Symmetry and optical spectra: a "silent" 1 : 2 Np(V)-oxydiacetate complex.

The 1 : 2 Np(V)-oxydiacetate complex, NpO(2)(ODA)(2)(3-), identified by single-crystal X-ray diffractometry for the first time, is centrosymmetric around the Np atom so that the f-f transitions of Np(V) are forbidden, resulting in the "silence" of the absorption and diffuse reflectance spectra of this complex in solution and the solid state in the near-IR and visible regions.