Anion Recognition of 2,3-Disubstituted Cyclodextrin Derivatives in a Mixed Solvent of Acetnitrile and Water

Abstract

In this study, we investigated the use of cyclodextrins (CDs) as scaffolds for constructing anion receptors. We synthesized modified α- and β-CDs (1-3), in which the hydroxyls on C-2 and C-3 are protected by benzyl, acetyl, or propionyl groups; moreover, we investigated their anion binding properties in CD₃CN or CD₃CN/D₂O (99/1, v/v) using ¹H-NMR titration experiments. The results demonstrate that CD-based receptors (1-3) effectively bind with AcO^- and H₂PO₄^- by cooperative intermolecular hydrogen bondings with alcoholic hydroxyl groups on C-6. The selectivity trends thought to be a function of the basicity of the anions and the size of the binding pocket in the receptors.