The structure and magnetic properties of a 3D pillared-layer polymer and two helical chains constructed from flexible ligands

Three novel coordination polymers of CoII and CuII with flexible ligands, namely [Co(oba)(dpa)]n (1), [Cu(oba)(dpa)]n (2) and [Cu(oba)(bpy)1/2]n (3) [H2oba = 4,4′-oxybis(benzoic acid), dpa = 2,2′-dipyridylamine, bpy = 4,4′-bipyridine] were synthesized by hydrothermal reactions and characterized by single-crystal X-ray diffraction, thermogravimetric analyses, elemental analysis and IR spectroscopy. X-ray diffraction analysis reveals that complexes 1 and 2 are isostructural. In complexes 1 and 2, the CoII and CuII ions are linked by flexible oba ligands to form 1D helical chain. These chains are further assembled into 3D supramolecular edifice via aromatic π-π stacking interactions and intermolecular hydrogen bonding. The CuII ions in complex 3 are linked by the carboxylate groups oba to form an eight-membered ring chains, the connectivity between the corner-shared eight-membered ring chains are further bridged by the bent oba ligands to produce 2D helical layer containing the right-handed helical chains. Furthermore, the adjacent helical layers are connected by bpy pillars to form a novel 3D framework with an unprecedented topology of (315·420·58·62). The magnetic properties of complexes 1-3 have also been investigated.