KF and CsF Recognition and Extraction by a Calix[4]crown-5 Strapped Calix[4]pyrrole Multitopic Receptor

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• 作者：Sung Kuk Kim ; Vincent M. Lynch ; Neil J. Young ; Benjamin P. Hay ; Chang-Hee Lee ; Jong Seung Kim ; Bruce A. Moyer ; Jonathan L. Sessler
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：December 26, 2012
• 年：2012
• 卷：134
• 期：51
• 页码：20837-20843
• 全文大小：460K
• 年卷期：v.134,no.51(December 26, 2012)
• ISSN：1520-5126

文摘

On the basis of ¹H NMR spectroscopic analyses and single crystal X-ray crystal structural data, the ion-pair receptor 1, bearing a calix[4]pyrrole for anion binding and calix[4]arene crown-5 for cation recognition, was found to act as a receptor for both CsF and KF ion-pairs. Both substrates are bound strongly but via different binding modes and with different complexation dynamics. Specifically, exposure to KF in 10% CD₃OD in CDCl₃ leads first to complexation of the K⁺ cation by the calix[4]arene crown-5 moiety. As the relative concentration of KF increases, then the calix[4]pyrrole subunit binds the F^{鈥?/sup> anion. Once bound, the K+ cation and the F鈥?/sup> anion give rise to a stable 1:1 ion-pair complex that generally precipitates from solution. In contrast to what is seen with KF, the CsF ion-pair interacts with receptor 1 in two different modes in 10% CD₃OD in CDCl₃. In the first of these, the Cs+ cation interacts with the calix[4]arene crown-5 ring weakly. In the second interaction mode, which is thermodynamically more stable, the Cs+ cation and the counteranion, F鈥?/sup>, are simultaneously bound to the receptor framework. Further proof that system 1 acts as a viable ion-pair receptor came from the finding that receptor 1 could extract KF from an aqueous phase into nitrobenzene, overcoming the high hydration energies of the K+ and F鈥?/sup> ions. It was more effective in this regard than a 1:1 mixture of the constituent cation and anion receptors (4 and 5).}