Ion pair and solvation dynamics of [Bmim][BF4] + water system

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

In this work, 1-butyl-3-methylimidazolium tetrafluoroborate/water mixtures were analysed over the whole water composition (xw) in order to study the rotational and translational behaviour of the ions. We employed a multinuclear NMR approach to determine anion/cation/water diffusion coefficients and longitudinal relaxation rates at different water content. In neat ionic liquids (IL), the cation diffuses faster than the anion, and at low xw, anions and cations share almost the same diffusion coefficient, but above a critical water concentration, the anion begins to diffuse faster than the cation. We identified this composition as approximately 10% xw where the ions share the same diffusion coefficient. We found that the water at this composition seems to have a much more dramatic effect in the rotational diffusion of the anion that decreases substantially and approaches that of the anion in the diluted IL. Translational and rotational dynamics of the ions suggest that water is first incorporated in pockets in the nanostructure of the IL allowing the ions to maintain most of the cation/anion interactions present in neat IL but already disrupting some anion/cation interactions due to preferential interaction with the anion. HOESY and NOESY data show that water displays contacts both with the cation and the anion in a positive NOE regime in contrary to the negative regime found for the cation/anion and cation/cation cross-relaxation. This is in accordance with the high relative diffusion coefficient of water and suggests that water molecules can exchange between preferential location sites that allow water to maintain contacts both with the anion and cation.

Original languageEnglish
Pages (from-to)127-139
Number of pages13
JournalMagnetic Resonance in Chemistry
Volume56
Issue number2(SI)
DOIs
Publication statusPublished - 1 Feb 2018

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Solvation
Anions
Cations
Negative ions
Ions
Positive ions
Water
Ionic Liquids
Ionic liquids
Chemical analysis
Water content
Nanostructures
Display devices
Nuclear magnetic resonance

Keywords

  • ion pair
  • ionic liquids
  • relaxation times
  • translational and rotational diffusion

Cite this

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title = "Ion pair and solvation dynamics of [Bmim][BF4] + water system",
abstract = "In this work, 1-butyl-3-methylimidazolium tetrafluoroborate/water mixtures were analysed over the whole water composition (xw) in order to study the rotational and translational behaviour of the ions. We employed a multinuclear NMR approach to determine anion/cation/water diffusion coefficients and longitudinal relaxation rates at different water content. In neat ionic liquids (IL), the cation diffuses faster than the anion, and at low xw, anions and cations share almost the same diffusion coefficient, but above a critical water concentration, the anion begins to diffuse faster than the cation. We identified this composition as approximately 10{\%} xw where the ions share the same diffusion coefficient. We found that the water at this composition seems to have a much more dramatic effect in the rotational diffusion of the anion that decreases substantially and approaches that of the anion in the diluted IL. Translational and rotational dynamics of the ions suggest that water is first incorporated in pockets in the nanostructure of the IL allowing the ions to maintain most of the cation/anion interactions present in neat IL but already disrupting some anion/cation interactions due to preferential interaction with the anion. HOESY and NOESY data show that water displays contacts both with the cation and the anion in a positive NOE regime in contrary to the negative regime found for the cation/anion and cation/cation cross-relaxation. This is in accordance with the high relative diffusion coefficient of water and suggests that water molecules can exchange between preferential location sites that allow water to maintain contacts both with the anion and cation.",
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author = "Jo{\~a}o Casc{\~a}o and Wagner Silva and Ferreira, {Ana S. D.} and Cabrita, {Eurico J.}",
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Ion pair and solvation dynamics of [Bmim][BF4] + water system. / Cascão, João; Silva, Wagner; Ferreira, Ana S. D.; Cabrita, Eurico J.

In: Magnetic Resonance in Chemistry, Vol. 56, No. 2(SI), 01.02.2018, p. 127-139.

Research output: Contribution to journalArticle

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AU - Cascão, João

AU - Silva, Wagner

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AU - Cabrita, Eurico J.

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