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Phenanthroline-strapped calix[4]pyrroles: anion receptors displaying affinity reversal as a function of solvent polarity

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Abstract

Calix[4]pyrroles 1 and 2, diametrically strapped with a phenanthroline via ester and amide linkages, respectively, have been synthesized as anion receptors. It was revealed by 1H NMR spectroscopic analysis that receptors 1 and 2 possessing both hydrogen bonding donors and acceptors were able to bind the bicarbonate anion (as its tetraethylammonium (TEA+) or sodium salt) in CDCl3, as well as in 15% aqueous DMSO with high affinity and selectivity over other anions. The amide-based receptor 2 contains additional potential hydrogen bonding donors relative to its ester-based congener 1. Nevertheless, in CDCl3 receptor 1 was found to display a higher affinity for all test anions than receptor 2. In contrast, in 15% aqueous DMSO solution the affinities of receptor 2 for anions, in particular chloride, bicarbonate, and dihydrogen phosphate, were enhanced, whereas those of receptor 1 were reduced dramatically with no appreciable interaction being seen in the case of most test anions considered in this study. These reversals in selectivity and affinities underscore the importance of solvent in regulating the recognition features of seemingly similiar anion binding agents.

Graphical abstract: Phenanthroline-strapped calix[4]pyrroles: anion receptors displaying affinity reversal as a function of solvent polarity

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Article information


Submitted
16 Nov 2019
Accepted
31 Dec 2019
First published
02 Jan 2020

Org. Chem. Front., 2020, Advance Article
Article type
Research Article

Phenanthroline-strapped calix[4]pyrroles: anion receptors displaying affinity reversal as a function of solvent polarity

N. J. Heo, J. H. Oh, J. T. Lee, Q. He, J. L. Sessler and S. K. Kim, Org. Chem. Front., 2020, Advance Article , DOI: 10.1039/C9QO01377F

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