One-dimensional helical coordination polymers of cobalt(II) and iron(II) ions with 2,2′-bipyridyl-3,3′-dicarboxylate (BPDC2−)

One-dimensional (1-D) helical coordination polymers, [MII(H2O)3(BPDC)]n · nH2O (M = Co (1), Fe (2)), have been prepared by the self-assembly of cobalt(II) and iron(II) ions, respectively, with 2,2′-bipyridyl-3,3′-dicarboxylic acid (H2BPDC) in an aqueous solution. X-ray crystal structures of compounds 1 and 2 show that each metal ion displays a distorted octahedral coordination geometry including three water oxygen atoms, one oxygen atom of the carboxylate of a BPDC2− belonging to the adjacent metal ion and two nitrogen atoms from the BPDC2− acting as a chelating ligand. In 1 and 2, one carboxylate oxygen atom of coordinated BPDC2− binds to the neighboring metal ion, which give rise to 1-D helical coordination polymers. The helical chains of 1 and 2 are linked by the hydrogen bonding interactions between the carboxylate oxygen atom of the BPDC2− ion belonging to a chain and the water molecule of the adjacent helical chain, which lead to 2-D networks extending along the ab plane. The supramolecules 1 and 2 show isomorphous structures regardless of the metal ions.

Graphical abstractThe reaction of 2,2′-bipyridyl-3,3′-dicarboxylic acid (H2BPDC) and metal ions [Co(II) and Fe(II)] in an aqueous solution forms 1-D helical coordination polymers of [CoII(H2O)3(BPDC)]n · nH2O (1) and [FeII(H2O)3(BPDC)]n · nH2O (2), respectively. Compounds 1 and 2 show 1-D helical structures by the metal–ligand coordination between the cobalt(II) or iron(II) ion and BPDC2−. The helical chains of 1 and 2 are linked by the hydrogen bonding interactions, which give rise to 2-D networks.Figure optionsDownload full-size imageDownload as PowerPoint slide