Shape-Persistent Oxa- and Aza-calix[4]arene Hybrid Molecular Cage and Naked Eye Sensing of Fluoride

An oxa- and aza-calix[4]arene hybrid molecular cage with a large, shape-persistent cavity wrapped by aromatic rings was designed and synthesized via multifold efficient S_NAr reactions. X-ray single-crystal analysis revealed that two THF molecules were encapsulated in the central cavity. Selective sensing of F^- in apolar solvent leads to naked eye discriminable color change. Addition of CH₃OH would recover the color of the molecular cage.