Trinuclear copper(II) complexes of bis(acylhydrazone) ligands. Structural analysis and magnetic properties of a sulfato-bridged hexanuclear dimer.

The synthesis and spectroscopic characterization of the new symmetric, O2N2N’2O’2N” ligand bis(salicylaldehyde)methyliminodiacetylhydrazone (H4MeImds) is reported. The reactions of H4MeImds with copper(II) chloride, nitrate and sulfate give trinuclear metal complexes of formula Cu3(MeImds)Cl2 . CHCl3 . H2O, Cu3(MeImds)(NO3)2 . 2H2O and Cu3(MeImds)(SO4) . 8H2O; the trinuclear species are obtained in spite of the used metal:ligand molar ratio. The X-ray crystal structure of [Cu3(MeImds)(SO4)(H2O)3] . 5H2O is determined; it consists of linear units, with the nonadentate ligand bound to three copper ions. The trimetallic units are bridged via sulfate anions to give hexanuclear dimers with an imposed centre of symmetry. The magnetic properties of [Cu3(MeImds)(SO4)(H2O)3] . 5H2O are characterized by a significant antiferromagnetic coupling within the trimetallic units and by a weak antiferromagnetic coupling between them. The analogous trinuclear copper(II) complexes Cu3(HImds)Cl2 . H2O and Cu3(HImds)(SO4) . 4H2O (H5Imds, bis(salicylaldehyde) iminodiacetylhydrazone) were also prepared and spectroscopically characterized.