Spectroscopic (FT-IR, FT-Raman, UV vis), Fukui function ...joics.org/gallery/ics-1274.pdf · linear optical effect [4]. In the recent years, amino acid complexes have received much

Spectroscopic (FT-IR, FT-Raman, UV–vis), Fukui function,

NLO, NBO, NPA and Thermodynamic properties of L-

Alaninium oxalate by ab initio and DFT method.

G.Ramachandran*

*Department of Physics, P.U.M .School, Vasur-632514, Tamilnadu, India.

*corresponding author: [email protected] (Dr.G.Ramchandran)

ABSTRACT

The Fourier Transform Infrared and Raman spectra of the L-Alaninium oxalate have

been recorded and analyzed. The fundamental vibrational wave numbers intensities of

vibrational bands and optimized geometrical parameters of the compound were evaluated using

DFT(B3LYP) method with 6-31+G(d,p) basis set The stable geometry of the compound was

determined from the potential energy surface scan. Complete vibrational assignments and

Natural Bond Orbital (NBO) analysis for the title compound were carried out. The assignments

of the vibrational spectra were carried out with the help of normal co-ordinate analysis (NCA)

following the Scaled Quantum Mechanical Force Field (SQMFF) methodology. The molecule

orbital contributions were studied by using the total (TDOS), partial (PDOS), and overlap

population (OPDOS) density of states. UV–visible spectrum of the compound was recorded and

the electronic properties, such as HOMO and LUMO energies were performed by time-

dependent DFT (TD-DFT) approach. Mulliken population analyses on atomic charges were also

calculated. Besides, molecular electrostatic potential (MEP) and thermodynamic properties

were performed.

Keywords: L-Alaninium oxalate; FTIR; FT-Raman; DFT; HOMO; LUMO;

1. Introduction

L –Alaninium oxalate organic single crystal possess unique opto-electronic

properties and its molecules have delocalized electron namely, conjugated electron system

exhibit various photo responses such as photoconductive, photo catalytic behavior [1,2].The

organic materials with intermolecular charge transfer have second order non liner optical effects

[3].The title compound is asymmetric carbon atom and non-Centro symmetric space group,

which make them optically active. It zwitterionic in nature has large hyperpolarizability and non-

linear optical effect [4]. In the recent years, amino acid complexes have received much attention

because they proved to be useful in nonlinear optical application. In particular, optically active

amino acids display specific features of interest such as molecular chirality, wide transparency

Journal of Information and Computational Science

Volume 9 Issue 8 - 2019

ISSN: 1548-7741

www.joics.org577

range in the visible and UV spectral region and zwitterionic nature of the molecule, which favors

crystal hardness [5-9].

Recently density functional theory (DFT) has emerged as a powerful tool for analyzing

vibrational spectra of fairly large molecules. The application of DFT to chemical systems has

received much attention because of faster convergence in time than traditional quantum

mechanical correlation methods [10-13]. Literature survey reveals that so far there is no

complete theoretical study for the title compound LAO. In this study, we set out experimental

and theoretical investigation of the conformation, vibrational and electronic transitions of LAO.

In the

ground state theoretical geometrical parameters, IR, Raman and UV spectra, HOMO and LUMO

energies of title molecule were calculated by using Gaussian 03W program. Detailed

interpretations of the vibrational spectra of the LAO have been made on the basis of the

calculated potential energy distribution (PED). The experimental results (IR, Raman and UV

spectra) were supported by the computed results, comparing with experimental characterization

data; vibrational wavenumbers and absorption wavelength values are in fairly good agreement

with the experimental results. The stable position of LAO with respect to alipatic compound was

obtained by performing the potential energy surface (PES) scan with B3LYP/6-31+G(d,p) level

of theory. The redistribution of electron density (ED) in various bonding, antibonding orbitals

and E(2) energies have been calculated by natural bond orbital (NBO) analysis to give clear

evidence of stabilization originating from the hyper conjugation of various intramolecular

interactions. By analyzing the total (TDOS), partial (PDOS), and overlap population (OPDOS)

density of states, the molecular orbital compositions and their contributions to the chemical

bonding were studied. The study of HOMO, LUMO analysis has been used to elucidate

information regarding charge transfer within the molecule. Moreover, the Mulliken population

analyses of the title compound have been calculated and the calculated results have been

reported. The experimental and theoretical results supported each other, and the calculations are

valuable for providing a reliable insight into the vibrational spectra and molecular properties.

2. Experimental details

Colorless crystals of LAO were grown by slow evaporation technique by dissolving L-

Alanine with the aqueous solution of oxalic acid in the stoichiometric ratio 1:1 colorless,

transparent crystals of LAO were obtained within two weeks. Repeated crystallization yielded

good quality crystals. The photograph of the grown crystal of LAO is shown in Fig.1.

The powder X-ray diffraction (XRD) measurements were carried out with Cu Kα radiation

using a Siemens D 500 X-ray diffractometer equipped with a rotating anode scanning (0.01 step

in 2θ) over the angular range 10-70˚ at room temperature generating X-ray by 45 kV and 30 mA

power settings. Monochromatic X-ray of λ=1.5418A˚ Kα1 line from a Cu target were made to

fall on the prepared samples. The diffraction pattern was obtained by varying the scattering angle

2θ from 10˚ to 70˚ in step size of 0.02.



ISSN: 1548-7741

www.joics.org578

The FTIR spectrum of the compound is recorded in Bruker IFS 66V spectrometer in the

range of 4000–400 cm-1. The spectral resolution is ± 2 cm-1. The FT- Raman spectrum of LAO is

also recorded in the same instrument with FRA 106 Raman module equipped with Nd: YAG

laser source operating at 1.064 lm line widths with 200mW power. The spectrum is recorded in

the range of 4000–100 cm-1 with scanning speed of 30 cm-1 min-1 of spectral width 2 cm-1. The

frequencies of all sharp bands are accurate to •± 1 cm-1. The ultraviolet absorption spectrum of

sample solved in water was examined in the range 100–1000 nm by using Cary 5E UV–Vis NIR

recording spectrometer. All the spectral measurements were carried out at Indian Institute of

Technology, Chennai, India.

3. Computational details

The molecular structure optimization of the title compound and corresponding energy

and vibrational harmonic frequencies were calculated using the DFT with Becke-3-Lee–Yang–

Parr (B3LYP) combined with standard 6-31+G(d,p) basis set using GAUSSIAN 03W program

package without any constraint on the geometry [14]. Geometries have been optimized with full

relaxation on the potential energy surfaces at B3LYP/6-31+G(d,p) basis set. The optimized

geometrical parameters, energy, fundamental vibrational frequencies, IR intensity, Raman

activity and the atomic charges were calculated theoretically using GAUSSIAN 03W package.

The Cartesian representation of the theoretical force constants have been computed at optimized

geometry by assuming C1 point group symmetry. Scaling of force field was performed according

to SQM procedure [15,16] using selective scaling in the natural internal coordinate

representation [17,18]. Transformations of the force field and the subsequent normal coordinate

analysis including the least square refinement of the scaling factors, calculation of the potential

energy distribution (PED) and the prediction of IR and Raman intensities were done on a PC

with the MOLVIB program(VersionV7.0-G77) written by Sundius [19,20]. The symmetry of the

molecule was also helpful in making vibrational assignments. The symmetries of the vibrational

modes were determined by using the standard procedure [21] of decomposing the traces of the

symmetry operation into the irreducible representations. The symmetry analysis for the

vibrational modes of LAO is presented in detail in order to describe the basis for the

assignments. By combining the result of the GAUSSVIEW program [22] with symmetry

considerations, vibrational frequency assignments were made with a high degree of confidence.

There is always some ambiguity in designing internal coordinates. However, the defined

coordinates form complete set and matches quite well with the motions observed using the

GAUSSVIEW program. UV–Vis spectra, electronic transitions, vertical excitation energies,

absorbance and oscillator strengths were computed with the Time-Dependent DFT (TD-DFT)

method. The electronic properties such as HOMO and LUMO energies were determined by TD-

DFT approach. To calculate functional group contributions to the molecular orbitals, the total

density of states (TDOS or DOS) the partial density of states (PDOS) and overlap population

density of states (OPDOS) spectra were prepared by using the program Gauss Sum 2.2[23]. The

PDOS and OPDOS spectra were created by convoluting the molecular orbital information with



ISSN: 1548-7741

www.joics.org579

Gaussian curves of unit height and a FWHM (Full Width at Half Maximum) of 0.3 eV. The

contribution of a group to a molecular orbital was calculated by using Mulliken population

analysis.

3.1 The prediction of Raman intensities

The Raman scattering activities (Si) calculated with the GAUSSIAN 03W program were

subsequently converted to relative Raman intensities (Ii) using Raint program [24] by the

following relationship derived from the basic theory of Raman scattering [25]. 4

0( )

[1 exp( )

i i

ii

f v v sIi

hcvv

kT

In the above formula 0 is the laser exciting frequency in cm-1 (in this work, we have used the

excitation wave number ν0 = 9398.5 cm-1, which corresponds to the wavelength of 1064 nm of a

Nd:YAG laser), νi is the vibrational wave number of the ith normal mode (cm-1) and Si is the

Raman scattering activity of the normal mode νi, f (is the constant equal to 10-12) is the suitably

chosen common normalization factor for all peak intensities. h, k, c and T are Planck constant,

Boltzmann constant, speed of light and temperature in Kelvin, respectively.

4. Result and Discussion

4.1 Characterization details of X-ray diffraction analysis

The experimental powder X-ray diffraction pattern of LAO crystal is shown in

Fig.2. Efforts were made to record the powder XRD pattern of the L –Alaninium oxalate crystal

and index them. Obtained unit cell parameters of L- Alanine oxalate compared with L-Alanine

and oxalic acid is shown in Table 1. The calculated Lattice parameter had been determined as a =

5.6304 Å; b = 7.2353 Å; c = 19.597 Å; υ=798.3 Å3 [26]. Which confirm the formation of the title

compound in orthorhombic crystal system.

4.2 Optimized geometry

The Optimized molecular structure of LAO with an atom numbering scheme adopted in

the computation is shown in the Fig.3. The optimized geometric parameters (bond lengths, bond

angles) of the title molecule are presented in Table 2. DFT calculations predict the self-consistent

field (SCF) energy of LAO as -702.1 Hartrees. The lowering of bond angles C(1)-C(3)-C(4)

to109.44˚ and H(16)-C(4)-H(8) to 109.46˚ (normally 120˚) is due to the charge transfer from the

oxalate anion to the alaninium cation which enhances the optical nonlinearity of the molecule.

The important geometrics such as C(1)-O(5) and C(1)-O(6) bond distances 1.21 and 1.31Ǻ and

C(3)-C(1)-O(5) and C(3)-C(1)-O(6) bond angles 120˚ and 120˚ respectively of one amino acid

residue suggest the presence of deprotonated carboxylate group. The H(17)….O(9) distance of

3.4134Ǻ is an increase strong C-H-O hydrogen boding and this length is significantly shorter

than the vandar Waals separation between the O atom and H atom [27]. Computed values show



ISSN: 1548-7741

www.joics.org580

that the bond length of N(2)-H(13) and N(2)-H(14) are 1.02Ǻ and 1.02Ǻ respectively. The same

value in N-H distance in the NH3 group indicated the existence N-H…..O hydrogen bonding.

Detail description of vibrational modes can be given by means of normal

coordinate analysis (NCA). For this purpose the full set of 57 standard internal coordinates for

LAO are define as given in Table 3. From these, a non-redundant set of local symmetry

coordinates were constructed by suitable linear combinations of internal coordinated following

the recommendations for Forgrasi et al. [28, 29] are summarized in Table 4. The theoretically

calculated DFT force field were transformed to this latter set of vibrational coordinates and used

in all subsequent calculations.

4.2. Vibrational band assignments

According to the theoretical calculations, LAO has a structure of C1 point group

symmetry. The molecule has 21 atoms and 57 modes of fundamental vibrations. We have taken

recourse to the calculation and visualization of contribution of internal coordinates in each

normal mode by Gaussian package [14] and chemcraft program. The harmonic vibrational

frequencies calculated for the title compound at B3LYP levels using 6-31+G(d,p) along with the

observed FT-IR and FTR frequencies for various modes of vibrations are presented in Table 5.

Some bands found in the predicted FT-IR and FTR spectra were not observed in the

experimental spectra of LAO. Therefore, a linearity between the experimental and scaled

calculated wave numbers for DFT method of LAO can be estimated by plotting the calculated

versus experimental wave numbers as shown in Fig.4. The correlation coefficients (R2) for

experimental and observed wave numbers computed from the DFT method were found to be

0.964. It can be noted from the R2 values that the theoretical prediction is in good agreement

with the experimental wave numbers. Also Fig.4 reveals the overestimation of the calculated

vibrational modes due to neglect of anharmonicity in real system. Inclusion of electron

correlation in DFT to a certain extent makes the frequency values smaller in comparison with the

HF frequency data. For the plots of simulated IR and Raman spectra, pure Lorentzian band

shapes were used with a bandwidth of 40 cm-1. Figs.5 and 6 shows a comparative representation

of theoretical and experimental FT-IR and FTRaman spectra, respectively.

4.2.1 O-H vibrations

The O-H group gives rise to three vibrations (stretching, inplane bending and out-of-

plane bending vibrations). The O-H group vibrations are likely to be the most sensitive to the

environment, so they show pronounced shifts in the spectra of the hydrogen bonded species. The

hydroxyl stretching vibrations are generally [30] observed in the region around 3500 cm-1. In the

case of the unsubstituted phenols it has been shown that the frequency of O-H stretching

vibration in the gas phase is 3657 cm-1 [31]. Similarly in our case a FT-IR band at 3450 cm-1 is

assigned to O-H stretching vibrations. A comparison of this band with that of the computed by

B3LYP/6-31+G(d,p) method (mode no. 57) at 3622 cm-1 show positive deviation of ~60 cm-1,

this may be due to the presence of strong intermolecular hydrogen bonding. The O-H in-plane



ISSN: 1548-7741

www.joics.org581

bending vibration in phenols, in general lies in the region 1150-1250 cm-1 and is not much

affected due to hydrogen bonding unlike to stretching and out-of-plane bending frequencies [30].

The medium strong band in FT-IR spectrum at 1250 cm-1 is assigned to O-H inplane bending

vibration for both the O-H groups in the ring. The theoretically computed value (mode no.36) at

1196 cm-1 by B3LYP/6-31+G(d,p) method (Table 5) show very good agreement with recorded

spectrum. The O-H out-of-plane bending mode for the free molecule lies below 300 cm-1 and it

is beyond the infrared spectral range of the present investigation. However, for the associated

molecule [32], the O-H out-of-plane bending mode lies in the region 517-710 cm-1 in both

intermolecular and intramolecular associations, the frequency is at a higher value than in free O-

H. The band at 490 cm-1 by B3LYP/6-31+G(d,p) method (mode no. 17) show excellent

correlation with recorded FTIR and FT-Raman bands at 490 cm-1 and 470 cm-1 respectively, but

this mode is a mixed mode as shown in Table 5.

4.2.2 N-H vibrations

The scaled -NH2 asymmetric and symmetric stretches in the range 3319-3236 cm-1 is in

agreement with experimental value of 3166-3126 cm-1. The PED of this mode is contributing

96% for asymmetric and 99% for symmetric stretching mode. The computed -NH2 scissoring

vibration at 1538 cm-1 is in excellent agreement with expected characteristic value 1600 cm-1

[33,34]. This is also very good agreement with recorded FT-IR value of 1495 cm-1. The C-NH2

out-of-plane and in-plane bending vibrations at 391 cm-1, is also in good agreement with the

assignment in the experimental data. The NH2 wagging computed at 463 cm-1 is missing in both

FT-IR and FT-Raman spectra.

4.2.3 Methyl group vibrations

The CH stretching in CH occurs at lower frequencies than those of the aliphatic

compound (3000–2800 cm-1) [35]. In the present work, CH3 asymmetric stretching is found at

2980 cm-1 in FT-IR and 2933 cm-1 in Raman spectrum. The CH symmetric stretching is found at

2932 cm-1 in FT-Raman. For methyl substituted aliphatic derivatives the symmetric bending

deformations and rocking modes normally appear around 1465–1440 cm-1 and 1040–990 cm-1

respectively [36]. In the present investigation a strong peak at 1440 cm-1 in FT-IR is assigned to

symmetric bending deformation. The in-plane rocking mode appears around 1420 cm-1 in

Raman. The out-of-plane rocking modes are observed around 1180 cm-1 in FT-Raman spectrum.

All these frequencies are shifted towards the maximum. This implies, the methyl vibrations are

favored by the presence of NH2 in the ring. These observations agree well with the earlier work

[37,38]. Also all the above observed frequencies coincide very well with the calculated

frequencies. The in-plane and out-of-plane bending vibrations lie around 410 cm-1 in FT-IR and

380 cm-1 in FT-Raman. CH torsional mode is expected around 50-100 cm-1 in FT-Raman

spectrum. The observed wavenumber (in FTRaman) at 80 cm-1 (mode no.8) is assigned to CH3

torsional mode, shows good agreement with computed wavenumber at 70 cm-1 by B3LYP

method.



ISSN: 1548-7741

www.joics.org582

4.2.4 C=O and C-O vibrations

The band observed in the region 1700–1800 cm-1 is usually the most characteristic

feature of carboxylic group. This band is due to the C-O stretching vibration. Also Koczon et al.

[39] observed the range of 1800–1500 cm-1, the C-C and C=O are group stretching vibrations.

The C=O stretching vibration of the LAO is observed at 1740 and 1590cm-1 in FT-IR and 1700

and 1600 cm-1 in FT-Raman spectrum and these wavenumbers are good coherent with empirical

values. Also this mode is observed at 1703 and 1682 cm-1 in FT-IR and FT-Raman spectrum by

Swislocka et al. [40]. The C=O and C-O vibrations also show fairly good coherent in literature

[41].

4.2.5 C-N vibrations

The identification of C-N vibration is a very difficult task, as mixing of several

bands is possible in this region. In this study, the bands of moderate intensity found at 1360cm-1

in FTIR spectra and 1365 cm-1 in FTRaman spectra, respectively, maybe due to interaction

between C-N stretching and N-H bending of C-N-H group [42]. Hence, they are assigned to

asymmetric and symmetric bending vibrations, respectively. The band observed at 1300 cm-1 in

FTIR spectrum is due to C-N-H bending vibration. These are in good agreement with the

computed values. Silverstein et al. [43] assigned C-N stretching absorption in the region 1342–

1266 cm-1.In this study, the band identified at 1270 cm-1 in FTRaman spectrum is assigned to C-

N stretching vibration. The theoretical scaled wave numbers at 410 and 402 cm-1 for the C-C-N

asymmetric and symmetric deformation vibration with PED 35 and 34%, respectively, which fall

in FTRaman spectrum at 410 and 402 cm-1(mode nos. 16 and 15) are in good agreement with the

experimental value. Puviarasan et al. [44] assigned frequencies at 300 and 213 cm-1 in FTRaman

spectrum, which have been assigned to in-plane and out-of-plane bending of C-N-C vibrations.

The theoretically computed values of C-N-C deformations also fall at 291 and 219 cm (mode

Nos 12 and 9), and are found to be in good agreement with the experimental data. The PED

corresponding to this vibration is 61%. The band observed at 508 cm-1 in FTIR spectrum which

has been assigned to N-C-C bending vibration is also in good agreement with the theoretical

value (mode No. 18).

4.2.6 C-H stretching modes

The hetero aromatic structure shows the presence of C-H stretching vibration in the

region 3100–3000 cm-1, which is the characteristic region for the ready identification of C-H

stretching vibrations [45]. In this region, the nature of the substituents does not make any

appreciable change [46]. Gunasekaran et al. [47] have reported the presence of C-H stretching

vibrations in the region 3100–3000 cm-1 for asymmetric stretching and 2990–2850 cm-1for

symmetric stretching. In this molecule, the FTIR band at 3059 cm-1and FTRaman band at 3050

cm-1 represent asymmetric stretching vibration. The FTIR and FTRaman bands at 2980 cm-1 and

2933 cm-1 represent C-H symmetric stretching vibrations. The scaled vibrations calculated at

3029 cm-1 ,and 3013cm-1 by B3LYP/6-31+G(d,p) method (mode Nos 52, and 51) which are

listed in Table 5. correspond to asymmetric and symmetric stretching mode of CH units with the



ISSN: 1548-7741

www.joics.org583

PED contribution of 98 and 95%, respectively. The bands corresponding to in-plane and out-of-

plane bending and deformation vibrations of CH group are presented in Table 5. The

experimental frequencies at 1063 cm-1 in FTIR spectra and at 1040 cm-1 in FTRaman spectra and

frequencies at 1063 cm-1 in FTIR spectra [48] which have been assigned to C-CH asymmetric

and symmetric bending vibrations, respectively, are compared with the theoretically calculated

values. The bands observed at 820 and 790 cm-1 in FTIR spectrum and at 814 cm in FTRaman

spectrum, respectively, have been assigned to asymmetric and symmetric N-CH deformation,

and in Raman

spectrum[49] the band observed at 754 cm-1 has been assigned to N-CH deformation. These

assigned frequencies coincide well with the theoretically computed values (mode Nos 28–25).

The wave number calculated by the B3LYP/6-31+G(d,p) method for the C-C-CH deformation

mode at 323 cm-1 is identified at 320 cm-1(mode No. 13) in the FTRaman spectrum [49], and is

found to be in good agreement with the experimental data with the contribution of 48% PED.

5. UV–vis spectra analysis

In the UV–vis region with high extinction coefficients, all molecules allow strong π-π*

and σ-σ* transition [50]. In an attempt to understand the nature of electronic transitions in terms

of their energies and oscillator strengths, time-dependent DFT (TD-DFT) calculations involve

configuration interaction between the singly excited electronic states are conducted. The

calculated excitation energies, oscillator strength (f) and wavelength (λ) and spectral assignments

are given in Table 6. The major contributions of the transitions are designated with the aid of

SWizard program [51]. The theoretical absorption wavelengths (in gas phase and solvent) are

compared in Table 6. Due to the Frank–Condon principle, the maximum absorption peak (λmax)

in an UV–visible spectrum corresponds to vertical excitation. TD-DFT calculations predict three

transitions in the UV–vis region for LAO molecule. The strong transitions at 2.67 eV (463 nm)

with an oscillator strength f = 0.5622 in gas phase, at 3.07 eV (402 nm) with an oscillator

strength f = 0.0007 in water solvent are assigned to n-π* transition. The experimental and

theoretical UV–Vis spectrum of LAO is shown in Fig. 7. In view of calculated absorption

spectra, the maximum absorption wavelength corresponds to the electronic transition from the

HOMO to LUMO with 100% contribution. The other wavelength, excitation energies, oscillator

strength and calculated counterparts with major contributions can be seen in Table 6. The

frontier molecular orbitals, HOMO and LUMO and frontier orbital gap helps to exemplify the

chemical reactivity and kinetic stability of the molecules [52]. The HOMO is the orbital that

primarily actsas an electron donor and the LUMO is the orbital that largely acts as the electron

acceptor. In order to evaluate the energetic behavior of the title compound, we carried out

calculations in gas and in solvent (water). HOMO and LUMO energies of HOMO-1, HOMO

(first excited state), lumo (ground state), HOMO-1 and their orbital energy gaps are calculated

by TD-DFT/B3LYP/6-31+G(d,p) in solvent (water) and Gas phase are presented in Table 6. The

3D plots of the frontier orbitals namely ground state (HOMO), HOMO+1 and first excited state

(LUMO), LUMO+1 are ∆E= -0.12061 eV ∆E= -0.26233 eV shown in Fig. 8. The positive phase



ISSN: 1548-7741

www.joics.org584

is blue and the negative one is red. It can be seen from the plots that the HOMO levels are spread

over the amino and carboxylate group expect the methyl group and H atoms. The LUMO of first

excited state is almost uniformly distributed over the molecule expect the H atoms, methyl atoms

and CH atoms. The energy gap of HOMO–LUMO explains the eventual charge transfer

interaction within the molecule, which influences the biological activity of the molecule.

Furthermore, in going from the gas phase to the solvent phase, the increasing value of the energy

gap and molecule becomes more stable. This electronic absorption corresponds that is mainly

described by one electron excitation from the highest occupied molecular or orbital (LUMO).

The energy difference between HOMO and LUMO orbital is a critical parameter in determining

molecular electrical transport properties because it is a measure of electron conductivity,

calculated by B3LYP/6-31+G(d,p) method is -0.12061 eV for the title molecule. The computed

energy values of LAO by B3LYP/6-31+G(d,p) method is presented in Table 7. The observed

transition from HOMO to LUMO is π – π*. Moreover lower in the HOMO and LUMO energy

gap explains the eventual charge transfer interactions taking place within the molecule.

5.1 Total, partial, and overlap population density-of-states

In the boundary region, neighboring orbitals may show quasi degenerate energy levels. In

such cases, consideration of only the HOMO and LUMO may not yield a realistic description of

the frontier orbitals. For this reason, the total (TDOS), partial (PDOS), and overlap population

(OPDOS or COOP (Crystal Orbital Overlap Population)) density of states [53–55], in terms of

Mulliken population analysis were calculated and created by convoluting the molecular orbital

information with Gaussian curves of unit height and full width at half maximum (FWHM) of 0.3

eV by using the GaussSum 2.2 program [23]. The TDOS, PDOS and OPDOS of the LAO are

plotted in Figs. 9–11, respectively. They provide a pictorial representation of MO (molecule

orbital) compositions and their contributions to chemical bonding. The most important

application of the DOS plots is to demonstrate MO compositions and their contributions to the

chemical bonding through the OPDOS plots which are also referred in the literature as COOP

diagrams. The OPDOS shows the bonding, anti-bonding and nonbonding nature of the

interaction of the two orbitals, atoms or groups. A positive value of the OPDOS indicates a

bonding interaction (because of the positive overlap population), negative value means that there

is an anti-bonding interaction (due to negative overlap population) and zero value indicates

nonbonding interactions [56]. Additionally, the OPDOS diagrams allow us to determine and

compare of the donor– acceptor properties of the ligands and ascertain the bonding, non-

bonding. The calculated total electronic density of states (TDOS) diagrams of the LAO is given

in Fig. 9. The partial density of state plot (PDOS) mainly presents the composition of the

fragment orbitals contributing to the molecular orbitals which is seen from Fig. 10. As seen Fig.

11, HOMO orbitals are localized on the ring and their contributions are about 14%. The LUMO

orbitals are localized on the ring (84%) of the compound. Only based on the percentage shares of

atomic orbitals or molecular fragments in the molecule is difficult to compare groups in terms of

its bonding and anti-bonding properties. Thus the OPDOS diagram is shown in Fig. 11 and some



ISSN: 1548-7741

www.joics.org585

of orbitals of energy values of interaction between selected functional groups which are shown

from figures easily, (O–H) atoms (green line) are negative (anti-bonding interaction). As can be

seen from the OPDOS plots for the LAO have anti-bonding character in frontier HOMO and

LUMO molecular orbitals for pyridine and oxygen atoms. Also OPDOS showed bonding

character both HOMO and LUMO.

5.2 Global and local reactivity descriptors

Based on the density functional descriptors, global chemical reactivity descriptors

of the title molecule such as ionization potential (I), electron affinity (A), chemical potential (μ),

electronegativity (χ), global hardness (ƞ), global softness(σ) and global electriphilicity (ω) values

can be described as followed [57]. In simple molecule orbital theory approaches, the HOMO

energy (E HOMO) is related to the ionization potential (I) by Koopman’s theorem and LUMO

energy (ELUMO) has been used to estimate the electron affinity (A) [58].

( )

( )

HOMO

LUMO

Ionizationpotential I E

Electronaffinity A E

The average value of the HOMO and LUMO energy is related to the electronnegativity (χ)

define by Mulliken [71]

( )( )

2

I AElectronegativity

In addition, the HOMO and LUMO energy is related to the hardness (ƞ) and softness (σ) [59].

( )

2

1( )

I AGlobalhardness

Globalsoftness

Parr et al. [60] defined global electriphilicity (ω)

2

( )2

Electriphilicity

Where μ is the chemical potential takes the average value of ionization potential (I) and electron

affinity (A) [61].

( )( )

2

I AChemicalpotential



ISSN: 1548-7741

www.joics.org586

The electronic chemical potential is the parameter which describes the escaping tendency

of electrons from an equilibrium system. Thus the frontier molecular orbital analysis also

provided the detailed on chemical stability, chemical hardness and electronegativity of the

molecule in B3LYP/6-31+G(d,p) basis set are presented in Table 7, respectively.

6. NBO analysis

By using the second-order bond–antibond (donor–acceptor) NBO energetic analysis,

insight into the most important delocalization schemes was obtained. The change in electron

density (ED) in the (σ*, π*) antibonding orbitals and E(2) energies have been calculated by

natural bond orbital (NBO) analysis [63] using DFT method to give clear evidence of

stabilization originating from various molecular interactions. The hyperconjugative interaction

energy was deducted from the second-order perturbation approach [63] 2

(2) ij

i j i

j i

FE E q

where qi is the donor orbital occupancy, εi and εj are diagonal element, and F (i, j) is the off

diagonal NBO Fock matrix element. The larger E(2) value the more intensive is the interaction

between electron donors and acceptor, i.e. the more donation tendency from electron donors to

electron acceptors and the greater the extent of conjugation of the whole system [64].

Delocalization of electron density between occupied Lewis’s type (bond or lone pair) NBO

orbital and formally unoccupied (anti bond or Rydberg) non-Lewis NBO orbital corresponds to a

stabilizing donor–acceptor interaction. NBO analysis has been performed on the LAO molecule

at the B3LYP/6-31+G (d,p) level to elucidate, the intra-molecular rehybridization and

delocalization of electron density within the molecule. The strong intramolecular

hyperconjugation interaction of the σ and π electrons of C–C to the anti C–C bond to the ring

leads to stabilization of some part in the ring as evident from Table 8. The intra molecular

hyperconjugative interaction of the (C1–C3) distribute to (C1–O5), (N2–H21) , (C3–C4), (C4-H24)

and (N2-H19) leading to stabilization of 0.83, 1.07,0.54, 2.32 and 0.961 kJ/mol respectively. This

enhanced further conjugate with anti bonding orbital of σ*(C1–C3), (C7–C9), leads to strong

delocalization of 4.70 and 1.14 kJ/mol respectively.

6.1 Natural population analysis

Natural population analysis[65](NPA) data of monomer and tetramer were used to

investigate the changes in charge, which give some insight into the interaction taking place upon

aggregation. For the sake of comparison, the calculated natural charges of LAO are presented in

Table 9. It shows that an atoms C13 has the most electronegative charge of -5.23961and O6 has

the most electropositive charge of 8.80348e. Likewise, C1 and C14 atom has considerable

electro negativity and they are tending to donate an electron. Conversely, the C3,C4 and C9

atoms have considerable electropositive and they are tending to acquire electron. Further, the

natural population analysis showed that 142 electrons in the title molecule are distributed on the

sub shell as follows:



ISSN: 1548-7741

www.joics.org587

Core: 35.98980 (99.9717% of 36)

Valence: 105.55477 (99.5800% of 106)

Rydberg: 0.45543 (0.3207% of 142)

7. Fukui function analysis

The Fukui function is among the most basic and commonly used reactivity indicators.

The Fukui function is given as the change in the density function ρ(r) of the molecule as a

consequence of changing the number of electrons N in the molecule, under the constraint of a

constant external potential. The Fukui function is defined as:

rN

rrF

where ρ (r) is the electronic density, N is the number of electrons and r is the external

potential exerted by the nuclease. Fukui functions are introduced, which are advocated as

reactivity descriptors in order to identify the most reactive sites for electrophilic or nucleophilic

reactions within a molecule. The Fukui function indicates the propensity of the electronic density

to deform at a given position upon accepting or donating electrons [66,67]. Also, it is possible to

define the corresponding condensed or atomic Fukui functions on the jth atom site as,

)1()1(2

1

)()1(

)1()(

0

NqNqf

NqNqf

NqNqf

jjj

jjj

jjj

for an electrophilic rf j

, nucleophilic or free radical attack rf j

, on the reference

molecule, respectively. In these equations, qj is the atomic charge (evaluated from Mulliken

population analysis, electrostatic derived charge, etc.) at the jth atomic site in the neutral (N),

anionic (N+1) or cationic (N-1) chemical species. Here, it is important to mention that

independently of the approximations used to calculate the Fukui function, all of them follow the

exact equation:

1drrf

which is important in the use of the Fukui function as an intramolecular reactivity index.

The values of the Fukui function calculated from the NBO charges. The values of Fukui

function analysis obtained by employing MEP and Mulliken charges. The results were obtained



ISSN: 1548-7741

www.joics.org588

from the NBO charges. From Table 10 note the presence of negative values of the Fukui

function. Recently it was reported that a negative Fukui function value means that when adding

an electron to the molecule, in some spots, the electron density is reduced; alternatively when

removing an electron from the molecule, in some spots, the electron density is increased.

From the calculated values, the reactivity order for the electrophilic case was C1 > N2 >

C3 > C4 > O5 > O6 > O9 > O10 > O11 > O12> H15> H16> H19 On the other hand, for

nucleophilic attack we can observe C7 > C8 > H13 > H14 > H17 > H18 > H20 > H21. Position

of reactive electrophilic sites and nucleophilic sites are accordance with the total electron density

surface and chemical behavior. If one compares the three kinds of attacks it is possible to

observe that, electrophilic attack is bigger reactivity comparison with the nucleophilic and

radical attack.

8. Molecular electrostatic potential surface

MEP is related to the electronic density and is a very useful descriptor in understanding

sites for electrophilic and nucleophilic reactions as well as hydrogen bonding interactions

[68,69]. The electrostatic potential V(r) is also well suited for analyzing processes based on the

“recognition” of one molecule by another, as in drug-receptor, and enzyme- substrate

interactions, because it is through their potentials that the two species first “see” each other

[70,71]. To predict reactive sites of electrophilic and nucleophilic attacks for the investigated

molecule, MEP at the B3LYP/6-31+G (d,p) optimized geometry was calculated. The negative

(red) regions of MEP were related to electrophilic reactivity and the positive (yellow) regions to

nucleophilic reactivity (Fig. 12). The negative region is localized on the carbon atoms and the

positive region is localized on the nitrogen atom. These results provide information concerning

the region where the compound can interact intermolecularly and bond metallically. Therefore,

Fig.12 confirms the nonexistence of intermolecular interactions within the molecule.

9. Mulliken population analysis

The Mulliken atomic charges are calculated by determining the electron population of

each atom as defined by the basis function [71]. The Mulliken atomic charges of LAO molecule

calculated by B3LYP/6-31+G(d,p) basis set. Calculation of effective atomic charges plays an

important role in the application of quantum chemical calculations to molecular systems. Our

interest here is in the comparison of different methods to describe the electron distribution in

LAO as broadly as possible, and assess the sensitivity, the calculated charges to changes in (i)

the choice of the basis set; (ii) the choice of the quantum mechanical method. Mulliken charges,

calculated the electron population of each atom defined in the basic functions. The Mulliken

charges calculated at different levels and at same basis set are listed in Table 11. The results can,

however, better represent in graphical form as given Fig. 13. The charges depending on basis set

are changed due to polarizability. The H20 and H21 atoms have more positive charges at

B3LYP/6-31+G(d,p). This is due to the presence of electronegative oxygen atom; the hydrogen

atoms attract the positive charge from the oxygen atoms The C1,C7 and C8 atoms by B3LYP



ISSN: 1548-7741

www.joics.org589

method is more negative charges than the other atoms due to electron accepting substitutions at

that position in LAO. The result suggests that the atoms bonded to O atom and all H atoms are

electron acceptor and the charge transfer takes place from O to H in LAO.

10. First order hyperpolarizability

In discussing nonlinear optical properties, the polarization of the molecule by an external

radiation field is often approximated as the creation of an induced dipole moment by an external

electric field. Under the weak polarization condition, we can use a Taylor series expansion in the

electric field components to demonstrate the dipolar interaction with the external radiation

electric field. The first order hyperpolarizability (β0) and related properties (α, β0 and ∆α) of

LAO are calculated based on the finite-field approach. In the presence of an applied electric

field, the energy to a system is a function of the electric field. The first-order hyperpolarizability

is a third rank tensor that can be described by a 3 3 3 matrix. The 27 components from the

3D matrix can be reduced to 10 components due to the Kleinman symmetry [72]. The

components of β are the coefficients in the Taylor series expansion of the energy in the external

electric field. When the electric field is weak and homogeneous, this expansion becomes.

0 1 1......

2 6E E F F F F F F

where E0 is the energy of the unperturbed molecules, Fα is the field of the origin μα, ααβ and βαβγ

are the components of dipole moment, polarizabiltiy and the first-order hyperpolarizability

respectively. The total static dipole moment μ, the mean polarizability α0, the anisotropy of the

polarizability ∆α and the mean first hyperpolarizability β0, using the x, y and z components are

followed: 1

2 2 2 2( )x y z

03

xx yy zz

1 1

2 2 22 22 ( ) ( ) 6xx yy yy xx xx

yyzxxzzzzz

yzzxxyyyyy

xzzxyyxxxx

zyx

and

2

1

222

0 )(



ISSN: 1548-7741

www.joics.org590

The calculated hyperpolarizability values of LAO are given in Table 12. The value of

second order optical susceptibility χ2 in a given depends on the molecular hyperpolarizability β,

the number of chromophores and the degree of non-centro symmetry. The computed first-order

hyperpolarizability, βtotal of the LAO molecules is .,..106129.3 30 use which that of urea is 10

times.

11. Thermodynamic Parameters

The standard statistical thermodynamic functions at B3LYP/6.31+G(d,p) level heat

capacity (C0p,m), entropy (S0

m) and enthalpy (Hm0) for the title compound are obtained from the

theoretical wavenumbers (Table13), which shows that these thermodynamic functions are

increasing with temperature ranging from 100 to 1000 K due to the fact that the molecular

vibrational intensities increase with temperature [73]. The correlation equations between heat

capacity, entropy, enthalpy changes and temperatures are built-in by quadratic formulas. The

fitting factors (R2) for these thermodynamic properties are 1.0000, 1.0000 and 1.0000

respectively. The corresponding fitting equations are as follow and the correlation graphs of

those are represented in Figure. 14.

These equations could be used for the further studies on the title compound. They can be

used to compute the other thermodynamic energies according to relationships of thermodynamic

functions and estimate directions of chemical reactions according to the second law of

thermodynamics in thermo chemical field. It is to notice that all thermodynamic calculations are

done in gas phase only and they cannot be used in liquid phase.

12. Conclusion

The organic NLO material from the amino acid family, viz L-Alaninium oxalate (LAO)

was grown by slow evaporation method. From the XRD analysis of the grown crystal, lattice

parameters were calculated. They are in good agreement with reported values. Optimized

geometry of the molecules shows the existence of C-H…O carbon bonding in the molecule.

Assignments of the vibrational bands have been done. The molecular geometry, HOMO and

LUMO energy and thermo-dynamical properties in the ground state have also been calculated.

The lowering of the HOMO-LUMO energy gap value suggests the possibility of intermolecular

charge transfer in the molecule making it a suitable NLO active compound. The correlations

between the statistical thermodynamic and temperature were also obtained. It is seen that the

heat capacities, entropies and enthalpies increase with increase temperature of molecule.

0 4 2 2

,

0 4 2 2

0 4 2 2

71.96 0.346 0.001 10 ( 1.0000)

276.9 1.602 0.003 10 ( 1.0000)

0.064 0.067 0.0001 10 ( 1.0000)

p m

m

m

C T T R

S T T R

H T T R



ISSN: 1548-7741

www.joics.org591

References

[1] H.S.Nalwa and S.Miyata, Non Linear Optics Of Organic Molecules And Polymers, CRC

Press, Boca Raton,1997.

[2] P.Gunter, Non Linear Optical Effects And Materials, Springer Verlag, Berlin 2000.

[3] M.Lydia Cardinea and S. Vasudevan, mater chem.phys.113 (2009) 670-672.

[4] S. Moitra and T.Kar, Cryst.Res.Technol.45 (2010) 70-74.

[5] R.Rameshbabu, N.Vijayan, R.Gopalakrishnan, P.Ramasamy, Cryst.Res.Technol 41(2006)

405-410.

[6]. K. Ambujam, K. Rajanbabu, S. Selvakumar, I.Vethapotheher, P.G. Joseph, P. Sagayaraj,

J. Cryst. Growth 286 (2006) 440-444.

[7] R. Mohankumar, K. Rajanbabu, D. Jayaraman, R. Javavel, K. Kitamura, J. Cryst.Growth,

275 (2005)1935-1939.

[8] Tapati mallik, Tanusree kar, J. Cryst. Growth, 285 (2005) 178-182.

[9] S. Dhanuskodi, K. Vasantha, Cryst. Res. Technol 39 (2004) 259-265.

[10] N.Sundaraganesan, S.Ilakiamani, P.Subramani, B.Dominic Joshua 67 (2007) 628-635.

[11] M.Sekerci, Y.Atalay, F.Yakuphanoglu, D.Avci, A. Bas, Spectrochim Acta 67 (2007)

503-508.

[12] C.Ravikumar, I.Hubert Joe, D. Sajan, Chem. Phys 369 (2010) 1-7.

[13] C.Ravikumar, I.Hubert Joe, Chem. Chem. Phys 12 (2010) 9452-9460.

[14] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Suzerain, M.A. Robb, J.R. Cheeseman Jr.,

J.A. Montgomery, T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,

J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson,

H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,M. Ishida,

T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P. Hratchian,

J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev,

A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth,

P. Salvador, J.J. Dannenberg,V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain,

O. Farkas, D.K. Malick, A.D. Rabuck,K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui,

A.G. Baboul, S. Clifford, J. Cioslowski, B. Stefanov, G. Liu,A. Liashenko, P. Piskorz,

I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al- Laham, C.Y. Peng, A. Nanayakkara,

M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople,

Gaussian 03, Revision A.I, Gaussian, Inc., Pittsburgh, PA, 2003.

[15] G. Rahut, P. Pulay, J. Phys. Chem 99 (1995) 3093–3100.

[16] P. Pulay, G. Fogarasi, G. Pongor, J.E. Boggs, A. Vargha, J. Am. Chem. Soc 105 (1983)

7037–7047.

[17] G. Fogarasi, P. Pulay, in: J.R. Durig (Ed.), Vibrational Spectra and Structure, 1985,

vol.14, Elsevier, Amsterdam, pp. 125–219 (Chapter 3).

[18] G. Fogarasi, X. Zhou, P.W. Taylor, P. Pulay, J. Am. Chem. Soc.1992, 114, 8191–8201.

[19] T. Sundius, Vib. Spectrosc,2002, 29 ,89–95.

[20] MOLVIB (V.7.0): Calculation of Harmonic Force Fields and Vibrational Modes of



ISSN: 1548-7741

www.joics.org592

Molecules, QCPE Program No. 807, 2002.

[21] F.A. Cotton, Chemical Applications of Group Theory, Wiley Interscience, New York, 1971.

[22] A. Frisch, A.B. Nielson, A.J. Holder, GAUSS VIEW User’s Manual, Gaussian Inc.,

Pittsburgh, PA, 2000.

[23] N.M. O’Boyle, A.L. Tenderholt, K.M. Langner, J. Comput. Chem 29(2008) 839–845.

[24] D. Michalska, Raint Program, Wroclaw University of Technology, 2003.

[25] D. Michalska, R. Wysokinski, Chem. Phys. Lett 403 (2005) 211–217.

[26] M.Subha nandhini, R.V. Krishnakumar, S.Natarajan. Acta Crystallogr., Sec E 57 (2001)

633- 635.

[27] A.Bondi, J.Phys.Chem 68 (1964) 441-451.

[28] D. Sajan, I. Hubert Joe, V.S. Jayakumar, J. Zaleski, J. Mol. Struct 785 (2006) 43-53.

[29] D. Michalska, D.C. Bienko, A.J.A. Bienko, Z. Latajka, J. Phys.Chem 100 (1996) 1186-1195.

[30] G. Varsanyi, Assignments of Vibrational Spectra of Seven Hundred Benzene Derivatives,

vols. 1-2 (1974) Adam Hilger.

[31] R.A. Yadav, I.S. Sing, Ind. J. Pure Appl. Phys 23 (1985) 626-627.

[32] A. Eriksson, J. Lindgren, K. Stojanoski, J. Mol. Struct 143 (1986) 167-170.

[33] F.R. Dollish, W.G. Fateley, F.F. Bentely, Characteristic Raman Frequencies on Organic

Compounds, Wiley, New York, 1997

[34] J.F. Arenas, I. Tocon, J.C. Otera, J.I. Marcos, J. Mol. Struct 410–411 (1997) 443–446.

[35] B.S. Furnell, Vogel Text Book of Practical Organic Chemistry, fifth ed., Long Man

Widely, New York.1989.

[36] L.G. Wade, Advanced Organic Chemistry, fourth ed., Wiley, New York. 1992.

[37] P. Koczon, J.Cz. Dobrowolski, W. Lewandowski, A.P. Mazurek, J. Mol. Struct 655 (2003)

89–95

[38] R. Swislocka, E. Regulska, M. Samsonowicz, W. Lewandowski, Polyhedron 28 (2009)

3556–3564.

[39] E.I. Paulraj, S. Muthu, Spectrochim. Acta A 108 (2013) 38–49.

[40] G. Socrates, Infrared Characteristic Group Frequencies, John Wiley and sons, New York,

1980.

[41] Y. Saito, K. Machinda, and T. Uno, Vibrational spectra of methylurea, Spectrochim. Acta

A, Mol. Spectrosc. 3 (1975), pp. 1237–1244.

[42] N. Puviarasan, V. Arjunan, and S. Mohan, FTIR and FT-Raman spectral investigations on

4-aminoquinaldine and 5-aminoquinoline, Turk. J. Chem. 28 (2004), pp. 53–66.

[43] G. Varsanyi, Assignments for vibrational spectra of seven hundred alipahtic derivatives,

Vol. 1/2, Academic Kiado, Budapset, 1973.

[44] S. Mohan and R. Murugan, Laser excited Raman spectrum vibrational analysis of 3,6-

dichloropyridazine, Indian J. Pure Appl. Phys. 31 (1993), pp. 496–499.

[45] S. Gunasekaran, R. ArunBalaji, S. Seshadri, and S. Muthu, Vibrational spectra and normal

coordinate analysis on structure of nitrazepam, Indian J. Pure Appl. Phys. 46 (2008), pp.

162–168.



ISSN: 1548-7741

www.joics.org593

[46] S. Gunasekaran, S. Kumaresan, R. ArunBalaji, G. Anand, and S. Srinivasan, Density

functional theory study of vibrational spectar and assignment of fundamental modes of

decarbazine, J. Chem. Sci. 120 (2008), pp. 315–324.

[47] N. Sundaraganesan, C. Meganathan, H. Saleem, and B.D. Joshua, Vibrational spectroscopy

investigation using ab initio and density functional theory analysis on the structure of 5-

amino-o-cresol, Spectrochim. Acta A 68 (2007), pp. 619–625.

[48] R.M. Silverstein, G.C. Bassler, T.C. Morrill, Spectrometric Identification of Organic

Compounds, John Wiley, Chichester, 1991

[49] S.I. Gorelsky, SWizard Program Revision 4.5, University of Ottawa, Ottawa, Canada, 2010,

<http://www.sg.chem.net/>.

[50] I. Fleming, Frontier Orbitals, Organic Chemical Reactions, John Wiley and Sons,New

York,

1976.

[51] R. Hoffmann, Solids and Surfaces: A Chemist’s View of Bonding in Extended Structures,

VCH Publishers, New York, 1988.

[52] T. Hughbanks, R. Hoffmann, J. Am. Chem. Soc. 105 (1983) 3528–3537.

[53] J.G. Małecki, Polyhedron 29 (2010) 1973–1979.

[54] M. Chen, U.V. Waghmare, C.M. Friend, E. Kaxiras, J. Chem. Phys. 109 (1998) 6854–6860.

[55] S.Saravanan, V.Balachandran, Spectrochim Acta A 120 (2014) 351.364.

[56] P.Politzer, J.S. Murray, The fundamental nature and role of the electrostatic potential in

atoms and molecules, Theor. Chem, acc. 108 (2002) 134-142.

[57] R.G.Pearson, Chemical Hardness, John Wiley-VCH, Weinheim, 1997.

[58] R.G. Parr, L.Von Szentpaly, S.Liu, J.Am, Chem, Soc, 121 (1999) 1922-1924.

[59] J.Padmanabhan, R.Parthasarathi, V.Subramanian, P.K. Chattaraj, J.Phys. Chem, A

111(2007) 1358-1361.

[60] E.D. Glendening, A.E. Reed, J.E. Carpenter, F. Weinhold, NBO Version 3.1, TCI,

University of Wisconsin, Madison, 1998.

[61] H.W. Thomson, P. Torkington, J. Chem. Soc. 171 (1945) 640–645.

[62] A.E.Reed, R.B.Weinstock, F.Weinhold, J.Chem.Phys.83 (1985)735-746.

[63] R.G. Parr, W. Yang, Functional Theory of Atoms and Molecules, Oxford University Press,

New York, 1989.

[64] P.W. Ayers, R.G. Parr, J. Am. Chem. Soc. (2000) 2010–2018.

[65] E. Scrocco, J. Tomasi, Adv. Quant. Chem. 11 (1978) 115.

[66] E.J. Luque, J.M. Lopez, M. Orozco, Theor. Chem. Acc. 103 (2000) 343.

[67] P. Politzer, P.R. Laurence, K. Jayasuriya, Environ. Health Perspect. 61 (1985) 19.

[68] E. Scrocco, J. Tomasi, Top. Curr. Chem. 42 (1973) 95.

[69] R.S. Mulliken, J. Chem. Phys. 23 (1995) 1833–1840.

[70] D.A. Kleinman, J. Phys. Rev. 126 (1962) 1977–1979.

[71] J. Bevan ott, J. Boerio-goates, Chemical Thermodynamics; Principles and Applications Academic Press, San Diego, 2000.



ISSN: 1548-7741

www.joics.org594

Figure 1. Numbering system adopted in the molecular structure of DMPABA.



ISSN: 1548-7741

www.joics.org595

Figure.2. Observed and stimulated FT-IR spectra of 2-(2,3-dimethylphenyl)aminobenzoic acid.



ISSN: 1548-7741

www.joics.org596

Figure.3. Observed and stimulated FT-Raman spectra of 2-(2,3-dimethylphenyl) aminobenzoic

acid.



ISSN: 1548-7741

www.joics.org597

Figure 4 The selected frontier molecular orbitals of 2-(2,3-dimethylphenyl)aminobenzoic acid

with the energy gaps..



ISSN: 1548-7741

www.joics.org598

Figure 5 The calculated TDOS diagrams of 2-(2,3-dimethylphenyl)amino benzoic acid.



ISSN: 1548-7741

www.joics.org599

‘

Figure 6 The calculated PDOS diagrams of 2-(2,3-dimethylphenyl)amino benzoic acid.



ISSN: 1548-7741

www.joics.org600

Figure 7 The calculated OPDOS (or COOP) diagrams of 2-(2,3-dimethylphenyl)amino

benzoic acid.



ISSN: 1548-7741

www.joics.org601

Figure 8 Comparative Mulliken 3D plot by B3LYP/6-31G(d,p) and B3LYP/6-

311++G(d,p) levels of 2-[(2,3-dimethylphenyl)amino]benzoic acid.



ISSN: 1548-7741

www.joics.org602

Figure 9 Electrostatic potential 3D map and 2D contour map for 2-[(2,3

dimethylphenyl)amino]benzoic acid.



ISSN: 1548-7741

www.joics.org603

Figure 10 Correlation graph between Heat Capacity and Temperature in the title compound at

B3LYP/6-311++G(d,p) and B3LYP/6-31G(d,p) method.



ISSN: 1548-7741

www.joics.org604

Figure 11 Correlation graph between Entropy and Temperature in the title compound at




ISSN: 1548-7741

www.joics.org605

Figure 12 Correlation graph between Enthalpy and Temperature in the title compound at




ISSN: 1548-7741

www.joics.org606

Table 1 Geometrical parameters optimized in 2-[(2,3-dimethylphenyl)amino]benzoic acid bond length (A˚ ), bond angle (◦).

Parameters

Bond lengths(Ǻ) Bond angles(0)

B3LYP/

6-311++G(d,p)

B3LYP/

6-31G(d,p)

Expa Parameters

B3LYP/

6-311++G(d,p)

B3LYP/

6-31G(d,p)

Expa

C1-C2 1.48 1.48 1.35 C2-C1-O8 125.5 125.4 125.5

C1-O8 1.21 1.22 1.21 C2-C1-O9 114.9 115.1 114.9

C1-O9 1.38 1.37 1.34 C1-C2-C3 126.1 126.2 126.2

C2-C3 1.43 1.43 1.34 C1-C2-C7 114.5 114.4 114.4

C2-C7 1.41 1.41 1.34 O8-C1-O9 119.6 119.5 119.6

C3-C4 1.41 1.42 1.34 C1-O9-H23 106.2 105.3 105.7

C3-N10 1.38 1.38 1.27 C1-C9-H24 107.2 106.9 107.2

C4-C5 1.38 1.39 1.34 C3-C2-C7 119.3 119.3 119.3

C4-H19 1.08 1.08 1.10 C2-C3-C4 117.4 117.5 117.4

C5-C6 1.40 1.40 1.34 C2-C3-N10 122.4 122.1 122.2

C5-H20 1.09 1.09 1.10 C2-C7-C6 122.2 122.1 122.2

C6-C7 1.38 1.38 1.34 C2-C7-H22 117.1 116.8 116.2



ISSN: 1548-7741

www.joics.org607

C6-H21 1.08 1.09 1.10 C4-C3-N10 120.1 120.4 120.3

C7-H22 1.08 1.08 1.10 C3-C4-C5 121.6 121.5 121.6

O9-H23 0.97 0.97 0.97 C3-C4-H19 118.8 118.7 118.8

N10-C11 1.42 1.42 1.27 C3-N10-C11 127.3 127.8 127.7

N10-H24 1.01 1.01 1.05 C3-N10-H24 115.8 115.3 115.5

C11-C12 1.41 1.41 1.34 C5-C4-H19 119.6 119.7 119.6

C11-C16 1.40 1.40 1.34 C4-C5-C6 121.0 121.0 121.0

C12-C13 1.41 1.41 1.34 C4-C5-H20 118.9 118.9 118.6

C12-C18 1.51 1.51 1.50 C6-C5-H20 120.1 120.1 120.1

C13-C14 1.40 1.40 1.34 C5-C6-C7 118.5 118.5 118.4

C13-C17 1.51 1.51 1.50 C5-C6-H21 120.9 120.9 120.9

C14-C15 1.39 1.39 1.34 C7-C6-H21 120.6 120.6 120.7

C14-H25 1.09 1.09 1.10 C6-C7-C22 120.8 121.0 120.9

C15-C16 1.39 1.39 1.34 H23-O9-H24 146.0 147.6 146.9

C15-H26 1.08 1.09 1.10 C11-N10-H24 116.7 116.4 116.5

C16-H27 1.08 1.08 1.10 N10-C11-C12 119.1 118.7 118.9



ISSN: 1548-7741

www.joics.org608

C17-H28 1.09 1.09 1.11 N10-C11-C16 120.2 120.8 120.6

C17-H29 1.10 1.10 1.11 N10-H24-H9 132.5 133.4 133.2

C17-H30 1.09 1.10 1.11 C12-C11-C16 120.6 120.4 120.4

C18-H31 1.09 1.09 1.11 C11-C12-C13 118.9 119.0 119.0

C18-H32 1.09 1.09 1.11 C11-C12-C18 120.3 120.0 120.3

C18-H33 1.10 1.10 1.11 C11-C16-C15 120.0 120.0 120.1

O9-H24 1.90 1.89 1.89 C11-C16-H27 119.4 119.4 119.4

C13-C2-C18 120.8 121.0 120.8

C12-C13-C14 119.6 119.7 119.6

C12-C13-C17 120.9 120.9 120.9

C12-C18-H31 111.1 111.0 111.1

C12-C18-H32 111.6 111.7 111.6

C12-C18-H33 111.7 112.0 111.7

C14-C13-C17 119.5 119.4 119.5

C13-C14-C15 121.0 120.9 120.9

C13-C14-H25 119.3 119.2 119.3



ISSN: 1548-7741

www.joics.org609

C13-C17-H28 110.7 110.8 10.7

C13-C17-H29 111.8 111.9 111.8

C13-C17-H30 111.8 111.9 111.8

C15-C14-H25 119.7 119.9 119.8

C14-C15-C16 119.9 120.0 119.9

C14-C15-H16 120.2 120.2 120.2

C16-C15-H26 119.9 119.8 119.9

C15-C16-H27 120.6 120.5 120.5

H28-C17-H29 107.6 107.5 107.5

H28-C17-H30 107.8 107.7 107.8

H29-C17-H30 107.0 106.8 107.0

H31-C18-H32 108.0 107.9 107.9

H31-C18-H33 107.4 107.3 107.4

H32-C18-H33 106.8 106.7 106.8

Notes: Bond lengths are in Ǻ, bond angles are in degrees. a X ray data taken from Ref. Mihaela M Pop, et al., 2002.



ISSN: 1548-7741

www.joics.org610

Table 2 Definition of internal coordinates of 2-[(2,3-dimethylphenyl)amino]benzoic acid.

No(i) Symbol Type Definitiona

Stretching

1-15 Ri C-C C1-C2,C2-C3,C2-C7,C3-C4,C4-C5,C5-C6,C6-C7,C11-C12,C11-C16,C12-C13,C12-C18,C13-C14,C13-C17,C14-C15,

C15-C16

16-18 Ri C-H C4-H19,C5-H20,C6-H21,C7-H22,C14-H25,C15-H26,C16-H27,C17-H28,C17-H29,C17-H30,C18-H31,C18-H32,C18-H33

29-30 Ri C-O C1-O8,C1-O9

31 Ri C-N C3-N10

32-33 Ri O-H O9-H23,O9-H24

34 Ri N-C C10-C11

35 Ri N-H N10-H24

In-plane bending

36-41 γi Ring1 C3-C2-C7,C2-C3-C4,C2-C7-C6,C3-C4-C5,C4-C5-C6,C5-C6-C7

42-47 γi Ring2 C12-C11-C16,C11-C12-C13,C11-C16-C15,C12-C13-C14,C13-C14-C15,C14-C15-C16

48-66 γi C-C-H C2-C7-H22,C3-C4-C19,C5-C4-H19,C4-C5-H20,C6-C5-H20,C5-C6-H21,C7-C6-H21,C6-C7-H22,C11-C16-H27,

C12-C18-H31,C12-C18-H32,C12-C18-H33,C13-C14-H25,C13-C17-H28,C13-C17-H29,C13-C17-H30,C15-C14-H25,

C16-C15-H26,C15-C16-H27

67-68 γi C-C-O C2-C1-O8,C2-C1-O9

69 γi O-C-O O8-C1-O9

70-71 γi C-O-H C1-O9-H23,C1-O9-H24

72-73 γi C-C-C C1-C2-C3,C1-C2-C7

74-77 γi C-C-N C2-C3-N10,C4-C3-N10,N10-C11-C12,N10-C11-C16

78 γi C-N-C C3-N10-C11

79-80 γi C-N-H C3-N10-H24,C11-N10-H24

Out-of-plane bending

81-87 ρi H-C-C H22-C7-C6-C2,H21-C6-C5-C7,H20-C5-C4-C6,H19-C4-C3-C8,H25-C14-C13-C15,H26-C15-C14-C16,

H27-C16-C15-C11

88 ρi O-C-O C2-C1-O8-O9

89-90 ρi C-H-H C18-H33-H32-H31,C17-H29-H30-H28

91 ρi H-N-C H24-N10-C3-C11

Torsion

92-95 τi Ring1 C2-C1-C4-C5,C3-C4-C5-C6,C4-C5-C6-C7,C5-C6-C7-C2,C6-C7-C2-C3,C7-C2-C3-C4

96-100 τi Ring2 C11-C12-C13-C14,C12-C13-C14-15,C13-C14-C15-C16,C14-C15-C16-C11,C15-C16-C11-C12,C16-C11-C12-C13

101-102 τi C-N-C C3-N10-C11-C12,C3-N10-C11-C12

103-104 τi CH3 C17-H28-H29-H30,C18-H31-H32-H33



ISSN: 1548-7741

www.joics.org611

105-106 τi C-C-N C2-C3-N10-C11,C4-C3-N10-C11

107 τi H-N-C H24-N10-C11-C12

108 τi C-CO2 C2-C1-O8-O9

aFor numbering of atom refer Fig. 1.



ISSN: 1548-7741

www.joics.org612

Table 3 Definition of local symmetry coordinates of 2-[(2,3-dimethylphenyl)amino]benzoic acid.

No.(i) Symbola Definitionb

1-15 ν CC R1,R2,R3,R4,R5,R6,R7,R8,R9,R10,R11,R12,R13,R14,R15

16-28 ν CH R16,R17,R18,R19,R20,R21,R22,R23,R24,R25,R26,R27,R28

29-30 ν (CO2ss) R29+R30/√2,R31+R32/√2

31 ν CN R33

32-33 ν OH R34,R35

34 ν NC R36

35 ν NH R37

36 β trig1 (γ38-γ39+γ40-γ41+γ42-γ43)/ √6

37 β asym1 (-γ38-γ39+2γ40-γ41-γ42-2γ43)/ √12

38 β sym1 (γ38-γ39+γ41-γ42)/ √2

39 β trig2 (γ44-γ45+γ46-γ47+γ48-γ49)/ √6

40 β asym1 (-γ44-γ45+2γ46-γ47-γ48-2γ49)/ √12

41 β sym1 (γ44-γ45+γ47-γ48)/ √2

42-51 β CCH (γ50-γ51)/ √2, (γ52-γ53)/ √2, (γ54-γ55)/ √2, (γ56-γ57)/ √2, (γ58-γ59)/ √2, (γ60-γ61)/ √2,

(γ62-γ63)/ √2, (γ64-γ65)/ √2, (γ66-γ67)/ √2, (γ68-γ69)/ √2

52-54 β CCO (γ70-γ71)/ √2, (γ72-γ73)/ √2, (γ74-γ75)/ √2, (γ76-γ77)/ √2

55 β CO2rock (γ78-γ79)/ √2

56 β CO2sic (2γ80-γ81-γ82/ √6)

57 ω CCC ρ 83, ρ 84

58-61 ω CCN ω85, ω86, ω87, ω88

62 ω CNC ω89

63-65 ω CNH ω90, ω91, ω92



ISSN: 1548-7741

www.joics.org613

Abbreviations: ν, stretching; β, in plane bending; ω, out of plane bending; τ, torsion.

aThese symbols are used for description of the normal modes by PED in Table 4.

bThe internal coordinates used here are defined in table given in Table 2.

Table 4 The experimental FT-IR, FT-Raman and calculated frequencies using B3LYP/6.31G(p,d),B3LYP/6-311++G(d,p) force

field along with their relative intensities, probable assignments and potential energy distribution (PED) of 2-[(2,3-

dimethylphenyl)amino]benzoic acid.

Modes

Experimental

Wave numbers (cm-1) Calculated frequencies(cm)

Assignments(PED)a

FT-IR FT-Raman

B3LYP/

6-31G(d,p)

B3LYP/

6-311++G(d,p)

Unscaled Scaled Unscaled Scaled

1 3640(s) 3641(w) 3764 3636 3765 3640 ν OH (100)

2 - 3470(vw) 3596 3474 3597 3478 ν OH (100)

3 - - 3208 3099 3206 3100 ν CH3(99)

4 - 3091(m) 3204 3095 3203 3097 ν CH3(98)

5 - - 3193 3084 3192 3087 ν CH3(95)

6 - - 3188 3080 3188 3083 ν CH3(90)

7 - - 3177 3069 3176 3071 ν CH3(89)

8 - - 3166 3058 3166 3062 ν CH3(85)

9 - - 3160 3053 3161 3057 ν CH3(80)

10 - - 3118 3012 3117 3014 ν CH3(75)

11 3000(vs) 3003(w) 3105 2999 3104 3002 ν CH3(66)

12 2993(m) - 3081 2976 3081 2979 ν CH3(54)

13 - - 3066 2962 3066 2965 ν CH(96)

14 - - 3021 2918 3020 2920 ν CH(96)



ISSN: 1548-7741

www.joics.org614

15 - - 3011 2909 3010 2911 ν CH(96)

16 1725(ms) - 1788 1727 1769 1711 C=O(85)

17 1598(ms) - 1652 1596 1648 1594 ν CC(73),ν COO(12)

18 - - 1641 1585 1637 1583 ν CC(70),ν COO(12)

19 - - 1623 1568 1620 1567 β CCH(32),ν CC(26)

20 - - 1622 1567 1617 1564 ν CC(18),ν CCC(16)

21 - - 1559 1506 1554 1503 NH3ass(70)

22 - - 1513 1462 1512 1462 ν CC(90),ν CH(18),ν CO(10)

23 - - 1507 1456 1506 1456 ν CC(85),ν CH(15),ν CO(10)

24 - - 1502 1451 1499 1450 ν CC(80),ν CH(12),ν CO(10)

25 - - 1499 1448 1496 1447 ν CC(75),ν CH(10),ν CO(10)

26 - 1442(w) 1493 1442 1491 1442 δ CC(70),δ CH(08),δ CO(10)

27 1430(s) - 1483 1433 1481 1432 δ CC(65),δ CO(18),δ CH(10)

28 - - 1478 1428 1476 1427 ν CC(40),β CCO(18),β CCC(18),

29 - - 1455 1405 1453 1405 β CCO(15),ν CC(35),β CCH(23)

30 - 1377(s) 1421 1373 1420 1373 δ C-O(65),ν OH(18),ν CC(14)

31 - - 1412 1364 1410 1363 ν CC(75),ν CO(16),ν CH(10)

32 - - 1371 1324 1366 1321 ν CC(69),ν CO(18),ν CH(10)

33 1300(vs) - 1347 1301 1345 1301 ν CC(65),ν CO(15),ν CH(10)

34 1280(vs) 1282(vw) 1320 1275 1319 1275 ν CC(75),ν CO(15),ν CH(10)

35 - - 1309 1264 1306 1263 ν CO2(22),ν CC(21),β CCH(14),ν HOC(10)

36 - - 1304 1259 1299 1256 ν CC(49),β CCC(17),β CCH(11),β CCO(10)

37 - - 1273 1230 1272 1230 β CCH(23),ν CC(21),ν C0(11)

38 - - 1253 1210 1252 1211 ν CC(17),β CO(27),β CCH(13),ν CO(10)

39 1170(vs) - 1205 1164 1204 1164 δ CH(60),γ OH(22),γ CC(11)

40 - - 1200 1159 1198 1158 CH3ss(54),ν CO(15),ν CH(10)

41 - - 1194 1153 1193 1154 CH3iop (64),ν CO(15),ν CH(10)

42 1142(vs) - 1187 1146 1185 1146 CH3opd (74),ν CO(15),ν CH(10)

43 1090(vs) 1090(vw) 1127 1089 1125 1088 γ CH(40),γ OH(20),γ CC(11)

44 1074(vs) 1070(vw) 1112 1074 1110 1073 γ CH(73),γ CC(18)

45 - - 1095 1057 1090 1054 γ CH(63),γ CC(18)

46 - - 1085 1048 1083 1047 γ CH(53),γ CC(18)



ISSN: 1548-7741

www.joics.org615

47 - - 1067 1031 1066 1031 γ CH(43),γ CC(18)

48 - - 1056 1020 1051 1016 γ CH(33),γ CC(18)

49 - 1000(vs) 1041 1006 1040 1006 δ C-O(75),ν CC(12),ν CH(08)

50 - - 1010 976 1009 976 γ CH(70),δ CC(37),ν CO(13)

51 - - 997 963 998 965 γ CH(60),δ CC(27),ν CO(13)

52 - - 987 953 988 955 γ CH(50),δ CC(17),ν O(13)

53 945(w) 945(vw) 976 943 981 949 γ CH(45),δ CC(17),ν CO(13)

54 905(s) - 936 904 934 903 γ CH(40),δ CC(17),ν CO(13)

55 - - 911 880 914 884 δ CC(68),δ CO(12),δ CH(08)

56 - - 876 846 874 845 δ CC(58),δ CO(22),δ CH(18)

57 829(s) - 857 828 856 828 γ CH(32),γ CO(18),τ CH3(10)

58 - - 824 796 824 797 γ CH(68),γ CO(12),τ CH3(12)

59 - - 805 778 805 778 γ CH(75),γ CH3(15),γ CC(13)

60 - 770(vs) 804 777 804 777 γ CH(65),γ CH3(15),γ CC(13)

61 750(vs) - 776 750 774 748 γ CH(55),γ CH3(15),γ CC(13)

62 - - 763 737 761 736 γ CH(45),γ CH3(15),γ CC(13)

63 - - 739 714 737 713 γ CC(65),γ CH(12),γ CO(10)

64 - - 721 696 719 695 CH3ipr(40),ν CO(15),ν CH(10)

65 - - 715 691 712 689 CH3opr(45),ν CC(15),ν CH(10)

66 - 620(s) 642 620 640 619 γ OH(34),ν CO(15),ν COOH(10)

67 600(vw) - 629 608 628 607 CH3ipr(54),ν CC(15),ν CH(10)

68 - - 589 569 587 568 CH3ipr(30),ν CH(20),ν CO(15)

69 - - 585 565 570 551 CH3opr(20),δ CH(20),δ COO(15)

70 545(ms) - 557 538 552 534 γ OH(67), γ CC(15),γ COOH(10)

71 - - 541 523 530 513 δ CC(45),δ CH(12),δ CO(10)

72 - 510(vw) 528 510 525 508 CH3ipr(48),ν CC(18),ν CH(10)

73 - - 520 502 515 498 CH3ipr(45),ν CC(15),ν CH(10)

74 - - 514 497 513 496 CH3ipr(40),ν CC(15),ν CH(10)

75 - - 499 482 499 483 CH3opr(35),ν CC(15),ν CH(10)

76 - - 471 455 472 456 CH3opr(30),ν CC(15),ν CH(10)

77 - 414(vw) 434 419 432 418 CH3opr(45),ν CC(15),ν CH(10)

78 - - 392 379 390 377 γ CC(42),γ CH(18),γ CO(12)



ISSN: 1548-7741

www.joics.org616

79 - 342(w) 356 344 356 344 γ CC(64),γ CO(12),γ CH(8)

80 - - 324 313 324 313 γ CC(45),τ CH3(12)

81 - 285(vw) 299 289 298 288 γ CC(54),γ CH(18),γ CO(12)

82 - - 275 266 274 265 γ CCO(42),γ COC(24),γ CCO(15)

83 - - 245 237 243 235 γ CC(40),γ COC(46),γ CCC(13)

84 - - 223 215 221 214 γ CCC(31),γ COC(36),γ CCC(13)

85 - - 189 183 187 181 δ CC(46),γ OH(22)

86 - - 165 159 166 161 γ COC(27),ν CCC(32),γ CO2(27)

87 - 135(s) 140 135 140 135 δ CC(65),γ CH(12)

88 120(w) - 128 124 126 122 δ C-O(75),γ CC(12),γ CH(08)

89 - - 85 82 98 95 δ CO(26),γ CCC(23)

90 - 65(vw) 68 66 68 66 δ O(52),γ OH(18),γ CO(12)

91 - - 60 58 55 53 δ C-O(75),γ CC(12),ν CH(08)

92 - 30(vs) 32 31 32 31 δ C-O(38),ν OH(18),τ CH3(10)

93 - 22(s) 26 25 23 22 τ CH3(75)

ν – stretching, δ – in plane, γ – out-plane, w – weak, m – medium, vw – very weak, s – strong, vs – very strong, ass – asymmetric

stretching, ss – symmetric stretching, ipb,β – in –plane bending, opb – out-of-plane bending, ipr – in-plane rocking, opr – out-of-plane

rocking, τ – torsion. aOnly PED contributions≥10% are listed.



ISSN: 1548-7741

www.joics.org617

Table 5 The ab initio B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p) calculated electric

dipole moments (Debye), Dipole moments compound, polarizability (in a.u) ,β components and

βtot (10-30 esu) value of 2-[(2,3-dimethylphenyl)amino]benzoic acid.

Parameters B3LYP/

6-31G(d,p)

B3LYP/

6-311++G(d,p)

µx 2.8858 3.2049

µy -0.2035 -0.0441

µz 0.4001 0.5509

µ 2.9205 3.2522

αxx -110.2431 -112.3185

αyy -95.1216 -96.7523

αzz -107.4862 -108.3726

α -91.6319 -95.1069

βxxx 63.0356 74.0324

βyyy -36.8750 -35.9070

βzzz -6.1133 -5.4846

βxyy -10.3416 -8.8117

βxxy 29.2654 31.9790

βxxz 15.5342 18.5339

βxzz -2.0657 -0.0537

βyzz -8.0808 -6.8662

βyyz -6.5401 -5.8714

β0(esu) 1.408910-30 2.205310-30



ISSN: 1548-7741

www.joics.org618

Table 6 Second –order perturbation theory analysis of Fock matrix in NBO basis corresponding to the intramolecular of

the title compound.

Donor NBO(i) EDa(i)/e Acceptor NBO(j) EDa(j)/e E(2)b

(kcalmol-1) E(j)-E(i)c(a.u) F(i,j)d(a.u)

σ (C1-C2) 1.97445 σ*(C1-O8) 0.00321 1.71 1.23 0.041

σ(C1-O8) 1.99366 σ*(C1-C2) 0.00652 2.2 1.45 0.051

σ(C1-O9) 1.99599 σ*(C1-O8) 0.00321 0.86 1.19 0.031

σ(C2-C3) 1.96898 σ*(C2-O7) 0.00028 4.57 1.23 0.067

σ(C2-C7) 1.96504 σ*(C3-C4) 0.00172 2.29 1.17 0.046

σ(C3-C4) 1.97444 σ*(C3-N10) 0.00311 51.05 1.71 0.264

σ(C3-N10) 1.98819 σ*(C6-C7) 0.00025 3.21 0.68 0.042

σ(C4-C5) 1.97678 σ*(C4-H19) 0.00011 1.04 1.14 0.031

σ(C4-H19) 1.97616 σ*(N10-C11) 0.00008 0.62 0.82 0.02

σ(C5-C6) 1.98047 σ* (C11-C16) 0.00004 1.67 0.53 0.027

σ(C5-H20) 1.98041 σ* (C4-C5) 0.00045 0.7 1.06 0.024

σ(C6-C7) 1.97676 σ*(C11-C16) 0.00004 1.88 0.53 0.028

σ(C6-H21) 1.98035 σ*(C16-H27) 0.00004 4.67 0.16 0.025

σ(C7-H22) 1.97663 σ* (C18-H32) 0.00003 1.44 1.58 0.043

σ(O9-H23) 1.98605 σ*(C11-C16) 0.00004 30.67 0.6 0.121

σ(N10-C11) 1.9887 σ*(C12-H30) 0.00002 12.96 3.12 0.18

σ(N10-H24) 1.97901 σ*(C11-C16) 0.00004 111.92 0.2 0.15

σ(C11-C12) 1.96814 σ*(C6-C7) 0.00013 129.4 0.58 0.245

σ(C11-C16) 1.97142 σ*(C17-H30) 0.00002 9.58 3.04 0.153



ISSN: 1548-7741

www.joics.org619

Table 7 Accumulation of natural charges and electron population of atoms in core, valance, Rydberg orbitals of

2-[(2,3-dimethylphenyl)amino]benzoic acid.

Atomsa Charge(e) Natural population(e)

Total(e) Atomsb Charge(e) Natural population(e)

Total(e) Core Valence Rydberg Core Valence Rydberg

C1 0.78358 1.99934 3.17029 0.04679 0.04679 C2 -0.21016 1.99872 4.19403 0.01742 6.21016

C3 0.21773 1.99893 3.76467 0.01867 5.78227 C4 -0.25166 1.99907 4.23599 0.0166 6.25166

C11 0.18654 1.99869 3.79381 0.02096 5.81346 C5 -0.15159 1.99913 4.13518 0.01728 6.15159

H19 0.20898 0.00000 0.78853 0.00249 0.79102 C6 -0.25279 1.99916 4.23316 0.02048 6.25279

H20 0.20953 0.00000 0.78877 0.00171 0.79047 C7 -0.11496 1.99889 4.09883 0.01725 6.11496

H21 0.21200 0.00000 0.78618 0.00182 0.78800 O8 -0.62782 1.99976 6.6144 0.01366 8.62782

H22 0.23995 0.00000 0.75785 0.00220 0.76005 O9 -0.70995 1.99972 6.69736 0.01288 8.70995

H23 0.50614 0.00000 0.48892 0.00494 0.49386 N10 -0.61244 1.99925 5.59549 0.01770 7.61244

H24 0.41859 0.00000 0.57662 0.00478 0.58141 C12 -0.06895 1.99893 4.05434 0.01568 6.06895

H25 0.20169 0.00000 0.79631 0.00200 0.79831 C13 -0.02800 1.99897 4.01390 0.01513 6.02800

H26 0.20607 0.00000 0.79208 0.00185 0.79393 C14 -0.21848 1.99913 4.20128 0.01818 6.21848

H27 0.20003 0.00000 0.79743 0.00254 0.79997 C15 -0.18598 1.99913 4.16874 0.01628 6.18598

H28 0.20951 0.00000 0.78842 0.00207 0.79049 C16 -0.24623 1.99909 4.23086 0.01628 6.24623

H29 0.20918 0.00000 0.78847 0.00234 0.79082 C17 -0.58382 1.99920 4.57509 0.00953 6.58382

H30 0.20918 0.00000 0.78847 0.00234 0.79082 C18 -0.58722 1.99930 4.57969 0.00823 6.58722

H31 0.20645 0.00000 0.79151 0.00203 0.79355

H32 0.21252 0.00000 0.78553 0.00195 0.78748

H33 0.21251 0.00000 0.78553 0.00195 0.78749

a Atoms containing negative charges. b Atoms containing positive charges.



ISSN: 1548-7741

www.joics.org620

Table 8 Comparison of HOMO, LUMO energy gaps and related molecular properties of 2-[(2,3-dimethylphenyl)amino]benzoic

acid at B3LYP/6-31G(d,p) and B3LYP/6-311++G(d,p) level of theory.

Molecular Properties Energy

(a.u)

Energy gap

(eV)

Ionization

potential

(I)

Electron

affinity

(A)

Global

hardness

(ƞ)

Electro

negativity

(χ)

Global

softness

(σ)

Chemical

potential

(μ)

Global

electrophilicity

(ω)

B3LYP/6-31G(d,p)

HOMO -0.2044 0.1537 0.2044 0.0507 0.0768 0.1275 13.0070 -0.1275 0.1053

LUMO -0.0507

HOMO -0.2044 0.1854 0.2044 0.0189 0.0927 0.1168 10.7870 -0.1116 0.0668

LUMO+1 -0.0189

HOMO -0.2044 0.1930 0.2044 0.0114 0.0965 0.1280 10.3590 -0.1280 0.0844

LUMO+2 -0.0114

B3LYP/6-311++G(d,p)

HOMO -0.2094 0.1507 0.2094 0.0587 0.0753 0.1340 13.2661 -0.1340 0.1187

LUMO -0.0587

HOMO -0.2094 0.1827 0.2094 0.0267 0.0913 0.1504 10.9469 -0.1504 0.1237

LUMO+1 -0.0267

HOMO -0.2094 0.1909 0.2094 0.0184 0.0954 0.1524 10.4723 -0.1524 0.1215

LUMO+2 -0.0184



ISSN: 1548-7741

www.joics.org621

Table 9 Using Mulliken population analysis: Fukui functions (

kf ,

kf , 0

kf ) for atoms of

2-[(2,3-dimethylphenyl)amino]benzoic acid.

Atoms

Mulliken atomic charges Fukui functions

qN+1 qN qN-1

C1 0.3799 0.7836 0.6658 -0.4037 0.1177 -0.1430

C2 -0.0182 -0.2102 -0.2623 0.1920 0.0521 0.1220

C3 0.0675 0.2177 0.1457 -0.1502 0.0721 -0.0391

C4 -0.0258 -0.2517 -0.2740 0.2259 0.0223 0.1241

C5 -0.1049 -0.1516 -0.3125 0.0467 0.1609 0.1038

C6 0.0074 -0.2528 -0.2567 0.2602 0.0039 0.1320

C7 -0.0769 -0.1150 -0.2094 0.0380 0.0945 0.0663

O8 -0.0268 -0.6278 -0.7537 0.6010 0.1258 0.3634

O9 -0.3572 -0.7100 -0.7631 0.3528 0.0532 0.2030

N10 -0.0220 -0.6124 -0.3458 0.5905 -0.2667 0.1619

C11 0.1057 0.1865 0.1738 -0.0809 0.0127 -0.0341

C12 0.0687 -0.0690 -0.1693 0.1376 0.1003 0.1190

C13 -0.0428 -0.0280 -0.0760 -0.0148 0.0480 0.0166

C14 0.0500 -0.2185 -0.2772 0.2685 0.0587 0.1636

C15 -0.1011 -0.1860 -0.1958 0.0849 0.0098 0.0474

C16 -0.0416 -0.2462 -0.2865 0.2046 0.0402 0.1224

C17 -0.2971 -0.5838 -0.5926 0.2867 0.0088 0.1478



ISSN: 1548-7741

www.joics.org622

C18 -0.3021 -0.5872 -0.8683 0.2851 0.2811 0.2831

H19 0.1083 0.2090 0.1802 -0.1007 0.0287 -0.0360

H20 0.1189 0.2095 0.1761 -0.0906 0.0334 -0.0286

H21 0.1166 0.2120 0.1796 -0.0954 0.0324 -0.0315

H22 0.1327 0.2400 0.2182 -0.1073 0.0218 -0.0428

H23 0.2624 0.5061 0.4685 -0.2437 0.0376 -0.1031

H24 0.2168 0.4186 0.4002 -0.2018 0.0184 -0.0917

H25 0.1110 0.2017 0.1818 -0.0907 0.0199 -0.0354

H26 0.1176 0.2061 0.1891 -0.0885 0.0170 -0.0357

H27 0.1063 0.2000 0.2042 -0.0938 -0.0042 -0.0490

H28 0.1137 0.2095 0.1946 -0.0958 0.0149 -0.0405

H29 0.1128 0.2092 0.1939 -0.0964 0.0152 -0.0406

H30 0.1128 0.2092 0.1945 -0.0964 0.0147 -0.0409

H31 0.1042 0.2065 0.1747 -0.1023 0.0318 -0.0352

H32 0.1222 0.2125 0.1640 -0.0903 0.0485 -0.0209

H33 0.1222 0.2125 0.1624 -0.0904 0.0501 -0.0201



ISSN: 1548-7741

www.joics.org623

Table 10 Mulliken’s atomic charge of 2-[(2,3-dimethylphenyl)amino]benzoic acid at

B3LYP/6-311G++(d,p) ,6-31G(d,p)

Atom

No.

Atomic charges(e)

B3LYP/

6-311G++(d,p)

B3LYP/

6-31G(d,p)

C1 -0.8620 0.4620

C2 0.0904 -0.2512

C3 -0.3949 0.2589

C4 0.0643 -0.1246

C5 -0.3511 -0.0776

C6 -0.4199 -0.1011

C7 0.0788 -0.0332

O8 -0.2932 -0.3407

O9 -0.3142 -0.3868

N10 0.1189 -0.5447

C11 -0.2529 0.1348

C12 0.5787 -0.0845

C13 0.3349 -0.1029

C14 -0.5872 -0.0631

C15 -0.4022 -0.0901

C16 0.2068 -0.0671

C17 -0.6265 -0.2671

C18 -0.6443 -0.2626

H19 0.1749 0.1237

H20 0.1710 0.0967

H21 0.1656 0.0928

H22 0.2218 0.1103

H23 0.3399 0.2630

H24 0.3895 0.2542

H25 0.1107 0.0793

H26 0.1690 0.0918

H27 0.1793 0.1114

H28 0.1447 0.1071

H29 0.1581 0.1255

H30 0.1597 0.1221

H31 0.1950 0.1214

H32 0.1411 0.1170

H33 0.1785 0.1249



ISSN: 1548-7741

www.joics.org624

Table 11 Thermodynamic function of 2-[(2,3-dimethylphenyl)amino]benzoic acid at

B3LYP/ 6-311++G(d,p) and B3LYP/6-31G(d,p) methods.

Temperature(K)

Thermodynamic parameter

B3LYP/6-311++G(d,p) B3LYP/6-31G(d,p)

S Cp (G-E)/T S Cp (G-E)/T

100 356.44 113.59 7.44 355.66 113.45 7.43

200 458.53 191.37 22.61 457.48 190.76 22.56

298.15 550.15 273.15 45.4 548.83 272.48 45.29

300 551.85 274.68 45.91 550.52 274.48 45.79

400 641.87 353.39 77.39 640.36 352.74 77.21

500 728.17 420.42 116.19 726.51 419.8 115.94

600 809.83 475.04 161.06 808.06 474.48 160.75

700 886.5 519.4 210.85 884.65 518.89 210.5

800 958.31 555.86 264.67 956.4 555.89 264.27

900 1025.59 586.28 321.82 1023.63 585.89 321.38

1000 1088.73 611.94 381.77 1086.73 611.6 381.29



ISSN: 1548-7741

www.joics.org625

Documents

Spectroscopic (FT-IR, FT-Raman, UV vis), Fukui function ...joics.org/gallery/ics-1274.pdf · linear optical effect [4]. In the recent years, amino acid complexes have received much