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

Abstract

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), [Co₃(BPE)₂(HL)₂(L)₂] (2), and [Co₅(BPE)₂(OH)₂(L)₄]·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 {Co₂} clusters bridged by BPE and L²⁻ ligands. Compounds 2 and 3 exhibit three-dimensional (3-D) networks built by {Co₃} (2) and {Co₅} (3) clusters, respectively, interconnected by BPE and L²⁻ ligands. Topological analysis indicates compound 2 has a doubly interpenetrated (4¹²·6³)-pcu (α-Po, 6-connected) network, whereas compound 3 possesses an 8-connected (3⁶·4¹⁸·5³·6)-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.