FT-IR SPECTROSCOPY - A SENSITIVE PROBE OF CONCEALED SYMMETRY-LOWERING IN TETRANUCLEAR COPPER(II) COMPLEXES

Vibrational spectra of metal complexes containing tetrahedral clusters are a sensitive test of slight distortions from ideal tetrahedral geometry. Comparison with crystal structures reported by X-ray diffraction shows that the latter consistently underestimate the magnitude of the distortion, to the extent that in some cases the space group is observed to be exactly cubic, while the molecules are of lower symmetry. The structures of the molecules are averaged out by disorder, and the extent to which this can occur can be estimated quantitatively by comparing the data from the two techniques.