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LASER PHOTOLYSIS STUDIES OF QUINONE REDUCTION BY PHEOPHYTIN a IN ALCOHOL SOLUTION
Author(s) -
Castelli Francesco,
Cheddar Glen,
Rizzuto Frank,
Tollin Gordon
Publication year - 1979
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.1751-1097.1979.tb09274.x
Subject(s) - pheophytin , chemistry , photochemistry , deuterium , photodissociation , disproportionation , kinetic isotope effect , semiquinone , solvent , quinone , singlet state , excited state , stereochemistry , organic chemistry , catalysis , photosystem ii , quantum mechanics , nuclear physics , biochemistry , photosynthesis , physics
‐ Upon laser photolysis of pheophytin‐benzoquinone solutions in ethanol, transients due to the pheophytin triplet state (P t ), an exciplex (Pδ + Qδ ‐ ), the pheophytin cation radical (P + ) and the semiquinone radical (Q ‐ ) can be observed. Kinetic analysis indicates that the evolution of these transients at times longer than one microsecond is due to the decay of the exciplex with the concomitant formation of P + and Q ‐ , reverse electron transfer to form P and Q, solvent oxidation by P + , and Q ‐ disproportionation. In support of the suggested solvent oxidation reaction, a large deuterium isotope effect is observed upon changing the solvent from methanol to its fully‐deuterated counterpart. Comparisons are made between these results and those obtained with chlorophyll as described in the preceding paper.