Single-photon ionization of pyrene and anthracene giving trapped electrons in alkali-metal cation-exchanged zeolites X and Y: a direct time-resolved diffuse reflectance study

Dynamics of the transient species generated upon photolysis of diarylmethanes within zeolites — Deprotonation and oxidation reactions

“…Consistent with this mechanism is the observation of short-lived Na 3 2+ clusters at wavelengths greater than 510 nm (Fig. 1a) produced when electrons are trapped by the counterbalancing sodium cations (10,13,(31)(32)(33).…”

“…It is well-established that radical cations of organic mate- rials incorporated within zeolites can be generated by direct irradiation of the precursor with the zeolite framework acting as the electron acceptor (10,21). The results obtained in the present work provide either direct or indirect evidence that each of the four diarylmethanes do undergo photoionization within the cation-exchanged Y-zeolites.…”

“…The presence of tetravalent aluminum gives rise to a net negative charge in the backbone, which must be balanced with a charge-balancing cation, typically alkali metals or protons. While the void cavities and channels of the zeolite are capable of accommodating molecular guests, zeolites are not simply inert vessels, but have been shown to participate as electron donors and acceptors in both thermal (7,8) and photoinduced (9)(10)(11)(12)(13)(14) electron transfer reactions. The high density of negative charge on the zeolite framework is thought to provide an environment well-suited for the generation of positively charged species and in fact, carbocations can be thermally generated within proton-exchanged zeolites (15).…”

“…Organic radical cations formed within the zeolite framework have also been the subject of much interest. Photoionization reactions leading to radical cation formation have been shown to be easily carried out within zeolite frameworks, making zeolites convenient host materials to study the photoinduced formation of radical cations (10,21).…”

Resolution of Ultrafast Pyrene Excimer Emission Rise Times in Zeolites X and Y†

“…Although emission from the monomer exhibits characteristic vibrational structure that is polarity dependent (l), excimer emission is broad, featureless and centered at longer wavelengths (2). These distinct luminescent properties have made pyrene a favorite photophysical probe for investigating the interior properties of a wide range of zeolites (3–10), including X and Y faujasite zeolites. Faujasites are aluminosilicate materials that have an open framework structure composed of linked SiO 4 4– and AlO 5 – 4 tetrahedra arranged into sodalite cages (11–16).…”