Issue 24, 2022

Tetraamidoindolyl calix[4]arene as a selective ion pair receptor for LiCl

Abstract

A calix[4]arene (1) functionalized with amidoindole groups on the upper rim and with propyl groups on the lower rim has been synthesized. It was revealed by 1H NMR spectroscopic analyses and single crystal X-ray diffraction analysis that compound 1 functions as an ion pair receptor capable of binding the lithium cation and the chloride anion concurrently in 10% DMSO-d6 in CDCl3. In the resulting complex, 1·LiCl, the lithium cation is coordinated to the amide carbonyl oxygen atoms of receptor 1 while the chloride anion is hydrogen-bonded to the indole NHs forming a contact ion pair with the co-bound lithium cation. With the lithium cation pre-complexed, the affinity of receptor 1 for Cl (Ka = 139 M−1) and Br (Ka = 31 M−1) was enhanced by 1.7-fold (Ka = 242 M−1) and 2.1-fold (Ka = 65 M−1), respectively, relative to its ion-free form. Likewise, the chloride complex of receptor 1 binds the lithium cation with 1.5-fold improved affinity (Ka = 353 M−1) relative to 1 alone. Receptor 1 was also found to extract and solubilize the otherwise insoluble salts LiCl and LiBr selectively into chloroform.

Graphical abstract: Tetraamidoindolyl calix[4]arene as a selective ion pair receptor for LiCl

Supplementary files

Article information

Article type
Research Article
Submitted
28 sep 2022
Accepted
25 okt 2022
First published
25 okt 2022

Org. Chem. Front., 2022,9, 6888-6893

Tetraamidoindolyl calix[4]arene as a selective ion pair receptor for LiCl

S. H. Kim, Y. Yeon, A. Lee, V. M. Lynch, Q. He, J. L. Sessler and S. K. Kim, Org. Chem. Front., 2022, 9, 6888 DOI: 10.1039/D2QO01519F

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