A new experimental protocol for intrazeolite photooxidations. The first product-based estimate of an upper limit for the intrazeolite singlet oxygen lifetime.

The intrazeolite photooxidations of several alkenes have been examined in hexane and in perfluorohexane slurries. The ability of perfluorohexane to increase the affinity of alkenes for the interior of the zeolite was documented. The nearly identical reaction rates in the two slurry solvents are attributed to a leveling of the singlet oxygen lifetime by the zeolite framework. A consideration of the rates of the various intrazeolite processes was used to estimate an upper limit for the intrazeolite lifetime of singlet oxygen.

Advances in singlet oxygen chemistry

The authors discuss the advances made in both mechanistic and synthetic aspects of singlet oxygen chem.  Formation and reactions of singlet oxygen in heterogeneous media (such as zeolites, micelles, vesicles, etc.) are discussed.  Cycloaddns. of mol. oxygen to olefins, heteroatom oxidns. via reaction of singlet oxygen with the electron pair at heteroatoms, and photooxygenations of heterocyclic systems by singlet oxygen are also reviewed.

Photooxidations of Alkenes in Fluorinated Constrained Media:  Fluoro-organically Modified NaY as Improved Reactors for Singlet Oxygen “Ene” Reactions

Creating a stationary fluorinated environment inside the zeolite cavity can increase the reactivity observed for intrazeolite photooxidation of alkenes. Exchanging the zeolite with fluorinated organic cations is a much more effective strategy than simply using a fluorinated solvent for slurry irradiations. Use of cations containing C-F bonds is also more efficient than use of deuterated cations for creation of a singlet oxygen friendly environment where the quenching processes are slowed down. Doping the zeolite with fluoro-organic cation 4 resulted in an increase in the singlet oxygen lifetime to 12 micros.

A Novel Zeolite-Induced Population of a Planar Viologen Conformation. New Viologen Charge Transfer Complexes and Alkene/Viologen/Zeolite Arrays

A rare example of a novel zeolite-induced conformational change and a mechanism for this process are suggested in order to rationalize an unexpected spontaneous intrazeolite reduction observed during preparation of a new viologen (MQ2+)-doped zeolite (NaY). In addition, the formations of six new alkene/viologen/ zeolite charge transfer (CT) arrays using NaMQY and the previously reported NaMVY are also reported. The binding constants between MQ2+ and MV2+ and 2,3-dimethyl-2-butene (TME) were determined using the Benesi-Hildebrand approach, and the stabilities of these CT complexes are compared to their intrazeolite analogue.

Viologen-Alkene CT Complex: A Comparison Between Solution and Intrazeolite Behavior‡‡Financial support through the NSF and the Italian CNR is fully acknowledged.