Macrocycles for the complexation of radiocesium: a concise review of crystallographic and computational studies

We review the crystallographic studies concerned with the complexes between cesium and different types of macrocycles. A detailed examination of the molecular structures indicates that the formation of several cesium–oxygen bonds is necessary in order for the macrocyle to capture a single Cs⁺ ion. In some cases, additional interactions such as cesium–arene and cesium–fluorine interactions may operate either alone or in combination with the above chemical bonds. Computational quantum chemistry studies based on experimental crystal structures represent a useful aid for elucidating the mechanism of binding and the role that explicit water molecules have in establishing ion–dipole interactions or H-bonds with the Cs⁺-macrocycle complex.