EPR Investigation of Photoinduced Radical Pair Formation and Decay to a Triplet State in a Carotene-Porphyrin-Fullerene Triad
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- 作者：Donatella Carbonera ; Marilena Di Valentin ; Carlo Corvaja ; Giancarlo Agostini ; Giovanni Giacometti ; Paul A. Liddell ; Darius Kuciauskas ; Ana L. Moore ; Thomas A. Moore ; and Devens Gust
- 刊名：Journal of the American Chemical Society
- 出版年：1998
- 出版时间：May 13, 1998
- 年：1998
- 卷：120
- 期：18
- 页码：4398 - 4405
- 全文大小：191K
- 年卷期：v.120,no.18(May 13, 1998)
- ISSN：1520-5126
文摘
The photochemistry of a molecular triad consisting of aporphyrin (P) covalently linked to a carotenoidpolyene (C) and a fullerene derivative (C60) has beenstudied at 20 K by time-resolved EPR spectroscopyfollowing laser excitation. Excitation of the porphyrin moietyyields C-1P-C60, which decays byphotoinducedelectron transfer to yieldC-P
+-C60-.This state rapidly evolves into a final charge-separated stateC+-P-C60-, whose spin-polarizedEPR signal was observed and simulated. There is a weak exchangeinteractionbetween the electrons in the radical pair (J = 1.2 G).TheC+-P-C60-state decays to give the carotenoidtriplet in high yield with a time constant of 1.2 
s. The spinpolarization of 3C-P-C60 is characteristicof atriplet formed by charge recombination of a singlet-derived radicalpair. The kinetics of the decay of 3C-P-C60 to the ground state were also determined. Thephotoinduced electron transfer from an excited singletstate at low temperature and the high yield of charge recombination toa spin-polarized triplet mimic similarprocesses observed in photosynthetic reaction centers.
+-C60-.This state rapidly evolves into a final charge-separated stateC+-P-C60-, whose spin-polarizedEPR signal was observed and simulated. There is a weak exchangeinteractionbetween the electrons in the radical pair (J = 1.2 G).TheC+-P-C60-state decays to give the carotenoidtriplet in high yield with a time constant of 1.2 s. The spinpolarization of 3C-P-C60 is characteristicof atriplet formed by charge recombination of a singlet-derived radicalpair. The kinetics of the decay of 3C-P-C60 to the ground state were also determined. Thephotoinduced electron transfer from an excited singletstate at low temperature and the high yield of charge recombination toa spin-polarized triplet mimic similarprocesses observed in photosynthetic reaction centers.