X-ray diffraction, 133Cs and 1H NMR and thermal studies of CdZrCs1.5(H3O)0.5(C2O4)4•x H2O displaying Cs and water dynamic behavior

A novel mixed cadmium zirconium cesium oxalate with an open architecture has been synthesized from precipitation methods at room pressure. It crystallizes with an hexagonal symmetry, space group P3(1)12 (no. 151), a = 9.105(5) Angstrom, c = 23.656(5) Angstrom, V = 1698(1) Angstrom(3) and Z = 3. The structure displays a [CdZr(C2O4)(4)](2-) helicoidal framework built from CdO8 and ZrO8 square-based antiprisms connected through bichelating oxalates, which generates channels along different directions. Cesium cations, hydronium ions and water molecules are located inside the voids of the anionic framework. They exhibit a dynamic disorder which has been further investigated by H-1 and Cs-133 solid-state NMR. Moreover a phase transition depending both upon ambient temperature and water vapor pressure was evidenced for the title compound. The thermal decomposition has been studied in situ by temperature-dependent X-ray diffraction and thermogravimetry. The final product is a mixture of cadmium oxide, zirconium oxide and cesium carbonate. (C) 2004 Elsevier Ltd. All rights reserved.