Internal and external heavy-atom effects on the photolysis of 1-benzyloxy-2-pyridone

The emission efficiencies of the title compound (BP) are subject to pronounced internal and external heavy-atom effects while the efficiency of its photoreaction is insensitive to these heavyatom perturbations. This result is explained in terms of the mechanism in which the N–O bond cleavage in a BP molecule takes place from higher vibrational states of the first excited singlet state in competition with vibrational relaxation to the fluorescent state. Further supporting evidence for this mechanism is obtained from temperature effects on the fluorescence and reaction efficiencies of BP.