Hindawi Publishing CorporationJournal of ChemistryVolume 2013 Article ID 258519 14 pageshttpdxdoiorg1011552013258519

Research ArticleMolecular Modeling and Spectroscopic Studies of Benzothiazole

V Sathyanarayanmoorthi1 R Karunathan1 and V Kannappan2

1 PG and Research Department of Physics PSG College of Arts and Science Coimbatore 641 014 India2 PG and Research Department of Chemistry Presidency College Chennai 600 005 India

Correspondence should be addressed to V Sathyanarayanmoorthi sathyanarayanamoorthiyahoocoin

Received 20 May 2013 Revised 23 July 2013 Accepted 26 July 2013

Academic Editor Cengiz Soykan

Copyright copy 2013 V Sathyanarayanmoorthi et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

The Fourier Transform (FT) infrared and FT-Raman spectra of benzothiazole (BT) have been recorded and analyzed The equi-libriumgeometry bonding features and harmonic vibrational frequencies have been investigated by ab initio and density functionaltheory (DFT)methodsThe assignments of the vibrational spectra have been carried outThe computed optimized geometric bondlengths and bond angles show good agreement with experimental data of the title compound The calculated HOMO and LUMOenergies indicate that charge transfer occurs within the molecule Stability of the molecule due to conjugative interactions arisingfrom charge delocalization has been analyzed using natural bond orbital (NBO) analysisThe results show that the electron density(ED) in the 120590lowast and 120587lowast antibonding orbital and second-order delocalization energies 119864(2) confirm the occurrence of intramolecularcharge transfer (ICT)The calculated results were applied to simulate infrared and Raman spectra BT which show good agreementwith recorded spectra

1 Introduction

Benzothiazole (BT) molecule contains a thiazole ring fusedwith benzene ring Thiazole ring is a five-member ringconsists of one nitrogen and one sulfur atom in the ring Ben-zothiazole is thus a bicyclic aromatic ring system A numberof BT derivatives have been studied as central muscle relax-ants and found to interfere with glutamate neurotransmis-sion in biochemical electrophysiological and behavioralexperiments [1] Substituted benzothiazoles have been stud-ied and found to have various chemical reactivity and biologi-cal activity Benzothiazole ring is found to possess pharmaco-logical activities such as antiviral [2] antibacterial [3] anti-microbial [4] and fungicidal activities [5] They are also use-ful as antiallergic [6] antidiabeticantitumor [7] antitumor[8] anti-inflammatory [9] anthelmintic [10] and anti-HIVagents Phenyl substituted benzothiazoles show antitumoractivity [11ndash13] while condensed pyrimido benzothiazolesand benzothiazoloquinazolines show antiviral activity Sub-stituted 6-nitro- and 6-amino-benzothiazoles show antimi-crobial activity

Molecular spectroscopic methods in particular experi-mental IR and Raman spectroscopy have been successfully

employed for structural investigation of complex molecularcompounds These techniques are especially effective whenused in combination with direct methods of structural ana-lysis in hydrogen bond investigations The aim of the presentwork is theoretical and experimental spectroscopic investiga-tion of BT molecular structure to gain insight into the struc-ture and physical properties of the molecular structure TheFT-IR and FT-Raman spectra were simulated and comparedwith experimental results Ab initio and DFT calculationshave been performed to support the wave number assign-ments

2 Methodology

21 Experimental Details The compound under investiga-tion namely BT is spectral grade purchased from MSAldrich Chemicals USA and it is used as such without fur-ther purification The FT-IR spectrum of the compound wasrecorded in Perkin-Elmer Spectrometer in the range of 4000ndash100 cmminus1 using KBr pellet technique The spectral resolutionis 01 cmminus1 The FT-Raman spectrum of the compound wasrecorded in the BRUKER RFS 27 and Standalone FT-Raman

2 Journal of Chemistry

Spectrometer in the frequency range 50ndash4000 cmminus1 TheLaser source is Nd YAG laser source operating at 1064 nmline with 200mW power The spectra were recorded withscanning speed of 20 cmminus1The frequencies of all sharp bandsare accurate to plusmn1 cmminus1

22 Computational Details The molecular geometry opti-mization and vibrational frequency calculations were carriedout on benzothiazole with GAUSSIAN 09W software pack-age [14] HF functional [15 16] combined with standard 6-311G and 6-311++G (d p) basis set (referred to as ldquolargerdquobasis) and the density functional method used is B3LYP thatis Beckersquos three-parameter hybrid functional with the Lee-Yang-Parr correlation functional method with 6-311++G (dp) The harmonic vibrational frequencies calculated for BTat HF and B3LYP levels using the triple split valence basisset along with the diffuse and polarization functions It maybe pointed out that computed wave number corresponds tothe isolated molecular state in the gaseous phase whereasthe experimental wave numbers correspond to the solid statespectra In order to evaluate the energetic behavior of thetitle compound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)and the lowest unoccupied MOs (LUMO) were calculatedusing HF6-311++G (d p) method NBO analysis has beenperformed on the BT molecule at the HF6-311++G (d p)and B3LYP6-311++G (d p) level in order to elucidate theintramolecular rehybridization and delocalization of elec-tron density within themoleculeThe result of interaction is aloss of occupancy from the density of electron in NBO of theidealized Lewis structure into an empty non-Lewis orbitalFor each donor (119894) and acceptor (119895) the stabilization energy119864(2) associated with the delocalization 119894 rarr 119895 is estimated as

119864 (2) = minus119899120590

⟨120590 |119865| 120590⟩2

120576lowast

120590minus 120576120590

= minus119899120590

119865119894119895

2

Δ119864

(1)

where ⟨120590|119865|120590⟩2 or 119865119894119895

2 is the Fock matrix element 119894 and 119895NBO orbitalrsquos 120576lowast

120590and minus120576

120590are the energies of 120590 and 120590lowast NBOs

and 119899120590is the population of the donor 120590 orbital Zero point

vibrational energy internal energy and its translational rota-tional and vibrational contributions entropy and heat capa-city of BT are computed through the calculation of partitionfunctions [17ndash19]

3 Results and Discussion

31 Molecular Geometry The optimized geometry of themolecule under investigation with IUPAC numberingscheme for the atoms is presented in Figure 1 The data ofstructural parameters obtained by ab initio method as com-pared to density functional theory for benzothiazole arereported in Table 1 The comparative graphs of bond lengthsand bond angles of the title molecule are presented in Figure2 From the computed values it is found thatmost of the opti-mized bond lengths are slightly larger than the experimentalvalues thismay be due to the fact that theoretical calculations

Figure 1 Optimized structure of benzothiazole

belong to isolated molecules in gaseous phase and theexperimental results belong to molecules in solid stateComparing bond angles and lengths obtained by B3LYPmethod with those obtained by HF as a whole the values gotby the former are higher than those obtained be the latermethod It may be pointed out that the values calculated byB3LYP method correlate satisfactorily with the experimentaldata From the data shown in Table 1 it is seen that both HFand DFT (B3LYP6-311++G (d p)) levels of theory in generalestimate the same values of some bond lengths and bondangles It is well known that HF methods underestimate andDFT method overestimates bond lengths particularly theCndashH bond lengths [20 21] This theoretical pattern is alsofound for benzothiazole molecule

The carbonndashcarbon bonds in benzene are not of equallengthwhich is justified by the presence of fused thiazole ringHowever the differences between the six CndashC distances aresmallThe longest bond distance in C4ndashC5 bond is due to thefusion of thiazole moiety at these carbons Comparing thebond distances of the hetero aromatic ring it is found thatthe bond distances in hetero aromatic ring differ significantlyfrom each other due to the difference in electronegativitiesof the bonded atoms The S1ndashC2 bond distance is the longest(17651 A) while the C2ndashN3 is the shortest (12874 A) Thelongest S1ndashC2 distance attributes the pure single bond char-acterThe C5ndashS1 and C2ndashS1 bond distances of BT determinedby B3LYP6-311++G (d p) method are 175 A and 17651 Arespectively in between the 181 A average distance for acarbonndashsulfur bond and the 161 A which indicate that theactual bond order is between one and two which is due toconjugative effect in benzothiazole Due to ring strain theC2ndashN3 double bond distance is 1268 A 1268 A 1263 A in HFand 12874 A for B3LYP6-311++G (d p) bigger than singlebondC2ndashH10With the electron donating substituents on thebenzene ring the symmetry of the ring is distorted yieldingring angles smaller than 120∘ at the point of substitution andslightly larger than 120∘ at the ortho- and metapositions [22]It is observed that in BT molecule the bond angle at thepoint of substitution C4ndashC5ndashC9 is 1187∘ in HF and 1189∘

Journal of Chemistry 3

10

11

12

13

14

15

16

17

18

19

HF6-311G

Valu

es (A

)

(S1

C2)

(S1

C5)

(C2

N3)

(C2

H10

)(N

3 C

4)(C

4 C

5)(C

4 C

6)(C

5 C

9)(C

6 C

7)(C

6 H

11)

(C7

C8)

(C7

H12

)(C

8 C

9)(C

8 H

13)

(C9

H14

)

B3LYP6-311++G (d p)HF6-311++G (d p)

mdash

(a)

HF6-311G

B3LYP6-311++G (d p)HF6-311++G (d p)

130

120

110

100

90

80

(C8

C9

H14

)(C

5 C

9 H

14)

(C5

C9

C8)

(C9

C8

H13

)(C

7 C

8 H

13)

(C7

C8

C9)

(C8

C7

H12

)(C

6 C

7 H

12)

(C6

C7

C8)

(C7

C6

H11

)(C

4 C

6 H

11)

(C4

C6

C7)

(C4

C5

C9)

(S1

C5

C9)

(S1

C5

C4)

(C5

C4

C6)

(N3

C4

C6)

(N3

C4

C5)

(C2

N3

C4)

(N3

C2

H10

)(C

1 C

2 H

10)

(C1

C2

N3)

(C2

C1

C5)

Valu

es (A

)

(b)

Figure 2 Bond length and bond angle difference between theoretical (HF and DFT) approaches

in DFT while the bond angles in at ortho to the substitutedcarbon C6ndashC7ndashC8 position is found to be 1208677 120908degree at HF and DFT respectively This may be due tomesomeric effect of the thiazole ringThemeta position angleC7ndashC8ndashC9 is greater than 120∘ and is found to be 12091∘121078∘ More distortion in bond parameters is observed inthe heteroring than in the benzene ringThe variation in bondangle depends on the electronegativity of the central atomthe presence of lone pair of electrons and the conjugationof the double bonds If the electro negativity of the centralatom is less the bond angle decreases Thus the bond angleC5ndashS1ndashC2 is very less (882122∘ 882011∘) than the bond angleC8ndashN3ndashC2 (110755∘ 110742∘) which is due to the fact thatelectronegativity of nitrogen is greater than sulfur

32 Vibrational Assignments The BT molecule consists of14 atoms and so it has 36 normal vibrational modes Theobserved vibrational assignments and analysis of BT are dis-cussed in terms of fundamental bands The harmonic vibra-tional frequencies calculated for BT at HF and B3LYP levelsalongwith the observed FT-IR and FT-Raman frequencies forvarious modes of vibrations have been presented in Table 2The comparative values of IR and Raman intensities are givenin Table 3 The recorded FT-IR and FT-Raman spectra of BTare given in in Figures 3(a) and 3(b) respectively TheoreticalFT-IR and FT-Raman spectra are reported in Figures 4 and 5respectively It may be pointed out here that computed wavenumbers correspond to the isolatedmolecular state in the gasphasewhereas the experimental wave numbers correspond tothe solid state spectra The calculated vibrational frequenciesusing different methods are compared with experimentallyobserved valuesThe calculated vibrational wave numbers are

consistent with the experimental results Few bands predictedtheoretically in FT-IR spectra were not observed in theexperimental spectrum of BT molecule may be due to theirvery weak intensity

321 CndashH Stretching Aromatic compounds commonlyexhibit multiple weak bands in the region 3100ndash3000 cmminus1[23ndash25] due to aromatic CndashH stretching vibrations In thepresent case the CndashH stretching vibrations are capturedat 3061 3150 cmminus1 in (mode no 32 33) FT-IR spectrumand corresponding Raman spectrum observed at 3063 cmminus1The aromatic CndashH in-plane bending modes of benzene andits derivatives are observed in the region 1300ndash1000 cmminus1The CndashH out-of-plane bending modes [26ndash29] are usuallyof medium intensity and absorption in the region 950ndash600 cmminus1 In the case of BT the bands observed at 1069 11241157 1198 and 1264 cmminus1 (mode no 17 19 20 21 and 22) in IRand at 1292 cmminus1 in Raman spectra are assigned to the CndashHin-plane bending vibrations The CndashH out of plane bendingmode of benzene derivatives is observed in the region 1000ndash600 cmminus1 The aromatic CndashH out of plane bending vibrationsof BT are assigned to the medium to weak bands observed at1014 and 978 cmminus1 (mode no 14 15) in the infrared spectrumand 1016 cmminus1 in Raman spectrum The aromatic CndashH in-plane and out of plane bending vibrations have substantialoverlapping with the ring CndashCndashC in-plane and out of planebending modes respectively

322 CndashS Stretching The CndashS and SndashH bonds are highlypolarizable and hence exhibit stronger spectral activity TheCndashS stretching vibration is expected in the region 710ndash685 cmminus1 [30] The CndashS stretching vibrations were observed

4 Journal of Chemistry

Table 1 Optimized some geometrical parameters of benzothiazole bond length (A) and bond angles (∘)

Parameters HF6-31G HF6-311G HF6-311++G B3LYP6-311GBond length

(S1 C2) 18159 18146 17464 17651(S1 C5) 18096 18043 17443 17518(C2 N3) 12688 12683 12638 12874(C2 H10) 10665 10647 10744 10827(N3 C4) 14031 1404 13886 13877(C4 C5) 13926 1391 13912 14139(C4 C6) 13887 13882 13932 14008(C5 C9) 1385 13844 13907 13962(C6 C7) 13811 13803 13761 13866(C6 H11) 10713 10689 10743 10832(C7 C8) 13975 13976 13994 1405(C7 H12) 10723 107 1075 10838(C8 C9) 13843 1383 13774 13893(C8 H13) 10726 10703 10751 10839(C9 H14) 10715 10694 10746 10832

Bond angle(C2 C1 C5) 867846 868578 882122 882011(C1 C2 N3) 115703 1156631 1169227 1166919(C1 C2 H10) 119792 1197907 1197167 1193151(N3 C2 H10) 1245047 1245462 1233605 123993(C2 N3 C4) 1129102 1128215 110755 110742(N3 C4 C5) 115155 1151091 1151782 1152284(N3 C4 C6) 1245797 1245766 124855 1251777(C5 C4 C6) 1202653 1203142 1199668 1195939(S1 C5 C4) 1094469 1095485 1089318 1091366(S1 C5 C9) 1291903 1291251 1296054 1294096(C4 C5 C9) 1213628 1213263 1214628 1214538(C4 C6 C7) 1187264 1187178 1187551 1189556(C4 C6 H11) 1193604 1192699 1195996 119307(C7 C6 H11) 1219132 1220123 1216452 1217374(C6 C7 C8) 1206426 1206135 1208677 120908(C6 C7 H12) 1198217 1198388 1197498 1196972(C8 C7 H12) 1195357 1195477 1193825 1193948(C7 C8 C9) 1209529 1209354 1209119 1210788(C7 C8 H13) 1195983 1196269 1195658 1195843(C9 C8 H13) 1194487 1194377 1195223 1193369(C5 C9 C8) 1180499 1180927 1180357 1180099(C5 C9 H14) 1211939 1211702 121132 1212411(C8 C9 H14) 1207561 1207371 1208323 120749

in the region 609ndash716 cmminus1 for 2-mercapto benzothiazole[31] The calculated values of the vibrations range from572 cmminus1 to 876 cmminus1 For 2-mercaptobenzoxazole [32] thecalculated values of the vibrations range from 579 cmminus1to 892 cmminus1 and the observed CndashS stretching vibrationis 954 cmminus1 In our title molecule the CndashS stretching isobserved at 667 and 799 cmminus1 (mode no 9 11) in FT-IR TheFT-Raman spectrum value at 801 cmminus1 as a medium bandis assigned to CndashS stretching vibration The calculated fre-quencies of 668 652 600 and 626 cmminus1 exactly correlate with

experimental observation as well as the literature data TheCndashS vibration is a pure mode as evident from Table 2The in-plane and out-of-plane CndashS stretching vibration also exactlycorrelates with experimental observations

323 C=N Vibrations The C=N stretching vibrations [33ndash36] are observed in the range 1672ndash1566 cmminus1 Varsanyi[37] has suggested that an IR band at 1626 cmminus1 for C=Nstretching and Raman frequency is assigned to the C=Nstretching vibration of benzothizaole [38] The respective

Journal of Chemistry 5

Table 2 Comparison of the experimental (FT-IR and FT-Raman) and theoretical harmonicwave numbers (cmminus1) of benzothiazole calculatedby HF B3LYP with 6-311++G(d p) basis set

Modes no Experimental 6-311G 6-311++G B3LYP6-311++G Assignment

IR Raman1 7144 1856993 2218993 1582282 CndashHmdashout of plane bending2 21004 2441506 2596877 2250702 CndashHmdashout of plane bending3 35291 3726441 3735584 3410859 Ring stretching4 42417 4262948 4141324 3500611 NndashCHWagging5 4717758 4672944 4293019 CndashSndashC in plane bending6 531 50508 5208227 5070766 4518357 CndashCndashCmdashout of plane bending7 585 5410727 5322922 4813446 CndashCndashCmdashout of plane bending8 6236493 6087293 5606751 CndashCndashCmdashout of plane bending9 667 6682929 6524117 6004245 CndashS Stretching10 769 70688 7303856 7176507 6667194 CndashCndashC Ring breathing11 799 80101 7778919 759172 7090033 CndashS Stretching12 828 8464841 8251871 7543702 Thiazole Ring Stretching13 873 8773007 8720681 8043435 CndashCndashCmdashin plane bending14 978 9742327 9298297 827145 CndashHmdashout of plane bending15 1014 101554 1025745 9702269 8752731 CndashHmdashout of plane bending16 10585012 10308954 9227485 CndashSmdashStretching17 1069 1085408 10534724 9853864 CndashHmdashin plane bending18 11102525 10695475 9934765 CndashHmdashin plane bending19 1124 112488 11248897 10964601 1015 CndashHmdashin plane bending20 1157 11660662 11251724 10279394 CndashHmdashin plane bending21 1198 119798 11940921 11544126 10924829 CndashHmdashin plane bending22 1264 12035496 11782819 11266974 CndashHmdashin plane bending23 1292 129166 12439149 12166827 11533509 CndashC Stretching24 1315 131601 13383513 13096226 12444551 CndashCmdashStretching25 1423 13942405 13642723 12687322 CndashCmdashStretching26 1454 142458 1427192 1397859 12757476 CndashCmdashStretching27 1490 146887 15753975 15565462 1440267 CndashH in plane bending28 1556 155701 15854282 15622713 14441304 CndashH in plane bending29 1592 16545209 16422366 15191381 C=N Stretching30 1657 16632985 16539474 15350676 CndashCndashC Stretching31 1692 17166492 17038545 16281791 C=N Stretching32 3061 306323 30701368 31057742 30286049 CndashH Stretching33 3150 30822096 3116571 3036013 CndashH Stretching34 30853847 31182409 30374297 CndashH Stretching35 30942296 31269054 30462331 CndashH Stretching36 31055365 31353642 30541799 CndashH Stretching

bands occurring at 1692 and 1592 cmminus1 (mode no 29 31) inIR spectra is assigned to the C=N stretching vibration for BTmolecule The bands corresponding to the CndashCndashC and CndashSndashC in-plane and out of plane bending modes of BT are pre-sented in Table 3 Normal coordinate analysis shows that sig-nificant mixing of CndashCndashC in-plane bending with CndashH in-plane bending occurs Similarly the skeletal out of planebending modes are overlapped with CndashH out of plane bend-ing modes significantlyThe theoretically calculated values of

C=N Stretching vibrations are in the region 1717 1704 and1629 cmminus1

324 Ring Vibrations The carbonndashcarbon stretching modesof the benzene ring are expected to be in the range from 1650to 1200 cmminus1 and are usually not very sensitive to substitutionby small substituents but heavy halogens diminish thefrequency [39 40] In theRaman spectrumof BT the carbonndashcarbon stretching bands appeared at 1596 1575 1478 and

6 Journal of Chemistry

Table 3 Comparative values of IR and Raman intensities between HF6-311G++(d p) and B3LYP6-311G++(d p) of benzothiazole

HF6-311G (d p) HF6-311++G (d p) B3LYP6-311++G (d p)IR intensity Raman intensity IR intensity Raman intensity IR intensity Raman intensity855 3144 769 1697 1275 3204087 1021 158 793 123 736111 1500 126 1427 119 13421498 2631 1753 2542 2289 2211114 2406 097 1681 1513 19921288 986 1117 772 1050 5311017 611 207 390 179 411663 363 586 362 673 243304 278 466 208 405 215484 527 506 514 506 2901616 809 1471 923 1848 11022038 669 2621 372 2366 1911424 381 1591 361 1031 3088808 038 7809 438 7812 0521160 1823 2484 1309 1720 4921248 488 1048 1079 223 1101542 225 1604 634 1029 935058 1192 573 250 1325 17501294 206 702 159 143 199315 157 443 134 170 225239 065 082 011 734 1881340 008 871 365 130 74841276 503 1628 962 845 182198 018 116 013 705 010007 250 102 227 1698 4843414 330 4098 372 768 0812704 098 1487 157 836 187666 087 2951 063 1958 0291029 944 1358 1394 966 1371635 327 827 284 099 1659869 945 11255 1948 10878 1177030 240 015 197 006 214794 626 421 560 437 10421326 1055 996 944 321 6442365 274 1421 244 1014 3242343 1530 1295 1386 955 1675

1209 cmminus1 The corresponding CndashC stretching modes areobserved in the infrared spectrum at 1454 1423 1315 and129231 cmminus1 (mode no 23 24 25 and 26) The theoreticallycalculated values are calculated at 1604 1602 1486 1454 1328and 1304 cmminus1 and these values show excellent agreementwith experimental data

The infrared band at 873 cmminus1 and two Raman bands at1000 and 700 cmminus1 (mode no 13) are assigned to CndashCndashC in-plane bending vibrations of BT The CndashC in-plane bendingvibrations appeared as the combination vibrations with CndashH in-plane bending vibrations The bands assigned to CndashCndashC out-of-plane bending vibrations are observed at 585531 cmminus1 in (mode no 6 7) FTIR spectrum and 505 cmminus1

in Raman spectrum for BT The ring breathing vibrationsare generally very strong in Raman spectrum This mode isfound in the region 1100minus1000 cmminus1 for a heavy substitutedcompound and is strongly Raman active This is confirmedby the very weak intense Raman band at 706 cmminus1 whichis supported by computed results The ring stretching modeis captured at 3726441 3735584 and 3410859 cmminus1 (modeno 3) in HF6-311++G (d p) and B3LYP6-311++G (d p)for benzothiazole molecule Comparison of IR intensitiesand Raman intensities calculated (Table 3) by HF and DFT(B3LYP) at 6-311+G (d p) level with experimental valuesexposes the variation of IR intensities and Raman intensitiesMost of the cases the values of IR intensities by HF are found

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CatalystsJournal of

2 Journal of Chemistry

Spectrometer in the frequency range 50ndash4000 cmminus1 TheLaser source is Nd YAG laser source operating at 1064 nmline with 200mW power The spectra were recorded withscanning speed of 20 cmminus1The frequencies of all sharp bandsare accurate to plusmn1 cmminus1

22 Computational Details The molecular geometry opti-mization and vibrational frequency calculations were carriedout on benzothiazole with GAUSSIAN 09W software pack-age [14] HF functional [15 16] combined with standard 6-311G and 6-311++G (d p) basis set (referred to as ldquolargerdquobasis) and the density functional method used is B3LYP thatis Beckersquos three-parameter hybrid functional with the Lee-Yang-Parr correlation functional method with 6-311++G (dp) The harmonic vibrational frequencies calculated for BTat HF and B3LYP levels using the triple split valence basisset along with the diffuse and polarization functions It maybe pointed out that computed wave number corresponds tothe isolated molecular state in the gaseous phase whereasthe experimental wave numbers correspond to the solid statespectra In order to evaluate the energetic behavior of thetitle compound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)and the lowest unoccupied MOs (LUMO) were calculatedusing HF6-311++G (d p) method NBO analysis has beenperformed on the BT molecule at the HF6-311++G (d p)and B3LYP6-311++G (d p) level in order to elucidate theintramolecular rehybridization and delocalization of elec-tron density within themoleculeThe result of interaction is aloss of occupancy from the density of electron in NBO of theidealized Lewis structure into an empty non-Lewis orbitalFor each donor (119894) and acceptor (119895) the stabilization energy119864(2) associated with the delocalization 119894 rarr 119895 is estimated as

119864 (2) = minus119899120590

⟨120590 |119865| 120590⟩2

120576lowast

120590minus 120576120590

= minus119899120590

119865119894119895

2

Δ119864

(1)

where ⟨120590|119865|120590⟩2 or 119865119894119895

2 is the Fock matrix element 119894 and 119895NBO orbitalrsquos 120576lowast

120590and minus120576

120590are the energies of 120590 and 120590lowast NBOs

and 119899120590is the population of the donor 120590 orbital Zero point

vibrational energy internal energy and its translational rota-tional and vibrational contributions entropy and heat capa-city of BT are computed through the calculation of partitionfunctions [17ndash19]

3 Results and Discussion

31 Molecular Geometry The optimized geometry of themolecule under investigation with IUPAC numberingscheme for the atoms is presented in Figure 1 The data ofstructural parameters obtained by ab initio method as com-pared to density functional theory for benzothiazole arereported in Table 1 The comparative graphs of bond lengthsand bond angles of the title molecule are presented in Figure2 From the computed values it is found thatmost of the opti-mized bond lengths are slightly larger than the experimentalvalues thismay be due to the fact that theoretical calculations

Figure 1 Optimized structure of benzothiazole

belong to isolated molecules in gaseous phase and theexperimental results belong to molecules in solid stateComparing bond angles and lengths obtained by B3LYPmethod with those obtained by HF as a whole the values gotby the former are higher than those obtained be the latermethod It may be pointed out that the values calculated byB3LYP method correlate satisfactorily with the experimentaldata From the data shown in Table 1 it is seen that both HFand DFT (B3LYP6-311++G (d p)) levels of theory in generalestimate the same values of some bond lengths and bondangles It is well known that HF methods underestimate andDFT method overestimates bond lengths particularly theCndashH bond lengths [20 21] This theoretical pattern is alsofound for benzothiazole molecule

The carbonndashcarbon bonds in benzene are not of equallengthwhich is justified by the presence of fused thiazole ringHowever the differences between the six CndashC distances aresmallThe longest bond distance in C4ndashC5 bond is due to thefusion of thiazole moiety at these carbons Comparing thebond distances of the hetero aromatic ring it is found thatthe bond distances in hetero aromatic ring differ significantlyfrom each other due to the difference in electronegativitiesof the bonded atoms The S1ndashC2 bond distance is the longest(17651 A) while the C2ndashN3 is the shortest (12874 A) Thelongest S1ndashC2 distance attributes the pure single bond char-acterThe C5ndashS1 and C2ndashS1 bond distances of BT determinedby B3LYP6-311++G (d p) method are 175 A and 17651 Arespectively in between the 181 A average distance for acarbonndashsulfur bond and the 161 A which indicate that theactual bond order is between one and two which is due toconjugative effect in benzothiazole Due to ring strain theC2ndashN3 double bond distance is 1268 A 1268 A 1263 A in HFand 12874 A for B3LYP6-311++G (d p) bigger than singlebondC2ndashH10With the electron donating substituents on thebenzene ring the symmetry of the ring is distorted yieldingring angles smaller than 120∘ at the point of substitution andslightly larger than 120∘ at the ortho- and metapositions [22]It is observed that in BT molecule the bond angle at thepoint of substitution C4ndashC5ndashC9 is 1187∘ in HF and 1189∘

Journal of Chemistry 3

10

11

12

13

14

15

16

17

18

19

HF6-311G

Valu

es (A

)

(S1

C2)

(S1

C5)

(C2

N3)

(C2

H10

)(N

3 C

4)(C

4 C

5)(C

4 C

6)(C

5 C

9)(C

6 C

7)(C

6 H

11)

(C7

C8)

(C7

H12

)(C

8 C

9)(C

8 H

13)

(C9

H14

)

B3LYP6-311++G (d p)HF6-311++G (d p)

mdash

(a)

HF6-311G

B3LYP6-311++G (d p)HF6-311++G (d p)

130

120

110

100

90

80

(C8

C9

H14

)(C

5 C

9 H

14)

(C5

C9

C8)

(C9

C8

H13

)(C

7 C

8 H

13)

(C7

C8

C9)

(C8

C7

H12

)(C

6 C

7 H

12)

(C6

C7

C8)

(C7

C6

H11

)(C

4 C

6 H

11)

(C4

C6

C7)

(C4

C5

C9)

(S1

C5

C9)

(S1

C5

C4)

(C5

C4

C6)

(N3

C4

C6)

(N3

C4

C5)

(C2

N3

C4)

(N3

C2

H10

)(C

1 C

2 H

10)

(C1

C2

N3)

(C2

C1

C5)

Valu

es (A

)

(b)

Figure 2 Bond length and bond angle difference between theoretical (HF and DFT) approaches

in DFT while the bond angles in at ortho to the substitutedcarbon C6ndashC7ndashC8 position is found to be 1208677 120908degree at HF and DFT respectively This may be due tomesomeric effect of the thiazole ringThemeta position angleC7ndashC8ndashC9 is greater than 120∘ and is found to be 12091∘121078∘ More distortion in bond parameters is observed inthe heteroring than in the benzene ringThe variation in bondangle depends on the electronegativity of the central atomthe presence of lone pair of electrons and the conjugationof the double bonds If the electro negativity of the centralatom is less the bond angle decreases Thus the bond angleC5ndashS1ndashC2 is very less (882122∘ 882011∘) than the bond angleC8ndashN3ndashC2 (110755∘ 110742∘) which is due to the fact thatelectronegativity of nitrogen is greater than sulfur

32 Vibrational Assignments The BT molecule consists of14 atoms and so it has 36 normal vibrational modes Theobserved vibrational assignments and analysis of BT are dis-cussed in terms of fundamental bands The harmonic vibra-tional frequencies calculated for BT at HF and B3LYP levelsalongwith the observed FT-IR and FT-Raman frequencies forvarious modes of vibrations have been presented in Table 2The comparative values of IR and Raman intensities are givenin Table 3 The recorded FT-IR and FT-Raman spectra of BTare given in in Figures 3(a) and 3(b) respectively TheoreticalFT-IR and FT-Raman spectra are reported in Figures 4 and 5respectively It may be pointed out here that computed wavenumbers correspond to the isolatedmolecular state in the gasphasewhereas the experimental wave numbers correspond tothe solid state spectra The calculated vibrational frequenciesusing different methods are compared with experimentallyobserved valuesThe calculated vibrational wave numbers are

consistent with the experimental results Few bands predictedtheoretically in FT-IR spectra were not observed in theexperimental spectrum of BT molecule may be due to theirvery weak intensity

321 CndashH Stretching Aromatic compounds commonlyexhibit multiple weak bands in the region 3100ndash3000 cmminus1[23ndash25] due to aromatic CndashH stretching vibrations In thepresent case the CndashH stretching vibrations are capturedat 3061 3150 cmminus1 in (mode no 32 33) FT-IR spectrumand corresponding Raman spectrum observed at 3063 cmminus1The aromatic CndashH in-plane bending modes of benzene andits derivatives are observed in the region 1300ndash1000 cmminus1The CndashH out-of-plane bending modes [26ndash29] are usuallyof medium intensity and absorption in the region 950ndash600 cmminus1 In the case of BT the bands observed at 1069 11241157 1198 and 1264 cmminus1 (mode no 17 19 20 21 and 22) in IRand at 1292 cmminus1 in Raman spectra are assigned to the CndashHin-plane bending vibrations The CndashH out of plane bendingmode of benzene derivatives is observed in the region 1000ndash600 cmminus1 The aromatic CndashH out of plane bending vibrationsof BT are assigned to the medium to weak bands observed at1014 and 978 cmminus1 (mode no 14 15) in the infrared spectrumand 1016 cmminus1 in Raman spectrum The aromatic CndashH in-plane and out of plane bending vibrations have substantialoverlapping with the ring CndashCndashC in-plane and out of planebending modes respectively

322 CndashS Stretching The CndashS and SndashH bonds are highlypolarizable and hence exhibit stronger spectral activity TheCndashS stretching vibration is expected in the region 710ndash685 cmminus1 [30] The CndashS stretching vibrations were observed

4 Journal of Chemistry

Table 1 Optimized some geometrical parameters of benzothiazole bond length (A) and bond angles (∘)

Parameters HF6-31G HF6-311G HF6-311++G B3LYP6-311GBond length

(S1 C2) 18159 18146 17464 17651(S1 C5) 18096 18043 17443 17518(C2 N3) 12688 12683 12638 12874(C2 H10) 10665 10647 10744 10827(N3 C4) 14031 1404 13886 13877(C4 C5) 13926 1391 13912 14139(C4 C6) 13887 13882 13932 14008(C5 C9) 1385 13844 13907 13962(C6 C7) 13811 13803 13761 13866(C6 H11) 10713 10689 10743 10832(C7 C8) 13975 13976 13994 1405(C7 H12) 10723 107 1075 10838(C8 C9) 13843 1383 13774 13893(C8 H13) 10726 10703 10751 10839(C9 H14) 10715 10694 10746 10832

Bond angle(C2 C1 C5) 867846 868578 882122 882011(C1 C2 N3) 115703 1156631 1169227 1166919(C1 C2 H10) 119792 1197907 1197167 1193151(N3 C2 H10) 1245047 1245462 1233605 123993(C2 N3 C4) 1129102 1128215 110755 110742(N3 C4 C5) 115155 1151091 1151782 1152284(N3 C4 C6) 1245797 1245766 124855 1251777(C5 C4 C6) 1202653 1203142 1199668 1195939(S1 C5 C4) 1094469 1095485 1089318 1091366(S1 C5 C9) 1291903 1291251 1296054 1294096(C4 C5 C9) 1213628 1213263 1214628 1214538(C4 C6 C7) 1187264 1187178 1187551 1189556(C4 C6 H11) 1193604 1192699 1195996 119307(C7 C6 H11) 1219132 1220123 1216452 1217374(C6 C7 C8) 1206426 1206135 1208677 120908(C6 C7 H12) 1198217 1198388 1197498 1196972(C8 C7 H12) 1195357 1195477 1193825 1193948(C7 C8 C9) 1209529 1209354 1209119 1210788(C7 C8 H13) 1195983 1196269 1195658 1195843(C9 C8 H13) 1194487 1194377 1195223 1193369(C5 C9 C8) 1180499 1180927 1180357 1180099(C5 C9 H14) 1211939 1211702 121132 1212411(C8 C9 H14) 1207561 1207371 1208323 120749

in the region 609ndash716 cmminus1 for 2-mercapto benzothiazole[31] The calculated values of the vibrations range from572 cmminus1 to 876 cmminus1 For 2-mercaptobenzoxazole [32] thecalculated values of the vibrations range from 579 cmminus1to 892 cmminus1 and the observed CndashS stretching vibrationis 954 cmminus1 In our title molecule the CndashS stretching isobserved at 667 and 799 cmminus1 (mode no 9 11) in FT-IR TheFT-Raman spectrum value at 801 cmminus1 as a medium bandis assigned to CndashS stretching vibration The calculated fre-quencies of 668 652 600 and 626 cmminus1 exactly correlate with

experimental observation as well as the literature data TheCndashS vibration is a pure mode as evident from Table 2The in-plane and out-of-plane CndashS stretching vibration also exactlycorrelates with experimental observations

323 C=N Vibrations The C=N stretching vibrations [33ndash36] are observed in the range 1672ndash1566 cmminus1 Varsanyi[37] has suggested that an IR band at 1626 cmminus1 for C=Nstretching and Raman frequency is assigned to the C=Nstretching vibration of benzothizaole [38] The respective

Journal of Chemistry 5

Table 2 Comparison of the experimental (FT-IR and FT-Raman) and theoretical harmonicwave numbers (cmminus1) of benzothiazole calculatedby HF B3LYP with 6-311++G(d p) basis set

Modes no Experimental 6-311G 6-311++G B3LYP6-311++G Assignment

IR Raman1 7144 1856993 2218993 1582282 CndashHmdashout of plane bending2 21004 2441506 2596877 2250702 CndashHmdashout of plane bending3 35291 3726441 3735584 3410859 Ring stretching4 42417 4262948 4141324 3500611 NndashCHWagging5 4717758 4672944 4293019 CndashSndashC in plane bending6 531 50508 5208227 5070766 4518357 CndashCndashCmdashout of plane bending7 585 5410727 5322922 4813446 CndashCndashCmdashout of plane bending8 6236493 6087293 5606751 CndashCndashCmdashout of plane bending9 667 6682929 6524117 6004245 CndashS Stretching10 769 70688 7303856 7176507 6667194 CndashCndashC Ring breathing11 799 80101 7778919 759172 7090033 CndashS Stretching12 828 8464841 8251871 7543702 Thiazole Ring Stretching13 873 8773007 8720681 8043435 CndashCndashCmdashin plane bending14 978 9742327 9298297 827145 CndashHmdashout of plane bending15 1014 101554 1025745 9702269 8752731 CndashHmdashout of plane bending16 10585012 10308954 9227485 CndashSmdashStretching17 1069 1085408 10534724 9853864 CndashHmdashin plane bending18 11102525 10695475 9934765 CndashHmdashin plane bending19 1124 112488 11248897 10964601 1015 CndashHmdashin plane bending20 1157 11660662 11251724 10279394 CndashHmdashin plane bending21 1198 119798 11940921 11544126 10924829 CndashHmdashin plane bending22 1264 12035496 11782819 11266974 CndashHmdashin plane bending23 1292 129166 12439149 12166827 11533509 CndashC Stretching24 1315 131601 13383513 13096226 12444551 CndashCmdashStretching25 1423 13942405 13642723 12687322 CndashCmdashStretching26 1454 142458 1427192 1397859 12757476 CndashCmdashStretching27 1490 146887 15753975 15565462 1440267 CndashH in plane bending28 1556 155701 15854282 15622713 14441304 CndashH in plane bending29 1592 16545209 16422366 15191381 C=N Stretching30 1657 16632985 16539474 15350676 CndashCndashC Stretching31 1692 17166492 17038545 16281791 C=N Stretching32 3061 306323 30701368 31057742 30286049 CndashH Stretching33 3150 30822096 3116571 3036013 CndashH Stretching34 30853847 31182409 30374297 CndashH Stretching35 30942296 31269054 30462331 CndashH Stretching36 31055365 31353642 30541799 CndashH Stretching

bands occurring at 1692 and 1592 cmminus1 (mode no 29 31) inIR spectra is assigned to the C=N stretching vibration for BTmolecule The bands corresponding to the CndashCndashC and CndashSndashC in-plane and out of plane bending modes of BT are pre-sented in Table 3 Normal coordinate analysis shows that sig-nificant mixing of CndashCndashC in-plane bending with CndashH in-plane bending occurs Similarly the skeletal out of planebending modes are overlapped with CndashH out of plane bend-ing modes significantlyThe theoretically calculated values of

C=N Stretching vibrations are in the region 1717 1704 and1629 cmminus1

324 Ring Vibrations The carbonndashcarbon stretching modesof the benzene ring are expected to be in the range from 1650to 1200 cmminus1 and are usually not very sensitive to substitutionby small substituents but heavy halogens diminish thefrequency [39 40] In theRaman spectrumof BT the carbonndashcarbon stretching bands appeared at 1596 1575 1478 and

6 Journal of Chemistry

Table 3 Comparative values of IR and Raman intensities between HF6-311G++(d p) and B3LYP6-311G++(d p) of benzothiazole

HF6-311G (d p) HF6-311++G (d p) B3LYP6-311++G (d p)IR intensity Raman intensity IR intensity Raman intensity IR intensity Raman intensity855 3144 769 1697 1275 3204087 1021 158 793 123 736111 1500 126 1427 119 13421498 2631 1753 2542 2289 2211114 2406 097 1681 1513 19921288 986 1117 772 1050 5311017 611 207 390 179 411663 363 586 362 673 243304 278 466 208 405 215484 527 506 514 506 2901616 809 1471 923 1848 11022038 669 2621 372 2366 1911424 381 1591 361 1031 3088808 038 7809 438 7812 0521160 1823 2484 1309 1720 4921248 488 1048 1079 223 1101542 225 1604 634 1029 935058 1192 573 250 1325 17501294 206 702 159 143 199315 157 443 134 170 225239 065 082 011 734 1881340 008 871 365 130 74841276 503 1628 962 845 182198 018 116 013 705 010007 250 102 227 1698 4843414 330 4098 372 768 0812704 098 1487 157 836 187666 087 2951 063 1958 0291029 944 1358 1394 966 1371635 327 827 284 099 1659869 945 11255 1948 10878 1177030 240 015 197 006 214794 626 421 560 437 10421326 1055 996 944 321 6442365 274 1421 244 1014 3242343 1530 1295 1386 955 1675

1209 cmminus1 The corresponding CndashC stretching modes areobserved in the infrared spectrum at 1454 1423 1315 and129231 cmminus1 (mode no 23 24 25 and 26) The theoreticallycalculated values are calculated at 1604 1602 1486 1454 1328and 1304 cmminus1 and these values show excellent agreementwith experimental data

The infrared band at 873 cmminus1 and two Raman bands at1000 and 700 cmminus1 (mode no 13) are assigned to CndashCndashC in-plane bending vibrations of BT The CndashC in-plane bendingvibrations appeared as the combination vibrations with CndashH in-plane bending vibrations The bands assigned to CndashCndashC out-of-plane bending vibrations are observed at 585531 cmminus1 in (mode no 6 7) FTIR spectrum and 505 cmminus1

in Raman spectrum for BT The ring breathing vibrationsare generally very strong in Raman spectrum This mode isfound in the region 1100minus1000 cmminus1 for a heavy substitutedcompound and is strongly Raman active This is confirmedby the very weak intense Raman band at 706 cmminus1 whichis supported by computed results The ring stretching modeis captured at 3726441 3735584 and 3410859 cmminus1 (modeno 3) in HF6-311++G (d p) and B3LYP6-311++G (d p)for benzothiazole molecule Comparison of IR intensitiesand Raman intensities calculated (Table 3) by HF and DFT(B3LYP) at 6-311+G (d p) level with experimental valuesexposes the variation of IR intensities and Raman intensitiesMost of the cases the values of IR intensities by HF are found

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Carbohydrate Chemistry

International Journal of

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Quantum Chemistry

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ElectrochemistryInternational Journal of

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CatalystsJournal of

Journal of Chemistry 3

10

11

12

13

14

15

16

17

18

19

HF6-311G

Valu

es (A

)

(S1

C2)

(S1

C5)

(C2

N3)

(C2

H10

)(N

3 C

4)(C

4 C

5)(C

4 C

6)(C

5 C

9)(C

6 C

7)(C

6 H

11)

(C7

C8)

(C7

H12

)(C

8 C

9)(C

8 H

13)

(C9

H14

)

B3LYP6-311++G (d p)HF6-311++G (d p)

mdash

(a)

HF6-311G

B3LYP6-311++G (d p)HF6-311++G (d p)

130

120

110

100

90

80

(C8

C9

H14

)(C

5 C

9 H

14)

(C5

C9

C8)

(C9

C8

H13

)(C

7 C

8 H

13)

(C7

C8

C9)

(C8

C7

H12

)(C

6 C

7 H

12)

(C6

C7

C8)

(C7

C6

H11

)(C

4 C

6 H

11)

(C4

C6

C7)

(C4

C5

C9)

(S1

C5

C9)

(S1

C5

C4)

(C5

C4

C6)

(N3

C4

C6)

(N3

C4

C5)

(C2

N3

C4)

(N3

C2

H10

)(C

1 C

2 H

10)

(C1

C2

N3)

(C2

C1

C5)

Valu

es (A

)

(b)

Figure 2 Bond length and bond angle difference between theoretical (HF and DFT) approaches

in DFT while the bond angles in at ortho to the substitutedcarbon C6ndashC7ndashC8 position is found to be 1208677 120908degree at HF and DFT respectively This may be due tomesomeric effect of the thiazole ringThemeta position angleC7ndashC8ndashC9 is greater than 120∘ and is found to be 12091∘121078∘ More distortion in bond parameters is observed inthe heteroring than in the benzene ringThe variation in bondangle depends on the electronegativity of the central atomthe presence of lone pair of electrons and the conjugationof the double bonds If the electro negativity of the centralatom is less the bond angle decreases Thus the bond angleC5ndashS1ndashC2 is very less (882122∘ 882011∘) than the bond angleC8ndashN3ndashC2 (110755∘ 110742∘) which is due to the fact thatelectronegativity of nitrogen is greater than sulfur

32 Vibrational Assignments The BT molecule consists of14 atoms and so it has 36 normal vibrational modes Theobserved vibrational assignments and analysis of BT are dis-cussed in terms of fundamental bands The harmonic vibra-tional frequencies calculated for BT at HF and B3LYP levelsalongwith the observed FT-IR and FT-Raman frequencies forvarious modes of vibrations have been presented in Table 2The comparative values of IR and Raman intensities are givenin Table 3 The recorded FT-IR and FT-Raman spectra of BTare given in in Figures 3(a) and 3(b) respectively TheoreticalFT-IR and FT-Raman spectra are reported in Figures 4 and 5respectively It may be pointed out here that computed wavenumbers correspond to the isolatedmolecular state in the gasphasewhereas the experimental wave numbers correspond tothe solid state spectra The calculated vibrational frequenciesusing different methods are compared with experimentallyobserved valuesThe calculated vibrational wave numbers are

consistent with the experimental results Few bands predictedtheoretically in FT-IR spectra were not observed in theexperimental spectrum of BT molecule may be due to theirvery weak intensity

321 CndashH Stretching Aromatic compounds commonlyexhibit multiple weak bands in the region 3100ndash3000 cmminus1[23ndash25] due to aromatic CndashH stretching vibrations In thepresent case the CndashH stretching vibrations are capturedat 3061 3150 cmminus1 in (mode no 32 33) FT-IR spectrumand corresponding Raman spectrum observed at 3063 cmminus1The aromatic CndashH in-plane bending modes of benzene andits derivatives are observed in the region 1300ndash1000 cmminus1The CndashH out-of-plane bending modes [26ndash29] are usuallyof medium intensity and absorption in the region 950ndash600 cmminus1 In the case of BT the bands observed at 1069 11241157 1198 and 1264 cmminus1 (mode no 17 19 20 21 and 22) in IRand at 1292 cmminus1 in Raman spectra are assigned to the CndashHin-plane bending vibrations The CndashH out of plane bendingmode of benzene derivatives is observed in the region 1000ndash600 cmminus1 The aromatic CndashH out of plane bending vibrationsof BT are assigned to the medium to weak bands observed at1014 and 978 cmminus1 (mode no 14 15) in the infrared spectrumand 1016 cmminus1 in Raman spectrum The aromatic CndashH in-plane and out of plane bending vibrations have substantialoverlapping with the ring CndashCndashC in-plane and out of planebending modes respectively

322 CndashS Stretching The CndashS and SndashH bonds are highlypolarizable and hence exhibit stronger spectral activity TheCndashS stretching vibration is expected in the region 710ndash685 cmminus1 [30] The CndashS stretching vibrations were observed

4 Journal of Chemistry

Table 1 Optimized some geometrical parameters of benzothiazole bond length (A) and bond angles (∘)

Parameters HF6-31G HF6-311G HF6-311++G B3LYP6-311GBond length

(S1 C2) 18159 18146 17464 17651(S1 C5) 18096 18043 17443 17518(C2 N3) 12688 12683 12638 12874(C2 H10) 10665 10647 10744 10827(N3 C4) 14031 1404 13886 13877(C4 C5) 13926 1391 13912 14139(C4 C6) 13887 13882 13932 14008(C5 C9) 1385 13844 13907 13962(C6 C7) 13811 13803 13761 13866(C6 H11) 10713 10689 10743 10832(C7 C8) 13975 13976 13994 1405(C7 H12) 10723 107 1075 10838(C8 C9) 13843 1383 13774 13893(C8 H13) 10726 10703 10751 10839(C9 H14) 10715 10694 10746 10832

Bond angle(C2 C1 C5) 867846 868578 882122 882011(C1 C2 N3) 115703 1156631 1169227 1166919(C1 C2 H10) 119792 1197907 1197167 1193151(N3 C2 H10) 1245047 1245462 1233605 123993(C2 N3 C4) 1129102 1128215 110755 110742(N3 C4 C5) 115155 1151091 1151782 1152284(N3 C4 C6) 1245797 1245766 124855 1251777(C5 C4 C6) 1202653 1203142 1199668 1195939(S1 C5 C4) 1094469 1095485 1089318 1091366(S1 C5 C9) 1291903 1291251 1296054 1294096(C4 C5 C9) 1213628 1213263 1214628 1214538(C4 C6 C7) 1187264 1187178 1187551 1189556(C4 C6 H11) 1193604 1192699 1195996 119307(C7 C6 H11) 1219132 1220123 1216452 1217374(C6 C7 C8) 1206426 1206135 1208677 120908(C6 C7 H12) 1198217 1198388 1197498 1196972(C8 C7 H12) 1195357 1195477 1193825 1193948(C7 C8 C9) 1209529 1209354 1209119 1210788(C7 C8 H13) 1195983 1196269 1195658 1195843(C9 C8 H13) 1194487 1194377 1195223 1193369(C5 C9 C8) 1180499 1180927 1180357 1180099(C5 C9 H14) 1211939 1211702 121132 1212411(C8 C9 H14) 1207561 1207371 1208323 120749

in the region 609ndash716 cmminus1 for 2-mercapto benzothiazole[31] The calculated values of the vibrations range from572 cmminus1 to 876 cmminus1 For 2-mercaptobenzoxazole [32] thecalculated values of the vibrations range from 579 cmminus1to 892 cmminus1 and the observed CndashS stretching vibrationis 954 cmminus1 In our title molecule the CndashS stretching isobserved at 667 and 799 cmminus1 (mode no 9 11) in FT-IR TheFT-Raman spectrum value at 801 cmminus1 as a medium bandis assigned to CndashS stretching vibration The calculated fre-quencies of 668 652 600 and 626 cmminus1 exactly correlate with

experimental observation as well as the literature data TheCndashS vibration is a pure mode as evident from Table 2The in-plane and out-of-plane CndashS stretching vibration also exactlycorrelates with experimental observations

323 C=N Vibrations The C=N stretching vibrations [33ndash36] are observed in the range 1672ndash1566 cmminus1 Varsanyi[37] has suggested that an IR band at 1626 cmminus1 for C=Nstretching and Raman frequency is assigned to the C=Nstretching vibration of benzothizaole [38] The respective

Journal of Chemistry 5

Table 2 Comparison of the experimental (FT-IR and FT-Raman) and theoretical harmonicwave numbers (cmminus1) of benzothiazole calculatedby HF B3LYP with 6-311++G(d p) basis set

Modes no Experimental 6-311G 6-311++G B3LYP6-311++G Assignment

IR Raman1 7144 1856993 2218993 1582282 CndashHmdashout of plane bending2 21004 2441506 2596877 2250702 CndashHmdashout of plane bending3 35291 3726441 3735584 3410859 Ring stretching4 42417 4262948 4141324 3500611 NndashCHWagging5 4717758 4672944 4293019 CndashSndashC in plane bending6 531 50508 5208227 5070766 4518357 CndashCndashCmdashout of plane bending7 585 5410727 5322922 4813446 CndashCndashCmdashout of plane bending8 6236493 6087293 5606751 CndashCndashCmdashout of plane bending9 667 6682929 6524117 6004245 CndashS Stretching10 769 70688 7303856 7176507 6667194 CndashCndashC Ring breathing11 799 80101 7778919 759172 7090033 CndashS Stretching12 828 8464841 8251871 7543702 Thiazole Ring Stretching13 873 8773007 8720681 8043435 CndashCndashCmdashin plane bending14 978 9742327 9298297 827145 CndashHmdashout of plane bending15 1014 101554 1025745 9702269 8752731 CndashHmdashout of plane bending16 10585012 10308954 9227485 CndashSmdashStretching17 1069 1085408 10534724 9853864 CndashHmdashin plane bending18 11102525 10695475 9934765 CndashHmdashin plane bending19 1124 112488 11248897 10964601 1015 CndashHmdashin plane bending20 1157 11660662 11251724 10279394 CndashHmdashin plane bending21 1198 119798 11940921 11544126 10924829 CndashHmdashin plane bending22 1264 12035496 11782819 11266974 CndashHmdashin plane bending23 1292 129166 12439149 12166827 11533509 CndashC Stretching24 1315 131601 13383513 13096226 12444551 CndashCmdashStretching25 1423 13942405 13642723 12687322 CndashCmdashStretching26 1454 142458 1427192 1397859 12757476 CndashCmdashStretching27 1490 146887 15753975 15565462 1440267 CndashH in plane bending28 1556 155701 15854282 15622713 14441304 CndashH in plane bending29 1592 16545209 16422366 15191381 C=N Stretching30 1657 16632985 16539474 15350676 CndashCndashC Stretching31 1692 17166492 17038545 16281791 C=N Stretching32 3061 306323 30701368 31057742 30286049 CndashH Stretching33 3150 30822096 3116571 3036013 CndashH Stretching34 30853847 31182409 30374297 CndashH Stretching35 30942296 31269054 30462331 CndashH Stretching36 31055365 31353642 30541799 CndashH Stretching

bands occurring at 1692 and 1592 cmminus1 (mode no 29 31) inIR spectra is assigned to the C=N stretching vibration for BTmolecule The bands corresponding to the CndashCndashC and CndashSndashC in-plane and out of plane bending modes of BT are pre-sented in Table 3 Normal coordinate analysis shows that sig-nificant mixing of CndashCndashC in-plane bending with CndashH in-plane bending occurs Similarly the skeletal out of planebending modes are overlapped with CndashH out of plane bend-ing modes significantlyThe theoretically calculated values of

C=N Stretching vibrations are in the region 1717 1704 and1629 cmminus1

324 Ring Vibrations The carbonndashcarbon stretching modesof the benzene ring are expected to be in the range from 1650to 1200 cmminus1 and are usually not very sensitive to substitutionby small substituents but heavy halogens diminish thefrequency [39 40] In theRaman spectrumof BT the carbonndashcarbon stretching bands appeared at 1596 1575 1478 and

6 Journal of Chemistry

Table 3 Comparative values of IR and Raman intensities between HF6-311G++(d p) and B3LYP6-311G++(d p) of benzothiazole

HF6-311G (d p) HF6-311++G (d p) B3LYP6-311++G (d p)IR intensity Raman intensity IR intensity Raman intensity IR intensity Raman intensity855 3144 769 1697 1275 3204087 1021 158 793 123 736111 1500 126 1427 119 13421498 2631 1753 2542 2289 2211114 2406 097 1681 1513 19921288 986 1117 772 1050 5311017 611 207 390 179 411663 363 586 362 673 243304 278 466 208 405 215484 527 506 514 506 2901616 809 1471 923 1848 11022038 669 2621 372 2366 1911424 381 1591 361 1031 3088808 038 7809 438 7812 0521160 1823 2484 1309 1720 4921248 488 1048 1079 223 1101542 225 1604 634 1029 935058 1192 573 250 1325 17501294 206 702 159 143 199315 157 443 134 170 225239 065 082 011 734 1881340 008 871 365 130 74841276 503 1628 962 845 182198 018 116 013 705 010007 250 102 227 1698 4843414 330 4098 372 768 0812704 098 1487 157 836 187666 087 2951 063 1958 0291029 944 1358 1394 966 1371635 327 827 284 099 1659869 945 11255 1948 10878 1177030 240 015 197 006 214794 626 421 560 437 10421326 1055 996 944 321 6442365 274 1421 244 1014 3242343 1530 1295 1386 955 1675

1209 cmminus1 The corresponding CndashC stretching modes areobserved in the infrared spectrum at 1454 1423 1315 and129231 cmminus1 (mode no 23 24 25 and 26) The theoreticallycalculated values are calculated at 1604 1602 1486 1454 1328and 1304 cmminus1 and these values show excellent agreementwith experimental data

The infrared band at 873 cmminus1 and two Raman bands at1000 and 700 cmminus1 (mode no 13) are assigned to CndashCndashC in-plane bending vibrations of BT The CndashC in-plane bendingvibrations appeared as the combination vibrations with CndashH in-plane bending vibrations The bands assigned to CndashCndashC out-of-plane bending vibrations are observed at 585531 cmminus1 in (mode no 6 7) FTIR spectrum and 505 cmminus1

in Raman spectrum for BT The ring breathing vibrationsare generally very strong in Raman spectrum This mode isfound in the region 1100minus1000 cmminus1 for a heavy substitutedcompound and is strongly Raman active This is confirmedby the very weak intense Raman band at 706 cmminus1 whichis supported by computed results The ring stretching modeis captured at 3726441 3735584 and 3410859 cmminus1 (modeno 3) in HF6-311++G (d p) and B3LYP6-311++G (d p)for benzothiazole molecule Comparison of IR intensitiesand Raman intensities calculated (Table 3) by HF and DFT(B3LYP) at 6-311+G (d p) level with experimental valuesexposes the variation of IR intensities and Raman intensitiesMost of the cases the values of IR intensities by HF are found

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

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Carbohydrate Chemistry

International Journal of

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Medicinal ChemistryInternational Journal of

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Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Analytical ChemistryInternational Journal of

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Quantum Chemistry

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Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

4 Journal of Chemistry

Table 1 Optimized some geometrical parameters of benzothiazole bond length (A) and bond angles (∘)

Parameters HF6-31G HF6-311G HF6-311++G B3LYP6-311GBond length

(S1 C2) 18159 18146 17464 17651(S1 C5) 18096 18043 17443 17518(C2 N3) 12688 12683 12638 12874(C2 H10) 10665 10647 10744 10827(N3 C4) 14031 1404 13886 13877(C4 C5) 13926 1391 13912 14139(C4 C6) 13887 13882 13932 14008(C5 C9) 1385 13844 13907 13962(C6 C7) 13811 13803 13761 13866(C6 H11) 10713 10689 10743 10832(C7 C8) 13975 13976 13994 1405(C7 H12) 10723 107 1075 10838(C8 C9) 13843 1383 13774 13893(C8 H13) 10726 10703 10751 10839(C9 H14) 10715 10694 10746 10832

Bond angle(C2 C1 C5) 867846 868578 882122 882011(C1 C2 N3) 115703 1156631 1169227 1166919(C1 C2 H10) 119792 1197907 1197167 1193151(N3 C2 H10) 1245047 1245462 1233605 123993(C2 N3 C4) 1129102 1128215 110755 110742(N3 C4 C5) 115155 1151091 1151782 1152284(N3 C4 C6) 1245797 1245766 124855 1251777(C5 C4 C6) 1202653 1203142 1199668 1195939(S1 C5 C4) 1094469 1095485 1089318 1091366(S1 C5 C9) 1291903 1291251 1296054 1294096(C4 C5 C9) 1213628 1213263 1214628 1214538(C4 C6 C7) 1187264 1187178 1187551 1189556(C4 C6 H11) 1193604 1192699 1195996 119307(C7 C6 H11) 1219132 1220123 1216452 1217374(C6 C7 C8) 1206426 1206135 1208677 120908(C6 C7 H12) 1198217 1198388 1197498 1196972(C8 C7 H12) 1195357 1195477 1193825 1193948(C7 C8 C9) 1209529 1209354 1209119 1210788(C7 C8 H13) 1195983 1196269 1195658 1195843(C9 C8 H13) 1194487 1194377 1195223 1193369(C5 C9 C8) 1180499 1180927 1180357 1180099(C5 C9 H14) 1211939 1211702 121132 1212411(C8 C9 H14) 1207561 1207371 1208323 120749

in the region 609ndash716 cmminus1 for 2-mercapto benzothiazole[31] The calculated values of the vibrations range from572 cmminus1 to 876 cmminus1 For 2-mercaptobenzoxazole [32] thecalculated values of the vibrations range from 579 cmminus1to 892 cmminus1 and the observed CndashS stretching vibrationis 954 cmminus1 In our title molecule the CndashS stretching isobserved at 667 and 799 cmminus1 (mode no 9 11) in FT-IR TheFT-Raman spectrum value at 801 cmminus1 as a medium bandis assigned to CndashS stretching vibration The calculated fre-quencies of 668 652 600 and 626 cmminus1 exactly correlate with

experimental observation as well as the literature data TheCndashS vibration is a pure mode as evident from Table 2The in-plane and out-of-plane CndashS stretching vibration also exactlycorrelates with experimental observations

323 C=N Vibrations The C=N stretching vibrations [33ndash36] are observed in the range 1672ndash1566 cmminus1 Varsanyi[37] has suggested that an IR band at 1626 cmminus1 for C=Nstretching and Raman frequency is assigned to the C=Nstretching vibration of benzothizaole [38] The respective

Journal of Chemistry 5

Table 2 Comparison of the experimental (FT-IR and FT-Raman) and theoretical harmonicwave numbers (cmminus1) of benzothiazole calculatedby HF B3LYP with 6-311++G(d p) basis set

Modes no Experimental 6-311G 6-311++G B3LYP6-311++G Assignment

IR Raman1 7144 1856993 2218993 1582282 CndashHmdashout of plane bending2 21004 2441506 2596877 2250702 CndashHmdashout of plane bending3 35291 3726441 3735584 3410859 Ring stretching4 42417 4262948 4141324 3500611 NndashCHWagging5 4717758 4672944 4293019 CndashSndashC in plane bending6 531 50508 5208227 5070766 4518357 CndashCndashCmdashout of plane bending7 585 5410727 5322922 4813446 CndashCndashCmdashout of plane bending8 6236493 6087293 5606751 CndashCndashCmdashout of plane bending9 667 6682929 6524117 6004245 CndashS Stretching10 769 70688 7303856 7176507 6667194 CndashCndashC Ring breathing11 799 80101 7778919 759172 7090033 CndashS Stretching12 828 8464841 8251871 7543702 Thiazole Ring Stretching13 873 8773007 8720681 8043435 CndashCndashCmdashin plane bending14 978 9742327 9298297 827145 CndashHmdashout of plane bending15 1014 101554 1025745 9702269 8752731 CndashHmdashout of plane bending16 10585012 10308954 9227485 CndashSmdashStretching17 1069 1085408 10534724 9853864 CndashHmdashin plane bending18 11102525 10695475 9934765 CndashHmdashin plane bending19 1124 112488 11248897 10964601 1015 CndashHmdashin plane bending20 1157 11660662 11251724 10279394 CndashHmdashin plane bending21 1198 119798 11940921 11544126 10924829 CndashHmdashin plane bending22 1264 12035496 11782819 11266974 CndashHmdashin plane bending23 1292 129166 12439149 12166827 11533509 CndashC Stretching24 1315 131601 13383513 13096226 12444551 CndashCmdashStretching25 1423 13942405 13642723 12687322 CndashCmdashStretching26 1454 142458 1427192 1397859 12757476 CndashCmdashStretching27 1490 146887 15753975 15565462 1440267 CndashH in plane bending28 1556 155701 15854282 15622713 14441304 CndashH in plane bending29 1592 16545209 16422366 15191381 C=N Stretching30 1657 16632985 16539474 15350676 CndashCndashC Stretching31 1692 17166492 17038545 16281791 C=N Stretching32 3061 306323 30701368 31057742 30286049 CndashH Stretching33 3150 30822096 3116571 3036013 CndashH Stretching34 30853847 31182409 30374297 CndashH Stretching35 30942296 31269054 30462331 CndashH Stretching36 31055365 31353642 30541799 CndashH Stretching

bands occurring at 1692 and 1592 cmminus1 (mode no 29 31) inIR spectra is assigned to the C=N stretching vibration for BTmolecule The bands corresponding to the CndashCndashC and CndashSndashC in-plane and out of plane bending modes of BT are pre-sented in Table 3 Normal coordinate analysis shows that sig-nificant mixing of CndashCndashC in-plane bending with CndashH in-plane bending occurs Similarly the skeletal out of planebending modes are overlapped with CndashH out of plane bend-ing modes significantlyThe theoretically calculated values of

C=N Stretching vibrations are in the region 1717 1704 and1629 cmminus1

324 Ring Vibrations The carbonndashcarbon stretching modesof the benzene ring are expected to be in the range from 1650to 1200 cmminus1 and are usually not very sensitive to substitutionby small substituents but heavy halogens diminish thefrequency [39 40] In theRaman spectrumof BT the carbonndashcarbon stretching bands appeared at 1596 1575 1478 and

6 Journal of Chemistry

Table 3 Comparative values of IR and Raman intensities between HF6-311G++(d p) and B3LYP6-311G++(d p) of benzothiazole

HF6-311G (d p) HF6-311++G (d p) B3LYP6-311++G (d p)IR intensity Raman intensity IR intensity Raman intensity IR intensity Raman intensity855 3144 769 1697 1275 3204087 1021 158 793 123 736111 1500 126 1427 119 13421498 2631 1753 2542 2289 2211114 2406 097 1681 1513 19921288 986 1117 772 1050 5311017 611 207 390 179 411663 363 586 362 673 243304 278 466 208 405 215484 527 506 514 506 2901616 809 1471 923 1848 11022038 669 2621 372 2366 1911424 381 1591 361 1031 3088808 038 7809 438 7812 0521160 1823 2484 1309 1720 4921248 488 1048 1079 223 1101542 225 1604 634 1029 935058 1192 573 250 1325 17501294 206 702 159 143 199315 157 443 134 170 225239 065 082 011 734 1881340 008 871 365 130 74841276 503 1628 962 845 182198 018 116 013 705 010007 250 102 227 1698 4843414 330 4098 372 768 0812704 098 1487 157 836 187666 087 2951 063 1958 0291029 944 1358 1394 966 1371635 327 827 284 099 1659869 945 11255 1948 10878 1177030 240 015 197 006 214794 626 421 560 437 10421326 1055 996 944 321 6442365 274 1421 244 1014 3242343 1530 1295 1386 955 1675

1209 cmminus1 The corresponding CndashC stretching modes areobserved in the infrared spectrum at 1454 1423 1315 and129231 cmminus1 (mode no 23 24 25 and 26) The theoreticallycalculated values are calculated at 1604 1602 1486 1454 1328and 1304 cmminus1 and these values show excellent agreementwith experimental data

The infrared band at 873 cmminus1 and two Raman bands at1000 and 700 cmminus1 (mode no 13) are assigned to CndashCndashC in-plane bending vibrations of BT The CndashC in-plane bendingvibrations appeared as the combination vibrations with CndashH in-plane bending vibrations The bands assigned to CndashCndashC out-of-plane bending vibrations are observed at 585531 cmminus1 in (mode no 6 7) FTIR spectrum and 505 cmminus1

in Raman spectrum for BT The ring breathing vibrationsare generally very strong in Raman spectrum This mode isfound in the region 1100minus1000 cmminus1 for a heavy substitutedcompound and is strongly Raman active This is confirmedby the very weak intense Raman band at 706 cmminus1 whichis supported by computed results The ring stretching modeis captured at 3726441 3735584 and 3410859 cmminus1 (modeno 3) in HF6-311++G (d p) and B3LYP6-311++G (d p)for benzothiazole molecule Comparison of IR intensitiesand Raman intensities calculated (Table 3) by HF and DFT(B3LYP) at 6-311+G (d p) level with experimental valuesexposes the variation of IR intensities and Raman intensitiesMost of the cases the values of IR intensities by HF are found

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

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CatalystsJournal of

Journal of Chemistry 5

Table 2 Comparison of the experimental (FT-IR and FT-Raman) and theoretical harmonicwave numbers (cmminus1) of benzothiazole calculatedby HF B3LYP with 6-311++G(d p) basis set

Modes no Experimental 6-311G 6-311++G B3LYP6-311++G Assignment

IR Raman1 7144 1856993 2218993 1582282 CndashHmdashout of plane bending2 21004 2441506 2596877 2250702 CndashHmdashout of plane bending3 35291 3726441 3735584 3410859 Ring stretching4 42417 4262948 4141324 3500611 NndashCHWagging5 4717758 4672944 4293019 CndashSndashC in plane bending6 531 50508 5208227 5070766 4518357 CndashCndashCmdashout of plane bending7 585 5410727 5322922 4813446 CndashCndashCmdashout of plane bending8 6236493 6087293 5606751 CndashCndashCmdashout of plane bending9 667 6682929 6524117 6004245 CndashS Stretching10 769 70688 7303856 7176507 6667194 CndashCndashC Ring breathing11 799 80101 7778919 759172 7090033 CndashS Stretching12 828 8464841 8251871 7543702 Thiazole Ring Stretching13 873 8773007 8720681 8043435 CndashCndashCmdashin plane bending14 978 9742327 9298297 827145 CndashHmdashout of plane bending15 1014 101554 1025745 9702269 8752731 CndashHmdashout of plane bending16 10585012 10308954 9227485 CndashSmdashStretching17 1069 1085408 10534724 9853864 CndashHmdashin plane bending18 11102525 10695475 9934765 CndashHmdashin plane bending19 1124 112488 11248897 10964601 1015 CndashHmdashin plane bending20 1157 11660662 11251724 10279394 CndashHmdashin plane bending21 1198 119798 11940921 11544126 10924829 CndashHmdashin plane bending22 1264 12035496 11782819 11266974 CndashHmdashin plane bending23 1292 129166 12439149 12166827 11533509 CndashC Stretching24 1315 131601 13383513 13096226 12444551 CndashCmdashStretching25 1423 13942405 13642723 12687322 CndashCmdashStretching26 1454 142458 1427192 1397859 12757476 CndashCmdashStretching27 1490 146887 15753975 15565462 1440267 CndashH in plane bending28 1556 155701 15854282 15622713 14441304 CndashH in plane bending29 1592 16545209 16422366 15191381 C=N Stretching30 1657 16632985 16539474 15350676 CndashCndashC Stretching31 1692 17166492 17038545 16281791 C=N Stretching32 3061 306323 30701368 31057742 30286049 CndashH Stretching33 3150 30822096 3116571 3036013 CndashH Stretching34 30853847 31182409 30374297 CndashH Stretching35 30942296 31269054 30462331 CndashH Stretching36 31055365 31353642 30541799 CndashH Stretching

bands occurring at 1692 and 1592 cmminus1 (mode no 29 31) inIR spectra is assigned to the C=N stretching vibration for BTmolecule The bands corresponding to the CndashCndashC and CndashSndashC in-plane and out of plane bending modes of BT are pre-sented in Table 3 Normal coordinate analysis shows that sig-nificant mixing of CndashCndashC in-plane bending with CndashH in-plane bending occurs Similarly the skeletal out of planebending modes are overlapped with CndashH out of plane bend-ing modes significantlyThe theoretically calculated values of

C=N Stretching vibrations are in the region 1717 1704 and1629 cmminus1

324 Ring Vibrations The carbonndashcarbon stretching modesof the benzene ring are expected to be in the range from 1650to 1200 cmminus1 and are usually not very sensitive to substitutionby small substituents but heavy halogens diminish thefrequency [39 40] In theRaman spectrumof BT the carbonndashcarbon stretching bands appeared at 1596 1575 1478 and

6 Journal of Chemistry

Table 3 Comparative values of IR and Raman intensities between HF6-311G++(d p) and B3LYP6-311G++(d p) of benzothiazole

HF6-311G (d p) HF6-311++G (d p) B3LYP6-311++G (d p)IR intensity Raman intensity IR intensity Raman intensity IR intensity Raman intensity855 3144 769 1697 1275 3204087 1021 158 793 123 736111 1500 126 1427 119 13421498 2631 1753 2542 2289 2211114 2406 097 1681 1513 19921288 986 1117 772 1050 5311017 611 207 390 179 411663 363 586 362 673 243304 278 466 208 405 215484 527 506 514 506 2901616 809 1471 923 1848 11022038 669 2621 372 2366 1911424 381 1591 361 1031 3088808 038 7809 438 7812 0521160 1823 2484 1309 1720 4921248 488 1048 1079 223 1101542 225 1604 634 1029 935058 1192 573 250 1325 17501294 206 702 159 143 199315 157 443 134 170 225239 065 082 011 734 1881340 008 871 365 130 74841276 503 1628 962 845 182198 018 116 013 705 010007 250 102 227 1698 4843414 330 4098 372 768 0812704 098 1487 157 836 187666 087 2951 063 1958 0291029 944 1358 1394 966 1371635 327 827 284 099 1659869 945 11255 1948 10878 1177030 240 015 197 006 214794 626 421 560 437 10421326 1055 996 944 321 6442365 274 1421 244 1014 3242343 1530 1295 1386 955 1675

1209 cmminus1 The corresponding CndashC stretching modes areobserved in the infrared spectrum at 1454 1423 1315 and129231 cmminus1 (mode no 23 24 25 and 26) The theoreticallycalculated values are calculated at 1604 1602 1486 1454 1328and 1304 cmminus1 and these values show excellent agreementwith experimental data

The infrared band at 873 cmminus1 and two Raman bands at1000 and 700 cmminus1 (mode no 13) are assigned to CndashCndashC in-plane bending vibrations of BT The CndashC in-plane bendingvibrations appeared as the combination vibrations with CndashH in-plane bending vibrations The bands assigned to CndashCndashC out-of-plane bending vibrations are observed at 585531 cmminus1 in (mode no 6 7) FTIR spectrum and 505 cmminus1

in Raman spectrum for BT The ring breathing vibrationsare generally very strong in Raman spectrum This mode isfound in the region 1100minus1000 cmminus1 for a heavy substitutedcompound and is strongly Raman active This is confirmedby the very weak intense Raman band at 706 cmminus1 whichis supported by computed results The ring stretching modeis captured at 3726441 3735584 and 3410859 cmminus1 (modeno 3) in HF6-311++G (d p) and B3LYP6-311++G (d p)for benzothiazole molecule Comparison of IR intensitiesand Raman intensities calculated (Table 3) by HF and DFT(B3LYP) at 6-311+G (d p) level with experimental valuesexposes the variation of IR intensities and Raman intensitiesMost of the cases the values of IR intensities by HF are found

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

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Carbohydrate Chemistry

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Analytical Methods in Chemistry

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CatalystsJournal of

6 Journal of Chemistry

Table 3 Comparative values of IR and Raman intensities between HF6-311G++(d p) and B3LYP6-311G++(d p) of benzothiazole

HF6-311G (d p) HF6-311++G (d p) B3LYP6-311++G (d p)IR intensity Raman intensity IR intensity Raman intensity IR intensity Raman intensity855 3144 769 1697 1275 3204087 1021 158 793 123 736111 1500 126 1427 119 13421498 2631 1753 2542 2289 2211114 2406 097 1681 1513 19921288 986 1117 772 1050 5311017 611 207 390 179 411663 363 586 362 673 243304 278 466 208 405 215484 527 506 514 506 2901616 809 1471 923 1848 11022038 669 2621 372 2366 1911424 381 1591 361 1031 3088808 038 7809 438 7812 0521160 1823 2484 1309 1720 4921248 488 1048 1079 223 1101542 225 1604 634 1029 935058 1192 573 250 1325 17501294 206 702 159 143 199315 157 443 134 170 225239 065 082 011 734 1881340 008 871 365 130 74841276 503 1628 962 845 182198 018 116 013 705 010007 250 102 227 1698 4843414 330 4098 372 768 0812704 098 1487 157 836 187666 087 2951 063 1958 0291029 944 1358 1394 966 1371635 327 827 284 099 1659869 945 11255 1948 10878 1177030 240 015 197 006 214794 626 421 560 437 10421326 1055 996 944 321 6442365 274 1421 244 1014 3242343 1530 1295 1386 955 1675

1209 cmminus1 The corresponding CndashC stretching modes areobserved in the infrared spectrum at 1454 1423 1315 and129231 cmminus1 (mode no 23 24 25 and 26) The theoreticallycalculated values are calculated at 1604 1602 1486 1454 1328and 1304 cmminus1 and these values show excellent agreementwith experimental data

The infrared band at 873 cmminus1 and two Raman bands at1000 and 700 cmminus1 (mode no 13) are assigned to CndashCndashC in-plane bending vibrations of BT The CndashC in-plane bendingvibrations appeared as the combination vibrations with CndashH in-plane bending vibrations The bands assigned to CndashCndashC out-of-plane bending vibrations are observed at 585531 cmminus1 in (mode no 6 7) FTIR spectrum and 505 cmminus1

in Raman spectrum for BT The ring breathing vibrationsare generally very strong in Raman spectrum This mode isfound in the region 1100minus1000 cmminus1 for a heavy substitutedcompound and is strongly Raman active This is confirmedby the very weak intense Raman band at 706 cmminus1 whichis supported by computed results The ring stretching modeis captured at 3726441 3735584 and 3410859 cmminus1 (modeno 3) in HF6-311++G (d p) and B3LYP6-311++G (d p)for benzothiazole molecule Comparison of IR intensitiesand Raman intensities calculated (Table 3) by HF and DFT(B3LYP) at 6-311+G (d p) level with experimental valuesexposes the variation of IR intensities and Raman intensitiesMost of the cases the values of IR intensities by HF are found

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Chemistry 7

(cmminus1)

T(

)

4000

0

3600

3200

2800

2400

2000

1800

1600

1400

1200

1000 80

0

600

450

0

00102030405060708090

999B-T

39353872

3434

3061

2992

29212873

27372630

2576

24852319

22801949

1913 1798

16921657

15921556

1510

1471

14551425

13151291

1267

1198

1157

1124

1069

1014

978

940

873

828

799 759729

706667

585531

(a)

Ram

an in

tens

ity

000

005

010

015

020

5000 4000 3000 2000 1000Wavenumber (cmminus1)

Bruker RFS 27

SAIF IITMCHENNAI

3063

23

1557

01

1468

87

1424

58

1316

03

1291

66

1197

98

1124

88

1015

54

801

0170

688 505

0742

417

352

9121

004

714

4

(b)

Figure 3 Experimental FT-IR and FT-Raman spectrum of benzothiazole

HF6-311G 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

Frequency (cmminus1)

(a)

140 130 120 110 100

90 80 70 60 50 40 30 20 10

0

HF6-311++G

30002500200015001000 500Frequency (cmminus1)

(b)

130 120 110 100

90 80 70 60 50 40 30 20 10

030002500200015001000 500

B3LYP-6-311++G

Frequency (cmminus1)

(c)

Figure 4 Theoretical FT-IR spectrum of benzothiazole

to be higher than B3LYP at 6-311+G (d p) level whereas in thecase of Raman activities the trend is reverse

33 NBOAnalysis Thenatural bond orbital analysis providesan efficient method for studying intra- and intermolecularbonding and interaction among bonds and also provides aconvenient basis for investigating charge transfer or conjuga-tive interaction in molecular systems Some electron donororbital acceptor orbital and the interacting stabilizationenergy resulting from the second-order microdisturbance

theory are reported [41] NBO analysis has been performedon the title molecule in order to elucidate the intermolecularrehybridization and delocalization of electron density withinthe molecule which are presented in Tables 4 and 5 A largediversity of energy values was found The stronger donorcharacter is shown by the p-type lone pair of the nitrogenatoms The most important interaction (119899 minus 120590lowast) energiesrelated to the resonance in the molecules are electrondonation from the LP(1)S atoms of the electron donatinggroups to the antibonding acceptor 120587lowast(CndashN) of the phenyl

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

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Carbohydrate Chemistry

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

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Chromatography Research International

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Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Theoretical ChemistryJournal of

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Analytical ChemistryInternational Journal of

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Quantum Chemistry

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Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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CatalystsJournal of

8 Journal of Chemistry

HF6-311G 600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500Frequency (cmminus1)

(a)

600 550 500 450 400 350 300 250 200 150 100

50 0

30002500200015001000 500

HF6-311++G

Frequency (cmminus1)

(b)

650 600 550 500 450 400 350 300 250 200 150 100

50 0

B3LYP-6-311++G

30002500200015001000 500Frequency (cmminus1)

(c)

Figure 5 Theoretical FT-Raman spectrum of benzothiazole

ring LP(1) S1 rarr 120590lowast (C2ndashN3) = 150 kJmolminus1 This largerenergy shows the hyperconjugation between the electron donating groups and the phenyl ring NBO analysis has beenperformed on the BT at the HF6-11++G (d p) and DFTlevel in order to elucidate the intramolecular rehybridizationand delocalization of electron density within the moleculeThe intramolecular interactions are formed by the orbitaloverlap between bonding (CndashC) and (CndashC) antibond orbitalwhich results in intramolecular charge transfer (ICT) causingstabilization of the systemThese interactions are observed asincrease in electron density (ED) in CndashC antibonding orbitalthat weakens the respective bondsThe strong intramolecularconjugative interaction of the 120590 electron of (S1ndashC2) distributeto 120590lowast (S1ndashC2) C4ndashC5 C4ndashC6 and C5ndashC9 of the ring On theother hand the 120587 (C2ndashN3) in the ring conjugate to the anti-bonding orbital of 120587lowast (C4ndashC6) leads to strong delocalizationof 1848 kJmol The 120587 (C4ndashC6) bond is interacting with 120587lowast(C2ndashN3) with the energy 1245 kcalmol for BT The 120590 (C4ndashC5) bond is interacting with 120590lowast (C2ndashH10) 120590lowast (C4ndashC6) 120590lowast(C5ndashC9) 120590lowast (C6ndashH11) 120590lowast (C9ndashH14) with the energies 068503 514 213 237 kcalmol for BTThe energy vlaues ofMOsof benzene ring 120590 (C4ndashC6 C6ndashC7 C7ndashC8 C8ndashC9) 120587 (C9ndashC5) are respectively 416 451 283 569 379 kcalmol for BT

34 Frontier Molecular Orbitals (FMOs) The highest occu-pied molecular orbitals (HOMOs) and the lowest-lyingunoccupied molecular orbitals (LUMOs) are called frontiermolecular orbitalrsquos (FMOs) The FMOs play an importantrole in the optical and electric properties as well as in

quantum chemistry and UV-vis spectra [37] The HOMOrepresents the ability to donate an electron LUMO as anelectron acceptor represents the ability to obtain an electronThe energy gap between HOMO and LUMO determines thekinetic stability chemical reactivity and optical polarizabilityand chemical hardness-softness of a molecule [42 43]

In order to evaluate the energetic behavior of the titlecompound we carried out calculations in vacuo and inorganic solvent (ethanol) The energies of important molec-ular orbitals of BT the highest occupied MOs (HOMO)the lowest unoccupied MOs (LUMO) were calculated usingHF6-311++G (d p) The energy values of HOMO andLUMO are minus02449 minus005227 respectively The 3D plotsof the HOMO LUMO orbitals computed for BT moleculeare illustrated in Figure 6 The positive phase is red andthe negative one is green It is evident from the figure thatwhile the HOMO is localized on almost the whole moleculeLUMO is localized on the thiazole ring Both the HOMOsand the LUMOs are mostly 120587 antibonding type orbitals Thecalculated energy value of HOMO is minus64099 eV and LUMOis minus2038 eV respectively The energy separation betweenthe HOMO and the LUMO is minus44061 eV respectively Theenergy gap of HOMO-LUMO explains the eventual chargetransfer interactionwithin themolecule which influences thebiological activity The wavelength of maximum absorptionexcitation energies 119864 (eV) and oscillator strengths (119891) ofbenzothiazole are calculated and given in Table 6 Figure 7contains theoretically deduced UV-vis spectrum of BT inethanol employing the TD-HF6-311++G (d p) method

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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Carbohydrate Chemistry

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Medicinal ChemistryInternational Journal of

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Chromatography Research International

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Organic Chemistry International

ElectrochemistryInternational Journal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Chemistry 9

Table 4 Second-order perturbation theory analysis of Fock matrix in NBO basis for benzothiazole

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)S1ndashC2 120590 197599 S1ndashC2 120590

lowast 007093 070 092 0023C4ndashC5 120590

lowast 003211 078 146 0030C4ndashC6 120590

lowast 002151 104 150 0035C5ndashC9 120590

lowast 002268 597 149 0084C5ndashC9 120587

lowast 035040 363 084 0054S1ndashC5 120590 197203 C2ndashN3 120587

lowast 007212 182 096 0038C2ndashH10 120590

lowast 002234 259 146 0055C5ndashC9 120590

lowast 002268 072 154 0030C8ndashC9 120590

lowast 001365 297 155 0061C2ndashN3 120590 199261 C2ndashH10 120590

lowast 002234 126 190 0044N3ndashC4 120590

lowast 002497 094 177 0037C4ndashC6 120590

lowast 002151 353 199 0075C4ndashC6 120587

lowast 034604 080 134 0032C2ndashN3 120587 195466 N3ndashC4 120590

lowast 002497 136 107 0034C4ndashC6 120587

lowast 034604 1848 064 0106C2ndashH10 120590 198286 C2ndashN3 120590

lowast 001757 183 160 0048N3ndashC4 120590

lowast 002497 801 133 0092N3ndashC4 120590 197560 S1ndashC2 120590

lowast 007093 112 115 0032C2ndashH10 120590

lowast 002234 702 164 0096C4ndashC5 120590

lowast 003211 054 169 0027C4ndashC6 120590

lowast 002151 123 173 0041C5ndashC9 120590

lowast 002268 269 173 0061C6ndashC7 120590

lowast 001185 180 174 0050C4ndashC5 120590 197874 C2ndashH10 120590

lowast 002234 068 165 0030C4ndashC6 120590

lowast 002151 503 174 0084C5ndashC9 120590

lowast 002268 514 174 0084C6ndashH11 120590

lowast 000915 213 166 0053C9ndashH14 120590

lowast 001004 237 166 0056C4ndashC6 120590 197510 S1ndashC5 120590

lowast 001756 416 122 0064C2ndashN3 120590

lowast 001757 150 176 0046C2ndashN3 120587

lowast 007212 053 112 0022N3ndashC4 120590

lowast 002497 134 150 0040C4ndashC5 120590

lowast 003211 554 168 0086C6ndashC7 120590

lowast 001185 272 172 0061C6ndashH11 120590

lowast 000915 169 164 0047C7ndashH12 120590

lowast 000908 225 164 0054C4ndashC6 120587 166368 C2ndashN3 120587

lowast 007212 1245 052 0077N3ndashC4 120590

lowast 002497 094 090 0028C5ndashC9 120587

lowast 035040 3919 046 0120C7ndashC8 120587

lowast 032093 3920 047 0122C5ndashC9 120590 198148 N3ndashC4 120590

lowast 002497 301 152 0060C4ndashC5 120590

lowast 003211 538 170 0086C8ndashC9 120590

lowast 001365 305 174 0065C8ndashH13 120590

lowast 000886 208 165 0052C9ndashH14 120590

lowast 001004 187 165 0050C5ndashC9 120587 170971 C2ndashN3 120587

lowast 007212 123 054 0024N3ndashC4 120590

lowast 002497 092 092 0028C4ndashC6 120587

lowast 034604 3607 048 0120C7ndashC8 120587

lowast 032093 3576 049 0120

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

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Analytical Methods in Chemistry

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Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

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Journal of

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Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

10 Journal of Chemistry

Table 4 Continued

Donor (119894) Type EDe Acceptor (119895) Type EDe E(2) E(119895) minus E(119894)b (a u) F (119894 119895)c (a u)C6ndashC7 120590 198054 N3ndashC4 120590

lowast 002497 451 149 007C4ndashC6 120590

lowast 002151 329 171 0067C6ndashH11 120590

lowast 000915 153 163 0045C7ndashC8 120590

lowast 001359 285 171 0062C7ndashH12 120590

lowast 000908 144 163 0043C8ndashH13 120590

lowast 000886 256 162 0058C6ndashH11 120590 198222 N3ndashC4 120590

lowast 002497 055 128 0024C4ndashC5 120590

lowast 003211 508 146 0077C4ndashC6 120590

lowast 002151 142 150 0041C6ndashC7 120590

lowast 001185 133 150 0040C7ndashC8 120590

lowast 001359 420 150 0071C7ndashC8 120590 198272 C6ndashC7 120590

lowast 001185 283 171 0062C6ndashH11 120590

lowast 000915 248 163 0057C7ndashH12 120590

lowast 000908 155 163 0045C8ndashC9 120590

lowast 001365 290 171 0063C8ndashH13 120590

lowast 000886 156 162 0045C9ndashH14 120590

lowast 001004 259 162 0058C7ndashC8 120587 167584 C4ndashC6 120587

lowast 034604 4289 046 0126C5ndashC9 120587

lowast 035040 4280 045 0125C7ndashH12 120590 198449 C4ndashC6 120590

lowast 002151 440 150 0073C6ndashC7 120590

lowast 001185 128 150 0039C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 420 150 0071C8ndashC9 120590 197778 S1ndashC5 120590

lowast 001756 569 121 0074C5ndashC9 120590

lowast 002268 397 170 0073C7ndashC8 120590

lowast 001359 283 171 0062C7ndashH12 120590

lowast 000908 251 163 0057C8ndashH13 120590

lowast 000886 143 163 0043C9ndashH14 120590

lowast 001004 153 162 0045C8ndashH13 120590 198412 C5ndashC9 120590

lowast 002268 470 149 0075C6ndashC7 120590

lowast 001185 416 150 0071C7ndashC8 120590

lowast 001359 129 150 0039C8ndashC9 120590

lowast 001365 126 150 0039C9ndashH14 120590 198424 C4ndashC5 120590

lowast 003211 444 146 0072C5ndashC9 120590

lowast 002268 154 149 0043C7ndashC8 120590

lowast 001359 407 150 0070C8ndashC9 120590

lowast 001365 133 150 0040C4ndashC6 120587

lowast 034604 C2ndashN3 120587lowast 007212 1862 005 0062

N3ndashC4 120590lowast 002497 279 043 0072

C5ndashC9 120587lowast 035040 C2ndashN3 120587

lowast 007212 379 006 0030C7ndashC8 120587

lowast 032093 37130 002 0122aE(2) means energy of hyperconjugative interaction (stabilization energy)bEnergy difference between donor and acceptor 119894 and 119895 NBO orbitalscF(119894 119895) is the Fock matrix element between 119894 and 119895 NBO orbitals

35 Thermodynamic Properties The values of thermody-namic parameters zero point vibrational energy thermalenergy specific heat capacity rotational constants entropy ofBT at 29815 K in ground state are listed in Table 7The varia-tion in zero point vibrational energies (ZPVEs) seems tobe significant The ZPVE is much lower by the DFTB3LYPmethod than by the HF method The high value of ZPVE of

BT is 6551 kclmol obtained at HF6-311++G (d p) whereasthe smallest values is 6163 kcalmol obtained at B3LYP6-311++G (d p) Dipole moment reflects the molecular chargedistribution and is given as a vector in three dimensionsTherefore it can be used as descriptor to depict the chargemovement across the molecule Direction of the dipolemoment vector in a molecule depends on the centers of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Chemistry 11

Table 5 Second-order perturbation energies 119864(2) (donor rarr acceptor) for benzothiazole

Donor (119894) Acceptor (119895) E(2) (kJ molminus1)a E(j) minus E(i)b (a u) F (i j)c (a u)Within unit 1

LP (1) S1 120590lowastC2ndashN3 150 170 0045

LP (1) S1 120587lowastC2ndashN3 138 105 0035

LP (1) S1 120590lowastC4ndashC5 177 161 0048

LP (1) S1 120590lowastC5ndashC9 052 164 0026

LP (2) S1 120587lowastC2ndashN3 898 059 0065

LP (2) S1 120590lowastC2ndashH10 141 109 0036

LP (2) S1 120590lowastC4ndashC5 121 114 0034

LP (2) S1 120590lowastC5ndashC9 198 118 0044

LP (1) N3 120590lowastC2ndashN6 264 117 0050

LP (1) N3 120590lowastC4ndashC5 923 138 0102

LP (1) N3 120590lowastC4ndashH7 347 125 0060

LP (1) N3 120590lowastS1ndashC2 2732 077 0130

LP (1) N3 120590lowastC4ndashC6 085 135 0031

LP (1) N3 120590lowastC4ndashC6 117 070 0027

aE(2) means energy of hyper conjugative interaction (stabilization energy)bEnergy difference between donor and acceptor i and j NBO orbitalscF (i j) is the Fock matrix element between i and j NBO orbitals

Table 6 Calculated absorption wavelength (nm) excitation energies E (eV) and oscillator strengths (119891) of benzothiazole

TD-HF6-311++G (d p) TD-HF6-311++G (d p)Ethanol Gas phase

120582 (mn) (119891) 119864 (eV) 120582 (mn) (119891) E (eV)3081 00333 40241 eV 30866 00265 40169 eV26501 00013 46784 eV 26795 0001 46272 eV25277 00025 49051 eV 25478 00018 48663 eV

Table 7 The calculated thermodynamical parameter of benzothiazole

Basis Set HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (d p)Zero point energy (KcalMol) 6693709 66140 6551671 6163Rotational constant 293435 293435 293435 293435Rotational temperature 014083 014083 014083 014083Energy (119864)

Translational 0889 0889 0889 0889Rotational 0889 0889 0889 0889Vibrational 68158 68168 67551 64058Total 70689 69988 69329 65836

Specific heat (119862V)Translational 2981 2981 2981 2981Rotational 2981 2981 2981 2981Vibrational 17963 17973 18512 15283Total 23627 23935 20895 21245

Entropy (119878)Translational 40613 40613 40613 40613Rotational 28903 28903 28903 28903Vibrational 10154 10167 10040 12445Total 79436 79683 79556 81961

Dipole moment 20974 20507 16331 14713

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

12 Journal of Chemistry

Table 8 Mulliken atomic charges of benzothiazole

Atoms HF6-31G HF6-311G HF6-311++G (d p) B3LYP6-311++G (dp)S1 0494254 0283343 minus0428958 minus0305656

C2 minus0223616 minus009723 minus01285 minus0174194

N3 minus043924 minus0377701 0038389 0055788C4 0177233 0264898 minus0932014 minus0938592

C5 minus0403325 minus0453121 1000645 0984567C6 minus0120432 minus009318 minus043895 minus0437759

C7 minus0221659 minus0167237 minus0377287 minus0307896

C8 minus0184873 minus0165775 minus0246147 minus0081338

C9 minus019687 minus0144593 0313292 0218011H10 0242781 0218665 0275732 0255925H11 0235255 0192916 0244504 0193902H12 0209181 0176608 0217394 0172514H13 0207899 0178898 0216713 0174776H14 0223413 018351 0245187 0189952

ELUMO = minus2038

ΔE = minus44061

EHOMO = minus64099

Figure 6 The molecular orbitals and energies for the HOMO andLUMO of the title compound

positive and negative charges Dipole moments are strictlydetermined for neutral molecules For charged systemsits value depends on the choice of origin and molecularorientation As a result of HF and DFT (B3LYP) calculationsthe highest dipole moment was observed for B3LYP6-311G++(dp) whereas the smallest one was observed forHF6-311++G (d p) in each molecule

On the basis of vibrational analysis the statically ther-modynamic functions heat capacity (C) entropy (S) andenthalpy changes (DH) for the title molecule were obtainedfrom the theoretical harmonic frequencies and listed in Table7 From the data in this table it can be observed that thesethermodynamic functions are increasing with temperatureranging from 100 to 600K due to the fact that the molecularvibrational intensities increase with temperature [44]

Wavelength (nm) 310 305 300 295 290 285 280 275 270 265 260 255

004 0036 0032 0028 0024

002 0016 0012 0008 0004

0252783 265026

308087

HF6-311++G (d p)

f

Figure 7 Theoretical UV-vis spectrum in ethanol for the titlemolecule calculated with the TD-HF6-311++G (d p) method

36 Mulliken Atomic Charges Mulliken atomic charge cal-culation is an important tool in the application of quantumchemical calculation to molecular system because atomiccharges influence dipole moment molecular polarizabil-ity electronic structure and other physical properties ofmolecular systems The calculated Mulliken charge valuesare listed in Table 8 The atomic charge depends on basisset presumably occur due to polarization For example thecharge of N (3) atom is minus043924 for HF6-31G minus0377701 forHF6-311G 0038389 for HF6-311++G (d p) and 0055788for B3LYP6-311++G (d p) The charge distribution of sulfurgroup is increasing trend in HF and B3LYP methods Thecharge of H10 H11 H12 H13 and H14 is positive in bothHF and DFT diffuse functions Considering all methods andbasis sets used in the atomic charge calculation the carbonatoms exhibit a substatantial negative charge which are donoratoms Hydrogen atom exhibits a positive charge which isan acceptor atom The Mulliken charge distribution of BTis increasing trend in B3LYP as compared to HF methodsA comparison of Mullikanrsquos Atomic charge obtained bythe two theoretical (HF and DFT) approaches is illustratedin Figure 8 It may be seen that the two methods givecomparable atomic charges

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Journal of Chemistry 13

S1 N3 C4 C5 C6 C7 C8 C9 H

10

H11

H12

H13

H14

00

05

10

Mul

liken

atom

ic ch

arge

s

minus10

minus05

HF6-311GHF6-311++G (d p)B3LYP6-311++G (d p)

C2

Figure 8 Mullikanrsquos atomic charges between theoretical (HF andDFT) approaches

4 Conclusion

In the present work we have performed the experimentaland theoretical vibrational analysis of a pharmaceuticallyimportant heterocyclic aromatic molecule benzothiazole forthe first time The optimized molecular geometry vibra-tional frequencies infrared activities and Raman scatteringactivities of the molecule in the ground state have beencalculated by using ab initio HF and DFT (B3LYP) methodswith 6ndash311++G (d p) basis set The vibrational frequencieswere calculated and scaled values are compared with therecorded FT-IR and FT-Raman spectra of the compoundThe observed and the calculated frequencies are found to bein good agreement Furthermore the thermodynamic andtotal dipole moment properties of the compound have beencalculated in order to get insight into molecular structureof the compound These computations are carried out withthe main aim that the results will be of assistance in thequest of the experimental and theoretical evidence for the titlemolecule in biological activity and coordination chemistry

References

[1] H M Bryson B Fulton and P Benfield ldquoRiluzole A reviewof its pharmacodynamic and pharmacokinetic properties andtherapeutic potential in amyotrophic lateral sclerosisrdquo Drugsvol 52 no 4 pp 549ndash563 1996

[2] S AkihamaM Okhude and AMiznoChemical Abstracts vol68 p 10369v 1968

[3] F Russo and M Santagati ldquoSynthesis and determination ofthe antibacterial activity of benzothiazole derivatives of 134thiadiazole and imidazo [21 b]134 thiadiazolerdquo Farmaco vol31 no 1 pp 41ndash48 1976 (Italian)

[4] K M Ghoneim S El-Basil A N Osman M M Said andS A Megahed ldquoSynthesis and antimicrobial investigation ofbenzothiazole derivativesrdquo Revue Roumaine de Chimie vol 36pp 1355ndash1361 1991

[5] S P Singh and S Seghal ldquoStudy of fungicidal activities of somebenzothiazolesrdquo Indian Journal of Chemistry B vol 27 p 9411988

[6] J H Musser R E Brown B Love et al ldquoSynthesis of 2-(23-dihydro-2-oxo-134-oxadiazol-5-yl) benzo heterocycles Anovel series of orally active antiallergic agentsrdquo Journal ofMedicinal Chemistry vol 27 pp 121ndash125 1984

[7] S R Pattan C Suresh V D Pujar V V K Reddy V P Rasaland B C Kotti ldquoSynthesis and antidiabetic activity of 2-amino[51015840(4-sulphonylbenzylidine)-24-thiazolidinedione]-7-chloro-6-fluorobenzothiazolerdquo Indian Journal of Chemistry B vol 44no 11 pp 2404ndash2408 2005

[8] M Yoshida I Hayakawa N Hyashi et al ldquoSynthesis and bio-logical evaluation of benzothiazole derivatives as potent antitu-mor agentsrdquo Bioorganic amp Medicinal Chemistry Letters vol 15pp 3328ndash3332 2005

[9] S N Sawhney R K Tomer O M Prakash I Prakashand S P Singh ldquoBenzothiazole derivatives Part XI-Synthesisand anti-inflammatory activity of some 2-(31015840-51015840-dimethyl-41015840-substituted-pyrazole-11015840-yl) benzothiazolesrdquo Indian Journal ofChemistry B vol 20 pp 314ndash316 1981

[10] H D Brown Chemical Abstracts vol 65 p 18593 1966[11] C O Leong M Gaskell G A Martin et al ldquoAntitumour

2-(4-aminophenyl)benzothiazoles generate DNA adducts insensitive tumour cells in vitro and in vivordquo British Journal ofCancer vol 88 pp 470ndash477 2003

[12] T D Bradshaw M C Bibby J A Double et al ldquoPreclinicalevaluation of amino acid prodrugs of novel antitumor 2-(4-amino-3-methylphenyl)benzothiazolesrdquo Molecular CancerTherapeutics vol 1 no 4 pp 239ndash246 2002

[13] I Hutchinson S A Jennings B R Vishnuvajjala A DWestwell and M F G Stevens ldquoAntitumor benzothiazoles16 Synthesis and pharmaceutical properties of antitumor 2-(4-aminophenyl)benzothiazole amino acid prodrugsrdquo Journal ofMedicinal Chemistry vol 45 no 3 pp 744ndash747 2002

[14] J Frisch G W Trucks H B Schlegel et al Gaussian 09 Pro-gram Revision C 01 Gaussian Inc Wallingford Conn USA2010

[15] A D Becke ldquoDensity-functional thermochemistry IIIThe roleof exact exchangerdquoThe Journal of Chemical Physics vol 98 no7 pp 5648ndash5652 1993

[16] G Rauhut and P Pulay ldquoTransferable scaling factors for densityfunctional derived vibrational force fieldsrdquo The Journal ofPhysical Chemistry vol 99 no 10 pp 3093ndash3100 1995

[17] S Srinivasan S Gunasekaran U Ponnambalam A Savar-ianandam S Gnanaprakasam and S Natarajan ldquoSpectro-scopic and thermodynamic analysis of enolic form of 3-oxo-L-gulofuranolactonerdquo Indian Journal of Pure and Applied Physicsvol 43 no 6 pp 459ndash462 2005

[18] G Socretes Infrared Characteristic Group Frequencies JohnWiley amp Sons New York NY USA 1st edition 1980

[19] D Alfe G A De Wijs G Kresse and M J Gillan ldquoRecentdevelopments in ab initio thermodynamicsrdquo International Jour-nal of Quantum Chemistry vol 77 no 5 pp 871ndash879 2000

[20] H M Badawi W Forner and Y S Oloriegbe ldquoTheoretical vib-rational spectra and potential scans for trichloromethylsulfonylisocyanaterdquo Journal of Molecular Structure vol 548 no 1ndash3 pp219ndash227 2001

[21] DMahadevan S Periandy and S Ramalingam ldquoFT-IR and FT-Raman vibrational assignments molecular geometry ab initio(HF) and DFT (B3LYP) calculations for 13-dichlorobenzenerdquoSpectrochimica Acta A vol 79 no 5 pp 962ndash969 2011

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

14 Journal of Chemistry

[22] M Batley R Bramley and K Robinson ldquoPhotophysics of thelowest triplet state in 2-benzoylpyridine crystals I Opticalspectrardquo Proceedings of the Royal Society A vol 369 pp 175ndash1851979

[23] Y Wang S Saebo and C U Pittman Jr ldquoThe structure ofaniline by ab initio studiesrdquo Journal of Molecular Structure vol281 no 2-3 pp 91ndash98 1993

[24] I Fleming Frontier Orbitals and Organic Chemical ReactionsJohn Wiley amp Sons London UK 1976

[25] A M Asiri M Karabacak M Kurt and K A Alamry ldquoSyn-thesismolecular conformation vibrational and electronic tran-sition isometric chemical shift polarizability and hyperpolar-izability analysis of 3-(4-methoxy-phenyl)-2-(4-nitro-phenyl)-acrylonitrile a combined experimental and theoretical analy-sisrdquo Spectrochim Acta A vol 82 pp 444ndash455 2011

[26] B Kosar and C Albayrak ldquoSpectroscopic investigations andquantum chemical computational study of (E)-4-methoxy-2-[(p-tolylimino)methyl]phenolrdquo Spectrochimica Acta A vol 78no 1 pp 160ndash167 2011

[27] A A El-Azhary ldquoADFT study of the geometries and vibrationalspectra of indene and some of its heterocyclic analogues benzo-furan benzoxazole bensothiophene benzothiazole indole andindazolerdquo Spectrochim Acta A vol 55 no 12 pp 2437ndash24461999

[28] YWang S Saebo andCU Pittman Jr ldquoThe structure of anilineby ab initio studiesrdquo Journal of Molecular Structure vol 281 no2-3 pp 91ndash98 1993

[29] A Altun K Golcuk andM Kumru ldquoStructure and vibrationalspectra of p-methylaniline Hartree-Fock MP2 and densityfunctional theory studiesrdquo Journal of Molecular Structure vol637 pp 155ndash169 2003

[30] J Coates Interpretation of Infrared Spectra A Practical Ap-proach John Wiley amp Sons Chichester UK 2000

[31] X Li Z Tang andX Zhang ldquoMolecular structure IR spectra of2-mercaptobenzothiazole and 2-mercaptobenzoxazole by den-sity functional theory and ab initio Hartree-Fock calculations rdquoSpectrochim Acta A vol 74 no 1 pp 168ndash173 2009

[32] I Yalcin E Sener T Ozden S Ozden and A Akin ldquoSyn-thesis andmicrobiological activity of 5-methyl-2-[p-substitutedphenyl]benzoxazolesrdquo European Journal of Medicinal Chem-istry vol 25 no 8 pp 705ndash708 1990

[33] R Saxena L D Kandpal andG NMathur ldquoSynthesis and cha-racterization of poly(benzobisthiazole)s derived from haloge-nated phthalic acid and isophthalic acidrdquo Journal of PolymerScience A vol 40 no 22 pp 3959ndash3966 2002

[34] R M Silverstein G C Bassler and T C Morril SpectrometricIdentification of Organic Compounds John Wiley amp SonsSingapore 5th edition 1991

[35] K Nakamoto Infrared and Raman Spectrum of Inorganic andCoordination Compounds John Wiley amp Sons NewYork NYUSA 5th edition 1997

[36] G Yang S I Matsuzono E Koyama H Tokuhisa and KHiratani ldquoA new synthetic route to benzoxazole polymer viatandem claisen rearrangementrdquoMacromolecules vol 34 no 19pp 6545ndash6547 2001

[37] G Varsanyi Assignments for Vibrational Spectra of Seven Hun-dred Benzene Derivatives vol 1 Adam Hilger London UK1974

[38] G Socrates Infrared Raman Characteristic Group FrequenciesmdashTables and Charts JohnWiley amp Sons New York NY USA 3rdedition 2001

[39] V Krishnakumar and R J Xavier ldquoNormal coordinate analysisof 2-mercapto and 46-dihydroxy-2-mercapto pyrimidinesrdquoIndian Journal of Pure and Applied Physics vol 41 pp 597ndash6012003

[40] J N Liu Z R Chen and S F Yuan ldquoStudy on the prediction ofvisible absorption maxima of azobenzene compoundsrdquo Journalof Zhejiang University Science B vol 6 pp 584ndash589 2005

[41] R Zhang B Dub G Sun and Y Sun ldquoExperimental andtheoretical studies on o- m- and p-chlorobenzylideneamino-antipyrinesrdquo Spectrochimica Acta A vol 75 pp 1115ndash1124 2010

[42] L J Bellamy The Infrared Spectra of Complex Molecules JohnWiley amp Sons NewYork NY USA 3rd edition 1975

[43] E Koglin E G Witte and R J Meier ldquoThe vibrational spectraof metabolites of methabenzthiazuron 2-amino-benzothiazoleand 2-(methylamino)benzothiazolerdquo Vibrational Spectroscopyvol 33 no 1-2 pp 49ndash61 2003

[44] C James A A Raj R Reghunathan I H Joe and V S Jayaku-mar ldquoStructural conformation and vibrational spectroscopicstudies of 26-bis(p-NN-dimethyl benzylidene) cyclohexanoneusing density functional theoryrdquo Journal of Raman Spectroscopyvol 37 no 12 pp 1381ndash1392 2006

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Applied ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Theoretical ChemistryJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Spectroscopy

Analytical ChemistryInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Quantum Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Organic Chemistry International

ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CatalystsJournal of