Study on DNA Binding Behavior and Light Switch Effect of New Coumarin-derived Ru(II) Complexes

A new ligand mhcip (mhcip=2-(4-methyl-7-hydroxyl-8-coumarinyl)imidazo[4,5-f]-[1,10]phenanthroline) and its ruthenium complexes, [Ru(L)2mhcip](2+) (L=bpy (2,2'-bipyridine), phen (1,10-phenanthroline)), have been synthesized and characterized. The introduction of coumarin ring may play an important role in the strong fluorescence of the complexes. Intercalative binding mode between both complexes and CT-DNA was determined by UV-visible spectroscopy, fluorescence spectroscopy and viscosity measurements. The two complexes show efficient DNA photocleavage under irradiation at 365 nm. The cycling of light switch off and on has been achieved for both complexes through the introduction of Cu(2+) and EDTA in the absence or presence of DNA.