Energy barrier in the photorearrangement of azoxybenzene to 2-hydroxyazobenzene

Abstract

The temperature dependence of the quantum yields of the photorearrangement of azoxybenzene in polar protic solvents and of 6,2′-dimethylazoxybenzene in polar protic and non-polar solvents to the corresponding 2-hydroxyazobenzenes in the range from room temperature to liquid nitrogen temperature was studied. It is shown that an energy barrier exists in the path from the ground state intermediate, observed in this work for the first time, to the photoproduct. The formation of the ground state intermediate also appears to be temperature dependent. Further, the observation that the quantum yields of the photorearrangement of 6,2′-dimethylazoxybenzene in non-polar and polar protic solvents at room temperature are comparable indicates that it is not catalysed solely by the presence of proton-donating solvents.