Isotropic ordering of ions in ionic liquids on the sub-nanometer scale

Chen, Hailong; Chen, Xin; Deng, Jingwen; Zheng, Junrong

doi:10.1039/c7sc05184k

Cited by 13 publications

(14 citation statements)

References 39 publications

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“…The non-directional (coulombic) interactions lead to a more isotropic distribution of ionic species and the directional interactions (Van der Waals and hydrogen bonding) to an anisotropic distribution. An intermolecular interaction study based on Density Functional Theory (DFT) using [C 2 mim][BF 4 ] and [C 4 mim][PF 6 ] ILs demonstrated that the Coulombic Force contributes with 70% of total energy, which indicates that the other interactions, like hydrogen bonding, π–π stacking and dispersion interactions, should also affect significantly the physicochemical properties [ 38 , 39 ]. Recently, a thorough review focused on understanding heterogeneous microstructures and dynamics of ILs in bulk liquids, in mixtures with cosolvents, and in interfacial regions was published highlighting the importance of the interplay among the intra- and intermolecular interactions [ 40 ].…”

Section: Structural Organizationmentioning

confidence: 99%

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Silva

Zanatta

Ferreira

et al. 2020

IJMS

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In the last few years, ionic liquids (ILs) have been the focus of extensive studies concerning the relationship between structure and properties and how this impacts their application. Despite a large number of studies, several topics remain controversial or not fully answered, such as: the existence of ion pairs, the concept of free volume and the effect of water and its implications in the modulation of ILs physicochemical properties. In this paper, we present a critical review of state-of-the-art literature regarding structure–property relationship of ILs, we re-examine analytical theories on the structure–property correlations and present new perspectives based on the existing data. The interrelation between transport properties (viscosity, diffusion, conductivity) of IL structure and free volume are analysed and discussed at a molecular level. In addition, we demonstrate how the analysis of microscopic features (particularly using NMR-derived data) can be used to explain and predict macroscopic properties, reaching new perspectives on the properties and application of ILs.

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Section: Structural Organizationmentioning

confidence: 99%

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Silva

Zanatta

Ferreira

et al. 2020

IJMS

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show abstract

“…Thus, not only ILs are macroscopically isotropic, that is, they completely lack any real orientational and translational order of the phase, but also at the nanoscale level, where the micro‐segregation occurs, neither orientational nor translational order has been detected so far. In fact, as we have mentioned already, very recent experimental evidence points to a completely disordered structure of the ions in typical ILs.…”

Section: Structure Of Ionic Liquidsmentioning

confidence: 58%

“…However, as mentioned already, a very recent article suggested that the degree of local order, considering a cation and its first solvation shell of anions, is basically zero . Zheng and co‐workers have measured the anisotropy in the anion vibrational modes of some ionic liquids (e.g., the S─O stretching mode of bistriflimide) induced by a selective excitation of the cation vibrational modes (e.g., the C─H stretching of the imidazolium ring) . They observed no induced anisotropy in the anions within 0.01 units of anisotropy, this one being defined as

R = \frac{I_{false∥} - I_{⊥}}{I_{false∥} + 2 I_{⊥}}

where

I_{∥}

and

I_{⊥}

are the intensities measured with a parallel or perpendicular geometry of the polarizers, respectively.…”

Section: Structure Of Ionic Liquidsmentioning

confidence: 94%

Section: Structure Of Ionic Liquidsmentioning

confidence: 99%

“…[]. This idea has been further pushed forward by a recent experimental investigation: using 2D IR spectroscopy, the authors observed a lack of orientational correlation between neighboring ions; thus, they proposed that ILs can be described as a 3D network of interconnecting nanocomposite of molten‐salt‐like domains and molecular‐liquid‐like domains. We will come back to this point later with more details.…”

Section: Structure Of Ionic Liquidsmentioning

confidence: 99%

See 2 more Smart Citations

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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Multiple Ensembles of the Hydrogen‐bonded Network in Ethylammonium Nitrate versus Water from Vibrational Spectral Dynamics of SCN⁻ Probe

Biswas

Mallik

2022

ChemPhysChem

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We performed classical molecular dynamics simulations to monitor the structural interactions and ultrafast dynamical and spectral response in the protic ionic liquid, ethylammonium nitrate (EAN) and water using the nitrile stretching mode of thiocyanate ion (SCN À ) as the vibrational probe. The normalized frequency distribution of the nitrile stretch in SCN À attains an asymmetric shape in EAN, indicating the existence of more than one hydrogen-bonding environment in EAN. Further, we computed the 2D IR spectrum from classical trajectories, applying the response function formalism. Spectral diffusion dynamics in EAN undergo an initial rattling of the SCN À inside the local ion-cage occurring at a timescale of 0.10 ps, followed by the breakup of the ion-cage activating molecular diffusion at 7.86 ps timescale. In contrast, the dynamics of structural reorganization occur at a timescale of 0.58 ps in H 2 O. Hence, the time dependence of the frequency-frequency correlation function decay hints at the local molecular structure and ultrafast ion dynamics of the SCN À probe. The loss of frequency correlation read from the peak shape changes in the 2D correlation spectrum as a function of waiting time is faster in H 2 O than in EAN due to the enhanced structural ordering and higher viscosity of the latter. We provide an atomic-level interpretation of the solvation environment around SCN À in EAN and water, which indicates multiple ensembles of the hydrogen bond network in EAN.

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Isotropic ordering of ions in ionic liquids on the sub-nanometer scale

Abstract: This article investigates structures of ionic liquids.

Cited by 13 publications

References 39 publications

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation

Multiple Ensembles of the Hydrogen‐bonded Network in Ethylammonium Nitrate versus Water from Vibrational Spectral Dynamics of SCN⁻ Probe

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Isotropic ordering of ions in ionic liquids on the sub-nanometer scale

Abstract: This article investigates structures of ionic liquids.

Cited by 13 publications

References 39 publications

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Computational Spectroscopy of Ionic Liquids for Bulk Structure Elucidation

Multiple Ensembles of the Hydrogen‐bonded Network in Ethylammonium Nitrate versus Water from Vibrational Spectral Dynamics of SCN− Probe

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Product

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Multiple Ensembles of the Hydrogen‐bonded Network in Ethylammonium Nitrate versus Water from Vibrational Spectral Dynamics of SCN⁻ Probe