TRIPLET-STATE PROPERTIES OF FLAVONE IN HOMOGENEOUS AND MICELLAR SOLUTIONS - A LASER FLASH-PHOTOLYSIS STUDY

The triplet state properties of flavone (2-phenylchromone) have been i nvestigated by laser flash photolysis. Excitation at 337 nm was carrie d out by means of a nitrogen laser. The T-T absorption spectrum was de termined in homogeneous solvents (benzene, ethanol, acetonitrile) and in micellar solutions of SDS, CTAC and Brij 35. The position of the tw o maxima at 370 and 620 nm was practically independent of the solvent. The self-quenching rate constants were determined in homogeneous solv ents and are in the range 1.8-3.0 x 10(8) dm(3) mol(-1) s(-1). The eff ect of surfactant concentration on the yield and decay of the triplet was investigated. The self-quenching was greatly diminished in the mic ellar systems. The results could be explained by considering the flavo ne as totally micellized. The quenching by amines was also studied in the three solvents. The rate constants correlate with the oxidation po tential of the amine and a new long-lived transient appears which was attributed to the flavone ketyl radical.