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

Abstract A new oxamido-bridged vanadium(IV)-oxo complex ligand VOL (H 2 L = 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 (H 2 O) 2 ](ClO 4 ) 2  · 1.5H 2 O ( 2 ) and [Mn(VOL) 2 (CH 3 OH) 2 ](ClO 4 ) 2  · 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 antiferromagnetic interaction is detected in complex 3 . The experiment data have been fitted according to the Heisenberg Hamiltonian H ˆ = - 2 J S ˆ 1 S ˆ 2 , leading to J  = 9.09 cm −1 , zJ ′ = 5.0 × 10 −3  cm −1 for complex 2 and J  = −0.27 cm −1 , θ  = −0.03 K for complex 3 .