A new three-dimensional cobalt(II) coordination polymer based on V-shaped 3,4′-oxydibenzoate: synthesis, crystal structure and magnetic properties

Abstract

A new coordination polymer (CP), namely poly[(μ-4,4′-bipyridine)(μ3-3,4′-oxydibenzoato)cobalt(II)], [Co(C14H8O5)(C10H8N2)] n or [Co(3,4′-obb)(4,4′-bipy)] n (1), was prepared by the self-assembly of Co(NO3)2·6H2O with the rarely used 3,4′-oxydibenzoic acid (3,4′-obbH2) ligand and 4,4′-bipyridine (4,4′-bipy) under solvothermal conditions, and has been structurally characterized by elemental analysis, IR spectroscopy, single-crystal X-ray crystallography and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction reveals that each CoII ion is six-coordinated by four O atoms from three 3,4′-obb2− ligands, of which two function as monodentate ligands and the other as a bidentate ligand, and by two N atoms from bridging 4,4′-bipy ligands, thereby forming a distorted octahedral CoN2O4 coordination geometry. Adjacent crystallographically equivalent CoII ions are bridged by the O atoms of 3,4′-obb2− ligands, affording an eight-membered Co2O4C2 ring which is further extended into a two-dimensional [Co(3,4′-obb)] n sheet along the ab plane via 3,4′-obb2− functioning as a bidentate bridging ligand. The planes are interlinked into a three-dimensional [Co(3,4′-obb)(4,4′-bipy)] n network by 4,4′-bipy ligands acting as pillars along the c axis. Magnetic investigations on CP 1 disclose an antiferromagnetic coupling within the dimeric Co2 unit and a metamagnetic behaviour at low temperature resulting from intermolecular π–π interactions between the parallel 4,4′-bipy ligands.