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Silva AT, Teixeira C, Marques EF, Prudêncio C, Gomes P, Ferraz R. Surfing the Third Wave of Ionic Liquids: A Brief Review on the Role of Surface-Active Ionic Liquids in Drug Development and Delivery. ChemMedChem 2021; 16:2604-2611. [PMID: 33908193 DOI: 10.1002/cmdc.202100215] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2021] [Indexed: 12/12/2022]
Abstract
The relevance of ionic liquids (ILs) is now well established in many fields, as their unique properties make them appealing as 1) greener alternatives to organic solvents (first-generation ILs), 2) tunable task-specific materials (second-generation ILs), and 3) multifunctional players in life and pharmaceutical sciences (third-generation ILs). This third wave of ILs encompasses a wide range of compounds, from bioactive molecules with single or even dual therapeutic action, to potential ingredient molecules for drug formulation and transport systems. In this context, the focus of this review is the emergent role of surface-active ionic liquids (SAILs) in drug development and delivery.
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Affiliation(s)
- Ana Teresa Silva
- LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Cátia Teixeira
- LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Eduardo F Marques
- CIQ-UP, Centro de Investigação em Química da Universidade do Porto, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Cristina Prudêncio
- CQB/CISA - Ciências Químicas e das Biomoléculas, Escola Superior de Saúde, Politécnico do Porto, Rua Dr. António Bernardino de Almeida 400, 4200-072, Porto, Portugal.,Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, 4200-072, Porto, Portugal
| | - Paula Gomes
- LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal
| | - Ricardo Ferraz
- LAQV-REQUIMTE, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal.,CQB/CISA - Ciências Químicas e das Biomoléculas, Escola Superior de Saúde, Politécnico do Porto, Rua Dr. António Bernardino de Almeida 400, 4200-072, Porto, Portugal
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Mann SK, Brown SP, MacFarlane DR. Structure Effects on the Ionicity of Protic Ionic Liquids. Chemphyschem 2020; 21:1444-1454. [DOI: 10.1002/cphc.202000242] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Revised: 05/17/2020] [Indexed: 11/11/2022]
Affiliation(s)
- Sarah K. Mann
- Department of Physics University of Warwick Coventry CV4 7AL U.K
| | - Steven P. Brown
- Department of Physics University of Warwick Coventry CV4 7AL U.K
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Hollóczki O, Wolff A, Pallmann J, Whiteside RE, Hartley J, Grasser MA, Nockemann P, Brunner E, Doert T, Ruck M. Spontaneous Substitutions at Phosphorus Trihalides in Imidazolium Halide Ionic Liquids: Grotthuss Diffusion of Anions? Chemistry 2018; 24:16323-16331. [PMID: 30157298 DOI: 10.1002/chem.201803558] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Oldamur Hollóczki
- Mulliken Center for Theoretical Chemistry; University of Bonn; Beringstrasse 4+6 53115 Bonn Germany
| | - Alexander Wolff
- Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
| | - Julia Pallmann
- Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
| | - Rachel E. Whiteside
- School of Chemistry and Chemical Engineering; Queen's University of Belfast; Belfast BT7 1NN UK
| | - Jennifer Hartley
- Institute of Inorganic Chemistry; TU Bergakademie Freiberg; 09599 Freiberg Germany
| | - Matthias A. Grasser
- Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
| | - Peter Nockemann
- School of Chemistry and Chemical Engineering; Queen's University of Belfast; Belfast BT7 1NN UK
| | - Eike Brunner
- Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
| | - Thomas Doert
- Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
| | - Michael Ruck
- Faculty of Chemistry and Food Chemistry; Technische Universität Dresden; 01062 Dresden Germany
- Max Planck Institute for Chemical Physics of Solids; Nöthnitzer Strasse 40 01187 Dresden Germany
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Li K, Yan Y, Zhao J, Lei J, Jia X, Mushrif SH, Yang Y. Understanding the role of hydrogen bonding in Brønsted acidic ionic liquid-catalyzed transesterification: a combined theoretical and experimental investigation. Phys Chem Chem Phys 2016; 18:32723-32734. [DOI: 10.1039/c6cp06502c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The intra- and inter-hydrogen bonding networks that govern the catalytic activity of Brønsted acidic ionic liquids were identified.
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Affiliation(s)
- Kaixin Li
- School of Chemical and Biomedical Engineering
- Nanyang Technological University
- Singapore
- Residues and Resource Reclamation Centre (R3C)
- Nanyang Environment and Water Research Institute
| | - Yibo Yan
- School of Chemical and Biomedical Engineering
- Nanyang Technological University
- Singapore
| | - Jun Zhao
- School of Chemical and Biomedical Engineering
- Nanyang Technological University
- Singapore
| | - Junxi Lei
- Residues and Resource Reclamation Centre (R3C)
- Nanyang Environment and Water Research Institute
- Nanyang Technological University
- 1 Cleantech Loop
- CleanTech One
| | - Xinli Jia
- School of Chemical and Biomedical Engineering
- Nanyang Technological University
- Singapore
| | - Samir H. Mushrif
- School of Chemical and Biomedical Engineering
- Nanyang Technological University
- Singapore
| | - Yanhui Yang
- School of Chemical and Biomedical Engineering
- Nanyang Technological University
- Singapore
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Santner S, Heine J, Dehnen S. Synthesis of Crystalline Chalcogenides in Ionic Liquids. Angew Chem Int Ed Engl 2015; 55:876-93. [PMID: 26661858 DOI: 10.1002/anie.201507736] [Citation(s) in RCA: 114] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Indexed: 11/12/2022]
Abstract
Crystalline chalcogenides belong to the most promising class of materials. In addition to dense solid-state structures, they may form molecular cluster arrangements and networks with high porosity, as in the so-called "zeotype" chalcogenidometalates. The high structural diversity comes along with interesting physical properties such as semi-/photoconductivity, ion transport capability, molecular trapping potential, as well as chemical and catalytic activity. The great interest in the development of new and tailored chalcogenides has provoked a continuous search for new and better synthesis strategies over the years. The trend has clearly been towards lower temperatures for both economic and ecological reasons as well as for better reaction control. This led to the application of ionic liquids as a designer-like medium for materials synthesis. In this Review, we summarize recent developments and present a survey of different chalcogenide families along with their properties.
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Affiliation(s)
- Silke Santner
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032, Marburg, Germany
| | - Johanna Heine
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032, Marburg, Germany
| | - Stefanie Dehnen
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032, Marburg, Germany.
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Santner S, Heine J, Dehnen S. Synthese kristalliner Chalkogenide in ionischen Flüssigkeiten. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201507736] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Silke Santner
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 35032 Marburg Deutschland
| | - Johanna Heine
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 35032 Marburg Deutschland
| | - Stefanie Dehnen
- Fachbereich Chemie und Wissenschaftliches Zentrum für Materialwissenschaften; Philipps-Universität Marburg; Hans-Meerwein-Straße 35032 Marburg Deutschland
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Kuchenbuch A, Giernoth R. Ionic Liquids Beyond Simple Solvents: Glimpses at the State of the Art in Organic Chemistry. ChemistryOpen 2015; 4:677-81. [PMID: 27308192 PMCID: PMC4906501 DOI: 10.1002/open.201500113] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2015] [Indexed: 11/26/2022] Open
Abstract
Within the last 25 years ionic liquids have written a tremendous success story, which is documented in a nearly uncountable amount of original research papers, reviews, and numerous applications in research and industry. These days, ionic liquids can be considered as a mature class of compounds for many different applications. Frequently, they are used as neoteric solvents for chemical tansformations, and the number of reviews on this field of research is huge. In this focused review, though, we are trying to evaluate the state of the art of ionic liquid chemistry beyond using them simply as solvents for chemical transformations. It is not meant to be a comprehensive overview on the topic; the choice of emphasis and examples rather refects the authors' personal view on the field. We are especially highlighting fields in which we believe the most fundamental developments within the next five years will take place: biomass processing, (chiral) ionic liquids from natural sources, biotransformations, and organic synthesis.
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Affiliation(s)
| | - Ralf Giernoth
- Department für ChemieUniversität zu KölnGreinstr. 450939KölnGermany
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Brehm M, Weber H, Thomas M, Hollóczki O, Kirchner B. Domain Analysis in Nanostructured Liquids: A Post-Molecular Dynamics Study at the Example of Ionic Liquids. Chemphyschem 2015; 16:3271-7. [DOI: 10.1002/cphc.201500471] [Citation(s) in RCA: 86] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 07/11/2015] [Indexed: 11/09/2022]
Affiliation(s)
- Martin Brehm
- Helmholtz-Zentrum für Umweltforschung Leipzig, Department Ökologische Chemie; Permoserstrasse 15 04318 Leipzig Germany
| | - Henry Weber
- Mulliken Center for Theoretical Chemistry; Rheinische Friedrich-Wilhelms-Universität Bonn; Beringstr. 4+6 53115 Bonn Germany
| | - Martin Thomas
- Mulliken Center for Theoretical Chemistry; Rheinische Friedrich-Wilhelms-Universität Bonn; Beringstr. 4+6 53115 Bonn Germany
| | - Oldamur Hollóczki
- Mulliken Center for Theoretical Chemistry; Rheinische Friedrich-Wilhelms-Universität Bonn; Beringstr. 4+6 53115 Bonn Germany
| | - Barbara Kirchner
- Mulliken Center for Theoretical Chemistry; Rheinische Friedrich-Wilhelms-Universität Bonn; Beringstr. 4+6 53115 Bonn Germany
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Fumino K, Fossog V, Stange P, Paschek D, Hempelmann R, Ludwig R. Controlling the subtle energy balance in protic ionic liquids: dispersion forces compete with hydrogen bonds. Angew Chem Int Ed Engl 2015; 54:2792-5. [PMID: 25639210 DOI: 10.1002/anie.201411509] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Indexed: 11/11/2022]
Abstract
The properties of ionic liquids are determined by the energy-balance between Coulomb-interaction, hydrogen-bonding, and dispersion forces. Out of a set of protic ionic liquids (PILs), including trialkylammonium cations and methylsulfonate and triflate anions we could detect the transfer from hydrogen-bonding to dispersion-dominated interaction between cation and anion in the PIL [(C6 H13 )3 NH][CF3 SO3 ]. The characteristic vibrational features for both ion-pair species can be detected and assigned in the far-infrared spectra. Our approach gives direct access to the relative strength of hydrogen-bonding and dispersion forces in a Coulomb-dominated system. Dispersion-corrected density functional theory (DFT) calculations support the experimental findings. The dispersion forces could be quantified to contribute about 2.3 kJ mol(-1) per additional methylene group in the alkyl chains of the ammonium cation.
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Affiliation(s)
- Koichi Fumino
- Universität Rostock, Institut für Chemie, Abteilung für Physikalische Chemie, Dr.-Lorenz-Weg 1, 18059, Rostock (Germany)
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Fumino K, Fossog V, Stange P, Paschek D, Hempelmann R, Ludwig R. Steuerung der subtilen Energiebalance in protischen ionischen Flüssigkeiten: Dispersionskräfte im Wettstreit mit Wasserstoffbrücken. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201411509] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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11
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Weiz A, Bruns J, Wickleder MS. Reaction with SO 3in Ionic Liquids: The Example of K 2(S 2O 7)(H 2SO 4). Z Anorg Allg Chem 2014. [DOI: 10.1002/zaac.201300416] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Beichel W, Eiden P, Krossing I. Establishing consistent van der Waals volumes of polyatomic ions from crystal structures. Chemphyschem 2013; 14:3221-6. [PMID: 23956232 DOI: 10.1002/cphc.201300659] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2013] [Indexed: 11/07/2022]
Abstract
Based on temperature (T) dependent crystal structure data of seven organic salts, a radii-based scheme for the calculation of the van der Waals volume (V(vdw)) is analyzed. The obtained volumes (V(vdw,r), r=radius-based) are nearly T independent. An ion volume partitioning scheme is proposed by fixing the anion volumes of [Cl](-), [Br](-), [I](-), [BF(4)](-), [PF(6)](-), [OTf](-) and [NTf(2)](-). The van der Waals volumes (V(vdw,r) (+/-)) of 48 ions are established, with low standard deviations (0.2-3.6 Å(3), 0.1-4.5 % of V(vdw,r) (+/-)). The ion volumes are independent of the counterion and one crystal structure already suffices for their derivation. Correlations of the viscosity with V(vdw,r) via a Litovitz ansatz and our recently derived Arrhenius-type approach prove that these volumes are suitable for the volume-based description and prediction of IL properties. The corresponding correlation coefficient for the latter is R(2)=0.86 for 40 ILs (354 data points) in the T range of 253-373 K.
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Affiliation(s)
- Witali Beichel
- Institut für Anorganische und Analytische Chemie, Albert-Ludwigs-Universität Freiburg, Albertstraße 21, D-79104 Freiburg i. Br. (Germany), Fax: (+49) 761 203-6001; Freiburger Materialforschungszentrum (FMF), Albert-Ludwigs-Universität Freiburg, Stefan-Meier-Straße 21, D-79104 Freiburg i. Br. (Germany).
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Hollóczki O, Kelemen Z, Könczöl L, Szieberth D, Nyulászi L, Stark A, Kirchner B. Significant cation effects in carbon dioxide-ionic liquid systems. Chemphyschem 2013; 14:315-20. [PMID: 23281169 PMCID: PMC3597992 DOI: 10.1002/cphc.201200970] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2012] [Indexed: 11/09/2022]
Abstract
Carbon dioxide–ionic liquid systems are of great current interest, and significant efforts have been made lately to understand the intermolecular interactions in these systems. In general, all the experimental and theoretical studies have concluded so far that the main solute–solvent interaction takes effect through the anion, and the cation has no, or only a secondary role in solvation. In this theoretical approach it is shown that this view is unfounded, and evidence is provided that, similarly to the benzene–CO2 system, dispersion interactions are present between the solute and the cation. Therefore, this defines a novel site for tailoring solvents to tune CO2 solubility.
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Affiliation(s)
- Oldamur Hollóczki
- Wilhelm-Ostwald-Institut für Physikalische und Theoretische Chemie, Universität Leipzig, Germany
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González L, Altava B, Bolte M, Burguete MI, García-Verdugo E, Luis SV. Synthesis of Chiral Room Temperature Ionic Liquids from Amino Acids - Application in Chiral Molecular Recognition. European J Org Chem 2012. [DOI: 10.1002/ejoc.201200607] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Pensado AS, Brehm M, Thar J, Seitsonen AP, Kirchner B. Effect of Dispersion on the Structure and Dynamics of the Ionic Liquid 1-Ethyl-3-methylimidazolium Thiocyanate. Chemphyschem 2012; 13:1845-53. [DOI: 10.1002/cphc.201100917] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2011] [Indexed: 11/09/2022]
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Dommert F, Wendler K, Berger R, Delle Site L, Holm C. Force Fields for Studying the Structure and Dynamics of Ionic Liquids: A Critical Review of Recent Developments. Chemphyschem 2012; 13:1625-37. [DOI: 10.1002/cphc.201100997] [Citation(s) in RCA: 226] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Indexed: 11/06/2022]
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Freudenmann D, Wolf S, Wolff M, Feldmann C. Ionic liquids: new perspectives for inorganic synthesis? Angew Chem Int Ed Engl 2011; 50:11050-60. [PMID: 21990270 DOI: 10.1002/anie.201100904] [Citation(s) in RCA: 265] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Indexed: 11/09/2022]
Abstract
Ionic liquids are credited with a number of unusual properties. These include a low vapor pressure, a wide liquid-phase range, weakly coordinating properties, and a high thermal/chemical stability. These properties are certainly of great interest for inorganic synthesis and the creation of novel inorganic compounds. On the other hand, the synthesis repertoire for preparing inorganic compounds has always been broad, ranging from syntheses in solutions and melts to solid-state reactions, and from crystal growth in the gas phase to high-pressure syntheses. What new aspects can ionic liquids then add to the synthesis of inorganic compounds? This Minireview uses some early examples to show that the use of ionic liquids indeed provides access to unusual inorganic compounds.
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Affiliation(s)
- Dominic Freudenmann
- Institut für Anorganische Chemie, Karlsruhe Institute of Technology (KIT), Engesserstrasse 15, 76131 Karlsruhe, Germany
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Freudenmann D, Wolf S, Wolff M, Feldmann C. Ionische Flüssigkeiten - neue Perspektiven für die anorganische Synthesechemie? Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201100904] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Preiss U, Verevkin SP, Koslowski T, Krossing I. Going Full Circle: Phase‐Transition Thermodynamics of Ionic Liquids. Chemistry 2011; 17:6508-17. [DOI: 10.1002/chem.201003150] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Indexed: 11/07/2022]
Affiliation(s)
- Ulrich Preiss
- Freiburger Materialforschungszentrum, Universität Freiburg, Stefan‐Meier‐Str. 21, 79104 Freiburg (Germany), Fax:(+49) 761‐203‐6001
| | - Sergey P. Verevkin
- Abteilung Physikalische Chemie, Universität Rostock, Dr.‐Lorenz‐Weg 1, 18059 Rostock (Germany)
| | - Thorsten Koslowski
- Institut für Physikalische Chemie, Universität Freiburg, Albertstr. 23a, 79104 Freiburg (Germany)
| | - Ingo Krossing
- Freiburger Materialforschungszentrum, Universität Freiburg, Stefan‐Meier‐Str. 21, 79104 Freiburg (Germany), Fax:(+49) 761‐203‐6001
- Institut für Anorganische und Analytische Chemie and Fellow of the Freiburg Institute for Advanced Studies (FRIAS), Universität Freiburg, Albertstr. 21, 79104 Freiburg (Germany)
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Cremer T, Kolbeck C, Lovelock KRJ, Paape N, Wölfel R, Schulz PS, Wasserscheid P, Weber H, Thar J, Kirchner B, Maier F, Steinrück HP. Towards a molecular understanding of cation-anion interactions--probing the electronic structure of imidazolium ionic liquids by NMR spectroscopy, X-ray photoelectron spectroscopy and theoretical calculations. Chemistry 2010; 16:9018-33. [PMID: 20658502 DOI: 10.1002/chem.201001032] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ten [C(8)C(1)Im](+) (1-methyl-3-octylimidazolium)-based ionic liquids with anions Cl(-), Br(-), I(-), [NO(3)](-), [BF(4)](-), [TfO](-), [PF(6)](-), [Tf(2)N](-), [Pf(2)N](-), and [FAP](-) (TfO=trifluoromethylsulfonate, Tf(2)N=bis(trifluoromethylsulfonyl)imide, Pf(2)N=bis(pentafluoroethylsulfonyl)imide, FAP=tris(pentafluoroethyl)trifluorophosphate) and two [C(8)C(1)C(1)Im](+) (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br(-) and [Tf(2)N](-) were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While (1)H NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C(2) position and the anion, a comparative XPS study provides first direct experimental evidence for cation-anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid's anion. These charge-transfer effects are found to be surprisingly similar for [C(8)C(1)Im](+) and [C(8)C(1)C(1)Im](+) salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions.
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Affiliation(s)
- Till Cremer
- Lehrstuhl für Physikalische Chemie II, Universität Erlangen-Nürnberg, Egerlandstrasse 3, 91058 Erlangen, Germany
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Ríos-Lombardía N, Busto E, Gotor-Fernández V, Gotor V, Porcar R, García-Verdugo E, Luis SV, Alfonso I, García-Granda S, Menéndez-Velázquez A. From salts to ionic liquids by systematic structural modifications: a rational approach towards the efficient modular synthesis of enantiopure imidazolium salts. Chemistry 2010; 16:836-47. [PMID: 19946902 DOI: 10.1002/chem.200901623] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This paper reports a simple and robust modular synthetic strategy that leads to a large variety of configurationally and structurally diverse imidazole-based chiral ionic liquids (CILs) by lipase-catalyzed resolution. The intimate microscopic interactions of the supramolecular ionic network of these imidazolium chiral salts at the molecular level are investigated both spectroscopically (NMR, FT-IR-ATR) and theoretically, and a topological analysis of the experimental electron densities obtained by X-ray diffraction of single crystals is performed. Our results support the key role played by the relative configuration of the -OR group on the hydrogen-bonding pattern and its strong influence on the final physical properties of the imidazolium salt. We also obtained a reasonable correlation between the observed melting point and the non-covalent interactions. The spectroscopic data and the topological analysis reflect the key role played by hydrogen bonds between the OH and imidazolium C2H groups in both cation-anion and cation-cation interactions, with the presence of an OH group leading to an additional inter-cation interaction. This interaction significantly affects the properties of stereoisomeric salts. Even more interestingly, we also studied the effect of the chirality by comparing enantiopure CILs with their racemic mixtures and found that, with the exception of trans-Cy6-OH-Im-Bn-Br, the melting points of the racemic mixtures are higher than those of the corresponding enantiomerically pure forms. For stereoisomeric examples, we have successfully explained the differences in melting temperatures in light of the corresponding structural data. Chirality should therefore be taken into account as a highly attractive design vector in the preparation of ILs with specifically desired properties.
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Affiliation(s)
- Nicolás Ríos-Lombardía
- Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Biotecnología de Asturias, Universidad de Oviedo, 33071 Oviedo, Spain
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