American Chemical Society
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Synthesis and Characterization of Fluorinated Metal Arsenates with a Layer Structure:  (C4H12N2)1.5[M3F5(HAsO4)2(AsO4)] (M = Fe, Ga)

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posted on 2001-09-01, 00:00 authored by Shi-Hao Luo, Yau-Chen Jiang, Sue-Lein Wang, Hsien-Ming Kao, Kwang-Hwa Lii
Two fluorinated metal arsenates, (C4H12N2)1.5[M3F5(HAsO4)2(AsO4)] (M = Fe, Ga), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction, magnetic susceptibility, Mössbauer spectroscopy, and 71Ga NMR spectroscopy. The two compounds are isostructural and crystallize in the monoclinic space group P21/c (No. 14) with a = 8.394(1) Å, b = 21.992(3) Å, c = 10.847(1) Å, β = 96.188(2)°, and Z = 4 for the Fe compound, and a = 8.398(1) Å, b = 21.730(3) Å, c = 10.679(1) Å, β = 95.318(2)°, and Z = 4 for the Ga compound. The structure consists of infinite chains of corner-sharing MX6 (X = O, F) octahedra and dimers of edge-sharing MO3F3 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 71Ga MAS NMR spectrum clearly shows a line shape consisting of three components, corresponding to three crystallographically distinct Ga sites.