Controlling Cesium Cation Recognition via Cation Metathesis within an Ion Pair Receptor

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• 作者：Sung Kuk Kim ; Gabriela I. Vargas-Z煤帽iga ; Benjamin P. Hay ; Neil J. Young ; L忙titia H. Delmau ; Charles Masselin ; Chang-Hee Lee ; Jong Seung Kim ; Vincent M. Lynch ; Bruce A. Moyer ; Jonathan L. Sessler
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：January 25, 2012
• 年：2012
• 卷：134
• 期：3
• 页码：1782-1792
• 全文大小：658K
• 年卷期：v.134,no.3(January 25, 2012)
• ISSN：1520-5126

文摘

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鈥搑elease cycle that does not necessarily require displacement to effect release. The receptor forms stable complexes with the test cesium salts, CsCl and CsNO₃, in solution (10% methanol-d₄ in chloroform-d) as inferred from ¹H NMR spectroscopic analyses. The addition of KClO₄ to these cesium salt complexes leads to a novel type of cation metathesis in which the 鈥渆xchanged鈥?cations occupy different binding sites. Specifically, K⁺ becomes bound at the expense of the Cs⁺ cation initially present in the complex. Under liquid鈥搇iquid conditions, receptor 3 is able to extract CsNO₃ and CsCl from an aqueous D₂O layer into nitrobenzene-d₅ as inferred from ¹H NMR spectroscopic analyses and radiotracer measurements. The Cs⁺ cation of the CsNO₃ extracted into the nitrobenzene phase by receptor 3 may be released into the aqueous phase by contacting the loaded nitrobenzene phase with an aqueous KClO₄ 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.