Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/bcsj.20220221

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s44211-022-00121-7

researchmap

Other Link： https://link.springer.com/article/10.1007/s44211-022-00121-7/fulltext.html

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.molliq.2022.118705

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcb.1c04693

researchmap

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Singapore  

DOI： 10.1007/978-981-33-6668-8

researchmap

Other Link： http://link.springer.com/content/pdf/10.1007/978-981-33-6668-8

Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry ({RSC})  

DOI： 10.1039/D0CP04898D

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcb.0c08021

researchmap

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcb.0c04078

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Molecular dynamics simulations of ionic liquids composed of N-propyl-N-methylpyrrolidinium cation ([pmpyro](+)) with (CF3SO2)(2)N- ([TFSA](-)), (FSO2)(2)N- ([FSA](-)), CF3SO3-, CF3CO2- and PF6- anions sandwiched by two charged graphene sheets show that the liquid structures near graphene sheets depend strongly on anion. Long-range charge ordering structures were observed when the ionic liquids were sandwiched with charged graphene sheets. Although the magnitude of the oscillation of cation and anion densities near charged graphene sheets is enhanced by the increase of the charges on the graphene sheets, the range of the charge-ordering structures from the graphene sheets does not largely change. The ranges of the charge-ordering structures from charged graphene sheets observed in the [pmpyro][TFSA], [pmpyro][FSA], [pmpyro][CF3SO3], [pmpyro][CF3CO2] and [pmpyro][PF6] ionic liquids are approximately 40, 80, 60, 60 and 100 angstrom, respectively.

DOI： 10.1002/batt.201900197

Web of Science

researchmap

Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/batt.201900197

Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Analytical Chemistry  

DOI： 10.2116/bunsekikagaku.69.271

researchmap

Publishing type：Research paper (scientific journal)   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/denkikagaku.20-fe0012

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpclett.0c00906

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acs.jpcc.9b10770

researchmap

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

High ionic carrier mobilities are important for the electrolyte solutions used in high-performance batteries. Based on the functional sharing concept, we fabricated mixed electrolytes consisting of solvate ionic liquids (SIL), which are highly concentrated solution electrolyte, and the non-coordinating low-viscosity dilution solvent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE). We investigated the thermal, transport, and static properties of electrolytes with different ratios of SIL to HFE. In particular, the interactions between the SILs and HFE and static correlations of the coordinating (ether-based molecules), non-coordinating (HFE), and carrier ionic species (lithium salt) were clarified by applying the excess density concept. Ether molecules always formed strong complexes with lithium cations regardless of the absence or presence of HFE. The repulsion force between the SILs and HFE was strongly affected by lithium salt concentration. From our results, we proposed dissociation/association models for these electrolyte systems.

DOI： 10.1039/c9ra04797b

Web of Science

researchmap

Publishing type：Research paper (scientific journal)  

© 2019 American Chemical Society. In a previous work, we have found that the pseudo-protic ionic liquid Nmethylimidazolium acetate, [C1HIm][OAc] or [Hmim][OAc], mainly consists of the electrically neutral molecular species N-methylimidazole, C1Im, and acetic acid, AcOH, even though the mixture has significant ionic conductivity. This system was revisited by employing isotopic substitution Raman spectroscopy (ISRS) and pulsed field gradient (PFG) NMR self-diffusion measurements. The ISRS and PFG-NMR results obtained fully confirm our earlier findings. In particular, the self-diffusion coefficient of the hydroxyl hydrogen atom in AcOH is identical to that of the methyl hydrogen atoms within the experimental uncertainty, consistent with very little ionization. Therefore, a proton conduction mechanism similar to the Grotthuss mechanism for aqueous acid solutions is postulated to be responsible for the observed electrical conductivity. Laity resistance coefficients (rij) are calculated from the transport properties, and the negative values obtained for the like-ion interactions are consistent with the pseudo-ionic liquid description, that is, the mixture is indeed a very weak electrolyte. The structure and rotational dynamics of the mixture were also investigated using high-energy X-ray total scattering experiments, molecular dynamics simulations, and dielectric relaxation spectroscopy. Based on a comparison of activation energies and the well-known linear free energy relationship between the kinetics and thermodynamics of autoprotolysis, we propose for [C1HIm][OAc] a Grotthus-type proton conduction mechanism involving fast AcOH/AcO- rotation as a decisive step.

DOI： 10.1021/acs.jpcb.9b03185

Web of Science

Scopus

PubMed

researchmap

Publishing type：Research paper (scientific journal)  

Neutron diffraction measurements have been carried out on 10 mol % LiTFSA (TFSA: bis(trifluoromethylsulfonil)amide) solutions in methanol-d4 and 2-propanol-d8 to obtain information on the solvation structure of Li+. The detailed coordination structure of solvent molecules within the first solvation shell of Li+ was determined through the least-squares fitting analysis of the difference function between normalized scattering cross sections observed for 6Li/7Li isotopically substituted sample solutions. The nearest-neighbor Li+···O distance and coordination number determined for the 10 mol % LiTFSA-methanol-d4 solution are rLiO = 1.98 ± 0.02 Å and nLiO = 3.8 ± 0.6, respectively. In the 2-propanol-d8 solution, it has been revealed that 2-propanol-d8 molecules within the first solvation shell of Li+ take at least two different coordination geometries with the intermolecular nearest-neighbor Li+···O distance of rLiO = 1.93 ± 0.04 Å. The Li+···O coordination number, nLiO = 3.3 ± 0.3, is determined. Ion-pair formation in the LiTFSA-methanol and LiTFSA-2-propanol solutions has been investigated by the attenuated total reflection infrared spectroscopic method. Mole fractions of free, Li+-bound, and aggregated TFSA- are derived from the peak deconvolution analysis of vibrational bands observed for TFSA-.

DOI： 10.1021/acs.jpcb.9b03477

Web of Science

Scopus

PubMed

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley Online Library  

The development of new electrolytes for lithium-sulfur (Li-S) batteries is important. Electrolytes based on 1:1 glyme:Li+ complexes can be locally destroyed to form free glyme during charge/discharge cycles. Free glyme can cause Li2Sx dissolution, which is a major factor in Li-S battery degradation. To decrease the local generation of free glyme, the glyme:Li+ electrolytes with higher proportions of Li salts are developed to control the Li2Sx dissolution into the electrolyte. The chemical solubility of Li2S8 and the charge/discharge properties of Li-S cells are investigated by varying the glyme:Li salt molar ratio. Nonequimolar (high Li salt concentration) glyme:Li salt mixture electrolytes directly suppress the Li2S8 dissolution and improve the charge/discharge properties (cycling and coulombic efficiency) of Li-S cells. The electrolyte composition can control the chemical stability of reactive intermediates at the Li2Sx electrode and provide high-performance Li-S cells for next-generation batteries.

DOI： 10.1002/ente.201900197

Web of Science

researchmap

DOI： 10.1246/bcsj.20180283

Web of Science

researchmap

Publishing type：Research paper (scientific journal)  

© 2018 Elsevier B.V. The electrochemical property of a silicon electrode in a half-cell was investigated using the mixture of monoglyme-based solvents and lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) with 2:1 stoichiometry. The solvents used in this study are monoglyme (G1), 1,2-diethoxyethane (DEE), 1,2-dibutoxyethane (DBE), and 1,2-dimethoxypropane (P-G1). When Li (DEE)2 or Li(P-G1)2 was used, the cell retained ca. 20% capacity at a rate of 3 C, while the other samples showed almost no capacity under the same conditions. Raman spectroscopy measurement revealed that Li+ exists as two forms in the mixture, that is, a solvent shared ion pair (SSIP) [Li+ ··· solvent ··· TFSA–] and a contact ion pair (CIP) [Li+ ··· TFSA–]. According to the spectroscopic analysis, SSIP is the dominant species for Li (DEE)2 and Li(P-G1)2, and CIP for Li (G1)2 and Li (DBE)2. The order of the rate property was Li(P-G1)2 ∼ Li (DEE)2 > Li (DBE)2 ∼ Li (G1)2, which is almost consistent with the stability of free energy levels of Li+ in the respective monoglymes against CIP Li+ ··· TFSA– evaluated from the Raman spectra.

DOI： 10.1016/j.matchemphys.2018.12.058

Web of Science

Scopus

researchmap

DOI： 10.2116/analsci.18P407

Web of Science

researchmap

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

To elucidate the properties of binary system of room temperature ionic liquids (RTILs), we measured and compared the temperature dependence of densities, viscosities, and refractive indices of seven binary RTILs as well as neat RTILs. The observed densities, viscosities, and refractive indices of the binary systems showed intermediate properties between those of two starting RTILs. The values observed for the binary RTILs were only deviated from the values estimated based on the data of neat RTILs (+/- 0.5%), and this deviation depended on both the combination of RTILs and the structures of the cation/anion. These results indicate that the properties of RTILs can be easily tuned by mixing RTILs depending on their applications.

DOI： 10.1021/acs.jced.8b00334

Web of Science

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/acs.jpcb.8b09439

Web of Science

researchmap

DOI： 10.1246/bcsj.20180205

Web of Science

researchmap

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

DOI： 10.1021/acs.jpcc.8b06251

PubMed

researchmap

Language：English   Publishing type：Part of collection (book)   Publisher：Royal Society of Chemistry  

New electrochemical application using room-temperature ionic liquids (ILs) are introduced, such as lithium secondary batteries, electrochemical double layer capacitors, and novel types of electrical devices for sustainable and renewal energy society. ILs have so many combinations, owing to many cation/anion species. In this chapter, we introduce properties from fundamental (general and special physicochemical properties) to electrochemical applications of ILs. We also discuss importance of molecular design and application target of ILs.

DOI： 10.1039/9781788011839-00365

Scopus

researchmap

Publishing type：Research paper (scientific journal)  

© The Author(s) 2018. To investigate physicochemical relationships between ionic radii, valence number and cationic metal species in electrolyte solutions, propylene carbonate with Li[N(SO2CF3)2], Na[N(SO2CF3)2], Mg[N(SO2CF3)2]2 and Ca[N(SO2CF3)2]2 were prepared. The temperature dependence of density, viscosity, ionic conductivity (AC impedance method) and self-diffusion coefficient (pulsed-gradient spin-echo nuclear magnetic resonance) was measured. The effects of cationic radii and cation valence number on the fluidity and transport properites (conductivity and self-diffusion coefficient) were analyzed.

DOI： 10.1149/2.0081803jes

Web of Science

Scopus

researchmap

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

Isotropic Raman scattering and time-of-flight neutron diffraction measurements were carried out for concentrated LiTFSA-EC solutions to obtain structural insight on solvated Li+ as well as the structure of contact ion pair, Li+center dot center dot center dot TFSA(-), formed in highly concentrated EC solutions. Symmetrical stretching vibrational mode of solvated Li+ and solvated Li+center dot center dot center dot TFSA(-) ion pair were observed at nu = 168-177 and 202-224 cm(-1), respectively. Detailed structural properties of solvated Li+ and Li+center dot center dot center dot TFSA(-) contact ion pair were derived from the least-squares fitting analysis of first-order difference function, Delta(Li)(Q), between neutron scattering cross sections observed for Li-6/Li-7 isotopically substituted 10 and 25 mol % *LiTFSA-ECd4 solutions. It has been revealed that Li+ in the 10 mol % LiTFSA solution is fully solvated by ca. 4 EC molecules. The nearest neighbor Li+center dot center dot center dot O(EC) distance and Li+center dot center dot center dot(EC)=C(EC) bond angle are determined to be 1.90 +/- 0.01 angstrom and 141 +/- 1 degrees, respectively. In highly concentrated 25 mol % LiTFSA-EC solution, the average solvation number of Li+ decreases to ca. 3 and ca. 1.5. TFSA(-) are directly contacted to Li+. These results agree well with the results of band decomposition analyses of isotropic Raman spectra for intramolecular vibrational modes of both EC and TFSA(-).

DOI： 10.1021/acs.jpcb.7b10933

Web of Science

researchmap

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

The solvation states of the sodium ion (Na+) and the tetraphenylborate ion (BPh4-) in 3-methylpyridine (3MP) and its mixture with deuterium oxide ((DO)-O-2) were investigated by Raman spectroscopy and DFT calculations. Raman spectra observed for the 3MP solutions systematically varied with increase in the amount of NaBPh4; the Raman band at 633 cm(-1) weakened and that at 639 cm(-1) strengthened with increase in the salt concentration. According to DFT calculations, the former was assigned to the 3MP molecule in the bulk and the latter to that bound to the Na+ ion. The number of 3MP molecules bound to Na+, n, was estimated to be 6.1, that is, a [Na(3MP)(6)](+) complex was formed in the 3MP/NaBPh4 solution. On the other hand, n was estimated to be 1.6 in the D2O/3MP/NaBPh4 mixtures with chi(3mp) = 0.50, where chi(3mp) denotes the mole fraction of 3MP in the D2O/3MP mixtures. Furthermore, both integrated intensities at 633 cm(-1) (free 3MP) and 640 cm(-1) (hydrated 3MP by D2O) were almost independent of the salt concentration in the case of D(2)OI3MP mixtures with chi(3mp) = 0.09. Additionally, the position of the other Raman bands at 609, 616, 626, and 672 cm(-1), arising from BPh4-, were almost independent of chi(3mp) between 1 and 0.09. These results suggest that Na+ is preferentially solvated with D2O, whereas BPh4- is preferentially solvated with 3MP in such mixtures. 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2017.10.006

Web of Science

researchmap

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

DOI： 10.5796/electrochemistry.85.680

CiNii Article

researchmap

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

The electrochemical properties of a sulfur positive electrode in equimolar glyme-Li salt mixtures were investigated. Cyclic voltammograms indicated that the insertion of Li into the sulfur/carbon composite electrode took place over at least three steps during the reduction process. In contrast, the broad anodic current suggested that the electrode kinetics for the extraction of Li were relatively slow. Stable charge-discharge operation of the Li-S cell consisting of a Li negative electrode with [Li(triglyme)][bis(trifluoromethanesulfonyl)amide] as the electrolyte was achieved at 800 cycles. This indicates that dissolution of Li2Sx into the electrolyte was effectively suppressed in this system. (C) The Electrochemical Society of Japan, All rights reserved.

DOI： 10.5796/electrochemistry.85.680

Web of Science

researchmap

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

The interactions of glymes with alkali or alkaline earth metal cations depend strongly on the metal cations. For example, the stabilization energies (E-form) calculated for the formation of cation-triglyme (G3) complexes with Li+, Na+, K+, Mg2+, and Ca2+ at the MP2/6-311G** level were -95.6, -66.4, -52.5, -255.0, and -185.0 kcal mol(-1), respectively, and those for the cation-tetraglyme (G4) complexes were -107.7, -76.3, -60.9, -288.3 and -215.0 kcal mol(-1), respectively. The electrostatic and induction interactions are the major source of the attraction in the complexes; the contribution of the induction interactions to the attraction is especially significant in the divalent cationglyme complexes. The binding energies of the cation-G3 complexes with Li+, Na+, K+, Mg2+, and Ca2+ and the bis(trifluoromethylsulfonyl)amide anion ([TFSA](-)) were -83.9, -86.6, -80.0, -196.1, and -189.5 kcal mol(-1), respectively, and they are larger than the binding energies of the corresponding cation-G4 complexes (-73.6, -75.0, -77.4, -172.1, and -177.2 kcal mol(-1), respectively). The binding energies and conformational flexibility of the cation-glyme complexes also affect the melting points of equimolar mixtures of glyme and TFSA salts. Furthermore, the interactions of the metal cations with the oxygen atoms of glymes significantly decrease the HOMO energy levels of glymes. The HOMO energy levels of glymes in the cation-glyme-TFSA complexes are lower than those of isolated glymes, although they are higher than those of the cation-glyme complexes.

DOI： 10.1039/c7cp02779f

Web of Science

researchmap

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

The hydrogen-bonding interactions in protic and aprotic amide solvent mixtures, i.e., formamide (FA) and N,N-dimethylformamide (DMF), were investigated via low-frequency Raman spectroscopy, small-angle neutron scattering (SANS) experiments, and molecular dynamics (MD) simulations. In a neat amide system, the low-frequency Raman spectra R(nu)s were well reproduced by the corresponding S(nu) spectra derived from the MD simulations. The observed peaks in R(nu)s at around <200 cm(-1) were assigned to the intermolecular interactions, particularly in terms of the hydrogen-bdnding network.formation and its dimensionality in the liquid state. The SANS experiments for the FA-DMF mixtures demonstrated that the FA molecules forming an extended three-dimensional hydrogen-bonding structure in the neat system interacted with DMF molecules through the hydrogen bonds in the mixtures over the whole range of solvent compositions, resulting in a homogeneous mixing state. Additionally, the R(nu) spectra for the mixtures were represented by the corresponding S(nu) spectra. From the R(nu) and S(nu) spectra of the FA-DMF mixtures, we found that (1) the Raman band at around 110 cm(-1) mainly originates from thelibration mode of amide molecules in the chain-like hydrogen-bonded structure and (2) the higher frequency band (approximately 200 cm(-1)) was attributed to the libration of the FA molecule restricted by the three-dimensional hydrogen-bonded network, which remained even in the DMF-rich compositions. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2017.05.017

Web of Science

researchmap

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

Physicochemical properties and battery performance of [Na-(glyme)][TFSA] complexes (TFSA: bis(trifluoromethanesulfonyl)amide) dissolved in a hydrofluoroether (HFE) were investigated. Glyme (tetraglyme (G4) or pentaglyme (G5)) coordinates to Na+ to form a 1:1 complex [Na(G4 or GS)](+) cation. Raman spectroscopy revealed that the complex structure of [Na(glyme)](+) is maintained in the HFE solution, and free (uncoordinated) glyrnes are not liberated on adding HFE. HFE molecules are scarcely involved in the first solvation shell of Na+ because of their low electron-pair-donating ability. Raman spectra of the [TFSA](-) anion suggests that the attractive interaction between the complex [Na(glyme)](+) cation and [TFSA](-) anion is enhanced on adding HFE. The population of contact ion-pair (CIP) and/or aggregate (AGG) is smaller for the G5 system than for the G4 one, and the [Na(G5)][TFSA]/HFE has higher ionic conductivity. The self-diffusion coefficients of the [Na(glyme)]+ complex and [TFSA](-) were measured by pulsed field gradient (PFG) NMR, and the dissociativity of [Na(glyme)] [TFSA] was assessed. The dissociativity of the G5 system is greater than that of the G4 one, and the dissociativity can be correlated with the attractive interaction between [Na(glyme)](+) and [TFSA](-), as evaluated by ab initio calculations. The dissociativity of the complexes gave significant effects on the battery performance.

DOI： 10.1021/acs.jpcc.6b06804

Web of Science

researchmap

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

Recently, we revealed N-methylimidazole C(1)Im equimolar mixtures with superacids and strong acids such as trifluoromethanesulfonic acid HTfO (Tf: CF3SO2-), bis-(trifluoromethanesulfonyl)amide acid HTf2N or trifluoroacetic acid CF3COOH are essentially protic ionic liquids by means of potentiometry of direct pH measurement in such liquids. Here, we demonstrated Raman spectroscopic speciation analysis of [C(1)hIm(+)][TfO-] and [C(1)hIm(+)][Tf2N-] (C(1)hIm(+): N-methylimidazolium) to elucidate both liquids are spectroscopically protic ionic liquids; much excess ionic species exist in these liquids and the amount of electrically neutral molecular species are practically negligible. In addition, to further insight into the hydrogen bond in the imidazolium-based protic ionic liquids, liquid structure of [C(1)hIm(+)][TfO-] were studied by high-energy X-ray total scattering HEXTS experiments with the aid of molecular dynamics simulations. Comparing with the hydrogen bond in [C(1)hIm(+)][Tf2N-] previously reported, the hydrogen bond in [C(1)hIm][TfO-] is stronger probably due to the narrower negative charge de-localization.

DOI： 10.1246/bcsj.20160130

Web of Science

researchmap

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

Equimolar mixtures of lithium bis(trifluoromethanesulfonyl)amide (LiTFSA) and tetraglyme (G4: CH3O (CH2CH2O)(4)-CH3) yield the solvate (or chelate) ionic liquid [Li(G4)][TFSA], which is a homogeneous transparent solution at room temperature. Solvate ionic liquids (SILs) are currently attracting increasing research interest, especially as new electrolytes for Li sulfur batteries. Here, we performed neutron total scattering experiments with Li-6/7 isotopic substitution to reveal the Li+ solvation/local structure in [Li(G4)][TFSA] SILs. The experimental interference function and radial distribution function around Li+ agree well with predictions from ab initio calculations and MD simulations. The model solvation/local structure was optimized with,nonlinear least-squares analysis to yield structural parameters. The refined Li+ solvation/local structure in the [Li(G4)][TFSA] SIL shows that lithium cations are not coordinated to all five oxygen atoms of the G4 molecule (deficient five-coordination) but only to four of them (actual four-coordination). The solvate cation is thus considerably distorted, which can be ascribed to the limited phase space of the ethylene oxide chain and competition for coordination sites from the TFSA anion.

DOI： 10.1021/acs.jpclett.6b01266

Web of Science

researchmap

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

An equimolar mixture of lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]) and either triglyme (G3) or tetraglyme (G4) yielded stable molten complexes: [Li(G3)][TFSA] and [Li(G4)][TFSA]. These are known as solvate ionic liquids (SILs). Glyme-based SILs have thermal and electrochemical properties favorable for use as lithium-conducting electrolytes in lithium batteries. However, their intrinsically high viscosities and low ionic conductivities prevent practical application. Therefore, we diluted SILs with molecular solvents in order to enhance their ionic conductivities. To determine the stabilities of the complex cations in diluted SILs, their conductivity and viscosity, the self-diffusion coefficients, and Raman spectra were measured. [Li(G3)](+) and [Li(G4)](+) were stable in nonpolar solvents, that is, toluene, diethyl carbonate, and a hydrofluoroether (HFE); however, ligand exchange took place between glyme and solvent when polar solvents, that is, water and propylene carbonate, were used. In acetonitrile (AN) mixed solvent complex cations [Li(G3)(AN)](+) and [Li(G4)(AN)](+) were formed. [Li(G4)][TFSA] was more conductive than [Li(G3)][TFSA] when diluted with nonpolar solvents due to the greater ionic dissociativity in [Li(G4)][TFSA] mixtures. In view of the stability of the Li-glyme complex cations, the enhanced ionic conductivities, and the intrinsic electrochemical stabilities of the diluting solvents, [Li(G4)][TFSA] diluted by toluene or HFE, can be a candidate for an alternative battery electrolyte.

DOI： 10.1021/acs.jpcc.5b11642

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

To quantify the properties of protic ionic liquids (PILs) as acid-base reaction media, potentiometric titrations were carried out in a neat PIL, ethylammonium nitrate (EAN). A linear relationship was found between the 14 pK(a) values of 12 compounds in EAN and in water. In other words, the pK(a) value in EAN was found to be roughly one unit greater than that in water regardless of the charge and hydrophobicity of the compounds. It is possible that this could be explained by the stronger acidity of HNO3 in EAN than that of H3O+ in water and not by the difference in the solvation state of the ions. The pH value in EAN ranges from -1 to 9 on the pH scale based on the pH value in water.

DOI： 10.1002/anie.201511328

Web of Science

researchmap

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

Neutron diffraction measurements have been carried out at 25 degrees C for 9.6 mol%*LiPF6-deutrerated dimethyl carbonate (DMC-d(6)) solutions in which the isotopic ratio of Li-6/Li-7 was changed. Local structure of Li+ in the solution was derived from the least squares fitting analysis of observed difference function, Delta(Li)(Q). It was revealed that Li+ is surrounded by ca. 3 DMC molecules and ca. 1 PF6- with intermolecular distances of r(Li+center dot center dot center dot O(DMC)) = 2.08 +/- 0.02 angstrom and r(Li+center dot center dot center dot F(PF6-)) = 2.03 +/- 0.06 angstrom, respectively. Raman experimental study and DFT calculations agree well with neutron structure analysis. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2015.07.004

Web of Science

researchmap

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

Liquid structure of bis-(trifluoromethanesulfonyl)amide TFSA(-) based protic and aprotic ionic liquids composed of imidazolium [h(2)Im(+)], N-methylimidazolium [C(1)hIm(+)] and N,N'-dimethylimidazolium [C(1)mIm(+)] were investigated by high-energy total scattering (NETS) experiments. The nearest neighboring cation-anon orientation variations by the N-methyl groups substitution to proton were suggested based on the peaks at around 6 and 9 angstrom in the differential radial distribution functions as the form of r(2){G(x-ray)(r)-1) for these ionic liquids. It was supposed that the NH center dot center dot center dot O hydrogen bond causes the cation-anion orientation variations. To obtain further insight into the hydrogen bond in the PIL, MD simulations performed and agreed well with the experiments. According to spatial distribution functions (SDF) for the three ionic liquids, the O atom of TFSA(-) prefers the NH hydrogen of the imidazolium that has the most positive partial atomic charge in the cation, while the F atom locates right above and right below the imidazolium ring plane. In addition, the NH center dot center dot center dot O hydrogen bond has short bond lengths and linear bond angles, while the C2H center dot center dot O interaction is long and bent. The NH center dot center dot center dot O hydrogen bond in the PIL was discussed based on structural aspect accompanied by a thermodynamic viewpoint. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2015.08.005

Web of Science

researchmap

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

Hydrofluoroethers have recently been used as the diluent to a lithium battery electrolyte solution to increase and decrease the ionic conductivity and the solution viscosity, respectively. In order to clarify the Li+ local structure in the 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) diluted [Li(G4)] [TFSA] (G4, tetraglyme; TFSA, bis(trifluoromethanesulfonyl)amide) solvate ionic liquid, Raman spectroscopic study has been done with the DFT calculations. It has turned out that the HFE never coordinates to the Li+ directly, and that the solvent (G4) shared ion pair of Li+ with TFSA anion (SSIP) and the contact ion pair between Li+ and TFSA anion (CIP) are found in the neat and HFE diluted [Li(G4)] [TFSA] solvate ionic liquid. It is also revealed that the two kinds of the CIP in which TFSA anion coordinates to the Li+ in monodentate and bidentate manners (hereafter, we call them the monodentate CIP and the bidentate CIP, respectively) exist with the SSIP of predominant [Li(G4)](+) ion-pair species in the neat [Li(G4)] [TFSA] solvate ionic liquid, and that the monodentate CIP decreases as diluting with the HFE. To obtain further insight, X-ray total scattering experiments (HEXTS) were carried out with the aid of MD simulations, where the intermolecular force field parameters, mainly partial atomic charges, have been newly proposed for the HFE and glymes. A new peak appeared at around 0.6-0.7 angstrom(-1) in X-ray structure factors, which was ascribed to the correlation between the [Li(G4)][TFSA] ion pairs. Furthermore, MD simulations were in good agreement with the experiments, from which it is suggested that the terminal oxygen atoms of the G4 in [Li(G4)](+) solvated cation frequently repeat coordinating/uncoordinating to the Li+, although almost all of the G4 coordinates to the Li+ to form [Li(G4)](+) solvated cation in the neat and HFE diluted [Li(G4)][TFSA] solvate ionic liquid.

DOI： 10.1021/acs.jpcb.5b12354

Web of Science

researchmap

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

Control of interfacial properties between the electrode and electrolyte is important for obtaining long lifecycle lithium-ion secondary batteries. To control interfacial degradation, we investigated the effect of changing the composition ratio of lithium salt (LiN(SO2CF3)(2)) and low-molecular-weight ether (CH3-O-(C2H4O)(3)-CH3) in the system. A highly electrochemically stable lithium salt glyme solvated ionic liquid electrolyte was realized, with long-lived, robust lithium solvation complexes by increasing the lithium salt composition ratio. Lithium secondary batteries using the electrolyte show notable suppression of the degradation of interfacial resistance at the interface of the electrolyte and the positive electrode (high oxidation state), which leads to a longer life-cycle of the batteries.

DOI： 10.1039/c6ra04404b

Web of Science

researchmap

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

The solvation structure of glucose in 1-ethyl-3-methylimidazolium methylphosphonate, [C(2)mIm(+)] [CH3(H)PO3-] ionic liquid and the liquid structure of the neat [C(2)mIm(+)] [CH3(H)PO3-] were investigated by high-energy X-ray diffraction (HEXRD) experiments with the aid of inolecular dynamics (MD) simulations. In neat [C(2)mIm(+)] [CH3(H)PO3-], a specific interaction between the cation and anion is found, that is, the oxygen atoms within CH3(H)PO3- are hydrogen bonded with the hydrogen of the C2 position within C2mIm+. In glucosei[C(2)mIm(+)] [CH3(H)PO3-] solutions, a significant peak is observed at 2.6 A in experimental radial distribution functions and is enhanced with increasing glucose concentration. It is found from MD simulations that the peak originated from the nearest-neighbor intermolecular interaction between glucose and the anion in [C(2)mIm(+)] [CH3(H)PO3-]. The atom atom pair correlation function derived from MD results shows that hydroxyl groups of glucose interact with oxygen atoms within CH3(H)PO3- through the hydrogen bonds. The intermolecular hydrogen bonds coexist with the intramolecular hydrogen bond in a glucose molecule. We conclude that glucose is easy to form a hydrogen bond with a polar CH3(H)PO3- anion; however, rupture of intrarnolecular hydrogen bonds within glucose is not enough in the ionic liquid.

DOI： 10.1021/acs.jpcb.5b00724

Web of Science

researchmap

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

Speciation analysis is defined as identifying and/or measuring the quantities of one or more individual chemical species in a sample; it also involves evaluations of the species distribution and molecular structure of the species, and even their conformers. Raman/IR vibration spectroscopy and neutron/X-ray scattering experiments can reveal not only molecular and/or liquid structures, but also species formation equilibria thermodynamically. We propose that such techniques can be called "Spectrothermodynamics". In this contribution, we show this speciation analysis applied to lithium ion solvation in the bis-(trifluoromethanesulfonyl)amide and the bis-(fluromethanesulfonyl)amide based ionic liquids, based on the spectrothermodynamics. We also describe ionic liquids specific central metal ion stabilization by the ionic liquid consisting of cations at the metal ion second sphere and the solvation structure equilibria evaluated thermodynamically.

DOI： 10.2116/bunsekikagaku.64.197

Web of Science

researchmap

Language：English   Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

In electrolyte solution system, metal ions are generally solvated by solvent molecules to form metal ion solvation complexes. Electrochemical and physicochemical properties of electrolyte solutions such as ionic conductivity, redox reaction behavior, viscosity, density, and so on strongly depend on the static and dynamic structures of the metal ion solvation complexes. Using ionic liquids (ILs) as a solvent, the anions solvate to metal ions to form [Mn+(anion-)m](n-m) complexes in ILs. In this chapter, we describe our structural studies for the Li ion solvation in IL system. We focus on aprotic imidazolium-based ILs with bis(fluorosulfonyl)imide, [FSI], and bis(trifluorosulfonyl)amide, [N(Tf)2], anions, and their Li ion solutions are investigated by Raman spectroscopic and high-energy X-ray diffraction experiments and theoretical calculations.

DOI： 10.1007/978-3-319-13485-7_10

Scopus

researchmap

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

Cation and anion effects were investigated in the energetics of CO2 solvation in room-temperature ionic liquids. The solvation free energy in 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) was calculated with three types of force fields by molecular dynamics simulations combined with the energy-representation (ER) method, and the interaction responsible for the CO2 stability was examined in terms of the average sum of the solute-solvent interaction energy and its electrostatic and van der Waals components. A key role of the van der Waals component was found for the cation contribution, and the electrostatic component was seen to be minor in the anion contribution. The solvation free energy of CO2 was also investigated in ionic liquids of the form 1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cnmim][NTf2]) with varying alkyl-chain lengths of n = 4, 6, 8, and 12 by the ER method. The free energy was found to depend weakly on n, in agreement with experiments, and the cation and anion contributions and the electrostatic and van der Waals interaction components acted similarly at all values of n examined. The alkyl-chain length was found not to affect the local structure around CO2 strongly, and its effect on the interaction energy with CO2 appeared mainly through the bulk density.

DOI： 10.1021/jp5101957

Web of Science

researchmap

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

Molecular dynamics simulations of equimolar mixtures of glymes (triglyme and tetraglyme) and Li[TFSA] (lithium bis(trifluoromethylsulfonyl) amide) show that the glyme chain length affects the coordination geometries of Li+, which induces the changes in interactions between the [Li(glyme)](+) complex and [TFSA](-) anions and diffusion of ions in the equimolar mixtures.

DOI： 10.1039/c4cp04718d

Web of Science

researchmap

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

Certain molten complexes of Li salts and solvents can be regarded as ionic liquids. In this study, the local structure of Li+ ions in equimolar mixtures ([Li(glyme)] X) of glymes (G3: triglyme and G4: tetraglyme) and Li salts (LiX: lithium bis(trifluoromethanesulfonyl) amide (Li[TFSA]), lithium bis(pentafluoroethanesulfonyl) amide (Li[BETI]), lithium trifluoromethanesulfonate (Li[OTf]), LiBF4, LiClO4, LiNO3, and lithium trifluoroacetate (Li[TFA])) was investigated to discriminate between solvate ionic liquids and concentrated solutions. Raman spectra and ab initio molecular orbital calculations have shown that the glyme molecules adopt a crown-ether like conformation to form a monomeric [Li(glyme)](+) in the molten state. Further, Raman spectroscopic analysis allowed us to estimate the fraction of the free glyme in [Li(glyme)] X. The amount of free glyme was estimated to be a few percent in [Li(glyme)] X with perfluorosulfonylamide type anions, and thereby could be regarded as solvate ionic liquids. Other equimolar mixtures of [Li(glyme)] X were found to contain a considerable amount of free glyme, and they were categorized as traditional concentrated solutions. The activity of Li+ in the glyme-Li salt mixtures was also evaluated by measuring the electrode potential of Li/Li+ as a function of concentration, by using concentration cells against a reference electrode. At a higher concentration of Li salt, the amount of free glyme diminishes and affects the electrode reaction, leading to a drastic increase in the electrode potential. Unlike conventional electrolytes (dilute and concentrated solutions), the significantly high electrode potential found in the solvate ILs indicates that the solvation of Li+ by the glyme forms stable and discrete solvate ions ([Li(glyme)](+)) in the molten state. This anomalous Li+ solvation may have a great impact on the electrode reactions in Li batteries.

DOI： 10.1039/c4cp05943c

Web of Science

researchmap

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

Liquid structures of Li/Mg/Cs-TFSA (TFSA: bis(trifluoromethylsulfonyl) amide, N(SO2CF3)(2)(-)) molten-salt systems have been investigated by Raman spectroscopy and high-energy X-ray diffraction. The Raman spectroscopic measurements indicate that the cis-conformer of the TFSA anion is more favorable than the trans-conformer in the molten salts containing Li+ and/or Mg2+, whereas the latter is dominant for a pure Cs[TFSA] molten salt. The present reverse Monte Carlo (RMC) structural modelling suggests that the coordination number of the anion around Mg, NMg-anion, decreased in Li0.1Mg0.1Cs0.8[TFSA](1.1) molten salt compared to that in Mg0.1Cs0.9[TFSA](1.1). The Mg-anion distance under the coexistence of Li+ is found to be about 10-15% longer than that without Li+ at around NMg-anion similar to 1.5, which means the increase of free volume around Mg cations in the Li-contained molten salt. Thus, the electrodeposition of Mg in alkali-TFSA molten salts would be facilitated under the coexistence of Li cations.

DOI： 10.1039/c4ra13244k

Web of Science

researchmap

DOI： 10.1039/c5cp01760b

Web of Science

researchmap

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

The structure and interactions of different (Li salt + glyme) mixtures, namely equimolar mixtures of lithium bis(trifluoromethylsulfonyl) imide, nitrate or trifluoroacetate salts combined with either triglyme or tetraglyme molecules, are probed using Molecular Dynamics simulations. structure factor functions, calculated from the MD trajectories, confirmed the presence of different amounts of lithium-glyme solvates in the aforementioned systems. The MD results are corroborated by S(q) functions derived from diffraction and scattering data (HEXRD and SAXS/WAXS). The competition between the glyme molecules and the salt anions for the coordination to the lithium cations is quantified by comprehensive aggregate analyses. Lithium-glyme solvates are dominant in the lithium bis(trifluoromethylsulfonyl) imide systems and much less so in systems based on the other two salts. The aggregation studies also emphasize the existence of complex coordination patterns between the different species (cations, anions, glyme molecules) present in the studied fluid media. The analysis of such complex behavior is extended to the conformational landscape of the anions and glyme molecules and to the dynamics (solvate diffusion) of the bis(trifluoromethylsulfonyl) imide plus triglyme system.

DOI： 10.1039/c5cp03414k

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER/PLENUM PUBLISHERS  

Ion-ion interactions or liquid structures in low-viscosity ionic liquid, 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide, [C(2)mIm(+)][FSA(-)] were investigated by high-energy X-ray diffraction (HEXRD) experiments and molecular dynamics (MD) simulations. Experimental X-ray structure factor, S (exp)(q) obtained from the HEXRD was successfully deconvoluted into the intra- and the intermolecular components, S (intra) (exp) (q) and S (inter) (exp) (q), respectively, by taking into account the population of cis and trans conformers of the FSA anion to give the corresponding radial distribution functions, G (intra) (exp) (r) and G (inter) (exp) (r), respectively. The G (inter) (exp) (r) exhibits the peaks at 3.5, 4.6 and 5.4 , which is well represented by theoretical radial distribution function, G (inter) (MD) (r) obtained from MD simulations. From the space distribution function, SDF calculated by MD simulations, it was found that static structure (distance and orientation) of the nearest neighbor intermolecular interaction between cation and anion in [C(2)mIm(+)][FSA(-)] is similar to its analogous ionic liquid, [C(2)mIm(+)][TFSA(-)] where TFSA is bis(trifluoromethanesulfonyl)amide.

DOI： 10.1007/s10953-014-0234-8

Web of Science

researchmap

Language：English   Publisher：SPRINGER/PLENUM PUBLISHERS  

DOI： 10.1007/s10953-014-0248-2

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER/PLENUM PUBLISHERS  

High-energy X-ray diffraction measurements were carried out at 26 A degrees C for aqueous 1.0, 2.0 and 2.05 mol% disodium adenosine 5'-triphosphate (ATP) and 2.0 and 2.05 mol% disodium adenosine 5'-diphosphate (ADP) solutions in order to obtain direct experimental information on the intramolecular conformations of ATP and ADP molecules in aqueous solutions. Observed interference terms were analyzed in terms of the intramolecular geometry of the ATP and ADP molecules. Dihedral angles between adenine and the ribose group (t (1)), ribose-ring and methylene group of ribose (t (2)), and the methylene group of ribose and triphosphate (or diphosphate) group (t (3)), were determined through the least-squares fitting procedure of the observed interference term.

DOI： 10.1007/s10953-014-0153-8

Web of Science

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Web of Science

researchmap

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

To develop a basic understanding of a new class of ionic liquids (ILs), "solvate" ILs, the transport properties of binary mixtures of lithium bis(trifluoromethanesulfonypamide (Li[TFSA]) and oligoethers (tetraglyme (G4), triglyme (G3), diglyme (G2), and monoglyme (G1)) or tetrahydrofiiran (THF) were studied. The self-diffusion coefficient ratio of the solvents and Li+ ions (D-sol/D-Li,) was a good metric for evaluating the stability of the complex cations consisting of Li+ and the solvent(s). When the molar ratio of Li+ ions and solvent oxygen atoms ([O]/[Li+]) was adjusted to 4 or 5, D-sol/D-Li, always exceeded unity for THF and G1-based mixtures even at the high concentrations, indicating the presence of uncoordinating or highly exchangeable solvents. In contrast, long-lived complex cations were evidenced by a D-sol/Du(Li) similar to 1 for the longer G3 and G4. The binary mixtures studied were categorized into two different classes of liquids: concentrated solutions and solvate ILs, based on D-sol/Du(Li). Mixtures with G2 exhibited intermediate behavior and are likely the borderline dividing the two categories. The effect of chelation on the formation of solvate ILs also strongly correlated with electrolyte properties; the solvate ILs showed improved thermal and electrochemical stability. The ionicity (Lambda(imp)/Lambda(NMR)) of [Li(glyme or THF)(x)][TFSA] exhibited a maximum at an [O]/[Li+] ratio of 4 or 5.

DOI： 10.1021/jp501319e

Web of Science

researchmap

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

We have measured physicochemical properties of five alkyltrimethylammonium cation-based room-temperature ionic liquids and compared them with those obtained from computational methods. We have found that static properties (density and refractive index) and transport properties (ionic conductivity, self-diffusion coefficient, and viscosity) of these ionic liquids show close relations with the length of the alkyl chain. In particular, static properties obtained by experimental methods exhibit a trend complementary to that by computational methods (refractive index proportional to [polarizability/molar volume]). Moreover, the self-diffusion coefficient obtained by molecular dynamics (MD) simulation was consistent with the data obtained by the pulsed-gradient spin-echo nuclear magnetic resonance technique, which suggests that computational methods can be supplemental tools to predict physicochemical properties of room-temperature ionic liquids.

DOI： 10.1021/jp500123q

Web of Science

researchmap

Language：English   Publisher：WALTER DE GRUYTER GMBH  

DOI： 10.1515/pac-2014-5028

Web of Science

researchmap

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

The quantitative Bronsted basicity of butylamine (BuNH2) in the typical aprotic ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, [C(2)mIm(+)][TFSA(-)], is reported. Potentiometric titration was performed for BuNH2 in the aprotic IL to experimentally determine the acid dissociation constant (pK(a)) for butylammonium (BuNH3+). The pK(a) value was estimated to be 16.6(1), and it was found that the value is significantly larger than that in aqueous solution (pK(a) = 10.6).

DOI： 10.1246/cl.130537

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Raman spectra of 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide [C2mIm+][FSA-] ionic liquid solutions dissolving LiFSA salt of various concentrations were measured at 298 K. FSA - ((FSO2)2N-) is an analogue anion of bis(trifluoromethanesulfonyl)amide ((CF3SO2) 2N-
TFSA-). We found that a solvation number of the Li+ ion in [C2mIm+][FSA-] is 3, though it has been well established that Li+ ion is solvated by two TFSA- anions in the corresponding ionic liquids below the Li + ion mole fraction of xLi+ &lt
0.2. To yield further insight into larger solvation numbers, Raman spectra were measured at higher temperatures up to 364 K. The Li+ ion solvation number in [C2mIm+][FSA-] evidently decreased when the temperature was elevated. Temperature dependence of the Li+ ion solvation number was analyzed assuming an equilibrium between [Li(FSA) 2]- and [Li(FSA)3]2-, and the enthalpy ΔH and the temperature multiplied entropy TΔS for one FSA- liberation toward a bulk ionic liquid were successfully evaluated to be 35(2) kJ mol-1 and 29(2) kJ mol-1, respectively. The ΔH and ΔS suggest that the Li+ ion is coordinated by one of bidentate and two of monodentate FSA- at 298 K, and that the more weakly solvated monodentate FSA- is liberated at higher temperatures. The high-energy X-ray diffraction (HEXRD) experiments of these systems were carried out and were analyzed with the aid of molecular dynamics (MD) simulations. In radial distribution functions evaluated with HEXRD, a peak at about 1.94 Å appeared and was attributable to the Li +-O(FSA-) correlations. The longer Li+- O(FSA-) distance than that for the Li+-O(TFSA-) of 1.86 Å strongly supports the larger solvation number of the Li + ions in the FSA- based ionic liquids. MD simulations at least qualitatively reproduced the Raman and HEXRD experiments. © 2013 American Chemical Society.

DOI： 10.1021/jp4053264

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/chem.201302228

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

The stabilization energies (ΔEform) calculated for the formation of the Li+ complexes with mono-, di- tri- and tetra-glyme (G1, G2, G3 and G4) at the MP2/6-311G* level were -61.0, -79.5, -95.6 and -107.7 kcal mol-1, respectively. The electrostatic and induction interactions are the major sources of the attraction in the complexes. Although the ΔEform increases by the increase of the number of the O⋯Li contact, the ΔEform per oxygen atom decreases. The negative charge on the oxygen atom that has contact with the Li+ weakens the attractive electrostatic and induction interactions of other oxygen atoms with the Li+. The binding energies calculated for the [Li(glyme)]+ complexes with TFSA- anion (glyme=G1, G2, G3, and G4) were -106.5, -93.7, -82.8, and -70.0 kcal mol-1, respectively. The binding energies for the complexes are significantly smaller than that for the Li+ with the TFSA- anion. The binding energy decreases by the increase of the glyme chain length. The weak attraction between the [Li(glyme)]+ complex (glyme=G3 and G4) and TFSA - anion is one of the causes of the fast diffusion of the [Li(glyme)]+ complex in the mixture of the glyme and the Li salt in spite of the large size of the [Li(glyme)]+ complex. The HOMO energy level of glyme in the [Li(glyme)]+ complex is significantly lower than that of isolated glyme, which shows that the interaction of the Li + with the oxygen atoms of glyme increases the oxidative stability of the glyme. The interactions in Li+-glymes-TFSA- complexes: The interactions of Li+ with glymes (tri- and tetra-glyme) are strong (-96 and -108 kcal mol-1), while the interactions of the [Li(glyme)]+ complexes with TFSA- (-82 and -70 kcal mol-1) are weaker than that between Li+ and TFSA - (-137 kcal mol-1). Copyright © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/cphc.201200843

Web of Science

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

High-resolution inelastic X-ray scattering (IXS) measurements were performed for room-temperature ionic liquids (ILs) of 1-ethyl-3- methylimidazolium bis(trifluoromethanesulfonyl)amide and bis(fluorosulfonyl) amide, [C2mIm+][TFSA-] and [C 2mIm+][FSA-], respectively, at ambient temperature. The observed spectra as a function of Q of 1.4-6 nm-1 can be ascribed to quasi-elastic and inelastic scatterings, so that they are well represented with the fitting by using the Lorentz and the damped harmonic oscillator model functions to yield the dynamic structure factors. It was found in the intermediate scattering function, F(Q, t) that both ILs show the relaxation at t &lt
10 ps. The IXS measurements were also made on [C 2mIm+][TFSA-] and [C2mIm +][FSA-] solutions dissolving Li salt. It is suggested that the adding of Li salt to IL significantly prolongs the relaxation time. © 2013 AIP Publishing LLC.

DOI： 10.1063/1.4802768

Web of Science

Scopus

researchmap

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

Solvation structures of poly(ethylene glycol) (PEG) in 1-ethyl-3-methylimidazolium-based ionic liquids solution were studied by using high-energy X-ray diffraction (HEXRD) and molecular dynamics (MD) simulation in terms of dependences on the anion-type for ILs, molecular weight (M-w), concentration and shape (linear or tetra-armed) for PEG. It was found from HEXRD experiment that there is no M-w and shape dependences for PEG in 1-ethyl-3-methylimidazolium bis-(trifluoromethansulfonyl)amide, [C(2)mIm(+)][TFSA(-)] solution, implying that the local structure (r < 15 angstrom) is not influenced by M-w and shape of PEG. From the HEXRD results with the aid of MD simulations, it was found that C(2)mIm cation preferentially solvates to PEG in all the ILs, and TFSA is distributed randomly with van der Waals and weak electrostatic interactions. The atom-atom pair correlation and space distribution functions evaluated from the MD simulations revealed that hydrogen bonding interactions are formed between C2 carbon within the imidazolium ring and O (PEG), which is essentially different from C4 carbon-O and C5 carbon-O interactions. Finally, we discussed the relationship between the obtained microscopic solvation structures and the macroscopic properties of PEG-based gel (swelling ratio and chi parameters).

DOI： 10.1021/ma400218e

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

It has been established that poly(benzyl methacrylate) in a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C2mIm+][TFSA-]), exhibits lower critical solution temperature (LCST)-type phase separation. In this work we investigated the solvation structure of benzyl methacrylate monomer in the ionic liquid by using high-energy X-ray diffraction with the aid of a molecular dynamics simulation. It was found that the C2mIm cation orderly distributes above and below a benzyl group within benzil methacrylate (BnMA), while the TFSA anion distributes around the equatorial position of the benzyl group where no cation distribution is found, with a weak interaction between TFSA and BnMA. The relationship between specific solvation and the LCST phase separation mechanism was considered at the molecular level. © The Japan Society for Analytical Chemistry.

DOI： 10.2116/analsci.29.311

Web of Science

Scopus

researchmap

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

Proton-donating and ionization properties of several protic ionic liquids (PILs) made from N-methylimidazole (Mim) and a series of acids (HA) have been assessed by means of potentiometric and calorimetric titrations. With regard to strong acids, bis(trifluoromethanesulfonyl) amide (Tf2NH) and trifluoromethanesulfonic acid (TfOH), it was elucidated that the two equimolar mixtures with Mim almost consist of ionic species, HMim(+) and A(-), and the proton transfer equilibrium corresponding to autoprotolysis in ordinary molecular liquids was established. The respective autoprotolysis constants were successfully evaluated, which indicate the proton-donating abilities of TfOH and Tf2NH in the respective PILs are similar. In the case of trifluoroacetic acid, the proton-donating ability of CF3COOH is much weaker than those of TfOH and Tf2NH, while ions are predominant species. On the other hand, with regard to formic acid and acetic acid, protons of these acids are suggested not to transfer to Mim sufficiently. From calorimetric titrations, about half of Mim is estimated to be proton-attached at most in the CH3COOH-Mim equimolar mixture. In such a mixture, hydrogen-bonding adducts formation has been suggested. The autoprotolysis constants of the present PILs show a good linear correlation with dissociation constants of the constituent acids in an aqueous phase.

DOI： 10.1021/jp308477p

Web of Science

researchmap

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

The shear relaxation spectra of three imidazolium-based ionic liquids, 1-methyl-3-octylimidazolium chloride ([C(8)mim][Cl]), 1-methyl-3-octylimidazolium hexafluorophosphate ([C(8)mim][PF6]), and 1-dodecyl-3-methylimidazolium bis(trifluoromethanesulfonyl) amide ([C(12)mim][TFSA]) were measured and compared with the intermediate scattering functions determined with neutron spin echo (NSE) spectroscopy. The shear relaxation is slower than that predicted from the relaxation of the main peak of the structure factor that is common to other molecular liquids, whereas it is faster than that from the relaxation of the pre-peak, that corresponds to the correlation length of about 10 nm specific to ionic liquids with an intermediately long alkyl chain. The role of the pre-peak structure in the mechanism of shear viscosity of ionic liquids is discussed based on the comparison between NSE and shear relaxations. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751547]

DOI： 10.1063/1.4751547

Web of Science

researchmap

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

X-ray photoelectron spectroscopy (XPS) was applied to a neat ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [EMI+] [Tf2N-] and its lithium salt solution at room temperature to clarify the composition and structure of its near-surface region. Core level peaks were recorded for Li 1s, N 1s, C 1s, F 1s, O 1s, S 2s, and S 2p. Valence band XPS spectra (0-40 eV binding energy) were also studied. The XPS spectra were analyzed using DV-X alpha calculations. Results show that the planar type isomer of the EMI+ cation is dominant at the near-surface region of EMI-Tf2N. Results of XPS measurements show a spectrum of Li Is in Li/EMI-Tf2N. The proposed models for the preferred orientation of the ions exhibit good agreement with. results obtained from the DV-X alpha calculations.

DOI： 10.1021/jp301658k

Web of Science

researchmap

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

Two ionic liquids (ILs) based on the BF4- anion are studied by H-1, B-11, and F-19 NMR spectroscopy by measuring self-diffusion coefficients (D) and spin-lattice relaxation times (T-1). The cations are 1-ethyl-3-methylimidazolium (EMIm) and 1-butyl-3-methylimidazolium (BMIm). Since two NMR nuclei (B-11 and F-19) of BF4- exhibit narrow lines and high sensitivity, the B-11 and F-19 NMR measurements of D-BF4 and T-1(BF4) were performed in a wide temperature range. The temperature-dependent behaviors of T-1(F-19) and T-1(B-11) were remarkably different, although the values of D-BF4(F-19) and D-BF4(B-11) almost agreed. Since the Arrhenius plots of T-1's for H-1, F-19, and B-11 exhibited T-1 minima, the correlation times tau(c)(H-1), tau(c)(F-19), and tau(c)(B-11) were evaluated. The D(cation) and D(BF4) were plotted against 1/tau(c)(H-1) and 1/tau(c)(F-19), respectively, and the relationships between translational and rotational motion are discussed. The translational diffusion of the cations is related to molecular librational motion and that of BF4 is coupled with reorientational motion. The tau(c)(B-11) derived from B-11 T-1 can be attributed to a local jump. From the plots of the classical Stokes-Einstein (SE) equation, the empirical c values, which were originally derived by theoretical boundary conditions, were estimated for each ion. The empirical c(BF4) was about 4.4(5), while the c values of the cations were smaller than 4.

DOI： 10.1021/jp306146s

Web of Science

researchmap

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

Refractive index, an optical property, and liquid density were measured for 17 types of room-temperature ionic liquids at various temperatures. Ab initio calculations were performed to yield theoretical polarizability of the respective ionic liquid composing ions. A highly linear correlation was found between the experimental refractive index and the predicted polarizability normalized in terms of the molar volume. This suggests that the electronic polarization of the ionic liquid composing ions predominantly contributes to the refractive index of the room-temperature ionic liquids.

DOI： 10.1021/je201289w

Web of Science

researchmap

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

Free energy of contact ion-pair (CIP) formation of lithium ion with BF4- and PF6- in water, propylene carbonate (PC), dimethyl carbonate (DMC) are quantitatively analyzed using MD simulations combined with the energy representation method. The relative stabilities of the mono-, bi-, and tridentate coordination structures are assessed with and without solvent, and water, PC, and DMC are found to favor the CIP-solvent contact. The monodentate structure is typically most stable in these solvents, whereas the configuration is multidentate in vacuum. The free energy of CIP formation is not simply governed by the solvent dielectric constant, and microscopic analyses of solute-solvent interaction at a molecular level are then performed from energetic and structural viewpoints. Vacant sites of Li+ cation in CIP are solvated with three carbonyl oxygen atoms of PC and DMC solvent molecules, and the solvation is stronger for the monodentate CIP than for the multidentate. Energetically favorable solute-solvent configurations are shown to be spatially more restricted for the multidentate CIP, leading to the observation that the solvent favors the monodentate coordination structure.

DOI： 10.1021/jp3011487

Web of Science

researchmap

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

The shear relaxation spectra of the solutions of lithium salts in ionic liquids composed of N-methyl-N-propylpyrrolidinium cation paired with bis(trifluoromethanesulfonyl)amide (TFSA(-)) or bis(fluorosulfonyl)amide (FSA(-)) anions are determined from 5 to 205 MHz at various concentrations of lithium salts. The addition of lithium salt retards the shear relaxation, together with the increase in the shear viscosity. The normalized spectra reduce to a single curve when plotted against the product of the frequency and zero-frequency shear viscosity, which indicates that the increase in the shear viscosity by lithium salts is ascribed to the increase in the relaxation time. The difference in the shear viscosity of TFSA- and FSA-based ionic liquids is also elucidated in terms of the shear relaxation time. The relationship with previous studies on ionic mobility and liquid structure is also discussed.

DOI： 10.1021/jp3032308

Web of Science

researchmap

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

Physicochemical properties such as a thermal behavior, ionic conductivity, viscosity and density, and acid-base properties of a new class of 2-hydroxyethylammonium-based protic ionic liquids (PILs) have been investigated. Thirty-six potential PILs were surveyed to find 32 salts with a melting point below 373 K. Among them, [(EtOH)(n)Et(3-n)NH+][TFS-] (Et, C2H5; n = 0 - 3) and [(EtOH)(2)EtNH+][X-] (X = TFS, trifluoromethanesulfonate; TFSA, bis(trifluoromethanesulfonyl)amide; NO3) were studied in terms of the Walden plots, molar volume and auto-protolysis reaction for effect of the number of 2-hydroxyethyl groups introduced in the cations and for dependence of the anion nature, respectively. With regard to [(EtOH)(n)Et(3-n)NH+][TFS-] (n = 0 - 3), the ion-ion interactions between cation-anion and cation-cation were enhanced with increasing the number of the 2-hydroxyethyl groups. In addition, the auto-protolysis constant K-s value for [(EtOH)(2)EtNH+][TFSA(-)] is smaller than that for TFS- based PIL, indicating that HTFSA behaves as a stronger acid than HTFS in the respective PIL. On the other hand, in [(EtOH)(2)EtNH+][NO3-], the emf jump was rather small, which suggests that the proton of HNO3 does not easily transfer to (EtOH)(2)EtN in the liquid state.

DOI： 10.2116/analsci.28.469

Web of Science

researchmap

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

Liquid structure and the closest ion-ion interactions in a series of primary alkylammonium nitrate ionic liquids [CnAm+][NO3-] (n = 2, 3, and 4) were studied by means of high-energy X-ray diffraction (HEXRD) experiments with the aid of molecular dynamics (MD) simulations. Experimental density and X-ray structure factors are in good accordance with those evaluated with MD simulations. With regard to liquid structure, characteristic peaks appeared in the low Q(Q: a scattering vector) region of X-ray structure factors S(Q)'s for all ionic liquids studied here, and they increased in intensity with a peak position shift toward the lower Q side by increasing the alkyl chain length. Experimentally evaluated S-Qpeak(r(max)) functions, which represent the S(Q) intensity at a peak position of maximum intensity Q(peak) as a function of distance (actually a integration range r(max)), revealed that characteristic peaks in the low Q region are related to the intermolecular anion-anion correlation decrease in the r range of 10-12 angstrom. Appearance of the peak in the low Q region is probably related to the exclusion of the correlations among ions of the same sign in this r range by the alkyl chain aggregation. From MD simulations, we found unique and rather distorted NH center dot center dot center dot O hydrogen bonding between CnAm+ (n = 2, 3, and 4) and NO3- in these ionic liquids regardless of the alkyl chain length. Subsequent ab initio calculations for both a molecular complex C2H5NH2 center dot center dot center dot HONO2 and an ion pair C2H5NH3+center dot center dot center dot NO2- revealed that such distorted hydrogen bonding is specific in a liquid state of this family of ionic liquids, though the linear orientation is preferred for both the N center dot center dot center dot HO hydrogen bonding in a molecular complex and the NH center dot center dot center dot O one in an ion pair. Finally, we propose our interpretation of structural heterogeneity in PILs and also in APILs.

DOI： 10.1021/jp209561t

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

The physicochemical (e. g., density, viscosity, ionic conductivity, and self-diffusion coefficient) and electrochemical (e. g., electrochemical window and electric double-layer capacitor performance) properties of two new types of room-temperature ionic liquids, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (EMIm-FAP) and 1-ethyl-3-methylimidazolium tetracyanoborate (EMIm-TCB), were investigated and compared. EMIm-FAP showed a wider electrochemical window with a carbon working electrode compared with EMIm-TCB, in spite of lower viscosity, larger self-diffusion coefficients and higher ionic conductivity. Also, the electric double-layer capacitor using EMIm-FAP shows better cycle reversibility and higher charge/discharge voltage operation (over 3 V) than that using EMIm-TCB. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.032207jes] All rights reserved.

DOI： 10.1149/2.032207jes

Web of Science

researchmap

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 &gt; 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

Web of Science

researchmap

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

Liquid structures of the bis(trifluoromethanesulfonyl)amide based ionic liquids composed of 1-ethyl-3-methylimidazolium and N-methyl-N-propylpyrrolidinium [(C(2)mIm(+)][TFSA(-)] and [C(3)mPyrro(+)][TFSA(-)], respectively) and Li+ ion solvation structure in their lithium salt solutions were studied by means of high-energy X-ray diffraction (HEXRD) technique with the aid of MD simulations. With regard to neat ionic liquids, a small but significant difference was found at around 3.5 angstrom in the intermolecular radial distribution functions G(inter)(r)s for these two ionic liquids; i.e., G(inter)(r) for [C(2)mIm(+)][TFSA(-)] was positioned at a slightly shorter region relative to that for [C(3)mPyrro(+)] [TFSA(-)], which suggests that the nearest neighboring cation anion interaction in the imidazolium ionic liquid is slightly greater than that in the other. With regard to Li+ ion solvation structure, G(inter)(r)s for [C(2)mIm(+)][TFSA(-)] dissolving Li+ ion exhibited additional small peak of about 1.9 angstrom attributable to the Li+-O (TFSA(-)) atom atom correlation, though the corresponding peak was unclear in [C(3)mPyrro(+)][TFSA(-)] due to overlapping with the intramolecular atom atom correlations in [C(3)mPyrro(+)]. In addition, the long-range density fluctuation observed in the neat ionic liquids diminished with the increase of Li+ ion concentration for both ionic liquid solutions. These observations indicate that the large scale Li+ ion solvated dusters are formed in the TFSA based ionic liquids, and well support the formation of [Li(TFSA)(2)](+) cluster clarified by previous Raman spectroscopic studies. MD simulations qualitatively agree with the experimental facts, by which the decrease in the long-range oscillation amplitude of r(2){G(r) - 1} for the Li+ containing ionic liquids can be ascribed to the variation in the long-range anion anion correlations caused by the formation of the Li+ ion solvated dusters.

DOI： 10.1021/jp2072827

Web of Science

researchmap

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

Room temperature ionic liquids (ILs) are stable liquids composed of anions and cations. 1-ethyl-3-methyl-imidazolium (EMIm, EMI) is a popular and important cation that produces thermally stable ILs with various anions. In this study two amide-type anions, bis(trifluoromethanesulfonyl) amide [N(SO2CF3)(2), TFSA, TFSI, NTf2, or Tf2N] and bis(fluorosulfonyl) amide [(N(SO2F)(2), FSA, or FSI] were investigated by multinuclear NMR spectroscopy. In addition to EMIm-TFSA and EMIm-FSA, lithium-salt-doped binary systems were prepared (EMIm-TFSA-Li and EMIm-FSA-Li). The spin-lattice relaxation times (T-1) were measured by H-1, F-19, and Li-7 NMR spectroscopy and the correlation times of H-1 NMR, tau(c)(EMIm) (8 x 10(-10) to 3 x 10(-11) s) for the librational molecular motion of EMIm and those of Li-7 NMR, tau(c)(Li) (5 x 10(-9) to 2 x 10(-10) s) for a lithium jump were evaluated in the temperature range between 253 and 353 K. We found that the bulk viscosity (eta) versus tau(c)(EMIm) and cation diffusion coefficient D-EMIm versus the rate 1/tau(c)(EMIm) have good relationships. Similarly, linear relations were obtained for the eta versus tau(c)(Li) and the lithium diffusion coefficient D-Li versus the rate 1/tau(c)(Li). The mean one-jump distances of Li were calculated from tau(c)(Li) and D-Li. The experimental values for the diffusion coefficients, ionic conductivity, viscosity, and density in our previous paper were analyzed by the Stokes-Einstein, Nernst-Einstein, and Stokes-Einstein-Debye equations for the neat and binary ILs to clarify the physicochemical properties and mobility of individual ions. The deviations from the classical equations are discussed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3625923]

DOI： 10.1063/1.3625923

Web of Science

researchmap

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELECTROCHEMICAL SOC INC  

Physicochemical properties such as density, viscosity, ionic conductivity, and self-diffusion coefficient of two types of room-temperature ionic liquids composed of cations with N-P bonds were investigated. One is an ionic liquid composed of cations with N-P-O bond, namely, tri(N,N-dimethylamino)-n-butoxyphosphonium bis(trifluoromethanesulfonyl)amide (TABP-TFSA) and has a relatively low viscosity (38 mPa s at 30 degrees C) due to the high internal mobility of the cation, despite its large ion size. TABP-TFSA showed a characteristic electrochemical oxidation behavior, such as a wide electrochemical potential window of stability without gas evolution. Formation of passivation film on a Pt electrode was suggested from the results of potential sweep experiments. The lithium secondary battery ([LiCoO2|Li] cell) using TABP-TFSA as the electrolyte achieved stable charge-discharge operations in over 500 cycles. For another ionic liquid with N-P bond, namely, TAEP-TFSA (TAEP(+) = tri(N-methyl-N-(n-butylamino))ethylphosphonium), less battery cycle stability and low rate performances were observed, despite the higher ionic dissociation than TABP-TFSA, probably because of the high viscosity and low electrochemical oxidative stability. It is shown that the introduction of oxygen in the cation like N-P-O produces better performances compared with the cation having N-P structure. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3613959] All rights reserved.

DOI： 10.1149/1.3613959

Web of Science

researchmap

Language：English   Publishing type：Part of collection (book)   Publisher：Nova Science Publishers, Inc.  

Conformational isomerism of room-temperature ionic liquids composing ions plays a key role on static and dynamic properties such as melting and freezing, density, ion conductivity, viscosity and so on. Additionally, in solution, metal ions are generally solvated by solvent molecules to form metal ion solvated clusters. Reactivity and mobility of metal ions in solution thus depend on the structure of metal ion solvated clusters. This can be also applied to those in ionic liquids. Vibration spectroscopy of Raman scattering and IR absorption is one of the useful tools to investigate the conformational isomerism and the structure of metal ion solvated clusters in ionic liquids. Moreover, they become more powerful with the aid of theoretical quantum calculations such as ab initio and DFT calculations, and molecular dynamics simulations. Here, we describe our recent works on the conformational isomerism and the metal ion solvation in ionic liquids by means of Raman/IR spectroscopy and theoretical calculations. © 2011 Nova Science Publishers, Inc. All rights reserved.

Scopus

researchmap

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

Room-temperature ionic liquids (RTIL, IL) are stable liquids composed of anions and cations. N-methyl-N-propyl-pyrrolidinium (P-13, Py-13, PYR13, or mppy) is an important cation and produces stable ILs with various anions. In this study two amide-type anions, bis(trifluoromethanesulfonyl)amide [N(SO2CF3)(2), TFSA, TFSI, NTf2, or Tf2N] and bis(fluorosulfonyl)amide [N(SO2F)(2), FSA, or FSI], were investigated. In addition to P-13-TFSA and P-13-FSA, lithium salt doped samples were prepared (P-13-TFSA-Li and P-13-FSA-Li). The individual ion diffusion coefficients (D) and spin-lattice relaxation times (T-1) were measured by H-1, F-19, and Li-7 NMR. At the same time, the ionic conductivity (sigma), viscosity (eta), and density (rho) were measured over a wide temperature range. The van der Waals volumes of P-13, TFSA, FSA, Li(TFSA)(2), and Li(FSA)(3) were estimated by molecular orbital calculations. The experimental values obtained in this study were analyzed by the classical Stokes-Einstein, Nernst-Einstein (NE), and Stokes-Einstein-Debye equations and Walden plots were also made for the neat and binary ILs to clarify physical and mobile properties of individual ions. From the temperature-dependent velocity correlation coefficients for neat P-13-TFSA and P-13-FSA, the NE parameter 1-xi was evaluated. The ionicity (electrochemical molar conductivity divided by the NE conductivity from NMR) and the 1-xi had exactly the same values. The rotational and translational motions of P-13 and jump of a lithium ion are also discussed. (C) 2010 American Institute of Physics. [doi:10.1063/1.3505307]

DOI： 10.1063/1.3505307

Web of Science

researchmap

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

Web of Science

researchmap

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

The conformational isomerism of the 1-n-butyl-3-methylimidazolium cation, [C(4)mim], in halide-based ionic liquids [C(4)mim]CI, [C(4)mim]Br, and [C(4)mm]I-was explored by Raman spectroscopy. The [C(4)mim](+) cation exhibits trans gauche conformational isomerism with respect to the N1-C7-C8-C9 dihedral angle of its butyl chain. The thermodynamics of trans-gauche conversion were analyzed through the successful evaluation of the corresponding Gibbs free energy, Delta(iso)G degrees, enthalpy, Delta H-iso degrees, and entropy, Delta S-iso degrees, of conformational isomerization. The values of Delta(iso)G degrees obtained are small (a few units of kJ/mol) and show a slight negative variation with the decrease of the size of the halide anion. On the other hand, Delta H-iso degrees and Delta S-iso degrees values are positive for [C(4)mim]I and decrease with the anion size to yield negative values for [C(4)mim]CI and [C(4)mim]Br. This suggests that the negative electrostatic field around the halide anions stabilizes the gauche isomer from an enthalpic point of view. In order to study the structure and ion-ion interactions in this type of ionic liquids, high-energy X-ray diffraction experiments were performed for [C(4)mim]CI at different temperatures and for supercooled [C(4)mim][Br] at ambient temperature. Molecular dynamics (MD) simulations for these systems were also carried out at several temperatures. Delta(iso)G degrees and Delta H-iso degrees values derived from the simulations qualitatively agree with the experimental ones. Experimental X-ray structure factors are also well reproduced by the simulations. The MD results also allowed the calculation of different spatial distribution functions (SDFs) for the three ionic liquids. Although all SDFs exhibit similar trends; [C(4)mim]I shows a reduced anion density facing the C-2-H atoms of the cation and enhanced anion densities above and below the imidazolium ring plane. This indicates that anions localized near the C-2-H atoms of the cation can stabilize their gauche conformer, an effect that is stronger with smaller anions. This conclusion is also supported by ab initio calculations at the CCSD(T) level for isolated ion pairs.

DOI： 10.1021/jp1044755

Web of Science

researchmap

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

The physicochemical and electrochemical properties of three 1-alkyl-2,3,5-trimethylpyrazolium cation-based room-temperature ionic liquids with various alkyl chain lengths were investigated. The temperature dependences of density, viscosity, and ionic conductivity were obtained by precise measurements. Electrolyte properties of these room-temperature ionic liquids were also examined from the viewpoint of their uses in lithium secondary batteries ([LiCoO(2) positive electrode[electrolyte]lithium metal negative electrode]). It was found that the alkyl chain length affects the charge-discharge performances of cells. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jpowsour.2009.10.081

Web of Science

researchmap

Language：Japanese   Publisher：The Electrochemical Society of Japan  

DOI： 10.5796/electrochemistry.78.687

CiNii Article

CiNii Books

researchmap

Other Link： https://jlc.jst.go.jp/DN/JALC/00354999630?from=CiNii

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

Web of Science

researchmap

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

Raman spectra of the ionic liquid, 1-butyl-3-methylimidazolium bis-(trifluoromethanesulfonyl)amide [C(4)mIm][TFSA] containing a LiTFSA salt were measured for the lithium salt mole fractions X-Li = 0.000, 0.053, 0.106, and 0.171 in the temperature range of 273-350 K. The lithium ion solvation number of 2 at ambient temperature is kept constant in higher temperatures examined in this study. Thermodynamic quantities, such as Gibbs free energy, Delta(iso)G(0); enthalpy, Delta H-iso(0); and entropy, Delta S-iso(0), for conformational isomerism of TFSA(-) from trans to cis isomers in the neat ionic liquid and also in the first solvation sphere of the lithium ion were successfully evaluated for the first time. In the neat ionic liquid, the thermodynamics quantities indicates that the trans isomer is slightly stabilized by enthalpy, though the enthalpic advantage is reduced by entropy to yield nearly equal Gibbs free energy. For the TFSA- in the first solvation sphere of the lithium ion, the Delta(iso)G(0), Delta H-iso(0), and T Delta S-iso(0) were obtained at 298 K to be -4, -9.4, and -5 kJ mol(-1), respectively, and the cis isomer is clearly more favored due to the larger enthalpy relative to that for the neat ionic liquid. However, gas phase quantum calculations for the lithium ion solvated clusters of [Li(TFSA)(2)](-) were reported to be opposite to the experimental isomerization enthalpy. In this study, additional MP2 level ab initio calculations were carried out for the lithium ion solvated clusters with a countercation of 1-ethyl-3-methylimidazolium [C(2)mIm] in gas phase to yield the energy difference of -8.8 kJ mol(-1) from [C(2)mIm][Li(trans-TFSA)(2)] to [C(2)mIm][Li(cis-TFSA)(2)]. The ab initio calculations revealed the important roles of the surrounding imidazolium cation as the second solvation sphere of the lithium ion and agree with the Raman experimental fact that the cis-TFSA(-) solvated to the lithium ion is more stabilized relative to the trans with relatively large enthalpy.

DOI： 10.1021/jp100898h

Web of Science

researchmap

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

To investigate the effects of the cation and anion on the physical properties of room-temperature ionic liquids, the temperature dependences of the viscosity and density of 12 (7 cationic, 6 anionic) room-temperature ionic liquids were measured and analyzed The effects of the cation were investigated using chainlike and cyclic (aromatic and non-aromatic) nitrogen-based room-temperature ionic liquids, and amide-type (N(SO(2)C(x)F(2x+1))(2), x=0, 1,2) anions and anions of various shapes were used to investigate the effects of the anion (C) 2009 Elsevier B V All rights reserved

DOI： 10.1016/j.molliq.2009.10.008

Web of Science

researchmap

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

The microscopic features of binary mixtures formed by an ionic liquid (EMI(+)TFSA(-) or EMI(+)FSA(-)) and a molecular liquid (acetonitrile or methanol) have been investigated by high-pressure infrared spectroscopy. On the basis of its responses to changes in pressure and concentration, the imidazolium C-H appears to exist at least in two different forms, i.e., isolated and associated structures. The weak band at approximately 3102 cm(-1) should be assigned to the isolated structure. CD(3)CN can be added to change the structural organization of ionic liquids. The compression of an EMI(+)TFSA(-)/CD(3)CN mixture leads to the increase in the isolated C-H band intensity. Nevertheless, the loss in intensity of the isolated structures was observed for EMI(+)FSA(-)/CD(3)CN mixtures as the pressure was elevated. In other words, the associated configuration is favored with increasing pressure by debiting the isolated form for EMI(+)FSA(-)/CD(3)CN mixtures. The stronger C-H center dot F interactions in EMI(+)FSA(-) may be one of the reasons for the remarkable differences in the pressure-dependent results of EMI(+)TFSA(-) and EMI(+)FSA(-).

DOI： 10.1063/1.3273206

Web of Science

researchmap

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

DOI： 10.1016/j.molliq.2009.07.003

Web of Science

researchmap

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

Large angle X-ray scattering (LAXS) experiment for 1-ethyl-3-methylimidazolium tetrafluoroborate [EMI(+)] [BF(4)(-)] ionic liquid was carried out at 298 K, to reveal the closest ion-ion interaction in the ionic liquid. The intra-molecular atom-atom correlations based on the molecular geometries in crystals were subtracted from the total pair correlation function to yield the inter-molecular pair correlation function. In the intermolecular pair correlation function, peaks of 3.4, 4.4 and 5.5 angstrom were successfully extracted as the closest ion-ion interactions. Molecular dynamics simulations based on the effective pair potentials were also performed to ascribe the peaks found in the experimentally evaluated inter-molecular pair correlation function at an atomistic level. The X-ray interference function derived from MD simulations and thus Fourier transferred X-ray weighted pair correlation function were reasonably agreement with those obtained by the experiment, the extracted peaks in the experimental inter-molecular pair correlation function can be appropriately attributed to the C (EMI(+)) - F (BF(4)(-)) atom-atom correlations. In addition, artificial MD simulations employed rigid models for the nonplanar and the planar EMI(+) isomers were performed to obtain further insight into the effect of the conformational isomerism on the ion-ion interactions in the ionic liquid. It turned out that the ion-ion interaction, namely the anion orientation around the cation, depends on the conformational isomerism of the cation from the artificial MD simulations. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2008.10.003

Web of Science

researchmap

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

researchmap

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

The conformational behaviors of N-alkyl-N-methylpyrrolidinium bis-(trifluoromethanesulfonyl) amide ionic liquids (alkyl; propyl and butyl, [P-In][TFSA]; n = 3 and 4) were studied by Raman spectroscopy in the frequency range of 200-1700 cm(-1) at different temperatures. Observed Raman spectra in the frequency range 870-960 cm(-1) for [P-13][TFSA] and at 860-950 cm(-1) for [P-14][TFSA] depend on the temperature, indicating that pseudo rotational isomerization of the pyrrolidinium ring exists in the ionic liquids. DFT calculations revealed that the pseudo rotational potential energy surfaces for P-13(+) and P-14(+) ions were similar to each other, i.e., the e6 isomer is the global minimum, whereas the three other isomers e1, e4, and e5 are ca. 3 kJ mol(-1) higher in energy. Optimized geometries with no imaginary frequency were successfully obtained for the e6, e1, and e4 isomers. For both cations, the theoretical Raman spectra of the e6 isomers reproduce well the observed data. To explain their observed Raman spectra in a reasonable way, it is necessary to consider one or more species as predicted by DFT calculations, i.e., the e4 isomer of P-13(+) rather than the e1, or the e1 isomer of P-14(+) rather than the e4. In addition, the torsion energy potentials of the alkyl chains of the cations were scanned by DFT calculations. It turns out that the alkyl chains of the cations prefer all trans conformations. It should be emphasized that the alkyl chains of the pyrrolidinium cations show remarkably different conformational behaviors comparing with those of the imidazolium. The isomerization enthalpies Delta H-iso degrees from the e6 to the e4 isomer of P-13(+) and to e1 of P-14(+) were reasonably estimated from the temperature dependence of Raman spectra based on our proposed assignments to be 2.9 M mol(-1) for P-13(+) and 4.2 kJ mol(-1) for P-14(+) respectively. Thus evaluated experimental Delta H-iso degrees values, which may contain some uncertainties, are in agreement with those predicted by DFT calculations and MD simulations suggesting that pseudo rotational isomerization equilibria are established in the examined N-alkyl-N-methylpyrrolidinium ionic liquids. The conformational behavior of TFSA(-) was also investigated. The Delta H-iso degrees from the trans (trifluoromethyl groups on opposite sides of the S-N-S plane) to the cis isomer were evaluated to be 4.2 kJ mol(-1) for [P-13][TFSA] and 3.5 kJ mol(-1) for [P-14][TFSA], respectively, which are similar to that for the 1-ethyl-3-methylimidazolium ionic liquid.

DOI： 10.1021/jp9009146

Web of Science

researchmap

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

Liquid structures of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide [BDMI+][TFSA(-)] and 1-butyl-2,3-dimethylimidazolium bis(trifluoromethanesulfonyl)amide [BDMI+][TFSA(-)] were studied by large-angle X-ray scattering (LAXS) experiments to elucidate methyl substitution effect at the C2 position of imidazolium cation on the long-range ordering of the ionic liquids. Radial distribution functions for both ionic liquids showed that the intermolecular correlations of ca. 5.5 and 10 angstrom a e significantly different from each other, unlike that of ca. 15 angstrom. MD simulations were also performed. It turns out that the methyl substitution at the C2 position of imidazolium causes variation of the orientation of the nearest neighboring ion-ion interactions without significant changes in the long-range ordering, probably longer than 15 angstrom, of the ionic liquids.

DOI： 10.1246/cl.2009.340

Web of Science

researchmap

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

High-pressure infrared measurements were carried out to observe the microscopic structures of two imidazolium-based ionic liquids, i.e., 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide [EMI+(CF3SO2)(2)N-, EMI(+)TFSA(-)] and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide [EMI+(FSO2)(2)N-, EMI(+)FSA(-)]. The results obtained at ambient pressure indicate that the imidazolium C-H may exist in two different forms, i.e., isolated and network structures. As the sample of pure EMI(+)FSA(-) was compressed, the network configuration is favored with increasing pressure by debiting the isolated form. For EMI(+)TFSA(-)/H2O mixtures, the imidazolium C-H peaks split into four bands at high pressures. The new spectral features at approximately 3117 and 3190 cm(-1), being concentration sensitive, can be attributed to the interactions between the imidazolium C-H and water molecules. The alkyl C-H absorption exhibits a new band at approximately 3025 cm(-1) under high pressures. This observation suggests the formation of a certain water structure around the alkyl C-H groups. The O-H stretching absorption reveals two types of O-H species, i.e., free O-H and bonded O-H. For EMI(+)TFSA(-)/H2O mixtures, the compression leads to a loss of the free O-H band intensities, and pressure somehow stabilizes the bonded O-H configurations. The results also suggest the non-negligible roles of weak hydrogen bonds in the structure of ionic liquids.

DOI： 10.1063/1.3100099

Web of Science

researchmap

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

The physicochemical properties (ionic conductivity, viscosity, density, and self-diffusion coefficient) of tri-n-ethylpentylphosphonium bis(trifluoromethanesulfonyl)amide (TEPP-TFSA) ionic liquid were compared with those of tri-n-ethylpentylammonium bis(trifluoromethanesulfonyl)amide (TEPA-TFSA). Compared with the TEPA-TFSA ionic liquid, the density and viscosity of the phosphorus ionic liquid are lower, although the ionic conductivity and self-diffusion coefficient are higher. The molar conductivities were compared for the values obtained by the electrochemical impedance method (electrochemical conductivity) and the calculated from the pulsed-gradient spin-echo nuclear magnetic resonance method (diffusive conductivity). The comparison shows that active ionic ratios of the TEPP-TFSA ionic liquid were smaller than those of the TEPA-TFSA ionic liquid in the whole temperature, regardless of the lower viscosity of the TEPP-TFSA ionic liquid, and results with high precision were obtained using Walden&apos;s law.

DOI： 10.1039/b820343a

Web of Science

researchmap

Publishing type：Research paper (scientific journal)   Publisher：Society of Computer Chemistry Japan  

DOI： 10.2477/jccj.H2013

researchmap

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

Solvation structures of manganese(II), cobalt(II), nickel(II) and zinc(II) ions in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (EMI(+)TFSA(-)) have been studied by UV-Vis, FT-IR and FT-Raman spectra. The ionic liquid involves TFSA(-) conformers with C-1 (cis) and C-2 (trans) symmetries, and both conformers coexist in equilibrium in the liquid state. The results showed that these metal(II) ions are all six-coordinated with three TFSA(-) ions, i.e., TFSA(-) ligates as a bidentate O-donor in the ionic liquid. Although the metal ion strongly prefers the C-1 conformer in crystals, the metal ion coordinates both the C-1 and C-2 conformers in the liquid state, and the conformational equilibrium in the bulk only slightly shifts to the C-1 conformer in the coordination sphere. We concluded that the conformational equilibrium in the coordination sphere is strongly temperature-sensitive.

DOI： 10.2116/analsci.24.1377

Web of Science

researchmap

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 -&gt; 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

Web of Science

researchmap

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

The solvation structure of the Li(I) species in N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)amide (DEMETFSA) was studied by measuring the Raman and multinuclear NMR spectra of DEMETFSA Solutions containing LiTFSA of various concentrations (0.12 - 1.92 mol kg(-1), [TFSA(-)]/[Li(I)] = 20.0-2.22). It was found from Raman spectra that an intense band clue to the free TFSA(-) anion at around 741 cm(-1) becomes weak, and a new band appears at around 747 cm(-1) with an increase in the concentrations of LiTFSA, and that the pseudoisosbestic point is observed at around 744 cm(-1) in the range of [TFSA(-)]/[Li(I)] = 20.0 - 5.00. From analyses of these Raman bands, the number of TFSA(-) anions bound to the Li+ ion was evaluated to be 1.85 +/- 0.08, and hence, the Li(I) in DEMETFSA Solutions was proposed to exist as [Li(TFSA)(2)](-) in the range of [TFSA(-)]/[Li(I)] = 20.0 - 5.00. Furthermore, in the range of [TFSA(-)]/[Li(I)] = 2.86 - 2.22, the hand observed at around 747 cm(-1) became more strong, and the pseudoisosbestic point disappeared. From these phenomena, it seems that the Li(I) oligomer species are formed in the higher concentration region of LiTFSA. The F-19 NMR signal of the TFSA- anion observed at 42.31 ppm in neat DEMETFSA was found to shift to a higher field linearly with an increase in the concentrations of LiTFSA ([LiTFSA] = 0.00 - 0.99 mol kg(-1), [TFSA(-)]/[Li+] = 20.0 - 3.33), while in a higher concentration range ([LiTFSA] &gt;= 1.26 mol kg(-1), [TFSA(-)]/[Li+] &lt;= 2.86), a slight deviation from linearity was observed. On the other hand, the Li-7 NMR signal did not show ail appreciable shift with increasing LiTFSA concentrations. These results Support that the Li(I) species in DEMETFSA solutions exist as [Li(TFSA)(2)](-) and the Li(I) oligomer species in the low and high concentration regions of LiTFSA, respectively.

DOI： 10.2116/analsci.24.1291

Web of Science

researchmap

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

The Raman spectra for 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide [BMI][TFSA] containing alkaline metal salts of TFSA(-), MTFSA (M = Li, Na, K and Cs), were recorded in the frequency range of 200 - 1800 cm(-1), with varying salt concentrations at 298 K. With Li+ and Na+ ions, at the frequency range of 730 - 760 cm-1, new Raman bands ascribable to the anion bound to the ions appeared at higher frequency relative to that found in the neat ionic liquid. On the other hand, with K+ and Cs+ ions, single Raman bands were solely observed. According to the difference Raman spectra for the ionic liquids containing K+ and Cs+, evaluated by subtracting Raman spectra for the neat ionic liquid, it turned out that two-state approximation, i.e., bulk TFSA(-) and TFSA(-) bound to K+ and Cs+ ions, could hold, as Li+ and Na+-ions. By careful analyses of Raman band intensity arising from bulk TFSA(-) as a function of the salt concentration, the solvation numbers for the respective ions were successfully evaluated to be 1.95 for Li+, 2.88 for Na+, 3.2 for K+ and 3.9 for Cs+, respectively. By taking into account that TFSA(-) acts as a bidentate ligand, the atomic coordination numbers are proposed to be 4, 6, 6 and 8 for Li+, Na+, K+ and Cs+, respectively. Raman shifts for the TFSA- bound to the metal ions relative to that of the bulk TFSA(-) were plotted against the ionic radii for the solvated alkaline metal ions estimated via Shannon's ionic radii, to yield a straight line with a slope of almost unity, suggesting that the electrostatic interaction predominantly operates in the ion-ion interaction between the alkaline metal ions and TFSA(-), as expected. Moreover, the Raman spectra in the frequency range of 370 - 450 cm(-1) strongly depend on the alkaline metal ions, indicating that cis TFSA(-) is favored in the first solvation sphere of the Li+ ion of a relatively small ionic radius, and that such a preferred conformational isomerism of TFSA(-) diminishes with an increase of the ionic radii of the central metal ions.

DOI： 10.2116/analsci.24.1297

Web of Science

researchmap

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

Liquid structure of a low-viscosity ionic liquid, N-methyl-N-propyl- pyrrolidinium bis(fluorosulfonyl) imide ((P13FSI-)-F-*) has been studied by a high-energy X-ray scattering technique at 298 K. The radial distribution function (RDF) indicates that the ionic liquid involves an ordered structure with significant intermolecular interactions at around 6, 10 and 16 A. In order to obtain information of intermolecular interactions in the range r&lt;6 angstrom. where intra- and intermolecular interactions are overlapped, the RDF in terms of g(inter)(r) for the intermolecular interaction was extracted by subtracting the intramolecular g(intra)(r) from the observed g(r). Here, the gin,,,(r) was evaluated by taking into account the distribution of conformers, i.e., the el, e4 and e6 conformers for P-13(+) and the C-1 and C-2 conformers for FSI-. and by knowing their crystal structures. The distribution of the P-13(*) conformers has been established in a previous work. The distribution of the FSI- conformers was determined by Raman spectra of the ionic liquid in the range 270-400 cm(-1) at various temperatures. The ginter(F) thus extracted shows a peak at 3.6 angstrom, which may be ascribed to the specific contact ion-pair interaction Of P-13*FSI-. The Gibbs energy, enthalpy and entropy of conformational change from C2 to C, were evaluated to be -3(2) kJ mol(-1), 6.8(6) kJ mol(-1) and 33(3) J K-1 mol(-1), respectively. (C) 2008 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2008.05.011

Web of Science

researchmap

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

Web of Science

researchmap

Language：English   Publisher：AMER CHEMICAL SOC  

Web of Science

researchmap

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

The conformational landscape of the bis(fluorosulfonyl)amide, [FSI](-), anion was analyzed using data obtained from Raman spectroscopy, molecular dynamics (MD), and ab initio studies. The plotting of three-dimensional potential energy surfaces and the corresponding MD simulation conformer-population histograms show the existence of two stable isomers, C-2 (trans) and C-1 (cis) conformers, and confirm the nature of the anion as a flexible molecule capable of interconversion between conformers in the liquid state. In ionic liquids, the two [FSI](-) conformers coexist in equilibrium, a result confirmed by the Raman data. The implications of the conformational behavior of the ion [FSI](-) are discussed in terms of the solvation properties of the corresponding ionic liquids.

DOI： 10.1021/jp803309c

Web of Science

researchmap

Language：English   Publishing type：Research paper (bulletin of university, research institution)  

researchmap

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

Web of Science

researchmap

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

The conformational landscapes of two commonly used ionic liquid ions, the anion bis(trifluoromethanesulfonyl)amide (Ntf(2)) and the cations N-propyl- and N-butyl-N-methylpyrrolidinium, were investigated using data obtained from Raman spectroscopy, molecular dynamics, and ab initio techniques. In the case of Ntf2, the plotting of three-dimensional potential energy surfaces (PES) and the corresponding molecular dynamics (MD) simulations confirmed the existence of two stable isomers (each existing as a pair of enantiomers) and evidenced the nature of the anion as a flexible, albeit hindered, molecule capable of interconversion between conformers in the liquid state, a result confirmed by the Raman data. In the case of the N,N-dialkylpyrrolidinium cations, the PES show a much more limited conformational behavior of the pyrrolidinium ring (pseudorotation). Nevertheless, such pseudorotation produces two stable isomers with the propyl and butyl side chains in completely different positions (axial-envelope and equatorial-envelope conformations). This result was also confirmed by Raman spectra analyses and MD simulations in the liquid phase. The implications of the conformational behavior of the two types of ions are discussed in terms of the solvation properties of the corresponding ionic liquids.

DOI： 10.1021/jp076997a

Web of Science

researchmap

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

An unusual ionic conduction phenomenon related to the phase transition of a novel phosphonium-cation-based room-temperature ionic liquid (RTIL) is reported; we found that in the phase change upon cooling, a clear increase in ionic conductivity was seen as the temperature was lowered, which differs from widely known conventional RTILs; clearly, our finding of abnormality of the correlation between temperature change and ionic conduction is the first observation in the electrolyte field.

DOI： 10.1039/b809309a

Web of Science

researchmap

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

Web of Science

researchmap

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

Web of Science

researchmap

Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/jp074325e

researchmap

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

5-Azonia-spiro[4.4]nonane tetrafluoroborate [(CH2)(4)N(CH2)(4)](+) BF4- is dissolved in dimethyl carbonate (DMC) to yield two liquid phases, DMC and salt-rich DMC solutions. The molecular structure of the [(CH2)(4)N(CH2)(4)](+) ion in the crystalline state and in the salt-rich DMC solution was studied by means of Raman spectroscopy at 298 K and theoretical DFT calculations. The [(CH2)(4)N(CH2)(4)](+) ion involves two pyrrolidinium (CH2)(4)N rings bridged through the N atom, and each pyrrolidinium ring involves various types of conformation. Theoretical DFT calculations for the [(CH2)(4)N(CH2)(4)](+) ion show that the distorted envelope-envelope conformers of the type E1-E1 and E1-E3 give relatively small energies. Observed Raman spectra of [(CH2)(4)N(CH2)(4)](+) BF4- crystals and the salt-rich DMC solution were satisfactorily explained in terms of the favorable presence of the sole envelope-envelope conformer of the type E1-E1.

DOI： 10.5796/electrochemistry.75.628

Web of Science

researchmap

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

The solvation number and conformation of N,N-dimethylacrylamide (DMAA) in the coordination sphere of the cobalt(II) ion in solution were studied, and compared with those of N,N-dimethylpropionamide (DMPA) by means of FT-Raman and Fr-IR spectroscopy. Both solvents are present as either the planar cis or nonplanar staggered conformer in equilibrium, and the former is more stable in the bulk. As these solvents solvate the metal ion through the carbonyl O atom of the acryl (DMAA) or propionyl (DMPA) group, the solvation structure around the metal ion is highly congested to reduce the solvation number and/or to lead to a conformational geometry change of solvent. It turns out that the solvation number of the cobalt(II) ion is 4 for both DMAA and DMPA at 298 K, and that DMPA changes its conformation upon solvation, whereas DMAA hardly changes. The enthalpy of conformational change Delta H degrees for DMPA is 5 kJ mol(-1) in the bulk, and is -9 kJ mol(-1) in the coordination sphere of the cobalt(II) ion.On the other hand, the Delta H degrees value for DMAA is 9 kJ mol(-1) in the bulk.

DOI： 10.2116/analsci.23.835

Web of Science

researchmap

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

Time-of-flight neutron diffraction measurements were carried out for Li-6/Li-7 isotopically substituted 10 mol % LiPF6-propylene carbonate-d(6) (PC-d(6)) solutions, in order to obtain structural information on the first solvation shell of Li+. Structural parameters concerning the nearest neighbor Li+center dot center dot center dot PC and Li+center dot center dot center dot PF6- interactions were determined through least-squares fitting analysis of the observed difference function, Delta(Li)(Q). It has been revealed that the first solvation shell of Li+ consists in average of 4.5(1) PC molecules with an intermolecular Li+center dot center dot center dot O(PC) distance of 2.04(1) angstrom. The angle Li+center dot center dot center dot O=C bond angle has been determined to be 138(2)degrees.

DOI： 10.1021/jp072597b

Web of Science

researchmap

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

Ethylammonium nitrate (EAN) is a protic room-temperature ionic liquid and classified into an amphoteric solvent. The equilibrium constant K-S = [EtNH2][HNO3] has directly been obtained for the first time by using an ion-selective field effect transistor (ISFET) electrode. The obtained K-S value is of 10(-10.0) mol(2) dm(-6), indicating that the neutral EAN involves HNO3 and EtNH2 molecules as much as 1.0 x 10(-5) mol dm(-3), or the pH (= - log[HNO3]) is 5 at 298 K.

DOI： 10.1246/cl.2007.684

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

CiNii Article

CiNii Books

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.11436/mssj1998.9.39_18

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

The solvation structure of magnesium, zinc(II), and alkaline earth metal ions in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA), and their mixtures has been studied by means of Raman spectroscopy and DFT calculations. The solvation number is revealed to be 6, 7, 8, and 8 for Mg2+, Ca2+, Sr2+, and Ba2+, respectively, in both DMF and DMA. The delta (O-C-N) vibration of DMF shifts to a higher wavenumber upon binding to the metal ions and the shift Delta nu (= nu(bound) - nu(free)) becomes larger, when the ionic radius of the metal ion becomes smaller. The nu (N-CH3) vibration of DMA also shifts to a higher wavenumber upon binding to the metal ions. However, the shift Delta nu saturates for small ions, as well as the transition-metal (II) ions, implying that steric congestion among solvent molecules takes place in the coordination sphere. It is also indicated that, despite the magnesium ion having practically the same ionic radius as the zinc(II) ion of six-coordination, their solvation numbers in DMA are significantly different. DFT calculations for these metalsolvate clusters of varying solvation numbers revealed that not only solvent-solvent interaction through space but also the bonding nature of the metal ion plays an essential role in the steric congestion. The individual solvation number and the Raman shift Delta nu in DMF-DMA mixtures indicate that steric congestion is significant for the magnesium ion, but not appreciable for calcium, strontium, and barium ions, despite the solvation number of these metal ions being large. Copyright (c) 2006 John Wiley & Sons, Ltd.

DOI： 10.1002/jrs.1662

Web of Science

researchmap

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

Conformational structure of the N-butyl-N-methyl-pyrrolidinium (P-14(+)) ion within its bis(trifluoromethanesulfonyl) imide (TFSI-) and bromide salts has been studied by means of DFT calculations and Raman spectroscopy. The P-14(+) ion gives various types of conformations with respect to the pyrrolidinium ring and N-butyl group. DFT calculations indicate that, among others, the eq- and ax-envelope conformers with the N-butyl group at equatorial and axial positions, respectively, against planar C-4 atoms of the envelope pyrrolidinium ring (-NCH2CH2CH2CH2-) are relatively stable, and the former gives the global minimum. It revealed by comparing observed and calculated Raman spectra that the P-14(+) ion is present mainly as the ax-envelope conformer in the P14+Br- crystal, whilst the eq- and ax-envelope conformers are present in equilibrium in the P14+TFSI- ionic liquid. The presence of conformational equilibrium is further supported by Raman spectra measured by varying temperature. It is also established that conformation of the N-butyl group is restricted to the trans-TT, in which the butyl group locates trans against its nearest carbon atom in the pyrrolidinium ring, and all carbon atoms in the butyl chain are located trans each other. (C) 2006 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2006.08.054

Web of Science

researchmap

Language：Japanese   Publisher：九州大学情報基盤センター  

DOI： 10.15017/1467684

CiNii Article

CiNii Books

researchmap

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

Metal-ion clusters involving alkaline earth metal and perchlorate ions, and N,N-dimethylformamide (DMF) have been studied by electrospray ionization mass spectrometry (ESI-MS). Three types of metal-ion clusters, [M(DMF)(n)](2+), [M(ClO4)-(DMF)(n)](+), and [M-2(CIO4)(3)(DMF)(n)](+) (M = Mg, Ca, and Sr) are found. It is proposed on the basis of DFT calculations that the metal ion in the [M-2(CIO4)(3)(DMF)(6)](+) clusters is six-coordinated with three mu-CIO4- ions and three DMF molecules.

DOI： 10.1246/cl.2006.1118

Web of Science

researchmap

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

The dielectric changes of thermochromic compounds, [Cu(dieten)(2)]X-2 (X = BF4 and ClO4, dieten = NN-diethylethylenediamine), have been induced by the transformation between square-planar and distorted-square-planar.

DOI： 10.1246/cl.2006.1114

Web of Science

researchmap

Cobalt(II) chloro complexation has been studied by titration calorimetry and spectrophotometry in solvent mixtures of N-methylformamide (NMF) and N,N-dimethylformamide (DMF). It revealed that a series of mononuclear CoCln n (2-n)+ (n=1-4) complexes are formed in the mixtures of NMF mole fraction x NMF =0.05 and 0.25, and the CoCl + , CoCl 3 - and CoCl 4 2- complexes in the mixture of x NMF =0.5, and their formation constants, enthalpies and entropies were obtained. As compared with DMF, the complexation is markedly suppressed in the mixtures, as well as in NMF. The decreasing formation constant of CoCl + with the NMF content is mainly ascribed to the decreasing formation entropy. DMF is aprotic and thus less-structured, whereas NMF is protic to form hydrogen- bonded clusters. In DMF-NMF mixtures, solvent clusters in neat NMF are ruptured to yield new clusters involving DMF, the structure of which depends on the solvent composition. The entropy of formation of CoCl + will be discussed in relation to the liquid structure of DMF, NMF and their mixtures. © 2006 Akadémiai Kiadó.

DOI： 10.1007/s10973-006-7643-x

Scopus

researchmap

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

Metal ions are solvated in solution, and, in a sterically congested organic solvent, those solvent molecules that are simultaneously bound to the metal ion will be subject to consequential steric interactions through space. The molecular structure of a solvent, particularly that of any functional groups in the vicinity of the coordinating atom to the metal ion, plays a key role in the solvation steric effect. Weak solvation steric effects lead to a distorted octahedral structure for six-coordinate transition-metal(II) ions, whereas strong steric effects lead to a decreased solvation number. In particular cases, the conformation of a solvent may undergo a change in response to coordination to the metal ion. Solvation steric effects play a decisive role in reaction thermodynamics and kinetics of the metal ion. Here, we show our recent results on solvation steric effects in terms of structure and thermodynamics, particularly, the conformational change of solvent and its effect on the metal-ion complexation.

DOI： 10.1351/pac200678081595

Web of Science

researchmap

Language：Japanese   Publishing type：Research paper (scientific journal)  

researchmap

Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

researchmap

The structure of bis(trifluoromethanesulfonyl) imide (TFSI) in the liquid state has been studied by means of Raman spectroscopy and DFT calculations. Raman spectra of 1-ethyl-3-methylimidazolium (EMI + ) TFSI - show relatively strong bands arising from TFSI - at about 398 and 407 cm - . Interestingly, the 407 cm -1 band, relative to the 398 cm -1 one, is appreciably intensified with raising temperature, suggesting that an equilibrium is established between TFSI - conformers in the liquid state. According to DFT calculations followed by normal frequency analyses, two conformers of C 2 and C 1 symmetry, respectively, constitute global and local minima, with an energy difference 2.2-3.3 kJ mol -1 . The wagging ω-SO 2 vibration appears at 396 and 430 cm -1 for the C 1 conformer and at 387 and 402 cm -1 for the C 2 one. Observed Raman spectra over the range 380-440 cm -1 were deconvoluted to extract intrinsic bands of TFSI - conformers, and the enthalpy of conformational change from C 2 to C 1 was evaluated. The enthalpy value is in good agreement with that obtained by theoretical calculations. We thus conclude that a conformational equilibrium is established between the C 1 and C 2 conformers of TFSI - in the liquid EMI + TFSI - , and the C 2 conformer is more favorable than the C 1 one. © 2006 American Chemical Society.

DOI： 10.1021/jp0612477

Scopus

researchmap

Raman spectra of aprotic N,N-dimethylformamide (DMF) and protic N-methylformamide (NMF) mixtures containing manganese(II), nickel(II), and zinc(II) perchlorate were obtained, and the individual solvation numbers around the metal ions were determined over the whole range of solvent compositions. Variation profiles of the individual solvation numbers with solvent composition showed no significant difference among the metal systems examined. In all of these metal systems, no preferential solvation occurs in mixtures with DMF mole fraction of x DMF &lt; 0.5, whereas DMF preferentially solvates the metal ions at x DMF &gt; 0.5. The liquid structure of the mixtures was also studied by means of small-angle neutron scattering (SANS) and low-frequency Raman spectroscopy. SANS experiments demonstrate that DMF molecules do not appreciably self-aggregate in the mixtures over the whole range of solvent composition. Low-frequency Raman spectroseopy suggests that DMF molecules are extensively hydrogen-bonded with NMF in NMF-rich mixtures, whereas NMF molecules extensively self-aggregate in DMF-rich mixtures, although the liquid structure in neat NMF is partly ruptured. The bulk solvent structure in the mixtures thus varies with solvent composition, which plays a decisive role in developing the varying profiles of the individual solvation numbers of metal ions in the solvent mixtures. © 2006 American Chemical Society.

DOI： 10.1021/jp054972a

Scopus

researchmap

Aprotic N,N-dimethylpropionamide (DMPA) and N,N,N′,N′- tetramethylurea (TMU) are both strong donor solvents and coordinate to metal ions through the carbonyl oxygen atom. These solvents show a different conformational aspect in the bulk phase, i.e., DMPA exists as either a planar cis or a nonplanar staggered conformer, while TMU exists in a single planar cis conformer. It has been established that the manganese(II) ion is solvated by five molecules in both solvents. Interestingly, although the planar cis conformer of DMPA is more favorable than the nonplanar staggered one in the bulk phase, the reverse is the case in the coordination sphere of the metal ion, i.e., a conformational change occurs upon solvation. To reveal the thermodynamic aspect of this conformational change, the complexation of Mn(II) with bromide ions in DMPA and TMU has been studied by titration calorimetry at 298 K. It was found that the Mn(II) ion forms mono-, di- and tri-bromo complexes in both solvents, and their formation constants, enthalpies and entropies were obtained. The ΔH 1 o value for MnBr + strongly depends on the solvent, i.e., it is positive (19.4 kJ-mol -1 ) in DMPA and negative (-8.7 kJ-mol -1 ) in TMU, whereas the ΔH 2 o and ΔH 3 o values for the stepwise formation of MnBr 2 and MnBr 3 - are both small and negative. The enthalpy of transfer Δ t H o from DMPA to TMU, which is evaluated on the basis of the extrathermodynamic TATB assumption, is 25.5 kJ-mol -1 for Mn 2+ and -3.6 kJ-mol -1 for MnBr + . These values indicate that the difference between the formation enthalpy of MnBr + in the two solvents, ΔH 1 o (DMPA) - ΔH 1 o (TMU), is mainly ascribed to the value of Δ t H o (Mn 2+ ). It is found that the metal ion is also five-coordinated in the monobromo complex, MnBr(DMPA) 4 + . The enthalpy for the conformational change of DMPA from its planar cis to the nonplanar staggered form is evaluated to be -11 and -5.5 kJ-mol -1 for Mn(DMPA) 5 2+ and MnBr(DMPA) 4 + , respectively. Note that these values are significantly smaller than the corresponding value (5.0 kJ-mol -1 ) in the bulk phase. We thus conclude that, although steric hindrance among solvent molecules is reduced by replacing one DMPA of Mn(DMPA) 5 2+ with the relatively small bromide ion, DMPA molecules are still sterically hindered in the MnBr(DMPA) 4 + complex. © 2005 Springer Science+Business Media, Inc.

DOI： 10.1007/s10953-005-8516-9

Scopus

researchmap

Raman spectra of liquid 1-ethyl-3-methylimidazolium (EMI + ) salts, EMI + BF 4 - , EMI + PF 6 , EMI + CF 3 SO 3 - , and EMI + N(CF 3 SO 2 ) 2 - , were measured over the frequency range 200-1600 cm -1 . In the range 200-500 cm -1 , we found five bands originating from the EMI + ion at 241, 297, 387, 430, and 448 cm -1 . However, the 448 cm -1 band could hardly be reproduced by theoretical calculations in terms of a given EMI + conformer, implying that the band originates from another conformer. This is expected because the EMI + involves an ethyl group bound to the N atom of the imidazolium ring, and the ethyl group can rotate along the C-N bond to yield conformers. The torsion energy for the rotation was then theoretically calculated. Two local minima with an energy difference of ca. 2 kJ mol -1 were found, suggesting that two conformers are present in equilibrium. Full geometry optimizations followed by normal frequency analyses indicate that the two conformers are those with planar and nonplanar ethyl groups against the imidazolium ring plane, and the nonplanar conformer is favorable. It elucidates that bands at 241, 297, 387, and 430 cm-1 mainly originate from the nonplanar conformer, whereas the 448 cm-1 band does originate from the planar conformer. Indeed, the enthalpy for conformational change from nonplanar to planar EMI + experimentally obtained by analyzing band intensities of the conformers at varying temperatures is practically the same as that evaluated by theoretical calculations. We thus conclude that the EMI + ion exists as either a nonplanar or planar conformer in equilibrium in its liquid salts. © 2005 American Chemical Society.

DOI： 10.1021/jp053476j

Scopus

researchmap

Chloride complexation of cobalt(II), nickel(II) and zinc(II) ions has been studied by calorimetry and spectrophotometry in N-methylformamide (NMF) containing 1.0 mol-dm -3 (n-C 4 H 9 ) 4 NClO 4 as an ionic medium at 298 K. A series of mononuclear complexes, MCl n (2 -n)+ (M=Co, Ni and Zn) with n = 1, 3 and 4 for cobalt(II), n = 1 for nickel(II), and n = 1-4 for zinc(II), are formed and their formation constants, enthalpies and entropies were obtained. It revealed that complexation is suppressed significantly in NMF relative to that in N,N-dimethylformamide (DMF) in all metal systems examined. The suppressed complexation in NMF is mainly ascribed to the smaller formation entropies in NMF reflecting that the solvent-solvent interaction or solvent structure in the bulk NMF is much stronger than that in the bulk DMF. Formation entropies, ΔS 1 o , of the monochloro complex in DMF, dimethyl sulfoxide and NMF are well correlated with the Marcus&#039; solvent parameter, ΔΔ v S o /R, according to ΔS 1 o /R = aΔΔ v S o /R+b. The a value is negative and similar in all metal systems examined, whereas the b value depends on the metal system. When a gaseous ion is introduced into a solvent, the ionic process of solvation is divided into two stages: the ion destroys the bulk solvent structure to isolate solvent molecules at the first stage and the ion then coordinates a part of isolated solvent molecules around it at the second stage. We propose that the a and b values may reflect the changes in the freedom of motion of solvent molecules at the first and second stages, respectively, of the ionic process of solvation. © 2005 Springer Science+Business Media, Inc.

DOI： 10.1007/s10953-005-5114-9

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

The rate of the solvent substitution reaction, CoCl3S -+Cl-→CoCl42-+S (S-solvent) has been studied by means of stopped flow spectrophotometry in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and the rate constant kf, and the activation enthalpy ΔfH≠ and entropy ΔfS≠ have been determined. The negative and large ΔfS≠ values of -38 and -68 J K-1 mol-1 in DMSO and DMF, respectively, evidently indicate that an associative mechanism operates or the five-coordinate species CoCl 4S2- forms at the transition state. The corresponding ΔfH≠ values are 48 and 36 kJ mol-1 in DMSO and DMF, respectively. To discuss solvation enthalpy difference of the CoCl4S2- at the transition state in the solvents, the transfer enthalpy ΔtH≠ of the activated species from DMF to DMSO was evaluated by combining the ΔfH ≠ values and the enthalpies of transfer ΔtH° of CoCl3- and Cl- from DMF to DMSO. The ΔtH≠ value thus obtained is 18 kJ mol -1, the value indicating that the solvation enthalpy of the activated species in DMF is more negative than that in DMSO despite that the electron-pair donating ability of DMF is weaker than that of DMSO. This implies that the entering chloride ion suffers from an appreciable steric hindrance of DMSO at the transition state. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2004.10.024

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Chloro and bromo complexation of the manganese(II) ion has been studied in N-methyl-2-pyrolidone (NMP) by titration calorimetry at 298 K. It is found that the manganese(II) ion forms a series of mononuclear MnCln (2-n)+ (n=1-4) and MnBrn(2-n)+ (n=1-3) complexes in NMP, and their formation constants, enthalpies and entropies have been obtained. The complexation in NMP is significantly weaker than that in N,N-dimethylpropionamide (DMPA), while it is almost to the same extent as that in N,N-dimethylacetamide (DMA), despite that these solvents coordinate to the metal ion through the carbonyl oxygen atom, and their electron-pair donating abilities are similar. This indicates that steric interaction among solvent molecules coordinated to the metal ion is significantly weaker in NMP than that in DMPA, while it is almost to the same extent in NMP and DMA. The manganese(II) ion is five-solvated in DMPA, and six-solvated in DMA. The complexation behavior in NMP implies that the manganese(II) ion is six-solvated in NMP, like in DMA. As NMP is a planar trans analogue of DMPA with respect to the propionyl group CH3CH2(CO)-, the magnitude of solvation steric effect around the metal ion for the planar trans DMPA may be similar to that for DMA. It is thus concluded that the local conformation, particularly around the coordinating carbonyl oxygen atom, plays a decisive role in the solvation steric effect of the metal ion in aprotic amide solvents. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2004.10.028

Scopus

researchmap

Solvation structure of the zinc(II) jon in N,N-dimethylpropionamide (DMPA) was studied by Raman spectroscopy at varying temperature and by quantum mechanical calculations. No significant ion-pair formation was found for the Zn(ClO 4 ) 2 solution in the molality range m Zn &lt; 1.5 mol kg -1 , and the solvation number of the zinc(II) ion was determined to be 4, indicating that 6-coordination of DMPA is sterically hindered. Interestingly, DMPA molecules are under equilibrium between planar cis and nonplanar staggered conformers, and the latter is more preferred in the coordination sphere, while the reverse is the case in the bulk. The ΔG°, ΔH°, and TΔS° values of conformational change from planar cis to nonplanar staggered in the coordination sphere were obtained to be -0.9, -8.5, and -7.5 kJ mol -1 , respectively. Density functional theory (DFT) calculations show that the planar cis conformer is more favorable than the nonplanar staggered one in the 1:2 cluster, as is the case for a single DMPA molecule and H(DMPA) - , indicating that there hardly occurs solvent-solvent interaction through the metal ion in the Zn 2+ -DMPA 1:2 cluster. On the other hand, the SCF energy of [Zn(planar cis-DMPA) 4-n (nonplanar staggered DMPA) n ] 2+ (n = 0-4) decreases with increasing n, implying that the nonplanar staggered conformer is preferred in the solvate ion. It is thus concluded that solvent-solvent interaction through space, or solvation steric effect, plays a crucial role in the conformational equilibrium in the coordination sphere of the four-solvate metal ion. © 2005 American Chemical Society.

DOI： 10.1021/jp044763a

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Solvation structure of the calcium ion in N,N-dimethylpropionamide (DMPA) has been studied by titration Raman spectroscopy by varying molality of Ca(ClO4)2 at 298 K and by varying temperature. Raman spectra of the solutions show bands ascribable to the planar cis and non-planar staggered conformers of free DMPA in the bulk and bound DMPA in the coordination sphere of the metal ion. The solvation number of the calcium ion in DMPA is found to be six, which is appreciably smaller than that in water, indicating that a steric hindrance operates among DMPA molecules simultaneously bound to the metal ion. It is also indicated that the planar cis conformer is preferred to the non-planar staggered conformer in the bulk, while it is much less preferred around the calcium ion. The enthalpy for conformational change from the planar cis to the non-planar staggered ΔH°is then evaluated to be 0.6 kJ mol-1 for those bound to the calcium ion. The value is significantly larger (or more endothermic) than that of the corresponding conformational change (-11 kJ mol-1) around the manganese(II) ion, indicating that the enthalpy for the conformational change depends strongly on the metal ion. The ΔH°value seems to sensitively change depending on the solvation structure, particularly the ionic radius. © 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2004.07.010

Scopus

researchmap

Complexation of copper(II) ion with some amide solvents such as N-methylformamide (NMF), formamide (FA), N,N-dimethylacetamide (DMA) and N-methylacetamide (NMA) has been studied by titration calorimetry in acetonitrile containing 0.1 mol dm -3 (C 2 H 5 ) 4 ClO 4 as an ionic medium at 298 K. These amides coordinate to the metal ion to form a series of mononuclear complexes, and their formation constants, enthalpies and entropies have been obtained. Thermodynamic parameters of formation of Cu(NMF) 2+ and Cu(FA) 2+ are not significantly different from those of Cu(DMF) 2+ (DMF: N,N-dimethylformamide), implying that a strong hydrogen-bonded structure of liquid NMF and FA are practically ruptured in the acetonitrile solution examined. The formation of Cu(DMA) 2+ and Cu(NMA) 2+ are appreciably less exothermic than the respective formation of Cu(DMF) 2+ and Cu(NMF) 2+ complexes, implying that the presence of the acetyl group causes steric hindrance upon its coordination to the metal ion. © 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.tca.2005.01.023

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：KLUWER ACADEMIC/PLENUM PUBL  

The distribution of 1,10-phenanthroline (phen) in micellar solutions of the nonionic surfactants Triton X and C12En with varying poly (ethylene oxide) chain lengths has been studied by potentiometry, calorimetry, and fluorometry at 298 K. Micelles accommodate 1,10-phenanthroline according to the reaction, phen + Y-m = Y-m(phen), where Ym denotes a surfactant molecule aggregated in micelles. The constant Km for the reaction of Triton X increases as a linear function of n*, the number of ethylene oxide (EO) groups, as K-m = K(EO)n* + K-c. Nonzero K-EO and K-c values suggest a heterogeneous inner structure of the micelle, i.e., the hydrophobic core surrounded by a hydrophilic poly (ethylene oxide) (PEO) shell. On the basis of molar volumes, the intrinsic thermodynamic parameters of transfer of 1,10-phenantholine were extracted. The enthalpy and entropy of transfer of 1,10-phenanthroline from the PEO shell to the core are found to be small and negative. By using KEO and Kc values for C12En obtained by fluorometry, individual fluorescence spectra of 1,10-phenanthroline in the PEO shell and core were extracted. The fluorescence intensity of 1,10-phenathroline accommodated in the core, like in organic solvents, is significantly reduced relative to that in water. These facts indicate that the aromatic rings of 1,10-phenanthroline penetrate into the hydrophobic core, while its hydrophilic N site is still hydrated in the PEO shell.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Hysteretic behavior was found on the heat of protonation of diethylenetriamine (dien) in aqueous solution at 298 K. We propose the presence of two conformers for Hdien+, which have significantly different proton affinities. Mutual transformation between the conformers may be practically forbidden, but is strongly accelerated upon their protonation to form H2dien2+.

DOI： 10.1246/cl.2004.186

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

The methyl group and oxygen in the propionyl group CH3CH2CO- of N,N-dimethylpropionamide (DMPA) have been previously shown to be planar cis. The present measurements of Raman spectra at varying temperature indicate the presence of another isomer in equilibrium with the planar cis one. It is suggested that, according to our ab initio MO calculation, it is a non-planar staggered conformer with a C-C-C-O dihedral angle of ca. 90°, i.e. the methyl group of the propionyl group is located above the amide O-C-N plane. The equilibrium shifts to the non-planar staggered conformer with increasing temperature. The ΔH° value for the conformational change from the planar cis to non-planar staggered conformer in the bulk is 5.0 kJ mol-1, which is in good agreement with the theoretical ones (6.6 kJ mol-1). The manganese(II) ion is five-solvated in DMPA, and it is elucidated that the non-planar staggered conformer is preferred to the planar cis conformer for DMPA molecules bound to the manganese(II) ion. This is ascribed to the solvation steric effect among solvent molecules bound to the metal ion. The ΔH° value for the conformational change of the bound DMPA from the planar cis to non-planar staggered conformation is -11 kJ mol-1.

DOI： 10.1039/b302143b

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Raman spectra of solutions of manganese(II) perchlorate with varying molality were measured in 1,1,3,3-tetramethylurea (TMU), N,N-dimethylformamide (DMF) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane O=C-N bending vibration at 660 cm-1 of DMF and the stretching N-CH3 vibration at 740 cm-1 of TMU show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. These Raman spectra were deconvoluted and the bound solvent band (vbound) to the metal ion was extracted from the free solvent band (vfree). The number of solvent molecules bound to the metal ion or the individual solvation number n in a solvent mixture, nTMU and nDMF, were evaluated by analyzing the intensity decrease of the free solvent band with increasing molality of the metal ion. It turned out that the manganese(II) ion is five-coordinated in neat TMU, while it is six-coordinated in the DMF-TMU mixture over the range of TMU content xTMU &lt
0.75, as well as in neat DMF. Interestingly, the relationship nTMU/nT &lt
xTMU (nT = nDMF + nTMU holds over the whole range of the mixtures, clearly indicating that DMF molecules preferentially solvate the metal ion due to the steric hindrance between bound TMU molecules. The frequency shift of the bound band relative to the free band, ΔvTMU = vbound - vfree, of TMU remains practically constant over the range xTMU &lt
0.75, and appreciably increases in neat TMU, while the ΔvDMF gradually decreases with increasing xTMU. The variation of ΔvTMU parallels with that of nT. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0167-7322(02)00151-4

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Formation thermodynamics of binary and ternary lanthanide(III) (Ln = La, Ce, Nd, Eu, Gd, Dy, Tm, Lu) complexes with 1,10-phenanthroline (phen) and the chloride ion have been studied by titration calorimetry and spectrophotometry in N,N-dimethylformamide (DMF) containing 0.2 mol-dm-3 (C 2H5)4NClO4 as a constant ionic medium at 25°C. In the binary system with 1,10-phenanthroline, the Ln(phen)3+ complex is formed for all the lanthanide(III) ions examined. The reaction enthalpy and entropy values for the formation of Ln(phen)3+ decrease in the order La &gt
Ce &gt
Nd, then increase in the order Nd &lt
Eu &lt
Gd &lt
Dy, and again decrease in the order Dy &gt
Tm &gt
Lu. The variation is explained in terms of the coordination structure of Ln(phen)3+ that changes from eight to seven coordination with decreasing ionic radius of the metal ion. In the ternary Ln3+-Cl- -phen system, the formation of LnCl(phen) 2+, LnCl2(phen)+, and LnCl3(phen) was established for cerium(III), neodymium(III), and thulium(III), and their formation constants, enthalpies, and entropies were obtained. The enthalpy and entropy values are also discussed from the structural point of view.

DOI： 10.1023/A:1021471907261

Scopus

researchmap

Language：English   Publishing type：Research paper (international conference proceedings)  

Thermodynamic and structural aspects on the solvation steric effect for yttrium(III) and lanthanide(III) ions in DMF, DMA and their mixtures will be reviewed. The yttrium(III) and lanthanide(III) ions form outer- and inner-sphere bromo complexes in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA), respectively, and an equilibrium geometry is established in the mixture. This is ascribed to the solvation steric effect of DMA, i.e. the simultaneous coordination of bulky DMA molecules around the metal ion causes a severe steric hindrance among them, allowing replacement of the solvent molecule with the penetrating bromide ion into the first-coordination sphere. Solvation steric effects for the metal(III) ion bring about appreciable changes in the bond length and solvation number. The results from titration calorimetry, EXAFS, 89Y-NMR and titration Raman spectroscopy will be discussed. © 2002 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0010-8545(01)00448-9

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

The Raman spectra of neodymium(III), gadolinium(III) and thulium(III) perchlorate solutions of varying salt molalities were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane O C-N bending vibration at 660 cm-1 of DMF and the stretching N-CH3 vibration at 740 cm-1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. In DMF-DMA mixtures, the magnitude of the shift for the δ(O C-N) and (N-CH3) vibrations of bound solvent molecules, Δ DMF, and Δ DMA, respectively, depends on the solvent composition, and the variation profile of Δ DMA is in parallel with that of the Ln-O(solvent) bond length. The number of solvent molecules bound to the metal ion or the individual solvation number in a solvent mixture, nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It is indicated that a strong solvation steric effect operates among bound solvent molecules, i.e., the total solvation number decreases with increasing DMA content, and the variation profile depends on the metal ion. The individual solvation number of DMA was found to be 3 at around xDMA = 0.4 for all the metal systems examined.

DOI： 10.1039/b204162f

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Academic Press Inc.  

Formation of cobalt(II)-thiocyanato complexes in nonionic surfactant solutions of poly(ethylene oxide) type with varying poly(ethylene oxide) chain lengths of 7.5 (Triton X-114), 30 (Triton X-305), and 40 (Triton X-405) has been studied by titration spectrophotometry and calorimetry at 298 K. Data were analyzed by assuming formation of a series of ternary complexes Co(NCS)nYm (2-n)+ (Y = surfactant) with an overall formation constant βnm. In all the surfactant systems examined, data obtained can be explained well in terms of formation of Co(NCS)+ and Co(NCS)2 in an aqueous phase (aq), and Co(NCS)4Y2- in micelles, and their formation constants, enthalpies, and entropies have been determined. The β41/β20 ratio increases and the corresponding enthalpy becomes significantly less negative with an increasing number of ethylene oxide groups. This suggests that micelles of these nonionic surfactants have a heterogeneous inner structure consisting of ethylene oxide and octylphenyl moieties. Indeed, on the basis of molar volumes of ethylene oxide and octylphenyl groups, intrinsic thermodynamic parameters have been extracted for the reaction Co(NCS)2(aq) + 2NCS-(aq) = Co(NCS)4Y2- (ΔrG°, ΔrH°, and ΔrS°) at each moiety. The ΔrG°, ΔrH°, and ΔrS° values are -16 kJ mol-1, -15 kJ mol-1, and 3 J K-1 mol-1, respectively, for the ethylene oxide moiety, and -15 kJ mol-1, -70 kJ mol-1, and -183 J K-1 mol-1 for octylphenyl. Significantly less negative ΔrH° and ΔrS° values for ethylene oxide imply that the hydrogen-bonded network structure of water is extensively formed at the ethylene oxide moiety, and the structure is thus broken around the Co(NCS)4 2- complex with weak hydrogen-bonding ability. © 2001 Academic Press.

DOI： 10.1006/jcis.2001.7457

Scopus

researchmap

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

The distribution thermodynamics of 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmphen) in micelles of the non-ionic surfactant Triton X-100 were studied by potentiometry and titration calorimetry at 298 K. Both of these ligands form HL+ and HL2+ (L = phen and dmphen) in acidic solution. Their formation constants were determined in aqueous solutions containing various concentrations of Triton X-100, and were found to decrease with increasing concentration of the surfactant. The decrease is explained in terms of accommodation of neutral phenanthrolines in micelles by taking into account the surfactant solution as a heterogeneous solvent mixture. The case in which the surfactant is treated as the third reactant was also examined, and thermodynamic parameters for the interaction between the surfactant and phenanthrolines, i.e. the Gibb's energies, enthalpies and entropies of transfer of phenanthrolines from aqueous solution to a micellar pseudo-phase, were obtained. The Gibb's energies of transfer of the neutral ligand L are -8.2 and -11.7 kJ mol(-1) for L = phen and dmphen, respectively. The corresponding enthalpies of transfer are both small and negative, implying that these neutral 1,10-phenanthrolines are still strongly hydrated in micelles, as well as in water, through the hydrophilic nitrogen sites.

Web of Science

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Raman spectra of solutions of manganese(II), nickel(II), copper(II) and zinc(II) perchlorate with varying molality were measured in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures by titration Raman spectroscopy at 298 K. The in-plane O=C-N bending vibration at 660 cm-1 of DMF and the stretching N-CH3 vibration at 740 cm-1 of DMA show an appreciable shift to a higher frequency upon coordination of the solvent molecules to the metal ion. These Raman spectra were deconvoluted and the bound solvent bands (vbound) to the metal ion were extracted from the free solvent band (vfree). The number of solvent molecules bound to the metal ion or the individual solvation number n in a solvent mixture, i.e., nDMF and nDMA for DMF and DMA, respectively, were evaluated by analyzing the intensity decrease of the free solvent bands with increasing molality of the metal ion. It turned out that the manganese(II) ion is six-coordinated over the whole solvent composition range in the mixtures, i.e., nDMF+nDMA=6, and the relationship nDMF/nDMA=xDMF/xDMA, where x denotes the mole fraction of the solvent, holds in the mixture. With regard to the zinc(II) ion, the total solvation number decreases from 6 with increasing xDMA in the mixtures. In neat DMA, two bound solvent bands are extracted, indicating that two species, Zn(DMA)6 2+ and Zn(DMA)4 2+, coexist in equilibrium. With the six-coordinate zinc(II) solvated ion, the relationship nDMF/nDMA&gt
xDMF/xDMA holds in the mixture. This shows that the solvation steric effect of DMA operates for the six-coordinate zinc(II) solvated ion, unlike for the manganese(II) one. The copper(II) ion is six-coordinated, although the coordination structure is strongly distorted owing to the Jahn-Teller effect. Indeed, two bands ascribable to the solvents bound at the equatorial and axial positions were extracted. In the mixtures, the relationship nDMF/nDMA&gt
xDMF/xDMA holds for solvents bound at the equatorial position, i.e., the solvation steric effect operates among solvent molecules, while the relationship nDMF/nDMA≤xDMF/xDMA holds for solvents bound at the axial position. This is expected because the Cu-O(solvent) bond length is longer for the solvent at the axial position, and the electron-pair donating ability is slightly stronger for DMA. The magnitude of the shift Δv (=vbound-vfree) depends strongly on the metal ion. Indeed, the Δv values in neat DMF and DMA vary according to the relationship Δv=(ar)-n, a function of the ionic radius r of the metal ion, and the parameters a and n were evaluated. The shift Δv in the mixtures implies that the M-O(DMF) bond length in the M(DMF)6-n(DMF)n 2+ solvated ion is elongated with increasing coordination number nDMA of DMA.

DOI： 10.1039/b107342g

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Individual solvation numbers around the nickel(II) ion have been determined by titration Raman spectroscopy in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) mixtures at 298 K. The in-plane bending vibration (δ(O=C-N)) of DMF and the stretching vibration (v(N-CH3)) of DMA were used in the present analysis. These Raman bands of solvent molecules shift to higher frequencies upon coordination of the solvent molecules to the metal ion. By analyzing the band intensities of free and bound solvent molecules with increasing concentration of the metal ion, the solvation number around the metal ion can be evaluated. Because the individual solvation numbers of DMF and DMA around the nickel(II) ion in the mixture are determined independently, the total solvation number is obtained as their sum. It was found that the total solvation number remains 6 in all mixtures of the DMA mole fraction x = 0 - 1. Although DMF and DMA have practically the same electron-pair donor capacities, the nickel(II) ion prefers DMF to DMA, and an equal solvation number is attained at x = 0.75. This is ascribed to the solvation steric effect of DMA.

DOI： 10.2116/analsci.17.323

Scopus

PubMed

researchmap

Language：English   Publishing type：Research paper (scientific journal)  

Adduct formation of the inert complexes Ru(phen)32+, Co(phen)33+ and Si(phen)34+ with 1,10-phenanthroline (phen) has been studied by potentiometry and calorimetry in aqueous solution containing 0.1 mol dm-3 NaCl as an ionic medium at 298 K. Formation of a 1 : 1 adduct, in which planar 1,10-phenanthroline molecules are stacked, has been found for all the inert complexes and their formation constants, enthalpies and entropies were obtained. Adduct formation constants are hardly influenced by the ionic charges of the metal center. The enthalpy values are all negative, indicating that a specific π-π interaction operates between stacked 1,10-phenanthroline molecules. The corresponding entropy values are positive for Ru(phen)32+ and Co(phen)33+, while it is negative for Si(phen)34+. The positive entropies indicate that reduction of hydrophobic hydration upon stacking also plays a key role in the adduct formation. Both enthalpy and entropy values significantly decrease with increasing charge, and they strongly compensate to give similar formation constants. This implies that hydrophobic hydration around aromatic rings within the inert complexes is reduced to a greater extent with increasing charge, Ru(phen)32+ &lt
Co(phen)33+ &lt
Si(phen)34+. 1,10-Phenanthroline forms protonated H(phen)+ and H(phen)2+ species in an acidic solution, and 1,10-phenanthroline molecules are stacked in the latter. The enthalpy and entropy of formation of H(phen)2+ are significantly negative, also indicating that π-π interaction play an essential role in the formation of H(phen)2+. On the other hand, both the enthalpy and entropy of solution of 1,10-phenanthroline remain unchanged in solution containing NaCl over the range 0.05-1 mol dm-3, suggesting that hydrophobic hydration shells are restricted at the vicinity of 1,10-phenanthroline.

DOI： 10.1039/b003854g

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Formation of chloro-complexes of AlIII has been studied by spectrophotometry, calorimetry and 27Al NMR spectroscopy in N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) at 298 K. Formation constants of the AlIII-Cl- system were obtained spectrophotometrically on the basis of those of the NiII-Cl- system by means of competitive complexation between AlIII and NiII ions. All data can be explained well in terms of formation of mono- and dichloro-complexes of AlIII in DMF, and mono-and trichloro-complexes in DMA, and their formation constants, formation enthalpies and entropies were determined. Formation entropies of chloro-complexes of AlIII in DMF are significantly less than the corresponding values of GaIII and InIII. It is thus suggested that the formation of inner-sphere AlCl2+ and AlCl2+ is strongly suppressed, and the chloro-complexes are present mainly as the outer-sphere [Al(DMF)6]3+Cl- and [Al(DMF)6]3+2Cl- complexes in DMF. This is indeed evidenced by the 27Al NMR. On the other hand, in DMA, the large and positive enthalpy and entropy values indicate that the mono- and trichloro-complexes are inner-sphere ones, AlCl2+ and AlCl30. The 27Al NMR signal ascribed to AlCl3 is largely shifted to a lower magnetic field indicating that the complex is tetrahedrally four-coordinated, [AlCl3(DMA)]0, and that a geometry change takes place upon complexation of the trichloro-complex in DMA.

DOI： 10.1039/a707898f

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Structural parameters of solvated neodymium(III), gadolinium(III), thulium(III) and ytterbium(III) ions in N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA) and their mixtures have been obtained by an extended X-ray absorption fine structure (EXAFS) method. It revealed that the metal-oxygen bond length is shortened and the coordination number is thus decreased with increasing DMA content in the mixture. Interestingly, the decrease in the coordination number takes place evidently at a lower DMA content for the thulium(III) ion than the neodymium(III) ion, i.e., the geometry change is more favorable for the metal ion with a smaller ionic radius. 89Y NMR chemical shifts also demonstrate that the coordination number decreases with increasing DMA content in the mixture, and the profile of varying coordination number is similar to that for the thulium(III) ion. This indicates that the strong solvation steric effect operates with both thulium(III) and yttrium(III) ions in the DMF-DMA mixture. Variations of metal-oxygen bond length for other metal systems in the mixture indicate that, relative to the thulium(III) ion, the gadolinium(III) ion experiences a less strong solvation steric effect, and the neodymium(III) ion even less. Structural parameters have also been determined for a series of lanthanoid(III) ions in both DMF and DMA. The LnIII-O bond length in DMA is generally shorter than that in DMF, and the difference is smallest for the lanthanum(III) ion, and largest for the lutetium(III) ion. The difference is thus larger for a metal ion with a smaller ionic radius, implying that the solvation steric hindrance is enhanced with decreasing ionic radius.

DOI： 10.1039/a806967k

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Academic Press Inc.  

Complexation of the cadmium(II) ion with thiocyanate and iodide ions have been studied by precise titration calorimetry in micellar solutions of a nonionic surfactant Triton X-100 containing 0.4 mol dm-3 NaClO4 as a constant ionic medium at 298 K. With regard to the Cd(II)-SCN- system, the formation of [Cd(NCS)]+ and [Cd(NCS)(SCN)] in aqueous solution and [Cd(NCN)2(SCN)]- in micelles was established, though the complexation in micelles is not extensive. With the Cd(II)-I- system, the formation of [CdI]+, [CdI3]-, and [CdI4]2- was established in aqueous solution together with the formation of [CdI2], [CdI3]-, and [CdI4]2- in micelles. It is revealed that the complexation in micelles is accompanied by relatively large and negative enthalpies, which is ascribed to the enthalpies of transfer of [CdI3]- and [CdI4]2- from aqueous solution to micelles. This suggests that a hydrophobic complex with no capacity to form strong hydrogen bonds in water is favored in micelles.

DOI： 10.1006/jcis.1997.4937

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry  

Complexation of copper(II) and zinc(II) with thiocyanate ions has been studied by precise titration spectrophotometry and calorimetry in aqueous solution containing varying concentrations (0-100 mmol dm-3) of a non-ionic surfactant Triton X-100 at 25°C. Both spectrophotometric and calorimetric data were analysed by treating the surfactant as the third component, and the complexes formed in aqueous and micellar pseudo phases were distinguished. In the case of zinc(II), the formation of [Zn(NCS)]+ and [Zn(NCS)3]- in the aqueous phase and [Zn(NCS)3Y]- and [Zn(NCS)4Y]2- (Y = Triton X-100) in the micellar phase was established, and their formation constants, enthalpies and entropies obtained. On the other hand, with copper(II), the formation of [Cu(NCS)]+, [Cu(NCS)2] and [Cu(NCS)2Y] was established, and their formation constants and intrinsic electronic spectra were extracted. As the complexation behaviour in a micellar solution might be compared with that in a non-aqueous solution, the complexation for the CuII-NCS- system was also studied in N,N-dimethylformamide. The difference in the complexation of copper(II) and zinc(II) ions in the micellar solution is discussed from thermodynamic and structural viewpoints.

DOI： 10.1039/a607341g

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society for Analytical Chemistry  

The complexation of cobalt(II), nickel(II), copper(II), and zinc(II) with thiocyanate ions has been studied in micellar solutions of nonionic surfactant Triton X-100 by titration spectrophotometry and calorimetry. The complexation has been also studied by varying length of POE (polyoxyethylene) chain. With regard to Co(II), the [Co(NCS)4]2-, which hardly forms in aqueous phase, is extensively formed in micelles. With Zn(II), the [Zn(NCS)3]- and [Zn(NCS)4]2- are formed in micelles. With Ni(II), no complexation occurs in micelles. In the case of Cu(II), the formation of [Cu(NCS)2] is concluded in both micelles and aqueous phase. The complexation behavior of [Co(NCS)4]2- and [Cu(NCS)2] depends significantly on the length of POE chain, suggesting that these complexes exist both in the relatively hydrophilic POE site and hydrophobic core site.

DOI： 10.2116/analsci.13.supplement_115

Scopus

researchmap

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Kluwer Academic/Plenum Publishers  

Complexation of cobalt(II) and nickel(II) with thiocyanate ions has been studied by precise spectrophotometry in aqueous and micellar solutions of a nonionic surfactant Triton X-100 of varying concentrations (20-100 mmol-dm-3). With regard to cobalt(II), the formation of [Co(NCS)]+, [Co(NCS)2], and [Co(NCS)4]2- was established. The formation constant of [Co(NCS)4]2- is increased with increasing concentration cf the surfactant, suggesting that the [Co(NCS)4]2- complex is formed in micelles. In contrast, the formation constants of [Co(NCS)]+ and [Co(NCS)2] are remained practically unchanged. On the other hand, with nickel(II), the formation of sole [Ni(NCS)]+ and [Ni(NCS)2] was established in both aqueous and micellar solutions examined, their formation constants being also remained unchanged. Interestingly, no higher complex was confirmed in the nickel(II) system, unlike cobalt(II). The unusual affinity of the [Co(NCS)4]2- complex with micelles will be discussed from thermodynamic and structural points of view.

DOI： 10.1007/BF00973781

Scopus

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

researchmap

Responsible for pages：28, 234-235  

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：English  

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese   Publisher：ジャスコレポート社  

CiNii Article

CiNii Books

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：English  

researchmap

Language：Japanese  

J-GLOBAL

researchmap

Language：English   Publishing type：Book review, literature introduction, etc.   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

Titration Raman spectroscopy has been developed for studying the solvation structure of metal ions in solution. The method affords us the solvation number, and the value thus obtained in neat solvents is in good agreement with that determined by EXAFS. The method is then applied to solvent mixtures, and the individual solvation number for each solvent is extracted. In a solvent mixture of N,N-dimethylformamide (DMF) and N,N,N',N'-tetramethylurea (TMU), the metal ion prefers DMF to TMU, which is ascribed to the solvation steric effect. The same applies also for the solvent mixture of N,N-dimethylpropionamide (DMPA) and DMF. However, unlike TMU, DMPA changes its conformation from the planar cis to non-planar staggered upon solvation to the metal ion. The enthalpy for the conformational change of DMPA is positive in the bulk, while it is significantly negative in the coordination sphere of the manganese(II) ion. Here, we briefly describe the procedure of measurements and analyses for the titration Raman spectroscopy, and review the solvation structure of the alkaline earth, first transition metal(H) and lanthanide(III) ions in some solvent mixtures in view of solvation steric effect.

Web of Science

researchmap

Language：English  

researchmap

Language：English   Publisher：ACADEMIC PRESS INC  

Formation of copper(II) thiocyanato and cadminum(II) iodo complexes in micelles of poly(ethylene oxide) (PEO)-type nonionic surfactants with varying PEO chain lengths of 9.5 (Triton X-100), 30 (Triton X-305), and 40 (Triton X-405) has been studied by titration spectrophotometry and calorimetry at 298 K. In a given surfactant solution, all data obtained were analyzed by assuming formation of ternary complexes MXnYm(2-n)+ (M = Cu-II,Cd-II; X =SCN-, I-; Y = surfactant), and the complexes thus form in aqueous phase (m = 0) or in micelles (m = 1). In the (CuSCN-)-S-II system, spectrophotometric data obtained by varying concentrations of the surfactant can be explained well in terms of formation of Cu(NCS)(2)Y in micelles and Cu(NCS)(+) and Cu(NCS)(2) in an aqueous phase, and it turned out that formation constant of Cu(NCS)(2)Y increases with increasing PEO chain length. In the Cd-II-I- system, the formation of CdI3Y- and CdI4Y2- is concluded in micelles, and that of CdI+, CdI3-, and CdI42- in an aqueous phase. Interestingly, formation enthalpies of CdI3Y- and CdI4Y2- become significantly less negative with increasing PEO chain length. This suggests that transfer of the complexes from aqueous solution to a hydrophobic octylphenyl (OP) moiety in micelles is significantly more exothermic than that to a hydrophilic PEO one. Thermodynamic parameters of transfer of CdI3- and CdI42- from aqueous solution to the OP and PEO moieties of micelles have been evaluated, (C) 2000 Academic Press.

DOI： 10.1006/jcis.2000.6722

Web of Science

PubMed

CiNii Article

researchmap

Language：Japanese   Publisher：広信社  

CiNii Article

CiNii Books

researchmap

Language：English   Publisher：ROYAL SOC CHEMISTRY  

Bromo complexation of neodymium(III) and yttrium(nr) in solvent mixtures of N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) has been studied by precise titration calorimetry, Y-89 NMR and extended X-ray absorption fine structure (EXAFS). With regard to neodymium(III), calorimetric data in the mixture of DMA content x are explained satisfactorily in terms of formation of mononuclear NdBrn(3-n)+(n = 1, 2 at x = 0.5 and n = 1, 2, 3 at x = 0.6, 0.75, 0.85). With yttrium(III), calorimetric data are also explained well in terms of formation of mononuclear YBrn(3-n)+(n = 1, 2 at x = 0.25, 0.5, 0.6 and n = 1, 2, 3 at x = 0.65, 0.75, 0.85). Formation enthalpy and entropy values of the monobromo complex remain practically unchanged up to x approximate to 0.5, and then significantly increase with increasing x. It is thus suggested in both metal(III) systems that outer-sphere bromo complexes are formed in the DMF-rich mixture, while inner-sphere bromo complexes are formed in the DMA-rich mixture in equilibrium with the outer-sphere ones, and the formation of inner-sphere complexes becomes more favorable with increasing DMA content. The marked difference in the complexation in DMF and DMA may be ascribed to the solvation steric effect. The solvation steric effect is enhanced with increasing DMA content leading to an enhanced complexation and a simultaneous geometry transition from outer- to inner-sphere coordination of the bromide ion. Evidence of the geometry transition has been obtained by EXAFS for neodymium(III), and by Y-89 NMR for yttrium(III). Interestingly, although ionic radii of neodymium(III) and yttrium(III) ions are significantly different, no appreciable metal-ion dependence is found with the geometry transition from outer- to inner-sphere bromo complex. This indicates that the geometry transition of the metal(III) solvate ion from eight- to seven-coordination is not always the necessary condition for the transition from outer- to inner-sphere complexation.

DOI： 10.1039/a901225g

Web of Science

CiNii Article

researchmap

researchmap

Language：English   Publisher：ROYAL SOC CHEMISTRY  

Molar volumes of zinc(II) thiocyanato complexes have been evaluated by densitometric titration in N,N-dimethylformamide at 298.15 K. All the measurements were carried out in solution containing an inert supporting electrolyte 0.2 mol dm(-3) (C2H5)(4)NClO4 and the molar volumes of all the ionic species were assumed to be kept constant throughout titration. The volume changes, Delta V, thus determined for the reactions are as follows:
Zn2+ + SCN- = [Zn(NCS)](+); Delta V(0-1)degrees, = 15 cm(3) mol(-1) (1)
[Zn(NCS)](+) + 2SCN(-) = [Zn(NCS)(3)](-); Delta(1-3)degrees = 77 cm(3) mol(-1) (2)
[Zn(NCS)(3)](-) + SCN- = [Zn(NCS)(4)](2-); Delta V(3-4)degrees = -18 cm(3) mol(-1) (3)
These show that the volume changes parallel the corresponding reaction entropies. The Delta V(1-3)degrees of reaction (2) shows a relatively large value, as expected from the fact that the coordination geometry around the zinc(II) ion changes from octahedral six-coordination to tetrahedral four-coordination.

DOI： 10.1039/a608617i

Web of Science

CiNii Article

researchmap

Event date： 2021.10

Presentation type：Poster presentation  

researchmap

Event date： 2021.10

Presentation type：Poster presentation  

researchmap

Event date： 2021.10

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.9

researchmap

Event date： 2021.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.9

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.5

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.5

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.3

Presentation type：Oral presentation (general)  

researchmap

Event date： 2021.3

Presentation type：Oral presentation (general)  

researchmap

Event date： 2020.11

Language：Japanese  

researchmap

Event date： 2020.9

Language：Japanese  

researchmap

Event date： 2020.9

Language：Japanese  

researchmap

Event date： 2020.3

Presentation type：Oral presentation (general)  

researchmap

Event date： 2020.3

Presentation type：Oral presentation (general)  

researchmap

Event date： 2019.11

Presentation type：Oral presentation (general)  

researchmap

Event date： 2019.11

Presentation type：Poster presentation  

researchmap

Event date： 2019.11

Presentation type：Poster presentation  

researchmap

Event date： 2019.10 - 2019.11

Presentation type：Poster presentation  

researchmap

Event date： 2019.10 - 2019.11

Presentation type：Oral presentation (general)  

researchmap

Event date： 2019.10 - 2019.11

Presentation type：Poster presentation  

researchmap

Event date： 2019.9

Presentation type：Poster presentation  

researchmap

Event date： 2019.9

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Language：English   Presentation type：Oral presentation (keynote)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Language：English   Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Language：English   Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Language：English   Presentation type：Oral presentation (keynote)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Language：English   Presentation type：Oral presentation (keynote)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Poster presentation  

researchmap

Language：English   Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Oral presentation (general)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Public lecture, seminar, tutorial, course, or other speech  

researchmap

Presentation type：Oral presentation (invited, special)  

researchmap

Presentation type：Poster presentation  

researchmap

Presentation type：Poster presentation  

researchmap