Temperature Effects on the Solvent-Dependent Deactivation of Singlet Oxygen

Singlet molecular oxygen, O-2(a(1)Delta(g)), is an intermediate in a variety of oxygenation reactions. The reactivity of singlet oxygen in a given system is influenced, in part, by competitive solvent-dependent channels that deactivate singlet oxygen in a nonradiative process. It has long been considered that these deactivation channels depend only slightly on temperature. This conclusion has been incorporated into the accepted empirically derived model of electronic-to-vibrational energy transfer used to account for the effect of solvent on the lifetime of singlet oxygen, tau(Delta). The current study reveals that tau(Delta), in fact, can depend quite significantly on temperature in certain solvents (e.g., D2O and benzene-d(6)). These results can have practical ramifications in studies of singlet oxygen reactivity. From a fundamental perspective, these data indicate that aspects of the model for nonradiative deactivation of singlet oxygen need to be re-evaluated.