Efficient and selective photochemical labilization of a given bidentate ligand in mixed ruthenium(II) complexes of the Ru(phen)(2)L2+ and Ru(bipy)(2)L2+ family (L = sterically hindering chelate)

Mixed ruthenium(II) complexes containing 1,10-phenanthroline (or 2,2 '-bipy ridine) and a sterically congested bidentate ligand such as 2,9-diphenyl-1, 10-phenanthroline, 6,6 '-dimethyl- or 6,6 '-diphenyl-2,2 '-bipyridine, or 1 -(2 '-pyridyl)-3,5- dimethylpyrazole undergo clean and selective ligand sub stitution under irradiation with visible light. For instance, Ru(phen)(2)(d mbp)(2+) in CH3CN is quantitatively converted to Ru(phen)(2)(CH3CN)(2)(2+) in a photochemical reaction accompanied by expulsion of the sterically hind ering chelate dmbp (phen 1,10-phenanthroline; dmbp= 6,6 '-dimethyl-2,2 '-bi pyridine). Interestingly, 2,2 '-bipyridine was found to be photochemically ejected in one case, probably as a consequence of its greater flexibility.