Tritopic Bis-Urea Receptors for Anion and Ion-Pair Recognition

Abstract

This work reports on the synthesis and characterization of three tritopic receptors and their binding properties toward various anions, as their tetrabutylammonium salts, and three alkali metal–acetate salts by UV–vis, fluorescence, 1 H, 7 Li, 23 Na, and 39 K NMR in MeCN/dimethyl sulfoxide (DMSO) 9:1 (v/v). Molecular recognition studies showed that the receptors have good affinity for oxyanions. Furthermore, these compounds are capable of ion-pair recognition of the alkali metal–acetate salts studied through a cooperative mechanism. Additionally, molecular modeling at the density functional theory (DFT) level of some lithium and sodium acetate complexes illustrates the ion-pair binding capacity of receptors. The anion is recognized through strong hydrogen bonds of the NH– groups from the two urea sites, while the cation interacts with the oxygen atoms of the polyether spacer. This work demonstrates that these compounds are good receptors for anions and ion pairs.

Synergistic regulation of chloride anion recognition using a triple‐functional sites receptor with two different cationic effectors

“…The Δ E b cp for Cl − in EUPR @Na‐Cl‐Ag and EUPR @Na‐Ag‐Cl are also larger than −151 kcal/mol. It is clear that the enhancement effect of two cation (Na + and Ag + ) is strong than one cation (Na + or Ag + ) introduced into, presenting the features of ion‐pair recognition 45–50 . Especially, the Δ E b cp for Cl − in EUPR @NaAgCl is the largest, manifesting an excellent synergistic regulation performance for chloride anion recognition with two different cationic effectors.…”

“…It is clear that the enhancement effect of two cation (Na + and Ag + ) is strong than one cation (Na + or Ag + ) introduced into, presenting the features of ion-pair recognition. [45][46][47][48][49][50] Especially, the ΔE b cp for Cl À in EUPR@NaAgCl is the largest, manifesting an excellent synergistic regulation performance for chloride anion recognition with two different cationic effectors. Na + binding, in turn, can be enhanced by chloride anion, whereas it seems that Ag + binding cannot always be enhanced by chloride anion.…”

Solid polymer nanocomposite electrolytes based on poly(ε‐caprolactone)‐based waterborne polyurethane–polyethylene oxide and fluorine‐doped carbon quantum dot‐MXene

“…There are limited reports in the literature on the strong affinity of anions to the NH groups of the urea and urethane functionality 53 . Regarding the mechanism of this phenomenon, it was suggested that in short distances, weaker forces like hydrogen bonding could overcome the strong ionic interactions leading to aggregation of anions stabilized by its environment 54,55 . It is evident that the urea‐urethane functionalities were quite successful at immobilizing the anions while the oxygen atoms in PEO and PCL were responsible for coordination with $$$ {\mathrm{Li}}^{+} $$$.…”

“…53 Regarding the mechanism of this phenomenon, it was suggested that in short distances, weaker forces like hydrogen bonding could overcome the strong ionic interactions leading to aggregation of anions stabilized by its environment. 54,55 It is evident that the urea-urethane functionalities were quite successful at immobilizing the anions while the oxygen atoms in PEO and PCL were responsible for coordination with Li þ . In a recent report, it was shown that ionomers of WPU were able to limit the mobility of counter anions and the high t Liþ was attributed to the ionomers present in the WPU structure.…”

Highly soluble bisurea derivatives for anion recognition

“…24 Gomez-Vega, Lara, and co-workers have also reported bisurea linked through a polyether bridge for ion-pair recognition. 25 In addition, flexible butyl, sterically bulky tert -butyl, and aromatic phenyl groups have been introduced as terminal groups to compare the solubilities and the binding abilities of the receptors.…”