Synthesis, crystal structures, and magnetic properties of two three-dimensional octacyanotungstate(IV)- based bimetallic frameworks with 4,4'-bipyridine dioxide (4,4'-dpdo)

The reaction of [HN(n-C4H9)3]3[WV (CN)8]·4H2O, 4,4′-bipyridine dioxide(4,4′-dpdo), and MnCl2·4H2O or CuCl2·2H2O gives two new three-dimensional octacyanometalate-based bimetallic assemblies, {[Mn2 (4,4′-dpdo)(H2O)4] [WIV (CN)8]{·6H2O (1) and {[Cu2(4,4′-dpdo)(H2O)][W(CN)8]{·CH3OH·H2O (2). Compound 1 crystallizes in the orthorhombic system, space group P21212 with cell constants α=10.397(2) A, b=11.321(2) A, c=12.295(3) A and Z=2, whereas 2 crystallizes in the monoclinic system, space group P21/c with cell constants a=13.038(3) A, b=13.784(3) A, c=13.225(3) A, β=93.44(3)° and Z=4. In complex 1, each [WIV (CN)8]4− unit with a square antiprismatic geometry is connected to four Mn2 dimers through four bridging CN− ions forming wavelike alternating-W-Mn2-W-Mn2- layers, which are further linked through 4,4′-dpdo ligands coordinated to the Mn ions into a three-dimensional open framework. In complex 2, each [WIV (CN)8]4− ion still adopts a square antiprismatic geometry, whereas it bonds to seven copper ions through seven CN− ions leading to cage-like undulate layers further bridged by 4,4′-dpdo ligands into a three-dimensional network. Due to the bridging role of the long rigid 4,4′-dpdo ligand, there exist plenty of large cavities in the open frameworks of complexes 1 and 2 occupied by solvent clusters containing H2O or CH3OH molecules. To our knowledge, it is noted that 4,4′-dpdo displays a μ-4,4,4′,4′ mode, which was first experimentally observed, although predicted before. Magnetic studies show that complex 1 displays an antiferromagnetic coupling between MnII ions, while complex 2 exhibits a weak ferromagnetic interaction between CuII ions.