Multiple regulated assembly, crystal structures and magnetic properties of porous coordination polymers with flexible ligands

Four novel coordination polymers of Ni-II and Co-II with flexible ligands, namely [Ni(oba)(bpe)](n)(.)nH(2)O (1), [Co(oba)-(bpe) (2), [Ni-2(oba)(2)(bPY)(2)(H2O)(2)](n) -nbpy (3), and [Co(oba)(bpy)1/2](n) (4) [H(2)oba = 4,4'-oxybis(benzoic acid), bpe = 1,2his (4-pyridyl)ethane, bpy = 4,4'-bipyridine] were synthesised by hydrothermal reactions and characterised by single-crystal X-ray diffraction, elemental analysis and IR spectroscopy. The Ni-II ions in complex 1 are linked by flexible oba and bpe ligands to form square-grid-like corrugated sheets. These sheets are interpenetrated with each other, resulting in the formation of a 3D porous network with lattice water molecules in the channels. The variable temperature X-ray diffraction analysis shows that the framework is stable up to 300 degrees C despite the complete removal of the lattice water molecules during the heat treatment. Complex 2 can be re-garded as possessing a alpha-polonium-related topology. Triple interpenetration occurs to form a nonporous structure. In complex 3, the oba and bpy ligands link Ni-II ions into 1D train-like boxes. These boxes are entangled, with the aid of hydrogen bonds, leading to the formation of a 3D porous supramolecular architecture. Free bpy ligands reside in the channels. The Co-II ions in complex 4 are linked by oba and bpy ligands to form a complicated 3D coordination polymer. The lattice water molecules in complex 1 and free bpy ligands in complex 3 can be regarded as templates that play an important role in the formation of the porous structures of complexes 1 and 3. The magnetic properties of complexes 1, 2, and 4 have also been investigated. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).