Nuclear magnetic resonance study of the dynamics of imidazolium ionic liquids with -CH2Si(CH3)3 vs -CH 2C(CH3)3 substituents

Song H. Chung, Richard Lopato, Steven G. Greenbaum, Hideaki Shirota, Ed Castner, James F. Wishart

Research output: Contribution to journalArticle

89 Citations (Scopus)

Abstract

Trimethylsilylmethyl (TMSiM)-substituted imidazolium bis(trifluoromethylsulfonyl)imide (NTf2 -), and tetrafluoroborate (BF4 -) ionic liquids (ILs) have lower room-temperature viscosities by factors of 1.6 and 7.4, respectively, than isostructural neopentylimidazolium ILs. In an attempt to account for the effects of silicon substitution in imidazolium RTILs and to investigate the ion dynamics, we report nuclear magnetic resonance (NMR) measurements of 1H (I = 1/2) and 19F (I = 1/2) spin-lattice relaxation times (T1) and self-diffusion coefficients (D) as a function of temperature for ILs containing the TMSiM group and, for comparison, the analogous neopentyl group. The 1H and 19F nuclei probe the dynamics of the cations and anions, respectively. The low-temperature line shapes were determined to be Gaussian, and the onset of the rigid lattice line width is correlated with the measured glass transition temperature. The spin-lattice relaxation data feature a broad T1 minimum as a function of inverse temperature for both nuclear species. The Arrhenius plots of the diffusion data for both nuclear species are found to exhibit Vogel-Tammann-Fulcher curvature. Analysis of the η and D data generally show fractional Stokes-Einstein behavior D ∝ (T/η)m. This is most prominent in the neopentylimidazolium BF4 - IL with m ≈ 0.66.

Original languageEnglish
Pages (from-to)4885-4893
Number of pages9
JournalJournal of Physical Chemistry B
Volume111
Issue number18
DOIs
Publication statusPublished - May 10 2007

Fingerprint

Ionic Liquids
Ionic liquids
Nuclear magnetic resonance
methylidyne
nuclear magnetic resonance
Spin-lattice relaxation
liquids
spin-lattice relaxation
Magnetic resonance measurement
Imides
Arrhenius plots
Temperature
imides
Silicon
Linewidth
Relaxation time
glass transition temperature
Anions
line shape
Cations

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Nuclear magnetic resonance study of the dynamics of imidazolium ionic liquids with -CH2Si(CH3)3 vs -CH 2C(CH3)3 substituents. / Chung, Song H.; Lopato, Richard; Greenbaum, Steven G.; Shirota, Hideaki; Castner, Ed; Wishart, James F.

In: Journal of Physical Chemistry B, Vol. 111, No. 18, 10.05.2007, p. 4885-4893.

Research output: Contribution to journalArticle

Chung, Song H. ; Lopato, Richard ; Greenbaum, Steven G. ; Shirota, Hideaki ; Castner, Ed ; Wishart, James F. / Nuclear magnetic resonance study of the dynamics of imidazolium ionic liquids with -CH2Si(CH3)3 vs -CH 2C(CH3)3 substituents. In: Journal of Physical Chemistry B. 2007 ; Vol. 111, No. 18. pp. 4885-4893.
@article{13bde0ea4af147e0b356b2a29d0f5ce8,
title = "Nuclear magnetic resonance study of the dynamics of imidazolium ionic liquids with -CH2Si(CH3)3 vs -CH 2C(CH3)3 substituents",
abstract = "Trimethylsilylmethyl (TMSiM)-substituted imidazolium bis(trifluoromethylsulfonyl)imide (NTf2 -), and tetrafluoroborate (BF4 -) ionic liquids (ILs) have lower room-temperature viscosities by factors of 1.6 and 7.4, respectively, than isostructural neopentylimidazolium ILs. In an attempt to account for the effects of silicon substitution in imidazolium RTILs and to investigate the ion dynamics, we report nuclear magnetic resonance (NMR) measurements of 1H (I = 1/2) and 19F (I = 1/2) spin-lattice relaxation times (T1) and self-diffusion coefficients (D) as a function of temperature for ILs containing the TMSiM group and, for comparison, the analogous neopentyl group. The 1H and 19F nuclei probe the dynamics of the cations and anions, respectively. The low-temperature line shapes were determined to be Gaussian, and the onset of the rigid lattice line width is correlated with the measured glass transition temperature. The spin-lattice relaxation data feature a broad T1 minimum as a function of inverse temperature for both nuclear species. The Arrhenius plots of the diffusion data for both nuclear species are found to exhibit Vogel-Tammann-Fulcher curvature. Analysis of the η and D data generally show fractional Stokes-Einstein behavior D ∝ (T/η)m. This is most prominent in the neopentylimidazolium BF4 - IL with m ≈ 0.66.",
author = "Chung, {Song H.} and Richard Lopato and Greenbaum, {Steven G.} and Hideaki Shirota and Ed Castner and Wishart, {James F.}",
year = "2007",
month = "5",
day = "10",
doi = "10.1021/jp071755w",
language = "English",
volume = "111",
pages = "4885--4893",
journal = "Journal of Physical Chemistry B Materials",
issn = "1520-6106",
publisher = "American Chemical Society",
number = "18",

}

TY - JOUR

T1 - Nuclear magnetic resonance study of the dynamics of imidazolium ionic liquids with -CH2Si(CH3)3 vs -CH 2C(CH3)3 substituents

AU - Chung, Song H.

AU - Lopato, Richard

AU - Greenbaum, Steven G.

AU - Shirota, Hideaki

AU - Castner, Ed

AU - Wishart, James F.

PY - 2007/5/10

Y1 - 2007/5/10

N2 - Trimethylsilylmethyl (TMSiM)-substituted imidazolium bis(trifluoromethylsulfonyl)imide (NTf2 -), and tetrafluoroborate (BF4 -) ionic liquids (ILs) have lower room-temperature viscosities by factors of 1.6 and 7.4, respectively, than isostructural neopentylimidazolium ILs. In an attempt to account for the effects of silicon substitution in imidazolium RTILs and to investigate the ion dynamics, we report nuclear magnetic resonance (NMR) measurements of 1H (I = 1/2) and 19F (I = 1/2) spin-lattice relaxation times (T1) and self-diffusion coefficients (D) as a function of temperature for ILs containing the TMSiM group and, for comparison, the analogous neopentyl group. The 1H and 19F nuclei probe the dynamics of the cations and anions, respectively. The low-temperature line shapes were determined to be Gaussian, and the onset of the rigid lattice line width is correlated with the measured glass transition temperature. The spin-lattice relaxation data feature a broad T1 minimum as a function of inverse temperature for both nuclear species. The Arrhenius plots of the diffusion data for both nuclear species are found to exhibit Vogel-Tammann-Fulcher curvature. Analysis of the η and D data generally show fractional Stokes-Einstein behavior D ∝ (T/η)m. This is most prominent in the neopentylimidazolium BF4 - IL with m ≈ 0.66.

AB - Trimethylsilylmethyl (TMSiM)-substituted imidazolium bis(trifluoromethylsulfonyl)imide (NTf2 -), and tetrafluoroborate (BF4 -) ionic liquids (ILs) have lower room-temperature viscosities by factors of 1.6 and 7.4, respectively, than isostructural neopentylimidazolium ILs. In an attempt to account for the effects of silicon substitution in imidazolium RTILs and to investigate the ion dynamics, we report nuclear magnetic resonance (NMR) measurements of 1H (I = 1/2) and 19F (I = 1/2) spin-lattice relaxation times (T1) and self-diffusion coefficients (D) as a function of temperature for ILs containing the TMSiM group and, for comparison, the analogous neopentyl group. The 1H and 19F nuclei probe the dynamics of the cations and anions, respectively. The low-temperature line shapes were determined to be Gaussian, and the onset of the rigid lattice line width is correlated with the measured glass transition temperature. The spin-lattice relaxation data feature a broad T1 minimum as a function of inverse temperature for both nuclear species. The Arrhenius plots of the diffusion data for both nuclear species are found to exhibit Vogel-Tammann-Fulcher curvature. Analysis of the η and D data generally show fractional Stokes-Einstein behavior D ∝ (T/η)m. This is most prominent in the neopentylimidazolium BF4 - IL with m ≈ 0.66.

UR - http://www.scopus.com/inward/record.url?scp=34249748928&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34249748928&partnerID=8YFLogxK

U2 - 10.1021/jp071755w

DO - 10.1021/jp071755w

M3 - Article

C2 - 17441766

AN - SCOPUS:34249748928

VL - 111

SP - 4885

EP - 4893

JO - Journal of Physical Chemistry B Materials

JF - Journal of Physical Chemistry B Materials

SN - 1520-6106

IS - 18

ER -