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R de Moraes B, Paschoal VH, Keppeler N, El Seoud OA, Ando RA. The Coiling Effect in Ether Ionic Liquids: Exploiting Acetate as a Probe for Transport Properties and Microenvironment Analysis. J Phys Chem B 2024. [PMID: 38608137 DOI: 10.1021/acs.jpcb.3c08162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/14/2024]
Abstract
The inherently high viscosity of ionic liquids (ILs) can limit their potential applications. One approach to address this drawback is to modify the cation side chain with ether groups. Herein, we assessed the structure-property relationship by focusing on acetate (OAc), a strongly coordinating anion, with 1,3-dialkylimidazolium cations with different side chains, including alkyl, ether, and hydroxyl functionalized, as well as their combinations. We evaluated their viscosity, thermal stabilities, and microstructure using Raman and infrared (IR) spectroscopies, allied to density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. The viscosity data showed that the ether insertion significantly enhances the fluidity of the ILs, consistent with the coiling effect of the cation chain. Through a combined experimental and theoretical approach, we analyzed how the OAc anion interacts with ether ILs, revealing a characteristic bidentate coordination, particularly in hydroxyl functionalized ILs due to specific hydrogen bonding with the OH group. IR spectroscopy showed subtle shifts in the acidic hydrogens of imidazolium ring C(2)-H and C(4,5)-H, suggesting weaker interactions between OAc and the imidazolium ring in ether-functionalized ILs. Additionally, spatial distribution functions (SDF) and dihedral angle distribution obtained via AIMD confirmed the intramolecular hydrogen bonding due to the coiling effect of the ether side chain.
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Affiliation(s)
- Beatriz R de Moraes
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Vitor H Paschoal
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Nicolas Keppeler
- Grupo de polímero e surfactantes, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Omar A El Seoud
- Grupo de polímero e surfactantes, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
| | - Rômulo A Ando
- Laboratório de Espectroscopia Molecular, Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, São Paulo 05508-900, Brazil
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2
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Rauber D, Philippi F, Schroeder D, Morgenstern B, White AJP, Jochum M, Welton T, Kay CWM. Room temperature ionic liquids with two symmetric ions. Chem Sci 2023; 14:10340-10346. [PMID: 37772103 PMCID: PMC10530934 DOI: 10.1039/d3sc03240j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Accepted: 08/31/2023] [Indexed: 09/30/2023] Open
Abstract
Room temperature ionic liquids typically contain asymmetric organic cations. The asymmetry is thought to enhance disorder, thereby providing an entropic counter-balance to the strong, enthalpic, ionic interactions, and leading, therefore, to lower melting points. Unfortunately, the synthesis and purification of such asymmetric cations is typically more demanding. Here we introduce novel room temperature ionic liquids in which both cation and anion are formally symmetric. The chemical basis for this unprecedented behaviour is the incorporation of ether-containing side chains - which increase the configurational entropy - in the cation. Molecular dynamics simulations indicate that the ether-containing side chains transiently sample curled configurations. Our results contradict the long-standing paradigm that at least one asymmetric ion is required for ionic liquids to be molten at room temperature, and hence open up new and simpler design pathways for these remarkable materials.
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Affiliation(s)
- Daniel Rauber
- Department of Chemistry, Saarland University Campus B 2.2 66123 Saarbrücken Germany
| | - Frederik Philippi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus London W12 0BZ UK
| | - Daniel Schroeder
- Department of Chemistry, Saarland University Campus B 2.2 66123 Saarbrücken Germany
| | - Bernd Morgenstern
- Department of Chemistry, Saarland University Campus B 2.2 66123 Saarbrücken Germany
| | - Andrew J P White
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus London W12 0BZ UK
| | - Marlon Jochum
- INM-Leibniz Institute for New Materials Campus D2.2 66123 Saarbrücken Germany
| | - Tom Welton
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus London W12 0BZ UK
| | - Christopher W M Kay
- Department of Chemistry, Saarland University Campus B 2.2 66123 Saarbrücken Germany
- London Centre for Nanotechnology, University College London 17-19 Gordon Street London WC1H 0AH UK
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3
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Rauber D, Philippi F, Becker J, Zapp J, Morgenstern B, Kuttich B, Kraus T, Hempelmann R, Hunt P, Welton T, Kay CWM. Anion and ether group influence in protic guanidinium ionic liquids. Phys Chem Chem Phys 2023; 25:6436-6453. [PMID: 36779955 DOI: 10.1039/d2cp05724g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ionic liquids are attractive liquid materials for many advanced applications. For targeted design, in-depth knowledge about their structure-property-relations is urgently needed. We prepared a set of novel protic ionic liquids (PILs) with a guanidinium cation with either an ether or alkyl side chain and different anions. While being a promising cation class, the available data is insufficient to guide design. We measured thermal and transport properties, nuclear magnetic resonance (NMR) spectra as well as liquid and crystalline structures supported by ab initio computations and were able to obtain a detailed insight into the influence of the anion and the ether substitution on the physical and spectroscopic properties. For the PILs, hydrogen bonding is the main interaction between cation and anion and the H-bond strength is inversely related to the proton affinity of the constituting acid and correlated to the increase of 1H and 15N chemical shifts. Using anions from acids with lower proton affinity leads to proton localization on the cation as evident from NMR spectra and self-diffusion coefficients. In contrast, proton exchange was evident in ionic liquids with triflate and trifluoroacetate anions. Using imide-type anions and ether side groups decreases glass transitions as well as fragility, and accelerated dynamics significantly. In case of the ether guanidinium ionic liquids, the conformation of the side chain adopts a curled structure as the result of dispersion interactions, while the alkyl chains prefer a linear arrangement.
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Affiliation(s)
- Daniel Rauber
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany.
| | - Frederik Philippi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK
| | - Julian Becker
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK
| | - Josef Zapp
- Pharmaceutical Biology, Saarland University, Campus B 2.3, 66123 Saarbrücken, Germany
| | - Bernd Morgenstern
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany.
| | - Björn Kuttich
- INM-Leibniz Institute for New Materials, Campus D2.2, 66123 Saarbrücken, Germany
| | - Tobias Kraus
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany. .,INM-Leibniz Institute for New Materials, Campus D2.2, 66123 Saarbrücken, Germany
| | - Rolf Hempelmann
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany.
| | - Patricia Hunt
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK.,School of Chemical and Physical Sciences, Victoria University of Wellington, New Zealand
| | - Tom Welton
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK
| | - Christopher W M Kay
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany. .,London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK.
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4
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Kurchavov D, Rustambek U, Haddad M, Ottochian A, Lefèvre G, Ciofini I, Lair V, Volovitch P. Influence of PEG-containing cation on molecular state of water in water – Acetate based ionic liquids mixtures. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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YAMADA H, MATSUMOTO K, KURATANI K, ARIYOSHI K, MATSUI M, MIZUHATA M. Preface for the 66th Special Feature “Novel Aspects and Approaches to Experimental Methods for Electrochemistry”. ELECTROCHEMISTRY 2022. [DOI: 10.5796/electrochemistry.22-66113] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Hirohisa YAMADA
- Department of Chemical Engineering, National Institute of Technology, Nara College
| | | | - Kentaro KURATANI
- Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Kingo ARIYOSHI
- Graduate School of Engineering, Osaka Metropolitan University
| | | | - Minoru MIZUHATA
- Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University
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6
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Yoon H, Shin S, Park S, Shin MW. Low-viscosity quaternary ammonium-based ionic liquid electrolytes for lithium air batteries. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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7
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Insight into the solute-solvent interactions by physicochemical and excess properties in binary systems of the ether- and allyl-based functionalized ionic liquids with acetonitrile. J Taiwan Inst Chem Eng 2022. [DOI: 10.1016/j.jtice.2022.104275] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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8
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Li X, Ning F, Luo L, Wu J, Xiang Y, Wu X, Xiong L, Peng X. Initiating a high-temperature zinc ion battery through a triazolium-based ionic liquid. RSC Adv 2022; 12:8394-8403. [PMID: 35424792 PMCID: PMC8984945 DOI: 10.1039/d2ra00298a] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/02/2022] [Indexed: 01/03/2023] Open
Abstract
Triazolium-based ionic liquids (T1, T2 and T3) with or without terminal hydroxyl groups were prepared via Cu(i) catalysed azide-alkyne click chemistry and their properties were investigated using various technologies. The hydroxyl groups obviously affected their physicochemical properties, where with a decrease in the number of hydroxyl groups, their stability and conductivity were enhanced. T1, T2 and T3 showed relatively high thermal stability, and their electrochemical stability windows (ESWs) were 4.76, 4.11 and 3.52 V, respectively. T1S-20 was obtained via the addition of zinc trifluoromethanesulfonic acid (Zn(CF3SO3)2) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to T1, displaying conductivity and ESW values of 1.55 × 10-3 S cm-1 and 6.36 V at 30 °C, respectively. Subsequently, a Zn/Li3V2(PO4)3 battery was assembled using T1S-20 as the electrolyte and its performances at 30 °C and 80 °C were investigated. The battery showed a capacity of 81 mA h g-1 at 30 °C, and its capacity retention rate was 89% after 50 cycles. After increasing the temperature to 80 °C, its initial capacity increased to 111 mA h g-1 with a capacity retention rate of 93.6% after 100 cycles, which was much higher than that of the aqueous electrolyte (WS-20)-based zinc ion battery (71.8%). Simultaneously, the T1S-20 electrolyte-based battery exhibited a good charge/discharge efficiency, and its Coulomb efficiency was 99%. Consequently, the T1S-20 electrolyte displayed a better performance in the Zn/Li3V2(PO4)3 battery than that with the aqueous electrolyte, especially at high temperature.
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Affiliation(s)
- Xun Li
- College of Physics and Electromechanical Engineering, Jishou University Jishou 416000 China
| | - Fawen Ning
- College of Chemistry and Chemical Engineering, Jishou University Jishou 416000 China
| | - Lin Luo
- College of Chemistry and Chemical Engineering, Jishou University Jishou 416000 China
| | - Jianhua Wu
- College of Physics and Electromechanical Engineering, Jishou University Jishou 416000 China
| | - Yanhong Xiang
- College of Physics and Electromechanical Engineering, Jishou University Jishou 416000 China
| | - Xianwen Wu
- College of Chemistry and Chemical Engineering, Jishou University Jishou 416000 China
| | - Lizhi Xiong
- College of Pharmacy, Jishou University Jishou 416000 China
| | - Xiaochun Peng
- College of Chemistry and Chemical Engineering, Jishou University Jishou 416000 China
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9
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Shimizu M, Sugiyama Y, Horita M, Yoshii K, Arai S. Cation‐Structure Effects on Zinc Electrodeposition and Crystallographic Orientation in Ionic Liquids. ChemElectroChem 2022. [DOI: 10.1002/celc.202200016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Masahiro Shimizu
- Shinshu University Graduate School of Engineering Faculty of Engineering: Shinshu Daigaku Materials Chemistry 4-17-1 Wakasato, Nagano 380-8553 Nagano JAPAN
| | - Yusuke Sugiyama
- Shinshu University Graduate School of Engineering Faculty of Engineering: Shinshu Daigaku Materials Chemistry JAPAN
| | - Masaomi Horita
- Shinshu University Graduate School of Engineering Faculty of Engineering: Shinshu Daigaku Technical division JAPAN
| | - Kazuki Yoshii
- National Institute of Advanced Industrial Science and Technology Battery Technology Research Division: Sangyo Gijutsu Sogo Kenkyujo Denchi Gijutsu Kenkyu Bumon Energy and Environment JAPAN
| | - Susumu Arai
- Shinshu University Graduate School of Engineering Faculty of Engineering: Shinshu Daigaku Materials Chemistry JAPAN
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10
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MAEYOSHI Y, YOSHII K, SAKAEBE H. Stable Lithium Metal Plating/Stripping in a Localized High-Concentration Cyclic Carbonate-Based Electrolyte. ELECTROCHEMISTRY 2022. [DOI: 10.5796/electrochemistry.22-00014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Yuta MAEYOSHI
- Research Institute of Electrochemical Energy, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Kazuki YOSHII
- Research Institute of Electrochemical Energy, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST)
| | - Hikari SAKAEBE
- Research Institute of Electrochemical Energy, Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST)
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11
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YOSHII K. Electrodeposition of Metals and Preparation of Metal Nanoparticles in Nonaqueous Electrolytes and Their Application to Energy Devices. ELECTROCHEMISTRY 2021. [DOI: 10.5796/electrochemistry.21-00078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Kazuki YOSHII
- Research Institute of Electrochemical Energy (RIECEN), Department of Energy and Environment, National Institute of Advanced Industrial Science and Technology (AIST)
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12
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Rauber D, Philippi F, Kuttich B, Becker J, Kraus T, Hunt P, Welton T, Hempelmann R, Kay CWM. Curled cation structures accelerate the dynamics of ionic liquids. Phys Chem Chem Phys 2021; 23:21042-21064. [PMID: 34522943 DOI: 10.1039/d1cp02889h] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids are modern liquid materials with potential and actual implementation in many advanced technologies. They combine many favourable and modifiable properties but have a major inherent drawback compared to molecular liquids - slower dynamics. In previous studies we found that the dynamics of ionic liquids are significantly accelerated by the introduction of multiple ether side chains into the cations. However, the origin of the improved transport properties, whether as a result of the altered cation conformation or due to the absence of nanostructuring within the liquid as a result of the higher polarity of the ether chains, remained to be clarified. Therefore, we prepared two novel sets of methylammonium based ionic liquids; one set with three ether substituents and another set with three butyl side chains, in order to compare their dynamic properties and liquid structures. Using a range of anions, we show that the dynamics of the ether-substituted cations are systematically and distinctly accelerated. Liquefaction temperatures are lowered and fragilities increased, while at the same time cation-anion distances are slightly larger for the alkylated samples. Furthermore, pronounced liquid nanostructures were not observed. Molecular dynamics simulations demonstrate that the origin of the altered properties of the ether substituted ionic liquids is primarily due to a curled ether chain conformation, in contrast to the alkylated cations where the alkyl chains retain a linear conformation. Thus, the observed structure-property relations can be explained by changes in the geometric shape of the cations, rather than by the absence of a liquid nanostructure. Application of quantum chemical calculations to a simplified model system revealed that intramolecular hydrogen-bonding is responsible for approximately half of the stabilisation of the curled ether-cations, whereas the other half stems from non-specific long-range interactions. These findings give more detailed insights into the structure-property relations of ionic liquids and will guide the development of ionic liquids that do not suffer from slow dynamics.
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Affiliation(s)
- Daniel Rauber
- Department of Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany.
| | - Frederik Philippi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK
| | - Björn Kuttich
- INM-Leibniz Institute for New Materials, Campus D2.2, 66123, Saarbrücken, Germany
| | - Julian Becker
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK
| | - Tobias Kraus
- Department of Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany. .,INM-Leibniz Institute for New Materials, Campus D2.2, 66123, Saarbrücken, Germany
| | - Patricia Hunt
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK.,School of Chemical and Physical Sciences, Victoria University of Wellington, New Zealand
| | - Tom Welton
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, White City Campus, London W12 0BZ, UK
| | - Rolf Hempelmann
- Department of Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany.
| | - Christopher W M Kay
- Department of Chemistry, Saarland University, Campus B2.2, 66123, Saarbrücken, Germany. .,London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK.
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Yoshii K, Uto T, Onishi T, Kosuga D, Tachikawa N, Katayama Y. Ether-Functionalized Pyrrolidinium-Based Room Temperature Ionic Liquids: Physicochemical Properties, Molecular Dynamics, and the Lithium Ion Coordination Environment. Chemphyschem 2021; 22:1584-1594. [PMID: 34129270 DOI: 10.1002/cphc.202100380] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/14/2021] [Indexed: 11/09/2022]
Abstract
The physicochemical properties of room temperature ionic liquids (RTILs) consisting of bis(trifluoromethanesulfonyl)amide (TFSA- ) combined with 1-hexyl-1-methylpyrrolidinium (Pyr1,6 + ), 1-(butoxymethyl)-1-methylpyrrolidinium (Pyr1,1O4 + ), 1-(4-methoxybutyl)-1-methyl pyrrolidinium (Pyr1,4O1 + ), and 1-((2-methoxyethoxy)methyl)-1-methylpyrrolidinium (Pyr1,1O2O1 + ) were investigated using both experimental and computational approaches. Pyr1,1O2O1 TFSA, which contains two ether oxygen atoms, showed the lowest viscosity, and the relationship between its physicochemical properties and the position and number of the ether oxygen atoms was discussed by a careful comparison with Pyr1,1O4 TFSA and Pyr1,4O1 TFSA. Ab initio calculations revealed the conformational flexibility of the side chain containing the ether oxygen atoms. In addition, molecular dynamics (MD) calculations suggested that the ion distributions have a significant impact on the transport properties. Furthermore, the coordination environments of the Li ions in the RTILs were evaluated using Raman spectroscopy, which was supported by MD calculations using 1000 ion pairs. The presented results will be valuable for the design of functionalized RTILs for various applications.
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Affiliation(s)
- Kazuki Yoshii
- Department of Energy and Environment, Research Institute of Electrochemical Energy (REICEN), National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka, 563-8577, Japan.,Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, 223-8522, Japan
| | - Takuya Uto
- Organization for Promotion of Tenure Track, University of Miyazaki, Nishi 1-1 Gakuen-Kibanadai, Miyazaki, 889-2192, Japan
| | - Takakazu Onishi
- Graduate School of Engineering, University of Miyazaki, Nishi 1-1 Gakuen-Kibanadai, Miyazaki, 889-2192, Japan
| | - Daichi Kosuga
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, 223-8522, Japan
| | - Naoki Tachikawa
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, 223-8522, Japan
| | - Yasushi Katayama
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa, 223-8522, Japan
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14
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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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15
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Philippi F, Rauber D, Kuttich B, Kraus T, Kay CWM, Hempelmann R, Hunt PA, Welton T. Ether functionalisation, ion conformation and the optimisation of macroscopic properties in ionic liquids. Phys Chem Chem Phys 2020; 22:23038-23056. [PMID: 33047758 DOI: 10.1039/d0cp03751f] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Ionic liquids are an attractive material class due to their wide liquid range, intrinsic ionic conductivity, and high chemical as well as electrochemical stability. However, the widespread use of ionic liquids is hindered by significantly higher viscosities compared to conventional molecular solvents. In this work, we show how the transport properties of ionic liquids can be altered significantly, even for isostructural ions that have the same backbone. To this end, structure-property relationships have been determined for a set of 16 systematically varied representative ionic liquids. Variations in molecular structure include ammonium vs. phosphonium, ether vs. alkyl side chains, and rigid vs. flexible anions. Ab initio calculations are used to relate molecular structures to the thermal, structural and transport properties of the ionic liquids. We find that the differences in properties of ether and alkyl functionalised ionic liquids are primarily dependent on minimum energy geometries, with the conformational flexibility of ether side chains appearing to be of secondary importance. We also show unprecedented correlations between anion conformational flexibility and transport properties. Critically, increasing fluidity upon consecutive introduction of ether side chains and phosphonium centres into the cation is found to be dependent on whether the anion is flexible or rigid. We demonstrate that targeted design of functional groups based on structure-property relationships can yield ionic liquids of exceptionally high fluidity.
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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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