Synthesis, Characterization, Spectral (FT-IR, 1H, 13C NMR, Mass and UV) and Biological Aspects of the Coordination Complexes of Sulfur Donor Ligands with Some Rare Earth Elements

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*Corresponding author: Email: [email protected];

American Chemical Science Journal4(1): 117-137, 2014

SCIENCEDOMAIN internationalwww.sciencedomain.org

Synthesis, Characterization, Spectral (FT-IR, 1H,13C NMR, Mass and UV) and Biological Aspectsof the Coordination Complexes of Sulfur Donor

Ligands with Some Rare Earth Elements

R. V. Singh1*, Pradeep Mitharwal1, Ritu Singh1 and S. P. Mital2

1Department of Chemistry, University of Rajasthan, Jaipur, 302 004, India.2Department of Chemistry, D.A.V. P.G. College, Dehradun-248001, India.

Authors’ contributions

This work was carried out in collaboration between all authors. Author RVS designed thestudy, performed the statistical analysis, wrote the protocol, and wrote the first draft of the

manuscript. Authors PM and RS managed the analyses of the study. Author SPM managedthe literature searches. All authors read and approved the final manuscript.

Received 17th September 2013Accepted 16th October 2013

Published 9th November 2013

ABSTRACT

Bio-potent ligands, 2-hydroxy-N-phenylbenzamide hydrazinecarbothioamide(HPHTSCZH2)and 2-hydroxy-N-phenylbenzamide hydrazine carbodithioic benzyl ester (HPHCBESH2)have been synthesized by the condensation of 2-hydroxy-N-phenylbenzamide withhydrazinecarbothioamide and hydrazine carbodithioic benzyl ester, respectively andreacted with hydrated lanthanide chlorides. The coordination moieties of the ligands havebeen confirmed by various spectral studies. Elemental analyses suggested that thecomplexes have 1:2 stoichiometry which were characterized further by magnetic moment,infrared, EPR, electronic, 1H NMR, 13C NMR and mass spectral studies. TGA studies werealso conducted for one of the representative compound to analyze the presence of watermolecule. The spectral studies confirmed the proposed framework of the new lanthanidecomplexes and indicated an octahedral geometry around the central metal atom. On thebasis of X-ray powder diffraction study one of the representative Sm complex was foundto have Hexagonal Lattice type, having Lattice Parameters: a = 18.528 Aº, b = 18.528 Aºand c = 20.675 Aº and α = 90º, β = 90º and γ =120º. The free ligands and their metal

Original Research Article

American Chemical Science Journal, 4(1): 117-137, 2014

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complexes have been tested in vitro against a number of microorganisms in order toassess their antimicrobial properties and in vivo for antifertility activity on male albino rats.Both the ligands and their complexes were found to possess appreciable fungicidal,bactericidal and antifertility activities.

Keywords: Rare earth elements; thiosemicarbazone; hydrazine carbodithioic acid; 2-hydroxy-N-phenylbenzamide; microorganisms; antifertility activity; TGA; spectralstudies.

1. INTRODUCTION

Nowadays, the complexes of the rare earth ions are a subject of increasing interest inbioinorganic and coordination chemistry [1]. A sustained research activity has been devotedto lanthanide complexes, because of their successful application in the form of diagnostictools in biomedical analysis as MRI contrast agents [2,3]. The coordination chemistry oflanthanide elements and important role of their complexes in chemical, medical andindustrial processes are enough to recognize them as worthwhile for the synthesis of thenew complexes. Apart from the structural diversities and bonding interactions, the multitudeapplications of lanthanide complexes make it an exciting arena in coordination chemistry[4,5]. Imines are important class of ligands due to their synthetic flexibility, their selectivityand sensitivity towards the central metal atom, structural similarities with natural biologicalsubstances and also due to the presence of the imine group (>C=N) which imparts inelucidating the mechanism of transformation and racemisation reaction in biological system[6].

The chemistry of thiosemicarbazones has received considerable attention in view of theirvariable bonding modes, promising biological implications, structural diversity, and ion-sensing ability [7-8]. They have been used as drugs and are reported to possess a widevariety of biological activities against bacteria, fungi, and certain type of tumors and they arealso a useful model for bioinorganic processes [9,10]. Metal complexes of imines derivedfrom S-alkyl/aryl esters of dithiocarbazoic acid [11] have received considerable attentionbecause of the presence of both hard nitrogen and soft sulfur donor atoms in the backbonesof these ligands. It is well known that lanthanide ions have high affinity to hard donor atoms,and thus ligands containing oxygen or nitrogen atoms have been extensively used in thesynthesis of lanthanide complexes [12].

Recently, there has been a growing interest in the lanthanide imines complexes owing to theimportant applications of both metals and ligands. Hirayama, et al. [13] extracted the trivalentlanthanide selectively as anionic imine complexes. Bastida, et al. [14] studied the lanthanidecomplexes with macrocyclic Schiff base ligands and obtained complexes of 18 and 15-membered macrocycles. Exhibiting a broad spectrum of biological activities and outstandingoptical properties, complexes of rare-earth metals with imines derived from amino acidsattract a great interest of researchers in recent years [15].

Keeping all these facts under consideration, during the present investigations we havesynthesized, characterized and screened the biologically potent ligands and their lanthanidecomplexes against a variety of pathogenic fungal and bacterial strains. Further, thecomplexes were also tested for their antifertility activity in male albino rats and the resultswere indeed positive.


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2. EXPERIMENTAL

The hydrated lanthanide chlorides as well as 2-hydroxy-N-phenylbenzamide were purchasedfrom Alfa Aesar and used as such. All the chemicals and solvents used were of analyticalgrade. Hydrazine carbodithioic acid was prepared in the laboratory by the literature method[16]. All the solvents were dried and distilled before use. The metal contents were estimatedcomplexometrically with EDTA using Erichrome Black T as an indicator. Sulfur and nitrogenwere estimated by the Messenger’s and Kjeldahl’s method, respectively. IR spectra wererecorded on a Perkin-Elmer model 577 grating spectrophotometer, in the range 4000–200cm-1 in KBr discs. 1H NMR and 13C NMR spectra were recorded on a JEOL-AL-300 FT NMRspectrometer in DMSO-d6 using TMS as the internal standard. EPR spectra of thecomplexes were monitored on Varian E- 4X band spectrometer. The electronic spectra wererecorded on a Varian–Cary/5E spectrophotometer and mass spectra were recorded onJEOL GCmate spectrometer. Molecular weight determinations were carried out by the RastCamphor Method. Magnetic susceptibility measurements were made at room temperaturewith the Faraday balance using Hg[Co(NCS)4] as calibrant.

2.1 Synthesis of the Ligands

Both of the ligands, 2-hydroxy-N-phenylbenzamide hydrazinecarbothioamide (HPHTSCZH2)and hydroxy-N-phenyl benzamide hydrazine carbodithioic benzyl ester (HPHCBESH2) wereprepared as reported in the literature [17]. Their physical properties and analytical data aregiven in Table 1. Synthetic route and structures of the ligands are given in Fig. 1.

C OHN

OH

NH

H2N CNH2

S

NH

H2N CSCH2C6H5

S

C NHN

OH

NH

CNH2

S

HPHTSCZH2

C NHN

OH

NH

CSCH2C6H5

S

HPHCBESH2

Ethanol, H2O

Ethanol, H2O

Fig. 1. Synthesis and structures of the ligands


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Table 1. Analytical data and physical properties of the ligands and their complexes

Compound Colour Meltingpoint (ºC)

Found (Calcd.) (%) µeff(B.M)

Mol. wt.found(Calcd.)

Yield (%)N S Ln

HPHTSCZH2 Light pink 124 19.51(19.57)

11.13(11.20)

- - 267.46(286.35)

80

HPHCBESH2 Grey 133 10.56(10.68)

16.34(16.30)

- - 407.70(393.53)

82

[La(HPHTSCZH)(HPHTSCZ)].3H2O Black 210-218 14.39(14.63)

7.67(7.96)

19.34(18.14)

.00 751.01(762.63)

72

[Pr(HPHTSCZH)(HPHTSCZ)].3H2O Dirty yellow 160-165 14.43(14.59)

8.52(8.35)

17.22(18.35)

3.53 747.98(764.62)

74

[Nd(HPHTSCZH)(HPHTSCZ)].3H2O Sandy brown 178-180 11.65(11.76)

6.69(6.70)

14.99(15.50)

3.47 779.06(767.96)

76

[Sm(HPHTSCZH)(HPHTSCZ)].3H2O Sandy brown 140-142 14.23(14.47)

8.12(8.28)

18.35(19.42)

1.44 768.56(774.07)

70

[La(HPHCBESH)(HPHCBES)].3H2O Light brown 150-158d 8.78(8.85)

13.42(13.51)

13.87(14.63)

.00 967.53(948.93)

75

[Pr(HPHCBESH)( HPHCBES)].3H2O Brown 230-240d 8.96(8.83)

13.60(13.48)

13.99(14.81)

3.71 932.86(950.93)

71

[Nd(HPHCBESH)( HPHCBES).3H2O Grey 90-100 8.57(8.80)

13.34(13.44)

14.98(15.11)

3.62 947.49(954.26)

68

[Sm(HPHCBESH)(HPHCBES)].3H2O Chocolatebrown

100-110 8.81(8.75)

13.42(13.35)

14.79(15.65)

1.52 956.14(960.37)

71


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2.2 Synthesis of the Sodium Salt of the Ligands

Sodium metal was taken corresponding to the weight of the ligand in 2:1 molar ratios. Nowboth the sodium metal and ligand were dissolved in minimum amount of methanolseparately. Ultimately these two solutions had been dissolved to prepare sodium salt of theligand. In this process the sodium metal first reacts with methanol and form sodiummethoxide. This sodium methoxide in the next step reacts with the ligand and replaces acidicproton from the enolic form of the ligand with the sodium metal and form sodium salt of theparticular ligand (Fig. 2). The ligands may be used as such but the rate of reaction will beslow as compared to the sodium salt. Removal of chloride from the metal chloride is easywith sodium as compared to hydrogen.

2.3 Synthesis of the Lanthanide (III) Complexes

The methanolic solution of the hydrated lanthanide chloride LnCl3.6H2O (2 g, 5.48 - 5.66mmol) was mixed with methanolic solution (50 mL) of the sodium salt of the ligand (3.13 –4.45 g, 10.96 – 11.32 mmol) in 1:2 molar ratios. The mixture was then heated under refluxfor about 13-16 h. On cooling, the sodium chloride which formed in this reaction was filteredthrough the alkoxy funnel and the excess of solvent from mother liquor was removed underreduced pressure. The physical properties and analytical data of these complexes arerecorded in Table 1. The suggested structure of the complexes is given in Fig. 2.

C N

HN

O

NC R

S

CN

NH

O

NCR

SH

Ln

.3H2O

Fig. 2. Structure of the metal complexesWhere, Ln = La, Pr, Nd and Sm , R = -NH2 or –SCH2C6H5


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2.4 Biological Activity

2.4.1 Antifungal activity

The antifungal activity of both the ligands and the synthesized complexes was evaluatedagainst Aspergillus fumigatus and Aspergillus niger using Czapek’s agar medium having thecomposition, glucose 20g, starch 20g, agar-agar 20g and distilled water 1000 mL. To thismedium was added requisite amount of the compounds after being dissolved indimethylformamide so as to get a certain concentrations (50, 100 and 200 ppm). Themedium then was poured into petri plates and the spores of fungi were placed on themedium with the help of inoculum’s needle. These petri plates were wrapped in polythenebags containing a few drops of alcohol and were placed in an incubator at 30 + 2ºC. Thecontrols were also run and three replicates were used in each case. The linear growth of thefungus was recorded by measuring the diameter of the fungal colony after 96 h and thepercentage inhibition was calculated by the equation:

% Inhibition = (C-T)100 / C

Where C and T are the diameters of the fungal colony in the control and the test plates,respectively [18].

Fig. 3. Antifungal activity of the ligands and their complexes.


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2.4.2 Antibacterial activity

Both of the ligands and their corresponding metal complexes were tested for theirantibacterial activity against Escherichia coli and Salmonala typhi using the paper disc platemethod [19]. The nutrient agar medium (peptone, beef extract, NaCl and agar-agar) and5mm diameter paper discs of Whatman filter paper No.1 were used. The compounds weredissolved in methanol for obtaining the concentrations of 500 and 1000 ppm. The filter paperdiscs were soaked in these solutions, dried and then placed in the petri plates previouslyseeded with the test organisms. The plates were incubated for 24 h at 28 + 2ºC andinhibition zone around each disc was measured.

Fig. 4. Antibacterial activity of the ligands and their complexes

2.4.3 Antifertility activity

The activity of the synthetic products towards the biological systems is an important featureof the current research, and the Schiff base metal complexes play a significant role in thisdirection. In view of such potential interest in these biologically active compounds, theantifertility activity of some selected compounds has been studied on male albino rats.Healthy adult male albino rats (Ratus norvegicus) of an average body weight 190-200 gwere used for experimentation. The animals were kept in clean polypropylene cagescovered with chrome plates grills and maintained in an airy room with controlled roomtemperature (20 ± 5ºC) with 12:12 hours light and dark cycle. The animals were fed withfood pellet procured from Ashirwad Industries, Chandigarh as well as germinated/sproutedgram and wheat seeds as an alternative feed. Tap water was supplied ad libitum.

Animals were divided into six groups containing 6 animals each. Group A animals were keptcontrol and were administered olive oil only. The animals in group B received ligand(HPHCBESH2) whereas the animals in groups C, D, E and F received La(III), Pr(III), Nd(III),


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Sm(III) metal complexes of ligand (HPHCBESH2), respectively. The animals weremaintained under perfect supervision and in accordance to the guidelines of committee forthe purpose of control and supervision of experiment on animals (CPCSEA) for theregulations of scientific experiments on animals. The experimental protocol has approval ofthe institutional ethical committee Dept of zoology UOR Jaipur. In the group B, the ligand 30mg/kg body weight suspended in olive oil was given orally through the mouth by pearl pointneedle for a period of 60 days. The animals of groups C, D, E and F received same doses ofrespective compound for the same period. It was then administered orally through the mouthby pearl point needle. No rat mortality occurred during the study period. The matingexposure test was done on day 55th of the experiment. The rats were sacrificed after 24 h ofthe last dose (61st day) to perform various tests. At the end of experiment, the rats wereweighed and sacrificed under light ether anesthesia. The male reproductive organs wereremoved, washed with distilled water, dried, weighed and processed for biochemical studies.Sperm mobility in cauda epididymis and sperm density in testes and cauda epididymis wereassessed. The protein, sialic acid, testicular glycogen acid and alkaline phosphatase oftestes, and serum testosterone were determined by standard laboratory techniques. Resultswere analysed statistically using student’s t-test.

3. RESULTS AND DISCUSSION

The reactions of hydrated lanthanide chlorides with bibasic tridentate ligands have beenshown by the following general equation:

MeOHLnCl3.6H2O+ 2LH2 + 4Na [Ln(L) (LH)].3H2O + 3NaCl + NaOH + 3H2O

Where, Ln = La, Pr, Nd and Sm, L= HPHTSCZ and HPHCBES

The newly synthesized complexes have been obtained as coloured solids which exhibit theirsolubility in methanol, DMSO and DMF. The monomeric nature of these products has beenconfirmed by the molecular weight determinations.

3.1 Electronic Spectra

The electronic spectra of the ligands and their metal complexes have been recorded in drymethanol. The electronic spectra of the ligands exhibit three bands in the regions 238-242,272-277 and 330-355 nm. The bands in the regions 238-242 nm and 272-277 nm areassignable to -* transitions of the azomethine group. The considerable hypsochromicshifting of the third band viz. 330-355 nm in the spectra of the metal complexes attributed tothe coordination of the azomethine nitrogen to the metal atom. The electronic spectra of thecomplexes are dominated by the ligands bands with the slight shift of spectral bands to thelower energy level. This slight shift was attributed to the effects of crystal field upon theinterelectronic repulsion of 4f electrons. The absorption bands appear in the spectra ofPr(III), Nd(III) and Sm(III) are due to transitions from the ground levels 3H4, 4I9/2 and 6H5/2 tothe excited ‘J’ levels of 4f configuration, respectively. The nephelauxetic parameter (β) [20],bonding parameter (b1/2) [21] and Sinha’s covalency parameter () [22] and angularcovalency (η) for the Pr(III), Nd(III) and Sm(III) complexes are presented in Table 2. TheSinha’s parameter () suggests the degree of covalency and is obtained by the equation,


125

= (1- βav)/ βav .100

Where βav is the average value of the ratio of vcomplex/ vaquo. The magnitude of the bondingparameters (b1/2) suggests the degree of involvement of 4f orbitals in metal–ligand bondingand is related to nephelauxetic ratio (β) by the equation,

b1/2 = [(1-βav)/2]1/2

Angular covalency (η) = (1-βav)1/2/ βav1/2

The intensity of the f–f transitions presents an interesting observation. The intensity of thenormal f–f transitions does not show much change. However, the hypersensitive transitions(environment sensitive transitions) are found to show large changes in intensity. Accordingto Karraker [23] the shape and intensity of these transitions indicate the geometry of thecomplex. In the present complexes, nephelauxetic ratio (β) being less than one and positivevalues of b1/2 and indicate slight covalent bonding between metal and ligand.

3.2 Infrared Spectra

The infrared spectra of the ligands show the most significant band in the region 1622-1618cm-1 assignable to (C=N) group which shifted to the lower frequency in the complexessuggesting the coordination of the azomethine nitrogen to the metal atom (Table 3). Theband in the region 3200-3050 cm-1 due to the (NH/OH) mode disappears in the complexes.The coordination of the azomethine nitrogen, phenolic oxygen and bonding of the thiolicsulfur to the metal ion is supported by the appearance of three absorption bands in theregions 530-515, 620-580 and 420–355 cm-1 in the complexes which may be assigned to(MN), (M-O) and (M-S) vibrations, respectively. However, two strong bands in theregions 3475-3460 and 3365-3350 cm-1 due to the asymmetric and symmetric vibrations ofNH2 group remain unaltered in the spectra of the complexes indicating the non-involvementof this group in the coordination. In the ligand HPHCBESH2, a doublet at 2895 and 2945cm-1 is assigned to symmetric and asymmetric vibrations of S-CH2-C6H5 grouping and isreduced to a weak doublet in the spectra of the complexes. The characteristic band due tov(SH) at 2610–2540 cm-1 present in spectra of the ligands was also seen in the complexesshowing that one ligand moiety of both type of ligands form coordinate bond in place ofsimple covalent bond to the metal atom. The broad band present in the region 3600-3568cm-1 may be assigned to (OH) stretching indicating the presence of water molecules.


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Table 2. Electronic spectral data of Ln(III)complexes

Complex Assignment Vmax of Ln+3

ion (cm-1)Vmax ofcomplexes(cm-1)

β 1-β b1/2 δ η

[Pr(HPHTSCZH)(HPHTSCZ)].3H2O 3H4 – 1D2- 3P0- 3P1- 3P2

17401209452145022820

17241208332127622727

.9908

.9946

.9918

.9959

.0092

.0054

.0082

.0041

.0678

.0519

.0640

.0452

.9285

.5429

.8267

.4116

.0963

.0736

.0908

.0641[Nd(HPHCBESH)(HPHCBES).3H2O 4I9/2 - 4G5/2,2G7/2

- 2G9/2- 4G11/2

168301979521913

166661960721739

.9902

.9905

.9920

.0098

.0095

.0080

.0700

.0689

.0632

.9896

.9591

.8064

.0993

.0978

.0897[Sm(HPHCBESH)(HPHCBES)].3H2O 6H5/2 – 4I13/2

- 4F9/2- 4I9/2- 6P3/2

21450258252652028733

21276256412631528571

.9918

.9928

.9922

.9943

.0082

.0072

.0078

.0057

.0640

.0600

.0624

.0533

.8267

.7252

.7256

.5732

.0908

.0851

.0886

.0756


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3.3 1H NMR Spectra

The 1H NMR spectra of both the ligands and their La(III) complexes were recorded inDMSO-d6 (Table 4). In the ligands, the signal in the region 10.05-12.10 ppm due to -OHdisappears in the complexes and this confirms the deprotonation and complexation throughthis functional group. The signal due to the -NH proton attached to the phenyl ring remainsunaltered in the complexes. In the spectra of La(III) complex, the -NH2 signal remainsunpurturbed at 2.58-2.60 ppm indicating the non involvement of this group in thecomplexation. The signal of -NH proton in the ligands in the range 8.59-8.78 ppmdisappears in the spectra of the corresponding complexes. The free ligands show multipletsin the region 6.70-8.32 ppm attributable to aromatic protons, which appear almost in thesame position in their respective complexes. The signals appearing at 5.50-4.51 ppm aredue to the SH proton. The appearance of this signal in the complexes showing that oneligand moiety of both type of ligands form coordinate bond in place of simple covalent bondto the metal atom.

3.4 13C NMR Spectra

The 13C NMR spectra of the ligands and their lanthanum complexes were recorded inDMSO-d6 and the assignments are shown in Table 4. The signals due to azomethine carbonappeared at δ152.81-153.43 ppm and on complexation they have shown downfield shift toδ156.26-158.05 ppm due to the resonance and also have given proof that nitrogen isinvolved in coordination. The spectra of the ligands exhibit a strong peak at δ175.02-176.24ppm due to C=S group which undergoes downfield shift in metal complexes suggesting theinvolvement of sulfur in coordination to the metal atom.

3.5 Magnetic Properties and EPR Spectra

The La(III) complexes are diamagnetic as expected. The room temperature magneticmoments of the complexes do not show much deviation from Van Vleck values [24]indicating that there is no significant participation of the 4f electrons in bonding since theyare well shielded by the 5s2 5p6 octet. However in case of Sm(III) complexes a slightvariation from Van Vleck values was observed [25]. Due to the low J–J separation, theenergy level between the ground state and the next higher level being only of the order ofKT, the excited states are also populated leading to anomalous magnetic moments. This isknown as the first order Zeeman Effect [26]. The EPR spectra (both at RT and LNT) werebroad having similar 'g' value of 1.98, which is nearly equal to the free electron value(g = 2.00277). Similar line widths at both the temperatures indicate spin–lattice and spin–spin relaxation processes contribute equally to line width.

3.6 Thermogravimetrical Analysis (TGA)

The TGA method was conducted to demonstrate the nature and number of the H2Omolecules in the complexes. Table 5 listed the losses in mass (Found and Calculated) of the[Pr(HPHTSCZH)( HPHTSCZ)].3H2O complex.


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Table 3. IR (cm-1) spectral data of the ligands and their corresponding complexes

Compound ν(C=N) (NH/OH) v(NH2) (SCH2C6H) v(SH) v(OH) ν(M→N) ν(M→O) ν(M→S)vsym vasym vsym vasym

HPHTSCZH2 1618 3050 3350 3475 - - 2540 - - - -HPHCBESH2 1622 3200 3365 3460 2895 2945 2610 - - - -[La(HPHTSCZH)(HPHTSCZ)].3H2O 1600 - 3348 3472 - - 2535 3600 530 620 420[Pr(HPHTSCZH)( HPHTSCZ)].3H2O 1598 - 3342 3469 - - 2532 3572 524 615 412[Nd(HPHTSCZH)(HPHTSCZ)].3H2O 1610 - 3339 3470 - - 2538 3585 518 586 358[Sm(HPHTSCZH)(HPHTSCZ)].3H2O 1608 - 3345 3465 - - 2536 3591 515 580 360[La(HPHCBESH)(HPHCBES)].3H2O 1602 - 3362 3452 2890 2940 2608 3576 526 618 417[Pr(HPHCBESH)(HPHCBES)].3H2O 1607 - 3356 3458 2885 2940 2600 3598 529 584 414[Nd(HPHCBESH)(HPHCBES).3H2O 1594 - 3363 3453 2889 2935 2598 3583 523 596 355[Sm(HPHCBESH)(HPHCBES)].3H2O 1612 - 3359 3457 2878 2936 2605 3568 520 585 356

Table 4. 1H NMR and 13 CNMR (, ppm) spectral data of the ligands and their La(III) complexes.

Compound 1HNMR 13CNMR-OH(s)

-NH(bs)

-SH(bs)

-NH2(s)

-S-CH2(s)

-NH(s)

Aromaticproton(m)

Thiolocarbon

>C=N Aromaticcarbon

HPHTSCZH2 10.05 8.59 - 2.60 - 10.64 6.75-8.32 175.02 152.81 159.76, 136.99, 129.15,127.79, 126.98, 125.58,122.44, 119.68, 117.94,116.89

HPHCBESH2 12.10 8.78 - - 1.92 10.75 6.70-8.19 176.24 153.43 158.72, 137.74, 133.81,127.82

[La(HPHTSCZH)(HPHTSCZ)].3H2O

- - 4.51 2.58 - 10.59 6.61-8.03 179.74 156.26 160.66, 138.89, 130.08,127.99, 129.85, 123.58,120.94, 120.48, 118.99,118.09

[La(HPHCBESH)(HPHCBES)].3H2O

- - 5.50 - 1.89 10.69 6.99-7.68 182.64 158.05 160.62, 137.84, 130.81,127.94


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Table 5. Thermogravimetrical analysis data for the metal complex

Complex formula Dehydration stage Start ofdecom-position

Oxide formationmetallic residues/%

Temperaturerange /ºC

H2O loss Temp./ºC

Calc. FoundCalc. Found

[Pr(HPHTSCZH)(HPHTSCZ)].3H2O

120-200 7.0683 7.0687 300 700 18.42 18.38

The complex decomposes in three steps. The initial mass loss within the range 120-200ºCcorresponds to the removal of three H2O molecules resulting in anhydrous complexes. Thefacts that the water molecule was lost at a low temperature suggest that the water is acrystal hydrate. The second and third subsequent decomposition steps start at 300ºC andcontinue upto 650ºC. Based on the above TGA results, the following three steps of thethermal decomposition may be proposed for the lanthanide imine complex.

[Pr(HPHTSCZH)( HPHTSCZ)].3H2ODehydration at

[Pr(HPHTSCZH)(HPHTSCZ )] + 3H2O

[Pr(HPHTSCZH)(HPHTSCZ)Partialdecomposition

300-450 0CIntermediate

IntermediateFinal decomposition

500-650 0CMetal Oxide

120-200 0C

Step - 1

Step - 2

Step - 3

3.7 Mass Spectra

The elemental analyses data of Nd(III) and Pr(III) complexes obtained are in agreement withthe formula [Nd(HPHCBESH)(HPHCBES)].3H2O and [Pr(HPHCBESH)(HPHCBES)].3H2O.The suggested formulae were further confirmed by mass-spectral fragmentation analysis.Many lanthanides possess several isotopes and the MS peak patterns are thereforecharacteristic of the nature of the cation present. Neodymium and Praseodymium haveseveral isotopes and the peak pattern of the compounds containing these metals thereforemuch more complicated. The spectra (although with low intensity) showed isotopic patternscentered around m/z (%) 954.26 and 950.93 for Nd and Pr, respectively, corresponding tothe mass weights of the complexes. The results thus obtained are in agreement with metal:ligand ratio, 1:2.

3.8 X-ray Powder Diffraction Studies

The possible geometry of the finely powdered product has been deduced on the basis of X-ray powder diffraction studies. The observed interplanar spacing values (’d’ in Å), have beenmeasured from the diffractogram of these compounds and the Miller indices h, k and l have


130

been assigned to each d value and 2θ angles are reported in Table 6 and Fig. 5. The resultsshow that the compound belongs to ‘Hexagonal’ crystal system having unit cell parametersas a = 18.528 Aº, b =18.528 Aº and c = 20.675 Aº maximum deviation of 2θ = 0.04 and α =90º, β = 90º and γ =120º.

Fig. 5. XRD-diffraction pattern of [Sm(L1H)(L1)].3H2O

Table 6. X-ray spectral data of [Sm(L1H)(L1)].3H2O.

H K l 2Theta(Exp.)

2Theta(Calc.)

2Theta(Diff.)

d(Exp.)

d(Calc.)

Intensity(Exp.)

3 0 4 30.190 30.193 -.003 3.71720 3.71680 30.234 1 2 33.898 33.942 -.044 3.32056 3.31639 40.344 0 5 39.287 39.292 -.005 2.87958 2.87920 64.485 1 4 45.227 45.235 -.009 2.51755 2.51708 12.966 1 0 46.608 46.607 .001 2.44689 2.44695 15.624 4 5 57.265 57.249 .016 2.02011 2.02064 53.137 2 2 60.304 60.346 -.042 1.92720 1.92597 16.606 2 7 65.997 66.005 -.009 1.77744 1.77723 11.578 2 1 67.370 67.408 -.038 1.74535 1.74449 15.475 2 9 68.862 68.840 .022 1.71207 1.71254 11.058 1 6 71.901 71.893 .008 1.64885 1.64900 44.815 1 11 75.865 75.887 -.022 1.57471 1.57431 26.925 5 8 80.019 80.011 .008 1.50567 1.50580 12.459 0 8 82.525 82.543 -.017 1.46778 1.46753 13.867 6 1 85.902 85.919 -.017 1.42069 1.42046 19.737 6 3 87.943 87.932 .011 1.39424 1.39438 22.59


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3.9 Biological Results and Discussion

Antimicrobial activity of the synthesized ligands and their corresponding metal complexes(Tables 7 and 8) on selected fungi, Aspergillus fumigatus and Aspergillus niger and twobacteria Escherichia coli and Salmonala typhi, were carried out (Figs. 3 and 4) [27]. Theresults of antimicrobial activity show that the metal complexes exhibit antimicrobialproperties and it is important to note that they show enhanced inhibitory activity compared tothe parent ligand. It has been suggested [28] that the ligands with nitrogen and sulfur donorsystems might inhibit enzyme production, since the enzymes which require these groups fortheir activity appear to be especially more susceptible to deactivation by the metal ions uponchelation. Chelation reduces the polarity [29] of the metal ion mainly because of the partialsharing of its positive charge with the donor groups and possibly the π-electrondelocalization within the whole chelate ring system thus formed during coordination. Thisprocess of chelation thus increases the lipophilic nature of the central metal atom, which inturn favours its permeation through the lipid layer of the membrane.

Table 7. Antifungal activity of the ligands and their complexes

Compound Diameter of inhibition zone (mm)Aspergillus fumigates, Aspergillus niger50ppm

100ppm

200ppm

50ppm

100ppm

200ppm

HPHTSCZH2 27 33 45 31 39 47HPHCBESH2 33 39 49 35 41 52[La(HPHTSCZH)(HPHTSCZ)].3H2O 48 58 69 46 60 65[Pr(HPHTSCZH)( HPHTSCZ)].3H2O 46 55 62 52 61 68[Nd(HPHTSCZH)(HPHTSCZ)].3H2O 41 48 56 51 58 66[Sm(HPHTSCZH)(HPHTSCZ)].3H2O 40 45 53 50 64 61[La(HPHCBESH)(HPHCBES)].3H2O 57 65 74 54 63 66[Pr(HPHCBESH)( HPHCBES)].3H2O 50 62 68 56 64 70[Nd(HPHCBESH)( HPHCBES).3H2O 43 50 60 52 60 68[Sm(HPHCBESH)(HPHCBES)].3H2O 42 48 59 53 66 63Flucanazole 90 100 100 95 100 100

Table 8. Antibacterial activity of the ligands and their complexes

Compound Diameter of inhibition zone (mm)E. coli, S. typhi

500 ppm 1000 ppm 500 ppm 1000 ppmHPHTSCZH2 4 8 5 8HPHCBESH2 6 9 6 9[La(HPHTSCZH)(HPHTSCZ)].3H2O 8 9 7 9[Pr(HPHTSCZH)( HPHTSCZ)].3H2O 7 10 6 10[Nd(HPHTSCZH)(HPHTSCZ)].3H2O 9 9 6 11[Sm(HPHTSCZH)(HPHTSCZ)].3H2O 6 8 8 11[La(HPHCBESH)(HPHCBES)].3H2O 10 11 9 12[Pr(HPHCBESH)( HPHCBES)].3H2O 9 13 10 12[Nd(HPHCBESH)( HPHCBES).3H2O 13 12 8 10[Sm(HPHCBESH)(HPHCBES)].3H2O 11 14 11 13Tetracyclin 16 20 15 18


132

The results of antifertility showed that administration of ligand and its metal complexes didnot affect the body weights of treated groups. However, a significant reduction in the weightof testes, epidydymis, seminal vesicle and ventral prostate was observed after treatmentwith ligand (HPHCBESH2) and its La(III), Pr(III), Nd(III), Sm(III) metal complexes. (Table 9)A significant decrease in motility of spermatozoa in cauda epidydymis and sperm density incauda epidydymis and testes have been observed in rats treated with ligand and its metalcomplexes. (Table 10) The reduction in the weights of these sex accessory organs may bedue to the decreased production of androgen [30].

Oral administration of ligand and its metal complexes caused a significant reduction intesticular glycogen and sialic acid contents where as cholesterol, sialic acid and alkalinephosphatase contents of testes were increased after treatment with in ligand and metalcomplexes (Table 11). Sialic acids are concerned with changing the membrane

Surface of maturing spermatozoa as well as with the development of their fertilizing capacity[31]. The results demonstrate a marked decrease in testicular glycogen, which may be dueto interference during glucose metabolism [32]. Inhibition of glycogen synthesis eventuallyaffects the protein synthesis and thus inhibits spermatogenesis [33].The serum testosteroneconcentrations were decreased significantly (P ≤ .01 to .001) after treatment with ligand(HPHCBESH2) and its La(III), Pr(III), Nd(III) and Sm(III) metal complexes (Table 11).

A marked reduction in testosterone content, in association with a highly reduced circulatinglevel of this hormone, confirmed alterations in the reproductive physiology of the rats. Theseresults suggested that the ligand and its complexes exert inhibitory effects on testicularfunction and lead to the infertility in male rats. Further, addition of a metal ion to the ligandenhances the activity.


133

Table 9. Effects of ligand and its complexes on body and reproductive organ weight of male rats

Group Treatment Body Weight Organ Weight (mg/100 g b.wt.)Initial Final Testes Epidydymis Seminal

VesicleVentralProstrate

A Control (olive oil) 221.0±16.4 231.0±14.5 1280.0±30.2 470.0±12.9 461.0±14.3 451.0±21.7B HPHCBESH2 226.0±10.3 237.0±13.3ns 1010.0±25.3a 359.0±13.2a 394.0±25.4a 398.0±19.7a

C [La(HPHCBESH)(HPHCBES)].3H2O 204.0±12.4 228.0±11.9ns 722.0±15.8b 281.0±11.2b 253.0±26.5b 279.0±17.9b

D [Pr(HPHCBESH)(HPHCBES)].3H2O 216.0±13.4 231.0±16.3ns 800.0±19.4b 293.0±14.1b 231.0±27.3b 251.0±30.3b

E [Nd(HPHCBESH)(HPHCBES).3H2O 218.0±15.4 238.0±16.5ns 710.0±20.4b 270.0±14.3b 222.0±26.9b 261.0±30.2b

F [Sm(HPHCBESH)(HPHCBES)].3H2O 209.0±9.8 225.0±14.3ns 652.0±30.2b 275.0±10.5b 228.0±28.3b 267.0±15.2b

Values are mean ± SEM of 6 determinationsa = p ≤ .01b= p ≤ .001

ns = p= Non SignificantGroup B, C, D, E and F compared with Group A

Table 10. Altered sperm dynamics and fertility of ligand and its various complexes treated male rats

Group Treatment Sperm Mortility (%) Sperm Density (million/mL) Fertility (%)Cauda Epidydymis Testes Cauda Epidydymis

A Control (olive oil) 71.5±4.5 4.78±0.7 60.4±3.70 100(+ve)B HPHCBESH2 58.5±4.7 a 3.20±.5 a 52.4±2.90 a 40(-ve)C [La(HPHCBESH)(HPHCBES)].3H2O 34.0±6.5 b 1.97±.3 b 25.0±2.10 b 82(-ve)D [Pr(HPHCBESH)(HPHCBES)].3H2O 31.0±5.4 b 1.80±.3 b 28.0±2.20 b 85(-ve)E [Nd(HPHCBESH)(HPHCBES).3H2O 33.0±5.1 b 1.50±.4 b 20.0±1.90 b 88(-ve)F [Sm(HPHCBESH)(HPHCBES)].3H2O 32.0±3.9 b 1.30±.3 b 22.3±2.10 b 85(-ve)

Values are mean± SEM of 6 determinationsa = p ≤ .01b= p ≤ .001

Group B, C, D, E and F compared with Group A


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Table 11. Testicular biochemistry and serum testosterone levels of ligand and its various complexes treated rats

Group Treatment Protein Sialic Acid Cholesterol Glycogen AcidPhosphatase

AlkalinePhosphatase

SerumTestosterone(mg/ml)

A Control(olive oil) 228.5±10.5 4.24±.70 8.0±.90 3.24±.39 3.21±.19 10.2±.60 2.90±.67B HPHCBESH2 281.0±5.3 a 3.18±.75 a 11.2±.70 a 2.71±.19 a 4.81±.20 a 14.1±.20 b 2.20±.72 a

C [La(HPHCBESH)(HPHCBES)].3H2O

336.0±2.9 b 1.91±.72 a 13.8±.39 b 1.48±.11 b 5.34±.16 b 17.2±.20 b 1.35±.10 b

D [Pr(HPHCBESH)(HPHCBES)].3H2O

332.0±3.6 a 1.82±.69 b 13.2±.35 a 1.42±.17 b 6.11±.32 b 17.6±.30 b 1.60±.30 b

E [Nd(HPHCBESH)(HPHCBES).3H2O

339.0±4.3 b 1.6±.75 b 13.6±.31 b 1.31±.13 b 6.22±.39 b 17.3±.40 b 1.28±.10 b

F [Sm(HPHCBESH)(HPHCBES)].3H2O

327.0±4.5 a 1.7±.60 b 13.7±.43 b 1.34±.14 b 5.74±.12 b 16.5±.35 b 1.15±.15 b

Values are mean ± SEM of 6 determinationsa = p ≤ .01b= p ≤ .001

Group B, C, D, E and F compared with Group A


135

4. CONCLUSION

On the basis of the analytical data and spectral studies, it has been observed that theligands coordinated to the metal atoms in a bibasic tridentate manner and thus possessoctahedral geometry. On the basis of X-Ray powder diffraction study [Sm(L1H)(L1)].3H2Ocomplex was found to have hexagonal lattice type. The biological screening data of theligands and their complexes indicate that the complexes are more potent than the parentligands.

ACKNOWLEDGMENTS

The authors are thankful to CSIR, New Delhi, India through grant no.09/149(0594)/2011/EMR-I for financial assistance.

COMPETING INTERESTS

Authors have declared that no competing interests exist.

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