Photochemistry of N‐Arylsulfonimides: An Easily Available Class of Nonionic Photoacid Generators (PAGs)

Abstract

The photochemical behavior of differently substituted N-arylsulfonimides was investigated. Homolysis of the S-N bond took place as the exclusive path from the singlet state to afford both N-arylsulfonamides and photo-Fries adducts, the amount of which depended on reaction conditions and aromatic substituents. Sulfinic and sulfonic acids were released upon irradiation under deaerated and oxygenated conditions, respectively. The nature of the excited states and intermediates involved were proved by laser flash photolysis and EPR experiments. These results highlighted the potential of such compounds as nonionic photoacid generators able to photorelease up to two equivalents of a strong acid for each mole of substrate.

Simultaneous Photografting of Two Organic Groups on a Gold Surface by using Arylazo Sulfones as Single Precursors

“…The presence of methanesulfonyl groups on the gold surface is in agreement with previous studies, indicating that sulfonyl radicals (both methanesulfonyl and arylsulfonyl radicals) can be generated via photolysis of different aromatic substrates, including arylsulfonates and N -arylsulfonimides . The absence of these groups as substituents on the grafted aryl moieties is in agreement with these previous photochemical experiments where such electrophilic species poorly react with arenes bearing electron-withdrawing substituents (e.g., CH 3 CO−), while they are efficiently trapped by electron-rich aromatics.…”

N‐Arylsulfonimides as Photoinitiators for Cationic Polymerization of Epoxy Sol‐Gel Materials

“…The degree of polymerization of compound 4 is quite similar to that obtained with commercial DPST. On the contrary, trifluoromethanesulfonimide 5 exhibited a modest efficiency (see Figure c) due to its inability to release strong sulfonic acids …”

“…Recently we have demonstrated that irradiation of N ‐arylsulfonimides (e.g. 1‐5 ) in air saturated acetonitrile caused likewise the release of sulfonic acids (up to two equivalents, 200% yield, for compounds 1‐4 , Scheme ) …”

“…Accordingly, compounds 1‐5 were tested as photoinitiators in the acid‐induced polymerization of an epoxy‐based hybrid organic‐inorganic system obtained via a sol‐gel process and then used to achieve micrometric patterns on the same materials by UV photolithography. Compound 5 was tested as well though only weak acids such as HF and H 2 SO 3 were released in solution …”

Recent Progress in Photo-Acid Generators for Advanced Photopolymer Materials

“…Typical structures and photochemical reaction mechanisms of non-ionic PAGs are shown in Table 1 [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”