Synthesis and DNA-binding studies of two ruthenium(II) complexes of an intercalating ligand.

Two new ruthenium(II) complexes [Ru(bpy)(2)(HBT)](2+) (1) and [Ru(phen)(2)(HBT)](2+) (2) (bpy=2,2'-bipyridine; phen=1,10-phenanthroline; HBT=11H, 13H-4, 5,9,10,12,14-hexaaza-benzo [b] triphenylene) have been synthesized and characterized by elemental analysis, mass spectra, (1)H NMR and cyclic voltammetry. The DNA binding property of the two complexes has been investigated employing absorption spectroscopy, fluorescence spectroscopy and viscosity measurements. Both complexes 1 and 2 have been found to prefer intercalative binding to DNA. The DNA binding constants for the two complexes have been measured to be 5.71+/-0.20 x 10(7) and 4.65+/-0.20 x 10(7)M(-1) through ethidium bromide displacement method. Molecular modeling studies too indicate that both complexes 1 and 2 prefer intercalative binding to DNA and both these complexes exhibit similar DNA binding energies. Both complexes 1 and 2 bring about photocleavage of plasmid DNA when irradiated at 440 nm.