Synthesis, structure refinement and thermal behavior of HEuP2O74H2O

The synthesis, the structure refinement and the thermal behavior are reported for a new diphosphate HEuP2O74H2O. This salt crystallizes in a monoclinic cell, a space group P21/n with: a=6.6320(2); b=11.5273(5); c=11.7574(5)A; beta=92.024(2) deg ; Z=4. The crystal structure was refined to R=0.0402 using 1572 reflections. The corresponding atomic arrangement consists of corrugated layers of [HP2] groups alternating with layers of the Eu3+ cations perpendicular to the [101] direction. Three of the crystallization water molecules are intercalated between these layers and participate to the coordination of the europium atom, the fourth one is located inside the anionic layer. The thermal decomposition of HEuP2O74H2O, which was followed by thermogravimetry and differential thermal analysis, shows that the dehydration of this salt took place between 361 and 1223 K. It gave, after dehydration, a mixture of europium diphosphate Eu4(P2O7)3 and europium tripolyphosphate Eu(PO3)3.