Research Projects in the Harper Group

The research carried out in this group can be divided into a number of distinct areas.  Below we have our principal projects listed and, along with brief descriptions of what we have achieved so far in these areas, are listed the directions that we hope to take them in the future.  For further information on past work, consult our publications and for further information on future directions, please contact Jason Harper.

Understanding Organic Processes in Ionic Liquids

Ionic liquids are salts that are molten a room temperature (or less than 100°C) and there has been much interest in developing them as alternatives to volatile organic solvents.  However, the outcome of a reaction (both in terms of rate and selectivity) is not readily predicted on going from a traditional 'molecular' solvent to an ionic liquid.  The aims of our research in this area is to develop this predictive framework.  The ionic liquids used are representative of those in the literature to ensure that the our results have value to other researchers; we tend to use the bmim (1-butyl-3-methylimidazolium) cation with the charge balanced by either a bistriflimide (bis(trifluoromethanesulfonimide)) or dca (dicyanimide) anion.

Our previous studies have focused on well-described processes such as the SN1 process shown here.  In this case, addition of an ionic liquid (bmim bistriflimide) was found to increase the rate of reaction at small concentrations but to decrease it at larger concentrations (Brad Man).  Calculation of the activation parameters for the process under these conditions showed that the addition of ionic liquid resulted in an enthalpic benefit (which dominates at low concentrations) and an entropic cost (which dominates at high concentrations) (Hon Man Yau).  The reorganisation required is supported by molecular dynamics simulations and the ordering can be clearly seen in the probability diagram shown here.

We are currently attempting to expand these studies to other reactions, particularly other substitution processes (Hon Man Yau), cycloaddition processes (Camille Rosella) and hydrolysis reactions (SJ Chan and Erika Davies).  The important point is that if a reaction outcome can't be explained in ionic liquids, it should be investigated!

This work is done in collaboration with Dr Anna Croft (Bangor University) and, as it has links to the project below, with Dr Jim Hook (Analytical Centre, UNSW).

Heteronuclear Magnetic Resonance Spectroscopy to Follow Reaction Kinetics

In the project described above, it is necessary to be able follow the progress of a chemical reaction.  Traditional techniques to do not always function well in ionic liquids.  For example, proton NMR spectroscopy is limited as deuterated versions of the ionic liquids are difficult to come bay.  As such, thanks to the work (and perserverance) of Bradley Man (one of the early undergraduate students in the group) we have been examining NMR spectroscopy of less frequently used nuclei in order to overcome these problems.  There are a range of advantages of these techniques, particularly in that spectra typically contain a greatly reduced number of signals (often just the one!) and obtaining NMR silent solvents is much more straightforward.

While traditional heteronuclei (such as fluorine-19) have been used and work well, not all reactions involve such atoms.  As such, we have extended this to nuclei that might be present in an organic process.  The reaction described above was our first demonstration, since it generates chloride ion and can be readily followed using chlorine-35 NMR spectroscopy (Brad Man).  Where other techniques fail (including proton NMR and GC), the spectrum of the reaction mixture shows simply an increasing signal due to the chloride ion produced (organochlorides are NMR silent due to the asymmetric chlorine environment).

We are currently extending this to look at other nuclei, particularly bromine-79 and oxygen-17 (both by SJ Chan), and examining the utility of these novel techniques.  During the course of our studies, an interesting temperature effect in fluorine-19 NMR spectroscopy was observed (Erika Davies) and potential applications of this are being investigated.

This work is carried out in collaboration with Dr Jim Hook (Analytical Centre, UNSW).

Switchable Surfaces

It is advantageous

Supramolecular Constructs Based on Unsaturated Hydrocarbons

Developing New Ways to Define Water Availability

Group XIV Tetratolyl Derivatives

Controlling Atropisomerism using Diketopiperazine Scaffolds

Determination of Reaction Mechanisms

Electron Donating Ability of C-H and C-C bonds

This page is currently under construction.  Please check back regularly for updates.

Last Updated October 6th 2009