Effect of the ancillary ligands on the binding of ruthenium(II) complexes [Ru(dmp)2(MCMIP)]2+ and [Ru(dmb)2(MCMIP)]2+ with DNA

Two polypyridine ruthenium(II) complexes, [Ru(dmp)₂(MCMIP)]²⁺ (1) (MCMIP = 2-(6-methyl-3-chromonyl)imidazo[4,5-f][1,10]-phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline) and [Ru(dmb)₂(MCMIP)]²⁺ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine), have been synthesized and characterized by elemental analysis, ES-MS and ¹H NMR. The DNA-binding behaviors of these complexes were investigated by electronic absorption titration, fluorescence spectroscopy, viscosity measurements and thermal denaturation. The results show that 1 and 2 effectively bind to CT-DNA; the DNA-binding affinities are closely related to the ancillary ligand.