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Controlling chemistry with cations: photochemistry within zeolites

Ramamurthy, V and Shailaja, J and Kaanumalle, Lakshmi S and Sunoj, RB and Chandrasekhar, J (2003) Controlling chemistry with cations: photochemistry within zeolites. In: Chemical Communication (16). pp. 1987-1999.

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Abstract

The alkali ions present in the supercages of zeolites X and Y interact with included guest molecules through quadrupolar (cation\pi-), and dipolar (cation–carbonyl) interactions. The presence of such interactions can be inferred through solidstate NMR spectra of the guest molecules. Alkali ions, as illustrated in this article, can be exploited to control the photochemical and photophysical behaviors of the guest molecules. For example, molecules that rarely phosphoresce can be induced to do so within heavy cation-exchanged zeolites. The nature (electronic configuration) of the lowest triplet state of carbonyl compounds can be altered with the help of light alkali metal ions. This state switch (n\pi*–\pi\pi*) helps to bring out reactivity that normally remains dormant. Selectivity obtained during the singlet oxygen oxidation of olefins within zeolites illustrates the remarkable control that can be exerted on photoreactions with the help of a confined medium that also has active sites. The reaction cavities of zeolites, like enzymes, are not only well-defined and confined, but also have active sites that closely guide the reactant molecule from start to finish. The examples provided here illustrate that zeolites are far more useful than simple shape-selective catalysts.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre: Division of Chemical Sciences > Organic Chemistry
Date Deposited: 17 Dec 2008 05:28
Last Modified: 19 Sep 2010 04:53
URI: http://eprints.iisc.ernet.in/id/eprint/16698

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