INCLUSION OF QUATERNARY AMMONIUM-COMPOUNDS BY CALIXARENES

In weakly polar solvents, strong association occurs between calixarene anions and tetraalkylammonium cations, with the magnitude of the obse rved equilibrium constants depending upon the charge on the anion, the solvent, the ring size of the calixarene and the nature of the alkyl group of the cation. Large upfield shifts of the methyl resonances of the [(CH3)(4)N](+) cation in solutions of [(CH3)(4)N](2) [p-t-butylcal ix[6]arene - 2H] indicate cation inclusion in a structure which is pos sibly identical with that found for the solid 'salt' by X-ray crystall ography. This shows one of the cations to be included within a partial cone structure of a 'hinged 3-up, 3-down' conformation of the calixar ene. The functionalised tetramethylammonium ions, choline and acetyl c holine, are also strongly included by various calixarene anions but at tempts to detect significant modification of the reactivity of acetyl choline resulting from inclusion have not been successful.