Synthesis and characterization of the manganese pyroarsenate Mn2As2O7 center dot 2H(2)O

The manganese pyroarsenate hydrate, Mn2As2O7. 2H(2)O, has been obtained as a single phase product using hydrothermal methods and the structure has bee n determined by single crystal X-ray diffraction. The title compound crysta llizes in the monoclinic space group P2(1)/n with a = 6.6576(4), b = 14.555 (1), c = 7.8147(5) Angstrom, beta = 94.935(1)degrees, V = 754.46(8) Angstro m (3) and Z = 4. The manganese ions are each coordinated to five oxygen ato ms and a water molecule in a distorted octahedral arrangement. Edge-sharing MnO6 octahedra form chains which are connected to a three-dimensional fram ework by As2O74- ions. The pyroarsenate anion, which attains a nearly eclip sed conformation, has a mean As-O distance for the terminal As-O bonds of 1 .669(2) Angstrom, while for the bridging oxygen atom a mean value of 1.757( 2) Angstrom is observed. Magnetic susceptibility measurements indicate the presence of high-spin Mn2+ ions. Thermogravimetric as well as IR and Raman spectroscopic studies of Mn2As2O7. 2H(2)O are presented.