Spectroscopy studies on DNA binding of two ruthenium complexes [Ru(MeIm)₄(L)]²⁺ (L = iip and tip)

Two ruthenium(II) complexes [Ru(MeIm)4(L)]2+ (L = 2-(imidazo-4-group)-1H-imidazo-[4,5-f][1,10]phenanthroline, 2-(thiophene-2-group)-1H-imidazo[4,5-f][1,10]phenanthroline, MeIm = 1-methylimidazole) have been synthesized according to literature and structurally characterized. The interaction of the complexes with calf thymus DNA has been explored using electronic absorption titration, competitive binding experiment, circular dichroism, thermal denaturation, and viscosity measurements. The results show that both complexes could bind DNA in a intercalation mode and the DNA-binding affinity of [Ru(MeIm)4(tip)]2+ (K b = (7.2 ± 0.3) × 105 (mol L−1)−1) is greater than that of [Ru(MeIm)4(iip)]2+ (K b = (6.1 ± 0.2) × 105 (mol L−1)−1).