Synthesis, characterization, DNA binding properties, fluorescence studies and toxic activity of cobalt(III) and ruthenium(II) polypyridyl complexes.

The new ligand 4-(isopropylbenzaldehyde)imidazo[4,5-f ][1,10]phenanthroline (ippip) and its complexes Ru(phen)(2)(ippip)(1),Co(phen)(2)(ippip)(2),Ru(bpy)(2)(ippip)(3),Co(bpy)(2)(ippip)(4)(bpy=2,2-bipyridine) and (phen=1,10-phenanthroline) were synthesized and characterized by ES(+)-MS, (1)H and (13)C NMR. The DNA binding properties of the four complexes were investigated by different spectrophotometric methods and viscosity measurements. The results suggest that complexes bind to calf thymus DNA (CT-DNA) through intercalation. When irradiated at 365 nm, the complexes promote the photocleavage of pBR322 DNA, and complex 1 cleaves DNA more effectively than 2, 3, 4 complexes under comparable experimental conditions. Furthermore, photocleavage studies reveal that singlet oxygen ((1)O(2)) plays a significant role in the photocleavage.