Bis(crown ether) and azobenzocrown derivatives of calix[4]arene. A review of structural information from crystallographic and modelling studies

The association within one molecule of calix[4]arene and crown ether moieti es leads to ligands with new complexing properties. In particular, calix[4] arene bis(crown-6) and some of its derivatives have been shown to be highly selective extractants for caesium ions. This review presents the backgroun d of the study and the results of crystal structure determinations and mole cular modelling calculations performed during the investigation of two mole cular families, the bis(crown ether) and the azobenzocrown derivatives of c alix[4]arene.