Comparative Study of Charge-Assisted Hydrogen- and Halogen-Bonding Capabilities in Solution of Two-Armed Imidazolium Receptors toward Oxoanions

Sabater, Paula; Zapata, Fabiola; Caballero, Antonio; Visitación, Néstor de la; Alkorta, Ibón; Elguero, José; Molina, Pedro

doi:10.1021/acs.joc.6b01146

Cited by 33 publications

(16 citation statements)

References 51 publications

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“…Nor has there been much consideration of halogen donors that bear a full positive charge. The imidazolium species represents a strong candidate for study of these matters, especially given its prominence [ 41 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 ] within the context of anion receptors and catalysis as well as in ionic liquids. How strong a halogen bond can arise when the H of the positively charged imidazolium is replaced by a halogen atom?…”

Section: Introductionmentioning

confidence: 99%

Halogen Bonds Formed between Substituted Imidazoliums and N Bases of Varying N-Hybridization

Scheiner

2017

Molecules

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Heterodimers are constructed containing imidazolium and its halogen-substituted derivatives as Lewis acid. N in its sp3, sp2 and sp hybridizations is taken as the electron-donating base. The halogen bond is strengthened in the Cl < Br < I order, with the H-bond generally similar in magnitude to the Br-bond. Methyl substitution on the N electron donor enhances the binding energy. Very little perturbation arises if the imidazolium is attached to a phenyl ring. The energetics are not sensitive to the hybridization of the N atom. More regular patterns appear in the individual phenomena. Charge transfer diminishes uniformly on going from amine to imine to nitrile, a pattern that is echoed by the elongation of the C-Z (Z=H, Cl, Br, I) bond in the Lewis acid. These trends are also evident in the Atoms in Molecules topography of the electron density. Molecular electrostatic potentials are not entirely consistent with energetics. Although I of the Lewis acid engages in a stronger bond than does H, it is the potential of the latter which is much more positive. The minimum on the potential of the base is most negative for the nitrile even though acetonitrile does not form the strongest bonds. Placing the systems in dichloromethane solvent reduces the binding energies but leaves intact most of the trends observed in vacuo; the same can be said of ∆G in solution.

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Section: Introductionmentioning

confidence: 99%

Halogen Bonds Formed between Substituted Imidazoliums and N Bases of Varying N-Hybridization

Scheiner

2017

Molecules

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“… Structure of the halogen and hydrogen bonding receptors 7 2+ ·2PF 6 − and 8 2+ ·2PF 6 − reported in [ 24 ] and the structure of the mixed halogen and hydrogen bonding receptor 5 2+ ·2PF 6 − proposed in this work. …”

Section: Figures Schemes and Tablesmentioning

confidence: 58%

“…Recently, we have reported the synthesis and the anion sensing properties of two-armed charge-assisted ditopic imidazolium and haloimidazolium bidentade receptors which recognize anions by hydrogen or halogen bonding interaction, respectively [ 24 ]. Taking into account the important differences found in the sensing behavior between these two receptors, we decided to perform the synthesis and study of a new charge-assisted bidentade receptor containing both halogen and hydrogen bonding sites by incorporation in its structure of one haloimidazolium, halogen bonding binding site, and one imidazolium, hydrogen bonding binding site, which could act through the cooperative and simultaneous action of halogen bonds and hydrogen bonds during the anion recognition event.…”

Section: Introductionmentioning

confidence: 99%

Modulation of the Selectivity in Anions Recognition Processes by Combining Hydrogen- and Halogen-Bonding Interactions

et al. 2017

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Most of the halogen bonding receptors for anions described use halogen bonding binding sites solely in the anion recognition process; only a few examples report the study of anion receptors in which the halogen bonding interaction has been used in combination with any other non-covalent interaction. With the aims to extend the knowledge in the behaviour of this kind of mixed receptors, we report here the synthesis and the anion recognition and sensing properties of a new halogen- and hydrogen- bonding receptor which binds anions by the cooperation of both non-covalent interactions. Fluorescence studies showed that the behaviour observed in the anion recognition sensing is similar to the one previously described for the halogen analogue and is quite different to the hydrogen one. On the other hand, the association constants obtained by 1H-NMR data demonstrate that the mixed halogen- and hydrogen-bonding receptor is more selective for SO42− anion than the halogen or hydrogen analogues.

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“…Different type of positively charged sites can be grafted onto the calixarene . Imidazolium groups, bound to different positions have been recently used . The imidazolium proton's high acidity can promote efficient and strong C‐H .… anion interactions and, in addition, the cationic imidazolium groups, may also induce strong electrostatic interactions with negatively charged anions.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Positively Charged tris‐Imidazolium Calix[6]arene Hosts for Anion Recognition

et al. 2019

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The syntheses of new tripodal ligands with effective C 3 symmetry and anion recognition properties, are reported herein. The ligands have a 1,3,5-tris-methoxy-2,4,6-tris-(α,ωbromoalkoxy)calix- [6]arene as a backbone, and were prepared from 1,3,5-tris-methoxy-p-tert-butyl-calix [6]arene by alkylation with a series of α,ω-dibromo-alkanes [Br(CH 2 ) n Br] of different chain lengths (n = 2, 4 or 6). Further substitution of the bromo groups, via the use of 1-methyl-, 1-mesityl-or 2,6-diisopropylphenyl-1H-imidazole, led to alkylation by imidazole units and afforded tripodal and tricationic 1,3,5-tris-methoxy-2,4,6-trisimidazolium-p-tert-butyl-calix[6]arenes. These scaffolds provide a framework for H-bonded and electrostatic interactions with various anions and their anion binding properties were investigated by 1 H NMR and UV-visible spectroscopy. A sizeable selectivity for HSO 4 -(present as the n-Bu 4 N + salt) was demonstrated for most of the tripodal ligands considered in this work. Other anions such BF 4 -, ClO 4 -, PF 6 -, NO 3 -, Clexhibited weak to medium associations with the investigated ligands. A single crystal X-ray study, unfortunately of poor quality, corroborated the geometry of the calix [6]arenes that was previously established by 1 H NMR spectroscopy. The bindingsite geometry was more definitively probed by DFT calculations. IntroductionOver the last decades, the design of molecular receptors with high selectivity has been one of the goals and challenges in the field of supramolecular chemistry: [1] different functionalities and shapes [2][3][4] have been investigated to induce selective and efficient [5][6][7][8] recognition of charged and/or neutral species. [9] Due to their potential applications in the biological, environmental and industrial domains, [10][11][12][13][14] interest has also been focused on pre-organized hosts for anion coordination. [15,16] Nevertheless the selective coordination of anions remains a research area which has been less explored compared to that of cations. [17][18][19][20] The designed receptors can be neutral or cationic organic scaffolds or even metal-ligand complexes. [21][22][23][24][25] Calix[4]arenes have attracted interest due to their concave macrocyclic structure and hydrophobic cavity, despite their small cavity size, which can hamper the design of systems for anion recognition. Following subtle substitution and preorganization on the upper and lower rims, [26][27][28][29][30] charged systems have been prepared and investigated. Different type of positively charged sites can be grafted onto the calixarene. [31] Imidazolium groups, bound to different positions have been recently used. [32][33][34] The imidazolium proton's high acidity can promote efficient and strong C-H .… anion interactions and, in addition, the cationic imidazolium groups, may also induce strong electrostatic interactions with negatively charged anions. Secondary effects, such as anion-π interactions [35,36] could also take place. Overall, this series of complementary interactions makes c...

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Comparative Study of Charge-Assisted Hydrogen- and Halogen-Bonding Capabilities in Solution of Two-Armed Imidazolium Receptors toward Oxoanions

Cited by 33 publications

References 51 publications

Halogen Bonds Formed between Substituted Imidazoliums and N Bases of Varying N-Hybridization

Halogen Bonds Formed between Substituted Imidazoliums and N Bases of Varying N-Hybridization

Modulation of the Selectivity in Anions Recognition Processes by Combining Hydrogen- and Halogen-Bonding Interactions

Synthesis and Characterization of Positively Charged tris‐Imidazolium Calix[6]arene Hosts for Anion Recognition

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