Abstract

Benzophenone's triplet state can efficiently sensitize the photoreduction of the dihydrobis(1-pyrazolyl)borate CuII complex [1, Cu(Bp)2] in solvents such as alcohols, THF or toluene. The efficiency of the reaction was quantitatively evaluated by determining the quantum yields, ?Cu, in different solvents. The results showed that the sensitized photoreduction was more efficient in solvents with better hydrogen donating power. The rate constant (kq) for quenching of the benzophenone triplet by Cu(Bp)2 was determined by Stern-Volmer type experiments. By carrying out the photolyses in the presence of coordinating ligands (phosphines or phosphites), it was determined that the first step in the photoreaction is the formation of CuI complex. A general reaction scheme is proposed.