Synthesis, crystal structure, electrochemistry and studies on protein binding, antioxidant and biocidal activities of Ni(II) and Co(II) hydrazone complexes

Bivalent transition metal hydrazone complexes of the composition [Ni(L-1)(2)] (1), [Co(L-1)(2)] (2), [Ni(L-2)(2)] (3) and [Co(L-2)(2)] (4) have been synthesised from the reactions of [MCl2(PPh3)(2)] (where M = Ni or Co) with hydrazones derived from 2-acetyl pyridine and carboxylic acid hydrazides of benzhydrazide (HL1) or thiophene-2-carboxylic acid hydrazide (HL2), respectively. Structure of the ligands HL1 and HL2 and their corresponding complexes with Ni(II) and Co(II) ions were proposed based on the elemental analysis, infrared and H-1 NMR spectral methods. Single crystal X-ray diffraction study of complex 1 revealed a distorted octahedral geometry around the metal ion provided by two units of the ligand. To explore the potential medicinal value of the new complexes, binding interaction of all the complexes with bovine serum albumin (BSA) was studied at normal physiological conditions using fluorescence and UV-Vis spectral techniques. The number of binding sites (n) and binding constant (K-a) were calculated according to the double logarithm regression equation. The results of synchronous fluorescence spectrum showed that binding of metal hydrazones with BSA induced conformational changes in BSA. The in vitro antioxidant and antimicrobial potentials of the new chelates were also carried out. (C) 2011 Elsevier Ltd. All rights reserved.