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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

Title
Induction-driven stabilization of the anion-π interaction in electron-rich aromatics as the key to fluoride inclusion in imidazolium-cage receptors
Authors
Xu Z.Singh N.J.Kim S.K.Spring D.R.Kim K.S.Yoon J.
Ewha Authors
윤주영
SCOPUS Author ID
윤주영scopus
Issue Date
2011
Journal Title
Chemistry - A European Journal
ISSN
0947-6539JCR Link
Citation
vol. 17, no. 4, pp. 1163 - 1170
Indexed
SCI; SCIE; SCOPUS WOS scopus
Abstract
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 CH 3CN. 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. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
DOI
10.1002/chem.201002105
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자연과학대학 > 화학·나노과학전공 > Journal papers
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