THE REACTION OF BIPHENYLS IN THE UPPER TRIPLET-STATES IN MICELLAR SYSTEMS

Reactions of the upper triplet states of biphenyl and its halogenated derivatives were investigated in aqueous micellar systems at room temperature with a two-step excitation method. Irradiation of the triplet states of biphenyl and its chloro and bromo derivatives produced hydrated electrons (e(aq)-) and a decrease in the triplet states. No evidence of carbon-halogen bond homolysis, with a rate competing with e(aq)- formation (tau < 1 ps), was obtained for the compounds investigated. The yield of photo-ionization was markedly reduced in a cationic micelle, i.e cetyltrimethylammonium bromide, compared with that in an anionic micelle, i.e. sodium dodecylsulfate. This is because of the enhanced geminate recombination of electron-cation pairs caused by the positive micellar surface charge which prevents the escape of electrons from the cationic micelle.