DNA interaction studies and photoinduced ligand exchange kinetics of a sterically strained ruthenium(II) complex

Abstract

Sterically strained ruthenium polypyridyl complexes represent an emerging class of bioactive molecules, capable of photoinduced ligand exchange and covalent binding with DNA, in a manner similar to cisplatin. A sterically strained complex, [Ru(biq)2(dpp)](PF6)2, where biq=2,2′-biquinoline, dpp=2,3-bis(2-pyridyl)pyrazine, was synthesized, and investigated with respect to its photoinduced ligand exchange and DNA interaction properties. Although synthesis and redox properties of the complex, [Ru(biq)2(dpp)](PF6)2, have been reported, the photoinduced ligand exchange properties and DNA binding properties have not yet been reported. Photoinduced dissociation of the dpp ligand was observed upon irradiation of water or acetonitrile solutions of the metal complex with visible light (λirr⩾550nm) to generate [Ru(biq)2(H2O)2](PF6)2 and [Ru(biq)2(CH3CN)2](PF6)2 complexes, respectively. The half-lives of photoactivated exchange of the dpp ligand with water and acetonitrile were found to be 14min and 6min, respectively. The dissociation of the dpp ligand upon irradiation with light was confirmed by mass spectrometry. The synthesized complex displays covalent binding with DNA upon irradiation with visible light, confirmed by slowing down of the rate of DNA migration in agarose gel electrophoresis. No effect on the rate of migration of DNA was observed when incubated with metal complex in dark. The spectroscopic, photoinduced ligand exchange kinetics and DNA interaction properties are presented.