Topological quenching of 2,4,6-triphenylpyrylium tetrafluoborate in anionic micelles

Topological quenching of the excited states of the photosensitizer 2,4,6-tr iphenylpyrylium tetrafluoborate bound to an anionic SDS micelle has been ob served by fluorescence spectroscopy. Spectroscopic data suggests that the t riphe nylpyrylium cation is micellized with the cationic pyrylium moiety sl ightly projecting out, experiencing the aqueous polar environment. Accordin gly, the quenching mechanism varied from static for neutral quenchers and d ynamic for the cationic quenchers whereas no quenching was observed for ani onic quenchers. Upon irradiation, micellized TP+ undergoes a photoinduced h ydrolysis to 1,3,5-triphenyl-1-pentene-1,5-dione, possibly through an elect ron transfer between triplet excited pyrylium cation and water molecules. T his electron transfer leads to the generation of hydroxyl radicals producin g the build-up of 10(-2) M hydrogen peroxide. (C) 2001 Elsevier Science B.V . All rights reserved.