Abstract

A series of three metal complexes of the 3-benzoyl-7-methoxycoumarin ligand have been synthesized and characterized by elemental analyses, molar conductance, Fourier-transform infrared spectroscopy, thermogravimetric analysis, electron paramagnetic resonance, proton nuclear magnetic resonance spectroscopy and cyclic voltammetry techniques. The infra-red spectra of the ligand and its complexes showed that the ligand behaved as a bidentate and confirmed the presence of nitrate ions in the coordination sphere. Thermal stability of the complexes was studied using thermogravimetric and differential thermal analysis, which supported the presence of nitrate ions in these complexes. All complexes exhibited an octahedral geometry around the metal center. The redox property of the metal complexes was studied cyclic voltametrically, which showed that all the complexes exhibited quasi-reversible nature. Antimicrobial studies of these metal complexes and the ligand were conducted against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Aspergillus niger and Candida albicans species. Metal complexes exerted greater antimicrobial activities compared to the ligand. The optimized structure of the zinc complex of coumarin derivative was obtained using DFT/RB3LYP method with 6-311G++G (d,p) basis set. Density functional theory calculations were performed for the determination of geometry structure and vibrational assignments for the zinc complex.