Mechanisms of Photoreactions in Solution. XXI.¹ Quenching of Excited Singlet States of Benzophenone

Abstract

Tris (dibenzoylmethanato) iron (III) and tris (dibenzoylmethanato) chromium (III) show exceptionally high reactivity as quenchers in the photoreduction of benzophenone by benzhydrol. The dependence of the effect on the concentrations of the quenchers suggests that, in addition to benzophenone triplets, excited singlet states of the ketone are deactivated by the chelates. Study of the effects of the two chelates on the benzophenonesensitized isomerization confirms the singlet quenching. Singlet quenching occurs at lower concentrations than would have been predicted by approximate theories.

Fluorescence enhancement of dibenzo-18-crown-6 by alkali metal cations

“…intersystem crossing yield for Sx -* Tx, approximately holds in a rigid MeOH-EtOH matrix at 77 K, since there was no appreciable photochemical reaction of the DC-M+ complexes. The values of µ can be calculated from eq 2 where the values at 77 K are given in Table I…”