Synthesis, characterisation and magnetic properties of cobalt(II) complexes with picolinic acid derivatives:: the crystal and molecular structures of [Co(MeC5H3NCOO)2(H2O)2] and [CoCl2(C5H4NCOOPri)2]

The reaction of Co(AcO)(2) with 6-methyl-2-pyridinecarboxylic acid, and that of CoCl2 with the isopropyl ester of 2-pyridinecarboxylic acid, both with a 1:2 metal to ligand molar ratio, afford optimum yields for the synthesis of cis[Co(MeC5H3NCOO)(2)(H2O)(2)] and cis-[CoCl2(C5H4NCOOPri)(2)], respectively. According to X-ray crystallography they both consist of mononuclear discrete molecules with octahedral coordination around Co(II). The ESR powder spectra of the related Zn phases doped with 0.25% Co(II) show the strong anisotropy of the g and A tensors. The magnetic behaviour of the solid complexes is characteristic of Co(II) systems with important spin-orbit coupling and weak antiferromagnetic interactions. Electronic UV-Vis and magnetic data indicate that these complexes, as well as the already known trans-[Co(C5H4NCOO)(2)(H2O)(2)], have a high-spin octahedral geometry in solution. (C) 2003 Elsevier B.V. All rights reserved.