Synthesis, crystal structures, and magnetic properties of two cyano-bridged tungstate(V)-manganese(II) bimetallic magnets

The reaction of manganese acetate with octacyanotungastate in an aqueous solution of concentrated acetic acid gives two new three-dimensional cyano-bridged manganese(II)-tungstate(V) bimetallic assemblies, [Mn-2(II)(H2O)(2)-(CH3COO)][W-v(CN)(8)].2H(2)O (1) (tetragonal space group 14/mcm, a = b = 11.9628(9) Angstrom, c = 13.367(2) Angstrom, and Z = 4) and (CS0.5Mn2II)-Mn-I[W-v(CN)(8)](CH3CO2)(1.5).H2O (2) (monoclinic space group C2/c, a = 16.274(2) Angstrom, b = 22.948(6) Angstrom, c = 13.196(l) Angstrom, beta = 128.040(6)degrees, and Z = 8). In complex 1, W-v(CN)(8) adopts a square antiprismatic geometry, and each CN group coordinates to the Mn-II ions forming W-Mn-4-W-Mn-4- ... columnar linkages where four sites on the Mn-II ion with octahedral geometry are occupied by CN groups. The columns are parallel and interlock, yielding a network structure. Complex 2 contains two different coordination geometries for Wv(CN)8, namely, square antiprismatic and dodecahedral. The columnar structures appear also in 2, where the Mn-II ions in two different environments provide three and four coordinated sites to the CN groups. The columns are bridged by both dodecahedral Wv(CN)8 groups and acetates. Cs ions were intercalated in the lattice by the formation of short attractive contacts with the acetates. The field-cooled magnetization, ac susceptibility, and the field dependence of magnetization measurements show that both 1 and 2 are ferrimagnets with ordering temperatures 40 and 45 K, respectively. The investigation of the magnetostructural correlation shows that the ferrimagnetic ordering in 1 and 2 are attributed to the dominant antiferromagnetic exchange pathways d(z2)(W)-d(xy)(Mn) and d(x2-y2)(W) - d(xy)(Mn).