Intrazeolite Photochemistry. 11. Modification of the Properties of the Energy-Transfer Photosensitizer 4-Aminobenzophenone by Immobilization within Different Zeolite Microenvironments

4-Aminobenzophenone (ABP) has been incorporated within the internal voids of four acid zeolites (HY, Hβ, HMor, and HZSM5) and the resulting composites characterized by diffuse reflectance, thermogravimetric analysis−differential scanning calorimetry, and FT-IR. Time-resolved diffuse reflectance of these composites showed that the photochemistry of ABP within these solids after laser excitation is extremely dependent on the zeolite microenvironment. The transient reflectance spectrum obtained for the ABP−HY composite closely resembles the transient absorption spectrum for ABP in polar solvents. However, the transient reflectance spectrum obtained for the ABP−HZSM5 composite shows one maximum at 530 nm, due to the T−T absorption of ABPH + triplet. A different situation was found for the ABP−Hβ and ABP−HMor composites, where besides the reflectance at 530 nm, other bands were present. In addition, the zeolite framework also modifies how ABP behaves as a photosensitizer. The use of these composites as heterogeneous photosensitizers was explored by performing the photosensitized dimerization of 1,3-cyclohexadiene as a model reaction. Cyclobutane [2+2] dimers were the main products, indicating that an energy-transfer reaction is the predominant mechanism under these conditions.