SHAPE-SELECTIVE PHOTOSENSITIZED ISOMERIZATION OF STILBENE USING A BENZOPHENONE INCORPORATED WITHIN ACID ZEOLITES

A series of heterogeneous photosensitizers has been obtained by immobi lization of 4-aminobenzophene (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/V is spe ctra of the composites. ABP when included within HZSM-5 (ABP-HZSM-5) b ehaves as the first shape-selective photosensitizer. Thus, trans-stilb ene could be photochemically isomerized to cis-stilbene in the presenc e of ABP-HZSM-5, while the reverse cis to trans isomerization failed. According to the relative dimensions of the zeolite hosts, ABP incorpo rated within HY, H beta and HMOR showed no remarkable difference in th e isomerization efficiency of both stilbene isomers.