Abstract

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.