(Thio)urea resorcinarene cavitands. Complexation and membrane transport of halide anions

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 H-1 NMR spectroscopy. The receptors have a small preference for chloride over the other halides; p-fluorophenylthiourea cavitand 8a gives the highest association constant (K-ass = 4.7 x 10(5) 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.