Abstract
The reactivity of the photoexcited triplet states of chlorophyll a (Chla), ZnTPP, and MgTPP (P/sup T/) with radicals was studied in neutral micelles by pulse radiolysis and photolysis (PRAP) spectroscopy. Steady-state triplet concentration was produced by a 2-ms light pulse, and the system was then subjected to a 10-ns electron pulse to form the radicals (CH/sub 3/)/sub 2/COH, Br/sub 2//sup -/. and MV/sup +/. from the proper solutes. The triplet states were found to undergo one-electron reduction by (CH/sub 3/)/sub 2/COH and oxidation by Br/sub 2//sup -/. with second-order rate constants approaching the diffusion-controlled limit and significantly more rapidly than the reactions of the ground states. The reaction of the triplet states (P/sup T/) with MV/sup +/. radicals was found to result in an overall recovery of the ground-state P from P/sup T/. The mechanism of this process is discussed in terms of two steps of electron transfer. P/sup T/ + MV/sup +/. ..-->.. P/sup -/. + MV/sup 2 +/ ..-->.. P + MV/sup +/.
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