Supramolecular umpolung: Converting electron-rich resorcin[4]arenes into potent CH-bonding anion receptors and transporters
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0000-0002-7071-7125 Date
2024
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Elsevier
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Abstract
Because of the technological and biological relevance of anions, their receptors and transporters are of great interest in various fields. This study introduces a paradigm shift in design, presenting the traditionally cation-focused resorcin[4]arenes as versatile anion receptors and efficient chloride transporters with remarkable performance in water-rich environments. The design is based on the generation of a large dipole moment, which concentrates the electrostatic potential in a buried binding site, and a seemingly trivial substitution with alkyl chains, which endows the receptors with anion transport capability.
Description
CH hydrogen bonding receptors constitute an emerging class of anion sensors and transporters, which, owing to their high proteolytic and pH resistance, are promising for biological applications. CH groups, however, are considered as weak hydrogen bond donors, requiring activation by strongly electron-withdrawing substituents. Accordingly, electron-rich aromatic rings have never been used for this purpose thus far. In this work, we demonstrate that resorcin[4]arenes, well known as p-electron-rich cation receptors,
can be converted into CH-bonding anion receptors by simple substitution with four nitro groups. Owing to their unique geometric features, tetranitroresorcin[4]arenes acquire large dipole moments (up to 15.8 D) and highly positive electrostatic potentials at the lower rim, leading to remarkable anion affinities (Ka(Cl-) = 1.36 3 105 M-1 in THF). Moreover, we show also that the seemingly innocent alkyl chains surrounding the anion binding site enable high anion transport activities (EC50 down to 0.012 mol%) and resistance to competitive aqueous/organic media.
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Chem 10, 1910–1924, June 13, 2024 ; https://doi.org/10.1016/j.chempr.2024.03.003