Very strong stabilization of alkene.cntdot.O2 charge-transfer state in zeolite NaY: red-light-induced photooxidation of 2,3-dimethyl-2-butene

Abstract

It is well-established that organic molecule-O[sub 2] pairs give rise to contact charge-transfer absorptions and photochemistry. Such spectroscopic and chemical observations have been made in oxygen-saturated organic solution, high-pressure O[sub 2] gas, and solid O[sub 2]. We wish to communicate an unprecedented stabilization of the excited charge-transfer state of 2,3-dimethyl-2-butene-O[sub 2] complexes by more than 10,000 cm[sup [minus]1] (300 nm) upon enclosure of the reactants in the cages of an inert polar matrix, namely zeolite NaY. In addition, chemistry that ensues from irradiation of the long wavelength absorption band is reported. This study shows that enclosure of alkene and O[sub 2] in the cages of inert zeolites allows us to tune the charge-transfer absorption to very long wavelengths. Such low-energy charge-transfer states of reactant pairs in inert solid matrices offer an opportunity to achieve product controlled photochemistry by furnishing optical access to very low-lying reaction surfaces, an aspect of photochemistry in zeolite matrices that is yet to be explored. 30 refs., 2 figs.