A 3-D Organically Templated Mixed Valence (Fe2+/Fe3+) Iron Phosphate with Oxide-Centered Fe4O(PO4)4 Cubes: Hydrothermal Synthesis, Crystal Structure, Magnetic Susceptibility, and Mössbauer Spectroscopy of [H3NCH2CH2NH3]2[Fe4O(PO4)4]·H2O

A 3-D, open framework, mixed valence iron phosphate, [H 3 NCH 2 CH 2 NH 3 ] 2 [Fe 4 O(PO 4 ) 4 ]·H 2 O, which contains organic ethylenediammonium dications in the framework voids, has been prepared via hydrothermal synthesis and has been characterized by single-crystal X-ray diffraction, magnetic susceptibility, and variable temperature Mössbauer spectroscopy. Crystal data: tetragonal, space group I 4̄2 m with a = 10.1383(8) Å, c = 9.628(1) Å, V = 989.6(1) Å 3, Z = 2, and R ( R w ) = 7.7(6.5) for 276 reflections ( I > 3σ( I )) and 32 variables. The fundamental building block of the structure is a novel cubane-like cluster with trigonal bipyramidal iron and tetrahedral phosphorus atoms lying at alternate vertexes of a cube with a tetrahedrally coordinated oxygen atom at the center of the cube. Each cluster is linked by eight Fe−O−P bonds that extend along what would be all 〈111〉 directions of the putative cube to eight similar clusters to form a framework that is only slightly distorted (by the presence of the organic cations) from cubic 4̄3 m symmetry. Mössbauer and ac magnetic susceptibility measurements show that equal amounts of valence trapped Fe 2+ and Fe 3+ are present, which undergo long range magnetic ordering at ∼12 K.