C3-Symmetric metacyclophane-based anion receptors with three thiourea groups as linkers between aromatic groups

Neutral anion receptors based on the C3-symmetric metacyclophane structure with three thiourea groups as linkers between aromatic groups have been prepared and examined for their anion-binding ability. The association constants of 1 and 2 with various anions were measured by the 1H NMR titration method. Compound 2, with three convergent thiourea groups pointing toward the binding cavity, showed increased binding affinities to anions and selective binding to AcO− compared to conformationally more flexible 1, which exhibited selective binding to H2PO4− in DMSO-d6.