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Koyakkat M, Ishida T, Fujita K, Shirota H. Low-Frequency Spectra of Hydrated Ionic Liquids with Kosmotropic and Chaotropic Anions. J Phys Chem B 2024; 128:4171-4182. [PMID: 38640467 DOI: 10.1021/acs.jpcb.4c01255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/21/2024]
Abstract
In this study, we investigated the water concentration dependence of the intermolecular vibrations of two hydrated ionic liquids (ILs), cholinium dihydrogen phosphate ([ch][dhp]) and cholinium bromide ([ch]Br), using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES). The anions of the former and latter hydrated ILs are kosmotropic and chaotropic, respectively. We found that the spectral peak of ∼50 cm-1 shifted to the low-frequency side in hydrated [ch][dhp], indicating the weakening of its intermolecular interactions. In contrast, no change in the peak frequency of the low-frequency band at ∼50 cm-1 was observed with increasing water concentration in hydrated [ch]Br. The vibrational density of states (VDOS) spectra generated from molecular dynamics (MD) simulations were in qualitative agreement with the experimental results. Decomposition analysis of the VDOS spectra for each component revealed that the red shift of the low-frequency band in the hydrated [ch][dhp] upon water addition was essentially due to the contributions of anions and water rather than that of the cholinium cation. We also found from the low-frequency spectra of the two hydrated ILs that they differed in the concentration dependence of the 180 cm-1 band, which is assigned as a hindered translational motion of water molecules combined to form O···O stretching motions. From the relationship between the peak frequency of the low-frequency band and the bulk parameter, which is the square root of the surface tension divided by the density, we found that the peak frequency in the hydrated IL with kosmotropic [dhp]- depends on the bulk parameter, similar to the case for an aqueous solution of the typical deep eutectic solvent reline. However, the peak frequency of the hydrated IL with chaotropic Br- is constant with the bulk parameter.
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Affiliation(s)
- Maharoof Koyakkat
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Tateki Ishida
- Institute for Molecular Science and Research Center for Computational Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan
| | - Kyoko Fujita
- Department of Pathophysiology, Tokyo University of Pharmacy and Life Sciences, 1432-1 Horinouchi, Hachioji, Tokyo 192-0392, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Ando M, Koyakkat M, Ueda T, Minato T, Shirota H. Wettability and Surface Tension of Imidazolium, Ammonium, and Phosphonium Bis(fluorosulfonyl)amide Ionic Liquids: Comparison between Pentyl, Ethoxyethyl, and Ethylthioethyl Groups. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:12090-12098. [PMID: 37578197 DOI: 10.1021/acs.langmuir.3c01375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
This study particularly compares the surface tensions and contact angles for molten bis(fluorosulfonyl)amide salts of imidazolium, ammonium, and phosphonium cations with the pentyl, ethoxyethyl, or ethylthioethyl group. The examined substrate plates for contact angle measurements include silicate glass, platinum, copper, graphene, and polytetrafluoroethylene (PTFE). In addition, quantum chemistry calculations were performed to obtain the optimized structures of the cations and anions of the ionic liquids (ILs) that were studied here along with some typical anions and their dipole moments, mean polarizabilities, and charge distributions. All ILs showed the same order of contact angles with respect to the substrates: PTFE > graphene ≈ copper ≈ platinum > silicate glass. By comparing the three functional groups, i.e., pentyl, ethoxyethyl, and ethylthioethyl, the ILs with the ethylthioethyl group featured a higher work of adhesion than the respective ILs with the pentyl or ethoxyethyl group. The values of the surface tensions of the ILs followed the same trend for the three functional groups. Based on the Fowkes theory, it was found that the larger surface tensions of the ILs with the ethylthioethyl group compared with pentyl and ethoxyethyl groups were because of the increase in both dispersive and nondispersive components. The quantum chemistry calculations of the ions showed a larger dipole moment and mean polarizability for the cations with the ethylthioethyl group as compared with the pentyl and ethoxyethyl groups. This is consistent with the analysis results of the surface tensions based on the Fowkes theory. By comparing other anions, the dispersive component of the surface tension of the ILs with bis(fluorosulfonyl)amide was large, which is attributed to the small dipole moment of the anion.
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Affiliation(s)
- Masatoshi Ando
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Maharoof Koyakkat
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Tadashi Ueda
- Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
| | - Taketoshi Minato
- Institute for Molecular Science, National Institutes of Natural Sciences, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Ando M, Tashiro A, Kawano M, Peng Y, Takamuku T, Shirota H. Exploring the Microscopic Aspects of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Formamide, N-Methylformamide, and N, N-Dimethylformamide by Multiple Spectroscopic Techniques and Computations. J Phys Chem B 2023; 127:3870-3887. [PMID: 37093658 DOI: 10.1021/acs.jpcb.2c09102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
The microscopic aspects of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) mixtures with formamide (FA), N-methylformamide (NMF), and N,N-dimethylformamide (DMF) were investigated using spectroscopic techniques of femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES), FT-IR, and NMR. Molecular dynamics simulations and quantum chemistry calculations were also performed. According to fs-RIKES, the first moment of the low-frequency spectrum bands mainly originating from the intermolecular vibrations in the [MOIm][BF4]/FA and [MOIm][BF4]/DMF systems changed gradually with the molecular liquid mole fraction XML but that in the [MOIm][BF4]/NMF system was constant up to XNMF = 0.7 and then gradually increased in the range of XNMF ≥ 0.7. Excluding the contribution of the 2D hydrogen-bonding network due to the presence of FA in the low-frequency spectrum band, the XML dependence of the normalized first moment of the low-frequency band in the [MOIm][BF4]/FA and [MOIm][BF4]/NMF systems revealed that the normalized first moment did not remarkably change in the range of XML < 0.7 but drastically increased in XML ≥ 0.7. FT-IR results indicated that the amide C═O band shifted to the low-frequency side with increasing XML for the three mixtures due to the hydrogen bonds. The imidazolium ring C-H band also showed a similar tendency to the amide C═O band. 19F NMR probed the microenvironment of [BF4]- in the mixtures. The [MOIm][BF4]/NMF and [MOIm][BF4]/DMF systems showed an up-field shift of the F atoms of the anion with increasing XML, and the [MOIm][BF4]/FA system exhibited a down-field shift. Steep changes in the chemical shifts were confirmed in the region of XML > 0.8. On the basis of the quantum chemistry calculations, the observed chemical shifts with increasing XML were mainly attributed to the many-body interactions of ions and amides for the [MOIm][BF4]/FA and [MOIm][BF4]/DMF systems. Meanwhile, the long distance between the cation and the anion was due to the high dielectric medium for the [MOIm][BF4]/NMF system, which led to an up-field shift.
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Affiliation(s)
- Masatoshi Ando
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Atsuya Tashiro
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Masahiro Kawano
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Yue Peng
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Toshiyuki Takamuku
- Faculty of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Hideaki Shirota
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Shirota H, Rajbangshi J, Koyakkat M, Baksi A, Cao M, Biswas R. Low-frequency spectra of reline and its mixtures with water: A comparative study based on femtosecond Raman-induced Kerr effect spectroscopy and molecular dynamics simulations. J Photochem Photobiol A Chem 2023. [DOI: 10.1016/j.jphotochem.2022.114504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Ando M, Ohta K, Ishida T, Koido R, Shirota H. Physical Properties and Low-Frequency Polarizability Anisotropy and Dipole Responses of Phosphonium Bis(fluorosulfonyl)amide Ionic Liquids with Pentyl, Ethoxyethyl, or 2-(Ethylthio)ethyl Group. J Phys Chem B 2023; 127:542-556. [PMID: 36602430 DOI: 10.1021/acs.jpcb.2c07466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This study compared the physical properties, e.g., glass transition temperature, melting point, viscosity, density, surface tension, and electrical conductivity, and the low-frequency spectra under 200 cm-1 of three synthesized ionic liquids (ILs), triethylpentylphosphonium bis(fluorosulfonyl)amide ([P2225][NF2]), ethoxyethyltriethylphosphonium bis(fluorosulfonyl)amide ([P222(2O2)][NF2]), and triethyl[2-(ethylthio)ethyl]phosphonium bis(fluorosulfonyl)amide ([P222(2S2)][NF2]), at various temperatures using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) and terahertz time-domain spectroscopy (THz-TDS). The [P222(2S2)][NF2] had the highest viscosity and glass transition temperature, whereas the [P222(2O2)][NF2] had the lowest. Among the three ILs, the [P222(2S2)][NF2] had the highest density and surface tension, and the [P222(2O2)][NF2] had the highest electrical conductivity. The RIKES and THz-TDS spectral line shapes for the three ILs varied significantly. For the [P2225][NF2], molecular dynamics simulations successfully reproduced the line shapes of the experimental spectra and indicated that the RIKES spectrum was mainly due to the cation and cross-term and their rotational motions, whereas the THz-TDS spectrum was mainly due to the anion and its translational motion. This shows that it is desirable to utilize both fs-RIKES and THz-TDS methods to reveal molecular motions at the low-frequency domain. The [P222(2S2)][NF2] had higher frequency peaks and broader bands in the low-frequency spectra via fs-RIKES and THz-TDS than those for the [P2225][NF2] and [P222(2O2)][NF2].
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Affiliation(s)
- Masatoshi Ando
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Kaoru Ohta
- Molecular Photoscience Research Center, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
| | - Tateki Ishida
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science and Research Center for Computational Science, 38 Nishigonaka, Myodaiji, Okazaki 444-8585, Japan
| | - Ryohei Koido
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Shimizu M, Shirota H. Intermolecular Dynamics of Positively and Negatively Charged Aromatics and Their Isoelectronic Neutral Analogs in Aqueous Solutions. J Phys Chem B 2022; 126:4309-4323. [PMID: 35658126 DOI: 10.1021/acs.jpcb.2c01517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study, we investigated the temperature dependence of intermolecular vibrations and orientational dynamics in the aqueous solutions of imidazole hydrochloride, imidazole, sodium triazolide, and triazole using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES) and steady-state Raman spectroscopy. The difference low-frequency Raman spectra under 250 cm-1 of the aqueous solutions relative to the neat water showed that the spectral shoulder in the high-frequency region at 60-100 cm-1, assigned to the libration of an aromatic ring, was higher in frequency for the imidazolium cation but lower for the triazolide anion than those of the respective neutral aromatics. The results of the ab initio quantum chemistry calculations of the clusters of the aromatics and water molecule(s) were consistent with the experimental spectra of the aqueous solutions. Further, the results of the temperature-dependent experiments showed that the signal intensity in the low-frequency region below 50 cm-1 increased for all solutions with an increase in temperature. In contrast, the spectral density in the high-frequency region above 80 cm-1 exhibited almost no shift for the 1.0 M solutions, while a significant red shift was observed for the 5.0 M solutions. In addition, the temperature-dependent densities, viscosities, and surface tensions were characterized for the aqueous aromatic solutions from 293 to 353 K.
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Affiliation(s)
- Masako Shimizu
- Department of Chemistry, Chiba University 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Shirota H, Yanase K, Ogura T, Sato T. Intermolecular Dynamics and Structure in Aqueous Lidocaine Hydrochloride Solutions. J Phys Chem B 2022; 126:1787-1798. [PMID: 35170970 DOI: 10.1021/acs.jpcb.1c10504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We investigated the intermolecular dynamics and static structure in the aqueous solutions of lidocaine hydrochloride (LDHCl) in the concentration range of [LDHCl] = 0-2.00 M using femtosecond Raman-induced Kerr effect spectroscopy (fs-RIKES), small- and wide-angle X-ray scattering (SWAXS), and dynamic light scattering (DLS). For the fs-RIKES experiments, the concentration dependence of the difference low-frequency spectra of the aqueous LDHCl solutions relative to the neat water, which was mainly due to the intermolecular vibrations, was characterized using an exponential function with a characteristic concentration of ∼1 M. For the SWAXS experiments, we observed a manifestation of an excess scattering component centered within a range of 8-10 nm-1 in the aqueous LDHCl solutions. The results of Fourier inversion and further deconvolution analyses unambiguously demonstrated that lidocaines assemble into a nanometer-sized micelle-like structure with the innermost core (∼0.3 nm) and outer shell (∼0.5 nm), respectively. The DLS experiments also found nanometer-sized aggregates and further indicated evidence of the clusters of the aggregates. The results of viscosities, densities, and surface tensions of the solutions and the quantum chemistry calculations supported the unique features of the microscopic intermolecular interaction and the micelle-like aggregation.
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Affiliation(s)
- Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Keiichi Yanase
- Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Taiki Ogura
- Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
| | - Takaaki Sato
- Department of Chemistry and Materials, Faculty of Textile Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano 386-8567, Japan
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Ando M, Shirota H. Low-Frequency Spectra of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Poly(ethylene glycol) by Femtosecond Raman-Induced Kerr Effect Spectroscopy. J Phys Chem B 2021; 125:12006-12019. [PMID: 34694116 DOI: 10.1021/acs.jpcb.1c07079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
This is the first report on low-frequency spectra of ionic liquid (IL)/polymer mixtures using femtosecond Raman-induced Kerr effect spectroscopy. We studied mixtures of 1-methyl-3-octylimidazolium tetrafluoroborate ([MOIm][BF4]) and poly(ethylene glycol) (PEG) with Mn = 400 (PEG400) at various concentrations. To elucidate the unique features of the IL/polymer mixture system, mixtures of PEG400 with a molecular liquid, 1-octhylimidazole (OIm), which is a neutral analog of the cation, were also studied. In addition, mixtures of [MOIm][BF4] with ethylene glycol (EG) and poly(ethylene glycol) with Mn = 4000 (PEG4000) were also investigated. The first moments of broad low-frequency spectra, mainly due to intermolecular vibrations for the [MOIm][BF4]/PEG400 and OIm/PEG400, increased slightly with increasing concentration of PEG400, indicating that microscopic intermolecular interactions, in general, are slightly enhanced. We also compared the [MOIm][BF4] mixtures with EG, PEG400, and PEG4000 at concentrations of 5 and 10 wt % PEG or EG. The low-frequency spectra of samples with the same concentrations were quite similar, but a comparison of the normalized spectra showed that the spectral intensity in the low-frequency region below ∼50 cm-1 of the [MOIm][BF4] mixtures with PEG400 and PEG4000 is somewhat lower than that of the [MOIm][BF4] mixtures with EG. Although the effect of the polymer is small compared to other polymer solution systems, this feature is attributed to a suppression of translational motion in the mixtures of [MOIm][BF4] with PEG compared to the mixtures of [MOIm][BF4] with EG due to the greater mass of PEG than EG. Density, surface tension, viscosity, and electrical conductivity were also estimated. From Walden plots, it was found that the [MOIm][BF4]/PEG4000 system showed more ideal electrical conductive behavior than the [MOIm][BF4]/PEG400 and [MOIm][BF4]/EG systems.
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Affiliation(s)
- Masatoshi Ando
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Hideaki Shirota
- Department of Chemistry, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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Ando M, Kawano M, Tashiro A, Takamuku T, Shirota H. Low-Frequency Spectra of 1-Methyl-3-octylimidazolium Tetrafluoroborate Mixtures with Methanol, Acetonitrile, and Dimethyl Sulfoxide: A Combined Study of Femtosecond Raman-Induced Kerr Effect Spectroscopy and Molecular Dynamics Simulations. J Phys Chem B 2020; 124:7857-7871. [DOI: 10.1021/acs.jpcb.0c04870] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Masatoshi Ando
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
| | - Masahiro Kawano
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Atsuya Tashiro
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Toshiyuki Takamuku
- Faculty of Science and Engineering, Saga University, Honjo-machi, Saga 840-8502, Japan
| | - Hideaki Shirota
- Department of Chemistry, Graduate School of Science, Chiba University, 1-33 Yayoi, Inage-ku, Chiba 263-8522, Japan
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