Side arm effects on cyclen-alkali metal cation complexation: Highly selective and three-dimensional encapsulation of Na+ ion

A variety of armed cyclens were prepared in which ester, amide, nitrile, an d pyridine moieties were attached as cation-ligating side arms to a 12-memb ered ring. Ester-, amide-, and pyridine-armed cyclens nicely accommodated a Na+ ion in a three-dimensional fashion and clearly discriminated the catio n from Li+ and K+ ions. They extracted Na+ ion more efficiently and selecti vely than common Na+ ion-selective ligands. X-ray diffraction, FAB-MS, Na-2 3 NMR binding studies, and computer modeling experiments demonstrated that the cyclens having ester-, amide-. and pyridine-functionalized side arms fo rmed highly selective encapsulated Na+ complexes via a cooperative action o f parent cyclen and side arms.