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CHLOROPHYLL PHOTOCHEMISTRY IN CONDENSED MEDIA—I. TRIPLET STATE QUENCHING AND ELECTRON TRANSFER TO QUINONE IN CELLULOSE ACETATE FILMS *
Author(s) -
Cheddar Glen,
Castelli Francesco,
Tollin Gordon
Publication year - 1980
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 - 10.1111/j.1751-1097.1980.tb03988.x
Subject(s) - flash photolysis , triplet state , photochemistry , chemistry , quinone , quenching (fluorescence) , reaction rate constant , semiquinone , electron transfer , radical , kinetics , electron paramagnetic resonance , singlet state , aqueous solution , excited state , fluorescence , organic chemistry , molecule , physics , nuclear magnetic resonance , quantum mechanics , nuclear physics
— Chlorophyll‐ a was incorporated into cellulose acetate films and the triplet state decay kinetics and electron transfer from triplet to p‐benzoquinone in aqueous solution was studied using laser flash photolysis and EPR. The triplet was found to decay by first order kinetics with a rate constant which was independent of Chl concentration. The triplet yield, however, was concentration dependent. These properties are due to quenching which occurs only at the singlet state level. In the presence of quinone, the triplet is quenched and, when the quinone is in an aqueous solution in contact with the film, Chl cation radical (C ± ) as well as the semiquinone anion radical (Q ± ) can be observed. The C decays by second order kinetics with a rate constant of 1.5 × 10 6 M ‐1 s ‐1 . Although triplet conversion to radicals is slightly lower in the films as compared to fluid solutions (˜ 3 times), the lifetimes of the radicals are greatly increased (˜ 10 3 times).