Intrazeolite photochemistry. photochemistry of 1-azaxanthone in zeolites in the presence of hydrogen donors, electron donors, and energy accepters

The photochemistry and photophysics of 1-azaxanthone included in faujasite zeolites have been examined. In organic solvents, 1-azaxanthone has been fo und to be a better H-abstractor than benzophenone, which led to the idea of its use as a probe for radical reactions in heterogeneous systems. However , in the highly polar zeolite interior, mixing of n,pi* and pi,pi* states o f 1-azaxanthone occurs, resulting in reduced probe reactivity. The reaction s of excited 1-azaxanthone included in NaY in the presence of other organic guests in the supercages were also monitored. Go-inclusion of small amount s of basic molecules such as pyridine and triethylamine led to a substantia l increase in the triplet lifetime. Larger amounts of triethylamine resulte d in ketyl radical anion formation, and addition of 2-propanol, a good hydr ogen donor, resulted in some ketyl radical formation along with another tra nsient. This second transient is ascribed to the cyclohexadienyl radical of 1-azaxanthone. Inclusion complexes of benzophenone in NaY were also prepar ed and the reactivity was compared to the 1-azaxanthone inclusion complexes .