The Conductivity of Imidazolium-Based Ionic Liquids from (−35 to 195) °C. A. Variation of Cation’s Alkyl Chain

Stoppa, Alexander; Zech, Oliver; Kunz, Werner; Buchner, Richard

doi:10.1021/je900789j

Cited by 165 publications

(140 citation statements)

References 39 publications

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“…Walden's rule is often applied to ionic liquids, where the molar conductivity is assumed to be directly pro- portional to the fluidity. [24][25][26] Figure 5 shows a Walden plot for the data studied here and demonstrates an approximate relation between molar conductivity and fluidity, with a stronger correlation in the data as the temperature decreases. It is well known that Walden's rule is at best a rough approximation in both molten salts 26 and organic liquid electrolytes, 27 although this rule is at least qualitatively valid.…”

Section: Discussionmentioning

confidence: 79%

Mass and charge transport in 1-alkyl-3-methylimidazolium triflate ionic liquids

Petrowsky

Burba

Frech

2013

The Journal of Chemical Physics

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Temperature-dependent transport properties in ionic liquids, such as the ionic conductivity and fluidity, are often characterized empirically through equations that require multiple adjustable fitting parameters in order to adequately describe the data. These fitting parameters offer no insight into the molecular-level mechanism of transport. Here the temperature dependence of these transport properties in 1-alkyl-3-methylimidazolium triflate ionic liquids is explained using the compensated Arrhenius formalism (CAF), where the conductivity or fluidity assumes an Arrhenius-like form that also contains a dipole density dependence in the exponential prefactor. The resulting CAF activation energies for conductivity and fluidity are much higher than those obtained from polar organic liquids and electrolytes. The CAF very accurately describes the temperature dependence of both conductivity and fluidity using only system properties (i.e., density and activation energy). These results imply that the transport mechanism in molten salts is very similar to that in polar organic liquids and electrolytes.

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Section: Discussionmentioning

confidence: 79%

Mass and charge transport in 1-alkyl-3-methylimidazolium triflate ionic liquids

Petrowsky

Burba

Frech

2013

The Journal of Chemical Physics

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“…Viscosities, η, were measured with a rolling ball microviscometer (Anton Paar, Graz, Austria, AMVn) with ∼ 0.5 % repeatability in the range of 5 to 125°C. Electrical conductivities, κ, were determined in the temperature range of -45 to 190°C with an overall uncertainty of 0.5 % using the two setups described previously [31,32].…”

Section: Auxiliary Measurementsmentioning

confidence: 99%

Dynamics of RTILs: A comparative dielectric and OKE study

Sonnleitner

Turton

Waselikowski

et al. 2014

Journal of Molecular Liquids

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The dynamics of room-temperature ionic liquids (RTILs) were studied by investigating their dielectric relaxation (DR) and timeresolved optical Kerr-effect (OKE) spectra in the frequency range of ∼10 MHz to ∼20 THz. For the studied RTILs the OKE and DR spectra are dominated by a relaxation in the GHz region and extend to a relatively sharp band at around 10 THz. Whilst the first feature is mainly associated with the structural relaxation of the fluid through ion rotation (α relaxation), the second indicates the short-time limit of intermolecular dynamics. The rather featureless intermediate region is mainly associated with intermolecular vibrations that are strongly coupled to hindered rotations. In contrast to other RTILs, imidazolium salts show an additional sub-α relaxation which dominates the OKE signal and is indicative of the breathing motion of rather long-lived cages.Mixed with polar solvents RTILs were found to retain their ionic liquid-like character up to relatively high levels of dilution, but with the overall dynamics considerably speeded up. Below RTIL mole fractions of ∼0.2-0.4 these systems behave like conventional electrolyte solutions with more or less pronounced ion pairing.

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“…Electrical conductivities, k, were determined at (25.000 AE 0.003) 1C with an overall uncertainty of 0.5% using the setup described previously. 29,30 The obtained data for r, k, molar conductivity, L = k/c EAN , and Z are summarized in Table S1 (ESI †).…”

Section: Introductionmentioning

confidence: 99%

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

Sonnleitner

Nikitina

Nazet

et al. 2013

Phys. Chem. Chem. Phys.

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Binary mixtures of the protic ionic liquid ethylammonium nitrate (EAN) and acetonitrile (AN) were studied at 25 1C over the entire composition range by means of broadband dielectric spectroscopy covering 0.2 r n/GHz r 89. The dielectric spectra could be decomposed into two relaxation processes, both of which proved to be composite modes. For dilute solutions the higher-frequency Debye relaxation centered at B60 GHz is associated with the rotational diffusion of AN molecules, whereas at higher salt concentrations ultra-fast intermolecular vibrations and librations of EAN dominate the process. For EAN-rich solutions the lower-frequency relaxation is mainly due to jump reorientation of the ethylammonium cation, whereas contact ion pairs (CIPs) dominate this mode for dilute solutions. From the relaxation amplitudes effective solvation numbers and ion-pair concentrations were determined. For vanishing EAN mole fraction, x EAN -0, an effective cation solvation number of B7 was found which steeply drops until x EAN E 0.2 but shows only moderate decrease later on. The obtained association constant for EAN, K 0 A = 970 L mol À1 , exceeds that of other 1 : 1 electrolytes in AN by a factor of B30-50. This observation, as well as the fact that CIPs are formed despite strong cation solvation, indicates that ion pairing is mainly driven by the formation of strong hydrogen bonds between anions and cations.

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The Conductivity of Imidazolium-Based Ionic Liquids from (−35 to 195) °C. A. Variation of Cation’s Alkyl Chain

Cited by 165 publications

References 39 publications

Mass and charge transport in 1-alkyl-3-methylimidazolium triflate ionic liquids

Mass and charge transport in 1-alkyl-3-methylimidazolium triflate ionic liquids

Dynamics of RTILs: A comparative dielectric and OKE study

Do H-bonds explain strong ion aggregation in ethylammonium nitrate + acetonitrile mixtures?

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