Characterization of the Excited-State Reactivity of a Persistent Aryl-Substituted Allyl Free Radical

Article abstract of DOI:10.1021/j100152a045

A family of stable aryl-substituted allyl radicals 1 (9H-fluoren-9-yl-9-<9H-fluoren>-9-ylidenephenylmethyls) has been characterized by electronic absorption spectroscopy, semiempirical (AM1) molecular orbital calculations, and cyclic voltammetry.Photolysis of 1a in aerated solvents that are poorer hydrogen atom sources than toluene resulted in oxygenation (Φ_OX ca. 5 * 10^-4) and cleavage products.A thermally reversible photocyclization mechanism is proposed to explain the oxygenation of 1a in inert solvents.Enhanced excited-state reactivity toward hydrogen and halogen atom donors was observed during the steady-state photolysis of 1a.Electron transfer from naphthalene to an excited state of 1a produces an extremely short lived (<30 ps) 1a anion/naphthalene radical cation geminate pair.