Biotin[6]uril Esters: Chloride-Selective Transmembrane Anion Carriers Employing C-H•••Anion Interactions

Biotin[6]uril hexaesters represent a new class of anionophores which operate solely through C-H center dot center dot center dot 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 SO42-). Especially relevant is the selectivity between chloride and bicarbonate, the major inorganic anions in biological systems.