1
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Katsyuba SA, Zvereva EE. What quantum chemical simulations tell us about the infrared spectra, structure and interionic interactions of a bulk ionic liquid. Phys Chem Chem Phys 2022; 24:7349-7355. [PMID: 35266472 DOI: 10.1039/d1cp05745f] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The recently developed efficient protocol to explicit quantum mechanical modeling of the structure and IR spectra of liquids and solutions [Katsyuba et al., J. Phys. Chem. B, 2020, 124, 6664-6670] is applied to ionic liquid 1-ethyl-3-methyl-imidazolium tetrafluoroborate [Emim][BF4], and its C2-deuterated analog [Emim-d][BF4]. It is shown that the solvation strongly modifies the frequencies and IR intensities of both cationic and anionic components of the ionic liquids. The main features of the bulk spectra are reproduced by the simulations for cluster ([Emim][BF4])8, representing an ion pair solvated by the first solvation shell. The geometry of the cluster closely resembles the solid-state structure of the actual ionic liquid and is characterized by short contacts of all CH moieties of the imidazolium ring with [BF4]- anions. Both structural and spectroscopic analyses allow the contacts to be interpreted as hydrogen bonds of approximately equal strength. The enthalpies of these liquid-state H-bonds, estimated with the use of empirical correlations, amount to 1.2-1.5 kcal mol-1, while the analogous estimates obtained for the gas-phase charged species [Emim][BF4]2- and [Emim]2[BF4]+ increase to 3.6-3.9 kcal mol-1.
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Affiliation(s)
- Sergey A Katsyuba
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Centre of RAS, Arbuzov st. 8, 420088, Kazan, Russia.
| | - Elena E Zvereva
- Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Centre of RAS, Arbuzov st. 8, 420088, Kazan, Russia. .,IFP Energies Nouvelles, 1 et 4 avenue de Bois-Préau, 92852 Rueil-Malmaison Cedex, France
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2
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Tran L, Rush K, Marzette J, Edmonds-Andrews G, Bennett T, Abdulahad A, Riley KE, Dutta S. Striking temperature-dependent molecular reorganization at the C-2 position of [EMIM][BF4]. Chem Phys Lett 2021. [DOI: 10.1016/j.cplett.2021.138956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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3
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Roy HA, Rodgers MT. 1-Alkyl-3-methylimidazolium cation binding preferences in hexafluorophosphate ionic liquid clusters determined using competitive TCID measurements and theoretical calculations. Phys Chem Chem Phys 2021; 23:18145-18162. [PMID: 34612278 DOI: 10.1039/d1cp02928b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids (ILs) exhibit unique properties that have led to their development and widespread use for a variety of applications. Development efforts have generally focused on achieving desired macroscopic properties via tuning of the IL through variation of the cations and anions. Both the macroscopic and microscopic properties of an IL influence its tunability and thus feasibility of use for selected applications. Works geared toward a microscopic understanding of the nature and strength of the intrinsic cation-anion interactions of ILs have been limited to date. Specifically, the intrinsic strength of the cation-anion interactions in ILs is largely unknown. In previous work, we employed threshold collision-induced dissociation (TCID) approaches supported and enhanced by electronic structure calculations to determine the bond dissociation energies (BDEs) and characterize the nature of the cation-anion interactions in a series of four 2 : 1 clusters of 1-alkyl-3-methylimidazolium cations with the hexafluorophosphate anion, [2Cnmim:PF6]+. To examine the effects of the 1-alkyl chain on the structure and energetics of binding, the cation was varied over the series: 1-ethyl-3-methylimidazolium, [C2mim]+, 1-butyl-3-methylimidazolium, [C4mim]+, 1-hexyl-3-methylimidazolium, [C6mim]+, and 1-octyl-3-methylimidazolium, [C8mim]+. The variation in the strength of binding among these [2Cnmim:PF6]+ clusters was found to be similar in magnitude to the average experimental uncertainty in the measurements. To definitively establish an absolute order of binding among these [2Cnmim:PF6]+ clusters, we extend this work again using TCID and electronic structure theory approaches to include competitive binding studies of three mixed 2 : 1 clusters of 1-alkyl-3-methylimidazolium cations and the hexafluorophosphate anion, [Cn-2mim:PF6:Cnmim]+ for n = 4, 6, and 8. The absolute BDEs of these mixed [Cn-2mim:PF6:Cnmim]+ clusters as well as the absolute difference in the strength of the intrinsic binding interactions as a function of the cation are determined with significantly improved precision. By combining the thermochemical results of the previous independent and present competitive measurements, the BDEs of the [2Cnmim:PF6]+ clusters are both more accurately and more precisely determined. Comparisons are made to results for the analogous [2Cnmim:BF4]+ and [Cn-2mim:BF4:Cnmim]+ clusters previously examined to elucidate the effects of the [PF6]- and [BF4]- anions on the binding.
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Affiliation(s)
- H A Roy
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
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4
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Roy HA, Rodgers MT. Nature and strength of intrinsic cation-anion interactions of 1-alkyl-3-methylimidazolium hexafluorophosphate clusters. Phys Chem Chem Phys 2021; 23:13405-13418. [PMID: 34105537 DOI: 10.1039/d1cp01130h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Imidazolium-based cations and the hexafluorophosphate anion are among the most commonly used ionic liquids (ILs). Yet, the nature and strength of the intrinsic cation-anion interactions, and how they influence the macroscopic properties of these ILs are still not well understood. Threshold collision-induced dissociation is utilized to determine the bond dissociation energies (BDEs) of the 2 : 1 clusters of 1-alkyl-3-methylimidazolium cations and the hexafluorophosphate anion, [2Cnmim:PF6]+. The cation, [Cnmim]+, is varied across the series, 1-ethyl-3-methylimidazolium [C2mim]+, 1-butyl-3-methylimidazolium [C4mim]+, 1-hexyl-3-methylimidazolium [C6mim]+, 1-octyl-3-methylimidazolium [C8mim]+, to examine the structural and energetic effects of the size of the 1-alkyl substituent of the cation on the binding to [PF6]-. Complementary electronic structure methods are employed for the [Cnmim]+ cations, (Cnmim:PF6) ion pairs, and [2Cnmim:PF6]+ clusters to elucidate details of the cation-anion interactions and their impact on structure and energetics. Multiple levels of theory are benchmarked with the measured BDEs including B3LYP, B3LYP-GD3BJ, and M06-2X each with the 6-311+G(d,p) basis set for geometry optimizations and frequency analyses and the 6-311+G(2d,2p) basis set for energetic determinations. The modest structural variation among the [Cnmim]+ cations produces only minor structural changes and variation in the measured BDEs of the [2Cnmim:PF6]+ clusters. Present results are compared to those previously reported for the analogous 1-alkyl-3-methylimidazolium tetrafluoroborate IL clusters to compare the effects of these anions on the nature and strength of the intrinsic binding interactions.
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Affiliation(s)
- H A Roy
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
| | - M T Rodgers
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.
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5
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Zeng HJ, Khuu T, Chambreau SD, Boatz JA, Vaghjiani GL, Johnson MA. Ionic Liquid Clusters Generated from Electrospray Thrusters: Cold Ion Spectroscopic Signatures of Size-Dependent Acid-Base Interactions. J Phys Chem A 2020; 124:10507-10516. [PMID: 33284621 DOI: 10.1021/acs.jpca.0c07595] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
We determine the intramolecular distortions at play in the 2-hydroxyethylhydrazinium nitrate (HEHN) ionic liquid (IL) propellant, which presents the interesting case that the HEH+ cation has multiple sites (i.e., hydroxy, primary amine, and secondary ammonium groups) available for H-bonding with the nitrate anion. These interactions are quantified by analyzing the vibrational band patterns displayed by cold cationic clusters, (HEH+)n(NO3-)n-1, n = 2-6, which are obtained using IR photodissociation of the cryogenically cooled, mass-selected ions. The strong interaction involving partial proton transfer of the acidic N-H proton in HEH+ cation to the nitrate anion is strongly enhanced in the ternary n = 2 cluster but is suppressed with increasing cluster size. The cluster spectra recover the bands displayed by the bulk liquid by n = 5, thus establishing the minimum domain required to capture this aspect of macroscopic behavior.
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Affiliation(s)
- Helen J Zeng
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Thien Khuu
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Steven D Chambreau
- Jacobs Technology, Inc., Air Force Research Laboratory, AFRL/RQRP, Edwards Air Force Base, California 93524, United States
| | - Jerry A Boatz
- Propellants Branch, Rocket Propulsion Division, Aerospace Systems Directorate, Air Force Research Laboratory, AFRL/RQRP, Edwards Air Force Base, California 93524, United States
| | - Ghanshyam L Vaghjiani
- In-Space Propulsion Branch, Rocket Propulsion Division, Aerospace Systems Directorate, Air Force Research Laboratory, AFRL/RQRP, Edwards Air Force Base, California 93524, United States
| | - Mark A Johnson
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
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6
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Roy HA, Hamlow LA, Rodgers MT. Gas-Phase Binding Energies and Dissociation Dynamics of 1-Alkyl-3-Methylimidazolium Tetrafluoroborate Ionic Liquid Clusters. J Phys Chem A 2020; 124:10181-10198. [PMID: 33231466 DOI: 10.1021/acs.jpca.0c06297] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ionic liquids (ILs) have become increasingly popular due to their useful and unique properties, yet there are still many unanswered questions regarding their fundamental interactions. In particular, details regarding the nature and strength of the intrinsic cation-anion interactions and how they influence the macroscopic properties of ILs are still largely unknown. Elucidating the molecular-level details of these interactions is essential to the development of better models for describing ILs and enabling the purposeful design of ILs with properties tailored for specific applications. Current uses of ILs are widespread and diverse and include applications for energy storage, electrochemistry, designer/green solvents, separations, and space propulsion. To advance the understanding of the energetics, conformations, and dynamics of gas-phase IL clustering relevant to space propulsion, threshold collision-induced dissociation approaches are used to measure the bond dissociation energies (BDEs) of the 2:1 clusters of 1-alkyl-3-methylimidazolium cations and tetrafluoroborate, [2Cnmim:BF4]+. The cation, [Cnmim]+, is varied across the series, 1-ethyl-3-methylimidazolium [C2mim]+, 1-butyl-3-methylimidazolium [C4mim]+, 1-hexyl-3-methylimidazolium [C6mim]+, and 1-octyl-3-methylimidazolium [C8mim]+, to examine the structural and energetic effects of the size of the 1-alkyl substituent on binding. Complementary electronic structure calculations are performed to determine the structures and energetics of the [Cnmim]+ and [BF4]- ions and their binding preferences in the (Cnmim:BF4) ion pairs and [2Cnmim:BF4]+ clusters. Several levels of theory, B3LYP, B3LYP-GD3BJ, and M06-2X, using the 6-311+G(d,p) basis set for geometry optimizations and frequency analyses and the 6-311+G(2d,2p) basis set for energetics, are benchmarked to examine their abilities to properly describe the nature of the binding interactions and to reproduce the measured BDEs. The modest structural variation among these [Cnmim]+ cations produces only minor structural changes and variation in the measured BDEs of the [2Cnmim:BF4]+ clusters. Present findings indicate that the dominant cation-anion interactions involve the 3-methylimidazolium moieties and that these clusters are sufficiently small that differences in packing effects associated with the variable length of the 1-alkyl substituents are not yet significant.
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Affiliation(s)
- H A Roy
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - L A Hamlow
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
| | - M T Rodgers
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
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7
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Booth RS, Annesley CJ. Photoinduced Intermolecular Electron Transfer in Gas Phase Ion Pairs of the 1-Ethyl-3-methylimidazolium Cation and the Bis(trifluoromethylsulfonyl)imide Anion. J Phys Chem A 2020; 124:9683-9691. [PMID: 33185452 DOI: 10.1021/acs.jpca.0c06018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this study, the UV photodissociation of gas phase ion pairs of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim]+[tf2n]-, is shown to proceed primarily through radical intermediates. [emim]+[tf2n]- ion pairs have been shown previously to undergo two-photon-dependent dissociation, but the mechanisms of this have not been probed in detail. By employing a two-laser pump probe spectroscopy and time-dependent density functional theory (TD-DFT) calculations, we have illustrated that one of the major UV photodissociation pathways in [emim]+[tf2n]- ion pairs is an intermolecular electron transfer wherein the anion transfers an electron to the cation resulting in two neutral open-shelled products. These products were observable for at least 1.6 μs post photodissociation, the experimental limit, via detection of the [emim]+ cation. This data demonstrates that the likely photoproducts of [emim]+[tf2n]- UV photodissociation are two neutral species that separate spatially, demonstrated through lack of observed relaxation pathways such as electron recombination. TD-DFT and frontier molecular orbital analysis calculations at the MN15/6-311++G(d,p) level are employed to aid in identifying excited state characteristics and support the interpretations of the experimental data. The energetic onset of the intermolecular electron transfer is consistent with previously observed [emim]+[tf2n]- absorption spectra in the bulk and gas phases. The similarities between bulk and gas phase UV spectra imply that this electron-transfer pathway may be a major photodissociation channel in both phases.
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Affiliation(s)
- Ryan S Booth
- Institute for Scientific Research, Boston College, Chestnut Hill, Boston, Massachusetts 02467, United States
| | - Christopher J Annesley
- Space Vehicles Directorate, Air Force Research Laboratory, Kirtland AFB, Albuquerque, New Mexico 87117, United States
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8
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Abstract
The extent to which cations and anions in ionic liquids (ILs) and ionic liquid solutions are dissociated is of both fundamental scientific interest and practical importance because ion dissociation has been shown to impact viscosity, density, surface tension, volatility, solubility, chemical reactivity, and many other important chemical and physical properties. When mixed with solvents, ionic liquids provide the unique opportunity to investigate ion dissociation from infinite dilution in the solvent to a completely solvent-free state, even at ambient conditions. The most common way to estimate ion dissociation in ILs and IL solutions is by comparing the molar conductivity determined from ionic conductivity measurements such as electrochemical impedance spectroscopy (EIS) (which measure the movement of only the charged, i.e., dissociated, ions) with the molar conductivity calculated from ion diffusivities measured by pulse field gradient nuclear magnetic resonance spectroscopy (PFG-NMR, which gives movement of all of the ions). Because the NMR measurements are time-consuming, the number of ILs and IL solutions investigated by this method is relatively limited. We have shown that use of the Stokes-Einstein equation with estimates of the effective ion Stokes radii allows ion dissociation to be calculated from easily measured density, viscosity, and ionic conductivity data (ρ, η, λ), which is readily available in the literature for a much larger number of pure ILs and IL solutions. Therefore, in this review, we present values of ion dissociation for ILs and IL solutions (aqueous and nonaqueous) determined by both the traditional molar conductivity/PFG-NMR method and the ρ, η, λ method. We explore the effect of cation and anion alkyl chain length, structure, and interaction motifs of the cation and anion, temperature, and the strength of the solvent in IL solutions.
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Affiliation(s)
- Oscar Nordness
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
| | - Joan F Brennecke
- McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United States
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9
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Zhang J, Baxter ET, Nguyen MT, Prabhakaran V, Rousseau R, Johnson GE, Glezakou VA. Structure and Stability of the Ionic Liquid Clusters [EMIM] n[BF 4] n+1- ( n = 1-9): Implications for Electrochemical Separations. J Phys Chem Lett 2020; 11:6844-6851. [PMID: 32697088 DOI: 10.1021/acs.jpclett.0c01671] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Precise functionalization of electrodes with size-selected ionic liquid (IL) clusters may improve the application of ILs in electrochemical separations. Herein we report our combined experimental and theoretical investigation of the IL clusters 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM]n[BF4]n+1- (n = 1-9) and demonstrate their selectivity and efficiency toward targeted adsorption of ions from solution. The structures and energies of the IL clusters, predicted with global optimization, agree with and help interpret the ion abundances and stabilities measured by high-mass-resolution electrospray ionization mass spectrometry and collision-induced dissociation experiments. The [EMIM][BF4]2- cluster, which was identified as the most stable IL cluster, was selectively soft-landed onto a working electrode. Electrochemical impedance spectroscopy revealed a lower charge transfer resistance on the soft-landed electrode containing [EMIM][BF4]2- compared with an electrode prepared by drop-casting of an IL solution containing the full range of IL clusters. Our findings indicate that specific IL clusters may be used to increase the efficiency of electrochemical separations by lowering the overpotentials involved.
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Affiliation(s)
- Jun Zhang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Eric T Baxter
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Manh-Thuong Nguyen
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Venkateshkumar Prabhakaran
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Roger Rousseau
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
| | - Grant E Johnson
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99354, United States
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10
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Zeng HJ, Menges FS, Niemann T, Strate A, Ludwig R, Johnson MA. Chain Length Dependence of Hydrogen Bond Linkages between Cationic Constituents in Hydroxy-Functionalized Ionic Liquids: Tracking Bulk Behavior to the Molecular Level with Cold Cluster Ion Spectroscopy. J Phys Chem Lett 2020; 11:683-688. [PMID: 31899639 DOI: 10.1021/acs.jpclett.9b03359] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Hydroxy functionalization of cations in ionic liquids (ILs) can lead to formation of contacts between their OH groups [so-called (c-c) interactions]. One class of these linkages involves cooperatively enhanced hydrogen bonds to anionic partners that are sufficiently strong to overcome the repulsion between two positively charged centers. Herein, we clarify how the propensity for the formation of (c-c) contacts depends on the alkyl chain length between two cationic rings and their OH groups by analyzing the temperature-dependent IR spectra of bulk ILs as well as the vibrational predissociation spectra of ∼35 K complexes comprised of two cations and one anion. This study compares the behavior of two cationic derivatives with ethyl and propyl chains complexed with two different anions: bis(trifluoromethylsulfonyl)imide and tetrafluoroborate. Only the bulk ILs with the longer chain propyl derivative [HPMPip+ = 1-(3-hydroxypropyl)-1-methylpiperidinium] display (c-c) interactions. Molecular-level aspects of this docking arrangement are revealed by analyzing the OH stretching fundamentals displayed by the ternary complexes.
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Affiliation(s)
- Helen J Zeng
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Fabian S Menges
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Thomas Niemann
- Department of Chemistry , University of Rostock , 18059 Rostock , Germany
- Department Life, Light & Matter , University of Rostock , Albert-Einstein-Strasse 25 , 18059 Rostock , Germany
| | - Anne Strate
- Department of Chemistry , University of Rostock , 18059 Rostock , Germany
- Department Life, Light & Matter , University of Rostock , Albert-Einstein-Strasse 25 , 18059 Rostock , Germany
| | - Ralf Ludwig
- Department of Chemistry , University of Rostock , 18059 Rostock , Germany
- Department Life, Light & Matter , University of Rostock , Albert-Einstein-Strasse 25 , 18059 Rostock , Germany
- Leibniz-Institut für Katalyse e.V. , Albert-Einstein-Strasse 29a , 18059 Rostock , Germany
| | - Mark A Johnson
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
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11
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Zeng HJ, Menges FS, Johnson MA. Comment on “C–D Vibration at C2 Position of Imidazolium Cation as a Probe of the Ionic Liquid Microenvironment”. J Phys Chem A 2019; 124:755-756. [DOI: 10.1021/acs.jpca.9b10728] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Helen J. Zeng
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Fabian S. Menges
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Mark A. Johnson
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
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12
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Tsybizova A, Fritsche L, Gorbachev V, Miloglyadova L, Chen P. Cryogenic ion vibrational predissociation (CIVP) spectroscopy of a gas-phase molecular torsion balance to probe London dispersion forces in large molecules. J Chem Phys 2019; 151:234304. [DOI: 10.1063/1.5124227] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Affiliation(s)
| | - Lukas Fritsche
- Laboratorium für Organische Chemie, ETH Zürich, Zürich, Switzerland
| | | | | | - Peter Chen
- Laboratorium für Organische Chemie, ETH Zürich, Zürich, Switzerland
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13
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Zeng HJ, Johnson MA, Ramdihal JD, Sumner RA, Rodriguez C, Lall-Ramnarine SI, Wishart JF. Spectroscopic Assessment of Intra- and Intermolecular Hydrogen Bonding in Ether-Functionalized Imidazolium Ionic Liquids. J Phys Chem A 2019; 123:8370-8376. [DOI: 10.1021/acs.jpca.9b04345] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Helen J. Zeng
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Mark A. Johnson
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Jasodra D. Ramdihal
- Chemistry Department, Queensborough Community College of the City University of New York, Bayside, New York 11364, United States
| | - Rawlric A. Sumner
- Chemistry Department, Queensborough Community College of the City University of New York, Bayside, New York 11364, United States
| | - Chanele Rodriguez
- Chemistry Department, Queensborough Community College of the City University of New York, Bayside, New York 11364, United States
| | - Sharon I. Lall-Ramnarine
- Chemistry Department, Queensborough Community College of the City University of New York, Bayside, New York 11364, United States
| | - James F. Wishart
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973, United States
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14
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Sanchora P, Pandey DK, Rana D, Materny A, Singh DK. Impact of Size and Electronegativity of Halide Anions on Hydrogen Bonds and Properties of 1-Ethyl-3-methylimidazolium-Based Ionic Liquids. J Phys Chem A 2019; 123:4948-4963. [DOI: 10.1021/acs.jpca.9b04116] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Paridhi Sanchora
- Department of Physics, Institute of Infrastructure Technology Research & Management, Ahmedabad 380026, India
| | - Deepak K. Pandey
- Department of Physics, Institute of Infrastructure Technology Research & Management, Ahmedabad 380026, India
| | - Debkumar Rana
- Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
| | - Arnulf Materny
- Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
| | - Dheeraj K. Singh
- Department of Physics, Institute of Infrastructure Technology Research & Management, Ahmedabad 380026, India
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15
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Niemann T, Strate A, Ludwig R, Zeng HJ, Menges FS, Johnson MA. Cooperatively enhanced hydrogen bonds in ionic liquids: closing the loop with molecular mimics of hydroxy-functionalized cations. Phys Chem Chem Phys 2019; 21:18092-18098. [DOI: 10.1039/c9cp03300a] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The combined experimental and theoretical approach for the gas and the liquid phases provides a quantitative understanding of the competition between differently H-bonded and charged constituents in liquids.
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Affiliation(s)
- Thomas Niemann
- Department of Chemistry
- University of Rostock
- 18059 Rostock
- Germany
- Department Life
| | - Anne Strate
- Department of Chemistry
- University of Rostock
- 18059 Rostock
- Germany
- Department Life
| | - Ralf Ludwig
- Department of Chemistry
- University of Rostock
- 18059 Rostock
- Germany
- Department Life
| | - Helen J. Zeng
- Sterling Chemistry Laboratory
- Yale University
- New Haven
- USA
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16
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Niemann T, Stange P, Strate A, Ludwig R. Like-likes-Like: Cooperative Hydrogen Bonding Overcomes Coulomb Repulsion in Cationic Clusters with Net Charges up to Q=+6e. Chemphyschem 2018; 19:1691-1695. [PMID: 29633456 PMCID: PMC6099258 DOI: 10.1002/cphc.201800293] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Indexed: 01/30/2023]
Abstract
Quantum chemical calculations have been employed to study kinetically stable cationic clusters, wherein the monovalent cations are trapped by hydrogen bonding despite strongly repulsive electrostatic forces. We calculated linear and cyclic clusters of the hydroxy-functionalized cation N-(3-hydroxypropyl) pyridinium, commonly used as cation in ionic liquids. The largest kinetically stable cluster was a cyclic hexamer that very much resembles the structural motifs of molecular clusters, as known for water and alcohols. Surprisingly, strong cooperative hydrogen bonds overcome electrostatic repulsion and result in cationic clusters with a high net charge up to Q=+6e. The structural, spectroscopic, and electronic signatures of the cationic and related molecular clusters of 3-phenyl-1-propanol could be correlated to NBO parameters, supporting the existence of "anti-electrostatic" hydrogen bonds (AEHB), as recently suggested by Weinhold. We also showed that dispersion forces enhance the cationic cluster formation and compensate the electrostatic repulsion of one additional positive charge.
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Affiliation(s)
- Thomas Niemann
- Universität Rostock, Institut für ChemieAbteilung für Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Peter Stange
- Universität Rostock, Institut für ChemieAbteilung für Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Anne Strate
- Universität Rostock, Institut für ChemieAbteilung für Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Ralf Ludwig
- Universität Rostock, Institut für ChemieAbteilung für Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V.Albert-Einstein-Str. 29a18059RostockGermany
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17
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Menges FS, Zeng HJ, Kelleher PJ, Gorlova O, Johnson MA, Niemann T, Strate A, Ludwig R. Structural Motifs in Cold Ternary Ion Complexes of Hydroxyl-Functionalized Ionic Liquids: Isolating the Role of Cation-Cation Interactions. J Phys Chem Lett 2018; 9:2979-2984. [PMID: 29750531 DOI: 10.1021/acs.jpclett.8b01130] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We address the competition between intermolecular forces underlying the recent observation that ionic liquids (ILs) with a hydroxyl-functionalized cation can form domains with attractive interactions between the nominally repulsive positively charged constituents. Here we show that this behavior is present even in the isolated ternary (HEMIm+)2NTf2- complex (HEMIm+ = 1-(2-hydroxyethyl)-3-methylimidazolium) cooled to about 35 K in a photodissociation mass spectrometer. Of the three isomers isolated by double resonance techniques, one is identified to exhibit direct contact between the cations. This linkage involves a cooperative H-bond wherein the OH group on one cation binds to the OH group on the other, which then attaches to the basic N atom of the anion. Formation of this motif comes at the expense of the usually dominant interaction of the acidic C(2)H group on the Im ring with molecular anions, as evidenced by isomer-dependent shifts in the C(2)H vibrational fundamentals.
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Affiliation(s)
- Fabian S Menges
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Helen J Zeng
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Patrick J Kelleher
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Olga Gorlova
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Mark A Johnson
- Sterling Chemistry Laboratory , Yale University , New Haven , Connecticut 06520 , United States
| | - Thomas Niemann
- Department of Chemistry , University of Rostock , 18059 Rostock , Germany
- Leibniz-Institut für Katalyse e.V. , Albert-Einstein-Strasse 29a , 18059 Rostock , Germany
| | - Anne Strate
- Department of Chemistry , University of Rostock , 18059 Rostock , Germany
- Leibniz-Institut für Katalyse e.V. , Albert-Einstein-Strasse 29a , 18059 Rostock , Germany
| | - Ralf Ludwig
- Department of Chemistry , University of Rostock , 18059 Rostock , Germany
- Leibniz-Institut für Katalyse e.V. , Albert-Einstein-Strasse 29a , 18059 Rostock , Germany
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18
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Gutiérrez A, Atilhan M, Alcalde R, Trenzado J, Aparicio S. Insights on the mixtures of imidazolium based ionic liquids with molecular solvents. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.01.167] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Patrick AL, Vogelhuber KM, Prince BD, Annesley CJ. Theoretical and Experimental Insights into the Dissociation of 2-Hydroxyethylhydrazinium Nitrate Clusters Formed via Electrospray. J Phys Chem A 2018; 122:1960-1966. [PMID: 29382196 DOI: 10.1021/acs.jpca.7b12072] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ionic liquids are used for myriad applications, including as catalysts, solvents, and propellants. Specifically, 2-hydroxyethylhydrazinium nitrate (HEHN) has been developed as a chemical propellant for space applications. The gas-phase behavior of HEHN ions and clusters is important in understanding its potential as an electrospray thruster propellant. Here, the unimolecular dissociation pathways of two clusters are experimentally observed, and theoretical modeling of hydrogen bonding and dissociation pathways is used to help rationalize those observations. The cation/deprotonated cation cluster [HEH2 - H]+, which is observed from electrospray ionization, is calculated to be considerably more stable than the complementary cation/protonated anion adduct, [HEH + HNO3]+, which is not observed experimentally. Upon collisional activation, a larger cluster [(HEHN)2HEH]+ undergoes dissociation via loss of nitric acid at lower collision energies, as predicted theoretically. At higher collision energies, additional primary and secondary loss pathways open, including deprotonated cation loss, ion-pair loss, and double-nitric-acid loss. Taken together, these experimental and theoretical results contribute to a foundational understanding of the dissociation of protic ionic liquid clusters in the gas phase.
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Affiliation(s)
- Amanda L Patrick
- Space Vehicles Directorate, Air Force Research Laboratory, Kirtland Air Force Base , New Mexico 87117, United States
| | - Kristen M Vogelhuber
- Space Vehicles Directorate, Air Force Research Laboratory, Kirtland Air Force Base , New Mexico 87117, United States.,Institute for Scientific Research, Boston College , Chestnut Hill, Massachusetts 02467, United States
| | - Benjamin D Prince
- Space Vehicles Directorate, Air Force Research Laboratory, Kirtland Air Force Base , New Mexico 87117, United States
| | - Christopher J Annesley
- Space Vehicles Directorate, Air Force Research Laboratory, Kirtland Air Force Base , New Mexico 87117, United States
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20
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Gorlova O, Craig SM, Johnson MA. Communication: Spectroscopic characterization of a strongly interacting C(2)H group on the EMIM+ cation in the (EMIM+)2X− (X = BF4, Cl, Br, and I) ternary building blocks of ionic liquids. J Chem Phys 2017; 147:231101. [DOI: 10.1063/1.5009009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Olga Gorlova
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520-8107, USA
| | - Stephanie M. Craig
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520-8107, USA
| | - Mark A. Johnson
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520-8107, USA
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21
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Dzugan LC, Matthews J, Sinha A, McCoy AB. Role of Torsion-Vibration Coupling in the Overtone Spectrum and Vibrationally Mediated Photochemistry of CH3OOH and HOOH. J Phys Chem A 2017; 121:9262-9274. [DOI: 10.1021/acs.jpca.7b09778] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Laura C. Dzugan
- Department
of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Jamie Matthews
- Analyst Research Laboratories, Ilan Ramon St. 2, Ness Ziona 7403635, Israel
| | - Amitabha Sinha
- Department
of Chemistry and Biochemistry, University of California, 9500 Gilman
Drive, La Jolla, San Diego, California 92093, United States
| | - Anne B. McCoy
- Department
of Chemistry, University of Washington, Seattle, Washington 98195, United States
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22
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Hunt PA. Quantum Chemical Modeling of Hydrogen Bonding in Ionic Liquids. Top Curr Chem (Cham) 2017; 375:59. [PMID: 28523638 PMCID: PMC5480408 DOI: 10.1007/s41061-017-0142-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2017] [Accepted: 04/16/2017] [Indexed: 01/18/2023]
Abstract
Hydrogen bonding (H-bonding) is an important and very general phenomenon. H-bonding is part of the basis of life in DNA, key in controlling the properties of water and ice, and critical to modern applications such as crystal engineering, catalysis applications, pharmaceutical and agrochemical development. H-bonding also plays a significant role for many ionic liquids (IL), determining the secondary structuring and affecting key physical parameters. ILs exhibit a particularly diverse and wide range of traditional as well as non-standard forms of H-bonding, in particular the doubly ionic H-bond is important. Understanding the fundamental nature of the H-bonds that form within ILs is critical, and one way of accessing this information, that cannot be recovered by any other computational method, is through quantum chemical electronic structure calculations. However, an appropriate method and basis set must be employed, and a robust procedure for determining key structures is essential. Modern generalised solvation models have recently been extended to ILs, bringing both advantages and disadvantages. QC can provide a range of information on geometry, IR and Raman spectra, NMR spectra and at a more fundamental level through analysis of the electronic structure.
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Affiliation(s)
- Patricia A Hunt
- Imperial College of Science, Technology and Medicine, London, UK.
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23
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Abstract
Vibrational spectroscopy has continued use as a powerful tool to characterize ionic liquids since the literature on room temperature molten salts experienced the rapid increase in number of publications in the 1990's. In the past years, infrared (IR) and Raman spectroscopies have provided insights on ionic interactions and the resulting liquid structure in ionic liquids. A large body of information is now available concerning vibrational spectra of ionic liquids made of many different combinations of anions and cations, but reviews on this literature are scarce. This review is an attempt at filling this gap. Some basic care needed while recording IR or Raman spectra of ionic liquids is explained. We have reviewed the conceptual basis of theoretical frameworks which have been used to interpret vibrational spectra of ionic liquids, helping the reader to distinguish the scope of application of different methods of calculation. Vibrational frequencies observed in IR and Raman spectra of ionic liquids based on different anions and cations are discussed and eventual disagreements between different sources are critically reviewed. The aim is that the reader can use this information while assigning vibrational spectra of an ionic liquid containing another particular combination of anions and cations. Different applications of IR and Raman spectroscopies are given for both pure ionic liquids and solutions. Further issues addressed in this review are the intermolecular vibrations that are more directly probed by the low-frequency range of IR and Raman spectra and the applications of vibrational spectroscopy in studying phase transitions of ionic liquids.
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Affiliation(s)
- Vitor H Paschoal
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo , Av. Prof. Lineu Prestes 748, São Paulo 05508-000, Brazil
| | - Luiz F O Faria
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo , Av. Prof. Lineu Prestes 748, São Paulo 05508-000, Brazil
| | - Mauro C C Ribeiro
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo , Av. Prof. Lineu Prestes 748, São Paulo 05508-000, Brazil
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24
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Strate A, Niemann T, Ludwig R. Controlling the kinetic and thermodynamic stability of cationic clusters by the addition of molecules or counterions. Phys Chem Chem Phys 2017; 19:18854-18862. [DOI: 10.1039/c7cp02227a] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We discuss the stability of cationic clusters when adding molecules or counterions, and predict their occurrence in gas phase experiments.
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Affiliation(s)
- Anne Strate
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- Rostock
- Germany
| | - Thomas Niemann
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- Rostock
- Germany
| | - Ralf Ludwig
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- Rostock
- Germany
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25
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Sung W, Kim D. Observation of isolated ionic liquid cations and water molecules in an inert solvent. Phys Chem Chem Phys 2016; 18:27529-27535. [PMID: 27711686 DOI: 10.1039/c6cp05292d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
1-Octyl-3-methyl imidazolium halides ([OMIM]I and [OMIM]Cl) were loaded on top of CCl4, and an in situ inclusion process was monitored from the CCl4 phase as time elapses by infrared absorption spectroscopy. Absorption from the bands corresponding to the C(2)-H and C(4,5)-H stretch modes in the imidazolium cation was reduced significantly compared to the bulk IL spectra. This indicates that (1) the [OMIM] cation exists in CCl4 as a monomer, dissociated from the anion and other cations, and (2) hydrogen bonding between the anion and the cation increases the dipole strength of the CH moieties in the imidazolium ring. [OMIM]I was found to transfer into the CCl4 phase much faster than [OMIM]Cl, and this instigated us to compare the transfer of aqueous solutions of ionic liquids, 1-butyl-3-methyl imidazolium halides ([BMIM]I and [BMIM]Cl) into the CCl4 matrix. Not only [BMIM]I but also water molecules transferred faster compared to those in the [BMIM]Cl aqueous solution. Water molecules in CCl4 were shown to form clusters in [BMIM]I; presumably, I- anions work as nucleation centers of water clusters.
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Affiliation(s)
- Woongmo Sung
- Department of Physics, Sogang University, Seoul 121-742, Korea.
| | - Doseok Kim
- Department of Physics, Sogang University, Seoul 121-742, Korea.
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26
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Bhattacherjee A, Wategaonkar S. Water bridges anchored by a C–H⋯O hydrogen bond: the role of weak interactions in molecular solvation. Phys Chem Chem Phys 2016; 18:27745-27749. [DOI: 10.1039/c6cp05469b] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen-bonded water bridges are re-directed from a polar NH bond to a weakly activated C(2)–H bond upon N-methylation. Infrared spectra, supported by ab initio calculations, provide direct evidence of the role of the C(2)–H donor in the solvation of the imidazole ring.
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Affiliation(s)
- Aditi Bhattacherjee
- Department of Chemical Sciences
- Tata Institute of Fundamental Research
- Mumbai 400 005
- India
| | - Sanjay Wategaonkar
- Department of Chemical Sciences
- Tata Institute of Fundamental Research
- Mumbai 400 005
- India
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27
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Voss JM, Marsh BM, Zhou J, Garand E. Interaction between ionic liquid cation and water: infrared predissociation study of [bmim]+·(H2O)n clusters. Phys Chem Chem Phys 2016; 18:18905-13. [DOI: 10.1039/c6cp02730j] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The infrared predissociation spectra of [bmim]+·(H2O)n, n = 1–8, in the 2800–3800 cm−1 region are presented and analyzed with the help of electronic structure calculations.
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Affiliation(s)
- Jonathan M. Voss
- Department of Chemistry
- University of Wisconsin-Madison
- Madison
- USA
| | - Brett M. Marsh
- Department of Chemistry
- University of Wisconsin-Madison
- Madison
- USA
| | - Jia Zhou
- Department of Chemistry
- University of Wisconsin-Madison
- Madison
- USA
| | - Etienne Garand
- Department of Chemistry
- University of Wisconsin-Madison
- Madison
- USA
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28
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Booth RS, Annesley CJ, Young JW, Vogelhuber KM, Boatz JA, Stearns JA. Identification of multiple conformers of the ionic liquid [emim][tf2n] in the gas phase using IR/UV action spectroscopy. Phys Chem Chem Phys 2016; 18:17037-43. [DOI: 10.1039/c6cp02657e] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have identified three families of conformers in gas phase ion pairs of [emim][tf2n] using IR/UV spectroscopy.
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Affiliation(s)
- Ryan S. Booth
- Space Vehicles Directorate
- Air Force Research Laboratory
- Kirtland AFB
- USA
- Institute for Scientific Research
| | | | - Justin W. Young
- Space Vehicles Directorate
- Air Force Research Laboratory
- Kirtland AFB
- USA
- Institute for Scientific Research
| | - Kristen M. Vogelhuber
- Space Vehicles Directorate
- Air Force Research Laboratory
- Kirtland AFB
- USA
- Institute for Scientific Research
| | - Jerry A. Boatz
- Aerospace Systems Directorate
- Air Force Research Laboratory
- Edwards AFB
- USA
| | - Jaime A. Stearns
- Space Vehicles Directorate
- Air Force Research Laboratory
- Kirtland AFB
- USA
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29
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Hanke K, Kaufmann M, Schwaab G, Havenith M, Wolke CT, Gorlova O, Johnson MA, Kar BP, Sander W, Sanchez-Garcia E. Understanding the ionic liquid [NC4111][NTf2] from individual building blocks: an IR-spectroscopic study. Phys Chem Chem Phys 2015; 17:8518-29. [PMID: 25749545 DOI: 10.1039/c5cp00116a] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This study explores the interactions underlying the IR spectra of the ionic liquid [NC4111][NTf2] and its deuterated isotopomer [d9-NC4111][NTf2] by first isolating the spectra of charged ionic building blocks using mass-selective CIVP spectroscopy and then following the evolution of these bands upon sequential assembly of the ionic constituents. The spectra of the (1,1) and (2,2) neutral ion pairs are recorded using superfluid helium droplets as well as a solid neon matrix, while those of the larger charged aggregates are again obtained with CIVP. In general, the cluster spectra are similar to that of the bulk, with the (2,2) system displaying the closest resemblance. Analysis of the polarization-dependent band intensities of the neutral ion pairs in liquid droplets as a function of external electric field yields dipole moments of the neutral aggregates. This information allows a coarse assessment of the packing structure of the neutral pairs to be antiparallel at 0.37 K, in contrast to the parallel arrangement found for the assembly of small, high-dipole neutral molecules with large rotational constants (e.g., HCN). The role of an extra anion or cation attached to both the (1,1) and the (2,2) ion pairs to form the charged clusters is discussed in the context of an additional remote, more unfavorable binding site intrinsic to the nature of the charged IL clusters and as such not anticipated in the bulk phase. Whereas for the anion itself only the lowest energy trans conformer was observed, the higher clusters showed an additional population of the cis conformer. The interactions are found to be consistent with a minimal role of hydrogen bonding.
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Affiliation(s)
- Kenny Hanke
- Department of Physical Chemistry II, Ruhr-University Bochum, D-44801 Bochum, Germany.
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30
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Bhattacherjee A, Wategaonkar S. Conformational preferences of monohydrated clusters of imidazole derivatives revisited. Phys Chem Chem Phys 2015; 17:20080-92. [DOI: 10.1039/c5cp02422f] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
IR-UV double resonance spectroscopy was used to identify the conformers of monohydrated benzimidazole andN-methylbenzimidazole in a supersonic jet. A new OH–N bound conformer relevant to histidine containing proteins was discovered. The long standing differences in the literature about the relative energies and abundance of the monohydrated imidazole derivatives have also been resolved.
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Affiliation(s)
- Aditi Bhattacherjee
- Department of Chemical Sciences
- Tata Institute of Fundamental Research
- Mumbai 400 005
- India
| | - Sanjay Wategaonkar
- Department of Chemical Sciences
- Tata Institute of Fundamental Research
- Mumbai 400 005
- India
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