Ultrafast Dynamics in Aprotic Molecular Liquids: A Femtosecond Raman-Induced Kerr Effect Spectroscopic Study

Shirota, Hideaki; Fujisawa, Tomotsumi; Fukazawa, Hiroki; Nishikawa, Keiko

doi:10.1246/bcsj.82.1347

Cited by 77 publications

(242 citation statements)

References 121 publications

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“…62,63 has been conducted in the same manner as previously reported by our group. 18,21 Figure 4 shows the Fourier transform Kerr spectra obtained from the Kerr transients with and without the wide-time-window Kerr transient for […”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence of Low-Frequency Spectra in Molten Bis(trifluoromethylsulfonyl)amide Salts of Imidazolium Cations Studied by Femtosecond Raman-Induced Kerr Effect Spectroscopy

Shirota

Kakinuma

2015

J. Phys. Chem. B

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In this study, the temperature dependence of the low-frequency spectra of liquid bis(trifluoromethylsulfonyl)amide salts of the monocations 1-methyl-3-propylimidazolium and 1-hexyl-3-methylimidazolium and the dications 1,6-bis(3-methylimidazolium-1-yl)hexane and 1,12-bis(3-methylimidazolium-1-yl)dodecane has been investigated by means of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The intensity in the low-frequency region below 20 cm(-1) in the spectra of the four ionic liquids increases with rising temperature. From a line-shape analysis of the broadened low-frequency spectra of the ionic liquids, it is clear that the lowest-frequency component, which peaks at approximately 5 cm(-1), contributes to the temperature dependence of the spectra. This implies that the activity of the intermolecular translational vibrational motion is increasing with rising temperature. It is also possible that decoupling in the crossover process between intermolecular vibrational motion and structural relaxation occurs as a result of a deterioration of the non-Markovian feature or the loss of memory caused by the higher temperature. The peak of the highest-frequency component, which is due mainly to the imidazolium ring libration, shifts to lower frequency with increasing temperature. This is attributed to weaker interactions of the ionic liquids at higher temperatures. Temperature-dependent viscosities from 293 to 353 K of the four ionic liquids have also been characterized.

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Section: Resultsmentioning

confidence: 99%

Temperature Dependence of Low-Frequency Spectra in Molten Bis(trifluoromethylsulfonyl)amide Salts of Imidazolium Cations Studied by Femtosecond Raman-Induced Kerr Effect Spectroscopy

Shirota

Kakinuma

2015

J. Phys. Chem. B

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“…Such high frequency dynamics have been characterised in optical Kerr effect (OKE) studies for numerous pure liquids, including the specific solvents used here. [26][27][28][29] The physical origin of this fast response is the non-diffusive librational motion of the molecule in a cage of its neighbours. 30 The role of this contribution is further corroborated by the Gaussian relaxation measured at early times, which is typical of librational dynamics observed in OKE and photon echo studies.…”

Section: B) 2des Reshapingmentioning

confidence: 99%

Two-Dimensional Electronic Spectroscopy of Chlorophyll a: Solvent Dependent Spectral Evolution

2015

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The interaction of the monomeric chlorophyll Q band electronic transition with solvents of differing physical-chemical properties is investigated through two-dimensional electronic spectroscopy (2DES). Chlorophyll constitutes the key chromophore molecule in light harvesting complexes. It is well known that the surrounding protein in the light harvesting complex fine tunes chlorophyll electronic transitions to optimize energy transfer. Therefore an understanding of the influence of the environment on the monomeric chlorophyll electronic transitions is important. The Q band 2DES are inhomogeneous at early times, particularly in hydrogen bonding polar solvents, but also in nonpolar solvents like cyclohexane. Interestingly this inhomogeneity persists for long times, even up to the nanosecond timescale in some solvents. The reshaping of the 2DES occurs over multiple timescales and was assigned mainly to spectral diffusion. At early times the reshaping is Gaussianlike, hinting at a strong solvent reorganization effect. The temporal evolution of the 2DES response was analysed in terms of a Brownian oscillator model. The spectral densities underpinning the Brownian oscillator fitting were recovered for the different solvents. The absorption spectra and Stokes shift were also properly described by this model. The extent and nature of inhomogeneous broadening was a strong function of solvent, being larger in H-bonding and viscous media and smaller in nonpolar solvents. The fastest spectral reshaping components were assigned to solvent dynamics, modified by interactions with the solute.

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“…46 Recently, the low-frequency Kerr spectra of 20 aromatic molecular liquids and 20 nonaromatic molecular liquids have been measured and discussed holistically. 19 The line shape of the low-frequency Kerr spectrum for aromatic molecular liquids, except for perfluorinated benzene, is generally bimodal, while that for nonaromatic molecular liquids is variable.…”

Section: Introductionmentioning

confidence: 99%

Effects of Aromaticity in Cations and Their Functional Groups on the Low-Frequency Spectra and Physical Properties of Ionic Liquids

Shirota¹,

Matsuzaki²,

Ramati

et al. 2014

J. Phys. Chem. B

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We have critically investigated the low-frequency spectra of six ionic liquids (ILs) consisting of systematically different cations having benzyl moieties or comparable-sized saturated cyclohexylmethyl groups, by means of femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES). The target ionic liquids are bis(trifluoromethylsulfonyl)amide ([NTf2](-)) salts of the 1-benzyl-3-methylimidazolium ([BzMIm](+)), 1-benzyl-1-methylpyrrolidinium ([BzMPyrr](+)), 1-benzylpyridinium ([BzPy](+)), 1-cyclohexylmethyl-3-methylimidazolium ([CHxmMIm](+)), 1-cyclohexylmethyl-1-methylpyrrolidinium ([CHxmMPyrr](+)), and 1-cyclohexylmethylpyridinium ([CHxmPy](+)) cations. The primary purpose of this study is to clarify the effects of charged and neutral aromatic moieties on the low-frequency spectrum and bulk properties such as liquid density, surface tension, shear viscosity, glass transition temperature, and melting point. We found that ILs with benzyl groups have larger surface tensions than those with the same cation bearing the cyclohexylmethyl group. The trend in the glass transition temperatures, comparing ILs having the same side group, is pyridinium > imidazolium > pyrrolidinium. The effects of a single aromatic moiety on the shear viscosity are inconclusive, although the viscosities of the ILs with aromatic moieties on both the cation and the benzyl group, i.e., [BzMIm][NTf2] and [BzPy][NTf2], are substantially lower than those of the other ILs at room temperature, as a consequence of their higher fragilities. In the low-frequency Kerr spectra in the frequency range of approximately 0.1 to 200 cm(-1) measured by fs-RIKES, the ILs possessing two aromatic groups show the largest relative intensity of the nuclear response to the electronic response. Both the charged and neutral aromatic rings show signals due to the ring libration; the neutral one appears at a lower frequency than the charged one. The relationship between the first moment of the broad low-frequency spectrum band and the bulk parameter consisting of the square root of the surface tension divided by the liquid density is obeyed by the cyclohexylmethyl derivatives whether the cation is aromatic or not, but not by the ILs with the neutral aromatic benzyl group. Quantum chemistry calculations have been also performed to understand the vibrational modes of the ionic species in the ILs.

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Ultrafast Dynamics in Aprotic Molecular Liquids: A Femtosecond Raman-Induced Kerr Effect Spectroscopic Study

Cited by 77 publications

References 121 publications

Temperature Dependence of Low-Frequency Spectra in Molten Bis(trifluoromethylsulfonyl)amide Salts of Imidazolium Cations Studied by Femtosecond Raman-Induced Kerr Effect Spectroscopy

Temperature Dependence of Low-Frequency Spectra in Molten Bis(trifluoromethylsulfonyl)amide Salts of Imidazolium Cations Studied by Femtosecond Raman-Induced Kerr Effect Spectroscopy

Two-Dimensional Electronic Spectroscopy of Chlorophyll a: Solvent Dependent Spectral Evolution

Effects of Aromaticity in Cations and Their Functional Groups on the Low-Frequency Spectra and Physical Properties of Ionic Liquids

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