Diphenylpyrrole‐Strapped Calix[4]pyrrole Extractant for the Fluoride and Chloride Anions

Abstract

AbstractThe anion binding features of diphenylpyrrole‐strapped calix[4]pyrrole 1 have been investigated by means of 1H NMR spectroscopy and ITC (isothermal titration calorimetry), as well as single crystal X‐ray diffraction analyses. Receptor 1 bearing an auxiliary pyrrolic NH donor and solubilizing phenyl groups on the strap was found to bind F−, Cl−, and Br− as their tetrabutylammonium salts with high affinity in DMSO‐d6. In addition, receptor 1 was found to extract the fluoride anion (as both its tetraethylammonium (TEA+) and tetrabutylammonium (TBA+) salts), as well as the chloride anion into chloroform‐d from an aqueous source phase. Cation metathesis using TBAI or the use of a dual host approach involving crown ethers enabled receptor 1 to extract simple alkali metal fluoride or chloride salts from water. Quantitative binding of NaF by receptor 1 was observed in 20 % D2O‐DMSO‐d6 allowing for the direct determination of the NaF concentration in an unknown sample.