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首页> 外文期刊>Chemistry: A European journal >Induction-driven stabilization of the anion-π interaction in electron-rich aromatics as the key to fluoride inclusion in imidazolium-cage receptors
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Induction-driven stabilization of the anion-π interaction in electron-rich aromatics as the key to fluoride inclusion in imidazolium-cage receptors

机译：富电子芳族化合物中阴离子-π相互作用的感应驱动稳定化是将咪唑笼式受体中的氟化物包含的关键

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摘要

Intermolecular interactions that involve aromatic rings are key processes in both chemical and biological recognition. It is common knowledge that the existence of anion-π interactions between anions and electron-deficient (π-acidic) aromatics indicates that electron-rich (π-basic) aromatics are expected to be repulsive to anions due to their electron-donating character. Here we report the first concrete theoretical and experimental evidence of the anion-π interaction between electron-rich alkylbenzene rings and a fluoride ion in CH3CN. The cyclophane cavity bridged with three naphthoimidazolium groups selectively complexes a fluoride ion by means of a combination of anion-π interactions and (C?￡?H) +?F--type ionic hydrogen bonds. 1H NMR, 19F NMR, and fluorescence spectra of 1 and 2 with fluoride ions are examined to show that only 2 can host a fluoride ion in the cavity between two alkylbenzene rings to form a sandwich complex. In addition, the cage compounds can serve as highly selective and ratiometric fluorescent sensors for a fluoride ion. With the addition of 1 equiv of F-, a strongly increased fluorescence emission centered at 385 nm appears at the expense of the fluorescence emission of 2 centered at 474 nm. Finally, isothermal titration calorimetry (ITC) experiments were performed to obtain the binding constants of the compounds 1 and 2 with F- as well as Gibbs free energy. The 2-F- complex is more stable than the 1-F- complex by 1.87 kcal mol-1, which is attributable to the stronger anion-π interaction between F- and triethylbenzene.
机译：涉及芳香环的分子间相互作用是化学和生物学识别中的关键过程。众所周知，阴离子与缺电子的（π-酸性）芳族化合物之间存在阴离子-π相互作用，这表明富含电子的（π-碱性）芳族化合物由于其供电子性而有望排斥阴离子。在这里，我们报告了第一个具体的理论和实验证据，证明了富电子的烷基苯环与CH3CN中的氟离子之间的阴离子-π相互作用。桥联有三个萘咪唑基的环空腔通过阴离子-π相互作用和（C→H→H）+→F-型离子氢键的组合选择性地使氟离子络合。通过1 H NMR，19 F NMR以及带有氟离子的1和2的荧光光谱进行了检查，结果表明只有2个可以在两个烷基苯环之间的空腔中形成一个氟离子，从而形成三明治复合物。此外，笼状化合物可以用作氟离子的高选择性和比例式荧光传感器。通过添加1当量的F-，出现了以385nm为中心的强烈增加的荧光发射，但以以474nm为中心的2的荧光发射为代价。最后，进行了等温滴定热分析（ITC）实验，以获得化合物1和2与F-以及吉布斯自由能的结合常数。 2-F-络合物比1-F-络合物稳定1.87 kcal mol-1，这归因于F-与三乙苯之间更强的阴离子-π相互作用。

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