CSFE3(PO4)3(OH2)2 - A MIXED-VALENCE IRON PHOSPHATE-CONTAINING TRIMERIC UNITS OF IRON OXYGEN POLYHEDRA

A mixed-valence iron phosphate, CsFe3(PO4)3(OH2)2, has been synthesize d hydrothermally and characterized by single-crystal X-ray diffraction and Mossbauer spectroscopy. The compound crystallizes in the monoclin ic space group C2/c with a = 13.435(2), b = 10.488(1), c = 9.024(2) an gstrom, beta = 108.60(1)-degrees, U = 1205.1(3) angstrom3 and Z = 4. T he structure consists of a three-dimensional framework of vertex-shari ng Fe(III)O5 trigonal bipyramids, Fe(II)O4(OH2)2 octahedra and PO4 tet rahedra, enclosing a network of cavities, where the caesium cations re side. Mossbauer spectroscopy confirms the presence of one Fe(II) and t wo Fe(III).