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

Five novel coordination polymers [Co4(OABDC)2(OH)2(H2O)4]n·(H2O)4.4n (1), [Ni4(OABDC)2(OH)2(H2O)4]n·(H2O)4n (2) (OABDC = 5-oxyacetateisophthalate), [Co2(OABDC)(bpe)(OH)]n·(H2O)2.9n (3), [Zn2(OABDC)(bpe)(OH)]n·(H2O)3.5n (4) (bpe = 1,2-bis(4-pyridyl)ethylene), and [Co2(OABDC)(bpy)(OH)]n·(H2O)2.2n (5) (bpy = 4,4′-bipyridine) have been acquired at similar hydrothermal conditions. All compounds are constructed from tetranuclear [M43-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 M4(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 (43)2.(46.618.84) topologies. Magnetic susceptibility measurements indicate that compound 1 shows strong antiferromagnetic behavior, while 2 exhibits strong ferromagnetic behavior.