Aggregation of Imidazolium Ionic Liquids in Molecular Liquids Studied by Small-Angle Neutron Scattering and NMR

Takamuku, Toshiyuki; Honda, Yuichi; Fujii, Kenta; Kittaka, Shigeharu

doi:10.2116/analsci.24.1285

Cited by 28 publications

(34 citation statements)

References 33 publications

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“…60 If the geometrical factor k of a given capillary has been calibrated in advance, then the separation between the two reference signals can be used to correct for the sample's magnetic susceptibility. 28,30,31,51,[54][55][56] In this study we present the results of a systematic investigation of ion solvation and association in FT-IR spectra were recorded at room temperature on a Bruker Tensor 27 spectrometer equipped with an ATR single reflection cell (ZnSe/diamond crystal) from Pike Technologies. Sample compartment was extensively flushed with nitrogen prior and during the measurements to avoid atmospheric water sorption.…”

Section: Problems Of Chemical Shift Referencingmentioning

confidence: 99%

“…0.05 ppm and 0.15 ppm in EmimCl-AN and by 0.07 ppm each in EmimTFSI-MeOH mixtures,54 by ca. 0.2 ppm each in EmimTFSI-DMSO/AN mixtures 28.…”

mentioning

confidence: 95%

“…exhibit more significant deshielding than the terminal methyl ones, i.e., positive relative chemical shift variations are observed: EmimTFSI-Ac-d 6 ,25 RmimPF 6 /BF 4 -Ac-d6 ,27 EmimTFSIMeOH/DMSO/H 2 O 28,51,54. For some systems, however, there was no appreciable difference in chemical shift variation for the ring hydrogen atoms and the terminal methyl which resulted in roughly zero values of the relative chemical shift variations like in BmimBF 4 -H 2 O (note that there is a number of reports for this system concerning negative values of the relative chemical shift variation),75,76 and RmimBF 4 -ethylene glycol 79.…”

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confidence: 99%

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Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative¹H and¹³C NMR chemical shifts

Marekha

Kalugin

Bria

et al. 2015

Phys. Chem. Chem. Phys.

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Mixtures of ionic liquids (ILs) with polar aprotic solvents in different combinations and under different conditions (concentration, temperature etc.) are used widely in electrochemistry. However, little is known about the key intermolecular interactions in such mixtures depending on the nature of the constituents and mixture composition. In order to systematically address the intermolecular interactions, the chemical shift variation of (1)H and (13)C nuclei has been followed in mixtures of imidazolium ILs 1-n-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4), 1-n-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6), 1-n-butyl-3-methylimidazolium trifluoromethanesulfonate (BmimTfO) and 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BmimTFSI) with molecular solvent acetonitrile (AN) over the entire composition range at 300 K. The concept of relative chemical shift variation is proposed to assess the observed effects on a unified and unbiased scale. We have found that hydrogen bonds between the imidazolium ring hydrogen atoms and electronegative atoms of anions are stronger in BmimBF4 and BmimTfO ILs than those in BmimTFSI and BmimPF6. Hydrogen atom at position 2 of the imidazolium ring is substantially more sensitive to interionic hydrogen bonding than those at positions 4-5 in the case of BmimTfO and BmimTFSI ILs. These hydrogen bonds are disrupted upon dilution in AN due to ion dissociation which is more pronounced at high dilutions. Specific solvation interactions between AN molecules and IL cations are poorly manifested.

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Section: Problems Of Chemical Shift Referencingmentioning

confidence: 99%

“…0.05 ppm and 0.15 ppm in EmimCl-AN and by 0.07 ppm each in EmimTFSI-MeOH mixtures,54 by ca. 0.2 ppm each in EmimTFSI-DMSO/AN mixtures 28.…”

mentioning

confidence: 95%

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confidence: 99%

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Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative¹H and¹³C NMR chemical shifts

Marekha

Kalugin

Bria

et al. 2015

Phys. Chem. Chem. Phys.

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“…[1][2][3][4] The potential properties and fields of application of ILs can be further expanded by considering mixtures with molecular liquids, in particular water and alcohols. [5][6][7][8][9][10][11][12] It is well known that only trace amounts of water can fluidise ILs significantly. [10][11][12] Thus, it is of interest to understand how cations, anions and molecules of these liquids interact with each other and determine the overall properties of the mixtures.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Methanol in Ionic Liquids: Validity of the Stokes–Einstein and Stokes–Einstein–Debye Relations

et al. 2014

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The validity of Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations for methanol in the physical environment of the ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is studied by means of nuclear magnetic resonance (NMR) relaxation time experiments, viscosity measurements and molecular dynamics (MD) simulations. The reorientational correlation times of the hydroxyl groups of pure methanol and of methanol in the IL/methanol mixtures were determined. For that purpose an approach for estimating NMR deuteron quadrupole coupling constants, presented by Wendt and Farrar (Mol. Phys. 1998, 95, 1077-1081), was confirmed. The self-diffusion coefficients of methanol were taken from the MD simulations. The viscosities of all systems were then measured and the SE and SED relations validated. For pure methanol both relations are valid, whereas they become increasingly invalid with increasing IL concentration, as indicated by effective volumes and radii that are too low. The deviation from the SE and SED relations could be related to dynamical heterogeneities described by the non-Gaussian parameter α(t) obtained from MD simulations. For pure methanol, α(t) is close to zero in accord with the validity of both relations. With increasing IL concentration the dynamical heterogeneities of methanol increase strongly. The times t* at the maximum of α(t) increase linearly with the relative number of methanol monomers in the mixtures. Thus, the dynamical heterogeneities are largest for single methanol molecules fully embedded in the IL environment. In their own environment methanol molecules are highly mobile, whereas in the IL-rich region the mobility is strongly reduced leading to the non-validity of SE and SED relations.

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“…2͑d͒ and 2͑e͒ suggest that the nature of local organization of imidazolium C-H in CD 3 OD mixtures is different from that in CD 3 CN mixtures. 49 The imidazolium C-H spectral features observed in Figs. 2͑d͒ and 2͑e͒ may be related to the geometrical properties of hydrogen-bond network in liquid methanol.…”

Section: Resultsmentioning

confidence: 98%

Solvation and microscopic properties of ionic liquid/acetonitrile mixtures probed by high-pressure infrared spectroscopy

Umebayashi

Jiang

Lin

et al. 2009

The Journal of Chemical Physics

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The microscopic features of binary mixtures formed by an ionic liquid (EMI(+)TFSA(-) or EMI(+)FSA(-)) and a molecular liquid (acetonitrile or methanol) have been investigated by high-pressure infrared spectroscopy. On the basis of its responses to changes in pressure and concentration, the imidazolium C-H appears to exist at least in two different forms, i.e., isolated and associated structures. The weak band at approximately 3102 cm(-1) should be assigned to the isolated structure. CD(3)CN can be added to change the structural organization of ionic liquids. The compression of an EMI(+)TFSA(-)/CD(3)CN mixture leads to the increase in the isolated C-H band intensity. Nevertheless, the loss in intensity of the isolated structures was observed for EMI(+)FSA(-)/CD(3)CN mixtures as the pressure was elevated. In other words, the associated configuration is favored with increasing pressure by debiting the isolated form for EMI(+)FSA(-)/CD(3)CN mixtures. The stronger C-H...F interactions in EMI(+)FSA(-) may be one of the reasons for the remarkable differences in the pressure-dependent results of EMI(+)TFSA(-) and EMI(+)FSA(-).

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Aggregation of Imidazolium Ionic Liquids in Molecular Liquids Studied by Small-Angle Neutron Scattering and NMR

Cited by 28 publications

References 33 publications

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative¹H and¹³C NMR chemical shifts

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative¹H and¹³C NMR chemical shifts

Dynamics of Methanol in Ionic Liquids: Validity of the Stokes–Einstein and Stokes–Einstein–Debye Relations

Solvation and microscopic properties of ionic liquid/acetonitrile mixtures probed by high-pressure infrared spectroscopy

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Aggregation of Imidazolium Ionic Liquids in Molecular Liquids Studied by Small-Angle Neutron Scattering and NMR

Cited by 28 publications

References 33 publications

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative1H and13C NMR chemical shifts

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative1H and13C NMR chemical shifts

Dynamics of Methanol in Ionic Liquids: Validity of the Stokes–Einstein and Stokes–Einstein–Debye Relations

Solvation and microscopic properties of ionic liquid/acetonitrile mixtures probed by high-pressure infrared spectroscopy

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Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative¹H and¹³C NMR chemical shifts

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative¹H and¹³C NMR chemical shifts