Intermolecular interactions of inorganic and organic molecules embedded inzeolite-type materials probed by near-infrared Fourier transform Raman spectroscopy

Near-infrared Fourier transform Raman spectroscopy represents an excellentl y suited tool to investigate spectroscopically inorganic and organic molecu les occluded in zeolite-type materials as well as interactions between them . Two examples are presented: First, insertion compounds of iodine in vario us microporous SiO2 modifications (deca-dodecasil 3R, all-silica theta-1 an d silicalite-1) are discussed. Intermolecular interaction between the inser ted molecules is prevented by occlusion of iodine in the cages of deca-dode casil 3R, but is allowed in the insertion compounds of hosts with higher po re dimensionalities. The intermolecular coupling is confirmed by an appreci able reduction of the Raman shifts, as observed similarly for liquid and am orphous iodine. The second example deals with pyridine and rt-alkylamines ( n-propyl-, n-butyl- or n-pentylamine) occluded during synthesis in all-sili ca ferrierite. Raman spectra reveal for all compounds, regardless of the n- alkylamine used, an interaction between the n-alkylamine and neighboring py ridine molecules, with both amines being located in the ten-membered ring c hannels. For this reason, it is proposed that bimolecular complexes, consis ting of an n-alkylamine weakly bound to a pyridine molecule act as structur e-directing agents during synthesis. (C) 1999 Elsevier Science B.V. All rig hts reserved.