Triplet behaviour in fluorocarbon solvents

Abstract

The phosphorescence efficiencies and lifetimes of 9 aromatic carbonyl compounds in fluorocarbon solvents at 20°C are reported, and triplet radiative lifetimes derived. With one exception the measured lifetimes fall in the range 0.3–1.0 ms, i.e., close to the range of lifetimes observed for the “unreactive” triplets in conventional solvents. Measurement of phosphorescence in fluorocarbon solvents provides a convenient method for investigating the triplets which react with conventional solvents by hydrogen abstraction. Constants for quenching of benzophenone triplet by ethanol, cyclohexane and benzene, and for quenching of acetophenone triplet by ground-state acetophenone have been measured. Irradiation of perfluorocarbon solutions of benzophenone containing small amounts of cyclohexane, or concentrated perfluorocarbon solutions of acetophenone alone, causes precipitation of photoproducts. The solvents thus show promise for investigating the photochemical reactions of such aromatic ketones.