Anion–cation and ion–solvent interaction of some typical ionic liquids in solvents with different dielectric constant

Hu, Xingbang; Lin, Qiuxing; Gao, Junyang; Wu, Youting; Zhang, Zhibing

doi:10.1016/j.cplett.2011.09.051

Cited by 58 publications

(38 citation statements)

References 48 publications

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“…As a result, the ion pair binding energy drastically drops from the vacuum value of −359.9 kJ mol −1 to −32.5 kJ mol −1 in the PCM approach. This result is in accordance with previous computational studies which show that increasing the solvent polarity progressively weakens the ion pairing in terms of the PCM‐estimated ion pair binding energies.…”

Section: Resultssupporting

confidence: 93%

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Intermolecular interactions, ion solvation, and association in mixtures of 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate and γ‐butyrolactone: insights from Raman spectroscopy

Marekha

Koverga

Moreau

et al. 2015

J Raman Spectroscopy

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By means of Raman spectroscopy coupled with density functional theory (DFT) calculations and perturbation correlation moving window two-dimensional correlation spectroscopy intermolecular interactions were assessed in mixtures of ionic liquid (IL) 1-nbutyl-3-methylimidazolium hexafluorophosphate (BmimPF 6 ) with polar aprotic solvent γ-butyrolactone (γ-BL) over the entire range of compositions. The symmetrical P-F stretching vibration of the IL anion was found to be insensitive to the changes in mixture concentration in contrast to the C¼O stretching vibration of the γ-BL and the imidazolium ring C-H stretching vibrations of the IL cation. Each of these vibrational profiles was decomposed in various spectral contributions, and their number was rationalized by the results of quantum-chemical calculations and/or previous controversial published data. Progressive redshift of the ring C-H stretching wavenumbers was referred to pronounced solvation of the cation at the imidazolium ring site accompanied with H-bond formation. This was especially pronounced at IL mole fraction less than 0.18. Complicated variations in the intensities of the individual contributions of the C¼O profile were treated as a manifestation of the changing with concentration pattern of the intermolecular interactions. The self-association of γ-BL molecules and distinct cation solvation as dominant intermolecular interactions at low IL content are replaced with weaker cation solvation and ion association at high concentrations of IL. Possible representative molecular structures were proposed on the basis of DFT calculations.

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Section: Resultssupporting

confidence: 93%

“…We also note that in terms of the competition energy defined by Hu et al . from the PCM calculations as the difference between the sum of the cation–solvent and anion–solvent binding energies from one side and the ion pair binding energy from another side one can expect a balanced competition between the ion pairing and the ion solvation.…”

Section: Resultsmentioning

confidence: 82%

Intermolecular interactions, ion solvation, and association in mixtures of 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate and γ‐butyrolactone: insights from Raman spectroscopy

Marekha

Koverga

Moreau

et al. 2015

J Raman Spectroscopy

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“…[93] In the case of the ion pair formed by the methylimidazolium cation and the dicyanamide anion, the PCM reveals free energies of solvation increasing in the series water, DMSO, and acetonitrile, and even more in solvents with lower dielectric constants. [94] Similarly, the binding energy of the EMI cation [95] as well as ethanolaminic cations [96] with several anions has been demonstrated to increase significantly in solvents with lower dielectric constants. For the ion pair composed by MMIM and the methylsulphate anion, PCM calculations in water and ethanol suggest ion pair separation.…”

Section: Quantum Mechanical Investigationsmentioning

confidence: 96%

Imidazolium Salt Ion Pairs in Solution

Stassen

Ludwig

Wulf

et al. 2015

Chemistry A European J

169

151

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The formation, stabilisation and reactivity of contact ion pairs of non-protic imidazolium ionic liquids (ILs) in solution are conceptualized in light of selected experimental evidence as well theoretical calculations reported mainly in the last ten years. Electric conductivity, NMR, ESI-MS and IR data as well as theoretical calculations support not only the formation of contact ion pairs in solution, but also the presence of larger ionic and neutral aggregates even when dissolved in solvents with relatively high dielectric constants, such as acetonitrile and DMSO. The presence of larger imidazolium supramolecular aggregates is favoured at higher salt concentrations in solvents of low dielectric constant for ILs that contain shorter N-alkyl side chains associated with anions of low coordination ability. The stability and reactivity of neutral contact species are also dependent on the nature of the anion, imidazolium substituents, and are more abundant in ILs containing strong coordinating anions, in particular those that can form charge transfer complexes with the imidazolium cation. Finally, some ILs display reactivities as contact ion pairs rather than solvent-separated ions.

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“…Solvation effects on anion-cation binding energies were investigated previously. [23][24][25] A number of approaches exist to capture solvation interactions in ab initio calculations, divided into three types, including continuum-based models such as the polarizable continuum model (PCM), [26][27][28][29] explicit atomistic solvent models, and the combination of atomistic and continuum methods. The PCM is easily utilized in practice and may accurately capture long range solute-solvent interactions but fails to accurately describe strong, local interactions in the first coordination shell.…”

Section: Introductionmentioning

confidence: 99%

Cluster-continuum quantum mechanical models to guide the choice of anions for Li+-conducting ionomers

Shiau

Liu

Colby

et al. 2013

The Journal of Chemical Physics

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A quantum-mechanical investigation on Li poly(ethylene oxide)-based ionomers was performed in the cluster-continuum solvation model (CCM) that includes specific solvation in the first shell surrounding the cation, all surrounded by a polarizable continuum. A four-state model, including a free Li cation, Li(+)-anion pair, triple ion, and quadrupole was used to represent the states of Li(+) within the ionomer in the CCM. The relative energy of each state was calculated for Li(+) with various anions, with dimethyl ether representing the ether oxygen solvation. The population distribution of Li(+) ions among states was estimated by applying Boltzmann statistics to the CCM energies. Entropy difference estimates are needed for populations to better match the true ionomer system. The total entropy change is considered to consist of four contributions: translational, rotational, electrostatic, and solvent immobilization entropies. The population of ion states is reported as a function of Bjerrum length divided by ion-pair separation with/without entropy considered to investigate the transition between states. Predicted concentrations of Li(+)-conducting states (free Li(+) and positive triple ions) are compared among a series of anions to indicate favorable features for design of an optimal Li(+)-conducting ionomer; the perfluorotetraphenylborate anion maximizes the conducting positive triple ion population among the series of anions considered.

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Anion–cation and ion–solvent interaction of some typical ionic liquids in solvents with different dielectric constant

Cited by 58 publications

References 48 publications

Intermolecular interactions, ion solvation, and association in mixtures of 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate and γ‐butyrolactone: insights from Raman spectroscopy

Intermolecular interactions, ion solvation, and association in mixtures of 1‐n‐butyl‐3‐methylimidazolium hexafluorophosphate and γ‐butyrolactone: insights from Raman spectroscopy

Imidazolium Salt Ion Pairs in Solution

Cluster-continuum quantum mechanical models to guide the choice of anions for Li+-conducting ionomers

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