Cobalt-cluster-based coordination polymers with size-matching mixed ligands

A series of mixed ligand cobalt coordination polymers built by V-shaped O-donor ligand and linear N-donor ligand, namely [Co(BPE)(L)] (1), [Co-3(BPE)(2)(HL)(2)(L)(2)] (2), and [Co-5(BPE)(2)(OH)(2)(L)(4)]center dot 4DMA (3) (H2L = 4,4'- (hexafluoroisopropylidene)-bis(benzoic acid), BPE = 1,2-di(4-pyridyl) ethane, DMA = dimethylacetamide), was synthesized under hydrothermal/ solvothermal conditions. Compound 1 displays a two-dimensional (2-D) double layer structure of {Co-2} clusters bridged by BPE and L2-ligands. Compounds 2 and 3 exhibit three-dimensional (3-D) networks built by {Co-3} (2) and {Co-5} (3) clusters, respectively, interconnected by BPE and L2- ligands. Topological analysis indicates compound 2 has a doubly interpenetrated (4(12).6(3))-pcu (alpha-Po, 6-connected) network, whereas compound 3 possesses an 8-connected (3(6).4(18).5(3).6)-hex network. It has been found that the reaction media and reaction conditions play key roles for the formation of cobalt clusters in the self-assemblies of compounds 1-3.