Syntheses, characterization and DNA binding of mono- and diruthenium(II) complexes containing 2,2′-bis(1,2,4-triazino[5,6-f]phenanthren-3-yl)-4,4′-bipyridine and 2,2′-bipyridine ligands

A novel bridging ligand 2,2'-bis(1,2,4-triazino[5,6-f]phenanthren-3-yl)-4,4'-bipyridine (btpb) and its mononuclear ruthenium(II) complex [Ru(bpy)(2)(btpb)](2+) (Rubtpb; bpy = 2,2'-bipyridyl) and dinuclear ruthenium(II) complex [Ru(bpy)(2)(btpb)Ru(bpy)(2)](4+) (Ru(2)btpb) have been synthesized and characterized by elemental analyses, fast atom bombardment or electrospray mass spectra, H-1 NMR, and electronic spectroscopy. Binding behaviors of the mono- and dinuclear complexes with calf thymus DNA (CT-DNA) have been investigated by absorption spectra, viscosity measurements, and equilibrium dialysis experiments. As the concentration of DNA is increased, the electronic absorption spectra bands at the metal-ligand charge transfer of the mononuclear complex Rubtpb at 501.0 nm exhibit hypochromism of about 17.4% and bathochromism of 2.0 nm, the dinuclear complex Ru(2)btpb at 511.0 nm exhibits hypochromism of about 24.8% and bathochromism of 1.0 nm. The increasing amounts of the complexes on the relative viscosities of CT-DNA are much smaller than that of the classic intercalators. The experiments suggest that the Rubtpb and Ru(2)btpb may be bound to DNA by non-intercalating binder. (c) 2004 Published by Elsevier B.V.