• A-priori prediction of IL character
• Functionalised ILs
• Protic ILs: Ionic or neutral?
• Mixtures!

• The viscosity challenge
• Hydrogen bonding in ILs: Exotic or ordinary?
• Aqueous contamination of ILs
• Novel conductors

Kamlet and Taft developed a method which correlates the relative effects of a solvent to the absorbance spectrum of a selection of dyes (one of which is nitroanaline) to quantify the polarizability (pi), H-bond donor ability (alpha) and H-bond acceptor ability (beta) of solvents in general. Our collaborator, Prof Tom Welton has applied this method to investigate the characteristics of ionic liquds. We use ab-initio quantum chemical methods with small probe molecules to evaluate these parameters. This means we can model prospective ILs and predict their characteristics before the more expensive and labourous process of synthesis is attempted.

doi A step towards the a-priori design of ionic-liquids, H. Niedermeyer, C. Ashworth, A. Brandt, T. Welton and P. Hunt PCCP, 2013 15, 11566-11578

doi Why does a reduction in hydrogen-bonding lead to an increase in viscosity for the 1-butyl-2,3-dimethyl-imidazolium based ionic liquids?, P. Hunt , J. Phys. Chem. B., 2007, Vol 111, Iss. (18), 4844-53

The high viscosity of ionic liquids is a limiting factor for mass/energy transfer in catalytic applications, charge movement in electrochemical devices and suitability as a lubricant. Ionic liquids are generally perceived as solid systems with an increased inherent disorder (due to the asymmetrical ions), and a reduced columbic interaction (due to the large size of the ions), which prevents regular crystal packing and makes them liquid at room temperature. However, the above general hypothesis is insufficient to account for detailed correlations that are experimentally observed. It is very important for the future development of ionic liquids, and their application that the viscosity be reduced. This project will explore the underlying molecular level reasons for the high viscosity.

The basic IL cations (and to a lesser extent the anions) have been functionalised with carboxylic acids, alcohols, ethers, nitriles, amides, thioureas, siloxanes ... however how the functional group effects the physical and chemical properties of the IL are not well understood at the molecular level. We use ab-initio methods to investigate the electronic structure and H-bonding with the aim of building rules that can be used to predict and rationalise the effects each type of functional group has on the IL.

doi Understanding siloxane functionalised ionic liquids H. Niedermeyer, M. Ab Rani, P. Lickiss, J. Hallett, T. Welton, A. White and P. Hunt , PCCP, 2010, Vol 12, Iss. (8), p2018-2029

doi Hydrogen Bonding in 1-Butyl- and 1-Ethyl-3-methylimidazolium Chloride Ionic Liquids, I. Skarmoutsos, D. Dellis, R. Matthews, T. Welton, and P. Hunt, JPCB, 2012, Vol 116, Iss. (16), p4921-4933

Normally H-bonds exist between two neutral species, or in a cation-neutral or anion-neutral arrangement. However, in ILs the H-bonds formed are between ions. This kind of H-bond has not been documented, and displays unique characteristics. We use ab-initio methods to investigate the electronic structure of these H-bonds, and classical methods to investigate the dynamic nature of these H-bonds.

The dynamics of H-bonds in water is well studied, in contrast the dynamics of the H-bonds in ILs are largely unknown. We have established that the criteria for defining H-bonds used in molecular liquids do not revieal the whole story of H-bonding in ILs. H-bonds in IL are less structured and more diverse.

Protic ILs have an "available" proton, usually this is supplied by the cation but can also be delivered by the anion. Protic ILs are not pure ILs because the proton transfer is an equilibrium process. We use ab-initio methods to investigate the proton transfer and stability of the ion-pair vs the neutral acid-base components of the IL.

Current MRes Green Chemistry Project

Water is a ubiquitious contaminant of ILs. Many applications include aqueous solutions of IL at a range of concentrations. Water is a small neutral but highly polar moleucle which can interact with either or both of the cation and anion, it can also insert between the cation and anion. Alternatively water can accumulate in clusters creating heterogenous areas within the IL. We are using ab-initio methods to investigate how water interacts with ionic liquids
doi Why are ionic liquid ions mainly associated in water? A Car-Parrinello study of 1-ethyl-3-methyl-imidazolium chloride water mixture, C. Spickermann, J. Thar, S. Lehmann, S. Zahn, J. Hunger, R. Buchner, PA Hunt, T. Welton, B. Kirchner, J. Chem. Phys., 2008, Vol 129, Iss. (10), no 104505

Nickel complexes change colour when heated in an ionic liquid. [NiCl₄]2- (tetrahedral) is blue in a "hot" ionic liquid, and becomes yellow or green (octahedral) on cooling. The required temperature range is easily accessible in indirect sunlight and hence we have solar thermochromic materials. How does the IL instigate this structural change? Image from Prof George Chen at Nottingham University who discovered these materials

Ionic liquids are being used as electrolytes in industrial clean metal production, and in electronic devices such as fuel cells and next generation batteries. However, the detailed mechanism for conduction within ionic liquids is unknown! We are examining how small ions like Li are solvated within ILs, and how contaminants like water effect the conduction. This project is undertaken in association with the experimental group of Dr Tim Albrecht

What happens when you mix ILs? Do particular ions favour pairing, or do they mix in an ideal manner? Are nano-structured domains formed?
What is the difference between functionalising an IL and mixing the pure IL with an equal proportion of the neutral solvent? What happens when we mix an alcohol or another neutral molecular solvent with an IL? Both H-bond but in very different ways.

doi Salts dissolved in salts: ionic liquid mixtures, M. Lui, L. Crowhurst, J. Hallett, P. Hunt, H. Niedermeyer and T. Welton Chemical Science, 2011, Vol 2, Iss. (8), p1491-1496