A study of how the crystalline environment of a molecule can influence its behaviour over a range of temperatures brings the development of molecular switches a step closer, suggests British inorganic chemist, Malcolm Halcrow.

With colleagues at the universities of Durham, Hull, Leeds and Manchester, Halcrow looked at a copper complex which, as a crystal, contains two geometrically dissimilar molecules that are chemically identical but behave differently.

Using crystallography, electron paramagnetic resonance and theoretical calculations, the team notes how the differing environment each molecule experiences in the crystal influences its degree of Jahn-Teller distortion. This effect, common in complexes of copper and several other transition metals, occurs when electrons rearrange themselves to lower the energy of a molecule, thereby distorting its geometry. The structures of half of the molecules in the complex did not vary when temperatures fell below 350 Kelvin; the others did (seen as a change in copper-nitrogen bond lengths) between 225 and 375 Kelvin.

Claire Darby