The 3D supramolecular architecture of copper(II) 6-methyl-2-pyridone-4-carboxylate: synthesis, structure, magnetic behavior and DFT studies

Abstract

Abstract The reaction of Cu(NO3)2·3H2O and 6-methyl-2-pyridone-4-carboxylic acid (Hhmpca) under hydrothermal condition produced a new copper(II) coordination polymer [Cu(hmpca)2(H2O)2]·4H2O (1), which has been characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis and single-crystal X-ray diffraction. The Cu(II) ions are linked by coordinating water molecule bridges to generate a polymeric chain, and adjacent chains are connected to form a layer structure through interchain N–H···O hydrogen bonding. Because of the strong hydrogen bonds of free water molecules, ladder-shaped water chains are produced. Further, the layers and the water chains are linked into a three-dimensional supramolecular structure through strong O–H···O hydrogen bonds. Magnetic susceptibility measurements have indicated that compound 1 shows antiferromagnetic interactions between the adjacent Cu(II) ions. Based on the crystal structure data, compound 1 was analyzed using hybrid density functional theory (DFT) methods at the B3LYP/6-31G(d) level, and a DFT-broken symmetry approach was applied to study the magnetic coupling behavior. The calculated exchange coupling constant J is in good agreement with the experimental data.