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Koyakkat M, Ishida T, Fujita K, Shirota H. Low-Frequency Spectra of Hydrated Ionic Liquids with Kosmotropic and Chaotropic Anions. J Phys Chem B 2024; 128:4171-4182. [PMID: 38640467 DOI: 10.1021/acs.jpcb.4c01255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2024]
Abstract
In this study, we investigated the water concentration dependence of the intermolecular vibrations of two hydrated ionic liquids (ILs), cholinium dihydrogen phosphate ([ch][dhp]) and cholinium bromide ([ch]Br), using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES). The anions of the former and latter hydrated ILs are kosmotropic and chaotropic, respectively. We found that the spectral peak of ∼50 cm-1 shifted to the low-frequency side in hydrated [ch][dhp], indicating the weakening of its intermolecular interactions. In contrast, no change in the peak frequency of the low-frequency band at ∼50 cm-1 was observed with increasing water concentration in hydrated [ch]Br. The vibrational density of states (VDOS) spectra generated from molecular dynamics (MD) simulations were in qualitative agreement with the experimental results. Decomposition analysis of the VDOS spectra for each component revealed that the red shift of the low-frequency band in the hydrated [ch][dhp] upon water addition was essentially due to the contributions of anions and water rather than that of the cholinium cation. We also found from the low-frequency spectra of the two hydrated ILs that they differed in the concentration dependence of the 180 cm-1 band, which is assigned as a hindered translational motion of water molecules combined to form O···O stretching motions. From the relationship between the peak frequency of the low-frequency band and the bulk parameter, which is the square root of the surface tension divided by the density, we found that the peak frequency in the hydrated IL with kosmotropic [dhp]- depends on the bulk parameter, similar to the case for an aqueous solution of the typical deep eutectic solvent reline. However, the peak frequency of the hydrated IL with chaotropic Br- is constant with the bulk parameter.
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Affiliation(s)
- Maharoof Koyakkat
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Tateki Ishida
- Institute for Molecular Science and Research Center for Computational Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Kyoko Fujita
- Department of Pathophysiology, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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2
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Shirota H, Rajbangshi J, Koyakkat M, Baksi A, Cao M, Biswas R. Low-frequency spectra of reline and its mixtures with water: A comparative study based on femtosecond Raman-induced Kerr effect spectroscopy and molecular dynamics simulations. J Photochem Photobiol A Chem 2023. [DOI: 10.1016/j.jphotochem.2022.114504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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3
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Shimizu M, Shirota H. Intermolecular Dynamics of Positively and Negatively Charged Aromatics and Their Isoelectronic Neutral Analogs in Aqueous Solutions. J Phys Chem B 2022; 126:4309-4323. [PMID: 35658126 DOI: 10.1021/acs.jpcb.2c01517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we investigated the temperature dependence of intermolecular vibrations and orientational dynamics in the aqueous solutions of imidazole hydrochloride, imidazole, sodium triazolide, and triazole using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) and steady-state Raman spectroscopy. The difference low-frequency Raman spectra under 250 cm-1 of the aqueous solutions relative to the neat water showed that the spectral shoulder in the high-frequency region at 60-100 cm-1, assigned to the libration of an aromatic ring, was higher in frequency for the imidazolium cation but lower for the triazolide anion than those of the respective neutral aromatics. The results of the ab initio quantum chemistry calculations of the clusters of the aromatics and water molecule(s) were consistent with the experimental spectra of the aqueous solutions. Further, the results of the temperature-dependent experiments showed that the signal intensity in the low-frequency region below 50 cm-1 increased for all solutions with an increase in temperature. In contrast, the spectral density in the high-frequency region above 80 cm-1 exhibited almost no shift for the 1.0 M solutions, while a significant red shift was observed for the 5.0 M solutions. In addition, the temperature-dependent densities, viscosities, and surface tensions were characterized for the aqueous aromatic solutions from 293 to 353 K.
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Affiliation(s)
- Masako Shimizu
- Department of Chemistry, Chiba University 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Ando M, Shirota H. Low-Frequency Spectra of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Poly(ethylene glycol) by Femtosecond Raman-Induced Kerr Effect Spectroscopy. J Phys Chem B 2021; 125:12006-12019. [PMID: 34694116 DOI: 10.1021/acs.jpcb.1c07079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This is the first report on low-frequency spectra of ionic liquid (IL)/polymer mixtures using femtosecond Raman-induced Kerr effect spectroscopy. We studied mixtures of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) and poly(ethylene glycol) (PEG) with Mn = 400 (PEG400) at various concentrations. To elucidate the unique features of the IL/polymer mixture system, mixtures of PEG400 with a molecular liquid, 1-octhylimidazole (OIm), which is a neutral analog of the cation, were also studied. In addition, mixtures of [MOIm][BF4] with ethylene glycol (EG) and poly(ethylene glycol) with Mn = 4000 (PEG4000) were also investigated. The first moments of broad low-frequency spectra, mainly due to intermolecular vibrations for the [MOIm][BF4]/PEG400 and OIm/PEG400, increased slightly with increasing concentration of PEG400, indicating that microscopic intermolecular interactions, in general, are slightly enhanced. We also compared the [MOIm][BF4] mixtures with EG, PEG400, and PEG4000 at concentrations of 5 and 10 wt % PEG or EG. The low-frequency spectra of samples with the same concentrations were quite similar, but a comparison of the normalized spectra showed that the spectral intensity in the low-frequency region below ∼50 cm-1 of the [MOIm][BF4] mixtures with PEG400 and PEG4000 is somewhat lower than that of the [MOIm][BF4] mixtures with EG. Although the effect of the polymer is small compared to other polymer solution systems, this feature is attributed to a suppression of translational motion in the mixtures of [MOIm][BF4] with PEG compared to the mixtures of [MOIm][BF4] with EG due to the greater mass of PEG than EG. Density, surface tension, viscosity, and electrical conductivity were also estimated. From Walden plots, it was found that the [MOIm][BF4]/PEG4000 system showed more ideal electrical conductive behavior than the [MOIm][BF4]/PEG400 and [MOIm][BF4]/EG systems.
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Affiliation(s)
- Masatoshi Ando
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Meng D, Sagala S, Aquino AJ, Quitevis EL. Orientational and low-frequency (0–450 cm−1) dynamics of methyl methacrylate: OHD-RIKES measurements and DFT calculations. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2020.115004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Shirota H, Moriyama K. Low-Frequency Vibrational Motions of Polystyrene in Carbon Tetrachloride: Comparison with Model Monomer and Dependence on Concentration and Molecular Weight. J Phys Chem B 2020; 124:2006-2016. [PMID: 32073847 DOI: 10.1021/acs.jpcb.9b10672] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this study, the low-frequency vibrational dynamics of polystyrene (PS) in CCl4 was investigated by femtosecond Raman-induced Kerr effect spectroscopy. Ethylbenzene (EBz) was also investigated as a model monomer of the polymer to elucidate the unique dynamical features of PS in solution. The broadened low-frequency spectrum of the PS/CCl4 in the frequency region below 150 cm-1 is significantly different from that of the EBz/CCl4. Difference spectra between the PS or EBz solutions and neat CCl4, normalized to an internal vibrational mode of CCl4, clearly show a much lower spectral intensity for the PS/CCl4 than the EBz/CCl4 in the low-frequency region below ca. 20 cm-1. This indicates that translational motions are suppressed in the PS/CCl4 compared to the EBz/CCl4. Moreover, the high-frequency motion at ca. 70 cm-1, mainly due to phenyl ring librations, occurs at higher frequency in PS (78 cm-1) than EBz (65 cm-1). In addition, the results of concentration-dependent experiments show that the first moment (M1) of the low-frequency difference spectra of both PS/CCl4 and EBz/CCl4 is almost independent of the concentration. The molecular weight dependence of the low-frequency spectrum in the PS/CCl4 shows that the M1 value of the low-frequency spectral band of PS shifts to higher frequencies when the molecular weight of PS increases up to Mw = ∼1000, which corresponds approximately to the decamer, and then remains constant upon further increasing the molecular weight.
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Affiliation(s)
- Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Katsuhiko Moriyama
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Kakinuma S, Shirota H. Femtosecond Raman-Induced Kerr Effect Study of Temperature-Dependent Intermolecular Dynamics in Pyrrolidinium-Based Ionic Liquids: Effects of Anion Species. J Phys Chem B 2019; 123:1307-1323. [DOI: 10.1021/acs.jpcb.8b10269] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Kakinuma S, Shirota H. Femtosecond Raman-Induced Kerr Effect Study of Temperature-Dependent Intermolecular Dynamics in Molten Bis(trifluoromethylsulfonyl)amide Salts: Effects of Cation Species. J Phys Chem B 2018; 122:6033-6047. [DOI: 10.1021/acs.jpcb.8b03302] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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9
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Xue L, Bardak F, Tamas G, Quitevis EL. Comparative study of the intermolecular dynamics of imidazolium-based ionic liquids with linear and branched alkyl chains: OHD-RIKES measurements. Phys Chem Chem Phys 2017; 19:4661-4672. [PMID: 28124692 DOI: 10.1039/c6cp08263g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This article describes a comparative study of the low-frequency (0-450 cm-1) Kerr spectra of the branched 1-(iso-alkyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([(N - 2)mCN-1C1im][NTf2] with N = 3-7) ionic liquids (ILs) and that of the linear 1-(n-alkyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([CNC1im][NTf2] with N = 2-7) ILs. The spectra were obtained by use of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The intermolecular spectrum of a branched IL is similar to that of a linear IL that is of the same alkyl chain length rather than of the same number of carbon atoms in the alkyl chain. This similarity and the lack of a correlation of the first spectral moments and widths of the intermolecular spectra with chain length is mainly attributed to the increase in the dispersion contribution to the total molar cohesive energy being compensated by stretching of the ionic network due to the increasing size of the nonpolar domains, which is dependent only on the length of the alkyl chain.
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Affiliation(s)
- Lianjie Xue
- Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
| | - Fehmi Bardak
- Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
| | - George Tamas
- Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
| | - Edward L Quitevis
- Department of Chemistry & Biochemistry, Texas Tech University, Lubbock, TX 79409, USA.
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Kakinuma S, Ishida T, Shirota H. Femtosecond Raman-Induced Kerr Effect Study of Temperature-Dependent Intermolecular Dynamics in Imidazolium-Based Ionic Liquids: Effects of Anion Species and Cation Alkyl Groups. J Phys Chem B 2017; 121:250-264. [DOI: 10.1021/acs.jpcb.6b11009] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Tateki Ishida
- Department
of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
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11
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Shirota H, Kakinuma S, Takahashi K, Tago A, Jeong H, Fujisawa T. Ultrafast Dynamics in Aromatic Cation Based Ionic Liquids: A Femtosecond Raman-Induced Kerr Effect Spectroscopic Study. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2016. [DOI: 10.1246/bcsj.20160085] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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12
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Lynden-Bell RM, Quitevis EL. The importance of polarizability: comparison of models of carbon disulphide in the ionic liquids [C1C1im][NTf2] and [C4C1im][NTf2]. Phys Chem Chem Phys 2016; 18:16535-43. [DOI: 10.1039/c6cp01752e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Three dimensional distribution of CS2 around a [C1C1im]+ ion showing the difference in behaviour of polarizable (red) and unpolarizable (blue) models of CS2.
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Shirota H, Kakinuma S. Temperature Dependence of Low-Frequency Spectra in Molten Bis(trifluoromethylsulfonyl)amide Salts of Imidazolium Cations Studied by Femtosecond Raman-Induced Kerr Effect Spectroscopy. J Phys Chem B 2015; 119:9835-46. [DOI: 10.1021/acs.jpcb.5b01776] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hideaki Shirota
- Department of Nanomaterial Science & Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Shohei Kakinuma
- Department of Nanomaterial Science & Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Cattaneo L, Savoini M, Muševič I, Kimel A, Rasing T. Ultrafast all-optical response of a nematic liquid crystal. OPTICS EXPRESS 2015; 23:14010-14017. [PMID: 26072770 DOI: 10.1364/oe.23.014010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Liquid crystals are superior optical materials for large area displays, but it is considered that their collective and slow-millisecond response makes them useless for ultrafast optical applications. In contrast to that, we here demonstrate an ultrafast optical response of a nematic liquid crystal, which is induced by an intense femtosecond optical impulse. We show that the refractive index of the nematic liquid crystal pentyl-cyanobiphenyl can be modulated at a time scale as fast as 500 fs via a coherently excited optical Kerr effect. The change in the refractive index is in the order of 10-4 at a fluence of 4 mJ/cm2 and is strongly polarization dependent. This unprecedented result opens new ways towards ultrafast all-optical modulation in liquid crystal-based devices.
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15
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Taschin A, Bartolini P, Eramo R, Righini R, Torre R. Optical Kerr effect of liquid and supercooled water: the experimental and data analysis perspective. J Chem Phys 2015; 141:084507. [PMID: 25173021 DOI: 10.1063/1.4893557] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The time-resolved optical Kerr effect spectroscopy (OKE) is a powerful experimental tool enabling accurate investigations of the dynamic phenomena in molecular liquids. We introduced innovative experimental and fitting procedures, that enable a safe deconvolution of sample response function from the instrumental function. This is a critical issue in order to measure the dynamics of liquid water. We report OKE data on water measuring intermolecular vibrations and the structural relaxation processes in an extended temperature range, inclusive of the supercooled states. The unpreceded data quality makes possible a solid comparison with few theoretical models: the multi-mode Brownian oscillator model, the Kubo's discrete random jump model, and the schematic mode-coupling model. All these models produce reasonable good fits of the OKE data of stable liquid water, i.e., over the freezing point. The features of water dynamics in the OKE data becomes unambiguous only at lower temperatures, i.e., for water in the metastable supercooled phase. We found that the schematic mode-coupling model provides the more rigorous and complete model for water dynamics, even if its intrinsic hydrodynamic approach does not give a direct access to the molecular information.
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Affiliation(s)
- A Taschin
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - P Bartolini
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - R Eramo
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - R Righini
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
| | - R Torre
- European Lab. for Non-Linear Spectroscopy (LENS), Univ. di Firenze, via N. Carrara 1, I-50019 Sesto Fiorentino, Firenze, Italy
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16
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Nakahara Y, Higashi M, Funayama R, Horii Y, Osuga H, Sakamoto H, Oda M, Kado S, Kimura K. Evaluation of Stretching Properties of [7]Thiaheterohelicene Framework Called “Molecular Spring” Using AFM Force Measurements and Electrostatic State Calculations. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2015. [DOI: 10.1246/bcsj.20140346] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yoshio Nakahara
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Minako Higashi
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Ryoto Funayama
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Yasuo Horii
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Hideji Osuga
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Hidefumi Sakamoto
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Masato Oda
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Shinpei Kado
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
| | - Keiichi Kimura
- Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University
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17
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Shirota H, Matsuzaki H, Ramati S, Wishart JF. Effects of Aromaticity in Cations and Their Functional Groups on the Low-Frequency Spectra and Physical Properties of Ionic Liquids. J Phys Chem B 2014; 119:9173-87. [DOI: 10.1021/jp509412z] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
| | | | - Sharon Ramati
- Chemistry
Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - James F. Wishart
- Chemistry
Department, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
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Bender JS, Coasne B, Fourkas JT. Assessing Polarizability Models for the Simulation of Low-Frequency Raman Spectra of Benzene. J Phys Chem B 2014; 119:9345-58. [DOI: 10.1021/jp509968v] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- John S. Bender
- Department of Chemistry & Biochemistry, ‡Institute for Physical Science and Technology, §Maryland NanoCenter, and ∥Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742, United States
- Multiscale Materials Science for Energy and Environment, UMI 3466
CNRS-MIT, and #Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachussetts Avenue, Cambridge, Massachusetts 02139, United States
| | - Benoit Coasne
- Department of Chemistry & Biochemistry, ‡Institute for Physical Science and Technology, §Maryland NanoCenter, and ∥Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742, United States
- Multiscale Materials Science for Energy and Environment, UMI 3466
CNRS-MIT, and #Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachussetts Avenue, Cambridge, Massachusetts 02139, United States
| | - John T. Fourkas
- Department of Chemistry & Biochemistry, ‡Institute for Physical Science and Technology, §Maryland NanoCenter, and ∥Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742, United States
- Multiscale Materials Science for Energy and Environment, UMI 3466
CNRS-MIT, and #Department
of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachussetts Avenue, Cambridge, Massachusetts 02139, United States
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19
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Biswas R, Das A, Shirota H. Low-frequency collective dynamics in deep eutectic solvents of acetamide and electrolytes: A femtosecond Raman-induced Kerr effect spectroscopic study. J Chem Phys 2014; 141:134506. [DOI: 10.1063/1.4897207] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Affiliation(s)
- Ranjit Biswas
- Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, J. D. Block, Sec. III, Salt Lake, Kolkata 700 098, West Bengal, India
| | - Anuradha Das
- Chemical, Biological and Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, J. D. Block, Sec. III, Salt Lake, Kolkata 700 098, West Bengal, India
| | - Hideaki Shirota
- Department of Nanomaterial Science and Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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20
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Lynden-Bell RM, Xue L, Tamas G, Quitevis EL. Local structure and intermolecular dynamics of an equimolar benzene and 1,3-dimethylimidazolium bis[(trifluoromethane)sulfonyl]amide mixture: Molecular dynamics simulations and OKE spectroscopic measurements. J Chem Phys 2014; 141:044506. [DOI: 10.1063/1.4890529] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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21
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Shirota H. Intermolecular/Interionic Vibrations of 1-Methyl-3-n-octylimidazolium Tetrafluoroborate Ionic Liquid and Benzene Mixtures. J Phys Chem B 2013; 117:7985-95. [DOI: 10.1021/jp402456g] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Hideaki Shirota
- Department of Nanomaterial Science
and Department of
Chemistry, Chiba University, 1-33 Yayoi,
Inage-ku Chiba 263-8522, Japan
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22
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Shirota H. Comparison of Low-Frequency Spectra between Aromatic and Nonaromatic Cation Based Ionic Liquids Using Femtosecond Raman-Induced Kerr Effect Spectroscopy. Chemphyschem 2012; 13:1638-48. [DOI: 10.1002/cphc.201100731] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2011] [Indexed: 11/08/2022]
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23
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Sun X, Stratt RM. The molecular underpinnings of a solute-pump/solvent-probe spectroscopy: the theory of polarizability response spectra and an application to preferential solvation. Phys Chem Chem Phys 2012; 14:6320-31. [DOI: 10.1039/c2cp24127g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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24
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Shirota H. Intermolecular Vibrations and Diffusive Orientational Dynamics of Cs Condensed Ring Aromatic Molecular Liquids. J Phys Chem A 2011; 115:14262-75. [DOI: 10.1021/jp208389n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Hideaki Shirota
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science & Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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25
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Shirota H, Kato T. Intermolecular Vibrational Spectra of C3v CXY3 Molecular Liquids, CHCl3, CHBr3, CFBr3, and CBrCl3. J Phys Chem A 2011; 115:8797-807. [DOI: 10.1021/jp203255u] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Affiliation(s)
- Hideaki Shirota
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
- Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Tatsuya Kato
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Fukazawa H, Ishida T, Shirota H. Ultrafast Dynamics in 1-Butyl-3-methylimidazolium-Based Ionic Liquids: A Femtosecond Raman-Induced Kerr Effect Spectroscopic Study. J Phys Chem B 2011; 115:4621-31. [DOI: 10.1021/jp200370f] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
| | - Tateki Ishida
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
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27
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Chakraborty A, Inagaki T, Banno M, Mochida T, Tominaga K. Low-Frequency Spectra of Metallocenium Ionic Liquids Studied by Terahertz Time-Domain Spectroscopy. J Phys Chem A 2011; 115:1313-9. [DOI: 10.1021/jp108097q] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Anjan Chakraborty
- Molecular Photoscience Research Center, Kobe University, Kobe, 657-8501 Japan
| | - Takashi Inagaki
- Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe, 657-8501 Japan
| | - Motohiro Banno
- Molecular Photoscience Research Center, Kobe University, Kobe, 657-8501 Japan
| | - Tomoyuki Mochida
- Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe, 657-8501 Japan
| | - Keisuke Tominaga
- Molecular Photoscience Research Center, Kobe University, Kobe, 657-8501 Japan
- Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe, 657-8501 Japan
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28
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Manfred K, He X, Fourkas JT. Assessing the role of moment of inertia in optical Kerr effect spectroscopy. J Phys Chem B 2010; 114:12096-103. [PMID: 20738116 DOI: 10.1021/jp106249t] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Optical Kerr effect (OKE) spectroscopy allows for the acquisition of high-quality, Bose-Einstein-corrected, low-frequency Raman spectra in liquids. However, the assignment of a molecular interpretation to these spectra remains an open problem. To address this issue, here we present an OKE study of benzene and four of its isotopologues. Our results indicate that hindered rotations are the major contributor to the OKE reduced spectral density (RSD) over the entire intermolecular spectral region (0-250 cm(-1)). We also have found that isotopologues with six (13)C atoms have RSDs that are enhanced at frequencies below 30 cm(-1). We further demonstrate that the collective orientational correlation time of these liquids scales with the inverse square root of the tumbling moment of inertia, indicating that there is strong translation-rotation coupling in benzene.
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Affiliation(s)
- Katherine Manfred
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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29
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Heisler IA, Meech SR. Low-frequency isotropic and anisotropic Raman spectra of aromatic liquids. J Chem Phys 2010; 132:174503. [DOI: 10.1063/1.3408288] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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30
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Pecheanu R, Cann NM. Molecular dynamics simulations of the liquid-crystal phases of 2-(4-butyloxyphenyl)-5-octyloxypyrimidine and 5-(4-butyloxyphenyl)-2-octyloxypyrimidine. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:041704. [PMID: 20481737 DOI: 10.1103/physreve.81.041704] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Indexed: 05/29/2023]
Abstract
In this paper, molecular dynamics simulations are employed to study the liquid-crystal phases of 2-(4-butyloxyphenyl)-5-octyloxypyrimidine and 5-(4-butyloxyphenyl)-2-octyloxypyrimidine. Both mesogens consist of aromatic phenyl-pyrimidine cores in between two identical alkoxy tails, but they differ in the preferred core conformation. The ab initio-based derivation of suitable molecular models is discussed in detail, with particular emphasis on capturing proper ring-ring interactions. The presence of ring quadrupoles in the molecular model is shown to be essential to the correct reproduction of the experimentally observed phases. Simulations of these fluids at various temperatures are performed and order, for the aromatic core and the flexible tails, is analyzed. To differentiate smectic- A from smectic- C phases, intermolecular structure is divided into contributions parallel and perpendicular to the director and layer normal.
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Affiliation(s)
- R Pecheanu
- Department of Chemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6
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31
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Fujisawa T, Nishikawa K, Shirota H. Comparison of interionic/intermolecular vibrational dynamics between ionic liquids and concentrated electrolyte solutions. J Chem Phys 2009; 131:244519. [DOI: 10.1063/1.3280028] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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32
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Shirota H, Fujisawa T, Fukazawa H, Nishikawa K. Ultrafast Dynamics in Aprotic Molecular Liquids: A Femtosecond Raman-Induced Kerr Effect Spectroscopic Study. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2009. [DOI: 10.1246/bcsj.82.1347] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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33
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Shirota H, Nishikawa K, Ishida T. Atom Substitution Effects of [XF6]− in Ionic Liquids. 1. Experimental Study. J Phys Chem B 2009; 113:9831-9. [DOI: 10.1021/jp809880j] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Hideaki Shirota
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan, and Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Keiko Nishikawa
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan, and Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Tateki Ishida
- Department of Nanomaterial Science, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan, and Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
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34
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Xiao D, Hines LG, Li S, Bartsch RA, Quitevis EL, Russina O, Triolo A. Effect of Cation Symmetry and Alkyl Chain Length on the Structure and Intermolecular Dynamics of 1,3-Dialkylimidazolium Bis(trifluoromethanesulfonyl)amide Ionic Liquids. J Phys Chem B 2009; 113:6426-33. [DOI: 10.1021/jp8102595] [Citation(s) in RCA: 190] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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35
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Zhong Q, Fourkas JT. Shape and Electrostatic Effects in Optical Kerr Effect Spectroscopy of Aromatic Liquids. J Phys Chem B 2008; 112:15342-8. [DOI: 10.1021/jp805874s] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Qin Zhong
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, Maryland NanoCenter, University of Maryland, College Park, Maryland 20742 and Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742
| | - John T. Fourkas
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, Maryland NanoCenter, University of Maryland, College Park, Maryland 20742 and Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742
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36
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Zhong Q, Fourkas JT. Optical Kerr Effect Spectroscopy of Simple Liquids. J Phys Chem B 2008; 112:15529-39. [DOI: 10.1021/jp807730u] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Qin Zhong
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, and Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742
| | - John T. Fourkas
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, and Center for Nanophysics and Advanced Materials, University of Maryland, College Park, Maryland 20742
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37
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Xiao D, Rajian JR, Hines LG, Li S, Bartsch RA, Quitevis EL. Nanostructural Organization and Anion Effects in the Optical Kerr Effect Spectra of Binary Ionic Liquid Mixtures. J Phys Chem B 2008; 112:13316-25. [DOI: 10.1021/jp804417t] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Dong Xiao
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
| | - Justin Rajesh Rajian
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
| | - Larry G. Hines
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
| | - Shengfu Li
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
| | - Richard A. Bartsch
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
| | - Edward L. Quitevis
- Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061
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38
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Heisler IA, Meech SR. Polarization-Resolved Ultrafast Polarizability Relaxation in Polar Aromatic Liquids. J Phys Chem B 2008; 112:12976-84. [DOI: 10.1021/jp805862z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Ismael A. Heisler
- School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom
| | - Stephen R. Meech
- School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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39
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Xiao D, Rajian JR, Cady A, Li S, Bartsch RA, Quitevis EL. Nanostructural Organization and Anion Effects on the Temperature Dependence of the Optical Kerr Effect Spectra of Ionic Liquids. J Phys Chem B 2007; 111:4669-77. [PMID: 17474695 DOI: 10.1021/jp066481b] [Citation(s) in RCA: 207] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The intermolecular spectra of three imidazolium ionic liquids were studied as a function of temperature by the use of optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The ionic liquids comprise the 1,3-pentylmethylimidazolium cation ([C(5)mim]+), and the anions, bromide (Br-), hexafluorophosphate (PF(6)-), and bis(trifluoromethanesulfonyl)imide (NTf(2)-). Whereas the optical Kerr effect (OKE) spectrum of [C(5)mim][NTf(2)] is temperature-dependent, the OKE spectra of [C(5)mim]Br and [C(5)mim][PF6] are temperature-independent. These results are surprising in light of the fact that the bulk densities of these room temperature ionic liquids (RTILs) are temperature-dependent. The temperature independence of the OKE spectra and the temperature dependence of the bulk density in [C(5)mim]Br and [C(5)mim][PF(6)] suggest that there are inhomogeneities in the densities of these liquids. The existence of density inhomogeneities is consistent with recent molecular dynamics simulations that show RTILs to be nanostructurally organized with nonpolar regions arising from clustering of the alkyl chains and ionic networks arising from charge ordering of the anions and imidazolium rings of the cations. Differences in the temperature dependences of the OKE spectra are rationalized on the basis of the degree of charge ordering in the polar regions of the RTILs.
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Affiliation(s)
- Dong Xiao
- Department of Chemistry, Texas Tech University, Lubbock, Texas 79409-1061, USA
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40
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Hunt NT, Jaye AA, Meech SR. Ultrafast dynamics in complex fluids observed through the ultrafast optically-heterodyne-detected optical-Kerr-effect (OHD-OKE). Phys Chem Chem Phys 2007; 9:2167-80. [PMID: 17487314 DOI: 10.1039/b616078f] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The ultrafast molecular dynamics of complex fluids have been recorded using the optically-heterodyne-detected optical-Kerr-effect (OHD-OKE). The OHD-OKE method is reviewed and some recent refinements to the method are described. Applications to a range of complex fluids, including microemulsions, polymer melts and solutions, liquid crystal and ionic liquids are surveyed. The level of detail attainable with the OHD-OKE method in these complex fluids is discussed. The prospects for future experiments are discussed.
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Affiliation(s)
- Neil T Hunt
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, UK NR4 7TJ
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41
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Shirota H, Castner EW. Molecular dynamics and interactions of aqueous and dichloromethane solutions of polyvinylpyrrolidone. J Chem Phys 2006; 125:34904. [PMID: 16863382 DOI: 10.1063/1.2208356] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We have investigated the dynamics of polyvinylpyrrolidone solutions (PVP, M(w)=10 000) on time scales from 20 fs to 42 ps using femtosecond optically heterodyne-detected Raman-induced Kerr effect spectroscopy. To compare the dynamics of polymer solutions with those of the analogous monomer, we also characterized solutions of 1-ethyl-2-pyrrolidone (EP). Dynamics of both PVP and EP solutions have been characterized for sample concentrations of 6.4, 12.7, 24.5, 33.3, and 40.7 wt %. The longest time scale relaxations observed in the Kerr transients for these solutions occur on the picosecond time scale and are best fit to triexponential functions. The intermediate and slow relaxation time constants for PVP and EP solutions are concentration dependent. The time constants for the PVP solutions are not consistent with the predictions of hydrodynamic models, while the analogous time constants for the EP solutions do display hydrodynamic scaling. The predominant relaxation of the polymer is assigned to reorientations of the pyrrolidone side group or torsional motions of the constitutional repeat unit, with additional relaxation pathways including hydrogen bond reorganization in aqueous solution and segmental motion of multiple repeat units. The vibrational dynamics of PVP and EP solutions occur on the femtosecond time scale. These dynamics are analyzed with a focus on the additional degrees of freedom experienced by EP relative to PVP that result from the absence of the tether from the pyrrolidone group on the main chain backbone. The intermolecular Kerr spectra of PVP in H(2)O and CH(2)Cl(2) differ because H(2)O can donate a hydrogen bond to the carbonyl acceptor group on the pyrrolidone ring, while CH(2)Cl(2) cannot.
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Affiliation(s)
- Hideaki Shirota
- Department of Chemistry and Chemical Biology, Rutgers-The State University of New Jersey, Piscataway, NJ 08854-8087, USA.
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42
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Elola MD, Ladanyi BM. Molecular Dynamics Study of Polarizability Anisotropy Relaxation in Aromatic Liquids and Its Connection with Local Structure. J Phys Chem B 2006; 110:15525-41. [PMID: 16884276 DOI: 10.1021/jp062071b] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The collective polarizability anisotropy dynamics in a set of three aromatic liquids, benzene (Bz), hexafluorobenzene (HFB), and 1,3,5-trifluorobenzene (TFB), has been studied by molecular dynamics simulation. These liquids have very similar shapes, but different electrostatic interactions due to opposite polarities of C-H and C-F bonds, giving rise to different local intermolecular structures in the liquid phase. We have investigated how these structural arrangements affect polarizability anisotropy dynamics observed in optical Kerr-effect (OKE) spectroscopy. We have modeled the interaction-induced polarizability with the first-order dipole-induced dipole approximation, with the molecular polarizability distributed over the carbon sites. Local contributions to the librational OKE spectrum were computed separately for molecules participating in parallel or perpendicular relative orientations within the first coordination shell. We found that the relative locations of parallel and perpendicular librational bands of the OKE spectra are closely related to the corresponding pair energy distributions of the closest four neighbors of a given molecule, corresponding to a model of a harmonic oscillator in a cage of nearest neighbors. This model predicts higher librational frequencies for more attractive intermolecular interactions, which in all three liquids correspond to parallel local arrangements. On the diffusive orientational time scale, all three liquids exhibit slower relaxation of molecules in parallel arrangements, although the difference in relaxation rates is substantial only in TFB, which has the strongest tendency toward parallel stacking. The analysis of the collective polarizability relaxation was performed using two different approaches, the projection scheme (J. Chem. Phys. 1980, 72, 2801) and the theory developed by Steele (Mol. Phys. 1987, 61, 1031) for the second time derivatives applied to collective time correlations. Both approaches allow the decomposition of the OKE response into contributions from orientational relaxation and other dynamical processes. We find that they lead to different predictions on how the response depends on collective reorientation and processes arising from fluctuations in the interaction-induced polarizability. We discuss the reasons for these differences and the advantages and disadvantages of the two analysis schemes.
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Affiliation(s)
- M Dolores Elola
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA.
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