Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7*H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates

Pierre Gras (1) , Nicolas Ratel-Ramond (2) , Sébastien Teychené (3) , Christian Rey (1) , Erik Elkaim (4) , Beatrice Biscans (3) , Stéphanie Sarda (1) , Christèle Combes (1)

1 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
2 CEMES - Centre d'élaboration de matériaux et d'études structurales
3 LGC - Laboratoire de Génie Chimique
4 SSOLEIL - Synchrotron SOLEIL

Calcium pyrophosphate hydrate (CPP, Ca2P2O7*nH2O) and calcium orthophosphate compounds (including apatite, octa­calcium phosphate etc.) are among the most prevalent pathological calcifications in joints. Even though only two dihydrated forms of CPP (CPPD) have been detected in vivo (monoclinic and triclinic CPPD), investigations of other hydrated forms such as tetra­hydrated or amorphous CPP are relevant to a further understanding of the physicochemistry of those phases of biological inter­est. The synthesis of single crystals of calcium pyrophosphate monohydrate (CPPM; Ca2P2O7*H2O) by diffusion in silica gel at ambient temperature and the structural analysis of this phase are reported in this paper. Complementarily, data from synchrotron X-ray diffraction on a CPPM powder sample have been fitted to the crystal parameters. Finally, the relationship between the resolved structure for the CPPM phase and the structure of the tetra­hydrated calcium pyrophosphate [beta] phase (CPPT-[beta]) is discussed.

Mots clés: Crystal structure; Calcium pyrophosphate hydrates; Powder diffraction; Structure determination; Pathological calcification; Synchrotron study

Domaines: Matériaux

Pierre Gras, Nicolas Ratel-Ramond, Sébastien Teychené, Christian Rey, Erik Elkaim, et al.. Structure of the calcium pyrophosphate monohydrate phase (Ca2P2O7*H2O): towards understanding the dehydration process in calcium pyrophosphate hydrates. Acta Crystallographica Section C : Structural Chemistry [2014-..], 2014, vol. 70, pp. 862-866. ⟨10.1107/S2053229614017446⟩. ⟨hal-01073729⟩