Synthesis, Spectroscopic, and Electrochemical Studies on Some New Copper(II) Complexes Containing 2-[(Z)-Phenyl (Pyridine-2-yl) Methylidene] AminoBenzenethiol and Monodentate Ligands
Five new mononuclear copper(II) complexes, namely, [Cu(L)(ImH)]·ClO41; [Cu(L)(Me-ImH)]·ClO42; [Cu(L)(Et-ImH)]·ClO43; [Cu(L)(2-benz-ImH)]·ClO44; [Cu(L)(benz-ImH)]·ClO45, where HL？=？2- [(Z)-phenyl (pyridine-2-yl) methylidene] amino benzenethiol; ImH？=？Imidazole; Me-ImH？=？Methy-limidazole; Et-ImH？=？Ethyl-imidazole; 2-benz-ImH？= 2-methyl-benzimidazole; benz-ImH？=？benz-imidazole, have been synthesized and characterized by various physicochemical and spectroscopic techniques. Magnetic moments, electronic spectra, and EPR spectra of the complexes suggested a square planar geometry around Cu(II) ion. The synthesized HL ligand behaves as monobasic tridentate Schiff base bound with the metal ion in a tridentate manner, with N2S donor sites of the pyridine-N, azomethine-N, and benzenethiol-S atoms. The redox behaviour of the copper complexes has been studied by cyclic voltammetry. Superoxide dismutase activity of these complexes has been revealed to catalyse the dismutation of superoxide ( ) and IC50 values were evaluated and discussed. 1. Introduction Transition metal complexes coordinated to tridentate Schiff base ligands have been studied extensively mainly because of their ease of preparation, flexibility, and versatility in terms of chemical properties, geometry, coordination sites, and ease of substitution. Ternary complexes formed between metal ions and two different types of bioligands, namely, heteroaromatic nitrogen bases and Schiff base, may be considered as models for substrate metal ion-enzyme interactions and other metal ion mediated biochemical interactions. Among those compounds, copper(II) complexes with Schiff base ligands have been of great interest due to their importance as essentially biologically active [1–4] models for metalloproteins [5, 6]. Copper is an important trace element for plants and animals and is involved in mixed ligand complex formation in a number of biological processes [7]. Imidazole and its derivatives are very important from a biological point of view [8]; namely, benzimidazole as the 5,6-dimethyl derivative is present in vitamin B12 and related biomolecules [9] and other benzimidazole compounds have found wide use as anthelmintic agents for both human and veterinary purposes [10]. In addition, it has been reported that several copper complexes with benzimidazole derivatives show inhibitory effects on helminth parasites [11]. Imidazole is also one of the most biologically important ligands. It behaves like a monodentate ligand at lower pH and at higher pH it serves as a bridging ligand. The deprotonated from of imidazole
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