| Abstrakt: |
A 3-D, open framework, mixed valence iron phosphate, [H3NCH2CH2NH3]2[Fe4O(PO4)4]·H2O, 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&fourmacr;2m with a = 10.1383(8) Å, c = 9.628(1) Å, V = 989.6(1) Å3, Z = 2, and R(Rw) = 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 &fourmacr;3m symmetry. Mössbauer and ac magnetic susceptibility measurements show that equal amounts of valence trapped Fe2+ and Fe3+ are present, which undergo long range magnetic ordering at ~12 K. |
