Photochemistry of triarylsulfonium salts

Photo Lewis acid generators: photorelease of B(C6F5)3 and applications to catalysis

“…40 In the absence of acetonitrile as trapping reagent, photolysis of CD 2 Cl 2 solutions of 1-Ph 3 S and 1-Ph 2 I gives B(C 6 F 5 ) 3 ; however, the reactions were found to be less clean due to slow photodecomposition of borane, shown in separate experiments. We have previously suggested the mechanism of borane photorelease from 1-Ph 3 S. 34 An analogous mechanism can be envisioned for the ion par 1-Ph 2 I with diphenyliodonium cation being the source of protons 30 instead of triphenylsulfonium cation 29 (Scheme 2). Taking into account the negligible basicity of the carbazolide nitrogen centre due to the conjugation of its lone pair with the aromatic system (the pK a of the conjugated acid of carbazole is −4.9), 41 we proposed that the reaction starts with the photoinduced protonation of the carbonyl group of the anion, which results in the formation of a zwitterionic intermediate 1-H.…”

“…Examples of external stimuli include heat, 24 mechanical force 25 or, more commonly, irradiation with a specific wavelength of light. [26][27][28] Light-induced catalysis is of particular importance in the area of photolithography, where photoacid generators (PAGs) eject protons upon irradiation, 29,30 which mediate the deprotection of photoresist polymers and allow for patterning to sub-20 nm resolution. Given the importance of B(C 6 F 5 ) 3 and other perfluoroaryl boranes as Lewis acid catalysts for siloxane synthesis and modification, we became interested in devising molecules that, when irradiated, would liberate this borane.…”

Building pH Sensors into Paper-Based Small-Molecular Logic Systems for Very Simple Detection of Edges of Objects

“…Figure 2b shows that 1 is largely preserved during irradiation, whereas 2 is significantly decomposed (into 3 and H + ). 46 It is worth reiterating that the irradiated areas are understood to show XOR logic using light dose inputs [40][41][42] and fluorescence output. On the other hand, no logic assignment can be made in a similar manner to the visualized edges themselves or to the unirradiated areas since the light dose is not supplied directly to those places.…”

Resist Materials and Processes for Extreme Ultraviolet Lithography

“…61) In photoresists, polymer absorption generally interferes with acid generation, although some acids are generated through so-called polymer sensitization (the energy or electron transfer from excited polymers to acid generators). 62,63) Tremendous efforts have been devoted to the reduction in polymer absorption during the development of KrF, ArF, and F 2 resists. Because the direct excitation of acid generators by incident photons is a major process of acid generation in photoresists, the absorption of resist films is optimized by adjusting the concentration or absorption coefficient of acid generators.…”