Key points are not available for this paper at this time.
A particularly challenging task is the design of anion receptors, because anions are larger than cations and are pH- and solvent-sensitive. The first host for anionic guests is a dendritic octadentate N ligand, which upon reaction with CuCl2, encapsulates chloride ions (Cl6, see picture) as guests by means of anion–π interactions in an electron-deficient cavity formed by four pyridine rings.
Hoog et al. (2004) studied this question.