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)(HET)](2+) (2) (bpy=2,2'-bipyridine; phen = 1,10-phenanthroline; HBT = 11H, 13HA, 5,9,10,12,14-hexaaza-benzo [b] triphenylene) have been synthesized and characterized by elemental analysis, mass spectra, H-1 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 I and 2 bring about photocleavage of plasmid DNA when irradiated at 440 nm. (C) 2008 Elsevier Masson SAS. All rights reserved.