Crystal structure and magnetic properties of two metal-picolinate systems obtained from degradation of bis(2-pyridylketone) through reaction with Mn(II) and Cu(II)

The bis(2-pyridyl-ketone) compound is expected to have great potential as a multidentate ligand with transition metals. However, similar ketone-containing compounds, bis(2-pyridyl-ketone) could undergo metal-promoted hydration. With the aim of determining its behaviour, bis(2-pyridyl-ketone) was reacted with Cu(II) and Mn(II). X-ray characterisation of the products reveals the formation of complexes containing picolinate anions as products of the degradation of bis(2-pyridyl-ketone). ESR spectroscopy for the compound with Mn(II) (1) indicates an important zero-field splitting term originating from the strong distortion of the resulting Mn(II) octahedra. The ESR spectra for the compound with Cu(II) (2) are consistent with the elongated Cu(II)-octahedra. These octahedra form a monodimensional arrangement which shows the occurrence of antiferromagnetic exchange couplings. (C) 1999 Elsevier Science Ltd. All rights reserved.