Two New Mixed-Valence Iron Phosphates Templated by Piperazine: (C4H12N2)[Fe4(OH)2(HPO4)5] and (C4H11N

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• 作者：Ví ; tezslav Zima ; Kwang-Hwa Lii ; Ninh Nguyen ; and Annie Ducouret
• 刊名：Chemistry of Materials
• 出版年：1998
• 出版时间：July 1998
• 年：1998
• 卷：10
• 期：7
• 页码：1914 - 1920
• 全文大小：272K
• 年卷期：v.10,no.7(July 1998)
• ISSN：1520-5002

文摘

Two piperazine-templated iron phosphates, (C₄H₁₂N₂)[Fe₄(OH)₂(HPO₄)₅] (1) and (C₄H₁₁N₂)_0.5[Fe₃(HPO₄)₂(PO₄)(H₂O)] (2), have been synthesized under solvothermal conditions andcharacterized by single-crystal X-ray diffraction, Mössbauer spectroscopy, and thermogravimetric analysis. Compound 1 crystallizes in the monoclinic space group C2/m (no. 12) witha = 25.706(3), b = 6.4492(6), c = 6.3790(6) Å, ges/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 102.601(2)ges/entities/deg.gif">, V = 1032.0(3) ų and Z = 2.The 3-D framework structure consists of layers of iron phosphate which are pillared throughHPO₄ groups to generate intersecting 8-ring channels with piperazinium dications at theintersections of these channels. Each layer contains infinite chains of edge-sharing Fe^IIO₆octahedra which are connected to each other via corner-sharing Fe^IIIO₆ octahedra and HPO₄groups. Compound 2 crystallizes in the monoclinic space group C2/c (no. 15) with a =30.8924(4), b = 6.3733(1), c = 12.5552(2) Å, ges/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 101.946(1)ges/entities/deg.gif">, V = 2418.41(7) ų, and Z = 8.The compound has a layered structure with piperazinium monocations in the interlayerspace. Each layer consists of a dimer of edge-sharing octahedra with the composition Fe^IIFe^IIIO₁₀ which shares edges with four Fe^IIO₅ trigonal bipyramids to form a hexamer as thebuilding unit. Each such hexamer is connected to others by corner sharing and throughphosphate groups. Both compounds are mixed-valence as indicated from bond valencecalculations, Mössbauer measurements, and electric field gradient calculations.