Crystal Structure and Luminescence Site of Na9[EuW10O36]·32H2O

Abstract Na9[EuW10O36]·32H2O, obtained from aqueous solutions, crystallizes in space group Cc with a = 11.484(5), b = 23.020(7), c = 23.581(6) Å, β = 91.71(3)°, V = 6231(3) Å3, Mr = 3349.4, Dx = 3.57 Mg m−3, and Z = 4. A full-matrix least-squares refinement finally yields R = 0.070 and Rw = 0.086 for 6473 independent reflections. The local symmetry around Eu3+ for the [EuW10O36]9− anion is approximately square antiprismatic. Photoexcitation into the oxygen-to-tungsten charge transfer bands of a solid sample leads to red emission due to f–f transitions within Eu3+, as a result of an intramolecular energy transfer from the W5O18 group to the Eu atom. The spectral transitions of photoluminescence recorded at 4.2 K can be interpreted based on the assumption of a C4v point group for Eu3+, which is consistent with the co-ordination geometry for the Eu atom.