Determination of the molecular structures of tungstates by Raman spectroscopy

Abstract An empirical correlation is developed for relating the wavenumbers of (WO) stretching modes to WO bond lengths and bond strengths for tungsten oxide reference compounds. A least‐squares exponential fit of crystallographically determined WO bond lengths to the wavenumbers of their Raman stretching modes is presented along with a relation between WO bond strengths, in valence units, and wavenumbers of Raman stretching modes. The empirical bond length/stretching mode wavenumber/bond strength relationships lead to a unique and effective method of interpreting Raman spectra of tungstate species. This method leads to the WO bond lengths and coordination of the tungstate species. The utility of the method is illustrated by estimating the wavenumbers of the Raman stretching modes for the ideal WO 4 tetrahedron and WO 6 octahedron, and the bonds lengths and coordinations of the tungstate species in the reference compounds Na 2 WO 4 , PbWO 4 , CaWO 4 and Bi 2 WO 6 . In addition, the WO bond lengths of the WO 6 octahedra in crystalline Ba 2 MgWO 6 are reported for the first time. This new approach for evaluating the Raman spectra of tungstate species is expected to be generally applicable to all tungstates, regardless of environment, physical state, or oxidation state.