title: Controlling cesium cation recognition via cation metathesis within an ion pair receptor.
abstract: Ion pair receptor 3 bearing an anion binding site and multiple cation binding sites has been synthesized and shown to function in a novel binding-release cycle that does not necessarily require displacement to effect release. The receptor forms stable complexes with the test cesium salts, CsCl and CsNO(3), in solution (10% methanol-d(4) in chloroform-d) as inferred from (1)H NMR spectroscopic analyses. The addition of KClO(4) to these cesium salt complexes leads to a novel type of cation metathesis in which the "exchanged" cations occupy different binding sites. Specifically, K(+) becomes bound at the expense of the Cs(+) cation initially present in the complex. Under liquid-liquid conditions, receptor 3 is able to extract CsNO(3) and CsCl from an aqueous D(2)O layer into nitrobenzene-d(5) as inferred from (1)H NMR spectroscopic analyses and radiotracer measurements. The Cs(+) cation of the CsNO(3) extracted into the nitrobenzene phase by receptor 3 may be released into the aqueous phase by contacting the loaded nitrobenzene phase with an aqueous KClO(4) solution. Additional exposure of the nitrobenzene layer to chloroform and water gives 3 in its uncomplexed, ion-free form. This allows receptor 3 to be recovered for subsequent use. Support for the underlying complexation chemistry came from single-crystal X-ray diffraction analyses and gas-phase energy-minimization studies.
authors.affiliation: Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station, A5300, Austin, Texas 78712-0165, USA.
authors.forename: Sung Kuk
authors.initials: SK
authors.lastname: Kim
authors.forename: Gabriela I
authors.initials: GI
authors.lastname: Vargas-Zúñiga
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Hay
authors.forename: Neil J
authors.initials: NJ
authors.lastname: Young
authors.forename: Lætitia H
authors.initials: LH
authors.lastname: Delmau
authors.forename: Charles
authors.initials: C
authors.lastname: Masselin
authors.forename: Chang-Hee
authors.initials: CH
authors.lastname: Lee
authors.forename: Jong Seung
authors.initials: JS
authors.lastname: Kim
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Lynch
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Moyer
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Sessler