Intrazeolite Photochemistry. Photochemistry of 1-Azaxanthone in Zeolites in the Presence of Hydrogen Donors, Electron Donors, and Energy Acceptors

The photochemistry and photophysics of 1-azaxanthone included in faujasite zeolites have been examined. In organic solvents, 1-azaxanthone has been found 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,π* and π,π* states of 1-azaxanthone occurs, resulting in reduced probe reactivity. The reactions of excited 1-azaxanthone included in NaY in the presence of other organic guests in the supercages were also monitored. Co-inclusion of small amounts of basic molecules such as pyridine and triethylamine led to a substantial increase in the triplet lifetime. Larger amounts of triethylamine resulted in ketyl radical anion formation, and addition of 2-propanol, a good hydrogen donor, resulted in some ketyl radical formation along with another transient. This second transient is ascribed to the cyclohexadienyl radical of 1-azaxanthone. Inclusion complexes of benzophenone in NaY were also prepared and the reactivity was compared to the 1-azaxanthone inclusion complexes.