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

Abstract The anion binding features of diphenylpyrrole‐strapped calix[4]pyrrole 1 have been investigated by means of 1 H 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‐ d 6 . 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 % D 2 O‐DMSO ‐d 6 allowing for the direct determination of the NaF concentration in an unknown sample.