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 (1) and [Co2(bpeb)­(obc)2]·2DMF·H2O (2), 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 1, the double pillared-layer structure has a dimeric repeating unit and exhibits rob topology, while single pillared-layer compound 2 has an unusual building block which is a linkage isomer of the well-known paddle-wheel structure and has a pcu topology. Twofold and threefold interpenetrations are observed in 1 and 2, respectively. The variable-temperature magnetic properties of 1 and 2 were also investigated. The double pillared-layer structure of 1 exhibits antiferromagnetic behavior while a relatively rare ferromagnetism has been observed for the single pillared-layer structure of 2.