Solute rotation and solvation dynamics in a room-temperature ionic liquid

J. A. Ingram, R. S. Moog, N. Ito, R. Biswas, Mark Maroncelli

Research output: Contribution to journalArticle

284 Citations (Scopus)

Abstract

Steady-state spectra, rotation times, and time-resolved emission spectra of the probe 4-aminophthalimide (4-AP) in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6-]) were measured over the temperature range 298-355 K. The steady-state spectroscopy indicates that the solvation energetics of 4-AP in [bmim+][PF6-] are comparable to those of 4-AP in highly polar but aprotic solvents such as dimethylformamide and acetonitrile (π* ∼ 0.8, ETN ∼ 0.4). The rotation of 4-AP in [bmim+][PF6-] and in more conventional aprotic solvents generally conforms to the expectations of simple hydrodynamic models. Other than the fact that [bmim+][PF6-] is highly viscous, nothing distinguishes the rotation of 4-AP in this ionic liquid from its rotation in more conventional polar aprotic solvents. Time-dependent emission spectra, recorded with an instrumental response of 25 ps, indicate that solvation dynamics in [bmim+][PF6-] occur in two well-separated time regimes. Near to room temperature, the observable response takes place in the 0.1-2 ns time range. This component can be described by a stretched exponential time dependence with an exponent of 0.6-0.7, indicative of strongly nonexponential relaxation. The integral time of the observed component of solvation is proportional to the rotation time of 4-AP and to solvent viscosity, suggesting the involvement of substantial solvent rearrangement. In addition to this relatively slow component, more than half of the solvation response in [bmim+][PF6-] is faster than can be detected in these experiments, that is, takes place in <5 ps.

Original languageEnglish (US)
Pages (from-to)5926-5932
Number of pages7
JournalJournal of Physical Chemistry B
Volume107
Issue number24
StatePublished - Jun 19 2003

Fingerprint

Ionic Liquids
Solvation
Ionic liquids
solvation
solutes
room temperature
liquids
Temperature
emission spectra
Dimethylformamide
Acetonitrile
Hydrodynamics
4-aminophthalimide
1-butyl-3-methylimidazolium hexafluorophosphate
Spectroscopy
Viscosity
time dependence
acetonitrile
hydrodynamics
exponents

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Ingram, J. A. ; Moog, R. S. ; Ito, N. ; Biswas, R. ; Maroncelli, Mark. / Solute rotation and solvation dynamics in a room-temperature ionic liquid. In: Journal of Physical Chemistry B. 2003 ; Vol. 107, No. 24. pp. 5926-5932.
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abstract = "Steady-state spectra, rotation times, and time-resolved emission spectra of the probe 4-aminophthalimide (4-AP) in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6-]) were measured over the temperature range 298-355 K. The steady-state spectroscopy indicates that the solvation energetics of 4-AP in [bmim+][PF6-] are comparable to those of 4-AP in highly polar but aprotic solvents such as dimethylformamide and acetonitrile (π* ∼ 0.8, ETN ∼ 0.4). The rotation of 4-AP in [bmim+][PF6-] and in more conventional aprotic solvents generally conforms to the expectations of simple hydrodynamic models. Other than the fact that [bmim+][PF6-] is highly viscous, nothing distinguishes the rotation of 4-AP in this ionic liquid from its rotation in more conventional polar aprotic solvents. Time-dependent emission spectra, recorded with an instrumental response of 25 ps, indicate that solvation dynamics in [bmim+][PF6-] occur in two well-separated time regimes. Near to room temperature, the observable response takes place in the 0.1-2 ns time range. This component can be described by a stretched exponential time dependence with an exponent of 0.6-0.7, indicative of strongly nonexponential relaxation. The integral time of the observed component of solvation is proportional to the rotation time of 4-AP and to solvent viscosity, suggesting the involvement of substantial solvent rearrangement. In addition to this relatively slow component, more than half of the solvation response in [bmim+][PF6-] is faster than can be detected in these experiments, that is, takes place in <5 ps.",
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Ingram, JA, Moog, RS, Ito, N, Biswas, R & Maroncelli, M 2003, 'Solute rotation and solvation dynamics in a room-temperature ionic liquid', Journal of Physical Chemistry B, vol. 107, no. 24, pp. 5926-5932.

Solute rotation and solvation dynamics in a room-temperature ionic liquid. / Ingram, J. A.; Moog, R. S.; Ito, N.; Biswas, R.; Maroncelli, Mark.

In: Journal of Physical Chemistry B, Vol. 107, No. 24, 19.06.2003, p. 5926-5932.

Research output: Contribution to journalArticle

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T1 - Solute rotation and solvation dynamics in a room-temperature ionic liquid

AU - Ingram, J. A.

AU - Moog, R. S.

AU - Ito, N.

AU - Biswas, R.

AU - Maroncelli, Mark

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N2 - Steady-state spectra, rotation times, and time-resolved emission spectra of the probe 4-aminophthalimide (4-AP) in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim+][PF6-]) were measured over the temperature range 298-355 K. The steady-state spectroscopy indicates that the solvation energetics of 4-AP in [bmim+][PF6-] are comparable to those of 4-AP in highly polar but aprotic solvents such as dimethylformamide and acetonitrile (π* ∼ 0.8, ETN ∼ 0.4). The rotation of 4-AP in [bmim+][PF6-] and in more conventional aprotic solvents generally conforms to the expectations of simple hydrodynamic models. Other than the fact that [bmim+][PF6-] is highly viscous, nothing distinguishes the rotation of 4-AP in this ionic liquid from its rotation in more conventional polar aprotic solvents. Time-dependent emission spectra, recorded with an instrumental response of 25 ps, indicate that solvation dynamics in [bmim+][PF6-] occur in two well-separated time regimes. Near to room temperature, the observable response takes place in the 0.1-2 ns time range. This component can be described by a stretched exponential time dependence with an exponent of 0.6-0.7, indicative of strongly nonexponential relaxation. The integral time of the observed component of solvation is proportional to the rotation time of 4-AP and to solvent viscosity, suggesting the involvement of substantial solvent rearrangement. In addition to this relatively slow component, more than half of the solvation response in [bmim+][PF6-] is faster than can be detected in these experiments, that is, takes place in <5 ps.

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