Role of β-phenyl rings in the deactivation of aromatic ketone triplets

Abstract

The four aromatic ketones investigated were shown to be photostable in solution. Laser flash photolysis experiments show that this photostability is the result of highly efficient triplet deactivation processes that lead to very short triplet lifetimes; for example for β-phenylpropiophenone the triplet lifetime in toluene at room temperature is about 1.0 ns. Structural effects on the nature and lifetime of the triplet state indicate that its deactivation requires the interaction of the carbonyl chromophore with the π system in the β-phenyl ring; a short-lived charge transfer intermediate may be involved in the process.