The structure of a novel mixed-valent chromium uranyl compound, (C3NH10)10[(UO2)13(Cr125+O42)(Cr6+O4)6(H2O)6](H2O)6 (1), obtained by the combination of a hydrothermal method and evaporation from aqueous solutions with isopropylammonium, contains uranyl chromate hemispheres with lateral dimensions of 18.9 × 18.5 Å2 and a height of about 8 Å. The hemispheres are centered by a UO8 hexagonal bipyramid surrounded by six dimers of Cr5+O5 square pyramids, UO7 pentagonal bipyramids, and Cr6+O4 tetrahedra. The hemispheres are linked into two-dimensional layers so that two adjacent hemispheres are oriented in opposite directions relative to the plane of the layer. From a topological point of view, the hemispheres have the formula U21Cr23 and can be considered as derivatives of nanospherical cluster U26Cr36 composed of three-, four-, and five-membered rings.
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