Electron spin resonance studies of photo-oxidation by metal ions in rigid media at low temperatures. Part 4.—Survey of photo-oxidation by the uranyl ion

Abstract

The long-standing problem of the mechanism of photo-oxidation of organic and inorganic molecules by the UO²⁺₂ ion has been explored in some detail by the matrix isolation method, the detection of trapped substrate-derived radicals being effected by electron spin resonance spectroscopy, mostly using organic matrices at 77 K. A variety of mechanisms is apparent even within a given homologous series, but the most common feature is abstraction of a hydrogen atom from a carbon atom adjacent to an activating group such as —CO—, —CN, —CO₂H, —CHO, —OH, —CONH₂, —CO₂R or from a phosphorus atom; carbon-carbon cleavage is found (sometimes exclusively) with secondary and tertiary alcohols, ketones, some carboxylic acids and diethyl ether. These results are discussed in the light of recent steady-state studies involving comparison of quantum yield and fluorescence quenching data.