Wavelength Dependent Oxygen Mediated Electron- Transfer Reactions within M⁺Y Zeolites:  Photo Oxidation and Reduction of 1,1-Diarylethylenes

Abstract

Radical cations of 1,1-diarylethylenes have been generated by direct excitation of the parent olefins within zeolites. The radical cation generated by short wavelength irradiation of the olefin reacts with the solvent hexane while the one generated by long wavelength excitation of the diarylethylene/oxygen complex reacts with the counteranion radical (superoxide anion). While in solution the preferred reaction of the 1,1-diarylethylene radical cation is in addition to another ground-state olefin, no products derived from such a reaction were detected within zeolites. Within zeolites, the 1,1-diarylethylene radical cations undergo abstraction of a hydrogen atom and reaction with superoxide anion, the least-favored reactions in solution. The results show that reactive organic radical cations can be generated within zeolites by lamp irradiation in the absence of a sensitizer.

Influence of Oxygen on the UV−Photocatalyzed Generation of Pyrene Cation Radicals in the Zeolites X and Y

“…Since the early 1980s, photochemists have explored the use of zeolites as a reaction medium and literature reviews are available on the subject. − These studies have shown how zeolites can be strategically used to gain a photophysical or photochemical advantage, and have provided a detailed description of molecular behavior that has assisted the development of new and existing applications of zeolites in general. Current research on photochemistry in zeolites that continues to draw upon the earlier findings includes such topics as wireless solar energy conversion or photocatalysis − and fine chemical synthesis that relies on selective oxidation − and chiral induction…”

Photophysics and photochemistry of the β-lapachone derived diphenyldihydrodioxin: generation and characterization of its cation radical

“…Its formation, under oxygenated conditions, possibly involves a dioxetane intermediate, resulting from the interaction between molecular oxygen and the 2,3-diphenyl-1,4-dioxene radical cation formed from the decay of 4 (Scheme 3), as previously proposed in the literature. 24 From these results we can conclude that the preferential decay mode for 4 involves the formation of the 2,3-diphenyl-1,4-dioxene radical cation.…”

Urea Photosynthesis inside Polyelectrolyte Capsules: Effect of Confined Media

“…Ramamurthy et al explored zeolites as a media for achieving chiral induction of optically active organic molecules during photochemical reactions. Zeolite confined space forces a reactant and the chiral inductor to interact intimately to yield enantiomerically enriched product as high as 90%. − Porous TiO 2 is also an effective photocatalyst for water decomposition, phenol, chlorophenol, , and n -pentane , oxidation, as a component of a photovoltaic cell . Photoinduced CO 2 reduction was demonstrated using TiO 2 nanocrystals embedded in a SiO 2 matrix .…”