Influence of Angular Dicarboxylate Ligand on the Structures of Single and Double Pillared-Layer Coordination Polymers of Co(II)

Two pillared-layer coordination polymeric compounds, namely, [Co₂(bpeb)₂(obc)₂]·DMF·5H₂O (<b>1</b>) and [Co₂(bpeb)­(obc)₂]·2DMF·H₂O (<b>2</b>), have been synthesized using a long dipyridyl spacer ligand (1,4-bis­[2-(4-pyridyl)­ethenyl]­benzene, bpeb), 4,4′-oxybisbenzoate (obc), and Co­(NO₃)₂·6H₂O under solvothermal conditions, using appropriate ratios of Co­(II) to bpeb. In compound <b>1</b>, the double pillared-layer structure has a dimeric repeating unit and exhibits <b>rob</b> topology, while single pillared-layer compound <b>2</b> has an unusual building block which is a linkage isomer of the well-known paddle-wheel structure and has a <b>pcu</b> topology. Twofold and threefold interpenetrations are observed in <b>1</b> and <b>2</b>, respectively. The variable-temperature magnetic properties of <b>1</b> and <b>2</b> were also investigated. The double pillared-layer structure of <b>1</b> exhibits antiferromagnetic behavior while a relatively rare ferromagnetism has been observed for the single pillared-layer structure of <b>2