Heteropolytungstate complexes of the lanthanide elements. Part II. Electronic spectra: a metal–ligand charge-transfer transition of cerium(III)

Abstract

The small nephelauxetic parameters dβ for lanthanide heteropolytungstate complexes show that the Ln–O bond is essentially ionic. The absorption spectra of the Eu^III complexes indicate, in each case, site symmetry not higher than tetragonal for the lanthanide; the emission spectra of EuW₁₀O₃₅^7– and Eu(SiW₁₁O₃₉)₂^11– in the solid state agree best with D_2d and D_4h microsymmetry respectively. The bands causing the brown colours of the Ce^III complexes, whose wavenumbers increase with the Ce^IV/Ce^III redox potential, are assigned to metal–ligand charge-transfer.