Synthesis and characterization of a novel one-dimensional iron phosphate: [C4H12N2]1.5[Fe2(OH)(H2PO4)(HPO4)2(PO4)]·0.5H2O

Abstract

An organically templated Fe^III phosphate, [C₄H₁₂N₂]_1.5[Fe₂(OH)(H₂PO₄)(HPO₄)₂(PO₄)]·0.5H₂O, has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, Mössbauer spectroscopy and thermogravimetric analysis. The compound crystallizes in the triclinic space group P (no. 2) with a = 6.3347(2), b = 13.0075(4), c = 13.7810(5) Å, α = 62.834(1), β = 81.404(1), γ = 82.688(1)°, U = 996.67(8) ų and Z = 2. The compound is unusual in that it is not only one of the few examples of 1-D organically templated iron phosphate, but also has a new type of chain structure which is built up from tetranuclear iron–oxygen clusters. The tetramer involves an edge-sharing dimer which further links at the shared corners to two more octahedra. These clusters are connected into the 1-D chain by PO₄ tetrahedra and have terminal HPO₄ and H₂PO₄ groups, with the piperazinium cations between the chains.