(Thio)urea Resorcinarene Cavitands. Complexation and Membrane Transport of Halide Anions

Abstract

Reaction of aminomethylcavitands with iso(thio)cyanates gives (thio)urea-functionalized resorcinarene cavitands, which represent a novel class of neutral anion receptors. The complexation of halide anions has been studied both with infrared and ¹H NMR spectroscopy. The receptors have a small <i>preference for chloride</i> over the other halides; <i>p</i>-fluorophenylthiourea cavitand 8a gives the highest association constant (K_ass = 4.7 × 10⁵ M^-1 with chloride in CDCl₃). A cooperative effect of the ligating (thio)urea moieties is indicated by the lower affinity of the corresponding tris(thio)urea-functionalized cavitands. For the first time facilitated membrane transport of halide anions through supported liquid membranes is achieved.