ELECTRONIC-PROPERTIES OF AQUAPOLYPYRIDYL RUTHENIUM COMPLEXES BOUND TODNA

The photophysics of complexes based on [(tpy)(L)RuOH2]2+ (tpy = 2,2',2 ''-terpyridine; L = bpy, 2,2'-bipyridine; phen, 1,10-phenanthroline; d ppz, dipyridophenazine) both in solution and bound to DNA have been in vestigated. Changes in the MLCT absorptions are consistent with DNA bi nding. The bpy and phen complexes are weakly emissive in fluid solutio n, and this emission is enhanced by a factor of two upon binding to DN A. The dppz complex is not emissive in buffer solution, but does emit upon binding. The low emission quantum yields of these complexes can b e attributed primarily to the proximity of dd states to the emissive M LCT states. Absorbance and emission titrations can be used to determin e binding affinities of 400 M-1 for [(tpy)(bpy)Ru(OH2)]2+ and 700000 M -1 for [(tpy)(dppz)Ru(OH2)]2+. The complexes are capable of binding co valently to DNA by replacement of the aqua ligand by a nucleophile in DNA. The covalent adduct is also emissive.