The interesting DNA-binding properties of three novel dinuclear Ru(II) complexes with varied lengths of flexible bridges

Three binuclear Ru(II) complexes with two [Ru(bpy)2(pip)]2+-based subunits {where bpy = 2,2′-bipyridine and pip = 2-phenylimidazo[4,5-f][1,10]phenanthroline} being linked by varied lengths of flexible bridges, were synthesized and characterized by 1H NMR, elemental analysis, UV–visible (UV–vis) and photoluminescence spectroscopy. The structures of the three complexes were optimized by density functional theory calculations. The interaction of the complexes with calf thymus DNA was investigated by UV–vis and luminescence titrations, steady-state emission quenching by [Fe(CN)6]4−, DNA competitive binding with ethidium bromide, DNA melting experiments, and viscosity measurements. The experimental results indicated that the three complexes bound to the DNA most probably in a threading intercalation binding mode with high DNA binding constant values three orders of magnitude greater than the DNA binding constant value reported for proven DNA intercalator, mononuclear counterpart [Ru(bpy)2(p-mopip)]2+ {p-mopip = 2-(4-methoxylphenyl)imidazo[4,5-f][1,10]phenanthroline}.

Graphical AbstractUV–visible and emission spectroscopy studies, viscosity measurements, and density functional calculations indicated that the three complexes bound to calf thymus DNA most probably in a threading intercalation binding mode with high DNA binding constant values three orders of magnitude greater than the DNA binding constant value reported for proven DNA intercalator, mononuclear counterpart [Ru(bpy)2(p-mopip)]2+ {p-mopip = 2-(4-methoxylphenyl)imidazo[4,5-f][1,10]phenanthroline}.Figure optionsDownload full-size imageDownload as PowerPoint slide