DNA Interaction, Photocleavage and Topoisomerase I Inhibition by Ru(II) Complex with a New Ligand Possessing Phenazine Unit

A new ruthenium complex with a dppz-like ligand pyidppz, [Ru(bpy)2(pyidppz)]2+ (pyidppz = 2-(pyridine-2-yl)imidazo-[4,5-b]dipyrido-[3,2-a:2′,3′-c]phenazine) has been synthesized and characterized by ES-MS, elemental analysis, 1H NMR. Intercalative mode of the complex bound to calf thymus DNA has been supported by different spectroscopic methods and viscosity measurements. The introduction of phenazine unit may be one of the main reasons for the weak emission of Ru(II) complex in aqueous solution. Under irradiation, this complex can efficiently cleave DNA. And the photocleavage reaction of the complex is found to be inhibited in the presence of singlet oxygen scavenger. Topoisomerase inhibition and DNA strand passage assay demonstrated that [Ru(bpy)2(pyidppz)]2+ and its parent complex [Ru(bpy)2(pyip)]2+ (pyip = 2-(pyridine-2-yl)imidazo[4,5-f][1,10]phenanthroline) can act as efficient catalytic inhibitor of DNA topoisomerase I.