Self-Contained Photoacid Generator Triggered by Photocyclization of Triangle Terarylene Backbone

Abstract

We herein propose a new type of efficient neutral photoacid generator. A photoinduced 6π-electrocyclization reaction of photochromic triangle terarylenes triggers subsequent release of a Brønsted acid, which took place from the photocyclized form. A H-atom and its conjugate base were introduced at both sides of a 6π-system to form the self-contained photoacid generator. UV irradiation to the 6π-system produces a cyclohexa-1,3-diene part with a H-atom and a conjugate base on the sp(3) C-atoms at 5- and 6-positions, respectively, which spontaneously release an acid molecule quantitatively forming a polyaromatic compound. A net quantum yield of photoacid generation as high as 0.52 under ambient conditions and a photoinitiated cationic polymerization of an epoxy monomer are demonstrated.

Efficient Self‐Contained Photoacid Generator System Based on Photochromic Terarylenes

“…On the other hand, the photoreaction of Pre‐PAG‐1 in polar solvents such as methanol also led first to the same coloration reaction, which was followed by a subsequent bleaching reaction when the solution was kept into the darkness (Supporting Information, Figure S2). This bleaching reaction agrees with the elimination of a methanol molecule reported for analogous molecules . Along with the elimination of methanol, a polycyclic compound depicted as Post‐PAG‐1 in Scheme was formed, which was isolated by HPLC and its structure was confirmed by 1 H NMR and X‐ray crystallography (Supporting Information, Figures S3, S4).…”

“…However, the amplitude of photoinduced modulation in K a value of most pH‐switching photochromic dyes is less than two orders of magnitude, which is too small for applications in photoresist systems. Recently, we reported a self‐contained PAG molecule based on a new mechanism for the acid release . An elimination reaction of a Brønsted acid molecule was triggered by a photoinduced 6π‐electrocyclization reaction in PAG‐0 (Scheme c), as a subsequent thermal reaction.…”

“…The QY of acid generation is, therefore, determined by the photoinduced 6π‐electrocyclization reaction from PAG‐0 a to PAG‐0 b . The first self‐contained PAG‐0 was designed based on the bisthiazolylbenzo[ b ]thiophene framework which exhibited a QY of 0.52 for the release of methanesulfonic acid in toluene . Although this value is rather larger than most of practical PAGs, there should be room for substantial improvement considering the capability of the mother compound, which showed a photon‐quantitative reactivity (QY=0.98) .…”

Substitution effect on the photochromic properties of benzo[b]thiophene-1,1-dioxide based diarylethenes

“…[6][7][8][9][10][11][12] Recently, several groups have demonstrated alternative ways to expand the versatility of DAE architectures by chemically tailoring the central ethene bridges. For instances, different aryl units such as thiophene, 13 thiazole, 14 imidazolium 15 and benzothiopene 16 have been employed as the central bridge. Novel DAEs containing different ethene bridges of 1,10-phenanthroline 17 , thiophene derivatives 18,19 and methylimidazol derivatives 20 were exploited as functional organic ligands to prepare versatile metal organic complex toward regulation of phosphorescence, near-infrared photochromic behavior and gated photochromism.…”

Photoacid Catalyzed Reaction of Phenol with Styrene

“…[14][15][16][17][18] A few acid-catalyzed reaction such as esterification and cationic polymerization reaction catalyzed with protonated merocyanine photoacid has been reported as applications. 7,19 Herein we have reported the reaction of styrene with phenol using photoacid catalyst in comparison with the reaction employing common protic acid or Lewis acid. Reaction of phenol with styrene in the presence of catalyst yields the mixture of mono-, di-, and tri-styrenated phenol as shown in Scheme 1.…”