Triplet state properties of flavone in homogeneous and micellar solutions. A laser flash photolysis study

Abstract

The triplet state properties of flavone (2-phenylchromone) have been investigated by laser flash photolysis. Excitation at 337 nm was carried out by means of a nitrogen laser. The T–T absorption spectrum was determined in homogeneous solvents (benzene, ethanol, acetonitrile) and in micellar solutions of SDS, CTAC and Brij 35. The position of the two maxima at 370 and 620 nm was practically independent of the solvent. The self quenching rate constants were determined in homogeneous solvents and are in the range 1.8–3.0 × 10⁸ dm³ mol^–1 s^–1. The effect of surfactant concentration on the yield and decay of the triplet was investigated. The self quenching was greatly diminished in the micellar systems. The results could be explained by considering the flavone as totally micellized. The quenching by amines was also studied in the three solvents. The rate constants correlate with the oxidation potential of the amine and a new long-lived transient appears which was attributed to the flavone ketyl radical.