Synthesis, characterization and the effect of ligand planarity of [Ru(bpy)(2)L](2+) on DNA binding affinity

Two structurally related ligands (L) 4,5,9,18-tetraazaphenanthreno[9,10-b] triphenylene (taptp) and 2,3-diphenyl-1,4,8,9-tetraazatriphenylene (dptatp) , and their related complexes of [Ru(bpy)(2)L](2+) have been synthesized an d characterized by elemental analyses, H-1 NMR and mass spectra. Their elec trochemical properties were also examined. Both complexes emit intense lumi nescence in organic solvent but are quenched in water to different extents. The interactions of the complexes with calf thymus DNA have been investiga ted by viscosity, absorption, emission and circular dichroism spectra. The intrinsic binding constants of [Ru(bpy)(2)(taptp)](2+) and [Ru(bpy)(2)(dpta tp)] (2+) are 1.7 x 10(5) and 3.8 x 10(4) M-1, respectively. All data indic ate that both complexes bind enantioselectively to double-stranded calf thy mus DNA via the intercalative mode, with stronger affinity for the fully pl anar ligand complex of [Ru(bpy)(2)(taptp)](2+). (C) 1999 Elsevier Science I nc, All rights reserved.