Co(II)-promoted transformation of diethyl(quinolin-2-ylmethyl)phosphonate to quinoline-2-carboxylate (2-qca):: Synthetic, structural and magnetic studies of [Co(2-qca)2(EtOH)2]

The interaction of the dietliyl(quinolin-2-ylmethyl)phosphonate (2-qmpe) ligand with COCl2 center dot 2H(2)O unexpectedly leads to the formation of a compound with the formula [Co(2-qca)(2)(EtOH)(2)] (2-qca = quinoline-2-carboxylate). This compound is a product of the oxidative cleavage of the C-P bond in 2-qmpe and the formation of the 2-qca ligand. The title compound was characterized by infrared, ligand field, EPR spectroscopy and low temperature magnetic (1.8-300 K) studies. Particularly, the crystal and molecular structures were determined by the X-ray diffraction. The CoN2O4 chromophore shows an elongated octahedron geometry, resulting from the two didentate N,O-bonded chelate ligands and two ethanol molecules - quinolil nitrogen atoms are located in axial positions and oxygen atoms are positioned in the basal plane. The crystal packing is due to hydrogen bonds and pi-pi stacking interactions, which give rise to a three-dimensional (3D) polymeric network. The magnetic properties reflect the molecular character of the compound, with a very weak magnetic exchange interaction. The moments are enhanced due to an important orbital contribution via spin-orbit coupling. (C) 2008 Elsevier Ltd. All rights reserved.