Beiträge zum Koordinationsverhalten von Oxidionen in anorganischen Feststoffen. III [1] Mn2P2O7, Mn2P4O12 und Mn2Si(P2O7)2 — Kristallzüchtung,Strukturverfeinerungen und Elektronenspektren von Mangan(II)‐Phosphaten |
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Authors: | R. Glaum H. Thauern A. Schmidt M. Gerk |
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Abstract: | Contributions on the Bonding Behaviour of Oxygen in Inorganic Solids. III [1] Mn2P2O7, Mn2P4O12 und Mn2Si(P2O7)2 — Crystal Growth, Structure Refinements and Electronic Spectra of Manganese(II) Phosphates By chemical vapour transport reactions in a temperature gradient single crystals of Mn2P2O7 (1050 → 950 °C) and Mn2P4O12 (850 → 750 °C) have been obtained using P/I mixtures as transport agent. Mn2Si(P2O7)2 was crystallized by isothermal heating (850 °C, 8d; NH4Cl as mineralizer) of Mn2P4O12 und SiO2. In Mn2Si(P2O7)2 [C 2/c, a = 17.072(1)Å, b = 5.0450(4)Å, c = 12.3880(9)Å, β = 103.55(9)°, 1052 independent reflections, 97 variables, R1 = 0.023, wR2 = 0.061] the Mn2+ ions show compressed octahedral coordination (d¯Mn—O = 2.19Å). The mean distance d¯Mn—O = 2.18Å was found for the radially distorted octahedra [MnO6] in Mn2P4O12 [C 2/c, Z = 4, a = 12.065(1)Å, b = 8.468(1)Å, c = 10.170(1)Å, β = 119.29(1)°, 2811 independent reflections, 85 variables, R1 = 0.025, wR2 = 0.072]. Powder reflectance spectra of the three pink coloured manganese(II) phosphates have been measured. The spectra show clearly the influence of the low‐symmetry ligand fields around Mn2+. Observed d—d electronic transition energies and the results of calculations within the framework of the angular overlap model (AOM) are in good agreement. Bonding parameters for the manganese‐oxygen interaction in [Mn2+O6] chromophors as obtained from the AOM treatment (B, C, Trees correction α, eσ, eπ) are discussed. |
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Keywords: | Manganese phosphates Crystal structure Electronic spectra Angular overlap model |
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