Anion Recognition Using Preorganized Thiourea Functionalized [3]Polynorbornane Receptors

A new family of [3]polynorbornane frameworks exhibiting conformationally preorganized aromatic thiourea (cleft-like) receptors have been designed and synthesized for anion recognition. These show excellent affinity for the biologically relevant dihydrogenphosphate (H₂PO₄^-) and dihydrogenpyrophosphate (H₂P₂O₇^2-) anions (among others), which are bound in 1:1 and 2:1 (host:anion) ratio, respectively. Moreover, visually striking color changes accompany guest binding, enabling this family to act as colorimetric anion sensors.