Synthesis and Characterization of the New Mixed Valent Compound Mn5VO8

This work describes the synthesis and characterization of the new compound Mn5VO8. This phase is the only known ternary mixed valent compound in the system MnO-Mn2O3-V2O5 and crystallizes in a so far unknown crystal structure, which leads to coordination for the Jahn-Teller cation Mn3+ in distorted octahedra (elongated and compressed, respectively). The material can be prepared by solid state reaction at 900 degrees C in a monoclinic [a = 19.5605(10) angstrom, b = 6.2184(3) angstrom, c = 5.4276(3) angstrom, beta = 100.078(4)degrees, C2/m, Z = 4] as well as in a triclinic [a = 5.4320(2) angstrom, b = 6.2066(2) angstrom, c = 10.2443(4) angstrom, a = 107.035(3)degrees, beta = 99.469(3)degrees, ? = 90.422(4)degrees, P$\bar{1}$, Z = 2] modification, depending on the composition of the starting material mixture (7MnO + V2O5 versus 0.5Mn2O3 + 4MnO + 0.5V2O5). Quantum mechanical calculations were carried out in order to get more detailed information on the material. Thereby, ionic charges could be assigned to the manganese atoms at the different crystallographic sites.