Iron arsenate frameworks

Abstract

Six new iron arsenate framework structures, Fe₂As₂O₇·2H₂O, [Fe₆As₈O₃₂H₄]²⁻(1,4-butanediamininium²⁺)·2H₂O, [Fe₄As₆O₂₂H₂]²⁻(piperazinium²⁺), [Fe₅As₅O₂₄H₄]²⁻(piperazinium²⁺)·2H₂O, [Fe₆As₇O₃₁H₅]²⁻(dabco²⁺) and LiFeAsO₄OH have been synthesised under hydrothermal conditions. Incorporation of the amine cation templates leads to more open framework geometries and, in contrast to iron phosphates which have topologies based on PO₄ tetrahedra, the iron arsenate structures typically contain protonated As(O,OH)₄ units. The magnetic properties of the iron arsenates studied show Curie–Weiss behaviours with maxima in the χ(T) vs.T plots in the range 10–50 K.