TRIARYLMETHYLIUM CATIONS ENCAPSULATED WITHIN ZEOLITE SUPERCAGES

A series of substituted triarylmethylium cations, including malachite green, tris(4-methoxyphenyl)methylium, and bis(4-methoxyphenyl)phenylm ethylium cations, has been prepared adsorbed on tridirectional large p ore zeolites Y and beta in their H+ or La3+ form, as well as within th e novel mesoporous aluminosilicate MCM-41, by ship-in-a-bottle synthes is from the corresponding benzaldehyde and N,N-dimethylaniline or anis ole. The resulting composites exhibit diffuse reflectance and IR spect ra characteristic of these trityl dyes. The cation content was determi ned by thermogravimetry-differential scanning calorimetry. Preparation of these triarylmethylium cations exclusively on the external surface of ZSM-5, a medium pore zeolite whose internal voids are too small to accommodate these cations, is also possible. Therefore, the methodolo gy based in the diffusion of smaller precursors does not guarantee its elf the intrazeolite location of the synthesized guests. In this work, we have experimentally determined that the dyes are blocked in the in terior of the faujasite pores, Thus, direct evidence showing the locat ion of the organic material inside the zeolite supercages was obtained using X-ray diffraction and X-ray photoelectron spectroscopy. These d yes incorporated within microporous solids can act as heterogeneous ph otosensitizers to promote the sensitized dimerization of 1,3-cyclohexa diene.