A Bambusuril Receptor Binds Chaotropic Anions in Water at Picomolar Concentrations

Anionic pollutants are widespread in the environment and pose risks to human health. Due to the typically low concentrations of these species, the development of efficient receptors for their detection and removal from aqueous solutions is highly desirable. Here, we report the design and synthesis of a bambusuril receptor with markedly enhanced anion-binding affinity in water, achieved by introducing trifluoromethyl electron-withdrawing groups. The resulting fluorinated receptor is, to date, the most potent known receptor for several chaotropic anions in aqueous media. The most stable 1:1 host–guest complex in water was observed with iodide, exhibiting a relative dissociation constant of 63 pM. This complex is over three orders of magnitude more stable than any previously reported complex between an artificial receptor and inorganic anion in water.