Photolysis reaction mechanism of dibenzophenoneoxime hexamethylenediurethane, a new type of photobase generator

The photochemical and photophysical phenomena of dibenzophenoneoxime hexame thylenediurethane have been investigated with laser flash photolysis to und erstand its participating mechanism in polymer curing reactions. Owing to t he extremely short Lifetimes of the first excited singlet (22 ps) and tripl et (10 ns) (n, pi*) states, that the molecules undergo, with a small quantu m efficiency of 10(-4), decarboxylation at the lowest triplet state with th e rate constant of 10(6) s(-1), forming dehydrogenated iminyl and aminyl ra dicals. Abstracting a hydrogen atom in the time scale of 270 mu s, the imin yl radical converts mainly into diphenyl-1-imine which, with being irradiat ed, dehydrogenates and dimerizes to yield benzophenone azine. Meanwhile, th e aminyl radical abstracts H to generate benzophenoneoxime-urethanyl hexame thyleneamine, which, as a photobase, raises solution pH. (C) 1999 Elsevier Science S.A. All rights reserved.