Intrazeolite Photochemistry. 16. Fluorescence of Methylviologen Adsorbed within Medium- and Large-Pore Zeolites

Abstract

Methylviologen (MV2+) incorporated within medium- and large-pore zeolites (NaZSM-5, Namordenite, NaY, and CsY) emits fluorescence at 330 and 420 nm; the latter is most prominent in zeolite NaY. The intensity ratio between these two bands depends on the structure of the zeolite. On the basis of molecular modeling and 13C CP/MAS NMR using the dipolar dephasing technique, the first band has been ascribed to the emission of MV2+ in a planar conformation. The unprecedented 420 nm band has been attributed to a twisted conformer probably interacting with the basic oxygen sites of the framework.