The role of hydrogen atoms in interactions involving imidazolium-based ionic liquids

Kempter, V.; Kirchner, Barbara

doi:10.1016/j.molstruc.2010.02.003

Cited by 151 publications

(151 citation statements)

References 90 publications

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“…In summary, the IR and Raman spectra of the C(2) protonated ILs show that the anion interacts with the cation via formation of a strong hydrogen bond at C(2)-H. Upon methylation, the anion moves to the C(4) and C(5) moiety, where it forms a new hydrogen bond with one of the two protons. The spectra do not suggest that other interaction mechanisms, such as those via the π-electron system of the aromatic ring (often referred to as the on-top position [37][38][39]), play a major role. Moreover, Endo et al [26] performed an experimental and computational study on methylated and nonmethylated butylimidazolium ILs with spherical anions.…”

Section: Vibrational Spectramentioning

confidence: 80%

Effects of C(2) Methylation on Thermal Behavior and Interionic Interactions in Imidazolium-Based Ionic Liquids with Highly Symmetric Anions

et al. 2018

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Featured Application: The study aims at making a step towards the rational design of ionic liquids for specific applications. The key to this rational design is to fully understand the structure-property relationships. In other words, knowing the links between the behavior at the molecular and the macroscopic scale will enable to develop materials/fluids with optimal properties for a given application, e.g., a chemical process or an electrochemical device. Abstract:The chemical and physical properties of imidazolium-based ionic liquids are determined by the interactions between the counter-ions. The C(2) position plays an important role in these interactions, as it represents the predominant site for interionic hydrogen bonding. This study shows that the directional hydrogen bonds between highly symmetrical anions (iodide, tetrafluoroborate, hexafluorophosphate) and the C(2)-H group of the 1-methyl-3-propylimidazolium cation determine the molecular and macroscopic behavior in terms of the thermal properties. Upon replacing the C(2) proton by a methyl group, the anion repositions itself at the C(4)/(5) moiety, where it forms a new hydrogen bond, apparently with only one of the two CH groups. In addition, the larger the anion is in diameter, the more likely it will establish further interactions with other parts of the cation, such as the propyl chain.

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Section: Vibrational Spectramentioning

confidence: 80%

Effects of C(2) Methylation on Thermal Behavior and Interionic Interactions in Imidazolium-Based Ionic Liquids with Highly Symmetric Anions

et al. 2018

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“…Further in addition to the C2-H hydrogen bonding, C4-H and C5-H also participate in Hbonding interaction with halide anion but stabilization due to H-bonding interaction between cation and anion is found to be more in case of interaction involving C2-H compared to that of involving C4 and C5-H. [35] It is because, while C2 is positive (due to the electron deficient  bond formation of C=N bond), the C4 and C5 are essentially neutral (due to  bond formation between two carbon sharing equally the available electrons). [36] …”

Section: Fig 4 Dft Optimized Structure Of Different Imidazolium Basmentioning

confidence: 99%

Interactions and Transitions in Imidazolium Cation Based Ionic Liquids

Shukla¹,

Srivastava²,

Saha³

2011

Ionic Liquids - Classes and Properties

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“…[26] They mainly occur at the protons bound in C 2 and also-to a smaller extent-at the protons bound in C 4 and C 5 positions at the imidazolium ring (see Scheme 1). Hydrogen bonding has been proposed to be of crucial importance for the melting point as well as the viscosity of ILs.…”

Section: Introductionmentioning

confidence: 99%

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

Cremer

Kolbeck

Lovelock

et al. 2010

Chemistry A European J

277

335

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Ten [C(8)C(1)Im](+) (1-methyl-3-octylimidazolium)-based ionic liquids with anions Cl(-), Br(-), I(-), [NO(3)](-), [BF(4)](-), [TfO](-), [PF(6)](-), [Tf(2)N](-), [Pf(2)N](-), and [FAP](-) (TfO=trifluoromethylsulfonate, Tf(2)N=bis(trifluoromethylsulfonyl)imide, Pf(2)N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C(8)C(1)C(1)Im](+) (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br(-) and [Tf(2)N](-) were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While (1)H NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C(2) position and the anion, a comparative XPS study provides first direct experimental evidence for cation-anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid's anion. These charge-transfer effects are found to be surprisingly similar for [C(8)C(1)Im](+) and [C(8)C(1)C(1)Im](+) salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.

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The role of hydrogen atoms in interactions involving imidazolium-based ionic liquids

Cited by 151 publications

References 90 publications

Effects of C(2) Methylation on Thermal Behavior and Interionic Interactions in Imidazolium-Based Ionic Liquids with Highly Symmetric Anions

Effects of C(2) Methylation on Thermal Behavior and Interionic Interactions in Imidazolium-Based Ionic Liquids with Highly Symmetric Anions

Interactions and Transitions in Imidazolium Cation Based Ionic Liquids

Towards a Molecular Understanding of Cation–Anion Interactions—Probing the Electronic Structure of Imidazolium Ionic Liquids by NMR Spectroscopy, X‐ray Photoelectron Spectroscopy and Theoretical Calculations

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