Acid/Base-mediated uptake and release of halide anions with a preorganized aryl-triazole foldamer.

A new approach for the construction of artificial receptors capable of selectively uptake and release of halides to mimic the biological halide ions pumps is developed, in which the preorganized aryl-triazole foldamer was designed to bear a resorcinolic group in the central strand as a switch regulator. By using 1,8-diazabicyclo[5.4.0]undec-7-ene/picric acid as the trigger, the foldamer can be switched between "w"-shape and helical conformation. Due to the large, half-open cavity as well as the additional electrostatic repulsion between oxyanions and guest halide, the foldamer in "w"-shape possesses a much weaker affinity for chloride, bromide, and iodide anions than those in the helical conformation in 6:94 (v/v) [D6 ]DMSO/CDCl3 . When the foldamer and chloride ions have the same initial concentrations of 1 mM, 70 % chloride ions in the solution could be reversibly bound or released upon switching.