EFFICIENT AND SELECTIVE UP-HILL TRANSPORT OF ANIONS BY PH-INDUCED AFFINITY SWITCHING OF A COPPER COMPLEX CARRIER

The copper(II) complex of 6,6'-bis(4-hexylbenzoylamino)-2,2'-bipyridin e served as a new type of functional carrier in efficient and selectiv e up-hill transport of anions across an organic liquid membrane. Rever sible deprotonation of the amide groups of the ligand regulated the up take and release of anions by alteration of the anion affinity of the complex, and affinity switching of the carrier by the pH of external a queous solutions induced efficient up-hill transport of SCN- and tolue ne-p-sulfonate by coupling with a small pH difference across the membr ane. The high thiocyanate selectivity of the carrier was ascribed to p referential axial coordination of SCN- to the complex which possesses an N2O2 square-planar structure.