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.