DNA-binding and cleavage, cytotoxicity properties of Ru(II) complexes with 2-(4′-chloro-phenyl) imidazo[4,5-f][1,10]phenanthroline, ligand and their “light switch” on–off effect

Abstract

Three new complexes of the type [Ru(phen)2PIP-Cl](1) [Ru(bpy)2PIP-Cl](2) and [Ru(dmp)2PIP-Cl](3) (phen = 1,10-phenanthroline; bpy = 2,2′-bipyridine; dmb = 4,4-dimethyl-2,2′-bipyridine), PIP-Cl = 2-(4′-chloro-phenyl) imidazo[4,5-f][1,10]phenanthroline) were synthesized and characterized by using UV–VIS, IR and 1H-NMR, 13C-NMR spectral methods. Absorption spectroscopy, emission spectroscopy, viscosity measurements and DNA melting techniques were used to investigate the binding of these Ru(II) complexes with calf thymus DNA, and photocleavage studies were used to investigate the binding of these complexes with plasmid DNA. The spectroscopic studies together with viscosity measurements and DNA melting studies supported fact that Ru(II) complexes bind to CT-DNA(calf thymus DNA) by an intercalation mode via PIP-Cl into the base pairs of DNA. Upon irradiation, these novel Ru(II) complexes cleave the plasmid pBR 322 DNA from the supercoiled form I to the open circular form II.