1. INTRODUCTION:

Dithiocarbamates are organo sulphur compounds and their metal complexes have drawn much research attention due to their diverse applications and interesting biological, structural, magnetic, electrochemical and thermal properties ^1–7. They are used as accelerators in vulcanization, as high pressure lubricants, as fungicides and pesticides. Dithiocarbamates are often used for the synthesis of transition metal complexes ^8–12. The dithiocarbamates themselves, dithiocarbamate – metal complexes are used in agriculture for controlling insects and fungi ¹³, in the treatment of alcoholism etc., The dithiocarbamate ligands reported in only the dithiocarboxy group as the ligator group, so they behave like biddentate ligands in complexes. Dithiocarbamates have been found to act as uninegative bidentate ligands, coordinating through both sulphur atoms, and both tetra and hexa–coordinated complexes of many transition metal ions have been isolated ^14–15. This prompted the author to prepare the bidendate ligands of 2–Amino–3–Methyl pyridine and 2–Amino–4–Methyl pyridine as their sodium salts and to explain the detail investigations leading to the complexation of these ligands with Cu (II) and Co (II) metals.

2. MATERIALS AND METHODS:

2.1. Materials and methods

All materials used in this investigation were purchased from Sigma/Aldrich and AR (Merck). Solvents used were of reagent grade and purified before use by the standard methods Cu[2A3MPDTC] , Co[2A4MPDTC] complexes were prepared by the procedures described in the literature. Conductivity measurements of the above Cu and Co complexes were carried out on a systronics conductivity bridge 303, using a conductivity cell of cell constant 1.0. The dithiocarbamate metal complexes of Copper (II) and Cobalt (II) were soluble in dimethyl formamide (DMF). Infrared spectra of the metal complexes were recorded on a Perlan – Elmer IR 598 spectrometer (4000 – 200 cm^–1) using KBr Pellets. The ESR spectrum of copper complex was recorded, by using JEOL, JES FA 200 EST spectrometer, at HCU, Hyderabad. Microchemical analysis of Carbon, Hydrogen and Nitrogen for the complexes were carried out as a Herause CHNO–RAPID elemental analyzer. ¹HNMR spectra were recorded on av – 400 MHZ NMR spectrometer in IISC, Bangalore in DMSO–d6 solvent. Melting points were determined on a unimelt capillary melting point apparatus.

2.2. Preparation of Sodium salt of dithiocarbamate ligands:

0.05mol of amine was dissolved in 10ml of absolute alcohol in a clean beaker which was placed in ice. To this cold solution 5ml of sodium hydroxide (10N) solution was added and then pure carbondisulphide (3.02ml, 0.05mol) was added in drop wise through separating funnel with constant stirring. The components were stirred mechanically for about 30min, sodium salt of dithiocarbamate precipitated out. It was dried and recrystallised from methanol.

2.3. Synthesis of Dithiocarbamate Metal Complexes

The aqueous solution of 0.005mol of metal salts was added with constant stirring to an aqueous solution of 0.01 sodium dithiocarbamate ligand. The reaction mixture was stirred at room temperature for 8 hours. The colored precipitate was obtained. The precipitate was filtered and washed with water and then with methanol and dried over calcium chloride in a desiccator. All the complexes were prepared in 1:2 ratios of metal to ligand.

The elemental analysis data of Cu[2A3MPDTC] is as follows. Yield 64% and decomposes at 205^oC Anal. Calcd. For C–36.9%, H –3.87%, N–12.03%. Found C–35.12%, H–3.57%, N–11.94%.

The elemental analysis data of Co[2A4MPDTC] is as follows. Yield 58% and decomposes at 207^oC Anal. Calcd. For C–36.45%, H –3.90%, N–12.15%. Found C–35.92%, H–3.36%, N–11.78%.

3. RESULTS AND DISCUSSION

3.1. IR Spectral Studies

3.1.a IR Spectral studies of [2A3MPDTC] ligand and its Cu (II) metal complex

The typical IR spectrum of 2A3MPDTC ligand is presented in the Fig. 1(a). The most significant bands recorded in the FT–IR spectra of the ligand and its metal compolexes are reported in the Table 1(a).

As concern the 2–amino–3–methyl pyridine dithiocarbamate moiety, two main regions of the IR were considered. First, the (1451–1550 cm^–1) region, which is primarily associated with thioureide bond υ (N–CSS) stretching vibrations. Second, the 950–1000 cm^–1 region, which is associated with υ (C–S) stretching vibrations. The characteristic band at 1474 cm^–1, was assignable to υ (N–CSS) this band defines a carbon nitrogen bond order between a single bond (υ = 1250–1350 cm^–1) and a double bond (υ = 1640–1690 cm^–1).

A single sharp band at 998.44 cm^–1 is assigned to the stretching vibrations of the C–S bond. The band at 3227.95 cm^–1 associated with the υ (N–H) stretching vibrations and band at 1559.99 cm^–1, is associated with the υ (N=C) bond stretching pyridine ring.

The bands at 2918.39 cm^–1 and 1384.46 cm^–1, were associated with the υ (C–H) stretching vibrations and δ(C–H) binding vibrations of methyl group which is attached to the pyridine ring in 3^rd position.

The interpretation of IR spectra of dithiocarbamates complexes of transition metals had arisen considerable interest both diagnostically to determine the mode of co–ordination and as mean of assessing the nature of bonding in these complexes. The infrared spectrum of Cu(II) complex was compared with the [2A3MPDTC] ligand. The typical IR spectra of [2A3MPDTC] complex was presented in Fig. 1(b).

A Strong band exhibited at 1474 cm^–1 in the I.R spectrum of the ligand, which was assigned to the thioureide bond is shifted towards the higher region 1515.27 for Cu(II) complex, suggesting the complexation of ligand with metal ion. The presence of single band at 1027.30 cm^–1 was assumed to υ (C–S) stretching vibrational mode and it indicates the symmetric bidentate behavior of the ligand that means the 2A3MPDTC ligand is coordinated via both the sulphur atoms. Along with these bands new band was formed in spectra of complex at 381.25 cm^–1for Cu which assigned to υ (M–S), occurring in the far–IR region depends on the nature of the metal ion and the substituents attached with the sulphur atoms. The appearance of a broad band at 3437.05 cm^–1can be assigned to the υ (O–H) stretching vibrations of coordinated water molecules present in the complex.

Table: 1(a) The important IR Bands of the 2A3MPDTC and its Cu(II) metal complex

Name of the Compound	Thioureide bond	–OH (water)	C–S	M–S
L=2A3MPDTC	1474.31	–	998.44	–
[Cu(L)₂(H₂O)₂]	1515.27	3437.05	1027.30	381.25

Fig. 1(a) IR spectrum of the 2A3MPDTC ligand

Fig. 1(b) IR spectrum of Cu[2A3MPDTC] metal complex

3.1.b IR Spectral studies of [2A4MPDTC] ligand and its Co(II) metal complex

The typical IR spectrum of 2A4MPDTC ligand was presented in the Fig. 1(c). The most significant bands recorded in the FTIR spectra of the ligand and its metal complexes were reported in the table 1(b).

The characteristic band at 1489.16 cm^–1 was assignable to υ (N–CSS), this band defines a carbon nitrogen bond order between a single bond (υ = 1250–1350 cm^–1) and a double bond (υ = 1640–1690 cm^–1). The appearance of a band in that region indicates the strong delocalization of electrons in the dithiocarbamate moiety resulting the partial double bond character of –C–N bond. The presence of single sharp band at 1001.12 cm^–1 was assigned to the stretching vibrations of the –C–S.

C–N stretching vibration mode in cyclic derivatives is observed in 1415–1493 cm^–1 and is less intense than the alkyl derivatives, it is due to low double bond character caused by the rigid ring systems. The band at 3226.11 cm^–1 associated with the υ (N–H) stretching vibrations and the band at 1558.18 cm^–1, was associated with the υ (N=C) bond stretching in the pyridine ring. The bands at 2917.39 cm^–1 and 1384 cm^–1, were associated with the υ (C–H) stretching vibrations and δ (C–H) bending vibrations of methyl group which is attached to the pyridine ring in 4^th position.

The infrared spectra of Co(II) complex was compared with the [2A4MPDTC] ligand. The typical IR spectra of Co[2A4MPDTC] complexes were presented in Fig. 1(d).

A Strong band exhibited at 1489.16 cm^–1 in the IR spectrum of the ligand, which was assigned to the Thioureide bond is

shifted towards higher region 1506.44 for Co(II) complex, suggesting the complexation of ligand with metal ion. The presence of single band at 1021.62 cm^–1 was assumed to υ (C–S) stretching vibrational mode and it indicates the symmetric bidentate behavior of the ligand that means the 2A4MPDTC ligand is coordinated via both the sulphur atoms. Along with these bands new band was formed in spectra of complex at 382.46 cm^–1for Co which assigned to υ (M–S), occurring in the far–IR region depends on the nature of the metal ion and the substituents attached with the sulphur. The appearance of a broad band at 3290.30 cm^–1can be assigned to the υ (O–H) stretching vibrations of coordinated water molecules present in the complex.

Table: 1(b) The important IR Bands of the 2A4MPDTC and its Co(II) metal complex

Name of the Compound	Thioureide bond	–OH (water)	C–S	M–S
L=2A4MPDTC	1489.16	–	1001.12	–
[Co(L)₂(H₂O)₂]	1506.44	3290.30	1021.62	382.46

Fig. 1(c) IR spectrum of the 2A4MPDTC ligand

Fig. 1(d) IR spectrum of Co[2A4MPDTC] metal complex

3.2. NMR Spectral Studies

3.2(a) ¹HNMR spectral studies of [2A3MPDTC] ligand and its Cu (II) metal complex

Fig. 2(a–b) shows NMR spectra of 2A3MPDTC ligand and its Cu(II) metal complex. Fig. 2(a) gives the typical NMR spectrum of the ligand 2A3MPDTC. The important chemical shift values of the ligands and metal complexes are summarized in table 2(a). The methyl protons of the picoline of dithiocarbamate ligand were observed at 2.45ppm. The peaks in the aromatic region were seen as a set of multiplets in the range 7.5–7.7ppm and the signal due to proton attached to the Nitrogen, in thioureide bond was appeared as a broad singlet at 10.4 ppm. Fig. 2(b) shows typical NMR spectrum of the Cu(II) complex. In the complex signal due to proton bonded to Nitrogen in thioureide bond was observed in the 10.89ppm. It was observed that the aromatic ring protons of range 7.2–7.9 ppm become broad and less intensive when compared to the corresponding dithiocarbamate ligand. This effect may be due to drifting of ring electrons through metal ion. The broad signal at 8.95ppm. In the case of metal complex indicates the complexation of water molecule to metal ion, it was not observed in the case of free ligand.

Table 2(a) ¹HNMR spectrum of the 2A3MPDTC ligand and Cu(II) metal complex in DMSO–d₆ in ppm

Name of the Compound

H–N–C

Thioureide bond

–CH₃

Coordinated water

Py– H

L=2A3MPDTC

10.4

2.45

–

7.5–7.7

[Cu(L)₂(H₂O)₂]

10.89

2.43

8.95

7.1–7.9

Fig. 2(a) ¹HNMR spectrum of the 2A3MPDTC ligand in DMSO–d6 solvent

Fig. 2(b) ¹HNMR spectrum of the Cu[2A3MPDTC] metal complex in DMSO – d₆

3.2(b) ¹HNMR spectral studies of [2A4MPDTC] ligand and its Co(II) metal complex

Fig. 2(c–d) shows NMR spectra of 2A4MPDTC ligand and its Co(II) metal complex. Fig. 2(c) gives the typical NMR spectrum of the ligand 2A4MPDTC. The important chemical shift values of the ligands and metal complexes are summarized in table 2(b). The methyl protons of the picoline of dithiocarbamate ligand were observed at 2.31ppm. The peaks in the aromatic region were seen as a set of multiplets in the range 7.3–7.9ppm and the signal due to proton attached to the Nitrogen, in thioureide bond was appeared as a broad singlet at 10.2 ppm. Fig. 2(d) shows typical NMR spectrum of the Co(II) complex. In the complex signal due to proton bonded to Nitrogen in thioureide bond was observed in the 10.42ppm. It was observed that the aromatic ring protons of range 7.3–7.9 ppm become broad and less intensive when compared to the corresponding dithiocarbamate ligand. This effect may be due to drifting of ring electrons through metal ion. The broad signal at 9.5ppm. In the case of metal complex indicates the complexation of water molecule to metal ion, it was not observed in the case of free ligand.

Table 2(b) ¹HNR spectrum of the 2A4MPDTC ligand and Cu(II) metal complex in DMSO–d₆ in ppm

Name of the Compound

H–N–C

Thioureide bond

–CH₃

Coordinated water

Py– H

L=2A4MPDTC

10.2

2.45

–

7.3–7.8

[Co(L)₂(H₂O)₂]

10.42

2.37

9.5

7.42–7.9

Fig. 2(c) ¹HNMR spectrum of the 2A4MPDTC ligand in DMSO – d₆

Fig. 2(d) ¹HNMR spectrum of the Co [2A4MPDTC] metal complex in DMSO – d₆

3.3. UV – Spectral Studies

3.3.a UV spectral studies of Cu – 2A3MPDTC complex

The electronic spectrum(Fig–3.a) of Cu – 2A3MPDTC complex to intense bands observed at 261nm and 321nm were assigned to the intra molecular charge transfer of the ligand (π à π^* and n à π^* in the N–C=S group). A moderately intense peak observed at 383nm may be due to the ligand metal charge transfer. The less intensive broadband in the high wave length region corresponding to intra ligand dà d metal orbital transitions. In particular this broad band can be assigned to the dx²–y² à d_xy and dx² – y² à d_xz,_yz.

3.3.b UV spectral studies of Co – 2A4MPDTC complex

The electronic spectrum(Fig–3.b) of Co – 2A4MPDTC complex to intense bands observed at 269nm and 321nm were assigned to the intra molecular charge transfer of the ligand (π à π^* and n à π^* in the N–C=S group). A moderately intense peak observed at 392nm may be due to the ligand metal charge transfer. The less intensive broadband in the high wave length region corresponding to spin allowed dàd metal orbital transitions.

Fig. 3(a) UV–Vis spectrum of the Cu[ 2A3MPDTC] metal complex

Fig. 3(b) UV – Vis spectrum of the Co[2A4MPDTC] metal complex

3.4 a.: ESR Spectral analysis of Cu(2A3MPDTC] metal complex

ESR spectra obtained for copper complex in DMF at liquid nitrogen temperature and representative ESR spectrum of Cu(II) ion complex are presented in Fig. 4(a). In this low temperature spectrum, four peaks of small intensity have been identified which are considered to originate fromg|| component. The spin Hamiltonian, orbital reduction and bonding parameters of the complex were given in Table 3(a).

The Spin Hamiltonian parameters (g||, g_┴, A||, and A_┴.) were determined from the intense peaks of the spectrum. Kivelson & Neiman [58] have reported that g|| value is less than 2.3, for covalent character and it is greater than 2.3 for ionic character of the metal–ligand bond in complex.

The trend g|| > g _ave > g _┴> 2.0023 observed for the complex suggests that the unpaired electron was localized in d_x² – _y² orbital of the copper (II) complex. The lowest g value (>2.04) also consistent with d_x² – _y² ground state. The g||/A|| quotient ranges is 111.58 cm, evidence in support of the octahedral geometry without any distortion.

The dipolar interaction term (P) which takes into account the dipole-dipole interaction of the electron moment with the nuclear moment. The Fermi constant interaction term (K) indicates the interaction between the electronic and the nuclear spins given by the expression K=A₀/(P–Δg₀), where (Ag₀= g_e–g₀), it represents the amount of unpaired electron density at the nucleus and K was the independent property of the central ion.

The observed K|| < K_┴. indicates the presence of significant in plane π–bonding. Giordano and Bereman suggested the identification of bonding groups from the values of dipolar term P, reduction of P values from the free ion value (0.036 cm^–1) might be attributed to the strong covalent bonding. The lower P and α² values for Cu [2A3MPDTC] complex suggest the presence of strong in-plane n bonding which in agreement with higher ligand field. The shape of ESR lines, ESR data together with the electronic spectral data suggest octahedral geometry for copper complex.

Table 3(a). Spin Hamiltonian and orbital reduction parameters of Copper complex in DMF solution

Parameters	Cu (2A3MPDTC)2
g\|\|	2.2093
g┴	2.0052
gave	2.0731
G	4.54
A\|\|*	0.0198
A┴*	0.0016
A*ave	0.00713
d–d	19083
K\|\|	0.6185
K┴	0.9713
P*	0.0273
α2	0.5109

* Values are given as cm–1 units.

Fig. 4(a) : ESR Spectrum of the Cu[2A3MPDTC] metal complex

3.4. b : ESR spectral analysis of Co[2A4MPDTC1 metal complexes

ESR spectrum of cobalt complex in DMF was recorded at liquid nitrogen temperature and representative ESR spectrum was presented in Fig.4(b). In this low temperature spectrum, three peaks of small intensity have been identified which were considered to originate from g|| component.

The spin Hamiltonian, orbital reduction and bonding parameters of the complex were given in Table.3(b). The Spin Hamiltonian parameters (g||, g_┴, A||, and A_┴.) were determined from the intense peaks of the spectrum. The g tensor value of the cobalt complex can be used to derive the ground state. The trend g|| > g _ave > g_┴ > 2.0023 observed for the complex suggests that the unpaired electron was localized in d_x²__y²orbital of the cobalt (II) complex.

According to Kivelson & Neiman have reported that g|| value is less than 2.3, the covalent bond character can be predicted to exist between the metal and the ligand for complex. The lowest g value (>2.0027) also consistent with a d_x²__y² ground state. The g||/A|| quotient ranges is 111.02 cm^–1, evidence in support of the octahedral geometry with no appreciable distortion.

The Axial symmetry parameter G value was intended by using Kneubuh’s method by using the expression, G – g||–2/g_┴–2 and related to the exchange interactions between cobalt – cobalt centers. According to Hathway, for the present complex G=4.54, indicating the formation of monomeric complexes.

The molecular orbital coefficients or the bonding parameters α² (in plane σ–bonding) and β² (in plane π–bonding) were calculated. The observed α² value for the present chelate 0.5780 indicates that the complex was having some covalent character.

The dipolar interaction (P) which takes into account the dipole–dipole interaction of the electron moment with the nuclear moment. Giordano and Bereman suggested the identification of bonding groups from the values of dipolar term P. The reduction of P values from the free ion value (0.036 cm^–1) might be attributed to the strong covalent bonding. The lower P and a² values for Co [2A4MPDTC] complex suggest the presence of strong in–plane n bonding which was in agreement with higher ligand field. According to Hathway the observed K|| < K_┴ indicates the presence of significant in plane Π–bonding. The shape of ESR lines, ESR data together with the electronic spectral data suggest octahedral geometry for cobalt complex.

Table.3(b). Spin Hamiltonian and orbital reduction parameters of

Cobalt complex in DMF solution

Parameters	Co (2A4MPDTC)₂
g\|\|	2.3216
g_┴	2.0712
g_ave	2.1546
G	4.5168
A\|\|^*	0.0211
A_┴^*	0.00158
A^*_ave	0.008086
d–d	16103
K\|\|	0.7762
K_┴	0.8699
P*	0.0227
α²	0.578

* Values are given as cm^–1 units.

Fig. 4(b) : ESR Spectrum of the Co[2A4MPDTC] metal complex

3.5. a : Thermal Analysis of [2A3MPDTC] Cu complex

TG techniques were employed to follow the thermal behavior of complexes. According to the results obtained, the complexes were not volatile and their decomposition occurs in more than one step. The typical Thermogram of complex was shown in the Fig.5(a). Thermogravimetric studies on the complexes confirmed their proposed molecular formulae. The thermal decomposition of metal complexes had been followed up to 1000°. The decomposition behavior of the complexes is observed in nitrogen atmosphere. All the experimental mass loss and total mass loss percentage values found were presented in the Table.4(a).

The Copper complex shows three main decomposition stages, and the first stage was due to endothermic loss of water molecules coordinated to the metal. The Second step was the Exothermic decomposition of the ligand moiety forming stable intermediate M (SCN)₂ at around 221.15 – 498.63°C, the decomposition of this intermediate occurs at the third stage between 510.34–813.72°C. Mass loss calculations corresponds to formation of M (SCN)₂, which decomposes at higher temperature to give CuS at 841.09° C.

If the Thermal Analysis was carried out in the vicinity of oxygen the metal sulphides further forms Metal oxides as the final decomposition products. The decomposition of thiocyanates and cyanates proceeds at a slow rate at higher temperatures. The literature suggests that metal thiocyanates are common products in the thermal decompositions of dtcs.

Table.4(a) : Thermal Analytical Data of metal complexes

Complex X=H₂O	Temperature range in °C	Probable assignment	Mass loss (%)	Total mass loss (%)
Cu L₂ 2X L= C₇H₇N₂S2	86.32–125.46 221.15–498.63 510.34–813.72	Loss of 2H₂O molecules Decomposition of L Formation of CuS	7.712 53.54 18.12	79.37

Fig. 5(a) : Thermogram of the Cu[2A3MPDTC] metal Complex

3.5. b : Thermal Analysis of Co [2A4MPDTC] complex

TG techniques were employed to follow the thermal behavior of complexes. According to the results obtained, the complexes are not volatile and their decomposition occurs in more than one step. The typical thermogram of complex was shown in the Fig. 5(b). The thermal decomposition of metal complexes had been followed up to 1000°. The decomposition behavior of the complexes was observed in nitrogen atmosphere. All the experimental mass loss and total mass loss percentage values found were presented in the Table.4(b).

The thermogram of the Cobalt complex shows three main decomposition steps. First stage of decomposition around 98.36°C to 156.28 °C, which indicates the presence of coordinated water molecules and this decomposition corresponds to small endothermic dehydration of the complex and gives anhydrous complex. The second decomposition stage at 158.85 – 210.93°C with a broad exothermic peak corresponds to the degradation of ligand moiety into stable M (SCN)₂ intermediate. Third stage of decomposition with successive sub steps in the temperature region of 277.84 – 793.15°C with two exothermic peaks corresponds to the decomposition of intermediate to give the corresponding cobalt sulphide as the final decomposition product.

If the Thermal Analysis was carried out in the vicinity of oxygen the metal sulphides further forms Metal oxides as the final decomposition products.

Table.4(b) : Thermo analytical Data of metal complexes

Complex X=H₂O	Temperature range in °C	Probable assignment	Mass loss (%)	Total mass loss (%)
Co L₂ 2X L= C₇H₇N₂S₂	98.36–156.28 158.85–210.93 277.84–793.15	Loss of 2H₂O molecules Decomposition of L Formation of CoS	7.69 54.35 18.29	80.49

Fig. 5(b) : Thermogram of the Co[2A4MPDTC] metal complex

4. ANTIBACTERIAL ACTIVITY:

The present investigation was an attempt to find out antibacterial activity of ligand and their metal complexes against Escherichia coli, Staphylococcus aureus and Bacillus subtilis in the range 50–150 um/ml. Choosing serial paper disc diffusion method. The antibacterial activity results were given in the table 5. The high antimicrobial activities of all the newly synthesized metal complexes surmounting that of ligands showed that complexation of the organic moiety to the metal ions substantially enhanced their activities. Such increased activity of metal chelates had been explained by Overtones concept and the Tweedy’s chelation theory. On chelation the polarity of the metal ion reduced to a greater extent due to the overlap of the ligand orbital and partial sharing of positive charge of metal ion with donor groups. It was further noted that the delocatlization of II–electrons over the whole chelate ring enhanced the lipophillicity of the complexes. This increased lipophillicity enhanced the penetration of the complexes into lipid membrane and blocking the metal binding sites on enzymes of microorganism thus retarding the normal cell processes.

Table 5 : Antibacterial activities of ligand and their transition metal complexes (Zone formation in mm)

Compound	*Escherichia coli*	*Staphylococcus aureus*	*Bacillus subtilis*
2A3MPDTC	7	8	7
(2A3MPDTC)₂Cu	10	12	11
2A4MPDTC	7	7	8
(2A4MPDTC)₂Co	9	10	11

5. CONCLUSION:

By concluding the above information the different dithiocarbamate ligand of 2–amino–3–methyl pyridine, 2–amino–4–methyl pyridine acts as good complexing agents towards many transition metal ions. By using all the above mentioned analytical data it was concluded that they behave as symmetric bidendate ligand during complexation. All the metal complexes carry no charge and are thermally stable. As such no single technique is independent of predicting final structures of the complexes, the entire information available from all the studies were clubbed together and suggested structures of the complexes for mentioned as follows.

Fig. 6(a) : M[2A3MPDTC]; M=Cu(II)

Fig. 6(b) : M[2A4MPDTC]; M=Co(II)

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Received on 02.01.2013 Modified on 19.01.2013

Asian J. Research Chem. 6(4): April 2013; Page 323-330