UV Laser Photochemistry: Triplet Biradical Trapping Efficiencies and Lifetimes

Article abstract of DOI:10.1021/ja00265a015

The trapping of triplet 1,3-cyclopentadiyl (1a) and the triplet 1,4-biradical 2-<2-ethyl>cyclopent-2-enyl (6) with molecular oxygen has been studied quantitatively.The lifetime of 1a has been found to range between 720 and 900 ns and that of 6 between 53 and 94 ns depending on the solvent.The biradical 1a was found to be trapped in essentially quantitative yield with no indication of oxygen-catalyzed intersystem crossing.In contrast, 6 was found to be trapped in 54-79percent yield with the residual biradical quenching being due to oxygen-catalyzed intersystem crossing.These and other biradical trapping data have been correlated with 1,3-biradical geometries and found to be in accord with Salem's rules for spin-orbit coupling in triplet biradicals.