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.
Hexakis(4-methoxyphenyl)benzene (HPB-OMe(1)) and hexakis(2,6-dimethyl-4-methoxyphenyl)benzene (HPB-OMe(2)) were synthesized via organometallic complex catalysis. The treatment of HPB-OMe(1) with FeCl3 caused cyclodehydrogenation at two positions to yield an oligophenylene with an indeno[1,2-<i>b</i>]fluorene structure (IF-OMe). Deprotection of the methoxy groups of these compounds was conducted by treatment with BBr3. Deprotonation of the OH groups of HPB-OH(1), HPB-OH(2), and IF-OH through treatment with NaH caused a bathochromic shift in the absorption and photoluminescence (PL) peaks. The bathochromic shift of the deprotonated species increased with the donor number (DN) of the solvents. These observations can be explained as the consequence of intramolecular charge transfer (ICT) from the ONa groups to the inner benzene rings
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