Effect of cyclodextrin complexation on the photochemistry of p-methoxy-β-phenylpropiophenone

Abstract

p-Methoxy-β-phenylpropiophenone triplets undergo efficient intramolecular deactivation by a mechanism that involves quenching of the carbonyl triplet by the aromatic ring. Inclusion of the ketone in either β- or γ-cyclodextrins leads to protection from external, water-soluble quenchers, such as nitrite or cupric ions. The triplet lifetime for the included ketone is longer in γ-cyclodextrin than in water; in contrast, β-cyclodextrin has virtually no effect on the lifetime in spite of quenching experiments which suggest that inclusion is efficient. It is suggested that the long lifetime in γ-cyclodextrin reflects inclusion of both rings, which cannot be achieved in the smaller cyclodextrin cavities.