Structure and Dynamics of 1-Ethyl-3-methylimidazolium Acetate via Molecular Dynamics and Neutron Diffraction

Bowron, Daniel T.; D’Agostino, Carmine; Gladden, Lynn F.; Hardacre, Christopher; Holbrey, John D.; Lagunas, M. Cristina; McGregor, James; Mantle, Mick D.; Mullan, Claire L.; Youngs, Tristan G. A.

doi:10.1021/jp102180q

Cited by 120 publications

(139 citation statements)

References 35 publications

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“…Indeed, molecular dynamics simulations and neutron diffraction studies on 1-ethyl-3-methylimidazolium acetate revealed the liquid structure as inplane interactions of acetate oxygen atoms with the three imidazolium ring hydrogens and cation−cation planar stacking above/below the imidazolium rings. 40 This in-plane organized liquid structure through strong directional hydrogen bonds for the imidazolium-based ILs also supports the intriguing observation of a lower value of viscosity for the [ 39,41 Trying to foster a deeper analysis on this phenomenon, we further carried out mass spectrometry studies. These observations are in fact supported by mass spectrometry data concerning the gas phase fragmentation of isolated [(Cation) 2 Anion] + aggregates induced by collision with a neutral gas (MS/MS).…”

Section: ■ Results and Discussionsupporting

confidence: 72%

Thermophysical Properties of Five Acetate-Based Ionic Liquids

et al. 2012

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Ionic liquids (ILs) with improved hydrogen-bonding acceptor abilities, such as acetate-based compounds, have shown great potential for CO 2 capture and biomass dissolution. In this context, the knowledge of the thermophysical properties of acetate-based fluids is essential for the design and scale-up of related processes. However, at this stage, acetate-based ILs are still poorly characterized. In this work, four thermophysical properties, specifically, density, viscosity, refractive index, and surface tension, were determined for five acetate-based ILs. Both protic and aprotic ILs were investigated, namely, N,N-dimethyl-N-ethylammonium acetate, 1-ethylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, and 1-butyl-1-methylpyrrolidinium acetate. From the temperature dependence of the measured properties, additional properties, such as the isobaric thermal expansion coefficient, the surface entropy and enthalpy, and the critical temperature, were further estimated. ■ INTRODUCTIONDuring the past decade research has emerged in various areas involving ionic liquids (ILs), and their potential applications are nowadays widespread. Ionic liquids are a group of molten salts normally composed of inorganic or organic anions, and relatively large organic cations, which do not easily form an ordered crystal and, therefore, they remain liquid at or near room temperature. 1−3 Recently, certain classes of ILs with improved hydrogenbonding acceptor capability, such as acetate-based fluids, have shown to be promising solvents for CO 2 capture 4−7 and cellulose and/or biomass dissolution. 8−11 Acetate-based fluids are able to strongly coordinate with CO 2 and hydrogen bond donator groups, such as −OH groups, and favorable results have thus been published. Moreover, acetate-based ILs present low toxicity, low corrosiveness, and favorable biodegradability. 12 Despite their undeniable interest, the thermophysical properties of acetate-based fluids are still poorly characterized. In a previous work we have determined the densities and viscosities of a series of imidazolium-based ILs which have shown potential for the dissolution of biomass. 13 Fendt et al. 14 presented the viscosities of acetate-based ILs and some of their mixtures with water and organic solvents. Qian et al. 15 explored the densities and viscosities of the protic IL 1-methylimidazolium acetate and its binary mixtures with alcohols. Additional scarce reports have addressed the measurements of densities, 16−18 viscosities, 19 refractive index, 16,20 and surface tension 18 of aprotic acetate-based ILs.In this work, the thermophysical properties of acetate-based ILs, specifically density, viscosity, refractive index, and surface tension, were measured as a function of temperature. The ILs are formed by the common anion acetate, combined either with protic (N,N-dimethyl-N-ethylammonium and 1-ethylimidazolium) or aprotic cations (1-ethyl-3-methylimidazolium, 1-butyl-3-methylimidazolium and 1-butyl-1-methylpyrrolydinium). Additio...

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Section: ■ Results and Discussionsupporting

confidence: 72%

Thermophysical Properties of Five Acetate-Based Ionic Liquids

et al. 2012

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“…The first one considered a trimer of BmimAc. Its initial configuration was built following the structure proposed by neutron scattering experiment for the EmimAc/water mixture [62]. In the second approach, the Monte Carlo computational method [63] was used to obtain the initial configuration of one BmimAc ion pair solvated by water molecules.…”

Section: Methodsmentioning

confidence: 99%

“…The initial configuration of water around BmimAc was obtained from Monte Carlo simulation of one BmimAc in a simulation box of 863 water molecules. In the case of the trimer, the initial configuration is based on the optimized geometry of Emim-Ac[62].…”

mentioning

confidence: 99%

Intermolecular interactions in mixtures of 1-n-butyl-3-methylimidazolium acetate and water: Insights from IR, Raman, NMR spectroscopy and quantum chemistry calculations

Marekha

Bria

Moreau

et al. 2015

Journal of Molecular Liquids

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“…63 This is because the existing force field models for ILs overestimate the charges on the ions, thereby leading to increased electrostatic interactions and decreased dynamics. Recently, new force field parameters for ILs based on refined charges have been found to show a good match with experimental data on the structure and dynamics of neat ILs.…”

Section: Ils Inmentioning

confidence: 99%

Nanostructural Reorganization Manifests in Sui-Generis Density Trend of Imidazolium Acetate/Water Binary Mixtures

Ghoshdastidar

Senapati

2015

J. Phys. Chem. B

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Ionic liquids (ILs) are emerging as a novel class of solvents in chemical and biochemical research. Their range of applications further expands when a small quantity of water is added. Thus, the past decade has seen extensive research on IL/water binary mixtures. While the thermophysical properties of most of these mixtures exhibited the expected trend, few others have shown deviations from the general course. One such example is the increase in density of the 1-alkyl-3-methyl imidazolium acetate ([Rn mim][Ac])-based ILs with the addition of low to moderate concentrations of water. Although such a unique trend was observed for imidazolium cations of different tail lengths and also from independent experiments, the molecular basis of this unique behavior remains unknown. In this study, we examine the nanostructural reordering in [Rn mim][Ac] (n = 2-6) ILs due to added water by means of molecular dynamics simulations, and correlate the observed changes to the sui-generis density trend. Results suggest that the initial rise in density in these ILs mainly pertains to the water-induced increased spatial correlation among the polar components, where high basicity of the acetate anion plays a key role. At moderate water concentration, the density can rise further for ILs with longer cation tails due to hydrophobic clustering. Thus, while [emim][Ac]/water mixtures exhibit the density turnover at Xw = 0.5, [bmim][Ac] and [hmim][Ac] show the turnover at Xw = 0.7. The detailed understanding provided here could help the preparation of optimal IL/water binary mixtures for various biochemical applications.

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Structure and Dynamics of 1-Ethyl-3-methylimidazolium Acetate via Molecular Dynamics and Neutron Diffraction

Cited by 120 publications

References 35 publications

Thermophysical Properties of Five Acetate-Based Ionic Liquids

Thermophysical Properties of Five Acetate-Based Ionic Liquids

Intermolecular interactions in mixtures of 1-n-butyl-3-methylimidazolium acetate and water: Insights from IR, Raman, NMR spectroscopy and quantum chemistry calculations

Nanostructural Reorganization Manifests in Sui-Generis Density Trend of Imidazolium Acetate/Water Binary Mixtures

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