Singlet oxygen as a reactive intermediate in the photodegradation of phenylenevinylene oligomers

Singlet molecular oxygen (a(1)Delta(g)) is shown to be the principal reacti ve intermediate in the photoinduced oxygen-dependent decomposition of a ser ies of phenylenevinylene oligomers. The reaction rate between singlet oxyge n and the oligomer decreases (1) with a decrease in the extent of phenylene vinylene conjugation (i.e., oligomer chain length) and (2) upon the incorpo ration of electron-withdrawing substituents on the oligomer. The reaction r ate, however, does not appear to depend solely on the electron density of t he oligomer pi system, as calculated using ab initio methods. For oligomers with vinyl-substituted cyano group(s), the reaction with singlet oxygen is very slow, thus making such compounds good candidates for the production o f stable electroluminescent materials.