CONDENSATION OF PYRROLE WITH ALDEHYDES IN THE PRESENCE OF Y-ZEOLITE AND MESOPOROUS MCM-41 ALUMINOSILICATE - ON THE ENCAPSULATION OF PORPHYRIN PRECURSORS

Condensation of pyrrole and benzaldehyde was carried out in isooctane or cyclohexane in the presence of MCM-41, HY (Si/Al 15) and CoY (Si/Al 2.6). In all cases, formation of tetraphenylporphyrin (TPP) was obser ved in the organic solutions, even after dissolving with hydrofluoric acid the resulting MCM-41 solid employed in the condensation. In addit ion, some reaction intermediates containing one to two pyrrole heteroc ycles were also characterized in these solutions. In spite of this, th e diffuse reflectance and IR spectra of the organic material adsorbed in the aluminosilicates after the condensation reaction were remarkabl y different from those characteristic of TPP. This discrepancy indicat es that the material adsorbed inside the solid pores is not TPP but mo st probably any of its immediate porphyrinogen precursors. In this reg ard, the coincidence of the diffuse reflectance spectra obtained after the synthesis with those characteristic of porphomethenes and porphod imethenes was noted. Condensation of pyrrole and acetaldehyde follows the same pattern: lack of formation of meso-tetramethylporphyrin (TMP) inside the pores according to diffuse reflectance and IR spectroscopi es, but detectable amounts of TMP in the organic solutions.