Probing molecular interaction in ionic liquids by low frequency spectroscopy: Coulomb energy, hydrogen bonding and dispersion forces

Fumino, Koichi; Reimann, Stefan; Ludwig, Ralf

doi:10.1039/c4cp01476f

Cited by 219 publications

(207 citation statements)

References 179 publications

(207 reference statements)

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“…However, no self-association occurs in N,N-dimethylaniline. Also, in ionic liquids, cation-anion interactions exist, as a result of subtle balance between hydrogen bonds, Coulomb forces and dispersion interactions between alkyl chains [16]. Thus, spectroscopic studies [95,96] …”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, ionic liquids reveal very interesting fundamental features: i) they have specific structure represented by polar (ionic) and non-polar (aliphatic) domains [4], which is crucial for the aforementioned diverse solvent power and ii) they allow a variety of interactions in their mixtures: dispersion forces between aliphatic chains present in the mixtures of imidazolium ionic liquids with alcohols [15]; strong interactions such as ionic (Coulomb forces [16] and ion-dipole interactions [17]), hydrogen bonds [15,[18][19][20], and specific interactions with the aromatic compounds [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

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Excess molar volumes and viscosity behaviour of binary mixtures of aniline/or N,N-dimethylaniline with imidazolium ionic liquids having triflate or bistriflamide anion

Soldatović¹,

Vuksanović

Radović

et al. 2017

The Journal of Chemical Thermodynamics

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In this study, densities and viscosities of four binary systems {aniline / N, N-dimethylaniline+1- Also, enthalpic and entropic parts of the ∆G *E function were determined, at the same composition, for three studied systems that exhibit complete miscibility, since {aniline + [bmim][OTf]} is a partially miscible system. Considering the calculated thermodynamic properties, molecular interactions in the investigated binary systems were analysed and are discussed.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Excess molar volumes and viscosity behaviour of binary mixtures of aniline/or N,N-dimethylaniline with imidazolium ionic liquids having triflate or bistriflamide anion

Soldatović¹,

Vuksanović

Radović

et al. 2017

The Journal of Chemical Thermodynamics

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“…The hydrogen-bonding contribution to the overall interaction energy in aprotic ILs is today widely accepted and well documented among others using far infrared and terahertz spectroscopy (FIR and THZ) studies, [38][39][40] and although such contribution is only about 10 %, the nature of hydrogen-bond interactions (e.g., directional) can significantly influence the properties of such ILs. Generally, ILs can be treated as structured solvents (from ion pairs, ion…”

Section: Ultrasound Absorptionmentioning

confidence: 99%

Ultrasonic Relaxation Study of 1-Alkyl-3-methylimidazolium-Based Room-Temperature Ionic Liquids: Probing the Role of Alkyl Chain Length in the Cation

et al. 2016

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Ultrasound absorption spectra of four 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide were determined as a function of the alkyl chain length on the cation from 1-propyl-to 1-hexyl-from 293.15 to 323.15 K at ambient pressure. Herein, the ultrasound absorption measurements were carried out using a standard pulse technique within a frequency range from 10 to 300 MHz. Additionally the speed of sound, density and viscosity have been measured. The presence of strong dissipative processes during the ultrasound wave propagation was found experimentally, i.e. relaxation processes in the megahertz range were observed for all compounds over the whole temperature range. The relaxation spectra (both relaxation amplitude and relaxation frequency) were shown to be dependent on the alkyl side chain length of the 1-alkyl-3-methylimidazolium ring. In most cases, a single Debye model described the absorption spectra very well. However, a comparison of the determined spectra with the spectra of a few other imidazolium-based ionic liquids reported in the literature (in part recalculated in this work) shows that the complexity of the spectra increases rapidly with the elongation of the alkyl chain length on the cation.This complexity indicates that both the volume viscosity and the shear viscosity are involved in relaxation processes even in relatively low frequency ranges. As a consequence, the sound velocity dispersion is present at relatively low megahertz frequencies.

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“…[35,36] Such binding energies for "doubly ionic hydrogen bonds" lie between 300 and 400 kJ mol À1 which is typical for cation anion interaction in ionic liquids. [37][38][39][40][41] Fora djusting the pure Hbond energy we also calculated asimilar ion pair, wherein the hydroxy group is replaced by amethyl group for eliminating the favorable OH···O interaction. Thec alculated H-bond energies are 8.9 kJ mol À1 and 13.59 kJ mol À1 ,respectively (see SI9).…”

Section: Introductionmentioning

confidence: 99%

Large Stokes Shift Ionic‐Liquid Dye

et al. 2017

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Abstract:We have incorporated the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he IL dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide [6MQc][NTf 2 ]w as characterized by NMR, ATRI R spectroscopya nd X-ray crystallography.T he fluorescence of the IL dye has al arge Stokes shift of Dl = 116 nm and aq uantum yield of f F = 0.56 in acetonitrile.C haracteristic solvent dependent shifts can be detected in the emission spectra. In other ILs,acetonitrile and THF we observe abathochromic shift of up to 28 nm compared to the pure IL dye at 467 nm. Forstronger polar solvents the fluorescence signals are strongly red-shifted to 650 nm indicating proton transfer to the solvent molecules in the excited state.T his underlines the importance of the IL building block [ MQc] + as photo acid.Fluorescent dyes are important tools in many branches of chemistry related sciences,s uch as biological chemistry, [1][2][3][4][5][6][7][8] materials science, [9][10][11] or solar-energy conversion. [12,13] Attractive fluorescent dyes are characterized by their extended spectral range,h igh emission quantum yields,p hotostability and good solubility in the solvent. Thef luorescent dye N-methyl-6-oxyquinolone [6MQz] was used for studying solvation phenomena. Thec olor of this solvatochromatic dye molecule depends strongly on the polarity of the surrounding,a st he permanent dipole moments strongly change upon excitation from the ground to the excited state.T hus [6MQz] has been used as dye for understanding solvation processes and proton transfer to solvents. [14][15][16][17][18][19][20][21][22] In some cases the polarity probe was incorporated into biomolecules such as sugars or enzymes for probing the chemical environment and providing biocompatibility. [10,11,18,19] Whereas other dyes have been extensively applied to probe the polarity of ionic liquids,t he protonated form of [6MQz] has never been used as moiety of an ionic liquid itself. [23,24] Thus,t he goal of our work was to incorporate the dye N-methyl-6-oxyquinolone [6MQz] in its protonated form as acation into an ionic liquid (IL) and thus to synthesize an IL dye.T he resulting ionic liquid dye N-methyl-6-hydroxyquinolinium bis(trifluoromethylsulfonyl) imide ]involves anion metathesis reaction and is shown in Scheme 1. Initial N-methyl-6-hydroxyquinolinium iodide was prepared using ak nown procedure which is also described in the Supporting Information (SI0). [25,26] Then, equimolar amounts of N-methyl-6-hydroxyquinolinium iodide (287 mg, 1mmol) and silver bis(trifluoromethylsulfonyl)imide (388 mg, 1mmol) were dissolved in 15 mL water each. Thet wo solutions were combined and the reaction mixture was stirred for 15 min. Silver iodide,which precipitates instantly,was filtered off and discarded. Them other liquor was removed on ar otary evaporator and the residue was dissolved in 25 mL ethanol to carry out ah ot-filtration with activated charcoal. After filtration, the solvent wa...

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Probing molecular interaction in ionic liquids by low frequency spectroscopy: Coulomb energy, hydrogen bonding and dispersion forces

Cited by 219 publications

References 179 publications

Excess molar volumes and viscosity behaviour of binary mixtures of aniline/or N,N-dimethylaniline with imidazolium ionic liquids having triflate or bistriflamide anion

Excess molar volumes and viscosity behaviour of binary mixtures of aniline/or N,N-dimethylaniline with imidazolium ionic liquids having triflate or bistriflamide anion

Ultrasonic Relaxation Study of 1-Alkyl-3-methylimidazolium-Based Room-Temperature Ionic Liquids: Probing the Role of Alkyl Chain Length in the Cation

Large Stokes Shift Ionic‐Liquid Dye

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