In vitro study on DNA binding of ruthenium(II) complexes with polypyridyl ligands.

A new ligand {2-(5-nitro-furan-2-yl)-1H-1,3,7,8-tetraaza-cyclopenta[l]-phenanthrene} (nftp) and its Ru(II) complexes [Ru(phen)(2)(nftp)](2+) (1) (phen = 1,10-phenanthroline) and [Ru(bpy)(2)(nftp)](2+) (2) (bpy = 2,2'-bipyridine) were synthesized and characterized. The binding properties of the two complexes to calf thymus-DNA (CT-DNA) were investigated by different spectrophotometric methods and viscosity measurements together with equilibrium dialysis and circular dichroism spectroscopy. The results suggest that both complexes bind to DNA through intercalation and enantioselectively interact with CT-DNA. However, complex 1 is a better candidate as an enantioselective binder to CT-DNA than complex 2. Although no emission is generally observed in water or organic solvents for Ru(II) polypyridyl complexes with a nitro group, complexes 1 and 2 can emit luminescence in both media. When irradiated at 365 nm, complex 1 cleaves DNA more effectively than complex 2.