Synthesis, structure, antioxidant and SOD-mimetic activity of [Cu(xanthurenate)(nicotinamide)(H2O)] complexes

Abstract

This study reports the synthesis of novel mixed ligand complexes of copper(II) with the xanthurenate anion (Xan2−) and nicotinamide ligand (NA): [Cu(Xan)(NA)(H2O)]·H2O and [Cu(Xan)(NA)(H2O)]·3H2O. The compounds were characterized by single crystal X-ray diffraction, IR spectroscopy, and thermal analysis. The first coordination sphere of copper(II) in [Cu(Xan)(NA)(H2O)] consists of a water molecule, a nicotinamide ligand coordinated via the pyridine nitrogen and a xanthurenate dianion coordinated in a tridentate manner via carboxylate oxygen, nitrogen, and phenolate oxygen. The five donor atoms define a distorted square pyramid whose apex is occupied by the aqua ligand. The antioxidant activities of the compounds were investigated by the 2,2-diphenyl-1-picrylhydrazyl scavenging method, which showed that the IC 50 values for both compounds are higher than for related [Cu(Xan)(H2O)2] complex. The title compounds also exhibit superoxide dismutase mimetic activity.