Mechanism of Reaction and Photoacid Generation of <i>N</i>-Oxysuccinimidoarylsulfonate PAGs:  A Laser Flash Photolytic Study

Abstract

The photochemical behavior of four N -oxysuccinimidoarylsulfonate photoacid generators (PAGs), 1-[[phenylsulfonyl]oxy]- (PSPD), 1-[[(4-methylphenyl)sulfonyl]oxy]- (MSPD), 1-[[(4-fluorophenyl)sulfonyl]oxy]- (FSPD), 1-[[(4-chlorophenyl)sulfonyl]oxy]-2,5-pyrrolidinedione (CSPD), has been studied by means of nanosecond laser flash photolysis (λ exc = 266 nm) and steady-state photolysis (λ exc = 254 nm) with the aim of understanding the reaction mechanism and, particularly, photoacid generation pathways and efficiency in the deep UV region. Upon photoexcitation, the formation of arylsulfonyl radicals and their subsequent desulfonylation were detected for the four PAGs. In oxygen-saturated solution, the generation of the corresponding arylperoxy radicals was also observed. Photoacid generation quantum yields upon laser excitation were found to range from 0.04 to 0.05. Product studies following steady-state irradiations reveal that acid generation is dominated by the formation of sulfonic acids.