Cu2Th4(MoO4)9: Un nouveau squelette structural

The compound Cu2Th4(MoO4)9is cubic, space groupI43d, witha= 14.477(7) Å andZ=4. Its crystal structure has been determined from single crystal data by X-ray diffraction: Th(MoO4)9units are constituted by a ThO9polyhedron sharing corners with MoO4tetrahedra. The 3D framework delimits 12 cages per unit cell, two-thirds of which are occupied by CuIisolated atoms, in agreement with EXAFS results. A crystal chemistry study has been performed: isomorphous cationic substitutions involving small, monovalent cations (Li+, Cu+) are possible, leading to isotypic compounds with empty or partially occupied cages. Structural refinement of the isotypic compound La4(MoO4)3(ReO4)6by the Rietveld method confirms the existence of empty cages and thus the relative stability of this new structural skeleton.