Study by electron paramagnetic resonance of charge transfer complexes formed by adsorption of TCNE on type X- and Y-zeolites

Abstract

Electron paramagnetic resonance (e.p.r.) was used to study charge-transfer complexes formed by adsorption of tetracyanoethylene (TCNE) on type X- and Y-zeolites.

The results obtained show that the paramagnetism appearing when TCNE is adsorbed on the zeolite is linked to the aluminium atoms and that two types of paramagnetic centres always appear simultaneously. However, the type constituted by the TCNE^– ion is more dependent on the nature of the cation and the presence of solvent. All these results can be interpreted by admitting the formation of a charge transfer complex with two paramagnetic electrons when TCNE is adsorbed on the surface of the zeolite. One of these electrons is bound to a TCNE^– ion and comes from an aluminium atom.

The second paramagnetic type is constituted by the second unpaired electron which necessarily appears at the same time as the first and is located in the structure of the zeolite, probably near the aluminium atom donor.