Synthesis, characterization and DNA-binding properties of [Ru(phen)2taptp]2+ and [Ru(phen)2dptatp]2+

Two structurally related complexes [Ru(phen)2taptp]2+ (1) and [Ru(phen)2dptatp]2+ (2), where taptp is 4,5,9,18-tetraazaphenanthreno[9,10-b]triphenylene and dptatp is 2,3-diphenyl-1,4,8,9-tetraazatriphenylene, were synthesized and characterized by elemental analyses and 1H NMR. The spectroscopic and electrochemical properties of complexes 1 and 2 were also examined. Both complexes can luminesce in organic solvent but are quenched in water to different extents. The interaction of the complexes with calf thymus DNA was studied by absorption and emission spectra, as well as viscosity and lifetime measurements. All the data indicate that both complexes bind with double-stranded calf thymus DNA via intercalative mode. Unlike its analog [Ru(bpy)2taptp]2+, [Ru(phen)2taptp]2+ shows negligible luminescence in water buffer but bright luminescence on binding to DNA, enabling it to be a sensitive probe for DNA conformation.