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, [Cu2(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 (μ-O, μ-N–N) and consequently can exist in the following coordination conformers: (a) metal centers bridged by μ-O, (b) metal centers bridged by μ-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.

Graphical abstractSynthesis of uncommon acylhydrazine mediated strong antiferromagnetically coupled dinuclear copper(II) and anti-orthogonal binuclear oxovanadium(V) complexes of a pyridyl-pyrazole derived Schiff base ligand: crystal structures, spectroscopic, electrochemical, magnetic and DFT studies.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Crystal structure of acylhydrazine bridged copper(II), and μ2-dioxo bridged vanadium(V) complexes. ► Infrared spectroscopy, electronic spectra. ► Magnetic properties, cyclic voltammetry. ► DFT studies.