Title Details

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 1

1.1 Prologue 1

1.2 The Definition of an Ionic Liquid 2

1.3 A Brief Perspective 6

1.4 Aprotic Versus Protic ILs 8

1.5 An Overview of IL Applications 9

1.6 Key Properties and Techniques for Understanding ILs 12

1.6.1 Viscosity 12

1.6.2 Vapor Pressure 13

1.6.3 Melting Point 13

1.6.4 Nanostructure 14

1.6.5 Thermal Properties 14

1.6.6 Electrochemical Properties 16

1.6.7 Conductivity and Ion Transport 16

1.6.8 Computational Techniques 17

1.7 New Materials Based on ILs 18

1.8 Nomenclature and Abbreviations 20

References 20

2 The Structure of Ions that Form Ionic Liquids 27

2.1 Introduction 27

2.2 Ionic Interactions and the Melting Point 28

2.2.1 Thermodynamics of the Melting Point 29

2.3 Effect of Ion Size and Crystal Packing 31

2.3.1 Quantifying the Madelung Constant 34

2.3.2 Computational Prediction of the Melting Point 35

2.4 Charge Delocalization and Shielding 37

2.5 Ion Asymmetry 39

2.6 Influence of Cation Substituents 41

2.7 Degrees of Freedom and Structural Disorder 43

2.7.1 Polymorphism 44

2.8 Short-Range Interactions –Hydrogen Bonding 44

2.9 Dications and Dianions 47

2.10 Tm Trends in Other IL Families 49

2.11 Concluding Remarks 50

References 50

3 Structuring of Ionic Liquids 55

3.1 Introduction 55

3.2 Ionicity, Ion Pairing and Ion Association 56

3.3 Short-Range Structuring 58

3.4 Structural Heterogeneity and Domain Formation 60

3.5 Hydrogen Bonding and Structure 62

3.6 Experimental Probes of Structure 64

3.7 Simulation Approaches to Understanding Structure 67

3.8 Structuring at Solid Interfaces 71

3.9 Ionic Liquid Structure in Confined Spaces 74

3.10 Impact of Structure on Reactivity and Application 75

3.11 Concluding Remarks 76

References 76

4 Synthesis of Ionic Liquids 81

4.1 Introduction 81

4.2 Synthesis of ILs 81

4.2.1 Formation of the Cation: Quaternization/Alkylation 81

4.2.2 Anion Exchange 82

4.2.2.1 Metathesis 83

4.2.2.2 Purification and Challenges of the Metathesis Reaction 84

4.2.2.3 Ion Exchange 85

4.2.3 Synthesis of ILs via the Carbonate Route 86

4.2.4 Flow Reactors 87

4.2.5 Solvate ILs 89

4.2.6 Chloroaluminate ILs 90

4.2.7 Task-Specific Ionic liquids (TSILs) 90

4.2.7.1 Alkoxy-Ammonium ILs 90

4.2.7.2 Zwitterionic Liquids 91

4.2.8 One-Pot Synthesis of Multi-Ion ILs 92

4.2.9 Polymer Ionic Liquids (Poly-ILs) 93

4.2.10 Protic Ionic Liquids (PILs) 95

4.2.11 Chiral ILs 96

4.3 Characterization and Analysis of ILs 97

4.4 Concluding Remarks 98

References 99

5 Physical and Thermal Properties 103

5.1 Introduction 103

5.2 Phase Transitions and Thermal Properties 103

5.2.1 Thermal Analysis and the Key Transitions Defining the Liquid State 103

5.2.2 Glass Transition, Glassy ILs, and the Kauzman Paradox 104

5.2.3 The Ideal Glass Transition 107

5.2.4 Influence of Ion Structure on Tg 108

5.2.5 Solid–Solid Transitions 109

5.2.5.1 Plastic Crystalline Phases 109

5.2.5.2 Liquid Crystals 110

5.2.6 Vaporization 110

5.2.7 Thermal Decomposition 113

5.2.8 Thermal Conductivity and Heat Capacity 117

5.3 Surface and Tribological Properties 118

5.4 Transport Properties and their Inter-relationships 120

5.4.1 Temperature Dependence of Transport Properties 124

5.4.2 Ionicity and theWalden Plot 126

5.4.2.1 Modeling the Transport Properties of ILs. 128

5.5 Properties of Ionic Liquid Mixtures 129

5.5.1 Thermal Properties 130

5.5.1.1 Melting Behavior of Mixtures of Salts and the Entropy of Mixing 130

5.5.1.2 Eutectics 132

5.5.2 Excess Molar Volume (VE) 134

5.5.3 Viscosity 135

5.5.4 Conductivity 136

5.5.5 Ionicity 137

5.6 Protic ILs, Proton Transfer, and Mixtures 139

5.7 Deep Eutectic Solvents and Solvate ILs 141

5.8 Concluding Remarks 142

References 143

6 Solvent Properties of Ionic Liquids: Applications in Synthesis and Separations 149

6.1 Introduction – Solvency and Intermolecular Forces 149

6.2 Liquid–Liquid Phase Equilibrium 151

6.2.1 Liquid Solubility, Mixing, and Demixing 151

6.2.2 Solvent Extraction 152

6.3 Gas Solubility and Applications 154

6.3.1 Physical Dissolution of Gases 154

6.3.2 Chemical Dissolution of Gases 158

6.4 Synthetic Chemistry in ILs – Selected Examples 159

6.4.1 Solvent Control of Reactions –Toluene+HNO3 160

6.4.2 Recovery of Expensive Catalysts:The Heck Reaction 161

6.4.3 Increased Reaction Rates and Enantiomeric Selectivity in Diels–Alder Reactions 162

6.4.4 Modulation of the Lewis Acidity of Catalysts:The Friedel–Crafts Reaction 163

6.4.5 Shift in Equilibrium by Stabilizing the Intermediate Species in the Rate-Determining Step: the Baylis–Hilman Reaction 165

6.4.6 Increase in Rate Constant at Low IL Concentrations: Substitution Reactions 166

6.5 Inorganic Materials Synthesis 167

6.6 Biomass Dissolution 169

6.6.1 Cellulose and Lignocellulose 169

6.6.2 Chitin 170

6.6.3 Keratin 170

6.6.4 Wool 171

6.6.5 Silk 171

6.7 Concluding Remarks 172

References 172

7 Electrochemistry of and in Ionic Liquids 177

7.1 Basic Principles of Electrochemistry in Nonaqueous Media 177

7.1.1 Redox Potentials 177

7.1.2 Three-Electrode Measurements 178

7.1.3 Potential Scanning Techniques 179

7.1.4 Reference Electrodes in IL Media 180

7.2 The ElectrochemicalWindow of Ionic Liquids 182

7.2.1 The Effect of Impurities 183

7.2.2 Choice ofWorking Electrode 184

7.2.3 Other Factors Affecting the ElectrochemicalWindow 184

7.3 Redox Processes in ILs 185

7.3.1 Internal Calibrants 185

7.3.2 Redox Couples for DSSCs 185

7.3.3 Metal Bipyridyl Complexes 187

7.3.4 Organic Redox Reactions 188

7.3.5 Polyoxometallates 189

7.3.6 Redox-Active ILs 190

7.4 Electrodeposition and Cycling of Metals in ILs 191

7.4.1 Chloroaluminate-Based ILs 193

7.4.2 Zinc 193

7.4.3 Aluminium Deposition from Air andWater Stable ILs 193

7.4.4 Lithium 194

7.4.5 Sodium 194

7.4.6 Magnesium 194

7.5 Electrosynthesis in Ionic Liquids 195

7.5.1 Oxidation Reactions 197

7.5.1.1 Fluorination 197

7.5.1.2 Oxidation of Alcohols 198

7.5.2 Reduction Reactions 199

7.5.2.1 CO2 Reduction 199

7.5.2.2 Carbon–Carbon Bond Formation 200

7.6 Concluding Remarks 202

References 202

8 Electrochemical Device Applications 209

8.1 Introduction 209

8.2 Batteries 210

8.2.1 Lithium–Ion Battery 210

8.2.2 High-Voltage Cathodes 214

8.2.3 Alternative High-Energy-Density Batteries 215

8.3 Fuel Cells 216

8.4 Dye-Sensitized Solar Cells andThermoelectrochemical Cells 220

8.5 Supercapacitors 223

8.6 Actuators 225

8.7 Concluding Remarks 226

References 227

9 Biocompatibility and Biotechnology Applications of Ionic Liquids 231

9.1 Biocompatibility of Ionic Liquids 231

9.1.1 Chemical Toxicity 231

9.1.2 Osmotic Toxicity 232

9.1.3 Biodegradation 233

9.1.4 Hydrated Ionic Liquids 234

9.2 Ionic Liquids from Active Pharmaceutical Ingredients 234

9.2.1 Dual Actives 235

9.2.2 Patent Matters 236

9.2.3 Protic Forms of APIs 236

9.2.4 Antimicrobials 237

9.2.5 Other Actives – Pesticides and Herbicides 237

9.3 Biomolecule Stabilization in IL Media 238

9.3.1 Proteins 238

9.3.2 DNA and RNA 239

9.3.3 Buffer ILs 241

9.3.4 Structural Proteins 242

9.4 Concluding Remarks 242

References 243

Index 245