Photochemistry of diaryliodonium salts

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

“…Both of these products were confirmed to originate from the hydridoborate by repeating the reaction with While the origin of benzene is relatively clear, the identity and origin of the product giving rise to the signal at 3.42 ppm was shown to be a result of reaction of photoproduced phenyl cation and the acetonitrile solvent. 55 Analysis using 13 30 Although it is plausible that adduct formation between this by-product and B(C 6 F 5 ) 3 could happen, we do not observe this. It is known that N-alkyl anilines form very weak adducts with B(C 6 F 5 ) 3 57 and so acetonitrile easily displaces this base.…”

“…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.…”

“…The photodegradation of the Ph 3 S + and Ph 2 I + cations has been studied in some detail and most of the products we observe can be rationalized on the basis of these earlier studies. 29,30 Essentially 53 ), indicating that the phenyl cation can also liberate borane by abstraction of the hydride (deuteride) from the counteranion. Photolysis of PhLAGs 7 in acetonitrile, which was used to quantify the efficiency of borane release through formation of CD 3 CN·B(C 6 F 5 ) 3 , was also examined.…”

Reaction Mechanisms of Excimer Resists Studied by Laser Flash Photolysis.

“…It is important to clarify the reaction mechanisms from the point of view of the effective development of microlithography techniques. Many papers on product analysis of acid genertor for KrF (248 nm) excimar laser and i-line (365 mn) have been reported [8][9][10][11][12][13]. And papers on flash photolysis of acid generator, such as a 347 nm nano-second flash and a 265 nm femto-second flash have been reported [14,15].…”