Polarized absorption spectroscopy on microcrystals An essential tool for the characterization of zeolite new materials

The application of polarized absorption spectroscopy as a powerful method in the characterization of modified zeolitic molecular sieve crystals can supply information on (i) the electronic states, (ii) the alignment 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 AIPO₄-5), the incorporation of ions (Se₂ anions in cancrinite), and the encapsulation of metal complexes (cobalticinium, [Co^III(ν5-C₅H₅)₂]⁺ in nonasils). The adsorption of chromophores (p-nitrodimethylaniline in AlPO₄-5) is shown as an important post-synthesis modification