QUENCHING OF TRIPLET BENZOPHENONE BY METHYL AND METHOXY BENZENES - ARE TRIPLET EXCIPLEXES INVOLVED

The quenching of triplet benzophenone by methyl and methoxy substitute d benzenes in acetonitrile was investigated. For both series of donors the quenching rate constants are considerably higher than expected fr om the Rehm-Weller relationship, which could be explained by a mechani sm involving a (triplet) exciplex intermediate. Two corresponding mode ls from the literature were chosen for simulating the experimental dat a. The results are in accord with the exciplex proposal. For a given d riving force the quenching rate constants differ substantially for the two kinds of donor employed. Together with the free ion yields, obtai ned by transient photoconductivity measurements, this confirms the imp ortant role of the chemical structure of the donors which determines t he stability of the exciplexes. (C) 1997 Elsevier Science S.A.