Abstract
This study was conducted to prepare novel azomethine chelates of Cu(II), Pd(II), Zn(II) and Cr(III) with tridentate dianionic azomethine OVAP ligand 2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol. The prepared compounds were characterized using elemental analyses and spectral, conductivity, magnetic and thermal measurements. The spectroscopic data suggest that the parent azomethine ligand binds to the investigated metal ions through both deprotonated phenol oxygen and azomethine nitrogen atoms, and adopts distorted octahedral geometry in the case of Cr(III) and Cu(II) ions while tetrahedral and square planar geometries for Zn(II) and Pd(II) ions, respectively. In order to confirm the molecular geometry of the investigated azomethine chelator and its complexes, theoretical density functional theory calculations were employed. Correlation between experimental observations and theoretical calculations of geometry optimization results are in a good agreement. Absorption titration was used to explore the interaction of the investigated azomethine metal chelates with calf thymus DNA, and the binding constant as well as Gibbs free energy were evaluated. Viscosity measurements and gel electrophoresis studies suggest intercalative and replacement binding modes of the azomethine metal chelates with calf thymus DNA. Additionally, the antimicrobial activity of the complexes was screened against some pathogenic bacteria and fungi. This biological study shows that the complexes exhibit a marked inhibitory effect compared to the corresponding ligand and standard drugs. Furthermore, the effect of the novel compounds as antioxidants was determined by reduction of 1,1-diphenyl-2-picrylhydrazyl and compared with that of vitamin C. Finally, in vitro cell proliferation via MTT assay was investigated against colon carcinoma cells (HCT-116), hepatic cellular carcinoma cells (HepG-2(and breast carcinoma cells (MCF-7) to calculate the cytotoxicity of the prepared compounds. Cell proliferation is inhibited for all compounds and in a dose-dependent manner in the sequence of OVAPPd > OVAPCu > OVAPZn > OVAPCr > OVAP azomethine ligand.