Two metal coordination polymers with general formula [M(dpa)(C 4O4)(H2O)] [M = Co (1), Ni (2), Zn (3); dpa = 2,2′-dipyridylamine] and [Cu(dpa)(C4O4)(H 2O)]2·H2O (4) have been synthesized under hydrothermal conditions. The single-crystal X-ray analyses reveal that compounds 1-3 are isostructural and possess distorted octahedral metal centers coordinated by two squarates, one dpa, and two water molecules. A 1D two-legged ladder-like framework is formed by interconnection of the water-bridged [M(dpa)(μ2-OH2)]24+ dimeric fragments and μ1,2-squarate ligands. Intra- and intermolecular hydrogen bonds between squarate, water, and dpa ligands, as well as the π-π stacking interaction of the pyridyl ring in the dpa ligands, provide extra forces to stabilize the extended network. Conversely, the molecular structure of compound 4 contains two distorted square-pyramidal CuII centers coordinated by two squarates, one dpa ligand, and one water molecule. The squarates adopt a μ1,2-binding mode to link the Cu centers and form a 1D helical chain. For compound 2, the magnetic exchange couplings between metal centers are analyzed with a binuclear magnetic model. The resulting negative magnetic exchange coupling constant indicates an antiferromagnetic interaction within the dimers. The magnetic behavior of compound 4 is typical of paramagnetic CuII ions.
All Science Journal Classification (ASJC) codes
- Inorganic Chemistry