Chemical modulation of the luminescence of a DNA-bound diruthenium(II) complex by copper(II) ion and EDTA

A method for the chemical modulation of the photoluminescence of a DNA-bound diruthenium(II) complex, [(bipy)2Ru(bpib)Ru(bipy)2]4+ (bipy = 2,2′-bipyridine, bpib = 1,4-bis([1, 10]phenanthroline [5,6-d]imidazol-2-yl) benzene) by the introduction of Cu2+ ion and EDTA has been developed. The diruthenium(II) complex showed strong photoluminescence both in buffer solutions and on an indium-tin oxide (ITO) surface, which was not modulated by Cu2+ or EDTA. The DNA-bound [(bipy)2Ru(bpib)Ru(bipy)2]4+ with a binding constant of 3.8 × 104 M−1 showed an enhancement in the luminescence based on the electrostatic interaction between the complex and DNA. The presence of Cu2+ was found to quench the luminescence of DNA-bound [(bipy)2Ru(bpib)Ru(bipy)2]4+, but the quenched luminescence was recovered by addition of an equimolar concentration of EDTA. Hence, the photoluminescence of DNA-bound [(bipy)2Ru(bpib)Ru(bipy)2]4+ depends strongly on the introduction of Cu2+ and EDTA.