Selective Inclusion of Fluoride within the Cavity of a Two-Wall Bis-calix[4]pyrrole

Abstract

We report what to our knowledge is the smallest bis-calix[4]pyrrole (2). It proved capable of trapping fluoride anions exclusively relative to other anions (Cl^-, Br^-, SCN^-, NO₃^-, H₂PO₄^-, HSO₄^-, SO₄^2-, and HP₂O₇^3-; tetrabutylammonium salts), as confirmed by ¹H NMR spectroscopy (CDCl₃), X-ray diffraction analysis, DFT calculations, and molecular dynamics simulations. The F^- selectivity is ascribed to the small size of the cavity in 2.