Four Cobaltic Coordination Polymers Based on 5-Iodo-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)·3­(H2O)]n (1), [Co2(5-iipa)2(bbi)2·3­(C2H6O2)]n (2), [Co­(5-iipa)­(bbi)·DMF]n (3) (DMF = N,N′-dimethylformamide), and [Co2(5-iipa)2(bbi)2·2DMAc]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···I, I···π, or C–H···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···I
interactions. The adjacent 2D parallel layers in compound 3 deviate from each other with the shift of 3.89 Å 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.