Mechanism of Reaction and Photoacid Generation of 1,2-di(Arylsulfonyl)hydrazine PAGs:  A Laser Flash Photolytic Study

Abstract

The photochemical behavior of four 1,2-di(arylsulfonyl)hydrazine photoacid generators has been studied by means of nanosecond laser flash photolysis (λ = 266 nm) and steady-state photolysis (λ = 254 nm) with the aim of understanding the reactions involved in photoacid generation. Upon photoexcitation, homolytic cleavage of the S−N bond results in the formation of arylsulfonyl radicals. The nitrogen-centered radical that also results from this cleavage decomposes to yield another arylsulfonyl radical. The arylsulfonyl radical generates acid via reaction with oxygen to yield a peroxysulfonyl radical, which subsequently reacts with a hydrogen donor to yield a peroxysulfonic acid. The sulfonic acids detected in product studies are presumed to be the stable decomposition products of these peroxysulfonic acids. Desulfonylation of the arylsulfonyl radical to generate SO 2 is a very minor pathway that occurs in competition with acid generation. Photoacid generation quantum yields upon laser excitation were found to range from 0.05 to 0.1.