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Photoinduced Electron Transfer Between Chlorophylls ( a / b ) and Fullerenes (C 60 /C 70 ) Studied by Laser Flash Photolysis ¶
Author(s) -
ElKhouly Mohamed E.,
Araki Yasuyuki,
Fujitsuka Mamoru,
Watanabe Akira,
Ito Osamu
Publication year - 2001
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2001)0740022petbca2.0.co2
Subject(s) - fullerene , flash photolysis , photochemistry , flash (photography) , electron transfer , chemistry , laser , photodissociation , photoinduced electron transfer , optics , organic chemistry , physics , reaction rate constant , quantum mechanics , kinetics
Photoinduced electron‐transfer processes in the systems of chlorophylls (Chl) (chlorophyll‐ a [Chl‐ a ] and chlorophyll‐ b ) and fullerenes (C 60 /C 70 ) in both polar and nonpolar solvents have been investigated with nanosecond laser photolysis technique, observing the transient spectra in the visible/near‐IR regions. By the excitation of Chl in benzonitrile (BN) it has been proved that electron transfer takes place from the triplet excited states of Chl to the ground states of C 60 /C 70 . By the excitation of C 70 in BN electron transfer takes place from the ground states of Chl to the triplet excited state of C 70 . In both Chl the rate constants and quantum yields for the electron‐transfer processes are as high as those of zinc porphyrins and zinc phthalocyanines, indicating that the long alkyl chains of Chl play no role in retarding the electron transfer. The rate constant for the electron‐mediating process from the radical anion of C 70 to octylviologen dication yielding the octylviologen radical cation was evaluated. The back electron‐transfer process from the viologen radical cation to the radical cation of Chl‐ a takes place in a longer time‐scale, indicating that a photosensitized electron‐transfer/electron‐mediating cycle is achieved.