Faculty Profiles - Ryo Kanzaki

Papers - Ryo Kanzaki

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Ryo Kanzaki, Hiroyuki Doi, Xuedan Song, Shota Hara, Shin-ichi Ishiguro, Yasuhiro Umebayashi . Acid-Base Property of N-Methylimidazolium-Based Protic Ionic Liquids Depending on Anion . The Journal of Physical Chemistry B 116 14146 - 14152 2012Acid-Base Property of N-Methylimidazolium-Based Protic Ionic Liquids Depending on AnionReviewed

Toshiyuki Takamuku, Hiroshi Wada, Chiemi Kawatoko, Takuya Shimomura, Ryo Kanzaki, Munetaka Takeuchi . Amide-induced phase separation of hexafluoroisopropanol-water mixtures depending on the hydrophobicity of amides . Physical Chemistry and Chemical Physics14 8335 - 8347 2012Amide-induced phase separation of hexafluoroisopropanol-water mixtures depending on the hydrophobicity of amidesReviewed

Xuedan SONG, Ryo KANZAKI, Shin-ichi ISHIGURO, Yasuhiro UMEBAYASHI . Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic Liquids . Analytical Sciences28 469 - 474 2012Physicochemical and Acid-base Properties of a Series of 2-Hydroxyethylammonium-based Protic Ionic LiquidsReviewed

Xuedan Song, Hiroshi Hamano, Babak Minofar, Ryo Kanzaki, Kenta Fujii, Yasuo Kameda, Shinji Kohara, Masayoshi Watanabe, Shin-ichi Ishiguro, Yasuhiro Umebayashi . Structural Heterogeneity and Unique Distorted Hydrogen Bonding in Primary Ammonium Nitrate Ionic Liquids Studied by High-Energy X-ray Diffraction Experiments and MD Simulations . The Journal of Physical Chemistry B116 2801 - 2813 2012Structural Heterogeneity and Unique Distorted Hydrogen Bonding in Primary Ammonium Nitrate Ionic Liquids Studied by High-Energy X-ray Diffraction Experiments and MD SimulationsReviewed

Kenta Fujii, Ryo Kanzaki, Toshiyuki Takamuku, Yasuo Kameda, Shinji Kohara, Mitsuhiro Kanakubo, Mitsuhiro Shibayama, Shin-ichi Ishiguro, Yasuhiro Umebayashi . Experimental evidences for molecular origin of low-Q peak in neutron X-ray scattering of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide ionic liquids . JOURNAL OF CHEMICAL PHYSICS135 ( 24 ) 244502 2011.12Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER INST PHYSICS

Short- and long-range liquid structures of [C(n)mIm(+)][TFSA(-)] with n = 2, 4, 6, 8, 10, and 12 have been studied by high-energy x-ray diffraction (HEXRD) and small-angle neutron scattering (SANS) experiments with the aid of MD simulations. Observed x-ray structure factor, S(Q), for the ionic liquids with the alkyl-chain length n > 6 exhibited a characteristic peak in the low-Q range of 0.2-0.4 angstrom (-1), indicating the heterogeneity of their ionic liquids. SANS profiles I-H(Q) and I-D(Q) for the normal and the alkyl group deuterated ionic liquids, respectively, showed significant peaks for n = 10 and 12 without no form factor component for large spherical or spheroidal aggregates like micelles in solution. The peaks for n = 10 and 12 evidently disappeared in the difference SANS profiles Delta I(Q) [= I-D(Q) - I-H(Q)], although that for n = 12 slightly remained. This suggests that the long-range correlations originated from the alkyl groups hardly contribute to the low-Q peak intensity in SANS. To reveal molecular origin of the low-Q peak, we introduce here a new function; x-ray structure factor intensity at a given Q as a function of r, S-Qpeak(r). The S-Qpeak(r) function suggests that the observed low-Q peak intensity depending on n is originated from liquid structures at two r-region of 5-8 and 8-15 angstrom for all ionic liquids examined except for n = 12. Atomistic MD simulations are consistent with the HEXRD and SANS experiments, and then we discussed the relationship between both variations of low-Q peak and real-space structure with lengthening the alkyl group of the C(n)mIm. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3672097]

DOI： 10.1063/1.3672097

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Toshiyuki Takamuku, Takuya Shimomura, Mai Tachikawa, Ryo Kanzaki . N,N-Dimethylformamideinduced phase separation of hexafluoroisopropanol- water mixtures . Physical Chemistry and Chemical Physics13 11222 - 11232 2011N,N-Dimethylformamideinduced phase separation of hexafluoroisopropanol- water mixturesReviewed

Hitoshi Kodamatani, Ryo Kanzaki, Takashi Tomiyasu, Keiitsu Saito, Yuriko Kono . DETERMINATION OF ORGANIC AND INORGANIC MERCURY SPECIES AS EMETINE DITHIOCARBAMATE COMPLEXES BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY WITH ELECTROGENERATED TRIS(2,2 '-BIPYRIDINE)RUTHENIUM(III) CHEMILUMINESCENCE DETECTION . ANALYTICAL LETTERS44 ( 17 ) 2769 - 2779 2011Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：TAYLOR & FRANCIS INC

A sensitive method for simultaneous determination of organic and inorganic mercury species has been developed and is presented in this study. The method is based on complex formation of mercury species with the emetine dithiocarbamate (emetine-CS(2)) ligand, HPLC separation, and tris(2,2'-bipyridine) ruthenium(III) chemiluminescence detection. The complexation reactions of the mercury species and emetine-CS(2) ligand occurred instantaneously upon the addition of emetine-CS(2) solution to the solution containing the mercury species. The complete separation of these complexes was achieved using an ODS column with 20mM NaH(2)PO(4)-acetonitrile (52:48, v/v) containing 30mM NaClO(4) as an ion-pair reagent. The calibration graphs of these complexes were linear in the range from 1-100 mu g/L. The detection limits were 0.27 mu g/L, 0.33 mu g/L, 0.39 mu g/L, and 0.17 mu g/L for methylmercury, ethylmercury, phenylmercury, and the mercury ion, respectively, at a signal-to-noise ratio of 3. The developed technique was validated by analyzing certified reference materials, CRM7402-a (cod fish, NMIJ) and CE464 (tuna fish, ERM), in combination with sonication-assisted acid leaching and liquid-liquid extraction. The emetine-CS2 ligand has been used for extraction, separation, and detection of mercury species. The results determined using the proposed method were in good agreement with the values of the certified reference materials. The MeHg(+) and EtHg(+) recoveries for the spiked samples were found to be almost 100%.

DOI： 10.1080/00032719.2011.565442

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Shin-ichi Ishiguro, Yasuhiro Umebayashi, Ryo Kanzaki, Kenta Fujii . Structure, solvation, and acid-base property in ionic liquids . PURE AND APPLIED CHEMISTRY82 ( 10 ) 1927 - 1941 2010.10Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：INT UNION PURE APPLIED CHEMISTRY

Ionic liquids (ILs) are expected to have specific properties as solvents for chemical reactions in view of solution chemistry. Among physicochemical properties, liquid structure, acid-base, and electron-pair donating and accepting abilities of solvent play a crucial role in ion-solvation and acid-base, metal-ion complexation, and electrochemical reactions. Various types of ILs have been developed, and among others, the bis(trifluoromethanesulfonyl)amide (TFSA-)-based ILs are extensively used. TFSA- is a flexible molecule to give two stable conformers, cis (C1) and trans (C2), which are present in equilibrium in the liquid state. The conformational equilibrium shifts upon solvation to the metal ion. This is quantitatively studied to obtain thermodynamic parameters of conformational change from C2 to Cl in the bulk and in the solvation sphere of the lithium ion. On the other hand, with ethylammonium nitrate (EAN), a typical protic IL, it is revealed that the ammonium group is hydrogen-bonded with three nitrate ions to form a heterogeneous liquid structure. The solvent acid-base property of EAN and acid dissociation reaction in EAN have been quantitatively revealed, and the results will be discussed in comparison with those in normal molecular solvents.

DOI： 10.1351/PAC-CON-09-10-28

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神﨑亮 . イオン液体の酸塩基性とpH測定 . Electrochemistry78 ( 8 ) 687 - 692 2010.8Invited Reviewed

Ryo Kanzaki, Xuedan Song, Yasuhiro Umebayashi, Shin-ichi Ishiguro . Thermodynamic Study of the Solvation States of Acid and Base in a Protic Ionic Liquid, Ethylammonium Nitrate, and Its Aqueous Mixtures . CHEMISTRY LETTERS39 ( 6 ) 578 - 579 2010.6Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：CHEMICAL SOC JAPAN

Ethylammonium nitrate (EAN) is a typical protic ionic liquid (PIL) known for a long time. In order to investigate acid-base reaction mechanisms in PIL, thermodynamic quantities of a reaction, which corresponds to autoprotolysis in amphoteric solvents, has been determined in neat EAN. Unlike H3O+ and OH- in water, proton donor and acceptor species in EAN are both neutral; this makes acid-base reaction mechanisms in EAN distinct from that in water. EAN-water mixtures have also been studied.

DOI： 10.1246/cl.2010.578

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Toshiyuki Takamuku, Miho Tanaka, Takunosuke Sako, Takuya Shimomura, Kenta Fujii, Ryo Kanzaki, Munetaka Takeuchi . Solvation of the Amphiphilic Diol Molecule in Aliphatic Alcohol-Water and Fluorinated Alcohol-Water Solutions . JOURNAL OF PHYSICAL CHEMISTRY B114 ( 12 ) 4252 - 4260 2010.3

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

We investigated the solvation properties of aqueous Solutions of aliphatic alcohols and fluorinated alcohols. These included ethanol (EtOH), 2-propanol (2-PrOH), 2,2,2-trifluoroethanol (TFE), and 1, 1, 1,3,3,3-hexafluoro-2-propanol (HFIP). The amphiphilic diol, 1,4-pentanediol (1,4-PD), was used as the solute to probe solvation properties at the molecular level. Small-angle neutron scattering (SANS) experiments revealed that the inherent microheterogeneity or HFIP-water binary Solutions was significantly enhanced by addition of 1,4-PD. In contrast, the addition of 1,4-PD to EtOH-, 2-PrOH-, and TFE-water solutions hardly changed the mixing state. Molecular dynamics simulations were used to obtain the spatial distribution functions for the oxygen atom of water molecules and the carbon and fluorine atoms of alcohol molecules around 1,4-PD. Of the alcohols studied, these spatial distributions illustrated that HFIP molecules formed the strongest hydrophobic solvation shell around the hydrocarbons of 1,4-PD. This preferential solvation of 1,4-PD by HFIP leads to enhancement of HFIP Clusters ill the Solutions. (13)C NMR and infrared spectroscopic measurements on 1,4-PD ill the different alcohol-water Solutions suggested that the number of water molecules around the hydrocarbons of 1,4-PD decreased in aliphatic alcohol-water solutions. Additionally, HFIP Molecules are thought to strongly interact with the hydrocarbons of 1,4-PD in HFIP-water solutions.

DOI： 10.1021/jp9097414

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Ryo Kanzaki, Takushi Mitsugi, Shuhei Fukuda, Kenta Fujii, Munetaka Takeuchi, Yasufumi Soejima, Toshiyuki Takamuku, Toshio Yamaguchi, Yasuhiro Umebayashi, Shin-ichi Ishiguro . Ion-ion interaction in Room Temperature Ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate studied by large angle X-ray scattering experiment and molecular dynamics simulations . Journal of Molecular Liquids147 77 - 82 2009Ion-ion interaction in Room Temperature Ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate studied by large angle X-ray scattering experiment and molecular dynamics simulationsReviewed

Yasuhiro Umebayashi, Takushi Mitsugi, Kenta Fujii, Shiro Seki, Kazumi Chiba, Hideo Yamamoto, Jpse N. Canongia Lopes, Agilio A. H. Padua, Munetaka Takeuchi, Ryo Kanzaki, Shin-ichi Ishiguro . Raman Spectroscopic Study, DFT Calculations and MD Simulations on the Conformational Isomerism of N-Alkyl-N-methylpyrrolidinium Bis-(trifluoromethanesulfonyl) Amide Ionic Liquids . The Journal of Physical Chemistry B113 4338 - 4346 2009Raman Spectroscopic Study, DFT Calculations and MD Simulations on the Conformational Isomerism of N-Alkyl-N-methylpyrrolidinium Bis-(trifluoromethanesulfonyl) Amide Ionic LiquidsReviewed

Yasuhiro Umebayashi, Wan-Lin Chung, Takushi Mitsugi, Shuhei Fukuda, Munetaka Takeuchi, Kenta Fujii, Toshiyuki Takamuku, Ryo Kanzaki, Shin-ichi Ishiguro . Liquid Structure and the Ion-Ion Interactions of Ethylammonium Nitrate Ionic Liquid Studied by Large Angle X-Ray Scattering and Molecular Dynamics Simulations . Journal of Computer Chemistry, Japan7 125 - 134 2008.11Liquid Structure and the Ion-Ion Interactions of Ethylammonium Nitrate Ionic Liquid Studied by Large Angle X-Ray Scattering and Molecular Dynamics SimulationsReviewed

Ryo Kanzaki, Kuniaki Uchida, Xuedan Song, Yasuhiro Umebayashi, Shin-ichi Ishiguro . Acidity and Basicity of Aqueous Mixtures of a Protic Ionic Liquid, Ethylammonium Nitrate . ANALYTICAL SCIENCES24 ( 10 ) 1347 - 1349 2008.10Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN SOC ANALYTICAL CHEMISTRY

Ethylammonium nitrate (EAN) is composed of C2H5NH3+ and NO3- ions, which behave as an acid and a base, respectively. The ionic liquid thus involves small amounts of C2H5NH2 and HNO3 molecules owing to proton transfer from C2H5NH3+ to NO3-. The equilibrium constant K-s (= [C2H5NH2][HNO3]), which corresponds to the autoprotolysis constant of water, was obtained to be ca. 10(-10) mol(2) dm(-6) by potentiometry using an ion-selective field-effect transistor and hydrogen electrodes at 298 K. The value indicates that C2H5NH2 and HNO3 molecules of ca. 10(-5) mol dm(-3) are involved in neat EAN. On the other hand, in an EAN-water mixture, a water molecule behaves as a base. The apparent pK(s) value was determined in EAN-water mixtures of various solvent compositions. Interestingly, the pK(s) value is remained at 10.5 in mixtures over the range of an EAN mole fraction of 0.05 - 0.9. The value is close to the pKa of C2H5NH2, or the acid-dissociation constant of C2H5NH3+, in aqueous solution. This implies that the reaction C2H5NH3+ + H2O -> C2H5NH2 + H3O+ is responsible for the pK(s) over a wide range of solvent composition. The pK(s) value in neat EAN is thus slightly smaller than that in the mixtures, implying that H3O+ is a stronger acid than HNO3 in an EAN solution, unlike water.

DOI： 10.2116/analsci.24.1347

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Shuhei Fukuda, Munetaka Takeuchi, Kenta Fujii, Ryo Kanzaki, Toshiyuki Takamuku, Kazumi Chiba, Hideo Yamamoto, Yasuhiro Umebayashi, Shin-ichi Ishiguro . Liquid structure of N-butyl-N-methylpyrrolidinium bis-(trifluoromethanesulfonyl) amide ionic liquid studied by large angle X-ray scattering and molecular dynamics simulations . JOURNAL OF MOLECULAR LIQUIDS143 ( 1 ) 2 - 7 2008.9Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Large angle X-ray scattering of the N-butyl-N-methylpyrrolidinium bis-(trifluoromethanesulfony) amide (P-14*TFSA(-)) ionic liquid was measured at 298 K. The total interference function i(LAXS)(s) and the total pair correlation function G(LAXS)(r) were successfully obtained. The i(LAXS)(s) was analyzed in terms of the intramolecular geometries of the conformational isomers of the P-14* and TFSA(-) ions based on the crystal structures, s the inter-molecular correlation function G(inter)(LAXS)(r) and the inter-molecular radial distribution function as the form D-inter(LAXS)(r)-4 pi r(2)rho(0) were evaluated. With G(inter)(LAXS)(r)-4 pi r(2)rho(0). the inter-molecular correlation peaks at 3.5. 4.5 and 5-6 angstrom evidently appeared as the short range interaction, while considerable long range interactions were found as the broad peaks at 10 and 15 angstrom. Molecular dynamics simulations of the ionic liquid based on the effective pairwise potentials were carried out. The X-ray total interference function derived from the MD simulations i(MD)(S) was in agreement with the experimental one. According to the inter-molecular partial atom-atom correlation functions from MD simulations, the observed peaks at 3.5, 4.5 and 5-6 angstrom can be predominantly ascribed to the closest atom-atom correlations between the P-14* and TFSA(-) ions such as C...O and C...F In the inter-molecular partial atom-atom correlation function between terminal methyl carbons of the butyl chain in the P-14* ion. a peak at 4.0 angstrom was found as the inter-molecular correlation, suggesting that the ionic liquid shows an alkyl chain aggregation, which is similar to that observed for 1-alkyl-3-methylmidazolium ionic liquids. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2008.02.012

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Kenta Fujii, Yasufumi Soejima, Yasuhiro Kyoshoin, Shuhei Fukuda, Ryo Kanzaki, Yasuhiro Umebayashi, Toshio Yamaguchi, Shin-ichi Ishiguro, Toshiyuki Takamuku . Liquid structure of room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis-(trifluoromethanesulfonyl) imide . JOURNAL OF PHYSICAL CHEMISTRY B112 ( 14 ) 4329 - 4336 2008.4Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The liquid structure of 1-ethyl-3-methylimidazolium bis-(trifluoromethanesulfonyl) imide (EMI+TFSI-) has been studied by means of large-angle X-ray scattering (LAXS), H-1, C-13, and F-19 NMR, and molecular dynamics (MD) simulations. LAXS measurements show that the ionic liquid is highly structured with intermolecular interactions at around 6, 9, and 15 angstrom. The intermolecular interactions at around 6, 9, and 15 angstrom are ascribed, on the basis of the MD simulation, to the nearest neighbor EMI+...TFSI- interaction, the EMI+...EMI+ and TFSI-...TFSI- interactions, and the second neighbor EMI+...TFSI- interaction, respectively. The ionic liquid involves two conformers, C-1 (cis) and C-2 (trans), for TFSI-, and two conformers, planar cis and nonplanar staggered, for EMI+, and thus the system involves four types of the EMI+...TFSI- interactions in the liquid state by taking into account the conformers. However, the EMI+...TFSI- interaction is not largely different for all combinations of the conformers. The same applies also to the EMI+...EMI+ and TFSI-...TFSI- interactions. It is suggested from the C-13 NMR that the imidazolium C-2 proton of EMI+ strongly interacts with the O atom of the -SO2(CF3) group of TFSI-. The interaction is not ascribed to hydrogen-bonding, according to the MD simulation. It is shown that the liquid structure is significantly different from the layered crystal structure that involves only the nonplanar staggered EMI+ and C-1 TFSI- conformers.

DOI： 10.1021/jp7105499

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Kenta Fujii, Shiro Seki, Shuhei Fukuda, Ryo Kanzaki, Toshiyuki Takamuku, Yasuhiro Ulmebayashi, Shin-ichi Ishiguro . Anion conformation of low-viscosity room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(fluorosulfonyl) imide . JOURNAL OF PHYSICAL CHEMISTRY B111 ( 44 ) 12829 - 12833 2007.11Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

Anion conformation of a low-viscosity room-temperature ionic liquid 1-ethyl-3-methylimidazolium his(fluorosulfonyl) imide (EMI+FSI-) has been studied by Raman spectra and theoretical DFT calculations. Three strong Raman bands were found at 293, 328, and 360 cm(-1), which are ascribed to the FSI- ion. These Raman bands show significant temperature dependence, implying that two FSI- conformers coexist in equilibrium. This is supported by theoretical calculations that the FSI- ion is present as either C-2 (trans) or C-1 (cis) conformer; the former gives the global minimum, and the latter has a higher SCF energy of about 4 W mol(-1). Full geometry optimizations followed by normal frequency analyses show that the observed bands at 293, 328, and 360 cm(-1) are ascribed to the Q, conformer. The corresponding vibrations at 305, 320, and 353 cm(-1) were extracted according to deconvolution of the observed Raman bands in the range 280-400 cm(-1) and are ascribed to the C-2 conformer. The enthalpy Delta H degrees of conformational change from C-2 to C-1 was experimentally evaluated to be ca. 4.5 W mol(-1), which is in good agreement with the predicted value by theoretical calculations. The bis(ti-ifluoromethanesulfonyl) imide anion (TFSI-) shows a conformational equilibrium between C-1 and C-2 analogues (Delta H degrees = 3.5 kJ mol(-1)). However, the profile of the potential energy surface of the conformational change for FSI- (the F-S-N-S dihedral angle) is significantly different from that for TFSI- (the C-S-N-S dihedral angle).

DOI： 10.1021/jp074325e

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Mitsunori Asada, Takushi Mitsugi, Kenta Fujii, Ryo Kanzaki, Yasuhiro Umebayashi, Shin-Ichi Ishiguro . Vibrational spectroscopy and molecular orbital calculations of N,N-dimethylacrylamide and N,N-dimethylpropionamide - Conformational equilibrium in the liquid state . JOURNAL OF MOLECULAR LIQUIDS136 ( 1-2 ) 138 - 146 2007.11Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Molecular vibrations of N,N-dimethylacrylamide (DMAA) and N,N-dimethylpropionamide (DMPA) in the liquid state were studied by means of Raman and IR spectra over the wide frequency range. It has been established in our previous work that DMPA involves two rotational isomers within its propionyl CH3-CH2-C(=O)- group. In the present work, it is revealed that, like DMPA, DMAA also involves two rotational isomers, the planar cis and nonplanar staggered ones, within its acryl CH2=CH-C(=O)- group. The terminal methylene carbon of the acryl group locates cis to the 0 atom within the amide O=C-N plane (the planar cis conformer) or above the amide plane (the nonplanar staggered conformer). This is well supported by theoretical MO calculations. Torsion potential energy surfaces (PES) for the C-C-C-O dihedral angle 0 of the acryl group show that a global minimum appears at ca. theta=0 degrees (the planar cis conformer) and a local minimum at ca. theta=130 degrees (the nonplanar staggered conformer). The geometry optimization followed by normal frequency analyses showed that theoretical Raman and IR bands for the conformers satisfactorily reproduce the observed ones. The enthalpy for the conformational change from the planar cis conformer to the nonplanar staggered one was experimentally evaluated by analyzing the integrated intensity changes of the bands in the range 700-800 cm(-1). The value thus obtained for the acryl group of DMAA is ca. 9 kJ mol(-1), which is significantly higher than the corresponding value for the propionyl group of DMPA (5 kJ mol(-1)). (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2007.02.007

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Yasuhiro Umebayashi, Takushi Mitsugi, Shuhei Fukuda, Takao Fujimori, Kenta Fujii, Ryo Kanzaki, Munetaka Takeuchi, Shin-Ichi Ishiguro . Lithium ion solvation in room-temperature ionic liquids involving bis(trifluoromethanesulfonyl) imide anion studied by Raman Spectroscopy and DFT calculations . JOURNAL OF PHYSICAL CHEMISTRY B111 ( 45 ) 13028 - 13032 2007.11Reviewed

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER CHEMICAL SOC

The solvation structure of the lithium ion in room-temperature ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EMI+TFSI-) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP+TFSI-) has been studied by Raman spectroscopy and DFT calculations. Raman spectra of EMI+TFSI- and BMP+TFSI- containing Li+TFSI- over the range 0.144-0.589 and 0.076-0.633 mol dm(-3), respectively, were measured at 298 K. A strong 744 cm(-1) band of the free TFSI- ion in the bulk weakens with increasing concentration of the lithium ion, and it revealed by analyzing the intensity decrease that the two TFSI- ions bind to the metal ion. The lithium ion may be four-coordinated through the 0 atoms of two bidentate TFSI- ions. It has been established in our previous work that the TFSI- ion involves two conformers of C-1 (cis) and C-2 (trans) symmetries in equilibrium, and the dipole moment of the C-1 conformer is significantly larger than that of the C-2 conformer. On the basis of these facts, the geometries and SCF energies of possible solvate ion clusters [Li(C-1-TFSI-)(2)](-), [Li(C-1-TFSI-)(C-2-TFSI-)](-))]-, and [Li(C-2-TFS)(-))(2)](-) were examined using the theoretical DFT calculations. It is concluded that the C-1 conformer is more preferred to the C, conformer in the vicinity of the lithium ion.

DOI： 10.1021/jp076869m

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Papers - Ryo Kanzaki