Hetero-metallic trigonal cage-shaped dimeric Ni 3 K core complex of L-proline ligand: Synthesis, structural, electrochemical and DNA binding and cleavage activities

Abstract

Hetero-metallic trigonal cage-shaped dimeric Ni3K core complex of L-proline ligand has been synthesized and characterized. Single crystal X-ray diffraction analysis showed that the hetero-metallic Ni(II)–K(I) complex has a dimeric structure with nine coordinated potassium atoms and six coordinated nickel atoms. The cyclic voltammograms of the complex exhibited two successive quasireversible reduction waves at (\(E_{\text {pc}}^{1} = -\)1.02 V and \(E_{\text {pc}}^{2} = -\)1.33 V) and two successive irreversible oxidation waves (\(E_{\text {pa}}^{1} =\) 0.95 V and \(E_{\text {pa}}^{2} =\) 1.45 V) versus Ag/AgCl in DMF solution. Interaction of the complex with calf-thymus DNA (CT DNA) has been studied using spectroscopic techniques. The complex is an avid DNA binder with a binding constant of 3.6 × 108 M−1. The complex showed efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of the reducing agent hydrogen peroxide involving hydroxyl radical (∘OH) species. As evidenced from the control experiment, DNA cleavage in the presence of∘OH radical was inhibited by quenchers, viz. DMSO and KI. The complex showed in vitro antimicrobial activity against four bacteria and two fungi and the activity is greater than that of the free ligand. Hetero-metallic trigonal cage-shaped dimeric Ni3K core complex of ligand L-proline was synthesized. The complex is an avid DNA binder. The complex showed efficient oxidative cleavage of supercoiled pBR322 DNA in the presence of H2O2 involving hydroxyl radical species.