Zeolites can be used as photoreactors to control the outcome of chemical reactions in the solid state. In the case of photochemical reactions it is possible to monitor the reaction intermediates involved in these processes using time resolved laser techniques.

In our case we have selected the zeolite NaY as the `host' in these supramolecular systems. NaY has supercages of approximately 13 Å in diameter which are accessible through four windows of approximately 7.4 Å in size. The `guests' are a variety of aromatic ketones and our first choice as `spectator' is pyridine, a molecule that shows high affinity towards the acid sites in zeolites. The molecules tested are:

(I) Xanthone, which is capable of reporting on the polarity of the environment in the zeolite cavity.
(II) p-Methoxy-ß-phenylpropiophenone, which undergoes an efficient excited triplet deactivation, and can report on mobility within the zeolite cavity.
(III) Hexanophenone, which undergoes the Norrish Type II photofragmentation. The cyclization-to-fragmentation ratios (cyclobutanols-to-acetophenone) can contain information on the ability of this molecule to achieve the conformation required for each of the photoproducts to form.

The combination of time resolved and product studies in these systems is anticipated to provide a detailed view of the way in which `spectators' can modify the environment perceived by the guests, and the photochemical and photophysical processes in which they participate.

12-aug-96