POLARIZED ABSORPTION-SPECTROSCOPY ON MICROCRYSTALS - AN ESSENTIAL TOOL FOR THE CHARACTERIZATION OF ZEOLITE NEW MATERIALS

The application of polarized absorption spectroscopy as a powerful met hod in the characterization of modified zeolitic molecular sieve cryst als can supply information on (i) the electronic states, (ii) the alig nment of zeolite-hosted colouring guests, and (iii) the concentration of the colouring species at very low loadings. The following examples are reported for modifications brought about during the synthesis: the isomorphous framework substitution (Co-II in AlPO4-5), the incorporat ion of ions (Se-2 anions in cancrinite), and the encapsulation of meta l complexes (cobalticinium, [Co-III(eta(5)-C5H5)2](+) in nonasils). Th e adsorption of chromophores (p-nitrodimethylaniline in AlPO4-5) is sh own as an important post-synthesis modification.