FRACTION OF EXCITED-STATE OXYGEN FORMED AS B(1)SIGMA(-PHASE-PHOTOSENSITIZED REACTIONS .2. EFFECTS OF SENSITIZER SUBSTITUENT()(G) IN SOLUTION)

The fraction F(S)igma of excited-state oxygen formed as b (1) Sigma(g) (+) was determined for a series of triplet-state photosensitizers in C Cl4 solutions. F-Sigma was determined by monitoring the intensities of (a) O-2(b (1) Sigma(g)(+)) fluorescence at 1926 nm (O-2(b (1) Sigma(g )(+)) --> O-2(a (1) Delta(g))) and (b) O-2(a (1) Delta(g)) phosphoresc ence at 1270 nm (O-2(a (1) Delta(g)) --> O-2(X(3) Sigma(g)(-))). Oxyge n excited states were formed by energy transfer from substituted benzo phenones and acetophenones. The data indicate that F(S)igma depends on several variables including the orbital configuration of the lowest t ripler state and the tripler-state energy. The available data indicate that the sensitizer-oxygen charge transfer (CT) state is not likely t o influence F-Sigma strongly by CT-mediated mixing of various sensitiz er-oxygen states.