COMPARATIVE PHOTOCHEMICAL BEHAVIOR OF SOME ANTHRACENYL AND NAPHTHACENYL SULFONIUM SALT DERIVATIVES

A series of anthracenyl and naphthacenyl mono- and bis-sulfonium salts was synthesized and their spectroscopic, redox and photoacid behavior investigated. When the thermodynamics of photoinduced electron transf er (PET) bond cleavage in the sulfonium salt derivatives is weakly exo thermic, i.e. Delta G(ET)degrees = -1.8 kcal mol(-1), the rate of PET does not compete effectively with the rate of decay of the first excit ed singlet state by fluorescence emission. When Delta G(ET)degrees is more exothermic than about 5 kcal mol(-1), the fluorescence emission i s quenched and PET bond cleavage takes place. The quantum yield of aci d formation (phi(H+)) in acetonitrile for the napthacenyl and anthrace nyl sulfonium salt derivatives is in the range 0.003-0.28. In the anth racenyl sulfonium salts, the electron-withdrawing requirements of the substituent groups on the sulfonium moiety are greatly relaxed over th e naphthacenyl derivatives due to the higher energy pi level of the a nthracene moiety.