New Chemistry and Physics from Transition-Metal Cyanides

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The aim of this research program is to characterise new solid-state materials with interesting structural and physical properties. The materials, transition-metal cyanides, are constructed by joining together simple structural building units. By assembling such units in different ways, we can design and produce a variety of new structures containing chains, layers and three-dimensional metal-cyanide frameworks. Some of these cyanide materials contain transition-metal ions in unusual coordination geometries, only found to date in biologically related systems. Others exhibit curious thermal behaviour such as 'negative thermal expansion', where they contract rather than expand on heating. A further class of cyanides act as molecular switches. The switches operate through changes in interatomic distances, geometry, colour and magnetic behaviour. Underlying all this work is the need to know the detailed structures of the materials on the atomic scale in order to explain their chemical and physical behaviours. The disordered nature of most of these materials makes their structural characterisation a challenge, which cannot be achieved in the home laboratory. To succeed in our aims, we need to use state-of-the art neutron and synchrotron facilities, which fortunately, the UK possesses at ISIS and Diamond. Using these facilities, we will also be able to determine how structures change with temperature and pressure. The knowledge of how structure evolves as a function of temperature and pressure is important in understanding both these materials and for the design of new materials of potential technological importance.