Fundamentals of Ionic Liquids

Professor Doug MacFarlane leads the Monash Ionic Liquids Group at Monash University. He is currently the holder of an Australian Research Council Laureate Fellowship. He is also the Program Leader of the Energy Program in the Australian Centre of Excellence for Electromaterials Science. His group focuses on a range of aspects of ionic liquids and their application in the energy sciences and sustainable chemistry. Professor MacFarlane was a BSc(Hons) graduate of Victoria University of Wellington, New Zealand and then undertook his graduate work in the Angell group at Purdue University, Indiana, graduating in 1983. After postdoctoral fellowships in France and New Zealand he took up an academic position at Monash. He has been a Professor of Chemistry at Monash since 1995 and was Head of School 2003-2006. A/Prof Jennifer Pringle is a Senior Research Fellow in the Institute for Frontier Materials at Deakin University, and a chief investigator in the ARC Centre of Excellence for Electromaterials Science. She received her degree and PhD at The University of Edinburgh in Scotland before moving to Monash University in Melbourne, Australia in 2002. From 2008-2012 she held an ARC QEII Fellowship, investigating the use of ionic electrolytes for dye-sensitized solar cells. A/Prof Pringle moved to Deakin University, Melbourne in 2013. There she leads research into the development and use of ionic electrolytes for applications including thermal energy harvesting and solid state lithium batteries. Dr. Mega Kar is a Research Fellow in the Monash Ionic Liquids group. She completed her undergraduate degree with honours at The University of Melbourne in 2008. She then went onto study her doctor of philosophy (PhD) at Monash University in Professor Douglas MacFarlane?s group, which focused on designing novel room-temperature alkoxy-ammonium based ionic liquids as electrolytes for reversible zinc electrochemistry, working towards a rechargeable metal-air battery for energy storage applications. Dr. Kar is currently a Research Fellow at Monash University, lecturing and specializing in IL synthesis and electrochemistry, working on electrodeposition and metal batteries.

• 1 An Introduction to Ionic Liquids 11.1 Prologue 11.2 The Definition of an Ionic Liquid 21.3 A Brief Perspective 61.4 Aprotic Versus Protic ILs 81.5 An Overview of IL Applications 91.6 Key Properties and Techniques for Understanding ILs 121.6.1 Viscosity 121.6.2 Vapor Pressure 131.6.3 Melting Point 131.6.4 Nanostructure 141.6.5 Thermal Properties 141.6.6 Electrochemical Properties 161.6.7 Conductivity and Ion Transport 161.6.8 Computational Techniques 171.7 New Materials Based on ILs 181.8 Nomenclature and Abbreviations 20References 202 The Structure of Ions that Form Ionic Liquids 272.1 Introduction 272.2 Ionic Interactions and the Melting Point 282.2.1 Thermodynamics of the Melting Point 292.3 Effect of Ion Size and Crystal Packing 312.3.1 Quantifying the Madelung Constant 342.3.2 Computational Prediction of the Melting Point 352.4 Charge Delocalization and Shielding 372.5 Ion Asymmetry 392.6 Influence of Cation Substituents 412.7 Degrees of Freedom and Structural Disorder 432.7.1 Polymorphism 442.8 Short-Range Interactions – Hydrogen Bonding 442.9 Dications and Dianions 472.10 T m Trends in Other IL Families 492.11 Concluding Remarks 50References 503 Structuring of Ionic Liquids 553.1 Introduction 553.2 Ionicity, Ion Pairing and Ion Association 563.3 Short-Range Structuring 583.4 Structural Heterogeneity and Domain Formation 603.5 Hydrogen Bonding and Structure 623.6 Experimental Probes of Structure 643.7 Simulation Approaches to Understanding Structure 673.8 Structuring at Solid Interfaces 713.9 Ionic Liquid Structure in Confined Spaces 743.10 Impact of Structure on Reactivity and Application 753.11 Concluding Remarks 76References 764 Synthesis of Ionic Liquids 814.1 Introduction 814.2 Synthesis of ILs 814.2.1 Formation of the Cation: Quaternization/Alkylation 814.2.2 Anion Exchange 824.2.2.1 Metathesis 834.2.2.2 Purification and Challenges of the Metathesis Reaction 844.2.2.3 Ion Exchange 854.2.3 Synthesis of ILs via the Carbonate Route 864.2.4 Flow Reactors 874.2.5 Solvate ILs 894.2.6 Chloroaluminate ILs 904.2.7 Task-Specific Ionic liquids (TSILs) 904.2.7.1 Alkoxy-Ammonium ILs 904.2.7.2 Zwitterionic Liquids 914.2.8 One-Pot Synthesis of Multi-Ion ILs 924.2.9 Polymer Ionic Liquids (Poly-ILs) 934.2.10 Protic Ionic Liquids (PILs) 954.2.11 Chiral ILs 964.3 Characterization and Analysis of ILs 974.4 Concluding Remarks 98References 995 Physical and Thermal Properties 1035.1 Introduction 1035.2 Phase Transitions and Thermal Properties 1035.2.1 Thermal Analysis and the Key Transitions Defining the Liquid State 1035.2.2 Glass Transition, Glassy ILs, and the Kauzman Paradox 1045.2.3 The Ideal Glass Transition 1075.2.4 Influence of Ion Structure on Tg 1085.2.5 Solid–Solid Transitions 1095.2.5.1 Plastic Crystalline Phases 1095.2.5.2 Liquid Crystals 1105.2.6 Vaporization 1105.2.7 Thermal Decomposition 1135.2.8 Thermal Conductivity and Heat Capacity 1175.3 Surface and Tribological Properties 1185.4 Transport Properties and their Inter-relationships 1205.4.1 Temperature Dependence of Transport Properties 1245.4.2 Ionicity and the Walden Plot 1265.4.2.1 Modeling the Transport Properties of ILs. 1285.5 Properties of Ionic Liquid Mixtures 1295.5.1 Thermal Properties 1305.5.1.1 Melting Behavior of Mixtures of Salts and the Entropy of Mixing 1305.5.1.2 Eutectics 1325.5.2 Excess Molar Volume (V E) 1345.5.3 Viscosity 1355.5.4 Conductivity 1365.5.5 Ionicity 1375.6 Protic ILs, Proton Transfer, and Mixtures 1395.7 Deep Eutectic Solvents and Solvate ILs 1415.8 Concluding Remarks 142References 1436 Solvent Properties of Ionic Liquids: Applications in Synthesis and Separations 1496.1 Introduction – Solvency and Intermolecular Forces 1496.2 Liquid–Liquid Phase Equilibrium 1516.2.1 Liquid Solubility, Mixing, and Demixing 1516.2.2 Solvent Extraction 1526.3 Gas Solubility and Applications 1546.3.1 Physical Dissolution of Gases 1546.3.2 Chemical Dissolution of Gases 1586.4 Synthetic Chemistry in ILs – Selected Examples 1596.4.1 Solvent Control of Reactions – Toluene + HNO3 1606.4.2 Recovery of Expensive Catalysts: The Heck Reaction 1616.4.3 Increased Reaction Rates and Enantiomeric Selectivity in Diels–Alder Reactions 1626.4.4 Modulation of the Lewis Acidity of Catalysts: The Friedel–Crafts Reaction 1636.4.5 Shift in Equilibrium by Stabilizing the Intermediate Species in the Rate-Determining Step: the Baylis–Hilman Reaction 1656.4.6 Increase in Rate Constant at Low IL Concentrations: Substitution Reactions 1666.5 Inorganic Materials Synthesis 1676.6 Biomass Dissolution 1696.6.1 Cellulose and Lignocellulose 1696.6.2 Chitin 1706.6.3 Keratin 1706.6.4 Wool 1716.6.5 Silk 1716.7 Concluding Remarks 172References 1727 Electrochemistry of and in Ionic Liquids 1777.1 Basic Principles of Electrochemistry in Nonaqueous Media 1777.1.1 Redox Potentials 1777.1.2 Three-Electrode Measurements 1787.1.3 Potential Scanning Techniques 1797.1.4 Reference Electrodes in IL Media 1807.2 The Electrochemical Window of Ionic Liquids 1827.2.1 The Effect of Impurities 1837.2.2 Choice of Working Electrode 1847.2.3 Other Factors Affecting the Electrochemical Window 1847.3 Redox Processes in ILs 1857.3.1 Internal Calibrants 1857.3.2 Redox Couples for DSSCs 1857.3.3 Metal Bipyridyl Complexes 1877.3.4 Organic Redox Reactions 1887.3.5 Polyoxometallates 1897.3.6 Redox-Active ILs 1907.4 Electrodeposition and Cycling of Metals in ILs 1917.4.1 Chloroaluminate-Based ILs 1937.4.2 Zinc 1937.4.3 Aluminium Deposition from Air and Water Stable ILs 1937.4.4 Lithium 1947.4.5 Sodium 1947.4.6 Magnesium 1947.5 Electrosynthesis in Ionic Liquids 1957.5.1 Oxidation Reactions 1977.5.1.1 Fluorination 1977.5.1.2 Oxidation of Alcohols 1987.5.2 Reduction Reactions 1997.5.2.1 CO2 Reduction 1997.5.2.2 Carbon–Carbon Bond Formation 2007.6 Concluding Remarks 202References 2028 Electrochemical Device Applications 2098.1 Introduction 2098.2 Batteries 2108.2.1 Lithium–Ion Battery 2108.2.2 High-Voltage Cathodes 2148.2.3 Alternative High-Energy-Density Batteries 2158.3 Fuel Cells 2168.4 Dye-Sensitized Solar Cells and Thermoelectrochemical Cells 2208.5 Supercapacitors 2238.6 Actuators 2258.7 Concluding Remarks 226References 2279 Biocompatibility and Biotechnology Applications of Ionic Liquids 2319.1 Biocompatibility of Ionic Liquids 2319.1.1 Chemical Toxicity 2319.1.2 Osmotic Toxicity 2329.1.3 Biodegradation 2339.1.4 Hydrated Ionic Liquids 2349.2 Ionic Liquids from Active Pharmaceutical Ingredients 2349.2.1 Dual Actives 2359.2.2 Patent Matters 2369.2.3 Protic Forms of APIs 2369.2.4 Antimicrobials 2379.2.5 Other Actives – Pesticides and Herbicides 2379.3 Biomolecule Stabilization in IL Media 2389.3.1 Proteins 2389.3.2 DNA and RNA 2399.3.3 Buffer ILs 2419.3.4 Structural Proteins 2429.4 Concluding Remarks 242References 243Index 245