Biotin[6]uril hexaesters represent a new class of anionophores which operate solely through C—H···anion interactions. The use of soft H-bond donors favors the transport of less hydrophilic anions (e.g., Cl^–, NO₃^–) over hard, stongly hydrated anions (e.g., HCO₃^– and SO₄^2–). Especially relevant is the selectivity between chloride and bicarbonate, the major inorganic anions in biological systems.

The discovery of receptors using templated synthesis enables the selection of strong receptors from complex mixtures.