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Radtke V, Priester D, Heering A, Müller C, Koslowski T, Leito I, Krossing I. The Unified Redox Scale for All Solvents: Consistency and Gibbs Transfer Energies of Electrolytes from their Constituent Single Ions. Chemistry 2023; 29:e202300609. [PMID: 37191477 DOI: 10.1002/chem.202300609] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/28/2023] [Accepted: 05/11/2023] [Indexed: 05/17/2023]
Abstract
We have devised the unified redox scale Eabs H2O , which is valid for all solvents. The necessary single ion Gibbs transfer energy between two different solvents, which only can be determined with extra-thermodynamic assumptions so far, must clearly satisfy two essential conditions: First, the sum of the independent cation and anion values must give the Gibbs transfer energy of the salt they form. The latter is an observable and measurable without extra-thermodynamic assumptions. Second, the values must be consistent for different solvent combinations. With this work, potentiometric measurements on silver ions and on chloride ions show that both conditions are fulfilled using a salt bridge filled with the ionic liquid [N2225 ][NTf2 ]: if compared to the values resulting from known pKL values, the silver and chloride single ion magnitudes combine within a uncertainty of 1.5 kJ mol-1 to the directly measurable transfer magnitudes of the salt AgCl from water to the solvents acetonitrile, propylene carbonate, dimethylformamide, ethanol, and methanol. The resulting values are used to further develop the consistent unified redox potential scale Eabs H2O that now allows to assess and compare redox potentials in and over six different solvents. We elaborate on its implications.
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Affiliation(s)
- Valentin Radtke
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Denis Priester
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Agnes Heering
- Institute of Chemistry, University of Tartu, Ravila 14a Str, 50411, Tartu, Estonia
| | - Carina Müller
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Thorsten Koslowski
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
| | - Ivo Leito
- Institute of Chemistry, University of Tartu, Ravila 14a Str, 50411, Tartu, Estonia
| | - Ingo Krossing
- Institut für Anorganische und, Analytische Chemie and Freiburger Materialforschungszentrum (FMF), Universität Freiburg, Albertstr. 21, 79104, Freiburg, Germany
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2
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Warren PB. Partial osmotic pressures of ions in electrolyte solutions and the Gibbs-Guggenheim uncertainty principle. Phys Rev E 2023; 107:034606. [PMID: 37073044 DOI: 10.1103/physreve.107.034606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 03/15/2023] [Indexed: 04/20/2023]
Abstract
The concept of the partial osmotic pressure of ions in an electrolyte solution is critically examined. In principle these can be defined by introducing a solvent-permeable wall and measuring the force per unit area which can certainly be attributed to individual ions. Here I demonstrate that although the total wall force balances the bulk osmotic pressure as required by mechanical equilibrium, the individual partial osmotic pressures are extrathermodynamic quantities dependent on the electrical structure at the wall, and as such they resemble attempts to define individual ion activity coefficients. The limiting case where the wall is a barrier to only one species of ion is also considered, and with ions on both sides the classic Gibbs-Donnan membrane equilibrium is recovered, thus providing a unifying treatment. The analysis can be extended to illustrate how the electrical state of the bulk is affected by the nature of the walls and the container handling history, thus supporting the "Gibbs-Guggenheim uncertainty principle," namely the notion that the electrical state is unmeasurable and usually accidentally determined. Since this uncertainty is conferred also onto individual ion activities, it has implications for the current (2002) IUPAC definition of pH.
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Affiliation(s)
- Patrick B Warren
- The Hartree Centre, STFC Daresbury Laboratory, Warrington WA4 4AD, United Kingdom
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3
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Radtke V, Gebel N, Priester D, Ermantraut A, Bäuerle M, Himmel D, Stroh R, Koslowski T, Leito I, Krossing I. Measurements and Utilization of Consistent Gibbs Energies of Transfer of Single Ions: Towards a Unified Redox Potential Scale for All Solvents. Chemistry 2022; 28:e202200509. [PMID: 35446995 PMCID: PMC9401597 DOI: 10.1002/chem.202200509] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Indexed: 11/08/2022]
Abstract
Utilizing the “ideal” ionic liquid salt bridge to measure Gibbs energies of transfer of silver ions between the solvents water, acetonitrile, propylene carbonate and dimethylformamide results in a consistent data set with a precision of 0.6 kJ mol−1 over 87 measurements in 10 half‐cells. This forms the basis for a coherent experimental thermodynamic framework of ion solvation chemistry. In addition, we define the solvent independent peabsH2O
‐ and the EabsH2O
values that account for the electronating potential of any redox system similar to the pHabsH2O
value of a medium that accounts for its protonating potential. This EabsH2O
scale is thermodynamically well‐defined enabling a straightforward comparison of the redox potentials (reducities) of all media with respect to the aqueous redox potential scale, hence unifying all conventional solvents′ redox potential scales. Thus, using the Gibbs energy of transfer of the silver ion published herein, one can convert and unify all hitherto published redox potentials measured, for example, against ferrocene, to the EabsH2O
scale.
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Affiliation(s)
- Valentin Radtke
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Niklas Gebel
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Denis Priester
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Andreas Ermantraut
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Monika Bäuerle
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Daniel Himmel
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Regina Stroh
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
| | - Thorsten Koslowski
- Institut für Physikalische Chemie Albert-Ludwigs-Universität Freiburg Albertstr. 23a 79104 Freiburg Germany
| | - Ivo Leito
- Institute of Chemistry University of Tartu Ravila 14a Str 50411 Tartu Estonia
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie Freiburger Materialforschungszentrum (FMF) and Freiburg Center for Interactive Materials and Bioinspired Technologies (FIT) Albert-Ludwigs-Universität Freiburg Albertstr. 21 79104 Freiburg Germany
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4
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A simplified methodology: pH sensing using an in situ fabricated Ir electrode under neutral conditions. J Solid State Electrochem 2021. [DOI: 10.1007/s10008-021-05017-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
AbstractHerein, a simplified fabrication method for the producing of a pH-sensitive iridium electrode is developed. The in situ electrochemical fabrication of an iridium oxide film is optimized and shown to be achievable under neutral conditions rather than the acidic conditions hitherto employed. The formation of a pH sensitive Ir(III/IV) hydrous film is confirmed via XPS. The amperometric pH-sensing properties of this electrochemically generated material were investigated using square wave voltammetry. In the pH range 2–13, the iridium oxide redox signal has a pH dependency of 86.1 ± 1.1 mV per pH unit for midpoint potentials with uncertainties being ± 0.01–0.05 pH. Finally, the newly developed pH sensor was used to measure the pH of a natural water sample with excellent results as compared to a conventional glass pH probe.
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Tanganov BB. Modeling of the Characteristics of Hydrogen Chloride Solutions in n-Alcohols. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2020. [DOI: 10.1134/s003602442006028x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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6
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Shu C, Zhu Q, Xiao K, Hou Y, Ma H, Ma J, Sun X. Direct Extracellular Electron Transfer of the Geobacter sulfurreducens Pili Relevant to Interaromatic Distances. BIOMED RESEARCH INTERNATIONAL 2019; 2019:6151587. [PMID: 31886232 PMCID: PMC6925702 DOI: 10.1155/2019/6151587] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Revised: 08/27/2019] [Accepted: 08/31/2019] [Indexed: 01/05/2023]
Abstract
Microorganisms can transfer electrons directly to extracellular acceptors, during which organic compounds are oxidized to carbon dioxide. One of these microbes, Geobacter sulfurreducens, is well known for the "metallic-like" conductivity of its type IV pili. However, there is no consensus on what the mechanism for electron transfer along these conductive pili is. Based on the aromatic distances and orientations of our predicted models, the mechanism of electron transfer in the Geobacter sulfurreducens (GS) pili was explored by quantum chemical calculations with Marcus theory of electron transfer reactions. Three aromatic residues from the N-terminal α-helix of the GS pilin subunit are packed together, resulting in a continuous pi-pi interaction chain. The theoretical conductance (4.69 μS/3.85 μS) of the predicted models is very similar to that in the experiments reported recently (3.40 μS). These findings offer a new concept that the GS pili belongs to a new class of proteins that can transport electrons through pi-pi interaction between aromatic residues and also provide a valuable tool for guiding further researches of these conductive pili, to investigate their roles in biogeochemical cycling, and potential applications in biomaterials, bioelectronics, and bioenergy.
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Affiliation(s)
- Chuanjun Shu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
- Department of Bioinformatics, School of Biomedical Engineering and Informatics, Nanjing Medical University, Nanjing 211166, China
| | - Qiang Zhu
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering and Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University, Nanjing 210023, China
| | - Ke Xiao
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Yue Hou
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
| | - Haibo Ma
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering and Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University, Nanjing 210023, China
| | - Jing Ma
- Institute of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering and Key Laboratory of Mesoscopic Chemistry of MOE, Nanjing University, Nanjing 210023, China
| | - Xiao Sun
- State Key Laboratory of Bioelectronics, School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China
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7
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Tai Y, Fung-Yee Tam N, Ruan W, Yang Y, Yang Y, Tao R, Zhang J. Specific metabolism related to sulfonamide tolerance and uptake in wetland plants. CHEMOSPHERE 2019; 227:496-504. [PMID: 31004816 DOI: 10.1016/j.chemosphere.2019.04.069] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/26/2019] [Accepted: 04/09/2019] [Indexed: 06/09/2023]
Abstract
Wetland plants are proven to perform well in water treatment. However, the phytoremediation capability of wetland plants for antibiotics, especially the uptake and metabolism involved in vivo, is poorly understood. In this study, we investigated the removal, uptake, and specific metabolism by Canna indica and Iris pseudacorus of five sulfonamides (SAs) using hydroponic experiments for seven days. The removal of SAs ranged from 15.2% to 98.4% in the planted groups, whereas that in the unplanted control group was much lower (12.6%-39.9%). The accumulation of SAs in plants was in a concentration-dependent manner via an active process and is not a major removal mechanism (constituted 0.31%-3.62% of the total removal load in plant system). The results also showed differences in the removal and accumulation by plant species of SAs. The acetyl conjugates (N-acetyl SA) were formed, which significantly enhanced the uptake of SAs (P < 0.001) except sulfapyridine. The concentrations of N-acetyl SA accounted for only 0.4%-23.8% of the total SAs distribution in plants, suggesting the involvement of other metabolism pathways. Methylation and oxidation metabolites were identified in plant tissues and no SA-induced growth stress occurred, revealing that antibiotic metabolism in vivo should be associated with the ability of wetland plants to accumulate antibiotic and tolerate antibiotic stress.
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Affiliation(s)
- Yiping Tai
- Research Center of Hydrobiology, Jinan University, Guangzhou, 510632, PR China; Research Centre of Tropic and Subtropic Aquatic Ecological Engineering, Ministry of Education, Guangzhou, 510632, PR China
| | - Nora Fung-Yee Tam
- Department of Chemistry, City University of Hong Kong, Hong Kong, SAR999077, PR China
| | - Weifeng Ruan
- Research Center of Hydrobiology, Jinan University, Guangzhou, 510632, PR China; Research Centre of Tropic and Subtropic Aquatic Ecological Engineering, Ministry of Education, Guangzhou, 510632, PR China
| | - Yufen Yang
- Research Center of Hydrobiology, Jinan University, Guangzhou, 510632, PR China; Research Centre of Tropic and Subtropic Aquatic Ecological Engineering, Ministry of Education, Guangzhou, 510632, PR China
| | - Yang Yang
- Research Center of Hydrobiology, Jinan University, Guangzhou, 510632, PR China; Research Centre of Tropic and Subtropic Aquatic Ecological Engineering, Ministry of Education, Guangzhou, 510632, PR China.
| | - Ran Tao
- Research Center of Hydrobiology, Jinan University, Guangzhou, 510632, PR China; Research Centre of Tropic and Subtropic Aquatic Ecological Engineering, Ministry of Education, Guangzhou, 510632, PR China
| | - Jingfan Zhang
- Research Center of Hydrobiology, Jinan University, Guangzhou, 510632, PR China; Research Centre of Tropic and Subtropic Aquatic Ecological Engineering, Ministry of Education, Guangzhou, 510632, PR China
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8
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Ring T, Kellum JA. Modeling Acid-Base by Minimizing Charge-Balance. ACS OMEGA 2019; 4:6521-6529. [PMID: 31459783 PMCID: PMC6648237 DOI: 10.1021/acsomega.9b00270] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 03/28/2019] [Indexed: 06/10/2023]
Abstract
In this study, we show that equilibrium pH can be obtained for any specified fluid with any number of buffers and dissociations. This is done by root finding in the equation for charge balance. We demonstrate that this equation is monotonic in proton concentration for conceivable buffers. We show that the total charge on any buffer is a function of only the total buffer concentration and pH, given the thermodynamic dissociation constants. Using the Davies' equation as a placeholder for single-ion activity coefficients as a function of charge and ionic strength, we develop an iterative algorithm, whereby the apparent dissociation constants are updated from the thermodynamic dissociation constants, and from this, the equilibrium is also identified in the nonideal state. We show how this algebra leads to guaranteed conservation of both thermodynamic dissociation constants and total buffer concentrations because the distribution of buffer species is fixed by the updated dissociation constants, actual pH, and total buffer concentration. Strong ions are assumed to contribute fixed charges. In order to concentrate on the process of modeling the equilibrium pH alone, this algorithm is examined against a series of theoretical results in which the Davies' equation was given the same status. However, a large sample of clinical pH measurements is also examined. To enhance the practical utility, CO2 and albumin are present as the default condition. We developed "ABCharge", a package in R, an open source language. The main function returns pH, activity coefficients, buffer species distribution, ionic strength, and charge balance for both the ideal and nonideal cases, for any mixture of any buffers with any number of known thermodynamic dissociation constants. Our algorithm can be updated if a more reliable and practical assessment of single-ion activities becomes available. Can Stock Photo/miceking.
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Affiliation(s)
- Troels Ring
- Department
of Biomedicine, Aarhus University, Vilh. Meyers Allé 3, 8000 Århus C, Denmark
- The
Center for Critical Care Nephrology. Department of Critical Care Medicine, University of Pittsburgh School of Medicine, and University
of Pittsburgh Medical Center, 15260 Pittsburgh, Pennsylvania, United States
| | - John A. Kellum
- The
Center for Critical Care Nephrology. Department of Critical Care Medicine, University of Pittsburgh School of Medicine, and University
of Pittsburgh Medical Center, 15260 Pittsburgh, Pennsylvania, United States
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9
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Leśniewski M, Śmiechowski M. Communication: Inside the water wheel: Intrinsic differences between hydrated tetraphenylphosphonium and tetraphenylborate ions. J Chem Phys 2018; 149:171101. [DOI: 10.1063/1.5056237] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Mateusz Leśniewski
- Department of Physical Chemistry, Chemical Faculty, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland
| | - Maciej Śmiechowski
- Department of Physical Chemistry, Chemical Faculty, Gdańsk University of Technology, Narutowicza 11/12, 80-233 Gdańsk, Poland
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10
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Hofer TS, Hünenberger PH. Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration. J Chem Phys 2018; 148:222814. [DOI: 10.1063/1.5000799] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Thomas S. Hofer
- Theoretical Chemistry Division, Institute of General, Inorganic and Theoretical Chemistry, Centre for Chemistry and Biomedicine, University of Innsbruck, Innrain 80-82, A-6020 Innsbruck, Austria
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11
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Özdenkçi K, Koskinen J, Sarwar G, Oinas P. Gibbs Free-Energy-Based Objective Function for Electrolyte Activity Coefficient Models. Ind Eng Chem Res 2017. [DOI: 10.1021/acs.iecr.7b01345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Karhan Özdenkçi
- Department of Chemical and
Metallurgical Engineering, Research Group of Plant Design, Aalto University, FI-00076 Aalto, Finland
| | - Jukka Koskinen
- Department of Chemical and
Metallurgical Engineering, Research Group of Plant Design, Aalto University, FI-00076 Aalto, Finland
| | - Golam Sarwar
- Department of Chemical and
Metallurgical Engineering, Research Group of Plant Design, Aalto University, FI-00076 Aalto, Finland
| | - Pekka Oinas
- Department of Chemical and
Metallurgical Engineering, Research Group of Plant Design, Aalto University, FI-00076 Aalto, Finland
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12
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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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13
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14
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Reif MM, Hünenberger PH. Origin of Asymmetric Solvation Effects for Ions in Water and Organic Solvents Investigated Using Molecular Dynamics Simulations: The Swain Acity-Basity Scale Revisited. J Phys Chem B 2016; 120:8485-517. [PMID: 27173101 DOI: 10.1021/acs.jpcb.6b02156] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The asymmetric solvation of ions can be defined as the tendency of a solvent to preferentially solvate anions over cations or cations over anions, at identical ionic charge magnitudes and effective sizes. Taking water as a reference, these effects are quantified experimentally for many solvents by the relative acity (A) and basity (B) parameters of the Swain scale. The goal of the present study is to investigate the asymmetric solvation of ions using molecular dynamics simulations, and to connect the results to this empirical scale. To this purpose, the charging free energies of alkali and halide ions, and of their hypothetical oppositely charged counterparts, are calculated in a variety of solvents. In a first set of calculations, artificial solvent models are considered that present either a charge or a shape asymmetry at the molecular level. The solvation asymmetry, probed by the difference in charging free energy between the two oppositely charged ions, is found to encompass a term quadratic in the ion charge, related to the different solvation structures around the anion and cation, and a term linear in the ion charge, related to the solvation structure around the uncharged ion-sized cavity. For these simple solvent models, the two terms are systematically counteracting each other, and it is argued that only the quadratic term should be retained when comparing the results of simulations involving physical solvents to experimental data. In a second set of calculations, 16 physical solvents are considered. The theoretical estimates for the acity A are found to correlate very well with the Swain parameters, whereas the correlation for B is very poor. Based on this observation, the Swain scale is reformulated into a new scale involving an asymmetry parameter Σ, positive for acitic solvents and negative for basitic ones, and a polarity parameter Π. This revised scale has the same predictive power as the original scale, but it characterizes asymmetry in an absolute sense, the atomistic simulations playing the role of an extra-thermodynamic assumption, and is optimally compatible with the simulation results. Considering the 55 solvents in the Swain set, it is observed that a moderate basity (Σ between -0.9 and -0.3, related to electronic polarization) represents the baseline for most solvents, while a highly variable acity (Σ between 0.0 and 3.0, related to hydrogen-bond donor capacity modulated by inductive effects) represents a landmark of protic solvents.
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Affiliation(s)
- Maria M Reif
- Physics Department (T38), Technische Universität München , D-85748 Garching, Germany
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15
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Ferse A, Ferse B. Individual ion activity and liquid junction potential—Two interrelated, interconnected electrochemical terms. Electrochim Acta 2016. [DOI: 10.1016/j.electacta.2016.01.167] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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