X-ray diffraction, 133Cs and 1H NMR and thermal studies of CdZrCs1.5(H3O)0.5(C2O4)4·xH2O 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 P3112 (no. 151), <f>a=9.105(5)</f> Å, <f>c=23.656(5)</f> Å, <f>V=1698(1)</f> Å3 and <f>Z=3.</f> 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 1H and 133Cs 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. [Copyright &y& Elsevier]