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Hunger L, Al Sheakh L, Fritsch S, Villinger A, Ludwig R, Harville P, Moss O, Lachowicz A, Johnson MA. Spectroscopic Evidence for Doubly Hydrogen-Bonded Cationic Dimers in the Solid, Liquid, and Gaseous Phases of Carboxyl-Functionalized Ionic Liquids. J Phys Chem B 2024; 128:5463-5471. [PMID: 38776534 DOI: 10.1021/acs.jpcb.4c02094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
Intermolecular interactions determine whether matter sticks together, gases condense into liquids, or liquids freeze into solids. The most prominent example is hydrogen bonding in water, responsible for the anomalous properties in the liquid phase and polymorphism in ice. The physical properties are also exceptional for ionic liquids (ILs), wherein a delicate balance of Coulomb interactions, hydrogen bonds, and dispersion interactions results in a broad liquid range and the vaporization of ILs as ion pairs. In this study, we show that strong, local, and directional hydrogen bonds govern the structures and arrangements in the solid, liquid, and gaseous phases of carboxyl-functionalized ILs. For that purpose, we explored the H-bonded motifs by X-ray diffraction and attenuated total reflection (ATR) infrared (IR) spectroscopy in the solid state, by ATR and transmission IR spectroscopy in the liquid phase, and by cryogenic ion vibrational predissociation spectroscopy (CIVPS) in the gaseous phase at low temperature. The analysis of the CO stretching bands reveals doubly hydrogen-bonded cationic dimers (c═c), resembling the archetype H-bond motif known for carboxylic acids. The like-charge doubly hydrogen-bonded ion pairs are present in the crystal structure of the IL, survive phase transition into the liquid state, and are still present in the gaseous phase even in (2,1) complexes wherein one counterion is removed and repulsive Coulomb interaction increased. The interpretation of the vibrational spectra is supported by quantum chemical methods. These observations have implications for the fundamental nature of the hydrogen bond between ions of like charge.
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Affiliation(s)
- Lasse Hunger
- Department of Chemistry, University of Rostock, 18059 Rostock, Germany
- Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany
| | - Loai Al Sheakh
- Department of Chemistry, University of Rostock, 18059 Rostock, Germany
- Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany
| | - Sebastian Fritsch
- Department of Chemistry, University of Rostock, 18059 Rostock, Germany
- Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany
| | | | - Ralf Ludwig
- Department of Chemistry, University of Rostock, 18059 Rostock, Germany
- Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany
- Leibniz-Institut für Katalyse e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
| | - Payten Harville
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Olivia Moss
- Sterling Chemistry Laboratory, Yale University, New Haven, Connecticut 06520, United States
| | - Anton Lachowicz
- 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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Hunger L, Ludwig R, Chuang YC, Chang HC. Hydroxy-Functionalized Ionic Liquids under Pressure: The Influence on Hydrogen Bonding between Ions of Opposite and Like Charges. J Phys Chem B 2024. [PMID: 38696327 DOI: 10.1021/acs.jpcb.4c01520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2024]
Abstract
Hydroxy functionalization of cations in ionic liquids (ILs) can lead to formation of hydrogen bonds between their OH groups, resulting in so-called (c-c) H-bonds. Thereby, the (c-c) H-bonds compete with regular H-bonds (c-a) between the OH groups and the anions. Polarizable cations, weakly interacting anions, and long alkyl chains at the cation support the propensity for the formation of (c-c) H-bonds. At low temperatures, the equilibrium between (c-c) and (c-a) H-bonds is strongly shifted in favor of the cation-cation interaction. Herein, we clarify the pressure dependence on (c-c) and (c-a) H-bond distributions in the IL 1-(2-hydroxyethyl)-3-methylimidazolium hexafluorophosphate [HOC2C1Im][PF6], in mixtures of [HOC2C1Im][PF6] with the nonhydroxy-functionalized IL 1-propyl-3-methylimidazolium hexafluorophosphate [C3C1Im][PF6] and in [HOC2C1Im][PF6] including trace amounts of water. The infrared (IR) spectra provide clear evidence that the (c-c) H-bonds diminish with increasing pressure in favor of the (c-a) H-bonds. Adding trace amounts of water results in enhanced (c-c) clustering due to cooperative effects. At ambient pressure, the water molecules are involved in the (c-c) H-bond motifs. Increasing pressure leads to squeezing them out of H-bond clusters, finally resulting in demixing of water and the IL at the microscopic level.
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Affiliation(s)
- Lasse Hunger
- Department of Chemistry, University of Rostock, 18059 Rostock, Germany
- Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany
| | - Ralf Ludwig
- Department of Chemistry, University of Rostock, 18059 Rostock, Germany
- Department Life, Light & Matter, University of Rostock, 18051 Rostock, Germany
- Leibniz-Institut für Katalyse e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
| | - Yen-Ching Chuang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Hai-Chou Chang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
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Khudozhitkov AE, Stepanov AG, Kolokolov DI, Ludwig R. Ion Mobility in Hydroxy-Functionalized Ionic Liquids Depends on Cationic Clustering: Tracking the Alkyl Chain Length Behavior with Deuteron NMR Relaxation. J Phys Chem B 2023; 127:9336-9345. [PMID: 37857325 DOI: 10.1021/acs.jpcb.3c05330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
Observing and quantifying the like-charge attraction in liquids and solutions is still challenging. However, we showed that elusive cation-cation hydrogen bonding may govern the structure and interaction in hydroxyl-functionalized ionic liquids. Therefore, cationic cluster formation depends on the shape, charge distribution, and functionality of the ions. We demonstrated by means of solid-state 2H NMR spectroscopy that cationic clusters change the structure and dynamics of ionic liquids. With increasing alkyl chain length, we observed two deuteron quadrupole coupling constants for the OD groups, differing by about 30 kHz. The lower value was assigned to the cation-cation interaction, indicating that the average (c-c) hydrogen bonds are stronger than the (c-a) hydrogen bonds between the cation and the anion despite the repulsive and attractive Coulomb interaction in the first and latter cases. Ion mobility could be studied by 2H NMR spectroscopy, although the deuterons in the hydrogen-bonded clusters underwent fast exchange. Our results also showed that simple relaxation models are not applicable anymore and that anisotropic motion must be considered.
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Affiliation(s)
- Alexander E Khudozhitkov
- Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
| | - Alexander G Stepanov
- Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia
| | - Daniil I Kolokolov
- Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
| | - Ralf Ludwig
- Universität Rostock, Institut für Chemie, Abteilung für Physikalische Chemie, Albert-Einstein-Str. 27, 18059 Rostock, Germany
- Department LL&M, University of Rostock, Albert-Einstein-Str. 25, 18059 Rostock, Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
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Khudozhitkov AE, Paschek D, Stepanov AG, Kolokolov DI, Ludwig R. How Like-Charge Attraction Influences the Mobility of Cations in Hydroxyl-Functionalized Ionic Liquids. J Phys Chem Lett 2023; 14:4019-4025. [PMID: 37093004 DOI: 10.1021/acs.jpclett.3c00463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Attractive interactions between ions of like charge remain an elusive concept. Observing and quantifying this type of interaction in liquids and solutions is still a major challenge. Recently, we have shown that cation-cation interactions are present in hydroxyl-functionalized ionic liquids and that they can be controlled by the shape, charge distribution and functionality of the ions. In the present study, we demonstrate that cationic cluster formation does not only change the local structures of the ionic liquids but also influences the dynamics of the cations in a characteristic way. We show that solid-state 2H NMR spectroscopy is well suited for the study of molecular motion, even if the hydrogen bonded species of interest are indistinguishable due to fast deuteron exchange. We also provide valuable information about the applicability of well-accepted relaxation models.
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Affiliation(s)
- Alexander E Khudozhitkov
- Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
| | - Dietmar Paschek
- Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Albert-Einstein-Strasse 27, 18059 Rostock, Germany
| | - Alexander G Stepanov
- Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia
| | - Daniil I Kolokolov
- Boreskov Institute of Catalysis, Siberian Branch of Russian Academy of Sciences, Prospekt Akademika Lavrentieva 5, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
| | - Ralf Ludwig
- Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Albert-Einstein-Strasse 27, 18059 Rostock, Germany
- Department LL&M, University of Rostock, Albert-Einstein-Strasse 25, 18059 Rostock, Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
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Xu S, Liu Y, Li X, Yue B, Huo F, He H, Zhang S. Quantitative Relation between Ionic Diffusivity and Ionic Association in Ionic Liquid-Water Mixtures. J Phys Chem Lett 2023; 14:2708-2714. [PMID: 36892821 DOI: 10.1021/acs.jpclett.2c03610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Molecular dynamic simulations of aqueous mixtures of imidazolium ionic liquids (ILs) were performed to elucidate the dependence of the ionic diffusivity on the microscopic structures changed by water. Two distinct regimes of the average ionic diffusivity (Dave) were identified with the increased water concentrations: the jam regime with slowly increased Dave and the exponential regime with rapidly increased Dave, which are found to be directly correlated to the ionic association. Further analysis leads to two general relationships independent of IL species between Dave and the degree of ionic association: (i) a consistent linear relationship between Dave and the inverse of ion-pair lifetimes (1/τIP) in the two regimes and (ii) an exponential relationship between normalized diffusivities (D̃ave) and short-ranged interactions between cations and anions (Ẽions), with different interdependent strengths in the two regimes. These findings revealed and quantified the direct correlation between dynamic properties and ionic association in IL-water mixtures.
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Affiliation(s)
- Shuting Xu
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of the Chinese Academy of Sciences School of Chemical Engineering, Beijing 100049, P. R. China
| | - Yawei Liu
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Xuefu Li
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Bowen Yue
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
| | - Feng Huo
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
- Zhengzhou Institute of Emerging Industrial Technology, Zhengzhou 450000, China
- Longzihu New Energy Laboratory, Zhengzhou Institute of Emerging Industrial Technology, Henan University, Zhengzhou 450000, P. R. China
| | - Hongyan He
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of the Chinese Academy of Sciences School of Chemical Engineering, Beijing 100049, P. R. China
| | - Suojiang Zhang
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China
- University of the Chinese Academy of Sciences School of Chemical Engineering, Beijing 100049, P. R. China
- Zhengzhou Institute of Emerging Industrial Technology, Zhengzhou 450000, China
- Longzihu New Energy Laboratory, Zhengzhou Institute of Emerging Industrial Technology, Henan University, Zhengzhou 450000, P. R. China
- College of Chemistry and Chemical Engineering, Henan University, Zhengzhou 451460, China
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6
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F. T. de Souza Í, C. C. Ribeiro M. Understanding ion-ion and ion-urea interactions in mixtures of urea and choline oxyanions salts. J Mol Liq 2023. [DOI: 10.1016/j.molliq.2023.121647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2023]
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7
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Song D, Chen J. Regulating the Acidity of SO 3 H-Functionalized Ionic Liquids: Hydrogen Bonding or Electrostatic Potential? Chempluschem 2022; 87:e202200225. [PMID: 36166679 DOI: 10.1002/cplu.202200225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/31/2022] [Indexed: 11/08/2022]
Abstract
The SO3 H-functionalized ionic liquids (ILs) with high acidity are important catalysts for acid-catalyzed reactions. However, the acidity of these ILs have been found to decrease due to intramolecular hydrogen bonds (H-bonds). In this work, a series of anionic SO3 H-functionalized ILs were designed and the factors resulting in weak acidity were investigated, including H-bonds strength and electrostatic potential on the leaving proton (ESPLP). Using catalytic experiment, atoms in molecules topology analysis and electrostatic potential calculation, it was found that the acidity of ILs was correlated with the value of ESPLP rather than the H-bond strength. Meanwhile, there were several ways to increase the acidity of anionic SO3 H-functionalized ILs, such as enhancing the electron-withdrawing ability of cation, introducing H-bond acceptor sites on cation or separating the intramolecular H-bonds through substitution position. These strategies made the conversion of TBA in Friedel-Crafts alkylation increase from 19 % to 84 %.
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Affiliation(s)
- Dayong Song
- State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, P. R. China.,College of Resources and Environmental Engineering Department, Shandong Agriculture and Engineering University, Jinan, 250100, P. R. China
| | - Jing Chen
- State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou, 730000, P. R. China
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Hunger L, Al‐Sheakh L, Zaitsau DH, Verevkin SP, Appelhagen A, Villinger A, Ludwig R. Dissecting Noncovalent Interactions in Carboxyl‐Functionalized Ionic Liquids Exhibiting Double and Single Hydrogens Bonds Between Ions of Like Charge. Chemistry 2022; 28:e202200949. [PMID: 35785500 PMCID: PMC9543318 DOI: 10.1002/chem.202200949] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Lasse Hunger
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Albert-Einstein-Str. 27 18059 Rostock Germany
| | - Loai Al‐Sheakh
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Albert-Einstein-Str. 27 18059 Rostock Germany
| | - Dzmitry H. Zaitsau
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Albert-Einstein-Str. 27 18059 Rostock Germany
- Department LL&M University of Rostock Albert-Einstein-Str. 25 18059 Rostock Germany
| | - Sergey P. Verevkin
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Albert-Einstein-Str. 27 18059 Rostock Germany
- Department LL&M University of Rostock Albert-Einstein-Str. 25 18059 Rostock Germany
| | - Andreas Appelhagen
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Albert-Einstein-Str. 27 18059 Rostock Germany
| | - Alexander Villinger
- Institut für Chemie Abteilung für Anorganische Chemie Universität Rostock Albert-Einstein-Str. 3a 18059 Rostock Germany
| | - Ralf Ludwig
- Institut für Chemie Abteilung für Physikalische Chemie Universität Rostock Albert-Einstein-Str. 27 18059 Rostock Germany
- Department LL&M University of Rostock Albert-Einstein-Str. 25 18059 Rostock Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V. Albert-Einstein-Str. 29a 18059 Rostock Germany
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9
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Computational approaches to structural properties investigation of triethylammonium- and triethanolammonium-based protic ionic liquids. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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10
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Bodo E. Perspectives in the Computational Modeling of New Generation, Biocompatible Ionic Liquids. J Phys Chem B 2022; 126:3-13. [PMID: 34978449 PMCID: PMC8762658 DOI: 10.1021/acs.jpcb.1c09476] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 12/15/2021] [Indexed: 12/11/2022]
Abstract
In this Perspective, I review the current state of computational simulations on ionic liquids with an emphasis on the recent biocompatible variants. These materials are used here as an example of relatively complex systems that highlights the limits of some of the approaches commonly used to study their structure and dynamics. The source of these limits consists of the coexistence of nontrivial electrostatic, many-body quantum effects, strong hydrogen bonds, and chemical processes affecting the mutual protonation state of the constituent molecular ions. I also provide examples on how it is possible to overcome these problems using suitable simulation paradigms and recently improved techniques that, I expect, will be gradually introduced in the state-of-the-art of computational simulations of ionic liquids.
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Affiliation(s)
- Enrico Bodo
- Chemistry Department, University of Rome “La Sapienza”, P. A. Moro 5, 00185 Rome, Italy
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Al-Sheakh L, Fritsch S, Appelhagen A, Villinger A, Ludwig R. Thermodynamically Stable Cationic Dimers in Carboxyl-Functionalized Ionic Liquids: The Paradoxical Case of "Anti-Electrostatic" Hydrogen Bonding. Molecules 2022; 27:molecules27020366. [PMID: 35056680 PMCID: PMC8778807 DOI: 10.3390/molecules27020366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 12/28/2021] [Accepted: 01/03/2022] [Indexed: 11/18/2022] Open
Abstract
We show that carboxyl-functionalized ionic liquids (ILs) form doubly hydrogen-bonded cationic dimers (c+=c+) despite the repulsive forces between ions of like charge and competing hydrogen bonds between cation and anion (c+–a−). This structural motif as known for formic acid, the archetype of double hydrogen bridges, is present in the solid state of the IL 1−(carboxymethyl)pyridinium bis(trifluoromethylsulfonyl)imide [HOOC−CH2−py][NTf2]. By means of quantum chemical calculations, we explored different hydrogen-bonded isomers of neutral (HOOC–(CH2)n–py+)2(NTf2−)2, single-charged (HOOC–(CH2)n–py+)2(NTf2−), and double-charged (HOOC– (CH2)n−py+)2 complexes for demonstrating the paradoxical case of “anti-electrostatic” hydrogen bonding (AEHB) between ions of like charge. For the pure doubly hydrogen-bonded cationic dimers (HOOC– (CH2)n−py+)2, we report robust kinetic stability for n = 1–4. At n = 5, hydrogen bonding and dispersion fully compensate for the repulsive Coulomb forces between the cations, allowing for the quantification of the two equivalent hydrogen bonds and dispersion interaction in the order of 58.5 and 11 kJmol−1, respectively. For n = 6–8, we calculated negative free energies for temperatures below 47, 80, and 114 K, respectively. Quantum cluster equilibrium (QCE) theory predicts the equilibria between cationic monomers and dimers by considering the intermolecular interaction between the species, leading to thermodynamic stability at even higher temperatures. We rationalize the H-bond characteristics of the cationic dimers by the natural bond orbital (NBO) approach, emphasizing the strong correlation between NBO-based and spectroscopic descriptors, such as NMR chemical shifts and vibrational frequencies.
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Affiliation(s)
- Loai Al-Sheakh
- Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (L.A.-S.); (S.F.); (A.A.)
| | - Sebastian Fritsch
- Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (L.A.-S.); (S.F.); (A.A.)
| | - Andreas Appelhagen
- Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (L.A.-S.); (S.F.); (A.A.)
| | - Alexander Villinger
- Institut für Chemie, Abteilung für Anorganische Chemie, Universität Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany;
| | - Ralf Ludwig
- Institut für Chemie, Abteilung für Physikalische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany; (L.A.-S.); (S.F.); (A.A.)
- Department LL&M, University of Rostock, Albert-Einstein−Str. 25, 18059 Rostock, Germany
- Leibniz−Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein−Str. 29a, 18059 Rostock, Germany
- Correspondence:
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12
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Ludwig R. Towards thermodynamically stable anionic dimers with “anti-electrostatic” hydrogen bonds overcoming like-charge repulsion. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.116882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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13
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de Souza ÍF, Paschoal VH, Bernardino K, Lima TA, Daemen LL, Z Y, Ribeiro MC. Vibrational spectroscopy and molecular dynamics simulation of choline oxyanions salts. J Mol Liq 2021. [DOI: 10.1016/j.molliq.2021.117100] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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14
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Al Sheakh L, Niemann T, Villinger A, Stange P, Zaitsau DH, Strate A, Ludwig R. Three in One: The Versatility of Hydrogen Bonding Interaction in Halide Salts with Hydroxy-Functionalized Pyridinium Cations. Chemphyschem 2021; 22:1850-1856. [PMID: 34241946 PMCID: PMC8518508 DOI: 10.1002/cphc.202100424] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 07/08/2021] [Indexed: 11/28/2022]
Abstract
The paradigm of supramolecular chemistry relies on the delicate balance of noncovalent forces. Here we present a systematic approach for controlling the structural versatility of halide salts by the nature of hydrogen bonding interactions. We synthesized halide salts with hydroxy-functionalized pyridinium cations [HOCn Py]+ (n=2, 3, 4) and chloride, bromide and iodide anions, which are typically used as precursor material for synthesizing ionic liquids by anion metathesis reaction. The X-ray structures of these omnium halides show two types of hydrogen bonding: 'intra-ionic' H-bonds, wherein the anion interacts with the hydroxy group and the positively charged ring at the same cation, and 'inter-ionic' H-bonds, wherein the anion also interacts with the hydroxy group and the ring system but of different cations. We show that hydrogen bonding is controllable by the length of the hydroxyalkyl chain and the interaction strength of the anion. Some molten halide salts exhibit a third type of hydrogen bonding. IR spectra reveal elusive H-bonds between the OH groups of cations, showing interaction between ions of like charge. They are formed despite the repulsive interaction between the like-charged ions and compete with the favored cation-anion H-bonds. All types of H-bonding are analyzed by quantum chemical methods and the natural bond orbital approach, emphasizing the importance of charge transfer in these interactions. For simple omnium salts, we evidenced three distinct types of hydrogen bonds: Three in one!
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Affiliation(s)
- Loai Al Sheakh
- Universität RostockInstitut für Chemie, Abteilung für Physikalische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Thomas Niemann
- Universität RostockInstitut für Chemie, Abteilung für Physikalische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Alexander Villinger
- Institut für Chemie, Abteilung für Anorganische ChemieUniversität RostockAlbert-Einstein-Strasse 3a18059RostockGermany
| | - Peter Stange
- Universität RostockInstitut für Chemie, Abteilung für Physikalische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Dzmitry H. Zaitsau
- Universität RostockInstitut für Chemie, Abteilung für Physikalische ChemieDr.-Lorenz-Weg 218059RostockGermany
- Department LL&MUniversity of RostockAlbert-Einstein-Str. 2518059RostockGermany
| | - Anne Strate
- Universität RostockInstitut für Chemie, Abteilung für Physikalische ChemieDr.-Lorenz-Weg 218059RostockGermany
- Department LL&MUniversity of RostockAlbert-Einstein-Str. 2518059RostockGermany
| | - Ralf Ludwig
- Universität RostockInstitut für Chemie, Abteilung für Physikalische ChemieDr.-Lorenz-Weg 218059RostockGermany
- Department LL&MUniversity of RostockAlbert-Einstein-Str. 2518059RostockGermany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V.Albert-Einstein-Str. 29a18059RostockGermany
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15
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Palumbo O, Cimini A, Trequattrini F, Brubach JB, Roy P, Paolone A. Evidence of the CH···O HydrogenBonding in Imidazolium-Based Ionic Liquids from Far-Infrared Spectroscopy Measurements and DFT Calculations. Int J Mol Sci 2021; 22:ijms22116155. [PMID: 34200392 PMCID: PMC8201385 DOI: 10.3390/ijms22116155] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 06/04/2021] [Accepted: 06/04/2021] [Indexed: 12/14/2022] Open
Abstract
Knowledge of all the intermolecular forces occurring in ionic liquids (ILs) is essential to master their properties. Aiming at investigating the weaker hydrogen bonding in aprotic liquids, the present work combined computational study and far-infrared spectroscopy on four imidazolium-based ILs with different anions. The DFT calculations of the ionic couples, using the ωB97X-D functional and considering both the empirical dispersion corrections and the presence of a polar solvent, show that, for all samples, the lowest energy configurations of the ion pair present H atoms, directly bound to C atoms of the cation and close to O atoms of the anion, capable of creating moderate to weak hydrogen bonding with anions. For the liquids containing anions of higher bonding ability, the absorption curves generated from the calculated vibrational frequencies and intensities show absorption bands between 100 and 125 cm−1 corresponding to the stretching of the hydrogen bond. These indications are in complete agreement with the presently reported temperature dependence of the far-infrared spectrum, where the stretching modes of the hydrogen bonding are detected only for samples presenting a moderate interaction and become particularly prominent at low temperatures. Moreover, from the analysis of the infrared spectra, the occurrence of various phase transitions as a function of temperature was detected, and the difference in the average energy between the H-bonded and the dispersion-governed molecular configurations was evaluated.
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Affiliation(s)
- Oriele Palumbo
- CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy; (O.P.); (A.C.); (A.P.)
| | - Adriano Cimini
- CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy; (O.P.); (A.C.); (A.P.)
| | - Francesco Trequattrini
- CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy; (O.P.); (A.C.); (A.P.)
- Physics Department, Sapienza University of Rome, Piazzale A. Moro 5, 00185 Rome, Italy
- Correspondence:
| | - Jean-Blaise Brubach
- Synchrotron SOLEIL, AILES Beamline, L’Orme des Merisiers Saint-Aubin, BP 48, CEDEX, 91192 Gif-sur-Yvette, France; (J.-B.B.); (P.R.)
| | - Pascale Roy
- Synchrotron SOLEIL, AILES Beamline, L’Orme des Merisiers Saint-Aubin, BP 48, CEDEX, 91192 Gif-sur-Yvette, France; (J.-B.B.); (P.R.)
| | - Annalisa Paolone
- CNR-ISC, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Rome, Italy; (O.P.); (A.C.); (A.P.)
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16
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Bodo E. Modelling biocompatible ionic liquids based on organic acids and amino acids: challenges for computational models and future perspectives. Org Biomol Chem 2021; 19:4002-4013. [PMID: 33978045 DOI: 10.1039/d1ob00011j] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this short review I shall highlight the basic principle and the difficulties that arise in attempting the computational modeling of seemingly simple systems which hide an unexpected complexity. Biocompatible ionic liquids which are based on the coupling of organic or amino acid anions with metabolic cations such as cholinium are the target of this review. These substances have been the subject of intense research activities in the last few years and have attracted the attention of computational chemists. I shall show that the computational description of these substances is far from trivial and requires the use of sophisticated techniques in order to account for a surprisingly rich chemistry that is due to several phenomena such as polarization, charge transfer, proton transfer equilibria and tautomerization reactions.
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Affiliation(s)
- Enrico Bodo
- Chemistry Department, University of Rome "La Sapienza", P. A. Moro 5, 00185 Rome, Italy.
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17
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Chen J, Dong K, Liu L, Zhang X, Zhang S. Anti-electrostatic hydrogen bonding between anions of ionic liquids: a density functional theory study. Phys Chem Chem Phys 2021; 23:7426-7433. [PMID: 33876102 DOI: 10.1039/d0cp06718k] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hydrogen bonds (HBs) play a crucial role in the physicochemical properties of ionic liquids (ILs). To date, HBs between cations and anions (Ca-An) or between cations (Ca-Ca) in ILs have been reported extensively. Here, we provided DFT evidence for the existence of HBs between anions (An-An) in the IL 1-(2-hydroxyethyl)-3-methylimidazolium 4-(2-hydroxyethyl)imidazolide [HEMIm][HEIm]. The thermodynamic stabilities of anionic, cationic, and H2O dimers together with ionic pairs were studied using potential energy scans. The results show that the cation-anion pair is the most stable one, while the HB in the anionic dimer possesses similar thermodynamic stability to the water dimer. The further geometric, spectral and electronic structure analyses demonstrate that the inter-anionic HB meets the general theoretical criteria of traditional HBs. The strength order of four HBs in complexes is cation-anion pair > H2O dimer ≈ cationic dimer > anionic dimer. The energy decomposition analysis indicates that induction and dispersion interactions are the crucial factors to overcome strong Coulomb repulsions, forming inter-anionic HBs. Finally, the presence of inter-anionic HBs in the ionic cluster has been confirmed by a global minimum search for a system containing two ionic pairs. Even though hydroxyl-functionalized cations are more likely to form HBs with anions, there are still inter-anionic HBs between hydroxyl groups in the low-lying structures. Our studies broaden the understanding of HBs in ionic liquids and support the recently proposed concept of anti-electrostatic HBs.
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Affiliation(s)
- Junwu Chen
- Beijing Key Laboratory of Ionic Liquids Clean Process, CAS Key Laboratory of Green Process and Engineering, State Key Laboratory of Multiphase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, P. R. China.
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18
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Philippi F, Welton T. Targeted modifications in ionic liquids - from understanding to design. Phys Chem Chem Phys 2021; 23:6993-7021. [PMID: 33876073 DOI: 10.1039/d1cp00216c] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ionic liquids are extremely versatile and continue to find new applications in academia as well as industry. This versatility is rooted in the manifold of possible ion types, ion combinations, and ion variations. However, to fully exploit this versatility, it is imperative to understand how the properties of ionic liquids arise from their constituents. In this work, we discuss targeted modifications as a powerful tool to provide understanding and to enable design. A 'targeted modification' is a deliberate change in the structure of an ionic liquid. This includes chemical changes in an experiment as well as changes to the parameterisation in a computer simulation. In any case, such a change must be purposeful to isolate what is of interest, studying, as far as is possible, only one concept at a time. The concepts can then be used as design elements. However, it is often found that several design elements interact with each other - sometimes synergistically, and other times antagonistically. Targeted modifications are a systematic way of navigating these overlaps. We hope this paper shows that understanding ionic liquids requires experimentalists and theoreticians to join forces and provides a tool to tackle the difficult transition from understanding to design.
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Affiliation(s)
- Frederik Philippi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK.
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19
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Gobbo D, Cavalli A, Ballone P, Benedetto A. Computational analysis of the effect of [Tea][Ms] and [Tea][H 2PO 4] ionic liquids on the structure and stability of Aβ(17-42) amyloid fibrils. Phys Chem Chem Phys 2021; 23:6695-6709. [PMID: 33710213 DOI: 10.1039/d0cp06434c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Experimental studies have reported the possibility of affecting the growth/dissolution of amyloid fibres by the addition of organic salts of the room-temperature ionic-liquid family, raising the tantalizing prospect of controlling these processes under physiological conditions. The effect of [Tea][Ms] and [Tea][H2PO4] at various concentrations on the structure and stability of a simple model of Aβ42 fibrils has been investigated by computational means. Free energy computations show that both [Tea][Ms] and [Tea][H2PO4] decrease the stability of fibrils with respect to isolated peptides in solution, and the effect is significantly stronger for [Tea][Ms]. The secondary structure of fibrils is not much affected, but single peptides in solution show a marked decrease in their β-strand character and an increase in α-propensity, again especially for [Tea][Ms]. These observations, consistent with the experimental picture, can be traced to two primary effects, i.e., the difference in the ionicity of the [Tea][Ms] and [Tea][H2PO4] water solutions and the remarkable affinity of peptides for [Ms]- anions, due to the multiplicity of H-bonds.
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Affiliation(s)
- D Gobbo
- Computational and Chemical Biology, Fondazione Istituto Italiano di Tecnologia, Genova, Italy.
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20
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Neumann J, Paschek D, Strate A, Ludwig R. Kinetics of Hydrogen Bonding between Ions with Opposite and Like Charges in Hydroxyl-Functionalized Ionic Liquids. J Phys Chem B 2021; 125:281-286. [PMID: 33356283 DOI: 10.1021/acs.jpcb.0c09278] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hydrogen-bonded structures and their lifetimes in ionic liquids (ILs) are governed by the subtle balance between Coulomb interactions, hydrogen bonding, and dispersion forces. Despite the dominant Coulomb interaction, local and directional hydrogen bonds (HBs) can play an important role in the behavior of ILs. Compared to water, the archetype of hydrogen-bonded liquids, ILs have larger constituents and higher viscosities but are typically lacking a three-dimensional HB network. Hydroxyl-functionalized ionic liquids are even more special: regular HBs between cations and anions (ca) are accompanied by HBs between pairs of cations (cc). Recently, infrared (IR) measurements have suggested that the (cc) HBs are even stronger than their (ca) counterparts and their strength can be controlled via the hydroxyalkyl chain length. In this paper, we show by means of molecular dynamics (MD) simulations that the presence of HBs has a profound effect on the molecular mobility of the ions. We investigate the kinetic mechanism of hydrogen bonding in ILs and show that the lifetimes and hence the stability of (cc) HBs increase with the chain length, making them more stable than the respective (ca) HBs. The observed HB equilibrium can explain the peculiar chain length dependence of the relative molecular mobilities of the ions by a direct comparison between hydroxyl-functionalized ILs with their nonfunctionalized counterparts.
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Affiliation(s)
- Jan Neumann
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, D-18059 Rostock, Germany
| | - Dietmar Paschek
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, D-18059 Rostock, Germany
| | - Anne Strate
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, D-18059 Rostock, Germany.,Department Life, Light & Matter, Universität Rostock, Albert-Einstein-Straße 25, D-18059 Rostock, Germany
| | - Ralf Ludwig
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, Dr.-Lorenz-Weg 2, D-18059 Rostock, Germany.,Department Life, Light & Matter, Universität Rostock, Albert-Einstein-Straße 25, D-18059 Rostock, Germany.,Leibniz Institut für Katalyse an der Universität Rostock, Albert-Einstein-Straße 29a, D-18059 Rostock, Germany
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21
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Le Donne A, Bodo E. Cholinium amino acid-based ionic liquids. Biophys Rev 2021; 13:147-160. [PMID: 33747249 PMCID: PMC7930144 DOI: 10.1007/s12551-021-00782-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 01/05/2021] [Indexed: 12/12/2022] Open
Abstract
Boosted by the simplicity of their synthesis and low toxicity, cholinium and amino acid-based ionic liquids have attracted the attention of researchers in many different fields ranging from computational chemistry to electrochemistry and medicine. Among the uncountable IL variations, these substances occupy a space on their own due to their exceptional biocompatibility that stems from being entirely made by metabolic molecular components. These substances have undergone a rather intensive research activity because of the possibility of using them as greener replacements for traditional ionic liquids. We present here a short review in the attempt to provide a compendium of the state-of-the-art scientific research about this special class of ionic liquids based on the combination of amino acid anions and cholinium cations.
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Affiliation(s)
- Andrea Le Donne
- Chemistry Department, University of Rome "La Sapienza", Piazzale A. Moro 5, 00185 Rome, Italy
| | - Enrico Bodo
- Chemistry Department, University of Rome "La Sapienza", Piazzale A. Moro 5, 00185 Rome, Italy
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22
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Thomann CA, Münzner P, Moch K, Jacquemin J, Goodrich P, Sokolov AP, Böhmer R, Gainaru C. Tuning the dynamics of imidazolium-based ionic liquids via hydrogen bonding. I. The viscous regime. J Chem Phys 2020; 153:194501. [DOI: 10.1063/5.0026144] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Affiliation(s)
- C. A. Thomann
- Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany
| | - P. Münzner
- Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany
| | - K. Moch
- Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany
| | - J. Jacquemin
- Faculté des Sciences et Techniques, Université de Tours, 37200 Tours, France
- QUILL Center, The Queen’s University of Belfast, Belfast BT9 5AG, Northern Ireland, United Kingdom
| | - P. Goodrich
- QUILL Center, The Queen’s University of Belfast, Belfast BT9 5AG, Northern Ireland, United Kingdom
| | - A. P. Sokolov
- Department of Chemistry, University of Tennessee, Knoxville, Tennessee 37916, USA and Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA
| | - R. Böhmer
- Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany
| | - C. Gainaru
- Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany
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23
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Philipp JK, Fritsch S, Ludwig R. Cyclic Octamer of Hydroxyl-functionalized Cations with Net Charge Q=+8e Kinetically Stabilized by a 'Molecular Island' of Cooperative Hydrogen Bonds. Chemphyschem 2020; 21:2411-2416. [PMID: 32845043 PMCID: PMC7702028 DOI: 10.1002/cphc.202000681] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/20/2020] [Indexed: 11/07/2022]
Abstract
Cyclic octamers are well-known structural motifs in chemistry, biology and physics. These include covalently bound cyclic octameric sulphur, cylic octa-alkanes, cyclo-octameric peptides as well as hydrogen-bonded ring clusters of alcohols. In this work, we show that even calculated cyclic octamers of hydroxy-functionalized pyridinium cations with a net charge Q=+8e are kinetically stable. Eight positively charged cations are kept together by hydrogen bonding despite the strong Coulomb repulsive forces. Sufficiently long hydroxy-octyl chains prevent "Coulomb explosion" by increasing the distance between the positive charges at the pyridinium rings, reducing the Coulomb repulsion and thus strengthen hydrogen bonds between the OH groups. The eightfold positively charged cyclic octamer shows spectroscopic properties similar to those obtained for hydrogen-bonded neutral cyclic octamers of methanol. Thus, the area of the hydrogen bonded OH ring represents a 'molecular island' within an overall cationic environment. Although not observable, the spectroscopic properties and the correlated NBO parameters of the calculated cationic octamer support the detection of smaller cationic clusters in ionic liquids, which we observed despite the competition with ion pairs wherein attractive Coulomb forces enhance hydrogen bonding between cation and anion.
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Affiliation(s)
- Jule Kristin Philipp
- Universität RostockInstitut für ChemieAbteilung Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Sebastian Fritsch
- Universität RostockInstitut für ChemieAbteilung Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
| | - Ralf Ludwig
- Universität RostockInstitut für ChemieAbteilung Physikalische und Theoretische ChemieDr.-Lorenz-Weg 218059RostockGermany
- Universität RostockDepartment LL&MAlbert-Einstein-Str. 2518059RostockGermany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V.Albert-Einstein-Str. 29a18059RostockGermany
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24
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Philipp JK, Ludwig R. Clusters of Hydroxyl-Functionalized Cations Stabilized by Cooperative Hydrogen Bonds: The Role of Polarizability and Alkyl Chain Length. Molecules 2020; 25:molecules25214972. [PMID: 33121087 PMCID: PMC7662246 DOI: 10.3390/molecules25214972] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 10/22/2020] [Accepted: 10/24/2020] [Indexed: 01/08/2023] Open
Abstract
We explore quantum chemical calculations for studying clusters of hydroxyl-functionalized cations kinetically stabilized by hydrogen bonding despite strongly repulsive electrostatic forces. In a comprehensive study, we calculate clusters of ammonium, piperidinium, pyrrolidinium, imidazolium, pyridinium, and imidazolium cations, which are prominent constituents of ionic liquids. All cations are decorated with hydroxy-alkyl chains allowing H-bond formation between ions of like charge. The cluster topologies comprise linear and cyclic clusters up to the size of hexamers. The ring structures exhibit cooperative hydrogen bonds opposing the repulsive Coulomb forces and leading to kinetic stability of the clusters. We discuss the importance of hydrogen bonding and dispersion forces for the stability of the differently sized clusters. We find the largest clusters when hydrogen bonding is maximized in cyclic topologies and dispersion interaction is properly taken into account. The kinetic stability of the clusters with short-chained cations is studied for the different types of cations ranging from hard to polarizable or exhibiting additional functional groups such as the acidic C(2)-H position in the imidazolium-based cation. Increasing the alkyl chain length, the cation effect diminishes and the kinetic stability is exclusively governed by the alkyl chain tether increasing the distance between the positively charged rings of the cations. With adding the counterion tetrafluoroborate (BF4−) to the cationic clusters, the binding energies immediately switch from strongly positive to strongly negative. In the neutral clusters, the OH functional groups of the cations can interact either with other cations or with the anions. The hexamer cluster with the cyclic H-bond motive and “released” anions is almost as stable as the hexamer built by H-bonded ion pairs exclusively, which is in accord with recent IR spectra of similar ionic liquids detecting both types of hydrogen bonding. For the cationic and neutral clusters, we discuss geometric and spectroscopic properties as sensitive probes of opposite- and like-charge interaction. Finally, we show that NMR proton chemical shifts and deuteron quadrupole coupling constants can be related to each other, allowing to predict properties which are not easily accessible by experiment.
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Affiliation(s)
- Jule K. Philipp
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, 18059 Rostock, Germany;
| | - Ralf Ludwig
- Institut für Chemie, Abteilung Physikalische und Theoretische Chemie, Universität Rostock, 18059 Rostock, Germany;
- Department Life, Light & Matter, Universität Rostock, Albert-Einstein-Str. 25, 18059 Rostock, Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Str. 29a, 18059 Rostock, Germany
- Correspondence: ; Tel.: +49-381-498-6517
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25
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Li H, Niemann T, Ludwig R, Atkin R. Effect of Hydrogen Bonding between Ions of Like Charge on the Boundary Layer Friction of Hydroxy-Functionalized Ionic Liquids. J Phys Chem Lett 2020; 11:3905-3910. [PMID: 32338913 DOI: 10.1021/acs.jpclett.0c00689] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Atomic force microscopy has been used to measure the lubricity of a series of ionic liquids (ILs) at mica surfaces in the boundary friction regime. A previously unreported cation bilayer structure is detected at the IL-mica interface due to the formation of H-bonds between the hydroxy-functionalized cations [(c-c) H-bonds], which enhances the ordering of the ions in the boundary layer and improves the lubrication. The strength of the cation bilayer structure is controlled by altering the strength of (c-c) H-bonding via changes in the hydroxyalkyl chain length, the cation charge polarizability, and the coordination strength of the anions. This reveals a new means of controlling IL boundary nanostructure via H-bonding between ions of the same charge, which can impact diverse applications, including surface catalysis, particle stability, electrochemistry, etc.
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Affiliation(s)
- Hua Li
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia
- Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia 6009, Australia
| | - Thomas Niemann
- Universität Rostock, Institut für Chemie, Abteilung für Physikalische Chemie, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
- Department LL&M, University of Rostock, Albert-Einstein-Strasse 25, 18059 Rostock, Germany
| | - Ralf Ludwig
- Universität Rostock, Institut für Chemie, Abteilung für Physikalische Chemie, Dr.-Lorenz-Weg 2, 18059 Rostock, Germany
- Department LL&M, University of Rostock, Albert-Einstein-Strasse 25, 18059 Rostock, Germany
- Leibniz-Institut für Katalyse an der Universität Rostock e.V., Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
| | - Rob Atkin
- School of Molecular Sciences, The University of Western Australia, Perth, Western Australia 6009, Australia
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26
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Khorrami F, Kowsari MH. Tracing Local Nanostructure of the Aqueous Solutions of the Biocompatible [Cho][Gly] Ionic Liquid: Importance of Hydrogen Bond Attraction between Like-Charged Ions. J Phys Chem B 2020; 124:3770-3783. [PMID: 32275831 DOI: 10.1021/acs.jpcb.0c01796] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The neat and aqueous solutions of the cholinium glycinate ionic liquid (IL), [Cho][Gly], at different water mole fractions, xws, are studied by molecular dynamics simulations. The changes in the local nanostructure of systems with composition have been determined by calculation of various structural distribution functions. Hydrogen bond (H-bond) attractions determine the major relative orientations of the oppositely and like charged nearest neighbors. The cation-anion H-bonds mainly form between the hydrogen of the hydroxyl or methyl groups of the cation and the carboxylate oxygen of the anion. A preferred (antiparallel) arrangement between adjacent [Cho]+ cations is due to the effective H-bond between the hydroxyl oxygen and the methyl hydrogen sites that promotes the like-charge cluster formation. Adding water decreases the occurrence probability of the [Cho]+···[Gly]-···[Cho]+ bridge structure in the aqueous solutions due to the formation of the [Gly]-···HOH···[Gly]- structure via H-bonding. Observed density trend versus xw is interpreted based on an interstice model and investigating the water cluster size distribution. Finally, the effect of xw on the infrared (IR) vibrational spectra were studied and blue and red shifts were observed for the stretching and bending vibrational modes of the hydroxyl group of [Cho]+, respectively. Current findings will improve the efficient engineering design and task-specific applications of aqueous solutions of bio-ILs consist of [Cho]+ and amino acid anions.
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Affiliation(s)
- Farzad Khorrami
- Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
| | - Mohammad H Kowsari
- Department of Chemistry, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran.,Center for Research in Climate Change and Global Warming (CRCC), Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
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27
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Strate A, Neumann J, Niemann T, Stange P, Khudozhitkov AE, Stepanov AG, Paschek D, Kolokolov DI, Ludwig R. Counting cations involved in cationic clusters of hydroxy-functionalized ionic liquids by means of infrared and solid-state NMR spectroscopy. Phys Chem Chem Phys 2020; 22:6861-6867. [PMID: 32202267 DOI: 10.1039/d0cp00303d] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Sensitive probe of like-charge attraction: analyzing infrared spectra allows counting the number of cations involved in clusters of opposite (c–a) and like-charged (c–c) ions in ionic liquids. This approach is also applicable to molecular liquids.
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Affiliation(s)
- Anne Strate
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- 18059 Rostock
- Germany
| | - Jan Neumann
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- 18059 Rostock
- Germany
| | - Thomas Niemann
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- 18059 Rostock
- Germany
| | - Peter Stange
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- 18059 Rostock
- Germany
| | - Alexander E. Khudozhitkov
- Boreskov Institute of Catalysis
- Siberian Branch of Russian Academy of Sciences
- Novosibirsk 630090
- Russia
- Novosibirsk State University
| | - Alexander G. Stepanov
- Boreskov Institute of Catalysis
- Siberian Branch of Russian Academy of Sciences
- Novosibirsk 630090
- Russia
- Novosibirsk State University
| | - Dietmar Paschek
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- 18059 Rostock
- Germany
| | - Daniil I. Kolokolov
- Boreskov Institute of Catalysis
- Siberian Branch of Russian Academy of Sciences
- Novosibirsk 630090
- Russia
- Novosibirsk State University
| | - Ralf Ludwig
- Universität Rostock
- Institut für Chemie
- Abteilung für Physikalische Chemie
- 18059 Rostock
- Germany
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