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

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 sp3 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.