Flux crystal growth and structural analysis of two cesium uranium oxides, Cs2.2U5O16 and Cs2U4O13, containing multiple cation–cation interactions

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Single crystals of Cs2.2U5O16 and Cs2U4O13 have been synthesized from a CsCl flux with the ramp rate controlling the formation of fully oxidized Cs2U4O13versus partially reduced Cs2.2U5O16. Their structures have been determined by single crystal X-ray diffraction. Cs2.2U5O16 crystallizes in the monoclinic space group C2/m with lattice parameters a = 13.4160(5) Å, b = 15.5089(6) Å, c = 7.9723(3) Å, and β = 92.7120(10)° and Cs2U4O13 crystallizes in the orthorhombic space group Ccmm with lattice parameters a= 13.5031(6) Å, b = 15.4048(7) Å, c = 39.5680(17) Å. The two compounds contain related uranium frameworks with disordered Cs atoms within the channels. Both structures contain multiple cation–cation interactions, CCIs, which arise due to the three dimensional nature of the framework. Magnetic properties are reported for Cs2.2U5O16, which contains mixed valent U.