Vaporization of Protic Ionic Liquids Studied by Matrix-Isolation Fourier Transform Infrared Spectroscopy

Horikawa, Mami; Akai, Nobuyuki; Kawai, Akio; Shibuya, Kazuhiko

doi:10.1021/jp501784w

Cited by 23 publications

(24 citation statements)

References 35 publications

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“…The Δ vap H values from Verevkin and co-workers for three protic ILs are excluded [ 150 ]. It is expected that the vapour phase for the three ILs studied will mainly comprise ionic vapour [ 67 ] and not non-ionic TD product vapour (most likely the products of proton transfer from the cation to the anion), but no evidence is presented to confirm this supposition. For protic ILs, ideally a Δ vap H technique would be used that can distinguish between IL vaporization and TD product vaporization.…”

Section: Measuring the Cohesive Energy Density For Ionic Liquids: Ovementioning

confidence: 99%

“…Most of the focus has been on [NTf 2 ] − -based ILs, which have the required combination of relatively good thermal stability and relatively high volatility [31,64,65]. Aprotic ILs are the focus of this article, as very few vaporization studies of protic ILs have been published, in particular on identification of the vapour phase species [66][67][68][69].…”

Section: Ionic Liquids Can Be Distilledmentioning

confidence: 99%

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Quantifying intermolecular interactions of ionic liquids using cohesive energy densities

Lovelock¹

2017

R. Soc. open sci.

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For ionic liquids (ILs), both the large number of possible cation + anion combinations and their ionic nature provide a unique challenge for understanding intermolecular interactions. Cohesive energy density, ced, is used to quantify the strength of intermolecular interactions for molecular liquids, and is determined using the enthalpy of vaporization. A critical analysis of the experimental challenges and data to obtain ced for ILs is provided. For ILs there are two methods to judge the strength of intermolecular interactions, due to the presence of multiple constituents in the vapour phase of ILs. Firstly, cedIP, where the ionic vapour constituent is neutral ion pairs, the major constituent of the IL vapour. Secondly, cedC+A, where the ionic vapour constituents are isolated ions. A cedIP dataset is presented for 64 ILs. For the first time an experimental cedC+A, a measure of the strength of the total intermolecular interaction for an IL, is presented. cedC+A is significantly larger for ILs than ced for most molecular liquids, reflecting the need to break all of the relatively strong electrostatic interactions present in ILs. However, the van der Waals interactions contribute significantly to IL volatility due to the very strong electrostatic interaction in the neutral ion pair ionic vapour. An excellent linear correlation is found between cedIP and the inverse of the molecular volume. A good linear correlation is found between IL cedIP and IL Gordon parameter (which are dependent primarily on surface tension). ced values obtained through indirect methods gave similar magnitude values to cedIP. These findings show that cedIP is very important for understanding IL intermolecular interactions, in spite of cedIP not being a measure of the total intermolecular interactions of an IL. In the outlook section, remaining challenges for understanding IL intermolecular interactions are outlined.

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Section: Measuring the Cohesive Energy Density For Ionic Liquids: Ovementioning

confidence: 99%

Section: Ionic Liquids Can Be Distilledmentioning

confidence: 99%

Quantifying intermolecular interactions of ionic liquids using cohesive energy densities

Lovelock¹

2017

R. Soc. open sci.

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“…For example, Akai and co‐workers reported the IR spectra of several protic ionic liquids evaporated and then isolated in a neon matrix and compared the results with the calculated vibrational spectra for selected geometries of the ion‐pairs. The comparison allowed to select the stable geometries and to gain insights on the evaporation mechanism . The stretching vibration of the hydroxyl group was the main target of the comparison between DFT calculated and experimental vibrational frequencies of [C 2 OHMIM][BF 4 ]‐acetonitrile mixtures which allowed to identify several species present in solution …”

Section: Computational Vibrational Spectroscopymentioning

confidence: 99%

Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation

Saielli

2018

Advcd Theory and Sims

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Computational spectroscopy" refers to quantum chemistry protocols capable of predicting the electronic and/or magnetic spectra of molecules. The most common techniques used for structural assignment are infrared, electronic, and NMR spectroscopies. Chemists can normally deduce the chemical structure of an unknown substance by using a vast collection of empirical relationships linking the spectral features with the presence or absence of functional groups and, this part mostly by NMR, the connectivity between them and the relative stereochemistry. Computational spectroscopy is a powerful aid for structural elucidation when empirical relationships do not suffice to unambiguously assign the structure. In these cases, the calculated spectrum of a putative structure is compared with the experimental one and the match, or lack thereof, between the two, measured by several statistical parameters, indicates whether or not that structure is the correct one. Is it possible to extend such protocols to bulk phases of complex fluids, such as ionic liquids, rather than covalent molecules, in order to get insights into the average structure of the fluid? It is the aim of this Progress Report to highlight recent advances in this field through the discussion of specific case studies.

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“…Vibrational data can be linked to experimental spectra (IR and Raman). However, for ion pairs and small clusters spectroscopic matrix isolation studies offer the best experimental technique for direct comparison with computed vibrations [45, 56, 96]. The computation of NMR spectra is also possible [81, 97, 98].…”

Section: Properties and Bonding Analysismentioning

confidence: 99%

Quantum Chemical Modeling of Hydrogen Bonding in Ionic Liquids

Hunt

2017

Top Curr Chem (Z)

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Hydrogen bonding (H-bonding) is an important and very general phenomenon. H-bonding is part of the basis of life in DNA, key in controlling the properties of water and ice, and critical to modern applications such as crystal engineering, catalysis applications, pharmaceutical and agrochemical development. H-bonding also plays a significant role for many ionic liquids (IL), determining the secondary structuring and affecting key physical parameters. ILs exhibit a particularly diverse and wide range of traditional as well as non-standard forms of H-bonding, in particular the doubly ionic H-bond is important. Understanding the fundamental nature of the H-bonds that form within ILs is critical, and one way of accessing this information, that cannot be recovered by any other computational method, is through quantum chemical electronic structure calculations. However, an appropriate method and basis set must be employed, and a robust procedure for determining key structures is essential. Modern generalised solvation models have recently been extended to ILs, bringing both advantages and disadvantages. QC can provide a range of information on geometry, IR and Raman spectra, NMR spectra and at a more fundamental level through analysis of the electronic structure.

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Vaporization of Protic Ionic Liquids Studied by Matrix-Isolation Fourier Transform Infrared Spectroscopy

Cited by 23 publications

References 35 publications

Quantifying intermolecular interactions of ionic liquids using cohesive energy densities

Quantifying intermolecular interactions of ionic liquids using cohesive energy densities

Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation

Quantum Chemical Modeling of Hydrogen Bonding in Ionic Liquids

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