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.

No abstract

Photochromic terarylene having a methoxy group and hydrogen as the leaving units at the photochemical reaction center carbon atoms has been synthesized. This molecule shows irreversible photochemical reaction affording a highly fluorescent condensed aromatic molecule.

4,5‐Dibenzothienylthiazole derivatives having leaving groups at the reactive 2‐positions of benzothiophene rings have been synthesized, and their photochromic ring‐closing reaction followed by spontaneous elimination and substitution reactions have been studied. A 4,5‐dibenzothienylthiazole having an ethoxy group and a hydrogen atom at each 2‐position of the benzothienyl ring underwent elimination to generate a condensed aromatic structure upon the addition of acid. 4,5‐Dibenzothienylthiazoles having an ethoxy or methyl groups at the 2‐position of the benzothienyl rings showed photochromism both in hexane and in methanol solutions with photocyclization quantum yields as high as 60 %. Upon the addition of acid to the methanol solutions of closed‐ring isomers of dibenzothienylthiazoles, the substitution of the ethoxy group with a methoxy group occurred. The generation and rearrangement of the carbocation intermediate formed by elimination of the ethoxy group from the closed‐ring isomers were apparent from the chemical structure of methoxy‐substituted products.

No abstract