AG-SPECIFIC PYRIDINE PODANDS - EFFECTS OF LIGAND GEOMETRY AND STEREOCHEMICALLY CONTROLLED SUBSTITUTION ON CATION COMPLEXATION AND TRANSPORTFUNCTIONS()

A new series of acyclic podands was designed so that three pyridine mo ieties cooperatively bind a guest Ag+. Liquid-Liquid extraction, NMR b inding, and computer calculation experiments reveal that podands with three pyridine donors in a proper geometry exhibit a perfect Ag+ speci ficity. They selectively extracted Ag+ in the presence of equimolar Pb 2+, CU2+, Ni2+, Co2+, and Zn2+. Introduction of two chiral centers clo se to the pyridine binding sites surprisingly influences the Ag+-bindi ng ability of the podand. Fourteen new pyridine podands were evaluated as carriers in a liquid membrane transport system. A combination of l igand geometry and stereocontrolled substitution provides excellent Ag +-specific transport.