Synthesis and Characterization of Bio Active Transition Metal Complexes of Cu(II) Co(II) and Ni(II) using Natural Sources

Bismi S Prakash.¹, Isac Sobana Raj. C.², Allen Gana Raj G.³

¹Research Scholar Department of Chemistry and Research centre, N.M Christian College, Marthandam- 629165, India.

²Department of Chemistry and Research centre, N.M Christian College, Marthandam-629165, India.

³Department of Chemistry and Research centre, Scott Christian College (Autonomous) Nagercoil- 629003, India.

*Corresponding Author E-mail: bismi07@gmail.com , isacsobanaraj@yahoo.co.in , allengraj@gmail.com

ABSTRACT:

Cardanol a naturally occurring C₁₅ unsaturated aliphatic chain substituted phenol derived from cashew nut shell liquid (CNSL) was used for the preparation of Schiff base ligand using Glutamine. Di-α-formylmethoxybis(3pentadecenylphenyl)methane (DFMPM) is prepared from cardanol using standard methods. The ligand formed Schiff base complexes with Cu(II), Co(II) and Ni(II) ions. The ligand and complexes were characterized by UV-visible, IR, and the elemental analysis, melting point, metal ion intake, SEM, XRD antibacterial and antifungal activity were studied. The result indicate that the complexes of Cu(II), Co(II) and Ni(II) are hexaco-ordinated and have moderate antibacterial and antifungal activity. The metal ion intake indicated the ligand can be used for the removal of these metals from water. The SEM and XRD studies revealed the nano crystalline nature of the complexes.

KEYWORDS: Cardanol, Formaldehyde, Epichlorohydrin, Glutamine, Schiff base

INTRODUCTION:

Compounds which contain pyridine and its derivatives of Schiff bases as ligands have occupied a central role in the development of coordination chemistry and biochemistry. Schiff base complexes of transition metals are highly useful due to their structure and physico-chemical properties. Cardanol is the main component obtained by vacuum distillation of roasted cashew nut shell liquid (CNSL) and was used for the preparation of bioactive transition Schiff base metal complexes.

The preparation involves (i) conversion of cardanol into bis(3-pentadecenyl phenol)methane (BPPM) (ii) conversion of BPPM to DFMPM (iii) condensation of DFMPM with glutamine to give Schiff base ligands^[1-3] and finally (iv) Schiff base complexes with transition metal salts. The ligands and complexes were characterised by UV-visible, FTIR and the elemental analysis, melting point, conductivity, metal ion intake anti bacterial and fungal activity were studied^[1-3].The result indicate that the complexes of Cu(II), Co(II) and Ni(II) were bioactive and also used for the removal of such ions from water the nano crystalline nature of complexes were confirmed by SEM and XRD studies.

MATERIALS AND METHODS:

Cardanol was obtained from M/S Sathya Cashew Chennai India, formaldehyde (37% solution), hydrochloric acid, epichlorohydrin, L-glutamine, sodium hydroxide and other chemicals were used of GR/AR grade quality obtained from Merk chemicals. All the solvents used were purified by standard methods^[4]. The micro analytical data (C,H,N) were collected using Perkin Elmer 2400 instrument. The metal ion intake were estimated by standard methods^[5] IR spectra were obtained by using PEIR spectrum instrument Model: 2000.

Synthesis of Schiff base ligand with DFMPM and L-glutamine:

The Schiff base ligands was prepared by the reported methods^[6-7]. Equimolar ethanolic solution of DFMPM and L-glutamine were mixed and refluxed for about an hour. Pour the reaction product in ice, (1+2) Schiff base ligand was obtained^[8]. The precipated yellow compound was filtered washed with water and dried over anhydrous calcium chloride. The crude sample was recrystalised from 50% absolute alcohol yield=62%. Melting point =223°C.

Synthesis of Cu(II), Co(II) and Ni(II) Schiff base metal complexes:

All the metal complexes were prepared by mixing ethanolic solution of Schiff base ligand with the corresponding aqueous metal salt solution of Cu(II) nitrate, Co(II) nitrate and Ni(II) nitrate in 2:1 molar ratio. The resulting mixture was refluxed for about twelve hours at 70-80°C^[9]. A coloured solution appeared on standing. The complexes were filtered, washed with ethanol, diethyl ether, acetone and hot water and finally dried under vaccum at 90°C.yield=60%

Estimation of metal ion intake:

The filtrates obtained in the above method were collected. The collections were used for the estimation of Cu(II), Co(II) and Ni(II) intake for complexation using standard methods^[10].

RESULT AND DISCUSSION:

The metal complexes of Cu(II), Co(II) and Ni(II)are coloured solids, stable towards air and have high melting points above (250^oC). The complexes are insoluble in water and common organic solvents but are soluble in DMF, CDCl₃ and DMSO. Analytical data (Table 1) suggest that the metal to ligands ratio in all the complexes to be 1:2^[11]. Conductivities of solutions of the complexes are non electrolytes because their conductivity value were in the range 12-15 ohm^-1cm² mol^-1.However the conductivity value is higher than expected for non electrolytes probably due to partial solvolysis of the complexes in DMF medium.

IR Spectra:

IR spectra of the complexes were compared with the free ligand in order to determine the involvement of co-ordination sites in chelation. Characteristic peaks in the spectra of the ligand and complexes were considered and compared. The selected IR spectral data are given in (Table2).The IR spectrum of the ligand (Fig.1) showed characteristic bands at 2856 cm^-1, 2923 cm^-1, 1606 cm^-1 due to the n_O-C, n_C-H, n_C=H respectively^[12]. The IR spectra of the complexes (Fig. 2-4) exhibited ligand bands with the appropriate shifts due to complex formation. The IR broad bands of metal complexes in the range of 3427-3188cm^-1indicate the presence of co-ordinated or lattice water molecule^[13]. The n_C-O phenolic stretching frequency is observed around 2924-2845 cm^-1 which get shifted to lower or higher frequency region indicating co-ordination of phenolic oxygen. Band at 2923-2855cm^-1 were assigned to C-H and 1710-1605cm^-1 were assigned to C=N respectively^{[14, 15]}. The imine peaks in the metal complexes showed changes in the ligand indicating co-ordination of the imine nitrogen atom to the metal ion due to co-ordination. Another absorption bands at 780-692cm^-1 is assigned to M-N bond and 702-599cm^-1 is assigned to M-O bond^[16-17]. The absorption bands at 3801-3013 cm^-1 is assigned to free NH₂ group and 1455-1442 cm^-1 is assigned to free COOH group and 1590-1489 cm^-1is assigned to C=O group. It shows that the terminal NH₂ group is not involved in bonding.

Table 1 Physical characteristics and analytical data of complexes

Compounds	yield	Colour	molecular formula	Molecular Weight	Melting point	Elemental Analysis
						C	H	N
Ligand(L)	60	Brown	C57H100N4O8	968	229	70.01 (70.66)	10.0 (10.33)	5.07 (5.78)
[CuL (NO3)2 ]	57	Light green	C114H200N6O22 Cu	2123	>250	64.18 64.43)	9.73 (9.60)	3.31 3.95)
[CoL (NO3)2 ]	56	Grey	C114H200N6O22Co	2119	>250	64.29 64.55)	9.39 (9.43)	3.19 (3.96)
[NiL (NO3)2 ]	58	Brown	C114H200N6O22Ni	2118.69	>250	64.37 (64.56)	9.48 (9.43)	3.75 (3.96)

Table 2 Selected FT-IR frequencies (cm^-1) and UV of the ligand and complexes

Ligand/ Complexes	nO-H	nO-C	nC-H	nC=N	nC=O	Free -COOH	Free -NH2	nM-N	nM-0	l max(nm)
Ligand( L)	-	2856	2923	1606	1489	1455.02	3013	780	702	-
[CuL (NO3)2 ]	3427	2854	2923	1605	1590	1455.39	3800	692	599	327 368 231
[CoL(NO3)2 ]	3188	2845	2924	1646	1600	1442.49	3801	771	600	382 - 224
[NiL(NO3)2 ]	3389	2924	2855	1710	1589	1445.39	3741	773	696	372 332 -

Fig. 1: FTIR Spectrum of ligand (L)

Fig.2: FTIR Spectrum of Cu(II) complex of Ligand

Fig.3: FTIR Spectrum of Co(II) complex of Ligand

Fig.4: FTIR Spectrum of Ni(II) complex of Ligand UV-visible spectra

The UV visible spectra (Fig. 5-7) are often very helpful in the evaluation of results furnished by other methods of structural investigation. The ligand showed a broad band at 360nm which is assigned to π-π* transition of the C=N chromophore^[18].On complexation this bond was shifted to lower wave length suggesting the co-ordination of imine nitrogen with central metal ion. The UV spectrum of Cu(II) complex showed three absorption bands at 327, 368, 231nm giving an octahedral geometry with field transition ²B₁g->²A₁g,²B₁g->²B₂g and ²B₁g->²E₂g,respectively^[19-20]. The UV spectrum of Co(II) and Ni(II) complexes showed absorption bands at 382nm and 224nm and 372 and332nm respectively suggesting octahedral geometry. On the basis of above studies the probable structure of the M(II) Schiff base complexes of Cu(II),Co(II) and Ni(II) may be presented as in figures 8, 9.

Fig.5:UV-Visible Spectrum Cu(II) complex of ligand

Fig.6:UV-VisibleSpectrum Ni(II) complex of ligand

Fig.7: UV-VisibleSpectrum Co(II) complex of ligand

Figure 8: Structure of ligand

Figure 9: Structure of Schiff base complexes, M=Cu(II),Co(II) and Ni(II) SEM analysis

The surface morphology of the complexes has been examined using scanning electron microscope. The SEM image of Co(II) complex is given below. The SEM images showed that the complex is micro crystalline in nature. Careful examination of single crystal, clearly indicate the nanoscale size of the single crystal of the complexes^[21]. Lower magnification showed grain like appearance.

Fig.10: SEM image of Schiff base of Co(II) in ethanol

Fig :11 SEM image of powder sample of Co(II) X-Ray Diffraction Analysis

The powder XRD for the Cu(II) was performed. The diffract gram is given in Fig.12. It is evident that the strong and broad peaks confirm the complex formation and the appearance of large feeble peaks indicate micro crystalline.

Fig.12: XRD spectrum of Cu(II) of ligand Metal ion intake

Table 4 Antibacterial and Anti fungal activity data of complexes

Ligand / complex	E. coli	P.aeruginosa	Klebsiella pneumoniae	Staphylococcus aureus	Candida albicans	PC	NC	Metal Ion intake meq/g
[CuL(NO3)2]	13.0	10.0	15.0	18.0	12.0	25.00	6.0	0.6012
[CoL(NO3)2]	6.0	19.0	22.0	17.0	6.0	22.00	6.0	0.4625
[NiL(NO3)2]	6.0	6.0	6.0	13.0	6.0	24.00	6.0	0.5120

Media : Mueller Hinton Agar for bacteria * PC - Chloramphenicol

The grain size of the complexes was calculated using Scherer’s formula. The calculated grain size of the complexes is in the range of 1.4477nm. These values suggested that the complexes are in nano crystalline size^[21]. Table 3

Table 3 Grain size of the Cu(II) complexes

Complex	Grain size(nm)
[CuL (NO3)2 ]	1.4477

The complexation behaviour of cardanol based Schiff base was affected by structural parameters^[22]. This study indicates that the metal ion intake decreased Cu(II), Co(II), and Ni(II)^[23] (Table.4).This order can be explained by Pearson’s proposal ^[24], hard acid preferred to combine with hard base and soft acid preferred to combine with soft base. It was found that the interaction of Cu(II) is normally more intense than other divalent metal ion with Schiff base ligand^[25]. Nature of the ligands and the chelate effect were the factors involved in the environmental chemistry and technological interest ^[26] . The complexes also be used for the removal of Cu(II),Co(II)and Ni(II) ions from water.

Antibacterial activity:

Antibacterial activity of the ligand complexes and standard drugs were screened by the disc diffusion method in ethanol as solvent. The result of antibacterial study is given in table 4.The antibacterial activity was estimated based on the size of inhibition zone in the disc. Under identical conditions the Schiff base complexes of Cu and Co have moderate antibacterial activities against these bacteria. The results of antibacterial activity substantiate the findings of earlier research^[27]the biological inactive compound become active and less biologically active compounds become more active upon coordination^[28] such enhancement in biologically compounds become more active upon coordination ^[29]such enhancement in biological activity of metal complexes can be explained on the basis of Overtone’s concept of cell permeability, the lipid membrane that surrounds the cell flavours the passage as only lipid soluble materials due to which lipho solubility is an important factor that controls antimicrobial activity. On chelation, the polarity of the metal ion is reduced to a greater extent due to overlap of the ligand orbital and partial sharing of the positive charge of the metal ion with donor groups. Further, it increases the delocalisation of π-electron over the whole chelate ring and enhanced liphophilicity of the complex. This enhanced the liphophilicity in turn enhances the penetration of the complex in to lipid membranes and blocking of metal binding sites on the enzymes of the micro organism^[30] . The metal complex may also be a vehicle for activation of the ligand as the cytotoxic agent. Moreover, coordination may lead to significant reduction of drug resistance. Also other factors such as solubility, conductivity and dipole moment may also be among the possible reason causing enhancement of bactericidal activity of the metal complexes as compared to the uncomplexed Schiff base compound.

CONCLUSION:

Schiff base metal complexes of Cu(II), Co(II) and Ni(II) were synthesized from cardanol using L-glutamine were clearly characterized on the basis of analytical and spectral data. Metal ion intake explained that the ligand can be effectively used for the extraction of metal ion from water. From the spectral and stoichiometric analysis, a hexa coordinated nature was assigned for the metal complexes. The nitrate group is present inside the coordination sphere. The XRD and SEM studies reveal that the complexes are nanocrystalline. The antibacterial study showed that Cu(II) and Co(II) have more antibacterial activity than Ni(II) complexes. The antifungal study revealed that Cu(II) complexes have more antifungal activity than other complexes.

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Received on 17.11.2015 Modified on 25.11.2015

Accepted on 14.12.2015 © AJRC All right reserved

Asian J. Research Chem. 8(12): December 2015; Page 726-732

DOI: 10.5958/0974-4150.2015.00117.0