Neutral anion receptors: design and application

After the development of synthetic cation receptors in the late 1960s, only in the past decade has work started on the development of synthetic neutral anion receptors. Combination and preorganization of different anion binding groups, like amides, urea moieties, or Lewis acidic metal centers lead to receptor molecules that strongly bind inorganic anions with high selectivity. Combined with neutral cation ligands, ditopic receptors were obtained for the complexation of inorganic salts. The molecular complexation properties of anion receptors has been transduced into macroscopic properties in membrane separation processes and in sensors for selective anion detection.