Premium
FLAVIN TRIPLET QUENCHING AND SEMIQUINONE FORMATION BY ALIPHATIC α‐SUBSTITUTED ACETIC ACIDS: INTERMEDIATES IN FLAVIN‐SENSITIZED PHOTODECARBOXYLATION *
Author(s) -
Ahmad Iqbal,
Tollin Gordon
Publication year - 1981
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.1751-1097.1981.tb09022.x
Subject(s) - flavin group , photochemistry , chemistry , quenching (fluorescence) , electron transfer , singlet state , photodissociation , semiquinone , excited state , fluorescence , stereochemistry , quinone , organic chemistry , physics , quantum mechanics , nuclear physics , enzyme
— The quenching of flavin excited states and the production of radical intermediates by aliphatic α‐substituted acetic acids have been investigated using fluorescence and laser photolysis measurements. Stern‐Volmer quenching constants for the flavin triplet are 2–4 orders of magnitude smaller than those found previously for aromatic acids. At the high substrate concentrations required to obtain triplet quenching, singlet quenching, probably via exciplex formation, is also observed. When triplet and radical yields are quantitated, it is found that, for pyruvate, glyoxylate and lactate, quenching occurs virtually exclusively by a one‐electron transfer mechanism. This supports the contention that the flavin‐sensitized photodecarboxylation of these acids proceeds via a radical mechanism.