K. Pitchumani

Asymmetrically modified zeolite as a medium for enantioselective photoreactions: Reactions from spin forbidden excited states

Moderate enantioslectivity has been achieved on two photochemical reactions that involve molecules reacting from spin forbidden excited states. Zeolite is found to be a unique medium in this context.

Photo-fries reaction of naphthyl esters within zeolites

Abstract Photolysis of naphthyl esters within zeolites leads to the photo-Fries rearrangements as in isotropic solution. However, a high level of product selectivity is obtained using ‘cation as the key’. A key component for predicting the selectivity of photoreactions within zeolites, namely the location of reactants, is missing at this stage.

Triplet–triplet energy transfer between organic molecules trapped in zeolites

Double loading of a zeolite with a triplet energy donor and a triplet energy acceptor followed by selective irradiation into the donor absorption band leads to characteristic triplet state reactivity of the acceptor.

CATION-GUEST INTERACTION WITHIN ZEOLITES : LI+ EXCHANGED ZEOLITES ARE UNIQUE

Lithium cations present in the supercages of zeolite X and Y activate guest molecules through electrostatic interaction with the π-cloud. Such an interaction may have consequences on the reactivity-photochemical and thermal-of the guest organic molecule.

Cation to anion triplet-triplet energy transfer in crystalline organic salts

Irradiation of crystalline salts formed between sensitizer-linked amines and photochemically reactive carboxylic acids at wavelengths where only the sensitizers absorb leads to characteristic triplet state reactivity of the carboxylate anions.

Cation radical and carbocation mediated reactions within Ca Y zeolite: 1-phenyl 3,4-dihydronaphthalene

Reactions of carbocations and radical cation of 1-phenyl 3,4-dihydronaphthalene have been investigated within Ca Y.

Zeolite as a reagent and as a catalyst: reduction and isomerizationof alkenes by Ca Y

Depending on the number of Bronsted acid sites present, Ca Y can act either as a reagent and reduce stilbenes to 1,2-diarylethanes or act as a catalyst and isomerize cis-stilbenes to the more stable trans form; Lewis acid sites generated by the activation process yield radical cations from stilbenes but these do not yield any stable products.

Novel approaches towards the generation of excited triplets of organic guest molecules with zeolites

Alkali metal cation-exchanged zeolites (M+X or M+Y) can be used as ‘microreactors’ in which to carry out photochemical rearrangement reactions of organic guests.

An exceptionally stable carbocation from indene generated and trapped within Ca Y zeolite

Inclusion of indene within activated Ca Y zeolite generates a persistent dimer carbocation; the chemistry that occurs within the supercages of Ca Y is controlled by the number of Bronsted acidic sites that are generated during the activation process.