Synthesis,characterization, structural investigation,and antimicrobial studies of mononuclear Zn(II), Cd(II), and Ag(I) complexes of an N3O Schiff base

An N₃O Schiff base (L), 1?:?1 condensate of benzil monohydrazone and 4-pyridine carboxaldehyde, and its Zn(II), Cd(II), and Ag(I) complexes were synthesized and characterized by elemental analyses and various spectroscopic techniques. The crystal structures of [ZnL₂Br₂] (1), [CdL₂I₂]·CH₂Cl₂, (2)·CH₂Cl₂, and [Ag(L)₂]ClO₄ (3) have been determined using X-ray crystallography. The Zn(II) and Cd(II) complexes show a tetrahedral configuration whereas in the asymmetric unit of 3, two independent coordination units of Ag(I) are present. Carbonyl–silver interaction, weak C–H?O interaction, and also π–π interaction are present in 3 in the solid state. The synthesized complexes have antibacterial activity against Klebsiella pneumoniae 114, Escherichia coli K88, Salmonella typhi ATCC 34, Bacillus subtilis UC564, and Staphylococcus aureus ATCC25923. The results showed that in some cases the antibacterial activities of the complexes were comparable to standard antibiotics Tetracycline and Streptomycin. The antifungal activities of the complexes were also studied for Aspergillus niger, Aspergillus oryzae, Penicillium notatum, and Saccharomyces cerevisiae. MIC values of 1, 2·CH₂Cl₂, and 3 are less than the Nystatin standard.     

Synthesis,spectral characterization and structural investigation on some 4-aminoantipyrine containing Schiff base Cu(II) complexes and their molecular association

Compounds [Cu(L₁)₂] (1) and [Cu(L₂)₂] (2), where L₁ and L₂ are Schiff base ligands of 4-aminoantipyrine and substituted salicylaldehydes, were synthesized and characterized using various spectroscopic techniques such as elemental analysis, UV–Vis, IR, and NMR. The single crystal X-ray structures for L₁, L₂, and their corresponding Cu(II) complexes assembled in a 1:2 metal to ligand ratio were analyzed for their various weak H-bonding and dimeric association. The structural analysis of compounds 1 and 2, being the first crystal structures in this series, deserves special attention to help further the understanding in this area of structure–reactivity correlation studies. Further these compounds, composed of very similar chemical composition with a small difference in the substituent on the salicylaldehyde moiety, influenced through various weak inter- and intramolecular H-bonding and C–H?π interactions, rearrange the geometry around Cu(II) from a tetrahedrally distorted square planar geometry in [Cu(L₁)₂] (1) to square planar in [Cu(L₂)₂] (2). Steric strain imposed by the methyl substitution on the 4-aminoantipyrine moiety of the Schiff base ligand, causing this small change of the Cu(II) geometry, along with various weak interactions is analyzed in detail.     

Synthesis, characterization and spectra studies on Zn(II) and Cu(II) complexes with thiocarbamide ligand containing Schiff base group

The ligand of 4-phenyl-1-(1-phenylethylidene)thiosemicarbazide (HL) and its metal complexes of ZnL₂ (1) and CuL₂ (2) have been synthesized. Elemental analysis, IR and X-ray single crystal diffraction characterizations for 1 and 2 have been carried out. In the complexes 1 and 2, the central metallic ions Zn²⁺ and Cu²⁺, coordinate with two deprotonated ligands, L⁻, respectively and adopt distorted tetrahedral geometries. The thermal analyses result shows that the two complexes undergo two similar decomposition processes because of their similar geometric configurations. For the two complexes, UV–Vis spectra have been measured and DFT calculations at B3LYP/LANL2DZ level of theory prove that the electronic spectra of 1 are corresponding with intraligand electronic transitions, and the electronic spectra of 2 are attributed to intraligand electronic transitions as well as d–d electronic transitions. Fluorescence spectra measurements indicate that the complex of 1 emits stronger fluorescence than the ligand of HL, and the complex 2 does not emit fluorescence at all. Electrochemical analyses reveal that both the oxidation peak currents and the reduction peak currents of 1 and 2 are stronger than those of the ligand, respectively.     

Synthesis,spectral characterization,theoretical, antimicrobial,DNA interaction and in vitro anticancer studies of Cu(II) and Zn(II) complexes with pyrimidine-morpholine based Schiff base ligand

Novel Cu(II) (1) and Zn(II) (2) complexes with 4-(1-(4-morpholinophenyl)ethylideneamino)pyrimidine-5-carbonitrile) (L) have been synthesized and characterized by various spectroscopic and analytical techniques. DFT (density functional theory) studies result confirms that, LMCT mechanism have been done between L and M(II) ions. The antimicrobial studies indicate that the ligand L and complexes 1 & 2 exhibit higher activity against the E. coli bacteria and C. albicans fungi. The groove binding mode of ligand L and complexes 1 & 2 with CT-DNA have been confirmed by electronic absorption, competitive binding, viscometric and cyclic voltammetric studies. The electronic absorption titration of ligand L and complexes 1 & 2 with DNA have been carried out in different buffer solutions (pH 4.0, 7.0 & 10.0). The K_b values of ligand L and complexes 1 & 2 are higher in acidic buffer at pH 4.0 (K_b = 2.42 × 10⁵, L; 2.8 × 10⁵, 1; 2.65 × 10⁵, 2) and the results revealed that, the interaction of synthesized compounds with DNA were higher in the acidic medium than basic and neutral medium. Furthermore, CT-DNA cleavage studies of ligand L and complexes 1 & 2 have been studied. The in vitro anticancer activities results show that complexes 1 & 2 have moderate cytotoxicity against cancer cell lines and low toxicity on normal cell line than ligand L.     

Synthesis,crystal feature and spectral characterization of paeonol derived Schiff base ligands and their Cu(II) complexes with antimicrobial activity

Four novel Schiff bases PNL-4OMe, PNL-4Br, PNL-4F, PNL-3,4-F₂, and their copper(II) complex with [M(L)₂(H₂O)₂] arrangement was synthesized using Paeonol and various aromatic substituted amines. Characterization has been done through FT-IR, ESI Mass, TG-DTA, DFT, magnetic measurements, elemental analysis, and Thermogravimetric analysis. Paeonol derived new bond formation in Schiff bases and changes in frequencies during complexation have been confirmed through FT-IR spectra. All complexes are thermally stable, paramagnetic, and have non-electrolytic behavior. The antimicrobial activity was also tested against Gram-positive bacteria; S. aureus, B. subtilis, and Gram-negative bacteria; E. coli, P. aeruginosa. Single-crystal X-ray data provide evidence that PNL-3,4-F₂ is recrystallizing in a triclinic system with P-1(2) space group and confirms the intramolecular H-bonding and short Vander Waal type interactions. Non-covalent interactions and π … π stacking surface interactions in PNL-3,4-F₂ were studied with Hirshfeld analysis. H-atoms have the highest interactions with other atoms of neighbouring molecules compared to all other atoms. DFT calculations were performed on the electronic structure of ligand PNL-3,4-F₂ and its copper(II) complex and discussed.     

Synthesis, reactivity and structural characterization of ytterbium complexes bearing a tridentate [O,N,N] Schiff base ligand

The synthesis, characterization and reactivity of ytterbium monochloride supported by tridentate Schiff base ligands are described. The metathesis reaction of anhydrous YbCl₃ with 1 equivalent of the sodium salt of a Schiff base, [{LNa(THF)}₂] (1) [LH = 3,5-Bu^t₂-2-(OH)-C₆H₂CHN-8-C₉H₆N], gave the ytterbium Schiff base monochloride complex L₂YbCl (2). Complex 2 reacted with NaOAr (OAr = OC₆H₃Bu^t-2-Me-4) in a 1:1 molar ratio to form the desired aryloxo derivative L₂Yb(OAr) (3). Complex 3 can also be prepared by the one-pot reaction of the Schiff base HL, n-BuLi, YbCl₃ and NaOAr in a 2:2:1:1 molar ratio. However, an unprecedented ytterbium aryloxide LL′Yb(OAr) (4) (L′ = 3,5-Bu^t₂-2-(O)C₆H₂CH(C₄H₉)-NH-8-C₉H₆N) can be isolated in low yield as a byproduct in the later case. Reaction of complex 2 with 1 equivalent of (CH₂CH-CH₂)MgBr in THF afforded the unexpected complex [Mg(H₂N-8-C₉H₆N)Cl(THF)₃]Br (5). Complexes 2-5 were fully characterized by elemental analysis and X-ray diffraction.     

Crystal feature and spectral characterization of Zn(II) complexes containing Schiff base of Acylpyrazolone ligand with antimalarial action

With association of acylpyrazolones and benzhydrazide, two novel Ligands BZ-PCBMCPMP ((Z)-N'-((4-chlorophenyl) (1-(3-chlorophenyl) 3-methyl-5-oxo-1,5-dihydro-4H-pyrazol-4-ylidene) methyl) benzohydrazide) and BZ-PCBPMP ((Z)-N'-((4-chlorophenyl) (1-phenyl) 3-methyl-5-oxo-1,5-dihydro-4H-pyrazol-4-ylidene) methyl) benzohydrazide)) with different O–N–O fashion were synthesized via Schiff base reaction, which on complexation with Zn(II) acetate dihydrate yields novel [Zn(BZ-PCBMCPMP)₂] and [Zn-(BZ-PCBPMP)₂] complexes with distorted octahedron framework. Structure elucidation was performed through several spectroscopic techniques such as FTIR, ¹H-NMR, ¹³C NMR, TG-DTA, UV/Vis, and Single-crystal XRD. The non-electrolytic nature was confirmed through molar-conductance values. Single crystal X-ray study of the BZ-PCBPMP ligand shows intramolecular as well as intermolecular hydrogen bonding, giving rise to a H-bonded dimer. In [Zn-(BZ-PCBPMP)₂] one ligand is symmetrically coordinating while the other is asymmetrically coordinating to the Zinc atom. Antimalarial property of ligands and complexes was also discovered by its efficient MIC activity against Chloroquine sensitive P. falciparum.     

Synthesis, characterization and biological evaluation of mononuclear Co(II), Ni(II), Cu(II) and Pd(II) complexes with new N2O2 Schiff base ligands

New tetradentate N(2)O(2) donor Schiff bases and their mononuclear Co(II), Ni(II), Cu(II), and Pd(II) complexes were synthesized and characterized extensively by IR, (1)H-, (13)C-NMR, mass, ESR, conductivity measurements, elemental and thermal analysis. Specifically the magnetic and electronic spectral measurements demonstrate the octahedral structures of cobalt(II), nickel(II) complexes and square planar geometries of copper(II), palladium(II) complexes. All the ligands and complexes were screened for their in vitro antibacterial activity against two gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) and two gram-negative bacteria (Escherichia coli, Klebsiella pneumonia). In this study, Pd(II) complexes exhibited potent antibacterial activity against B. subtilis, S. aureus whereas other metal complexes also exerted good activity towards all tested strains even than standard drugs streptomycin and ampicillin.     

Synthesis, characterization and antioxidant activity of naringenin Schiff base and its Cu(II), Ni(II), Zn(II) complexes

A new ligand, naringenin-2-hydroxy benzoyl hydrazone (H(5)L), was prepared by condensation of naringenin with 2-hydroxy benzoyl hydrazine. Its Cu(II), Ni(II), Zn(II) complexes have also been synthesized and characterized on the basis of (1)H-NMR, IR, UV-Vis spectra, elemental analyses, molar conductivity and thermal analyses. The general formula of these complexes was M(H(3)L) [M=Cu(II), Ni(II) and Zn(II)]. In addition, the antioxidant activities (superoxide and hydroxyl radical) of the free ligand and its complexes were determined in vitro. These compounds were found to possess potent antioxidant activity and be better than standard antioxidants like vitamin C and mannitol. In particular, the Cu(II) complex displayed excellent activity on the superoxide radical.     

Synthesis, structural and spectral studies of Cu(II) and V(IV) complexes of a novel Schiff base derived from pyridoxal. Antimicrobial activity

A novel Schiff base, N-(4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one)pyridoxaldimine (HL·HCl), was prepared and structurally characterized on the basis of elemental analyses, ¹H and ¹³C NMR, and IR spectral data. The synthesis and characterization of several Cu(II) (1-6) and V(IV) (7) complexes with N-(4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one)pyridoxaldimine are reported. The composition and structures of the copper(II) and vanadium(IV) complexes were proposed based on elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic and EPR spectroscopy. In addition, the structures of the ligand and the complex [CuL(H₂O)₂]NO₃·2.25H₂O (1) have been determined by single-crystal X-ray diffraction, showing that the Cu(II) center has a distorted square-pyramidal geometry. The ligand and the complexes were also tested for their in vitro antibacterial activity.     

Synthesis and characterization of Co(II), Ni(II), Cu(II) and Zn(II) complexes of tridentate Schiff base derived from vanillin and DL-alpha-aminobutyric acid

Co(II), Ni(II), Cu(II) and Zn(II) complexes of the Schiff base derived from vanillin and dl-alpha-aminobutyric acid were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements, powder XRD and biological activity. The analytical data show the composition of the metal complex to be [ML(H(2)O)], where L is the Schiff base ligand. The conductance data indicate that all the complexes are non-electrolytes. IR results demonstrate the tridentate binding of the Schiff base ligand involving azomethine nitrogen, phenolic oxygen and carboxylato oxygen atoms. The IR data also indicate the coordination of a water molecule with the metal ion in the complex. The electronic spectral measurements show that Co(II) and Ni(II) complexes have tetrahedral geometry, while Cu(II) complex has square planar geometry. The powder XRD studies indicate that Co(II) and Cu(II) complexes are amorphous, whereas Ni(II) and Zn(II) complexes are crystalline in nature. Magnetic measurements show that Co(II), Ni(II) and Cu(II) complexes have paramagnetic behaviour. Antibacterial results indicated that the metal complexes are more active than the ligand.     

Synthesis, characterization and structural studies of diorganotin(IV) complexes with Schiff base ligand salicylaldehyde isonicotinylhydrazone

Eight diorganotin(IV) complexes of salicylaldehyde isonicotinylhydrazone (H₂SalN) R₂Sn(SalN) R = t-Bu 1, Ph 2, PhCH₂3, o-ClC₆H₄CH₂4, p-ClC₆H₄CH₂5,m-ClC₆H₄CH₂6,o-FPhCH₂7, p-FC₆H₄CH₂8 were prepared. All complexes 1-8 have been characterized by elemental, IR, ¹H, ¹³C and ¹¹⁹Sn NMR analyses. The crystal structures of H₂SalN and complex 1 were determined by X-ray crystallography diffraction analyses. Studies show that H₂SalN is a tridentate planar ligand. For complex 1, the tin atom lies in this plane and forms a five- and six-membered chelate ring with the tridentate ligand. A comparison of the IR spectra of the ligand with those of the corresponding complexes, reveals that the disappearance of the bands assigned to carbonyl unambiguously confirms that the ligand coordinate with the tin in the enol form.     

Synthesis,characterization and biological studies of some Co(II), Ni(II) and Cu(II) complexes derived from indole-3-carboxaldehyde and glycylglycine as Schiff base ligand

The Schiff base ligand derived from indole-3-carboxaldehyde(indal) and glycylglycine(glygly) were synthesized and characterized by elemental analysis, IR, electronic spectrum, ¹H NMR and mass spectrum. Co(II), Ni(II) and Cu(II)–indal-glygly Schiff base complexes were synthesized and characterized by elemental analysis, molar conductance, IR, electronic spectra, magnetic measurements, ESR, electrochemical studies, TGA, DSC analysis, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR spectral data show that the ligand is tridentate and the binding sites are azomethine nitrogen, peptide nitrogen and carboxylato oxygen atoms. Electronic spectral measurements indicate tetrahedral geometry for Co(II) and Ni(II) complexes and square planar geometry for Cu(II) complex. Magnetic measurements show weak ferromagnetic behaviour for Co(II) and Ni(II) complexes and paramagnetic behaviour for Cu(II) complex. ESR spectral data shows the ionic link between metal and the Schiff base ligand. The metal complexes are found to be stabilized in the unusual oxidation states of the metal ion during electrolysis. Thermal analysis of the complex indicates that the decomposition takes place in three steps. IR and thermal studies indicate that the fourth position would be occupied by a water molecule in complexes. XRD shows that the complexes have the crystallite size of 31, 40 and 67 nm, respectively. The surface morphology of the complexes was studied by SEM. The antimicrobial activity of the ligand and its complexes were screened by Kirby Bayer Disc Diffusion method. DNA cleavage studies were performed for metal–Schiff base complexes in presence of hydrogen peroxide as oxidant.     

Mixed ligand Cu(II) complexes containing o-vanillin-l-tryptophan Schiff base and heterocyclic nitrogen bases: synthesis,structural characterization,and biological properties

[Cu(L)] (1) and mixed ligand copper(II) complexes [Cu(L)(A)] (2 and 3), where L is the Schiff base derived from o-vanillin and l-tryptophan and A is pyridine (2) and imidazole (3), were synthesized and characterized using conventional and spectral techniques. 2 was structurally characterized using single crystal X-ray crystallography showing that Cu(II) is coordinated through N₂O₂ donors in a square plane. The EPR spectra of the complexes in frozen solution support a square-based structure. Electrochemical behavior of the complexes has been studied by cyclic voltammetry. The DNA-binding properties of L and 1–3 with calf thymus DNA were investigated by spectral and kinetic methods. For all the complexes, the maximum value of binding constant (0.38 × 10⁶) was achieved with 3 by spectroscopic titration. The ability of compounds to break pUC19 DNA was checked by gel electrophoresis. The ligand and copper complexes exert cytotoxicity against MCF-7 cell line.     

Synthesis and spectroscopic studies of mononuclear mixed ligand Schiff base complexes of Cu(II) involving conjugated heterocyclic nitrogen base and N-phOHA or N-phDHA

Mononuclear complexes of Cu(II) have been prepared by reacting a 1:1:1 molar ratio of N- phOHA or N-phDHA, dipy or phen and cupric chloride where, N-phOHA = N-phenyl-O-hydroxyacetophenonimine, N-phDHA = N-phenyl-2,4-dihydroxy acetophenonimine, dipy = 2,2′-bipyridil, phen = 1,10-phenanthroline. All complexes were characterized on the basis of their microanalysis data, molar conductance, magnetic moment at room temperature, UV-Vis, IR, ¹H NMR, and ESR spectra. The monomeric and ionic nature of complexes was confirmed by their magnetic moment data and molar conductance values. The ESR spectra of metal chelates in polycrystalline and solution state at 300 K and 77 K were recorded and their silent features are reported. The ESR spectra of the metal chelates provided information about their structure on the basis of Hamiltonian parameters of the complexes and also degree of covalency.     

Synthesis, spectroscopic characterization and DNA nuclease activity of Cu(II) complexes derived from pyrazolone based NSO-donor Schiff base ligands

Two neutral mononuclear Cu(II) complexes have been prepared in EtOH using Schiff bases derived from 4-toluoyl pyrazolone and thiosemicarbazide. Both the ligands have been characterized on the basis of elemental analysis, IR, (1)H NMR, (13)C NMR and mass spectral data. The molecular geometry of one of these ligands has been determined by single crystal X-ray study. It reveals that these ligands exist in amine-one tautomeric form in the solid state. Microanalytical data, Cu-estimation, molar conductivity, magnetic measurements, IR, UV-Visible, FAB-Mass, TG-DTA data and ESR spectral studies were used to confirm the structures of the complexes. Electronic absorption and IR spectra of the complexes suggest a square-planar geometry around the central metal ion. The interaction of complexes with pET30a plasmid DNA was investigated by spectroscopic measurements. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the copper(II) complexes can cleave circular plasmid DNA to nicked and linear forms.     

Synthesis,characterization and bioactivity of Schiff base copper(II) complexes derived from L-glutamine and L-asparagine

To investigate the structure–activity relationship of L-glutamine and L-asparagine Schiff base copper complexes in applications, L-glutamine and L-asparagine Schiff bases (GV and AV) and their copper complexes [Cu₃(GV)₂(CH₃COO)₂(H₂O)] · 2H₂O (GVC) and [CuAV(H₂O)₃] (AVC) have been synthesized and characterized by molar conductance, elemental analysis, UV-Vis, IR, ¹H-NMR, and TG-DTG. We examined the geometries of GV, AV, GVC, and AVC through Hartree–Fock method and electronic absorption spectra. We also tested their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Bacillus subtilis bacteria and antiproliferation activity on human breast cancer MDA-MB-231 cells. The side chain difference between L-glutamine and L-asparagine results in different geometry of GV and AV, which leads to different geometry of GVC and AVC. GVC, a trinuclear Cu(II) complex, shows the highest antibacterial activity and the highest growth inhibition activity on MDA-MB-231 cells. Our results suggest that GVC has potential as an antibacterial and anticancer agent.     

Synthesis,structures, and property studies on Zn(II), Ni(II), and Cu(II) complexes with a Schiff base ligand containing thiocarbamide group

A Schiff base ligand containing thiocarbamide group of 4-phenyl-1-(4-methoxyl-1-phenylethylidene)thiosemicarbazide (HL) and its three mononuclear metal complexes of ZnL₂ (1), NiL₂ (2), and CuL₂ (3) have been synthesized. Elemental analysis, IR, and X-ray single crystal diffraction characterizations for the ligand and the three complexes have been carried out. In the three complexes, the central metallic ions of Zn²⁺, Ni²⁺, and Cu²⁺ coordinate with two deprotonated ligands of L⁻, respectively. In 1, Zn²⁺ ion adopts a distorted tetrahedral geometry, while in 2 and 3, both the Ni²⁺ and Cu²⁺ ions possess distorted square planar configurations. For the four compounds, UV–Vis spectra have been measured and DFT calculations at B3LYP/LANL2DZ level of theory prove that the electronic spectra of HL and 1 are corresponding with electronic transitions of n → π* and π → π* in the ligand itself and the electronic spectra of 2 and 3 are attributed to intraligand electronic transitions as well as d–d electronic transitions. Electrochemical investigations reveal that the different metal–ligand interactions have changed the peak shapes and peak locations, which are corresponding with the DFT-B3LYP/LANL2DZ calculational results. Fluorescence spectra measurements indicate that the ligand emits purple fluorescence and the complex 1 emits stronger blue fluorescence, while the complexes 2 and 3 quench fluorescence. The thermal analyses result show that the three complexes undergo two similar decomposition processes because of their similar geometric configurations.     

Synthesis of alkynylated photo-luminescent Zn(II) and Mg(II) Schiff base complexes

A new series of photo-luminescent Zn(II) and Mg(II) Schiff base complexes were prepared by treatment of the arylethynyl-substituted salicylaldehydes obtained from the Sonogashira reaction with the metal salt followed by addition of the different diamines. Most square-planar Zn(II) complexes exhibited good quantum efficiencies. The Mg(II) complexes displayed even higher quantum yields than the corresponding Zn-complexes. Unsymmetrical Zn(II) Schiff base complexes were also successfully prepared from organic monoimines obtained as intermediates in the formation of the Mg metal Schiff base complex. The monoimine can also be prepared from the reaction of salicylaldehydes with excess diaminoarene. Two crystal structures featuring the zinc atom are reported, one with a rare four-coordinate square planar geometry and the other with a five-coordinate square pyramidal geometry.     

Synthesis,characterization and electrochemical properties of copper(II) complexes derived from succinoyldihydrazine Schiff base ligands

Four new copper(II) complexes of the composition [Cu(H₂L)(H₂O)] have been synthesized by template method from reaction of copper(II) acetate, succinoyldihydrazine and some o-hydroxy aromatic aldehydes and ketones in aqueous methanol media. The composition of the complexes has been established on the basis of data obtained from analytical and mass spectral studies. The structure of the complexes has been discussed in the light of molar conductance, magnetic moment, Uv-vis, EPR and IR spectral studies. All of the complexes are non-electrolyte in DMSO. The μ_eff values for the complexes fall in the region 1.76–1.85 BM which rules out the possibility of any M–M interaction in the structural unit of the complexes. The ligands coordinate to the metal centre in enol form through phenolate/naphtholate oxygen atoms and azomethine nitrogen atoms. The NMR spectra show that ligands are present in anti-cis configuration in uncoordinated state. In all of the complexes the copper centre adopts square pyramidal stereochemistry. The unpaired electron is present in $d_{x^2-y^2}$ orbital in the ground state for copper centre in the complexes. The electron transfer reactions for the complexes have been studied by cyclic voltammetry.