Chemical Scavenging Yields for Short-Lived Products from the Visible Light Photoionization of the Tris(bipyridine)ruthenium(II) Triplet Metal-to-Ligand Charge-Transfer Excited State.

The rate of visible light photoionization of the tris(bipyridine)ruthenium(II) triplet metal-to-ligand charge-transfer excited state (MLCT) is very strongly dependent on the acid concentration in aqueous solution, and the pattern of this dependence is similar to that reported for the photoionization of iodide. With 405 nm visible irradiation of MLCT, less than 15% of the photoionized products appear as free solvated electrons in bulk solution, while more than 75% of the photoproducts appear to be solvent-separated, (oxidized substrate)-electron ion pairs that efficiently recombine with the photo-oxidized complex in the absence of an electron scavenger. The quantum yield of free solvated electrons generated by these 405 nm irradiations is approximately 0.