Four Cobaltic Coordination Polymers Based on 5-lodo-Isophthalic Acid: Halogen-Related Interaction and Solvent Effect

A series of four novel cobaltic coordination polymers based on 5-iodo-isophthalic acid (5-iipa) and 1,1'-(1,4-butanediyl)bis(imidazole) (bbi), namely, [Co(5-iipa)(bbi)center dot 3(H2O)](n) (1), [Co-2(5-iipa)(2)(bbi)(2)center dot 3(C2H6O2)](n) (2), [Co(5-iipa)(bbi)center dot DMF](n) (3) (DMF = N,N'-dimethylformamide), and [Co-2(5-iipa)(2)(bbi)(2)center dot 2DMAc](n) (4) (DMAc = N,N'-dimethylacetamide) have been solvothermally synthesized by using various solvents. Their thermal analysis, XRD and UV-vis absorption spectra have been investigated as well. Structural analyses exhibit that they all form 2D covalent structures based on the intersection of Co-5-iipa and Co-bbi chains, and adjacent layers are parallel and united together to yield a 3D supramolecular structure through interlayer I center dot center dot center dot I, I center dot center dot center dot pi, or C-H center dot center dot center dot O interactions, respectively. More interestingly, channels are detected in the architectures, which are mainly occupied by the guest solvent molecules. Compound 1 features a rare 3-fold interpenetrating 3D supramolecular architecture, while compound 2 exhibits an interesting 3-fold parallel interpenetrated two-dimensional (2D) -> three-dimensional (3D) network motifs based on I center dot center dot center dot I interactions. The adjacent 2D parallel layers in compound 3 deviate from each other with the shift of 3.89 angstrom along the b or - b axis. Compound 4 shows a double layer structure in which the bbi-Co waving-like ribbon is running along the c-axis. Results demonstrate that both halogen-related interaction and solvent effect play important roles in the assembly of the supramolecular metal-organic networks.