BENZOPHENONE SENSITIZED PHOTOCHEMISTRY OF A COPPER(II) POLYPYRAZOLYLBORATE COMPLEX

Benzophenone's triplet state can efficiently sensitize the photoreduct ion of the dihydrobis(1-pyrazolyl)borate Cu-II complex [1, Cu(Bp)(2)] in solvents such as alcohols, THF or toluene. The efficiency of the re action was quantitatively evaluated by determining the quantum yields, Phi(Cu), in different solvents. The results showed that the sensitize d photoreduction was more efficient in solvents with better hydrogen d onating power. The rate constant (k(q)) for quenching of the benzophen one triplet by Cu(Bp)(2) was determined by Stern-Volmer type experimen ts. By carrying out the photolyses in the presence of coordinating lig ands (phosphines or phosphites), it was determined that the first step in the photoreaction is the formation of Cu-I complex. A general reac tion scheme is proposed.