Laser Photo‐Ionization of Phenothiazine in Micellar Solution II: Mechanism and Light Induced Redox Reactions with Quinones

Abstract

AbstractThe ionization of phenothiazine incorporated in micelles of sodium laurylsulfate in water by 347.1 nm light (3.57 eV photon energy) may by explained by rapid tunneling of an electron from excited phenothiazine through the double layer into unoccupied electronic redox levels of the systems aq/eaq−. Photoionization is promoted by duroquinone (DQ) which is also solubilized in the micelles. In such a system semiquinone anion and phenothiazine cation radicals are formed via fast (< ns) intramicellar electron transfer from excited PTH and a relatively slow (μs) transfer from PTH triplets to DQ. The presence of duroquinone in a micelle prevents photoejection of electrons from phenothiazine into the water. Ionization was also achieved in cationic micelles of cetyl‐trimethyl‐ammonium‐bromide in the presence of naphthoquinone sulfonate at the periphery of the micelles. The phenothiazine/micelle/water system is an example for the heterogeneous catalysis of water decomposition by light, and the phenothiazine/micelle/quinone/water system may be regarded as a simple model for electron transfer in the photosynthetic system.