Electron-Transfer Reactions of Chlorophyll a and Porphyrin Triplets with Radicals in Aqueous Micellar Solutions

Article abstract of DOI:10.1021/j100220a016

The reactivity of the photoexcited triplet states of chlorophyll a (Chla), ZnTPP, and MgTPP (P^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 (CH3)2.COH, Br2^-., and MV^+. from the proper solutes.The triplet states were found to undergo one-electron reduction by (CH3)2.COH and oxidation by Br2^-. 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^T) with MV^+. radicals was found to result in an overall recovery of the ground-state P from P^T.The mechanism of this process is discussed in terms of two steps of electron transfer: P^T + MV^+. -> P^-. + MV²⁺ -> P + MV^+..