Scheme: Leverhulme Trust Senior Research Fellowship
Organisation: University of Sheffield
Dates: Feb 2013-Jan 2014
Summary: This project summary is not available for publication.
Scheme: Wolfson Research Merit Awards
Dates: Aug 2005-Sep 2009
Summary: The main aim of the research is to understand better what makes some molecules 'aromatic', a term which implies special structure, properties and chemistry. When aromatic molecules are exposed to a magnetic field, the circulation induced in their least bound electrons gives rise to characteristic ‘ring currents’. The most famous example is benzene, with its special stability, six equivalent carbon-carbon bonds of length between single and double bonds, characteristic reactivity and special magnetic properties. The induced currents themselves affect the local magnetic fields and so are observed indirectly through the fingerprint of the molecule in Nuclear Magnetic Resonance Spectroscopy, a technique that is used to assign structures to newly synthesised molecules. The present research is concerned with predicting the strength, direction and distribution of these currents. One aim is the development of an accurate technique for computing the currents by solving the basic equations that govern the motions of electrons in molecules. This has now been done for many molecules, and the results mapped to give direct yes/no answers to questions of aromaticity. The second aim is construction of simple qualitative models that use ideas about symmetry and energy to predict the essentials of these maps from what we know about the molecule in the absence of the field. In many cases, the current depends on the spatial distribution of just the top 2 or 4 electrons of an unsaturated molecule and can be predicted without heavy calculation. Better understanding of aromaticity should help in molecular design, and synthesis of molecules with optimum properties for applications. Understanding ring currents may also help in understanding the currents that flow through molecules acting as nano-scale conductors. In particular, we have worked this year on conduction through graphenes - single sheets of graphite - ultimately to find rules connecting shape and conduction.
Organisation: University of Exeter
Dates: Oct 2004-Jul 2005