Synthesis and bio-catalytic activity of isostructural cobalt(III)-phenanthroline complexes

Abstract

We have synthesized two isostructural mononuclear cobalt(III) complexes [1]NO3⋅3H2O and [1]NO3⋅CH3CO2H⋅H2O {[1] + = [Co(1,10-phenanthroline)2Cl2]+} and characterized by single crystal X-ray structural analyses. Mass spectral studies of the complexes indicate both the compounds to produce identical cationic species viz., [Co(phen)2Cl2]+ in methanol solution. [1]+ has been evaluated as model system for the catechol oxidase enzyme by using 3,5-di-tert-butylcatechol (3,5-DTBC) as the substrate in methanol medium, which revealed that the cationic complex efficiently inhibits catalytic activity with kcat value 9.65 ×102 h−1. [1]+ cleaved pBR 322 DNA without addition of an activating agent. Further, the anti-cancer activity of [1]+ on human hepatocarcinoma cell line (HepG2) has been examined. The induction of apoptosis induced in the cell line was assessed base on the changes in cell morphology, which showed the efficacy of [1] + to induce apoptosis in 53% of cells during 24 h treatment. Interestingly, the observed IC50 values reveal that [1]+ brings about conformational change on DNA strongly and exhibits remarkable cytotoxicity. The cationic cobalt(III) complex exhibits good catalytic activity in saturated oxygen environment towards 3,5-ditertbutylcatechol with kcat value 9.65×102 h-1. It also exhibits important cytotoxicity against human hepatocarcinoma cell line (HepG2).