Free Radicals Produced from the Derivatives of Pyrylium Salts in Solution by Photoillumination

Abstract

Abstract The photoreactions of 2,4,6-triphenyl- (TPP), 2-t-butyl-4,6-diphenylpyrylium (2BDPP) and 2,4,6-triphenylthiopyrylium (TPTP) salts in tetrahydrofuran (THF) and/or 1,2-dimethoxyethane were investigated. Photoproducts were identified to be pyranyl radicals on the basis of photochemical behavior and ESR spectra. Quantum yields of one-electron reduction reactions of TPP, 2BDPP, and TPTP were obtained to be 0.21, 0.047, and 0.53, respectively. The hf coupling constants of protons in the radicals were determined by simulation. The photoillumination of TPP in THF at low temperatures revealed that a certain intermediate radical species was involved in this one-electron photoreduction.