Synthesis of bifunctional receptor for fluoride and cadmium based on calix[4]arene with thiourea moieties

Abstract

A new calix[4]arene thiourea derivative bearing a benzothiazolyl moiety (L) was synthetized and characterized by single crystal X-ray, NMR and ESI-TOF. The binding ability of the bifunctional receptor towards several ions was investigated in acetonitrile by means of UV–Visible and NMR spectroscopy. The UV–Vis studies of receptor L demonstrated a stoichiometry of 1:1 for all ions studied. Also, recognize selectively F− and Cd2+ with a detection limit of 97 and 37 μM, respectively. Also, 1H NMR titration of receptor L indicated that both thiourea bridge and phenolic hydroxyl functional groups played a critical role in the binding of F− and Cd2+ ions. 1H NMR spectrum showed that receptor L has a flattened-cone conformation in solution that changes to a cone conformation in the presence of fluoride while cadmium maintained the initial conformation.