Photogeneration and migration of electrons and holes in zeolite NaY

Electron transfer and charge migration between electron donors and acceptors encapsulated within dry NaY zeolites a-re explored using nanosecond laser flash photolysis. The role of the zeolite in these redox processes is examined in order to characterize the intrazeolite mobility of electrons and holes, Electron migration is initiated by photoexciting trans-anethole in NaY containing coadsorbed 1,4-dicyanobenzene as an electron acceptor, while hole migration is initiated by photoexciting chloranil in NaY containing coadsorbed 4,4'-dimethoxybicumene as all electron donor. The experimental results demonstrate that ultrafast redox reactions (> 10(8) s(-1)) take place, leading to long-lived charge separated species within the zeolite cavities. The efficiency of these redox processes is examined as a function of donor-acceptor concentration and the presence of nitrous oxide as an electron trap. Interpretation of the experimental data with two independent models provides evidence that the redox chemistry occurring within NaY cannot be completely accounted for by contact interactions between the incorporated molecules. From these models, it is estimated that the zeolite can mediate electron and hole migration over vacant, through-space distances of 11 and 18 Angstrom, respectively.