Construction of Metal-Organic Frameworks with Tetranuclear Metal Clusters: Hydrothermal Synthesis, Structure, and Magnetic Properties

Five novel coordination polymers [Co-4(OABDC)(2)(OH)(2)(H2O)(4)](n)center dot(H2O)(4.4n) (1), [Ni-4(OABDC)(2)(OH)(2)(H2O)(4)](n)center dot(H2O)(4n) (2) (OABDC = 5-oxyacetateisophthalate), [Co-2(OABDC)(bpe)(OH)](n)center dot(H2O)(2.9n) (3), [Zn-2(OABDC)(bpe)(OH)](n)center dot(H2O)(3.5n) (4) (bpe = 1,2-bis(4-pyridyl)ethylene), and [Co-2(OABDC)(bpy)(OH)](n)center dot(H2O)(2.2n) (5) (bpy = 4,4'-bipyridine) have been acquired at similar hydrothermal conditions. All compounds are constructed from tetranuclear [M-4(mu(3)-OH)(2)] (M = Co for 1, 3, and 5, Ni for 2, Zn for 4) clusters. Compounds 1 and 2 are isomorphous, in which the M-4(OH)(2) units act as 6-connected nodes and the frameworks are two-dimensional (2D) (3,6)-connected nets with the rare CdI2 type. If considering the strong H-bond interactions between neighboring layers, both exhibit three-dimensional (3D) microporous networks with channels running along the [100] direction. Complexes 3 and 4 are also isomorphous, in which the 2D CdI2-based layer was pillared by bpe spacers; thus channels occur along the [100] direction. While adopting bpy instead of the bpe ligand, smaller channels are observed along the [100] direction for 5. The last three compounds all feature 3D networks with one of the scarce (3,8)-connected (4(3))(2)center dot(4(6)center dot 6(18)center dot 8(4)) topologies. Magnetic susceptibility measurements indicate that compound 1 shows strong anti ferromagnetic behavior, while 2 exhibits strong ferromagnetic behavior.