title: Ester-armed cyclens having quadruplicated helical geometry: remarkably stable and selective encapsulation of Na+ ion.
abstract: A new series of ester-armed cyclens nicely accommodated a Na+ ion in their quadruplicated helical binding spheres and effectively discriminated the cation from Li+ and K+ ions. Crystallographic studies revealed that four ester-functionalized sidearms provided effective coordination with the Na+ ion trapped in the 12-membered cyclen ring. Log K values for their Na+ complexes were estimated as 9-11 in CD3CN or C2D5OD, which were comparable to those of common bicyclic cryptands. FAB-MS, liquid-liquid extraction, and NMR binding experiments demonstrated that the cooperative action of the parent cyclen ring and ester-functionalized sidearms offered stable and selective encapsulation of the Na+ ion based on unique quadruplicated helical geometry.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Shinoda
authors.forename: T
authors.initials: T
authors.lastname: Nishimura
authors.forename: M
authors.initials: M
authors.lastname: Tadokoro
authors.forename: H
authors.initials: H
authors.lastname: Tsukube