First structural determination of layered and pillared organic derivatives of γ-zirconium phosphate by X-ray powder diffraction data

Abstract

This paper reports the structural characterization of one layered and one pillared organic derivative of γ-zirconium phosphate dihydrogenphosphate, ZrPO 4O 2P(OH)C 3H 7·H 2O and ZrPO 4[O 2P(OH)C 4H 8(OH)PO 2] 0.5·H 2O, respectively. They were obtained by topotactic exchange of n-propylphosphonate and butyldiphosphonate groups on γ-ZrPO 4O 2P(OH) 2·2H 2O. The strategies used to prepare these compounds with a degree of crystallinity sufficient for structure analysis by X-ray powder diffraction (XRPD) data are described. The structures were determined `ab initio' by Patterson methods after decomposition of the pattern with the La Bail method, and final Rietveld refinement. Depending on the method of preparation used, two phases were found for the layered propylphosphonate derivative: one is orthorhombic, a=30.212(2), b=6.6128(4) and c=5.3612(3) Å, space group Pna2 1, Z=4; the other is monoclinic, a=5.3593(4), b=6.6217(4) and c=30.695(2) Å, β=98.810(3)°, space group P2 1/ c, Z=4. The pillared butyldiphosphonate derivative is orthorhombic, a=5.3797(2), b=6.6244(2) and c=13.0111(5) Å, space group Pmmn. As predicted many years ago, the structure of the γ-inorganic backbone was maintained after the topotactic reaction, for both layered and pillared organic derivatives.