A Highly Efficient Neutral Anion Receptor in Polar Environments by Synergy of Anion−π Interactions and Hydrogen Bonding

Abstract

Herein, it is shown how anion recognition in highly polar solvents by neutral metal-free receptors is feasible when multiple hydrogen bonding and anion−π interactions are suitably combined. A neutral aromatic molecular tweezer functionalized with azo groups is shown to merge these two kinds of interactions in a unique system and its efficiency as an anion catcher in water is evaluated using first-principles quantum methods. Theoretical calculations unequivocally prove the high thermodynamic stability in water of a model anion, bromide, captured within the tweezer’s cavity. Thus, static calculations indicate anion–tweezer interaction energies within the range of covalent or ionic bonds and stability constants in water of more than 10 orders of magnitude. First-principles molecular dynamics calculations also corroborate the stability through the time of the anion–tweezer complex in water. It shows that the anion is always found within the tweezer’s cavity due to the combination of the tweezer–anion interactions plus a hydrogen bond between the anion and a water molecule that is inside the tweezer’s cavity.

Research Progress on Anion-π Interactions

“…2021 年, Orenha 课题组 [88] 利用阴离子-π 相互作用和 氢键的协同作用设计了对 Cl -、 Br -和硝酸根阴离子具有 识别作用的新型受体. 同年, Hermida-Ramon 课题组 [89] 设计合成了一种可与阴离子-π 和氢键相互作用而结合 的中性分子.…”

Recent Advancements in Ion‐Pair Receptors

“…Interestingly, to date these artificial ionpair receptors have not only been used in selective and sensitive sensing/recognization activities, but also employed in catalysis, ion transport through membrane or channels, and extraction or separation of salts in addition to their involvement in the construction of supramolecular polymers, self-assemblies, and dendrimers etc. [11][12][13][14][15][16] Supramolecular synthetic receptors had been used as the "molecular containers". They are having the capability for holding liquids, gasses, and solids in addition to their transportation.…”

“…offering ditopic or polytopic receptors. Interestingly, to date these artificial ion‐pair receptors have not only been used in selective and sensitive sensing/recognization activities, but also employed in catalysis, ion transport through membrane or channels, and extraction or separation of salts in addition to their involvement in the construction of supramolecular polymers, self‐assemblies, and dendrimers etc [11–16] …”