摘要:
A new series of acyclic podands was designed so that three pyridine moieties cooperatively bind a guest Ag(+). Liquid-Liquid extraction, NMR binding, and computer calculation experiments reveal that podands with three pyridine donors in a proper geometry exhibit a perfect Ag(+) specificity. They selectively extracted Ag+ in the presence of equimolar Pb(2+), CU(2+), Ni(2+), Co(2+), and Zn(2+). Introduction of two chiral centers close to the pyridine binding sites surprisingly influences the Ag(+)-binding ability of the podand. Fourteen new pyridine podands were evaluated as carriers in a liquid membrane transport system. A combination of ligand geometry and stereocontrolled substitution provides excellent Ag(+)-specific transport.