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

Abstract

4-Aminobenzophenone (ABP) has been incorporated within the internal voids of four acid zeolites (HY, H , HMor, and HZSM5) and the resulting composites characterized by diffuse reflectance, thermogravimetric analysis-differential scanning calorimetry, and FT-IR. Timeresolved 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-H 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.

Intrazeolite Photochemistry. 13. Photophysical Properties of Bulky 2,4,6-Triphenylpyrylium and Tritylium Cations within Large- and Extra-Large-Pore Zeolites

“…into the channels of medium-pore zeolites, large differences in the transient absorption spectra upon going from ZSM-5 to large-pore zeolites have been observed. 5,7 Similar precedents showing different behavior in ZSM-5, such as room-temperature phosphorescence of R,ω-diphenylpolyenes which is not observed for large-pore zeolites, has also been reported and attributed to a tight fit of the guest inside the ZSM-5 channels. 18,19 According to the tight-fit interpretation, this phenomenon is due not to any intrinsic property of ZSM-5 but to molecular orbital distortions and Coulombic interactions owing to spatial confinement experienced by the guest.…”

Probing the Polarity of Various Cellulose Derivatives with Genuine Solvatochromic Indicators

“…The bathochromic UV/Vis shift observed for 3 with increasing HBD capacity [negative sign of the coefficient a from Equation (1)] indicates a co‐ordination of accessible H‐atoms of the CTs surface upon the lone electron pair of the carbonyl oxygen. A similar result is observed when 3 is encapsulated in cavities of HY zeolites48 or adsorbed on poly(amino acids) 11. Therefore, β values for CTs cannot be determined with 3 as surface polarity indicator.…”

Zeolite-based photocatalysts

“…In order to obtain a truly heterogeneous energy transfer photocatalyst, 4-amino benzophenone has been adsorbed on acid zeolites. 53 It was hoped that an acid-base reaction will anchor the weakly basic 4-aminobenzophenone by protonation of the -NH 2 group providing an ionic bond to the solid (Scheme 10).…”