Varying Ligand Backbones for Modulating the Interpenetration of Coordination Polymers Based on Homoleptic Cobalt(II) Nodes

To explore the influence of ligand backbones on the structures of coordination architectures, three structurally related rodlike ligands bearing different backbones, 1,4-bis(benzoimidazol-1-yl)-phenyl (L1), 1,4-bis(imidazol-1-yl)-benzene (L2), and 4,4′-bis(imidazol-1-yl)-biphenyl (L3), have been employed to react with Co(ClO4)2·6H2O, and three three-dimensional interpenetrating coordination polymers, {[Co(L1)2](ClO4)2}∞ (1), {[Co(L2)3](ClO4)2(CHCl3)2}∞ (2), and {[Co(L3)3](ClO4)2}∞ (3), have been obtained under similar conditions. Compound 1 forms a 3-fold interpenetrating network with diamondoid topology based on a tetrahedrally coordinated CoII node, whereas complex 2 takes a double interpenetrating network with α-polonium-type topology and compound 3 exhibits a 3-fold interpenetrating network with β-Sn topology. Compared with the tetrahedrally coordinated CoII node in compound 1, the CoII nodes in compounds 2 and 3 are both octahedrally coordinated. To the best of our knowledge, the 3-fold interpenetrating network of compound 3 is the first example of β-Sn 485463 topology in coordination polymers. Our results reveal that ligand backbones (including terminal groups and spacer conformations) may be the major influence on the structure topology of coordination architectures, and significantly, the coordination mode and spacer length play important role in controlling the degree of interpenetration of coordination polymers.