Shape-selective photosensitized isomerization of stilbene using a benzophenone incorporated within acid zeolites

A series of heterogeneous photosensitizers has been obtained by immobilization of 4-aminobenzophenone (ABP) within acid zeolites of medium and large pore size. The strong interaction between the amino substituent of ABP and the acid sites of the zeolite is revealed by the red-shift (ca. 50 nm) of the long wavelength absorption band in the UV/Vis spectra of the composites. ABP when included within HZSM-5 (ABP-HZSM-5) behaves as the first shape-selective photosensitizer. Thus, trans-stilbene could be photochemically isomerized to cis-stilbene in the presence of ABP-HZSM-5, while the reverse cis to trans isomerization failed. According to the relative dimensions of the zeolite hosts, ABP incorporated within HY, Hβ and HMOR showed no remarkable difference in the isomerization efficiency of both stilbene isomers.