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The vast majority of chemical reactions occur in liquids. Rationalising liquid-phase reactivity is extremely difficult, as for any reaction a large number of electrons interact. Therefore, much more needs to be known about electron location and energy for reactive species in solution. In addition, solvents affect reactivity. However, our understanding of the specific and detailed effects of the solvent on reactive species is still in its infancy.

Direct measurements of liquid-phase electron location and energy (i.e. valence electronic structure) are extremely scarce, particularly for light elements, due to the problems posed by liquid vaporisation in the high vacuum conditions required for soft X-ray spectroscopy (apparatus pressure <10-8 mbar). Dr Lovelock uses synchrotron X-ray spectroscopy to measure liquid-phase electronic structure.

The techniques are:

• X-ray photoelectron spectroscopy (XPS)
• Auger electron spectroscopy (AES)
• resonant AES (RAES)
• resonant X-ray emission spectroscopy (RXES)
• core-hole clock spectroscopy
• near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.

The terminology of Lewis acids and bases is an attempt to rationalise chemical reactivity. Valence electronic structure is vital for understanding and predicting the reactivity of Lewis acids (electron-pair acceptors) and Lewis bases (electron-pair donors). Lewis reactivity features across all areas of chemistry.

Metal ions dissolved in ionic liquids can be used as both Lewis acidic and Lewis basic catalysts; these systems are particularly attractive due to the rare ability to fine-tune catalyst acidity/basicity. Frustrated Lewis pairs (FLPs) have been developed as outstanding candidates for small molecule activation, including H2 (for the hydrogen energy economy) and CO2for carboncapture and processing).