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Watanabe M. Advances in Organic Ionic Materials Based on Ionic Liquids and Polymers. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2021. [DOI: 10.1246/bcsj.20210281] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Masayoshi Watanabe
- Advanced Chemical Energy Research Center, Institute of Advanced Sciences, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama, Kanagawa 240-8501, Japan
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Watanabe H, Arai N, Kameda Y, Buchner R, Umebayashi Y. Effect of Brønsted Acidity on Ion Conduction in Fluorinated Acetic Acid and N-Methylimidazole Equimolar Mixtures as Pseudo-protic Ionic Liquids. J Phys Chem B 2020; 124:11157-11164. [PMID: 33198463 DOI: 10.1021/acs.jpcb.0c07706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To clarify proton conduction mechanism in protic ionic liquids (PILs) and pseudo-PILs (pPILs), equimolar mixtures of N-methylimidazole (C1Im) with fluorinated acetic acids were investigated by Raman spectroscopy, X-ray scattering, and dielectric relaxation spectroscopy (DRS). Only the ionic species exist in the equimolar mixture of C1Im and HTFA (HTFA: trifluoroacetic acid). On the other hand, the equimolar mixture of C1Im and HDFA (HDFA: difluoroacetic acid) consists of both ionic and electrically neutral species. In particular, not only the electrostatic but also van der Waals interactions with the F atoms were observed in the liquid structures of both [C1hIm+][TFA-] and [C1hIm+][DFA-]. The concept for proton conduction mechanism that we have proposed in previous study was revisited; the proton conduction mechanism could be classified with two linear free energy relationship lines for proton exchange reaction and translation/rotation of proton carriers. Our results exhibit that the proton conduction mechanism changes from proton hopping to vehicle mechanism with increasing acidity of an acid HA in PILs.
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Affiliation(s)
- Hikari Watanabe
- Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
| | - Nana Arai
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
| | - Yasuo Kameda
- Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Yamagata 990-8560, Japan
| | - Richard Buchner
- Institute of Physical and Theoretical Chemistry, University of Regensburg, Universitätsstr. 31, Regensburg 93053, Germany
| | - Yasuhiro Umebayashi
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan
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Abe H, Koyama Y, Kishimura H, Matsuishi K. High-pressure crystal polymorph of the protic ionic liquid: Ethylammonium nitrate. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.113959] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Gao F, Ji P, Cheng JP. Unexpected Strong Acidity Enhancing the Effect in Protic Ionic Liquids Quantified by Equilibrium Acidity Studies: A Crucial Role of Cation Structures on Dictating the Solvation Properties. J Org Chem 2020; 85:3041-3049. [PMID: 32027506 DOI: 10.1021/acs.joc.9b02946] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The equilibrium acidities for several series of structural and electronic different organic acids were measured in 3-pyrrolidinium-based aprotic and protic ionic liquid (IL) analogues, that is, [Bmpy][NTf2], [BpyH][NTf2], and [PyH2][NTf2], by the UV-Vis method. The acidities of neutral acids are found to be much stronger in the protic ILs (PILs) than aprotic ILs (AILs), and the acidifying effect in the two PILs roughly increases proportionally to the number of protons in the cation of the PIL. On the other hand, interestingly, the cationic N+-H acids exhibit similar acidities in [Bmpy][NTf2] and [BpyH][NTf2] but much weaker than those in [PyH2][NTf2]. The Hammett ρ values for the acidic dissociation of para-substituted benzoic acids in two PILs are about the same as that in water (1.00) but significantly smaller than that in the AIL [Bmpy][NTf2] (2.66). The correlations between the acidities in the PILs and water show double-linear relationships with different slopes and intercepts for the neutral and cationic acids. These, together with previous observations in the PILs [DBUH][OTf] (DBU = 1,5-diazabicyclo(5.4.0)-5-undecene) and EAN (ethylammonium nitrate), clearly indicate that the structure of the cation plays a subtle but a crucial role on sensing the electronic nature of solutes and strongly affects the solvation behaviors of PILs.
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Affiliation(s)
- Feixiang Gao
- Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Pengju Ji
- Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Jin-Pei Cheng
- Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, China.,State Key Laboratory of Elemento-organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, China
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Xu J, Deng G, Wang YT, Guo HY, Kalhor P, Yu ZW. Local Acid Strength of Solutions and Its Quantitative Evaluation Using Excess Infrared Nitrile Probes. J Phys Chem Lett 2020; 11:1007-1012. [PMID: 31958952 DOI: 10.1021/acs.jpclett.9b03804] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We propose the concept of local acidity in condensed-phase chemistry in this work. The feature is demonstrated in trifluoroethanol (TFE) by employing two Fourier-transform infrared spectroscopy (FTIR) nitrile probes, acetonitrile (CH3CN) and benzonitrile (PhCN). Specifically, three positive excess peaks were found in the binary systems composed of TFE and a probe using excess spectroscopy. To characterize the local acidity quantitatively, we have tried to correlate the wavenumbers of the positive excess peaks of the probes and the pKa values in water of a series of XH-containing compounds (X = O, N, and C). Good linear relationships were discovered. Accordingly, three different pKa values of TFE were determined based on the three positive excess infrared peaks, which are attributed to the monomer, dimer, and trimer of TFE with the help of quantum-chemical calculations. The concept of local acidity and its quantitative evaluation enrich our knowledge of acid-base chemistry and will shed light on a better understanding of microstructures of solutions.
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Affiliation(s)
- Jing Xu
- MOE Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology, Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
| | - Geng Deng
- MOE Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology, Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
| | - Yu-Tian Wang
- MOE Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology, Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
| | - Hao-Yue Guo
- MOE Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology, Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
| | - Payam Kalhor
- MOE Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology, Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
| | - Zhi-Wu Yu
- MOE Key Laboratory of Bioorganic Phosphorous Chemistry and Chemical Biology, Department of Chemistry , Tsinghua University , Beijing 100084 , P. R. China
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Kanzaki R, Kodamatani H, Tomiyasu T. Proton Thermodynamics in a Protic Ionic Liquid, Ethylammonium Nitrate. Chemistry 2019; 25:13500-13503. [PMID: 31454440 DOI: 10.1002/chem.201903485] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Indexed: 11/11/2022]
Abstract
In order to investigate the proton solvation state in protic ionic liquids (PILs), ten acid dissociation enthalpies and entropies of eight compounds were determined in ethylammonium nitrate (EAN). Regardless of the nature of the compound, 24 kJ mol-1 larger enthalpy and 65 J mol-1 K-1 larger entropy than those in water, respectively, were observed. These values were reasonably explained by the differences in the proton solvation structure in EAN and water. Namely, protons in EAN exist as HNO3 , having a higher reaction energy than that of H3 O+ in water, undergo entropic stabilization as a result of the less-structured solvation. As such, the entropic effect of the proton solvation structure on the acid-base property is possibly applicable to all PILs. In addition, based on these proton thermodynamics, enthalpy and entropy windows were proposed as a novel perspective for the characterization of solvents. Use of this concept enabled the visualization of similarities and differences between EAN and water.
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Affiliation(s)
- Ryo Kanzaki
- Graduate School of Science and Engineering, Kagoshima University, 1-21-35, Korimoto, Kagoshima, 890-0065, Japan
| | - Hitoshi Kodamatani
- Graduate School of Science and Engineering, Kagoshima University, 1-21-35, Korimoto, Kagoshima, 890-0065, Japan
| | - Takashi Tomiyasu
- Graduate School of Science and Engineering, Kagoshima University, 1-21-35, Korimoto, Kagoshima, 890-0065, Japan
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Non-equilibrium protic and aprotic ionic liquids: Measuring the distance from the equilibrium state. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Gao F, Wang Z, Ji P, Cheng JP. CO 2 Absorption by DBU-Based Protic Ionic Liquids: Basicity of Anion Dictates the Absorption Capacity and Mechanism. Front Chem 2019; 6:658. [PMID: 30705879 PMCID: PMC6344442 DOI: 10.3389/fchem.2018.00658] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/18/2018] [Indexed: 12/16/2022] Open
Abstract
PILs are promising solvent systems for CO2 absorption and transformations. Although previously tremendous work has been paid to synthesize functionalized PILs to achieve a high-performance absorption, the underlying mechanisms are far less investigated and still not clear. In this work, a series of DBU-based PILs, i.e., [DBUH][X], with anions of various basicities were synthesized. The basicities of the anions were accurately measured in [DBUH][OTf] or extrapolated from the known linear correlations. The apparent kinetics as well as the capacities for CO2 absorption in these PILs were studied systematically. The results show that the absorption rate and capacity in [DBUH][X] are in proportional to the basicity of PIL, i.e., a more basic PIL leads to a faster absorption rate and a higher absorption capacity. In addition, the spectroscopic evidences and correlation analysis indicate that the capacity and mechanism of CO2 absorption in [DBUH][X] are essentially dictated by the basicities of anions of these PILs.
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Affiliation(s)
- Feixiang Gao
- Department of Chemistry, Center of Basic Molecular Science, Tsinghua University, Beijing, China
| | - Zhen Wang
- School of Chemical and Environmental Engineering, Anyang Institute of Technology, Anyang, China
| | - Pengju Ji
- Department of Chemistry, Center of Basic Molecular Science, Tsinghua University, Beijing, China
| | - Jin-Pei Cheng
- Department of Chemistry, Center of Basic Molecular Science, Tsinghua University, Beijing, China.,State Key Laboratory of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering, Nankai University, Tianjin, China
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Miran MS, Hoque M, Yasuda T, Tsuzuki S, Ueno K, Watanabe M. Key factor governing the physicochemical properties and extent of proton transfer in protic ionic liquids: ΔpKa or chemical structure? Phys Chem Chem Phys 2019; 21:418-426. [DOI: 10.1039/c8cp06973e] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A series of protic ionic liquids (PILs) are prepared by neutralisation of bis(trifluoromethanesulfonyl)amide acid (H[NTf2]) with various amines, and the properties (especially thermal stability and ionicity) are compared with those of PILs from 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) and various acids.
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Affiliation(s)
- Muhammed Shah Miran
- Department of Chemistry and Biotechnology
- Yokohama National University
- Yokohama 240-8501
- Japan
| | - Mahfuzul Hoque
- Department of Chemistry and Biotechnology
- Yokohama National University
- Yokohama 240-8501
- Japan
| | - Tomohiro Yasuda
- Department of Chemistry and Biotechnology
- Yokohama National University
- Yokohama 240-8501
- Japan
| | - Seiji Tsuzuki
- Research Centre for Computational Design of Advanced Functional Materials (CD-FMat)
- National Institute of Advanced Industrial Science and Technology (AIST)
- Tsukuba
- Japan
| | - Kazuhide Ueno
- Department of Chemistry and Biotechnology
- Yokohama National University
- Yokohama 240-8501
- Japan
| | - Masayoshi Watanabe
- Department of Chemistry and Biotechnology
- Yokohama National University
- Yokohama 240-8501
- Japan
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Kanzaki R, Daiba H, Kodamatani H, Tomiyasu T. Validation of pH Standards and Estimation of the Activity Coefficients of Hydrogen and Chloride Ions in an Ionic Liquid, Ethylammonium Nitrate. J Phys Chem B 2018; 122:10593-10599. [PMID: 30351941 DOI: 10.1021/acs.jpcb.8b08870] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We selected and validated the pH values of three standard materials that function in the protic ionic liquid, ethylammonium nitrate (EAN). The pH values of 0.05 mol kg-1 phthalate, oxalate, and phosphate buffers were 4.93 (0.04), 2.12 (0.04), and 7.13 (0.06), respectively (the values in the parentheses denote the standard deviation). Because the pH of EAN ranges from 0 to 10, with a neutral pH of 5, these materials are usable as acidic, basic, or neutral standards. The standard electrode potential of silver-silver chloride in EAN was 127.2 (1.7) mV. The activity coefficients of hydrogen and chloride ions remain equal to unity in EAN of a wide concentration range, which indicates that the effective ionic strength is independent of the solute ion concentration. In addition, the estimated value of the transfer activity coefficient of chloride ion suggests a weaker solvation in EAN compared with water in spite of a ubiquitous cation (C2H5NH3+). These behaviors of ions in EAN can be explained by the unique solvation in the ionic liquid through direct ion-ion electrostatic interactions.
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Affiliation(s)
- Ryo Kanzaki
- Department of Earth and Environmental Sciences, Graduate School of Science and Engineering , Kagoshima University , Korimoto, Kagoshima 890-0065 , Japan
| | - Hikaru Daiba
- Department of Earth and Environmental Sciences, Graduate School of Science and Engineering , Kagoshima University , Korimoto, Kagoshima 890-0065 , Japan
| | - Hitoshi Kodamatani
- Department of Earth and Environmental Sciences, Graduate School of Science and Engineering , Kagoshima University , Korimoto, Kagoshima 890-0065 , Japan
| | - Takashi Tomiyasu
- Department of Earth and Environmental Sciences, Graduate School of Science and Engineering , Kagoshima University , Korimoto, Kagoshima 890-0065 , Japan
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Abe H, Takekiyo T, Yoshimura Y, Shimizu A, Ozawa S. Multiple crystal pathways and crystal polymorphs in protic ionic liquids. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.08.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Ingenmey J, Gehrke S, Kirchner B. How to Harvest Grotthuss Diffusion in Protic Ionic Liquid Electrolyte Systems. CHEMSUSCHEM 2018; 11:1900-1910. [PMID: 29742320 DOI: 10.1002/cssc.201800436] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Indexed: 06/08/2023]
Abstract
Hydrogen is often regarded as fuel of the future, and there is an increasing demand for the development of anhydrous proton-conducting electrolytes to enable fuel-cell operation at elevated temperatures exceeding 120 °C. Much attention has been directed at protic ionic liquids as promising candidates, but in the search for highly conductive systems the possibility of designing Grotthuss diffusion-enabled protic ionic liquids has been widely overlooked. Herein, the mechanics of proton-transfer mechanism in the equimolar mixture of N-methylimidazole and acetic acid was explored using ab initio molecular dynamics simulations. The ionicity of the system is approximated with good agreement to experiments. This system consists mostly of neutral species but exhibits a high ionic conductivity through Grotthuss-like proton conduction. Chains of acetic-acid molecules and other species participating in the proton-transfer mechanisms resembling Grotthuss diffusion could be directly observed. Furthermore, based on these findings, a series of static quantum chemical calculations was conducted to investigate the effect of substituting the anion and cation with different functional groups. We predict whether a given combination of cation and anion will be a true ionic liquid or a molecular mixture and propose some systems as candidates for Grotthuss diffusion-enabled protic ionic liquids.
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Affiliation(s)
- Johannes Ingenmey
- Mulliken Center for Theoretical Chemistry, Universität Bonn, Beringstr. 4, 53115, Bonn, Germany
| | - Sascha Gehrke
- Mulliken Center for Theoretical Chemistry, Universität Bonn, Beringstr. 4, 53115, Bonn, Germany
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 3436, 45470, Mülheim an der Ruhr, Germany
| | - Barbara Kirchner
- Mulliken Center for Theoretical Chemistry, Universität Bonn, Beringstr. 4, 53115, Bonn, Germany
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Yang JD, Ji P, Xue XS, Cheng JP. Recent Advances and Advisable Applications of Bond Energetics in Organic Chemistry. J Am Chem Soc 2018; 140:8611-8623. [DOI: 10.1021/jacs.8b04104] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Jin-Dong Yang
- Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Pengju Ji
- Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, China
| | - Xiao-Song Xue
- State Key Laboratory of Elemento-organic Chemistry, Collaborative Innovation Centre of Chemical Science and Engineering, College of Chemistry, Nankai University, Tianjin 300071, China
| | - Jin-Pei Cheng
- Center of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, China
- State Key Laboratory of Elemento-organic Chemistry, Collaborative Innovation Centre of Chemical Science and Engineering, College of Chemistry, Nankai University, Tianjin 300071, China
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Bentley CL, Bond AM, Zhang J. Voltammetric Perspectives on the Acidity Scale and H +/H 2 Process in Ionic Liquid Media. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2018; 11:397-419. [PMID: 29553798 DOI: 10.1146/annurev-anchem-061417-010022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Nonhaloaluminate ionic liquids (ILs) have received considerable attention as alternatives to molecular solvents in diverse applications spanning the fields of physical, chemical, and biological science. One important and often overlooked aspect of the implementation of these designer solvents is how the properties of the IL formulation affect (electro)chemical reactivity. This aspect is emphasized herein, where recent (voltammetric) studies on the energetics of proton (H+) transfer and electrode reaction mechanisms of the H+/H2 process in IL media are highlighted and discussed. The energetics of proton transfer, quantified using the p Ka (minus logarithm of acidity equilibrium constant, Ka) formalism, is strongly governed by the constituent IL anion, and to a lesser extent, the IL cation. The H+/H2 process, a model inner-sphere reaction, also displays electrochemical characteristics that are strongly IL-dependent. Overall, these studies highlight the need to carry out systematic investigations to resolve IL structure and function relationships in order to realize the potential of these diverse and versatile solvents.
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Affiliation(s)
- Cameron L Bentley
- Department of Chemistry, University of Warwick, Coventry CV4 7AL, United Kingdom;
| | - Alan M Bond
- School of Chemistry and Australian Research Council Centre of Excellence for Electromaterials Science, Monash University, Clayton, Victoria 3800, Australia; ,
| | - Jie Zhang
- School of Chemistry and Australian Research Council Centre of Excellence for Electromaterials Science, Monash University, Clayton, Victoria 3800, Australia; ,
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Kanzaki R, Guibert C, Fresnais J, Peyre V. Dispersion mechanism of polyacrylic acid-coated nanoparticle in protic ionic liquid, N,N-diethylethanolammonium trifluoromethanesulfonate. J Colloid Interface Sci 2018; 516:248-253. [DOI: 10.1016/j.jcis.2018.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/30/2017] [Accepted: 01/02/2018] [Indexed: 11/29/2022]
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Himmel D, Radtke V, Butschke B, Krossing I. Grundlegende Bemerkungen zur Azidität. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201709057] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Daniel Himmel
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
| | - Valentin Radtke
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
| | - Burkhard Butschke
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie, und Freiburger Materialforschungszentrum (FMF); Universität Freiburg; Albertstraße 21 79104 Freiburg Deutschland
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Himmel D, Radtke V, Butschke B, Krossing I. Basic Remarks on Acidity. Angew Chem Int Ed Engl 2018; 57:4386-4411. [PMID: 29171707 DOI: 10.1002/anie.201709057] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/16/2017] [Indexed: 12/21/2022]
Abstract
This Review provides a unified view on Brønsted acidity. For this purpose, a brief overview of the concepts acidity, acid strengths, and pH value is given, including problems, proposed solutions, and the use of the pHabs /pHabsH2O scale as a unifying concept. Thereafter, some examples of the accessibility and application of unified pHabs values are given. The Review is rounded off with the analogy of acid-base chemistry to redox chemistry with the introduction of the unified redox scale peabs . The combination of pHabs and peabs values in the protoelectric potential map (PPM), as elaborated in ongoing studies on the thermochemistry of single ions, provides a means to classify and to compare all possible acid-base/redox reactions in a medium-independent and, thus, unified fashion.
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Affiliation(s)
- Daniel Himmel
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Valentin Radtke
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Burkhard Butschke
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstrasse 21, 79104, Freiburg, Germany
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Wang Z, Gao F, Ji P, Cheng JP. Unexpected solvation-stabilisation of ions in a protic ionic liquid: insights disclosed by a bond energetic study. Chem Sci 2018; 9:3538-3543. [PMID: 29780485 PMCID: PMC5934747 DOI: 10.1039/c7sc05227h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Accepted: 03/05/2018] [Indexed: 11/21/2022] Open
Abstract
Equilibrium acidities (pKas) of 42 organic acids were precisely determined in protic ionic liquid (PIL) [DBUH][OTf]. Surprisingly, the often seen homoassociation complication during the pKa measurement of O-H acids in DMSO was not detected in [DBUH][OTf], implying that the incipient oxanion should be better solvation-stabilized by the PIL, although its "apparent" dielectric constant is much lower than that of the conventional molecular solvent DMSO. Evidence showing that the solute ions in the PIL are also free from other specific ion associations like ion-pairing is further demonstrated by the identical pKas of protic amine salts bearing largely different counter-anions. Correlations between the RO-H, N-H, N+-H and RCOO-H bond acidities in [DBUH][OTf] and in water revealed different slopes and intercepts for each individual series, suggesting far superior properties of the DBUH+-based PIL for differentiating the solvation effect of various species in structural analysis to the well applied EAN that is known for leveling out differential solvation.
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Affiliation(s)
- Zhen Wang
- Centre of Basic Molecular Science (CBMS) , Department of Chemistry , Tsinghua University , Beijing , 100084 , China . ; .,School of Chemical and Environmental Engineering , Anyang Institute of Technology , Anyang 455000 , China
| | - Feixiang Gao
- Centre of Basic Molecular Science (CBMS) , Department of Chemistry , Tsinghua University , Beijing , 100084 , China . ;
| | - Pengju Ji
- Centre of Basic Molecular Science (CBMS) , Department of Chemistry , Tsinghua University , Beijing , 100084 , China . ;
| | - Jin-Pei Cheng
- Centre of Basic Molecular Science (CBMS) , Department of Chemistry , Tsinghua University , Beijing , 100084 , China . ; .,State Key Laboratory of Elemento-Organic Chemistry , Collaborative Innovation Centre of Chemical Science and Engineering , Nankai University , Tianjin , 300071 , China
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Reid JESJ, Bernardes CES, Agapito F, Martins F, Shimizu S, Minas da Piedade ME, Walker AJ. Structure-property relationships in protic ionic liquids: a study of solvent-solvent and solvent-solute interactions. Phys Chem Chem Phys 2018; 19:28133-28138. [PMID: 29022017 DOI: 10.1039/c7cp05076c] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The ionic nature of a functionalized protic ionic liquid cannot be rationalized simply through the differences in aqueous proton dissociation constants between the acid precursor and the conjugate acid of the base precursor. The extent of proton transfer, i.e. the equilibrium ionicity, of a tertiary ammonium acetate protic ionic liquid can be significantly increased by introducing an hydroxyl functional group on the cation, compared to the alkyl or amino-functionalized analogues. This increase in apparent ionic nature correlates well with variations in solvent-solute and solvent-solvent interaction parameters, as well as with physicochemical properties such as viscosity.
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Affiliation(s)
- Joshua E S J Reid
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
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22
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Abbott AP, Alabdullah SSM, Al-Murshedi AYM, Ryder KS. Brønsted acidity in deep eutectic solvents and ionic liquids. Faraday Discuss 2017; 206:365-377. [PMID: 28926059 DOI: 10.1039/c7fd00153c] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Despite the importance of ionic liquids in a variety of fields, little is understood about the behaviour of protons in these media. The main difficulty arises due to the unknown activity of protons in non-aqueous solvents. This study presents acid dissociation constants for nine organic acids in deep eutectic solvents (DESs) using standard pH indicator solutes. The pKIn value for bromophenol blue was found by titrating the DES with triflic acid. The experimental method was developed to understand the acid-base properties of deep eutectic solvents, and through this study it was found that the organic acids studied were slightly less dissociated in the DES than in water with pKa values between 0.2 and 0.5 higher. pKIn values were also determined for two ionic liquids, [Bmim][BF4] and [Emim][acetate]. The anion of the ionic liquid changes the pH of the solution by acting as a buffer. [Emim][acetate] was found to be more basic than water. It is also shown that water significantly affects the pH of ionic liquids. This is thought to arise because aqueous mixtures with ionic liquids form heterogeneous solutions and the proton partitions into the aqueous phase. This study also attempted to develop an electrochemical pH sensor. It was shown that a linear response of cell potential vs. ln aH+ could be obtained but the slope for the correlation was less than that obtained in aqueous solutions. Finally it was shown that the liquid junction potential between two reference electrodes immersed in different DESs was dependent upon the pH difference between the liquids.
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Affiliation(s)
- Andrew P Abbott
- Materials Centre, Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK.
| | - Sahar S M Alabdullah
- Materials Centre, Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK.
| | - Azhar Y M Al-Murshedi
- Materials Centre, Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK.
| | - Karl S Ryder
- Materials Centre, Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK.
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23
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Hashimoto K, Fujii K, Ohara K, Shibayama M. Effect of protonation on the solvation structure of solute N-butylamine in an aprotic ionic liquid. Phys Chem Chem Phys 2017; 19:8194-8200. [DOI: 10.1039/c6cp08247e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Significant change in the solvation structure by protonation reaction in the ionic liquid [C2mIm][TFSA].
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Affiliation(s)
| | - Kenta Fujii
- Graduate School of Sciences and Technology for Innovation
- Yamaguchi University
- Yamaguchi 755-8611
- Japan
| | - Koji Ohara
- Japan Synchrotron Radiation Research Institute (JASRI)
- Sayogun Sayocho
- Japan
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24
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Reid JESJ, Agapito F, Bernardes CES, Martins F, Walker AJ, Shimizu S, Minas da Piedade ME. Structure–property relationships in protic ionic liquids: a thermochemical study. Phys Chem Chem Phys 2017; 19:19928-19936. [DOI: 10.1039/c7cp02230a] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
How does cation functionality influence the strength of intermolecular interactions in protic ionic liquids (PILs)? Quantifying the energetics of PILs can be an invaluable tool to answer this fundamental question.
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Affiliation(s)
- Joshua E. S. J. Reid
- York Structural Biology Laboratory
- Department of Chemistry
- University of York
- Heslington
- York
| | - Filipe Agapito
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | - Carlos E. S. Bernardes
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | - Filomena Martins
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
| | | | - Seishi Shimizu
- York Structural Biology Laboratory
- Department of Chemistry
- University of York
- Heslington
- York
| | - Manuel E. Minas da Piedade
- Centro de Química e Bioquímica e Departamento de Química e Bioquímica
- Faculdade de Ciências
- Universidade de Lisboa
- 1749-016 Lisboa
- Portugal
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25
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Matsubara Y, Grills DC, Koide Y. Experimental Insight into the Thermodynamics of the Dissolution of Electrolytes in Room-Temperature Ionic Liquids: From the Mass Action Law to the Absolute Standard Chemical Potential of a Proton. ACS OMEGA 2016; 1:1393-1411. [PMID: 31457204 PMCID: PMC6640753 DOI: 10.1021/acsomega.6b00129] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2016] [Accepted: 12/12/2016] [Indexed: 06/10/2023]
Abstract
Room-temperature ionic liquids (ILs) are a class of nonaqueous solvents that have expanded the realm of modern chemistry, drawing increasing interest over the last few decades, not only in terms of their own unique physical chemistry but also in many applications including organic synthesis, electrochemistry, and biological systems, wherein charged solutes (i.e., electrolytes) often play vital roles. However, our fundamental understanding of the dissolution of an electrolyte in an IL is still rather limited. For example, the activity of a charged species has frequently been assumed to be unity without a clear experimental basis. In this study, we have discussed a standard component-based scheme for the dissolution of an electrolyte in an IL, supported by our observation of ideal Nernstian responses for the reduction of silver and ferrocenium salts in a representative IL, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([emim+][NTf2 -] or [emim+][TFSI-]). Using this scheme, which was also supported by temperature-dependent measurements with ILs having longer alkyl chains in the imidazolium ring, and the solubility of the IL in water, we established the concept of Gibbs transfer energies of "pseudo-single ions" from the IL to conventional neutral molecular solvents (water, acetonitrile, and methanol). This concept, which bridges component- and constituent-based energetics, utilizes an extrathermodynamic assumption, which itself was justified by experimental observations. These energies enable us to eliminate inner potential differences between the IL and molecular solvents (solvent-solvent interactions), that is, on a practical level, conditional liquid junction potential differences, so that we can discuss ion-solvent interactions independently. Specifically, we have examined the standard electrode potential of the ferrocenium/ferrocene redox couple, Fc+/Fc, and the absolute intrinsic standard chemical potential of a proton in [emim+][NTf2 -], finding that the proton is more acidic in the IL than in water by 6.5 ± 0.6 units on the unified pH scale. These results strengthen the progress on the physical chemistry of ions in IL solvent systems on the basis of their activities, providing a rigorous thermodynamic framework.
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Affiliation(s)
- Yasuo Matsubara
- Department
of Material and Life Chemistry, Kanagawa
University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
| | - David C. Grills
- Chemistry
Division, Brookhaven National Laboratory, P.O. Box 5000, Upton, New
York 11973-5000, United
States
| | - Yoshihiro Koide
- Department
of Material and Life Chemistry, Kanagawa
University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan
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26
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Wang Z, Li X, Ji P, Cheng JP. Absolute pKas of Sulfonamides in Ionic Liquids: Comparisons to Molecular Solvents. J Org Chem 2016; 81:11195-11200. [DOI: 10.1021/acs.joc.6b02182] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Zedong Wang
- State
Key Laboratory of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, People’s Republic of China
| | - Xin Li
- State
Key Laboratory of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, People’s Republic of China
| | - Pengju Ji
- Center
of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China
| | - Jin-Pei Cheng
- State
Key Laboratory of Elemento-organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering, Nankai University, Tianjin 300071, People’s Republic of China
- Center
of Basic Molecular Science (CBMS), Department of Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China
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