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Side Arm Effects on Cyclen-Alkali Metal Cation Complexation: Highly Selective and Three-Dimensional Encapsulation of
Hiroshi Tsukube1, Yoshihisa Mizutani, Satoshi Shinoda
1Department of Chemistry, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan, and Department of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Yamaguchi University, Ube 755-0031, Japan.
Abstract:
A variety of armed cyclens were prepared in which ester, amide, nitrile, and pyridine moieties were attached as cation-ligating side arms to a 12-membered ring. Ester-, amide-, and pyridine-armed cyclens nicely accommodated a Na(+) ion in a three-dimensional fashion and clearly discriminated the cation from Li(+) and K(+) ions. They extracted Na(+) ion more efficiently and selectively than common Na(+) ion-selective ligands. X-ray diffraction, FAB-MS, (23)Na NMR binding studies, and computer modeling experiments demonstrated that the cyclens having ester-, amide-, and pyridine-functionalized side arms formed highly selective encapsulated Na(+) complexes via a cooperative action of parent cyclen and side arms.