101
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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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102
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Kashyap HK, Biswas R. Dipolar Solvation Dynamics in Room Temperature Ionic Liquids: An Effective Medium Calculation Using Dielectric Relaxation Data. J Phys Chem B 2008; 112:12431-8. [DOI: 10.1021/jp8044516] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Hemant K. Kashyap
- Department of Chemical, Biological & Macromolecular Sciences, and Unit for Nanoscience and Technology, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700 098, India
| | - Ranjit Biswas
- Department of Chemical, Biological & Macromolecular Sciences, and Unit for Nanoscience and Technology, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata 700 098, India
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103
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Shim Y, Kim HJ. Dielectric Relaxation, Ion Conductivity, Solvent Rotation, and Solvation Dynamics in a Room-Temperature Ionic Liquid. J Phys Chem B 2008; 112:11028-38. [DOI: 10.1021/jp802595r] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Youngseon Shim
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, and School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-722, Korea
| | - Hyung J. Kim
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, and School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-722, Korea
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104
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Fumino K, Wulf A, Ludwig R. The cation-anion interaction in ionic liquids probed by far-infrared spectroscopy. Angew Chem Int Ed Engl 2008; 47:3830-4. [PMID: 18412214 DOI: 10.1002/anie.200705736] [Citation(s) in RCA: 230] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Koichi Fumino
- Institut für Chemie, Abteilung Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 1, 18059 Rostock, Germany
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105
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Hu Z, Huang X, Annapureddy HVR, Margulis CJ. Molecular Dynamics Study of the Temperature-Dependent Optical Kerr Effect Spectra and Intermolecular Dynamics of Room Temperature Ionic Liquid 1-Methoxyethylpyridinium Dicyanoamide. J Phys Chem B 2008; 112:7837-49. [DOI: 10.1021/jp800729g] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Zhonghan Hu
- Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, and Department of Chemistry, Columbia University, New York, New York 10027
| | - Xuhui Huang
- Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, and Department of Chemistry, Columbia University, New York, New York 10027
| | - Harsha V. R. Annapureddy
- Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, and Department of Chemistry, Columbia University, New York, New York 10027
| | - Claudio J. Margulis
- Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, and Department of Chemistry, Columbia University, New York, New York 10027
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106
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Fumino K, Wulf A, Ludwig R. Fern-IR-spektroskopische Charakterisierung der Wechselwirkung zwischen Kationen und Anionen in ionischen Flüssigkeiten. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200705736] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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107
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The Chemical Environment of Ionic Liquids: Links Between Liquid Structure, Dynamics, and Solvation. ADVANCES IN CHEMICAL PHYSICS 2008. [DOI: 10.1002/9780470259498.ch2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
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108
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Stoppa A, Hunger J, Buchner R, Hefter G, Thoman A, Helm H. Interactions and Dynamics in Ionic Liquids. J Phys Chem B 2008; 112:4854-8. [DOI: 10.1021/jp800852z] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
| | | | | | - Glenn Hefter
- ChemistryDSE, Murdoch University, Murdoch, W.A. 6150, Australia
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109
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Mukherjee P, Crank JA, Sharma PS, Wijeratne AB, Adhikary R, Bose S, Armstrong DW, Petrich JW. Dynamic solvation in phosphonium ionic liquids: comparison of bulk and micellar systems and considerations for the construction of the solvation correlation function, C(t). J Phys Chem B 2008; 112:3390-6. [PMID: 18298112 DOI: 10.1021/jp7107126] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Dynamic solvation of the dye coumarin 153 is studied in a phosphonium ionic liquid: hexadecyltributylphosphonium bromide, [(C4)3C16P+][Br-]. It forms micelles in water, and the bulk also exists as a liquid under our experimental conditions. This system permits a comparison with an imidazolium ionic liquid studied earlier, which also formed micelles in water (J. Phys. Chem. A 2006, 110, 10725-10730). We conclude that our analysis of the comparable situation in a phosphonium liquid is not as definitive as we had proposed earlier, i.e., that the majority of the early-time solvation arises from the organic cation. Part of the difficulty in performing this analysis is most likely due to the amount of water that is associated with the micelle. In the course of this work, we have focused on the calculation of the solvation correlation function, C(t), and investigated how it depends upon the methods with which the "zero-time" spectrum is constructed.
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Affiliation(s)
- Prasun Mukherjee
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
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110
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Lohse PW, Bürsing R, Lenzer T, Oum K. Exploring 12‘-Apo-β-carotenoic-12‘-acid as an Ultrafast Polarity Probe for Ionic Liquids. J Phys Chem B 2008; 112:3048-57. [DOI: 10.1021/jp710766z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Peter W. Lohse
- Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstrasse 6, 37077 Göttingen, Germany and Max-Planck-Institut für biophysikalische Chemie, Abt. Spektroskopie und Photochemische Kinetik (10100), Am Fassberg 11, 37077 Göttingen, Germany
| | - Reinhard Bürsing
- Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstrasse 6, 37077 Göttingen, Germany and Max-Planck-Institut für biophysikalische Chemie, Abt. Spektroskopie und Photochemische Kinetik (10100), Am Fassberg 11, 37077 Göttingen, Germany
| | - Thomas Lenzer
- Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstrasse 6, 37077 Göttingen, Germany and Max-Planck-Institut für biophysikalische Chemie, Abt. Spektroskopie und Photochemische Kinetik (10100), Am Fassberg 11, 37077 Göttingen, Germany
| | - Kawon Oum
- Georg-August-Universität Göttingen, Institut für Physikalische Chemie, Tammannstrasse 6, 37077 Göttingen, Germany and Max-Planck-Institut für biophysikalische Chemie, Abt. Spektroskopie und Photochemische Kinetik (10100), Am Fassberg 11, 37077 Göttingen, Germany
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111
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Weingärtner H. Understanding Ionic Liquids at the Molecular Level: Facts, Problems, and Controversies. Angew Chem Int Ed Engl 2008; 47:654-70. [DOI: 10.1002/anie.200604951] [Citation(s) in RCA: 1286] [Impact Index Per Article: 80.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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112
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Weingärtner H. Zum Verständnis ionischer Flüssigkeiten auf molekularer Ebene: Fakten, Probleme und Kontroversen. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200604951] [Citation(s) in RCA: 165] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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113
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Paul A, Samanta A. Effect of Nonpolar Solvents on the Solute Rotation and Solvation Dynamics in an Imidazolium Ionic Liquid. J Phys Chem B 2007; 112:947-53. [DOI: 10.1021/jp077536s] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Aniruddha Paul
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India
| | - Anunay Samanta
- School of Chemistry, University of Hyderabad, Hyderabad 500046, India
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114
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Castner EW, Wishart JF, Shirota H. Intermolecular dynamics, interactions, and solvation in ionic liquids. Acc Chem Res 2007; 40:1217-27. [PMID: 18020400 DOI: 10.1021/ar700169g] [Citation(s) in RCA: 222] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ionic liquids can simultaneously assume multiple solvent roles, because they are strongly polar and polarizable solvents and binary solutions and frequently contain very hydrophobic components. When the cation and anion functional groups are tuned appropriately, ionic liquids can be used as designer solvents for a broad range of applications. In this Account, we discuss our spectroscopic studies on the intermolecular interactions, dynamics, solvation, transport, and friction in ionic liquids, as compared with information obtained from macroscopic experiments including viscometry and calorimetry.
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Affiliation(s)
- Edward W. Castner
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8087, Chemistry Department, Brookhaven National Laboratory, Building 555A, Upton, New York 11973-5000, and Division of Nanoscience, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - James F. Wishart
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8087, Chemistry Department, Brookhaven National Laboratory, Building 555A, Upton, New York 11973-5000, and Division of Nanoscience, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Hideaki Shirota
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8087, Chemistry Department, Brookhaven National Laboratory, Building 555A, Upton, New York 11973-5000, and Division of Nanoscience, Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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115
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Iwata K, Okajima H, Saha S, Hamaguchi HO. Local structure formation in alkyl-imidazolium-based ionic liquids as revealed by linear and nonlinear Raman spectroscopy. Acc Chem Res 2007; 40:1174-81. [PMID: 17963358 DOI: 10.1021/ar700074c] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We show several pieces of Raman spectroscopic evidence that are indicative of local structure formation in imidazolium-based ionic liquids. Low-frequency Raman spectra of C n mimX, where C n mim stands for 1-alkyl(C n H 2 n+1 )-3-methylimidazolium cation and X represents the anion, exhibit broad bands assignable to collective modes of local structures. Spatial distributions of coherent anti-Stokes Raman scattering (CARS) signals from C n mim[PF 6] are consistent with local structures whose size increases with increasing n. Picosecond Raman spectra of S 1 trans-stilbene as a "picosecond Raman thermometer" show microscopic thermal inhomogeneity ascribable to local structure formation in C 2mimTf 2N and C 4mimTf 2N. We also describe two novel phenomena that we believe are relevant to extraordinary nanoenvironments generated by local structures in a magnetic ionic liquid C 4mim[FeCl 4].
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Affiliation(s)
- Koichi Iwata
- Research Centre for Spectrochemistry and Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Chemistry, Banaras Hindu University; Varanasi 221005, India, and Institute of Molecular Science and Department of Applied Chemistry, National Chiao Tung University; 1001 Ta Hsueh Road, Hsinchu 300, Taiwan
| | - Hajime Okajima
- Research Centre for Spectrochemistry and Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Chemistry, Banaras Hindu University; Varanasi 221005, India, and Institute of Molecular Science and Department of Applied Chemistry, National Chiao Tung University; 1001 Ta Hsueh Road, Hsinchu 300, Taiwan
| | - Satyen Saha
- Research Centre for Spectrochemistry and Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Chemistry, Banaras Hindu University; Varanasi 221005, India, and Institute of Molecular Science and Department of Applied Chemistry, National Chiao Tung University; 1001 Ta Hsueh Road, Hsinchu 300, Taiwan
| | - Hiro-o Hamaguchi
- Research Centre for Spectrochemistry and Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan, Department of Chemistry, Banaras Hindu University; Varanasi 221005, India, and Institute of Molecular Science and Department of Applied Chemistry, National Chiao Tung University; 1001 Ta Hsueh Road, Hsinchu 300, Taiwan
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116
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Aslanov LA, Zakharov MA, Knyazeva EE, Yatsenko AV. Preparation of mesoporous aluminum hydroxide and oxide in ionic liquids. RUSS J INORG CHEM+ 2007. [DOI: 10.1134/s0036023607100051] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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117
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Schröder C, Rudas T, Neumayr G, Gansterer W, Steinhauser O. Impact of anisotropy on the structure and dynamics of ionic liquids: A computational study of 1-butyl-3-methyl-imidazolium trifluoroacetate. J Chem Phys 2007; 127:044505. [PMID: 17672705 DOI: 10.1063/1.2754690] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The complex ionic network of 1-butyl-3-methyl-imidazolium trifluoroacetate was simulated by means of the molecular dynamics methods over a time period of 100 ns. The influence of the anisotropy of the shape and charge distribution of both the cations and the anions on the local (molecular) and global (collective) structure and dynamics is analyzed. The distance-dependent g coefficients of the orientational probability function g(r,Omega) were found to be an excellent way to interpret local structure. Thereby, the combination and interrelation of individual g coefficients elucidate the mutual orientation. Dynamics at the molecular level is characterized by the time correlation function of the center-of-mass corrected molecular dipole moment mucm. Upon uniting the set of molecular dipoles to a single collective rotational dipole moment, MD, dynamics on a global level is studied. Decomposing into subsets of cations and anions respective self terms as well as the prominent cross term can be extracted. This decomposition also enables a detailed peak assignment in dielectric spectra.
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Affiliation(s)
- C Schröder
- Department of Computational Biological Chemistry, University of Vienna, A-1090 Vienna, Austria
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118
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Chung SH, Lopato R, Greenbaum SG, Shirota H, Castner EW, Wishart JF. Nuclear Magnetic Resonance Study of the Dynamics of Imidazolium Ionic Liquids with −CH2Si(CH3)3 vs −CH2C(CH3)3 Substituents. J Phys Chem B 2007; 111:4885-93. [PMID: 17441766 DOI: 10.1021/jp071755w] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Trimethylsilylmethyl (TMSiM)-substituted imidazolium bis(trifluoromethylsulfonyl)imide (NTf(2)-), and tetrafluoroborate (BF(4)-) 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 eta and D data generally show fractional Stokes-Einstein behavior D proportional to (T/eta)m. This is most prominent in the neopentylimidazolium BF(4)- IL with m approximately 0.66.
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Affiliation(s)
- Song H Chung
- Department of Chemistry and Physics, William Paterson University of New Jersey, Wayne, New Jersey 07470, USA.
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119
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Yamamoto K, Tani M, Hangyo M. Terahertz Time-Domain Spectroscopy of Imidazolium Ionic Liquids. J Phys Chem B 2007; 111:4854-9. [PMID: 17419609 DOI: 10.1021/jp067171w] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
We have measured the terahertz (THz) complex dielectric spectra of imidazolium ionic liquids by THz time-domain spectroscopy (THz-TDS) in the frequency range from 5 (0.15 THz) to 140 cm(-1) (4.2 THz). The ionic liquids investigated are 1-ethyl-3-methylimidazolium (EMIm+)/trifluoromethanesulfonate (TfO-), EMIm+/tetrafluoroborate (BF(4)-), 1-butyl-3-methylimidazolium (BMIm+)/TfO-, and BMIm+/BF(4)-. The dielectric values of the ionic liquids in the THz region are similar to those of short-chain alcohols. The THz dielectric values are related to subpicosecond-to-picosecond dynamics. The same trend has been observed in the empirical polarity ET(30) although it is related to the static characteristics of polarity and hydrogen bonding ability. A difference between the two types of liquids is observed in the THz dielectric spectral shapes: the ionic liquids show structured lineshapes but short-chain alcohols show much less structured ones. The structured lineshapes of the ionic liquids reflect the low-frequency motions of interion and/or intramolecular vibrations. When the ionic liquids composed of the different imidazolium cations contain the same anions as counterions, their density-normalized THz dielectric spectra above 20 cm(-1) bear strong resemblance to each other in shape and magnitude. It shows clearly that the THz spectra do not originate from the intramolecular vibrations of the imodazolium cations. All of the intramolecular vibrations of the anions are located above 140 cm(-1) except the CF3-SO3 torsion of TfO-, the band of which alone cannot explain the broad THz dielectric spectra of the ionic liquids. Therefore, we conclude that the interion vibrations rather than the intramolecular vibrations dominantly contribute to the THz dielectric spectra. The results strongly indicate that even in the liquid phase the ionic liquids have local structures similar to their solid-phase structures.
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Affiliation(s)
- Kohji Yamamoto
- PRESTO, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
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120
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Shirota H, Wishart JF, Castner EW. Intermolecular Interactions and Dynamics of Room Temperature Ionic Liquids That Have Silyl- and Siloxy-Substituted Imidazolium Cations. J Phys Chem B 2007; 111:4819-29. [PMID: 17417895 DOI: 10.1021/jp067126o] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The intermolecular interactions and dynamics of novel ionic liquids with alkylsilyl and alkylsiloxy substitutions on the cations are studied by measuring the intermolecular vibrational spectra and reorientational dynamics using femtosecond Kerr effect methods. The new ionic liquids include 1-dimethylphenylsilylmethyl-3-methylimidazolium (PhSi-mim+), and 1-methyl-3-pentamethyldisiloxymethylimidazolium (SiOSi-mim+) cations paired with the bis(trifluoromethylsulfonyl)imide (NTf(2)-) anion. Measured ionic liquid viscosities are surprisingly low for such bulky cation substituents. DFT electronic structure calculations on the isolated ions provide additional information about the electrostatic interactions.
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Affiliation(s)
- Hideaki Shirota
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, New Jersey 08854-8087, USA.
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121
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Schröder C, Wakai C, Weingärtner H, Steinhauser O. Collective rotational dynamics in ionic liquids: A computational and experimental study of 1-butyl-3-methyl-imidazolium tetrafluoroborate. J Chem Phys 2007; 126:084511. [PMID: 17343462 DOI: 10.1063/1.2464057] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The aim of this study is the analysis of the rotational motion in ionic liquids, in particular, 1-butyl-3-methyl-imidazolium tetrafluoroborate. By comparing single-particle and collective motion it is found that the Madden-Kivelson relation is fairly fulfilled in long-term simulation studies (>100 ns), i.e., the collective reorientation can be predicted by the corresponding single-particle property and the static dipolar correlation factor, GK. Furthermore, simulated reorientation is in accordance with hydrodynamic theories yielding hydrodynamic radii comparable to van der Waals radii. Since viscosity is the central quantity entering hydrodynamic formulas, we calculated and measured the viscosity of our system in order to have two independent cycles of hydrodynamic evaluation, a computational and an experimental one. While the static dielectric constant agrees with dielectric reflectance experiment, the hydrodynamic radii derived from the experiments are much lower as a consequence of enhanced rotational motion. Even more, a considerable dynamic broadening is observed in the experiments.
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Affiliation(s)
- C Schröder
- Department of Computational Biological Chemistry, University of Vienna, A-1090 Vienna, Austria
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122
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Weingärtner H, Sasisanker P, Daguenet C, Dyson PJ, Krossing I, Slattery JM, Schubert T. The Dielectric Response of Room-Temperature Ionic Liquids: Effect of Cation Variation. J Phys Chem B 2007; 111:4775-80. [PMID: 17279790 DOI: 10.1021/jp0671188] [Citation(s) in RCA: 174] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In continuation of recent work on the dielectric response of imidazolium-based ionic liquids (ILs) (J. Phys. Chem. B, 2006, 110, 12682), we report on the effect of cation variation on the frequency-dependent dielectric permittivity up to 20 GHz of ionic liquids. The salts are comprised of pyrrolidinium, pyridinium, tetraalkylammonium, and triethylsulfonium cations combined with the bis-((trifluoromethyl)sulfonyl)imide anion. The dielectric spectra resemble those observed for imidazolium salts with the same anion. In all cases, the major contribution results from a diffusive low-frequency response on the time scale of several 100 ps, which shows a broadly distributed kinetics similar to that of spatially heterogeneous states in supercooled and glassy systems rather than that observed in fluid systems. There is evidence for a weak secondary process near 10-20 ps. Perhaps the most interesting difference to imidazolium salts is founded in the missing portions of the spectra due to processes beyond the upper cutoff frequency of 20 GHz. These are lower than that observed for imidazolium-based salts and seem to vanish for tetraalkylammonium and triethylsulfonium salts. As for imidazolium salts, the extrapolated static dielectric constants are on the order of epsilon(S) congruent with 10-13, classifying these ILs as solvents of moderate polarity.
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123
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Jeong D, Shim Y, Choi MY, Kim HJ. Effects of Solute Electronic Polarizability on Solvation in a Room-Temperature Ionic Liquid. J Phys Chem B 2007; 111:4920-5. [PMID: 17253742 DOI: 10.1021/jp067316z] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The effects of solute polarizability on solvation and solute transport in the room-temperature ionic liquid 1-ethyl-3-methylimidazolium hexafluorophosphate (EMI+PF(6)-) are investigated via molecular dynamics simulations. A valence-bond description is employed to account for the instantaneous adjustment of the solute electronic charge distribution to the fluctuating solvent environment. It is found that the ultrafast inertial component of solvation dynamics becomes slower as the solute polarizability grows. Moreover, its contribution to overall solvent relaxation becomes reduced with increasing polarizability, especially in the case of nonequilibrium solvation dynamics. Overall, the inclusion of the solute electronic polarizability in the simulations improves the agreement with time-dependent Stokes shift measurements.
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Affiliation(s)
- Daun Jeong
- Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
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124
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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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125
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Paul A, Samanta A. Solute Rotation and Solvation Dynamics in an Alcohol-Functionalized Room Temperature Ionic Liquid. J Phys Chem B 2007; 111:4724-31. [PMID: 17474699 DOI: 10.1021/jp065790z] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Steady-state and time-resolved fluorescence behaviors of two dipolar solutes, coumarin 153 and 4-aminophthalimide, have been studied in an alcohol-functionalized room-temperature ionic liquid, 1-(hydroxyethyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide. The steady-state fluorescence parameters have been exploited for the estimation of the polarity of this ionic liquid and to obtain information on the hydrogen bonding interaction between the ionic liquid and the probe molecules. The time-resolved measurements have been focused on the dynamics of solvation by studying the dynamic Stokes shift in the ps-ns time scale and solute rotation by measuring the time dependence of the fluorescence anisotropy. The time-resolved anisotropy studies reveal a significant slow down of the rotational motion of one of the probe molecules. The time-dependent fluorescence Stokes shift measurements suggest that the time-resolvable part of the dynamics is biphasic in nature, highly dependent on the probe molecule and the ultrafast component is comparatively less than that in other ionic liquids. The influence of the hydrogen bonding interaction between the probe molecules and the ionic liquids on the solute rotation and the various components of the solvation dynamics is carefully analyzed in an attempt to obtain further insight into the mechanism of solvation in these novel media.
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Affiliation(s)
- Aniruddha Paul
- School of Chemistry, University of Hyderabad, Hyderabad 500 046, India
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126
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Hunt PA, Gould IR, Kirchner B. The Structure of Imidazolium-Based Ionic Liquids: Insights From Ion-Pair Interactions. Aust J Chem 2007. [DOI: 10.1071/ch06301] [Citation(s) in RCA: 181] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A large number of ab-initio (B3LYP/6–31++G(d,p)) computed ion-pair structures have been examined in order to determine if such calculations are capable of offering insight into the physical properties of the liquid state, particularly viscosity and melting point. Ion pairings based around the 1-butyl-3-methylimidazolium (C4C1im) cations and a range of anions (Cl, BF4, and N(Tf)2 where N(Tf)2 is bis(trifluoromethylsulfonly)imide) were chosen because of the range of viscosities exhibited by the corresponding ionic liquids. We have used these results to build up a ‘picture’ of the ionic liquid structure which is consistent with molecular dynamics simulations and experimental evidence. However, further work is required to established if such an analysis could be predictive. Nevertheless, we establish clear relationships relating ion-pair association energy, a derived ‘connectivity index’, and the diversity of structures with viscosity and melting point. Our calculations indicate that ions in C4C1imCl form a strong, highly connected and regular array thus rationalizing the high viscosity and melting point. In contrast the ion-pairs of C4C1imN(Tf)2 form a weakly interacting, highly disordered, and low connectivity network consistent with the low viscosity and melting point. C4C1imBF4 lies midway between these two extremes.
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127
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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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128
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Schröder C, Rudas T, Steinhauser O. Simulation studies of ionic liquids: Orientational correlations and static dielectric properties. J Chem Phys 2006; 125:244506. [PMID: 17199354 DOI: 10.1063/1.2404674] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ionic liquids BMIM+I-, BMIM+BF4-, and BMIM+PF6- were simulated by means of the molecular dynamics method over a time period of more than 100 ns. Besides the common structural analysis, e.g., radial distribution functions and three dimensional occupancy plots, a more sophisticated orientational analysis was performed. The angular correlation functions g(00)110(r) and g(00)101(r) are the first distance dependent coefficients of the pairwise orientational distribution function g(rij,Omega1,Omega2,Omega12). These functions help to interpret the three dimensional plot and reveal interesting insights into the local structure of the analyzed ionic liquids. Furthermore, the collective network of ionic liquids can be characterized by the Kirkwood factor Gkappa(r) [J. Chem. Phys. 7, 911 (1939)]. The short-range behavior (r<10 A) of this factor may be suitable to predict the water miscibility of the ionic liquid. The long-range limit of Gkinfinity is below 1 which demonstrates the strongly coupled nature of the ionic liquid networks. In addition, this factor relates the orientational structure and the dielectric properties of the ionic liquids. The static dielectric constant epsilon(omega=0) for the simulated system is 8.9-9.5. Since in ionic liquids the very same molecule contributes to the total dipole moment as well as carries a net charge, a small, but significant contribution of the cross term between the total dipole moment and the electric current to epsilon(omega=0) is observed.
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Affiliation(s)
- C Schröder
- Department of Computational Biological Chemistry, University of Vienna, A-1090 Vienna, Austria
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129
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Ribeiro MCC. Correlation between Quasielastic Raman Scattering and Configurational Entropy in an Ionic Liquid. J Phys Chem B 2006; 111:5008-15. [PMID: 17474704 DOI: 10.1021/jp063810r] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Low-frequency (5-200 cm(-1)) Raman spectra are reported for the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim]PF(6), in glassy, supercooled liquid, and normal liquid phases (77-330 K). Raman spectra of [bmim]PF(6) agree with previous results obtained by optical Kerr effect spectroscopy and molecular dynamics simulation. Both the superposition model and the coupling model give reasonable fit to low-frequency Raman spectra of [bmim]PF(6). The configurational entropy of [bmim]PF(6) has been evaluated as a function of temperature using recently reported data of heat capacity. The calculated configurational entropy is inserted in the Adam-Gibbs theory for supercooled liquids, giving a good fit to non-Arrhenius behavior of viscosity and diffusive process, with the latter revealed by a recent neutron scattering investigation of [bmim]PF(6). There is a remarkable linear dependence between intensity of quasielastic Raman scattering and configurational entropy from 77 K up to the melting point of [bmim]PF(6). This correlation offers insight into the nature of dynamical processes probed by low-frequency Raman spectra of ionic liquids.
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Affiliation(s)
- Mauro C C Ribeiro
- Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo, C.P. 26077, CEP 05513-970, São Paulo, SP, Brazil.
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130
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Seth D, Chakraborty A, Setua P, Sarkar N. Interaction of ionic liquid with water in ternary microemulsions (Triton X-100/water/1-butyl-3-methylimidazolium hexafluorophosphate) probed by solvent and rotational relaxation of coumarin 153 and coumarin 151. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:7768-75. [PMID: 16922562 DOI: 10.1021/la061356c] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
The interaction of ionic liquid with water in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6])/Triton X-100 (TX-100)/H2O ternary microemulsions, i.e., "[bmim][PF6]-in-water" microregions of the microemulsions, has been studied by the dynamics of solvent and rotational relaxation of coumarin 153 (C-153) and coumarin 151 (C-151). The variation of the time constants of solvent relaxation of C-153 is very small with an increase in the [bmim][PF6]/TX-100 ratio (R). The rotational relaxation time of C-153 also remains unchanged in all micremulsions of different R values. The invariance of solvation and rotational relaxation times of C-153 indicates that the position of C-153 remains unaltered with an increase in R and probably the probe is located at the interfacial region of [bmim][PF6] and TX-100 in the microemulsions. On the other hand, in the case of C-151, with an increase in R the fast component of the solvation time gradually increases and the slow component gradually decreases, although the change in solvation time is small in comparison to that of microemulsions containing common polar solvents such as water, methanol, acetonitrile, etc. The rotational relaxation time of C-151 increases with an increase in R. This indicates that with an increase in the [bmim][PF6] content the number of C-151 molecules in the core of the microemulsions gradually increases. In general, the solvent relaxation time is retarded in this room temperature ionic liquid/water-containing microemulsion compared to that of a neat solvent, although retardation is very small compared to that of the solvent relaxation time of the conventional solvent in the core of the microemulsions.
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Affiliation(s)
- Debabrata Seth
- Department of Chemistry, Indian Institute of Technology, Kharagpur 721 302, WB, India
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131
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Mukherjee P, Crank JA, Halder M, Armstrong DW, Petrich JW. Assessing the Roles of the Constituents of Ionic Liquids in Dynamic Solvation: Comparison of an Ionic Liquid in Micellar and Bulk Form. J Phys Chem A 2006; 110:10725-30. [PMID: 16970363 DOI: 10.1021/jp063433i] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamic solvation of the dye, coumarin 153, is compared in an ionic liquid that forms micelles in water against the bulk solvent. This provides the unprecedented opportunity of investigating the behavior of the ionic liquid in two globally different configurations. It is proposed that the imidazolium moiety is in both cases responsible for the majority of the solvation, which manifests itself in the first 100 ps. Exploiting the use of ionic liquids capable of accommodating specific structures thus provides a deeper insight into how solutes interact with these fascinating and interesting solvents (at least those that are imidazolium based) that are gaining ever increasing interest in the scientific community.
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Affiliation(s)
- Prasun Mukherjee
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA
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132
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Xiao D, Rajian JR, Li S, Bartsch RA, Quitevis EL. Additivity in the Optical Kerr Effect Spectra of Binary Ionic Liquid Mixtures: Implications for Nanostructural Organization. J Phys Chem B 2006; 110:16174-8. [PMID: 16913736 DOI: 10.1021/jp063740o] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Low-frequency spectra of binary room-temperature ionic liquid (RTIL) mixtures of 1-pentyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide and 1-pentyl-3-methylimidazolium bromide in the 0-250 cm(-1) region were studied as a function of mole fraction at 295 K. The spectra were obtained by use of optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The spectra of these binary mixtures are well described by the weighted sums of the spectra for the neat RTILs. This surprising result implies that the intermolecular modes giving rise to the spectra of the neat liquids must also produce the spectra of the mixtures. Additivity of the OKE spectra can be explained by a model in which locally ordered domains are assumed to exist in the neat liquid with the structures of these locally ordered domains preserved upon mixing. Recently published molecular dynamics simulations show that RTILs are nanostructurally organized with ionic networks and nonpolar regions. If ionic networks also exist in the mixture, the additivity of the OKE spectra implies that there are "blocks" along the network of the mixture that are ordered in the same way as in the neat liquids. These "block co-networks" would have a nanostructural organization resembling that of a block copolymer.
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133
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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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134
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Headley LS, Mukherjee P, Anderson JL, Ding R, Halder M, Armstrong DW, Song X, Petrich JW. Dynamic Solvation in Imidazolium-Based Ionic Liquids on Short Time Scales. J Phys Chem A 2006; 110:9549-54. [PMID: 16884187 DOI: 10.1021/jp0606964] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Steady-state and time-resolved Stokes shift data for the probe coumarin 153 in two imidazoles, six imidazolium-based ionic liquids, and several other solvents are presented. These results are consistent with our original suggestion (J. Phys. Chem. B 2004, 108, 10245-10255) that initial solvation is dominated by the organic moiety of the ionic liquid, and they show that for the imidazole-based liquids initial solvation is in all cases very rapid. Solvation by methylimidazole and butylimidazole is complete in 100 ps, and all of the imidazolium ionic liquids demonstrate similarly rapid initial solvation. Owing to the importance of determining the amount of initial solvation that is missed in a given experiment with finite time resolution, we discuss a method of estimating the intramolecular contribution to the reorganization energy. This method yields 2068 cm(-1) and is compared with an alternative method.
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135
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Daguenet C, Dyson PJ, Krossing I, Oleinikova A, Slattery J, Wakai C, Weingärtner H. Dielectric Response of Imidazolium-Based Room-Temperature Ionic Liquids. J Phys Chem B 2006; 110:12682-8. [PMID: 16800602 DOI: 10.1021/jp0604903] [Citation(s) in RCA: 233] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have used microwave dielectric relaxation spectroscopy to study the picosecond dynamics of five low-viscosity, highly conductive room temperature ionic liquids based on 1-alkyl-3-methylimidazolium cations paired with the bis((trifluoromethyl)sulfonyl)imide anion. Up to 20 GHz the dielectric response is bimodal. The longest relaxation component at the time scale of several 100 ps reveals strongly nonexponential dynamics and correlates with the viscosity in a manner consistent with hydrodynamic predictions for the diffusive reorientation of dipolar ions. Methyl substitution at the C2 position destroys this correlation. The time constants of the weak second process at the 20 ps time scale are practically the same for each salt. This intermediate process seems to correlate with similar modes in optical Kerr effect spectra, but its physical origin is unclear. The missing high-frequency portion of the spectra indicates relaxation beyond the upper cutoff frequency of 20 GHz, presumably due to subpicosecond translational and librational displacements of ions in the cage of their counterions. There is no evidence for orientational relaxation of long-lived ion pairs.
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Affiliation(s)
- Corinne Daguenet
- Ecole Polytechnique Fédérale de Lausanne, Institut des Sciences et Ingénerie Chimiques, CH-1015 Lausanne, Switzerland
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136
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Lang B, Angulo G, Vauthey E. Ultrafast Solvation Dynamics of Coumarin 153 in Imidazolium-Based Ionic Liquids. J Phys Chem A 2006; 110:7028-34. [PMID: 16737250 DOI: 10.1021/jp057482r] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dynamic Stokes shift of coumarin 153 has been measured in two room-temperature ionic liquids, 1-(3-cyanopropyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-propyl-3-methylimidazolium tetrafluoroborate, using the fluorescence up-conversion technique with a 230 fs instrumental response function. A component of about 10-15% of the total solvation shift is found to take place on an ultrafast time scale < 10 ps. The amplitude of this component is substantially less than assumed previously by other authors. The origin of the difference in findings could be partly due to chromophore-internal conformational changes on the ultrafast time scale, superimposed to solvation-relaxation, or due to conformational changes of the chromophore ground state in polar and apolar environments. First three-pulse photon-echo peak-shift experiments on indocyanine green in room-temperature ionic liquids and in ethanol indicate a difference in the inertial component of the early solvent relaxation of <100 fs.
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Affiliation(s)
- Bernhard Lang
- Department of Physical Chemistry, University of Geneva, Switzerland
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137
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Fujisawa T, Fukuda M, Terazima M, Kimura Y. Raman Spectroscopic Study on Solvation of Diphenylcyclopropenone and Phenol Blue in Room Temperature Ionic Liquids. J Phys Chem A 2006; 110:6164-72. [PMID: 16671688 DOI: 10.1021/jp057423d] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We investigated the solvation of several room temperature ionic liquids by Raman spectroscopy using diphenylcyclopropenone (DPCP) and phenol blue (PB) as probe molecules. We estimated acceptor numbers (AN) of room temperature ionic liquids by an empirical equation associated with the Raman band of DPCP assigned as a C=C stretching mode involving a significant C=O stretching character. According to the dependence of AN on cation and anion species, the Lewis acidity of ionic liquids is considered to come mainly from the cation charge. The frequencies and bandwidths of the C=O and C=N stretching modes of phenol blue are found to be close to those in conventional polar solvents such as methanol and dimethyl sulfoxide. The frequencies of these vibrational modes show similar dependence upon the electronic absorption band center as is observed in conventional liquid solvents. However, peculiar behavior was found in the Raman bandwidths and the excitation wavelength dependence of the C=N stretching mode in room temperature ionic liquids. Both the bandwidth of the C=N stretching mode and the extent of the excitation wavelength dependence of the Raman shift of the C=N stretching mode tend to decrease as the absorption band center decreases, in contrast to the case of conventional solvents. This anomaly is discussed in terms of the properties of room temperature ionic liquids.
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Affiliation(s)
- Tomotsumi Fujisawa
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
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138
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Jaye AA, Hunt NT, Meech SR. Temperature- and solvation-dependent dynamics of liquid sulfur dioxide studied through the ultrafast optical Kerr effect. J Chem Phys 2006; 124:024506. [PMID: 16422610 DOI: 10.1063/1.2145760] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The ultrafast dynamics of liquid sulphur dioxide have been studied over a wide temperature range and in solution. The optically heterodyne-detected and spatially masked optical Kerr effect (OKE) has been used to record the anisotropic and isotropic third-order responses, respectively. Analysis of the anisotropic response reveals two components, an ultrafast nonexponential relaxation and a slower exponential relaxation. The slower component is well described by the Stokes-Einstein-Debye equation for diffusive orientational relaxation. The simple form of the temperature dependence and the agreement between collective (OKE) and single molecule (e.g., NMR) measurements of the orientational relaxation time suggests that orientational pair correlation is not significant in this liquid. The relative contributions of intermolecular interaction-induced and single-molecule orientational dynamics to the ultrafast part of the spectral density are discussed. Single-molecule librational-orientational dynamics appear to dominate the ultrafast OKE response of liquid SO2. The temperature-dependent OKE data are transformed to the frequency domain to yield the Raman spectral density for the low-frequency intermolecular modes. These are bimodal with the lowest-frequency component arising from diffusive orientational relaxation and a higher-frequency component connected with the ultrafast time-domain response. This component is characterized by a shift to higher frequency at lower temperature. This result is analyzed in terms of a harmonic librational oscillator model, which describes the data accurately. The observed spectral shifts with temperature are ascribed to increasing intermolecular interactions with increasing liquid density. Overall, the dynamics of liquid SO2 are found to be well described in terms of molecular orientational relaxation which is controlled over every relevant time range by intermolecular interactions.
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Affiliation(s)
- Andrew A Jaye
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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139
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Endres F, Zein El Abedin S. Air and water stable ionic liquids in physical chemistry. Phys Chem Chem Phys 2006; 8:2101-16. [PMID: 16751868 DOI: 10.1039/b600519p] [Citation(s) in RCA: 680] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids are defined today as liquids which solely consist of cations and anions and which by definition must have a melting point of 100 degrees C or below. Originating from electrochemistry in AlCl(3) based liquids an enormous progress was made during the recent 10 years to synthesize ionic liquids that can be handled under ambient conditions, and today about 300 ionic liquids are already commercially available. Whereas the main interest is still focussed on organic and technical chemistry, various aspects of physical chemistry in ionic liquids are discussed now in literature. In this review article we give a short overview on physicochemical aspects of ionic liquids, such as physical properties of ionic liquids, nanoparticles, nanotubes, batteries, spectroscopy, thermodynamics and catalysis of/in ionic liquids. The focus is set on air and water stable ionic liquids as they will presumably dominate various fields of chemistry in future.
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Affiliation(s)
- Frank Endres
- Faculty of Natural and Materials Sciences, Clausthal University of Technology, Robert-Koch-Str. 42, 38678 Clausthal-Zellerfeld, Germany.
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140
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Shirota H, Castner EW. Why Are Viscosities Lower for Ionic Liquids with −CH2Si(CH3)3 vs −CH2C(CH3)3 Substitutions on the Imidazolium Cations? J Phys Chem B 2005; 109:21576-85. [PMID: 16853801 DOI: 10.1021/jp053930j] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
We have prepared novel room temperature ionic liquids (RTILs) with trimethylsilylmethyl (TMSiM)-substituted imidazolium cations and compared the properties of these liquids with those for which the TMSiM group is replaced by the analogous neopentyl group. The ionic liquids are prepared with both tetrafluoroborate (BF(4)(-)) and bis(trifluoromethylsulfonyl)imide (NTf(2)(-)) anions paired with the imidazolium cations. At 22 degrees C, the TMSiM-substituted imidazolium ILs have shear viscosities that are reduced by a factor of 1.6 and 7.4 relative to the alkylimidazolium ILs for the NTf(2)(-) and BF(4)(-) anions, respectively. To understand the effect of silicon substitution on the viscosity, the charge densities have been calculated by using density functional theory electronic structure calculations. The ultrafast intermolecular, vibrational, and orientational dynamics of these RTILs have been measured by using femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy (OHD-RIKES). The intermolecular dynamical spectrum provides an estimate of the strength of interactions between the ions in the RTILs, and provides a qualitative explanation for the observed reduction in viscosity for the silicon-substituted RTILs.
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Affiliation(s)
- Hideaki Shirota
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 610 Taylor Road, Piscataway, New Jersey 08854-8087, USA.
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141
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Shirota H, Castner EW. Physical Properties and Intermolecular Dynamics of an Ionic Liquid Compared with Its Isoelectronic Neutral Binary Solution. J Phys Chem A 2005; 109:9388-92. [PMID: 16866386 DOI: 10.1021/jp054664c] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this study, we address the following question about room-temperature ionic liquids (RTILs). Are the properties of a RTIL more dependent on the charges of the molecular ions or on the fact that the liquid is a complex mixture of two species, one or both of which are asymmetric? To address this question and to better understand the interactions and dynamics in RTILs, we have prepared the organic ionic liquid 1-methoxyethylpyridinium dicyanoamide (MOEPy(+)/DCA(-)) and compared this RTIL with the analogous isoelectronic binary solution, comprised of equal parts of 1-methoxyethylbenzene (MOEBz) and dicyanomethane (DCM). In essence, we have created a RTIL and a nearly identical neutral pair in which we have effectively turned off the charges. To understand the intermolecular interactions in both of these liquids, we have characterized the bulk density and shear viscosity. Using femtosecond optical Kerr effect spectroscopy, we have also characterized the intermolecular vibrational dynamics and diffusive reorientation. To verify that the shape, polarizability, and electronic structure of the RTIL ions and the components of the neutral pair are truly quite similar, we have carried out density functional theory calculations on the individual molecular ion and neutral species.
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142
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Shirota H, Funston AM, Wishart JF, Castner EW. Ultrafast dynamics of pyrrolidinium cation ionic liquids. J Chem Phys 2005; 122:184512. [PMID: 15918734 DOI: 10.1063/1.1893797] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
We have investigated the ultrafast molecular dynamics of five pyrrolidinium cation room temperature ionic liquids using femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The ionic liquids studied are N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P14+/NTf2-), N-methoxyethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P1EOE+/NTf2-), N-ethoxyethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide P1EOE+/NTf2-), N-ethoxyethyl-N-methylpyrrolidinium bromide P1EOE+, and N-ethoxyethyl-N-methylpyrrolidinium dicyanoamide P1EOE+/DCA-). For comparing dynamics among the five ionic liquids, we categorize the ionic liquids into two groups. One group of liquids comprises the three pyrrolidinium cations P14+, P1EOM+, and P1EOE+ paired with the NTf2- anion. The other group of liquids consists of the P1EOE+ cation paired with each of the three anions NTf2-, Br-, and DCA-. The overdamped relaxation for time scales longer than 2 ps has been fit by a triexponential function for each of the five pyrrolidinium ionic liquids. The fast ( approximately 2 ps) and intermediate (approximately 20 ps) relaxation time constants vary little among these five ionic liquids. However, the slow relaxation time constant correlates with the viscosity. Thus, the Kerr spectra in the range from 0 to 750 cm(-1) are quite similar for the group of three pyrrolidinium ionic liquids paired with the NTf2- anion. The intermolecular vibrational line shapes between 0 and 150 cm(-1) are fit to a multimode Brownian oscillator model; adequate fits required at least three modes to be included in the line shape.
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Affiliation(s)
- Hideaki Shirota
- Department of Chemistry & Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-8087, USA
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143
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Shirota H. Ultrafast Dynamics of Liquid Poly(ethylene glycol)s and Crown Ethers Studied by Femtosecond Raman-Induced Kerr Effect Spectroscopy. J Phys Chem B 2005; 109:7053-62. [PMID: 16851802 DOI: 10.1021/jp044125s] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Ultrafast molecular dynamics of liquid poly(ethylene glycol)s, tetra(ethylene glycol), penta(ethylene glycol), and poly(ethylene glycol) with the molecular weight of 600, and crown ethers, 12-crown-4 and 15-crown-5, have been investigated by means of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. Picosecond Kerr transients of poly(ethylene glycol)s and crown ethers are characterized by a biexponential function with the time constants of about 2 and 20 ps. Both the faster and slower time constants do not vary much among the five oligo(ethylene oxide)s. Femtosecond dynamics is discussed based on the Kerr (depolarized Raman) spectra obtained by Fourier transform deconvolution analysis of the high time resolution Kerr transients. The broad low-frequency band (0-200 cm(-1)) in the Kerr spectrum is analyzed by two Brownian oscillators. The spectral shapes of linear poly(ethylene glycol) and cyclic crown ether are very different. Both the low- and high-frequency Brownian oscillators for crown ethers show lower frequency and broader spectral features than those for poly(ethylene glycol)s. The comparison of the low-frequency spectra of poly(ethylene glycol)s and crown ethers shows that the low-frequency spectrum of 15-crown-5 is closer to that of poly(ethylene glycol)s than that of 12-crown-4 is. The difference of the low-frequency spectra between poly(ethylene glycol) and crown ether is discussed with the concepts of molecular conformation and liquid density. The features of the observed intramolecular vibrational bands are also correlated with the molecular conformations.
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Affiliation(s)
- Hideaki Shirota
- Department of General Systems Sciences, Graduate School of Arts & Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
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144
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Chakrabarty D, Chakraborty A, Seth D, Sarkar N. Effect of Water, Methanol, and Acetonitrile on Solvent Relaxation and Rotational Relaxation of Coumarin 153 in Neat 1-Hexyl-3-methylimidazolium Hexafluorophosphate. J Phys Chem A 2005; 109:1764-9. [PMID: 16833504 DOI: 10.1021/jp0460339] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The dynamics of solvent relaxation in ionic liquid (IL)-water, IL-methanol, and IL-acetonitrile mixtures have been investigated using steady state and picosecond time-resolved fluorescence spectroscopy. We have used Coumarin 153 (C-153) and 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF(6)]) as fluorescence probe and IL, respectively. The steady-state emission spectra showed that the gradual addition of cosolvents increases the polarity of the mixtures. In neat [hmim][PF(6)] and all IL-cosolvent mixtures, solvation occurs in two well-separated time regimes within the time resolution of our instrument. A substantial portion of the solvation has been missed due to the limited time resolution of our instrument. The gradual addition of cosolvents decreases the viscosity of the medium and consequently solvation time also decreases. The decrease in solvation time is more pronounced on addition of acetonitrile compared to water and methanol. The rotational relaxation time of the probe is also decreasing with gradual addition of the cosolvents. The decrease in viscosity of the solution is responsible for the decrease in the rotational relaxation time of the probe molecule.
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Affiliation(s)
- Debdeep Chakrabarty
- Department of Chemistry, Indian Institute of Technology, Kharagpur 721 302, WB, India
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145
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Zhu X, Farrer RA, Fourkas JT. Optical Kerr Effect Spectroscopy Using Time-Delayed Pairs of Pump Pulses with Orthogonal Polarizations. J Phys Chem B 2005; 109:8481-8. [PMID: 16851996 DOI: 10.1021/jp046761w] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We characterize in detail a recently introduced technique in which perpendicularly polarized pulses with controllable intensities and timing are used for the excitation step in optical Kerr effect spectroscopy. We examine the ratio of pump pulse intensities required to cancel the contribution of reorientational diffusion or of a Raman-active intramolecular vibration to the signal as a function of the delay time between excitation pulses. These results indicate that the signal can be described well as arising from the sum of independent third-order responses initiated by each pump pulse. This conclusion is further supported by using data obtained with a single pump pulse to model decays obtained with two pump pulses.
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Affiliation(s)
- Xiang Zhu
- Eugene F. Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, USA
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146
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Shirota H. Ultrafast molecular dynamics of liquid aromatic molecules and the mixtures with CCl4. J Chem Phys 2005; 122:44514. [PMID: 15740274 DOI: 10.1063/1.1840420] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The ultrafast molecular dynamics of liquid aromatic molecules, benzene, toluene, ethylbenzene, cumene, and 1,3-diphenylpropane, and the mixtures with CCl(4) have been investigated by means of femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. The picosecond Kerr transients of benzene, toluene, ethylbenzene, and cumene and the mixtures with CCl(4) show a biexponential feature. 1,3-Diphenylpropane and the mixtures with CCl(4) show triexponential picosecond Kerr transients. The slow relaxation time constants of the aromatic molecules and the mixtures with CCl(4) are qualitatively described by the Stoke-Einstein-Debye hydrodynamic model. The ultrafast dynamics have been discussed based on the Kerr spectra in the frequency range of 0-800 cm(-1) obtained by the Fourier transform analysis of the Kerr transients. The line shapes of the low-frequency intermolecular spectra located at 0-180 cm(-1) frequency range have been analyzed by two Brownian oscillators ( approximately 11 cm(-1) and approximately 45 cm(-1) peaks) and an antisymmetric Gaussian function ( approximately 65 cm(-1) peak). The spectrum shape of 1,3-diphenylpropane is quite different from the spectrum shapes of the other aromatic molecules for the low magnitude of the low-frequency mode of 1,3-diphenylpropane and/or an intramolecular vibration. Although the concentration dependences of the low- and intermediate-frequency intermolecular modes (Brownian oscillators) do not show a significant trend, the width of high-frequency intermolecular mode (antisymmetric Gaussian) becomes narrower with the higher CCl(4) concentration for all the aromatics mixtures with CCl(4). The result indicates that the inhomogeneity of the intermolecular vibrational mode in aromatics/CCl(4) mixtures is decreasing with the lower concentration of aromatics. The intramolecular vibrational modes of the aromatic molecules observed in the Kerr spectra are also shown with the calculation results based on the density functional theory.
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Affiliation(s)
- Hideaki Shirota
- Department of General Systems Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan.
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147
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Urahata SM, Ribeiro MCC. Single particle dynamics in ionic liquids of 1-alkyl-3-methylimidazolium cations. J Chem Phys 2005; 122:024511. [PMID: 15638602 DOI: 10.1063/1.1826035] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ionic dynamics in room temperature molten salts (ionic liquids) containing 1-alkyl-3-methylimidazolium cations is investigated by molecular-dynamics simulations. Calculations were performed with united atom models, which were used in a previous detailed study of the equilibrium structure of ionic liquids [S. M. Urahata and M. C. C. Ribeiro, J. Chem. Phys. 120, 1855 (2004)]. The models were used in a systematic study of the dependency of several single particle time correlation functions on anion size (F-, Cl-, Br-, and PF6-) and alkyl chain length (1-methyl-, 1-ethyl-, 1-butyl-, and 1-octyl-). Despite of large mass and size of imidazolium cations, they exhibit larger mean-square displacement than anions. A further detailed picture of ionic motions is obtained by using appropriate projections of displacements along the plane or perpendicular to the plane of the imidazolium ring. A clear anisotropy in ionic displacement is revealed, the motion on the ring plane and almost perpendicular to the 1-alkyl chain being the less hindered one. Similar projections were performed on velocity correlation functions, whose spectra were used to relate short time ionic rattling with the corresponding long time diffusive regime. Time correlation functions of cation reorientation and dihedral angles of the alkyl chains are discussed, the latter decaying much faster than the former. A comparative physical picture of time scales for distinct dynamical processes in ionic liquids is provided.
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Affiliation(s)
- Sérgio M Urahata
- Laboratório de Espectroscopia Molecular, Instituto de Química, Universidade de São Paulo CP 26077, CEP 05513-970, São Paulo, SP, Brazil
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148
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Chiappe C, Pieraccini D. Ionic liquids: solvent properties and organic reactivity. J PHYS ORG CHEM 2005. [DOI: 10.1002/poc.863] [Citation(s) in RCA: 948] [Impact Index Per Article: 49.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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149
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Krishnan M, Balasubramanian S. n-Heptane under Pressure: Structure and Dynamics from Molecular Simulations. J Phys Chem B 2004; 109:1936-46. [PMID: 16851178 DOI: 10.1021/jp046889d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Atomistic molecular dynamics simulations have been performed in the isothermal-isobaric ensemble to explore the phase behavior of n-heptane. Motivated by recent high-pressure spectroscopic experiments on n-heptane, the present work aims at understanding the liquid-solid and the alluded to solid-solid transitions upon increasing pressure. Starting from the stabilized solid phase at 300 K and 10 kbar, we have investigated the range of these two transitions by a gradual decrease and increase of pressure, respectively. Although the solid-liquid transition has clear signatures such as the formation of gauche defects along the molecular backbone, the present model does not show any sign of a first-order solid-solid transition at high pressures. However, interesting changes in the environment around methyl groups and in their dynamics are observed. These have been substantiated by calculations of the vibrational density of states obtained from a normal-mode analysis and from the simulation trajectory.
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Affiliation(s)
- M Krishnan
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560 064, India
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150
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Rajian JR, Hyun BR, Quitevis EL. Intermolecular Spectrum of Liquid Biphenyl Studied by Optical Kerr Effect Spectroscopy. J Phys Chem A 2004. [DOI: 10.1021/jp047415h] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Justin Rajesh Rajian
- Department of Chemistry and Biochemistry and Department of Physics, Texas Tech University, Lubbock, Texas 79409
| | - Byung-Ryool Hyun
- Department of Chemistry and Biochemistry and Department of Physics, Texas Tech University, Lubbock, Texas 79409
| | - Edward L. Quitevis
- Department of Chemistry and Biochemistry and Department of Physics, Texas Tech University, Lubbock, Texas 79409
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