Mixed Ligand Complexes Of Co Research Articles

Synthesis and Characterization Some Complexes of Mixed Ligand and Study Its Effects as Antioxidant and Anticancer

A series of mixed ligand complexes of Co(II), Ni(II), Cu(II), Zn (II),Cd(II), Fe (III ) andAu(III) were prepared and characterized. A new azo ligand derived from 4-methylimidazole with sulfadiazine and Schiff base derived from 4-(dimethylamino)-2-hydroxobenzaldehyde and 4-amino-3-hydroxy benzene sulfonamide. Ligands structures and their transitional metal mix-ligand complexes were characterized using various analytical techniques, including molar conductance, elemental analysis (C.H.N), electronic spectral, magnetic measurements, 1HNMR, IR spectral studies and mass spectra. The data shows that these complexes have composition of [ML1L2H2O] where M = Co(II), Ni(II), Cu(II), Zn(II) ,Cd(II) and Hg(II). [ML1L2Cl] where M=Fe(III). [ML1L2]Cl2 where M=Au(III). The magnetic susceptibility and electronic spectral data of the complexes indicate that the octahedral geometry of all complexes, except the complex of Au(III) indicates a square plane geometry. The IR results demonstrate that the co-ordination sites are imidazole nitrogen atom and the farthest azo nitrogen atom of L1 as natural bidentate with nitrogen the azomethine and oxygen atoms of Schiff base L4. Azo ligand and Schiff base behave as tridentate manner. All the compounds showed DPPH radical scavenging activity. In general, the results indicated that the complexes have potential and promising anti-oxidant activities.

Mixed Ligand Complexes of Cobalt(II): Synthesis, Reactivity, Physico-Chemical and Spectroscopic Studies

The mixed ligand complexes of Co(II) metal ions with some heterocyclic nitrogen bases along with 1-cyano-1-carboethoxyethylene-2,2-dithiolate ion (CED2−) of the compositions, Co(N-N)(CED)·2H2O [N-N = o-phen/2,2′-bipy] and Co(N-N)(CED)L2 [N-N = o-phen/2,2′-bipy, CED2– = 1-cyano-1- carboethoxyethylene-2,2-dithiolate, L = γ-picoline (γ-pic), β-picoline (β-pic), α-picoline (α-pic), pyridine (py)] were characterized and isolated by analytical data as well as physico-chemical methods for example infrared spectroscopy, electronic, magnetic susceptibility, molar conductance. The complexes are soluble in coordinating solvents like DMSO and DMF and decompose below 250 ºC. The synthesized complexes in DMF solution are non-electrolytic as shown by their molar conductance data. The calculated magnetic moments suggest that the synthesixed cobalt(II) compounds are paramagnetic and produce a low-spin environment for the Co(II) ion. Thermal studies reveal that Co(N-N) contains two coordinated water molecules (CED)·2H2O. Electronic spectra of cobalt(II) complexes with mixed ligands in DMF solution are consistent with distorted octahedral stereochemistry. The IR studies indicates that the CED2- ion exhibits bidentate chelating behaviour and that heterocyclic nitrogen donors coordinate to Co atoms (II). Reaction with heterocyclic nitrogen donors (γ-picoline, β-picoline, α-picoline, pyridine) signifying the ligand exchange reaction.

Synthesis, characterization and antimicrobial properties of Cobalt(III), Nickel(III), Copper(II) and Zinc(II) complexes with pyridine and thiocyanate

Mixed-ligand complexes of Co(III), Ni(III), Cu(II) and Zn(II) with pyridine and thiocyanate have been synthesized and characterized using elemental analysis, infrared and UV-Vis spectroscopy, thermal analytical techniques, melting point determination, molar conductivity and room temperature magnetic susceptibility measurements. The results suggest that all complexes are stable and molecular with octahedral coordination geometry for the Co(III) and Ni(III) complexes, square planar or tetrahedral geometry for the Cu(II) complex and a tetrahedral geometry for the Zn(II) complex. Evaluation of the antimicrobial activities of the ligands, metals salts and complexes on four bacterial strains (E. Coli, K.Pneumonia, S.typhi and S. flexneri) and four fungal strains (C. Albicans, C., Parapsilopsis, C. tropicalis and C. neoformans) showed higher activity of the complexes compared to the ligands and metals salts. The Co(III) complex showed higher activity than the reference drugs; doxycycline and Penicillin while the Cu(II) complex showed higher activity than the reference antibiotics; doxycycline and nystatin.

Biologically active mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) as potential antimalarial, antidibetic and anticancer agents

Mixed ligand complexes of transition metal ions Co(II), Ni(II), Cu(II) and Zn(II) were synthesized using bidentate Schiff’s base (E)-2-((benzo[d]thiazol-2-yliminomethyl)-6-methoxyphenol (L1), derived from condensation reaction of 2-aminobenzothiazole and 2-hydroxy-3-methoxybenzaldehyde, and 5-Chloro-8-hydroxyquinoline (5CHQ) (L2) as ligands. All the synthesized compounds were characterized using elemental analysis, IR, electronic, 1H and 13C NMR spectra, TGA-DTA and Powder XRD analysis, molar conductivity and magnetic susceptibility measurements. Based on the results obtained all the synthesized complexes are proposed to have tetrahedral geometry. All the synthesized compounds were screened for their antioxidant, antimicrobial, antimalarial, antidibetic, anticancer activities and cytotoxicity study using MTT assay. The complexes are proposed to have potential antimalarial, antidibetic and anticancer activities.

Synthesis, spectroscopic characterization, computational studies, theoretical investigation of NLO properties and antibacterial activities of mixed ligand complexes of Co(II) and Cu(II)

The reaction of Schiff base 2-(4-(dimethylamino)benzylideneamino)phenol (DBAP) and diethylenetriamine/ethylenediamine with cobalt(II) and copper(II) metal ion in equimolar ratio afforded mixed ligand complexes [M(DBAP)(L)Cl(H2O)n] (1–4), where M = Co(II) 1, 2; Cu(II) 3, 4; L = diethylenetriamine (1, 3); n = 0 and ethylenediamine (2, 4); n = 1. All the newly synthesized complexes were characterized by elemental analysis, spectroscopic techniques viz., UV-vis, FT-IR, ESR, PXRD and mass spectrometry. The influence of chelation of cobalt(II) and copper(II) ion on nonlinear optical properties of Schiff base (DBAP) were examined with DFT study. The polarizability (α0) and first-order hyperpolarizability (β) of ligand and their metal complexes were calculated and compared with reference molecule p-nitroaniline. The hyperpolarizability of Schiff base and their metal complexes show a good nonlinear optical behavior. Theoretical investigation of the complexes was performed by DFT using B3LYP level of theory on the basis set 6-31 G (d, p)/LanL2DZ. On the basis of spectroscopic data and DFT computation, a six-coordinate geometry is tentatively proposed around the metal ion. In vitro antibacterial activities of these complexes were also screened against V. cholerae and E. coli, and found to have good antibacterial activity.

Novel mixed ligand complexes of Co(II), Ni(II), Cu(II), and Zn(II) with 1,10-phenanthroline and acesulfame. Synthesis, structural analysis and hydrogen adsorption study

Four novel metal organic framework (MOF) structures containing acesulfame (ace) and 1,10-phenanthroline (phen) ligands of Co2+, Ni2+, Cu2+ and Zn2+ metal cations were synthesized. The crystal structure analysis of three compounds (1, 2, and 3) was also performed. The structural formula for complex 4 is proposed based on spectroscopic and thermal analysis data. It has been determined that structures 1, 2, and 4 are in a distorted octahedral geometry. It has been suggested that the charge balance of the coordination sphere with 2+ is provided by two monoanionic ace ligands located outside the coordination sphere as counter-ion. In structure 3, there are two CuII metal cations, two phen ligands coordinated as bidentate to each metal cation and ace ligand that provides monoanionic-monodentate coordination. The Cu2+ cation has distorted bipyramidal geometry. The maximum hydrogen gas adsorption has been found 1.4575 mL/g (0.046 wt%) for the Ni complex.

Mixed ligand complexes of Co(II), Ni(II) and Cu(II) with quercetin and diimine ligands: synthesis, characterization, anti-cancer and anti-oxidant activity.

In this work, mixed ligand complexes of Co(II) Ni(II) and Cu(II) were synthesized using quercetin and diimine (1,10-phenanthroline or 2,2'-bipyiridine) ligands. The obtained Ni(II) and Co(II) complexes are new and the Cu(II) complexes are synthesized by different method from the literature. The characterization of complexes was performed by elemental analysis, thermogravimetric analysis, ESI-MS, UV-visible and infrared spectral analyses, magnetic susceptibility and molar conductivity measurements. It was found that quercetin, diimine and metal(II) ion form 1:1:1 complexes. Resulting data supported octahedral geometry for Ni(II) and Co(II) complexes and square pyramidal geometry for Cu(II) complexes. The proposed compositions are [Co(queH-1)Cl(phen)(H2O)]∙2H2O (1, queH = quercetin, phen = 1,10-phenanthroline), [Ni(queH-1)Cl(phen)(H2O)]∙2H2O (2), [Cu(queH-1)Cl(phen)]∙2.5H2O (3) and [Cu(queH-1)Cl(bpy)]∙2H2O (4, bpy = 2,2'-bipyiridine). Antioxidant capacity and total phenolic content of complexes measured by Folin-Ciocalteu and ABTS methods. Anti-cancer effect of these compounds were tested against different cancer cells (A549, PC-3, HeLa and MCF-7). Apoptosis identified by the fluorescence imaging, caspase cleaved cytokeratin-18 and flow cytometry analysis (annexin V, caspase 3/7, mitochondria membrane potential and oxidative stress). As a result, Cu(II) complexes are more effective than the other compounds and Complex 3 is a promising anti-cancer compound against breast cancer MCF-7 and MDA-MB-231 cells (IC50values are 2.4 and 5.4µM for 48h, respectively). Flow cytometry analysis exhibited that Complex 3 caused apoptosis in MCF-7 cells. These results support that Complex 3 has anticancer activity and can be a potential anticancer agent especially in breast cancer.

Syntheses, Structures, and Magnetic Properties of Mixed-ligand Complexes of Co(II) Based on N-Heterocyclic and Different Carboxylate Ligands

Two novel transition-metal coordination polymers with the formulas [Co(L1)(bbi)(H2O)]n (1) and {[Co(L2)(phen)]·H2O}n (2) (H2L1 = 1,4-naphthalenedi- carboxylic acid, H2L2 = 5-OH-1,3-benzenedicarboxylic acid, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), phen = 1,10-phenanthroline) have been hydrothermally synthesized and characterized by techniques of single crystal X-ray diffraction, infrared spectra, elemental analysis, powder X-ray diffraction, and variable-temperature magnetic susceptibility measurements. X-ray crystal structure analyses reveal that complex 1 exhibits 2D framework with 4-connected sql topology and is further extended into a 3D supramolecular architecture via strong O–H···O and weak C–H···O hydrogen-bonding interactions, while complex 2 features a 1D ladder-like chain with a 3-connected (42·6) topological structure. Magnetic studies showed the presence of an antiferromagnetic interaction between adjacent Co(II) ions in both complexes. Two new mixed ligand complexes of cobalt based on N-heterocylic and carboxylate ligands were readily obtained and characterized. The topological structures, thermal stabilities and magnetic properties of which are observed and discussed.

The mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with coumarilic acid/1,10-phenanthroline

The coumarilate (coum−) and 1,10-phenanthroline (phen) mixed ligand complexes of Co(II) (1), Ni(II) (2) Cu(II) (3) and Zn(II) (4) were synthesized and structural characterizations were performed by using elemental analysis, magnetic susceptibility, solid-state UV–Vis, FTIR spectra, thermoanalytical TG-DTG/DTA and single-crystal X-ray diffraction methods. The Co(II) and Ni(II) complexes are salt-type compounds, and they have two moles phen ligands bound as bidentate, two moles aqua ligands in coordination sphere and two moles anionic coum− ligand outside of the coordination unit as the counter-ion of the molecular structure. At the same time, the Co(II) and Ni(II) complexes have five moles of aqua ligands as hydrated water outside of the molecules. It was obtained that Cu(II) and Zn(II) complex structures contain one mole of phen ligand, two moles coordinated (coum−) ligand and a one-mole aqua ligand, and the molecules (Cu(II) and Zn(II)) have fivefold structure and obey square pyramidal geometry. Thermal decomposition of each complex started with dehydration (the first removal is the dehydration of complex Co(II) and Ni(II) as removal of hydrate–aqua molecules), and then, the decomposition of organic parts was observed. The thermal dehydration of the complexes takes place in one (Cu(II) and Zn(II)) or two (Co(II) and Co(II)) steps. The decomposition mechanism, thermal decomposition steps and thermal stability of the investigated complexes provide useful data for the interpretation of their structures. The final decomposition products were found to be metal oxides. Some biological applications (antifungal/antibacterial) were performed using structurally characterized compounds.

Synthesis, characterization and biological screening studies of mixed ligand complexes using flavonoids as precursors

Flavonoids are a group of plant phenolics that provide various health benefits through cell signalling pathways and antioxidant effects. In the present study, a new series of mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) were synthesized by incorporating curcumin and quercetin flavonoid precursors. The structural features of the synthesized complexes were explored using elemental analysis, thermogravimetric analysis, UV–visible, infrared, NMR, mass and electron paramagnetic resonance spectral analyses and conductivity measurements. These data support an octahedral geometry of the synthesized complexes. In silico biological activity score for the ligand was predicted using PASS online software. ADMET properties were studied using VLS3D online software. Anti‐inflammatory and antioxidant activities were experimentally validated which prove that theoretical predictions are in agreement with the experimental results. Interestingly the synthesized complexes interact with calf thymus DNA through groove binding mode. Moreover, they have good potential to cleave pUC19 DNA. Minimum inhibitory concentration values of the synthesized complexes reveal that they have better antimicrobial efficacy than the ligands.

Mixed Ligand Complexes of Co(II) and Ni(II) Containing Organic Acids and Amine Bases as Primary and Secondary Ligands

The synthesis and characterization of mixed ligand complexes of Co(II) and Ni(II) have been described. Organic dibasic acid, malic acid plays role as primary ligand and Heterocyclic amine bases play role as secondary ligands in the complexes. Melting points, Elemental analysis, Magnetic susceptibility measurements, IR, UV and 1H-NMR spectral analysis were used in determining their physico-chemical properties. The prepared complexes of Co(II) and Ni(II) were found to form octahedral structure.

Studies on the Mixed Ligand Complexes of Co(II), Ni(II) and Cu(II) with Phthalimide and Heterocyclic Amines

This paper describes the synthesis and characterization of mixed ligand complexes of Co(II), Ni(II) and Cu(II) with, Phthalimide and heterocyclic amines. The Elemental analysis, IR, UV-vis and 1H-NMR spectral analysis, colours, molar conductances and magnetic properties suggested that the complexes have formulation as [M(Ph-imide)2(L)2~4], Where, M = Co(II), Ni(II) and Cu(II); Ph-imide = Phthalimide; L=Quinoline, Iso-quinoline, 2-Picoline and Pyridine. The prepared complexes of Co (II) and Ni (II) were octahedral and Cu (II) was square planar.

Synthesis, characterization and antimicrobial activities of mixed ligand transition metal complexes with isatin monohydrazone Schiff base ligands and heterocyclic nitrogen base

Mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with various uninegative tridentate ligands derived from isatin monohydrazone with 2-hydroxynapthaldehyde/substituted salicylaldehyde and heterocyclic nitrogen base 8-hydroxyquinoline have been synthesized and characterized by elemental analysis, conductometric studies, magnetic susceptibility and spectroscopic techniques (IR, UV–VIS, NMR, mass and ESR). On the basis of these characterizations, it was revealed that Schiff base ligands existed as monobasic tridentate ONO bonded to metal ion through oxygen of carbonyl group, azomethine nitrogen and deprotonated hydroxyl oxygen and heterocyclic nitrogen base 8-hydroxyquinoline existed as monobasic bidentate ON bonded through oxygen of hydroxyl group and nitrogen of quinoline ring with octahedral or distorted octahedral geometry around metal ion. All the compounds have been tested in vitro against various pathogenic Gram positive bacteria, Gram negative bacteria and fungi using different concentrations (25, 50, 100, 200μg/mL) of ligands and their complexes. Comparative study of antimicrobial activity of ligands, and their mixed complexes indicated that complexes exhibit enhanced activity as compared to free ligands and copper(II) Cu(LIV)(Q)⋅H2O complex was found to be most potent antimicrobial agent.

Physicochemical studies and biological activity of mixed ligand complexes involving bivalent transition metals with a novel Schiff base and glycine as a representative amino acid

The mixed-ligand complexes of Co(II), Ni(II), Mn(II) and Zn(II) with 2-aminomethyl thiophenyl-4-bromosalicylaldehyde Schiff base (ATS) and glycine as a representative example of amino acids have been achieved. These complexes namely [Ni(ATS)(Gly)] (1), [Co(ATS)(Gly)].H 2 O (2) [Mn(ATS)(Gly)].2H 2 O (3), and [Zn(ATS)(Gly)] (4) were characterized by elemental, molar conductance, infrared, magnetic moment, and electronic spectra. ATS behaves as mononegatively charged bidentate ligand with coordination through azomethine nitrogen and phenolate oxygen groups while glycine acts as monobasic bidentate ligand is coordinated via amino and ionized carboxylate group after deprotonation. The low molar conductance values suggest the non-electrolytic nature of these complexes. The magnetic and spectral data indicates a square planar geometry for Ni(II) complex, tetrahedral geometry for Zn(II) and octahedral geometry for both Mn(II) and Co(II) complexes. The isolated chelates have been screened for their antimicrobial activity.

Synthesis and Characterization of mixed ligand complexes of Co(II) ion with some N and S donor

Mixed ligand complexes of Co(II) ion with some heterocyclic nitrogen donors and 1,1-dicyanoethylene-2,2-dithiolate of the compositions, Co(N-N)2(i-MNT), Co(N-N)(i-MNT).2H2O and Co(N-N)(i-MNT)L2 (N-N = 1,10-phenanthroline, 2,2'-bipyridine ; i-MNT 2- = 1,1-dicyano- ethylene -2,2- dithiolate ; L = pyridine(py), -picoline (-pic), -picoline (-pic) or -picoline (-pic) have been isolated and characterized on the basis of analytical data, molar conductance, magnetic susceptibility, electronic and infrared spectral studies. The molar conductance data reveal non-electrolytic nature of the complexes in DMF. Magnetic moment values suggest low spin complexes. The electronic spectral data suggest distorted octahedral stereochemistry around Co(II) ion in these complexes. Infrared spectral studies suggest bidentate chelating behaviour of i-MNT 2- , 1,10-phenanthroline and 2,2'-bipyridine while other ligands show unidentate

Synthesis and Thermal Study of Co (II), Ni (II), Cu (II) Mixed Ligand Complexes Using Histidine As Tridentate Ligand

The mixed ligand complexes of Co (II), Ni (II) and Cu (II) with histidine (His.) and 8- hydroxyquinoline (Qui.) have been synthesized and characterized.The resulting complexes were characterized by vibrational and electronic spectral data, thermogravimetric studies , metal analysis and molar conductance measurements. The histidine acts as tridentate ligand, coordinating through the two nitrogen atoms of imidazole ring and the amino group and carboxylate oxygen whereas 8-hydroxyquinoline shows a bidentate nature and the coordination occurs through nitrogen of imine group and oxygen of phenol group. The experimental data suggest that a mononuclear octahedral structure with general formula (M (His.)(Qui.) H2O ) where M= Co (II), Ni (II) and (Cu (His.)(Qui.)H2O) .H2O, thermo gravimetric studies reveal the presence of coordinated water molecules in all complexes. The molar conductance measurements reveal non-electrolytic nature of complexes. Mixed ligand complexes of 8-hydroxyquinoline and o-hydroxybenzylidene-1-phenyl-2, 3-dimethyl-4-amino-3- pyrazolin-5-on with Fe (II), Co (II), Ni (II) and Cu (II) ions were synthesized , the molar conductivity of the complexes in DMF solution have non-electrolyte behavior and 8-hydroxyquinoline coordinate through the nitrogen and oxygen atoms. therefore, the complexes have tetrahedral configuration. (12) Several mixed ligand Ni(II),Cu(II) and Zn(II) complexes of 2- amino-3-hydroxypyridine(AHP) and imidazoles viz.,, imidazole (him), benzimidazole (bim), histamine(hist) and L- histidine(his) have been synthesized and characterized, the geometry becomes tetrahedral when mixed ligand complexes are fomed with him, bim and hist for Cu(II) and Zn(II). All Ni (II) and Cu (II) / Zn (II) histidine mixed ligand complexes have octahedral geometry.The complexes exhibited considerable amount of antibacterial activity and Cu (II) complexes cleave DNA yielding scission of the sugar- phosphate backbone . (13) Mixed ligand Zr(IV) complexes prepared with 8-hydroxyquinoline as a primary ligand and amino acids such as L-alanine/L - serine/glycine as a secondary ligand. Zr(II) was used due to its high coordination number and ability to form stable complexes. These complexes were characterized and screened for their antibacterial, antifungal and cytotoxic properties . (14) Kinetics and mechanism of thermal decomposition of o-vanilline-L-histidine complexes of some transition metal ions in which histidine acts as a tridentate ligand and an octahedral structure for the complexes has been reported . (15) Synthesis, structural, coordination and thermal stability studies of mixed ligand complexes of histidine with other ligands (adenine/guanine/ethylenediamine, diethylenetriamine or N,N,N , N ,, ,N ,,, -pentamethyldiethylenetriamine, glycine or L-alanine, histamine and diethylglyoxime) have been carried out .

Synthesis And Characterization Of Mixed Ligand Complexes Of Co(Ii) And Fe(Iii) Ions With Maleic Acid And Heterocyclic Amines

This paper describes the preparation and characterization of mixed ligand complexes of Co(II) and Fe(III) ions with maleic acid and heterocyclic amines of general formula [M(ME)L] and K[M(ME)L] (where M = Co(II) (1-4), Fe(III) (5-6); ME = C4H2O4 (1-4), 2C4H2O4 (5-6); L = C5H6N2 (1), C9H7N (2-3), C9H6NO (4), C5H5N.H2O (5), C6H7N (6)). The molecular structures of the complexes have been determined by spectral, magnetic studies and elemental analysis. Journal of Bangladesh Chemical Society, Vol. 25(2), 139-145, 2012 DOI: http://dx.doi.org/10.3329/jbcs.v25i2.15066

Synthesis and Characterization of Mixed Ligand Complexes of Co(II) and Fe(III) Ions with Malic Acid and Heterocyclic Amines

This paper describes the preparation and characterization of mixed ligand complexes of Co(II) and Fe(III) ions with malic acid and heterocyclic amines. The general formula of the complexes are as follows: [M(MA)L2] and K[M(MA)2L2] (where, M = Co(II) (1-4), Fe(II) (5-8); MA = C4H4O5 (1-4), 2C4H4O5 (5-8); L = C6H5N (1), C6H7N (2), C9H7N (3, 4), 2C6H5N (5), 2C6H7N (6), 2C9H7N (7-8). The complexes were prepared in the solid form and characterized by elemental analysis, conductivity and magnetic measurements, infrared and electronic spectroscopic studies. The infrared spectra of the complexes confirmed the coordination of metal ion with ligands. The Co(II) complexes are assumed to have tetrahedral and the Fe(III) complexes have octahedral structure based on the electronic spectra and magnetic measurements. Their antibacterial and antifungal activity has also been evaluated by the disc diffusion methods against fourteen pathogenic bacteria (five gram positive and nine gram negative) and fourteen fungi. Complexes [Co(II)(MA)(4-pico)2] showed the highest antibacterial activity against all bacteria tested (when, MA= C4H4O5 and 4-pico = C6H7N). DOI: http://dx.doi.org/10.3329/bpj.v15i2.12589 Bangladesh Pharmaceutical Journal 15(2): 177-181, 2012

Mixed ligand complexes of essential metal ions with L-glutamine and succinic acid in SLS-water mixtures

Speciation of mixed ligand complexes of Co(II), Ni(II) and Cu(II) with L-glutamine and succinic acid was studied in varying amounts (0.0-2.5% w/v) of sodium lauryl sulphate in aqueous solutions maintaining an ionic strength of 0.16 mol L-1 (NaCl) at 303.0 K. Titrations were carried out in the presence of different relative concentrations (M : L : X = 1 : 2 : 2, 1 : 4 : 2, 1 : 2 : 4) of metal (M) to L-glutamine (L) to succinic acid (X) with sodium hydroxide. Stability constants of ternary complexes were refined with MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The species detected were ML2X, MLX, MLXH and MLXH2 for Co(II), Ni(II) and Cu(II). Extra stability of ternary complexes compared to their binary complexes was believed to be due to electrostatic interactions of the side chains of ligands, charge neutralization, chelate effect, stacking interactions and hydrogen bonding. The species distribution with pH at different compositions of SLS and plausible equilibria for the formation of species were also presented.

Synthesis, Characterization and Antimicrobial Activity of Mixed Schiff Base Ligand Complexes of Co(II), Ni(II), Cu(II) and Zn(II)

The mixed ligand complexes of Co(II), Ni(II), Cu(II) and Zn(II) with Schiff bases N‐(2‐hydroxy‐1‐naphthylidene)‐4‐methylaniline (L1H) and N‐(2‐hydroxybenzylidene)‐2,3‐dimethylaniline (L2H) have been synthesized and characterized. The resulting complexes were characterized by elemental analysis, thermogravimetric analysis, magnetic moment measurements, conductivity measurements, 1H NMR, IR, UV‐visible and ESR spectral studies. The Schiff bases acts as bidentate monobasic ligands, coordinating through deprotonated phenolic oxygen and azomethine nitrogen atoms. The complexes are non‐electrolytic in DMSO. The presence of the two coordinated water molecules in these complexes was indicated by IR spectra and thermogravimetric analysis of the complexes. From the analytical and spectral data the stoichiometry of these complexes have been found to be [M(L1)(L2)(H2O)2] {where M = Co(II) , Ni(II), Cu(II) and Zn(II)}. It is found that Co(II), Ni(II), Cu(II) and Zn(II) complexes exhibited octahedral geometry. The antimicrobial activities of ligands and their mixed ligand complexes were screened by disc diffusion method. It is found that the metal complexes have higher antimicrobial activity than the free ligand.