Cs3UGe7O18: A Pentavalent Uranium Germanate Containing Four- and Six-Coordinate Germanium

A pentavalent uranium germanate, Cs3UGe7O18, was synthesized under high-temperature, high-pressure hydrothermal conditions at 585 °C and 160 MPa and structurally characterized by single-crystal X-ray diffraction and infrared spectroscopy. The valence state of uranium was confirmed by X-ray photoelectron spectroscopy and electron paramagnetic resonance. The room-temperature EPR spectrum can be simulated with two components using an axial model that are consistent with two distinct sites of uranium(V). In the structure of the title compound, each [6]GeO6 octahedron is bonded to six three-membered single-ring [4]Ge3O96– units to form germanate triple layers in the ab plane. Each layer contains nine-ring windows; however, these windows are blocked by adjacent layers. The triple layers are further connected by UO6 octahedra to form a three-dimensional framework with intersecting six-ring channels along the ⟨110⟩ directions. The Cs+ cation sites are fully occupied, ordered, and located in the cavities of the f...