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ENERGY CONVERSION IN THE DECAY OF TRIPLET LUMIFLAVIN IN THE PRESENCE OF FERRI‐ AND FERROCYANIDE
Author(s) -
Naman S. A.
Publication year - 1988
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.1751-1097.1988.tb02693.x
Subject(s) - ferricyanide , chemistry , reaction rate constant , ferrocyanide , photochemistry , flash photolysis , quenching (fluorescence) , electron transfer , triplet state , excited state , kinetics , inorganic chemistry , fluorescence , organic chemistry , molecule , atomic physics , physics , electrode , quantum mechanics
— Flash photolysis at 450 nm has been used to study the quenching of the excited triplet state of lumiflavin and the transient species formed in subsequent reactions in deaerated phosphate buffer (pH 6.9). The effect of the presence of ferricyanide on the life time of triplet lumiflavin has been studied. The results suggest an energy transfer reaction without concurrent electron transfer reactions. The rate constant for the process was 2.8 times 10 9 M ‐1 s ‐1 . The analogous reaction with ferrocyanide could not be observed because of the efficient electron transfer reaction (δG = ‐20.6 kcal mol ‐1 ) leading to the formation of the semireduced lumiflavin and ferricyanide. The rate constant for this reaction was 3.3 times 10 9 M ‐1 s ‐1 . The semireduced lumiflavin radical was found to disappear in a second order reaction with a rate constant of 1.7 times 10 9 M ‐1 s ‐1 . It was found to react with ferricyanide with a rate constant of 0.7 times 10 9 M ‐1 s ‐1 . A model for the various photochemical and photophysical processes involved in the decay and quenching of the lumiflavin triplet state is suggested and discussed.