Confirmation of local water structure confined in ionic liquids using H/D exchange

Yoshimura, Yukihiro; Mori, Takahiro; Kaneko, Kazuyoshi; Nogami, Koji; Takekiyo, Takahiro; Masuda, Yuichi; Shimizu, Akio

doi:10.1016/j.molliq.2019.04.151

Cited by 28 publications

(24 citation statements)

References 51 publications

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“…The water nanostructure within IL/water mixtures changes markedly with increasing water content and the nature of these changes depends on the hydrophilicity of the IL. In analogy with prior spectroscopic [52,56] and NMR studies [66,67,71], qualitative structural features can be inferred by characterizing water dynamics; here we focus on the water rotational correlation timescales. In Figure S1, we show rotational correlation functions of water molecules within the five different IL/water mixtures at varying water content.…”

Section: Resultsmentioning

confidence: 99%

“…This question has been stated in recent work simply as whether "water molecules in IL matrices (are) dispersed or does a water pool form?" [71]. We note that experimental characterization of changes in transport properties (e.g., conductivity, viscosity) of ILs with water content can provide clues about internal water structure [23,27,47,[75][76][77][78] but such analysis is indirect and requires care [79].…”

Section: Introductionmentioning

confidence: 99%

“…Experimental spectroscopy [25,[48][49][50][51][52][53][54][55][56][57], small angle X-ray or neutron diffraction (SAXS/SANS) [58][59][60][61][62][63][64][65], and nuclear magnetic resonance (NMR) studies [66][67][68][69][70][71] have revealed a wealth of information on the structural and dynamic properties of IL/water mixtures. We restrict such synopsis to ILs composed of shorter chain cations similar to BMIM + ; it is well-documented that ILs composed of longer chain cations form micelles, reverse micelles or self-assemble when mixed with water [53,58,60,[72][73][74] but this surfactant-like regime is not our focus.…”

Section: Introductionmentioning

confidence: 99%

“…Structural heterogeneity and microscopic domain formation occurs in hydrophobic IL/water mixtures, as indicated for BMIM + /bis(trifluoromethylsulfonyl)imide ([BMIM + ][TFSI − ]) based on NMR measurements [66]. There exists disagreement, however, on the lengthscale of such water pockets or confined microdomains within ILs; some studies report lengthscales on the order of several nanometers [61], while other studies suggest that domains are formed from fewer than ∼5 water molecules [71]. This question has been stated in recent work simply as whether "water molecules in IL matrices (are) dispersed or does a water pool form?"…”

Section: Introductionmentioning

confidence: 99%

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Tuning Water Networks via Ionic Liquid/Water Mixtures

Verma

Stoppelman

McDaniel

2020

IJMS

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Water in nanoconfinement is ubiquitous in biological systems and membrane materials, with altered properties that significantly influence the surrounding system. In this work, we show how ionic liquid (IL)/water mixtures can be tuned to create water environments that resemble nanoconfined systems. We utilize molecular dynamics simulations employing ab initio force fields to extensively characterize the water structure within five different IL/water mixtures: [BMIM + ][BF 4 − ], [BMIM + ][PF 6 − ], [BMIM + ][OTf − ], [BMIM + ][NO 3 − ] and [BMIM + ][TFSI − ] ILs at varying water fraction. We characterize water clustering, hydrogen bonding, water orientation, pairwise correlation functions and percolation networks as a function of water content and IL type. The nature of the water nanostructure is significantly tuned by changing the hydrophobicity of the IL and sensitively depends on water content. In hydrophobic ILs such as [BMIM + ][PF 6 − ], significant water clustering leads to dynamic formation of water pockets that can appear similar to those formed within reverse micelles. Furthermore, rotational relaxation times of water molecules in supersaturated hydrophobic IL/water mixtures indicate the close-connection with nanoconfined systems, as they are quantitatively similar to water relaxation in previously characterized lyotropic liquid crystals. We expect that this physical insight will lead to better design principles for incorporation of ILs into membrane materials to tune water nanostructure.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Tuning Water Networks via Ionic Liquid/Water Mixtures

Verma

Stoppelman

McDaniel

2020

IJMS

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“…As seen by the examples discussed above, the question of how the addition of water correlates to the structural modifications is very complex and instigates a heated scientific debate. Even very recently, two papers, Verma et al [ 133 ] using MD simulations with ab-initio force fields, and Yoshimura et al [ 142 ] using NMR and Raman spectroscopy, formulated a new model for [C 4 mim][BF 4 ]/water systems at low water content. Both works maintained the idea that at low water content the water is “trapped” inside the IL network, with small water clusters characterized by water molecules with three or four hydrogen bonds per molecule, indicating that local structure approaches bulk water like coordination environment.…”

Section: Water Effectmentioning

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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Formation of α‐synuclein aggregates in aqueous ethylammonium nitrate solutions

et al. 2020

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The effect of adding ethylammonium nitrate (EAN), which is an ionic liquid (IL), on the aggregate formation of α‐synuclein (α‐Syn) in aqueous solution has been investigated. FTIR and Raman spectroscopy were used to investigate changes in the secondary structure of α‐Syn and in the states of water molecules and EAN. The results presented here show that the addition of EAN to α‐Syn causes the formation of an intermolecular β‐sheet structure in the following manner: native disordered state → polyproline II (PPII)‐helix → intermolecular β‐sheet (α‐Syn amyloid‐like aggregates: α‐SynA). Although cations and anions of EAN play roles in masking the charged side chains and PPII‐helix‐forming ability involved in the formation of α‐SynA, water molecules are not directly related to its formation. We conclude that EAN‐induced α‐Syn amyloid‐like aggregates form at hydrophobic associations in the middle of the molecules after masking the charged side chains at the N‐ and C‐terminals of α‐Syn.

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Confirmation of local water structure confined in ionic liquids using H/D exchange

Cited by 28 publications

References 51 publications

Tuning Water Networks via Ionic Liquid/Water Mixtures

Tuning Water Networks via Ionic Liquid/Water Mixtures

Revisiting Ionic Liquid Structure-Property Relationship: A Critical Analysis

Formation of α‐synuclein aggregates in aqueous ethylammonium nitrate solutions

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