Synthesis and studies of rare acylhydrazine bridged strong antiferromagnetically coupled dicopper(II) and dioxovanadium(V) complexes of a pyridyl-pyrazole derived Schiff base ligand

A binuclear acylhydrazine bridged Cu(II) complex, [Cu-2(L)(NO3)(3)(H2O)] (1), and an anti-orthogonal binuclear oxovanadium(V) complex, [V2O4(L)(2)] (2), have been synthesized and characterized spectroscopically and crystallographically. The ligand HL has two potentially bridging functional groups (mu-O, mu-N-N) and consequently can exist in the following coordination conformers: (a) metal centers bridged by mu-O, (b) metal centers bridged by mu-N-N. A rare acylhydrazine bridged (a) type configuration exists in the dinuclear Cu(II) complex 1. The bridging ligand mediates a strong antiferromagnetic coupling (J = -99 cm(-1)). The exchange pathway parameters have also been evaluated from density functional theoretical calculations to corroborate the bridging signatures with experimental findings (J = -93.96 cm(-1)). Molecule 2 has a centrosymmetric structure with each vanadium center having a distorted octahedral geometry. It shows a one step irreversible reduction at +0.43 V. The bond angles, bond lengths and torsion angles in 2 are correlated with DFT. (C) 2012 Elsevier Ltd. All rights reserved.