Synthesis and characterization of fluorinated metal arsenates with a layer structure:...

Two fluorinated metal arsenates, (C(4)H(12)N(2))(1.5)[M(3)F(5)(HAsO(4))(2)(AsO(4))] (M = Fe, Ga), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, magnetic susceptibility, Mössbauer spectroscopy, and (71)Ga NMR spectroscopy. The two compounds are isostructural and crystallize in the monoclinic space group P2(1)/c (No. 14) with a = 8.394(1) A, b = 21.992(3) A, c = 10.847(1) A, beta = 96.188(2) degrees, and Z = 4 for the Fe compound, and a = 8.398(1) A, b = 21.730(3) A, c = 10.679(1) A, beta = 95.318(2) degrees, and Z = 4 for the Ga compound. The structure consists of infinite chains of corner-sharing MX(6) (X = O, F) octahedra and dimers of edge-sharing MO(3)F(3) octahedra, which are linked into two-dimensional sheets through arsenate tetrahedra with diprotonated piperazinium cations between the sheets. Magnetic susceptibility and Mössbauer spectroscopy confirm the presence of Fe(III). The (71)Ga MAS NMR spectrum clearly shows a line shape consisting of three components, corresponding to three crystallographically distinct Ga sites.