Photophysics and photochemistry of triplet exciplexes between triplet naphthalene derivatives and benzophenone
The photophysical and photochemical behaviors in the naphthalene derivatives (RX) and benzophenone (BP or XO) systems have been studied by means of 355-nm laser photolysis techniques in polar media. At the initial event, the triplet energy transfer (TET) occurs from 3BP* to RX in the nanosecond region. It is found that the following reactions occur effectively in polar media via the triplet exciplexes having loose sandwich-like structures with weak charge-transfer character in the microsecond region: (1) For RNH3'-BP or ROH-BP system, hydrogen atom transfer (HT), for the latter proton-enhanced HT whereas for the former proton-reduced HT, and the more protic hydrogen atom of -NH3+ is more reactive in HT for the HOW3'-BP system (2) for the ROMe-BP system, proton-induced electron transfer (ET) in the presence of protons. (3) for the RN(Me)* (or RN(Et,))-BP system, hydrogen-bonding-induced ET in the presence of H20 or methanol.