Photoredox behavior and chiral discrimination of DNA bound M(diimine)3n+ complexes (M = Ru2+, Cr3+)

An overview is given of the rapidly developing field of bioinorganic chemistry involving the interaction of Ru(diimine)(3)(2+) complexes with double-stranded DNA. This contribution focusses on the photoredox behavior of these DNA bound systems and the presence of chiral discrimination in the binding process. Cr(diimine)(3)(3+) complexes are attractive new candidates for such studies in view of their long-lived room temperature luminescence and strong excited state oxidizing power. For these Cr(III) systems we observe strong quenching of the emission signal in the presence of B-DNA, and provide evidence that this quenching is associated with a photoredox process involving guanine base oxidation. We also demonstrate the value of capillary electrophoresis (CE) as a technique for assessing the relative binding constants and the stereoselectivities of transition metal interactions with DNA. In addition, we explore the use of CE as an alternative approach to help resolve literature disagreements between different Ru(phen)(3)(2+)/DNA binding models. (C) 2001 Elsevier Science B.V. All rights reserved.