Chiral diruthenium(II) complexes containing a modified 4,4′-bipyridine bridging ligand: syntheses, characterization and DNA binding

A pair of novel chiral dimeric ruthenium(II) complexes [ΔΔ-, ΛΛ-Ru(bpy)2(btpb)Ru(bpy)2]4+ (1; btpb=2,2′-bis(1,2,4-triazino[5,6-f]phenanthren-3-yl)-4,4′-bipyridine) have been synthesized and characterized by electrospray mass spectra, 1H NMR, UV–Vis and circular dichroism spectra. Binding behaviors of the complexes with calf thymus DNA have been investigated by absorption spectra and viscosity measurements. The electronic absorption spectrum of ΔΔ-1 at 505.5 nm exhibits hypochromism of about 8.4% and bathochromism of 2.5 nm; ΛΛ-1 at 500.0 nm exhibits hypochromism of about 9.1% and bathochromism of 4.5 nm, respectively. The experiments suggest that ΔΔ-1 and ΛΛ-1 may be bound to DNA by non-intercalating binder.