Calixcrowns and Related Molecules

Abstract

The synthesis of 1,2- and 1,3-calix[4]-bis-crowns, double calix[4]arenes and double calixcrowns have been shown to depend on the reaction conditions (nature of the base, structure of the ditosylates, and the stoichiometry of the reactants). The 1,3-alternate conformation of the 1,3-calix[4]-bis-crowns was shown to be favourable to the selective complexation of cesium cation. The observed Na+/Cs+ selectivity was exploited in separation processes using them as carriers in transport through supported liquid membranes (SLMs). The best Na+/Cs+ selectivity (1/45 000) was observed for the naphthyl derivative 7. Calix(aza)crowns and 1,3-calix[4]-bis-(aza)-crowns were also produced through the preliminary formation of the Schiff base-calixarenes, which were further hydrogenated. The syntheses consisted of the 1,3-selective alkylation of calixarenes followed by cyclization into a 1,3-bridged calixarene or by the direct 1,3-capping of the calixarene with appropriate ditosylates. Soft metal complexation by these ligands is also presented.