A macrocyclic oxamido vanadium(IV)-oxo ligand and its derivative VOIV 2MII (M = Cu, Mn) trinuclear complexes: synthesis, structures and magnetic properties

A new oxamido-bridged vanadium(IV)-oxo complex ligand VOL (H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) (1) has been synthesized. Based on the mononuclear ligand, two trinuclear complexes [Cu(VOL)(2)(H2O)(2)](ClO4)(2) center dot 1.5H(2)O (2) and [Mn(VOL)2-(CH3OH)(2)](ClO4)(2) center dot 5CH(3)OH (3) have been prepared and structurally characterized by X-ray crystallography. In complexes 2 and 3, the central ions Cu(II) and Mn(II) are connected to two VOL fragments via an exo-cis oxamido bridge. Magnetic susceptibility studies (2-300 K) indicate the occurrence of ferromagnetic coupling between the paramagnetic metals in complex 2, while a weak anti ferromagnetic interaction is detected in complex 3. The experiment data have been fitted according to the Heisenberg Hamiltonian H=-2jS(1)S(2), leading to J=9.09 cm(-1), zj'=5.0 x 10(-3) cm(-1) for complex 2 and J = -0.27 cm(-1), O = -0.03 K for complex 3. (C) 2008 Elsevier Ltd. All rights reserved.