A Ni(ii) dinuclear complex bridged by end-on azide-N and phenolate-O atoms: spectral interpretation, magnetism and biological study

Abstract

A potential tetradentate monoanionic N₂O₂ chelator, HL, derived from the condensation of o-vanillin and N,N-dimethylethylenediammine, has been reacted with nickel perchlorate and sodium azide to yield the dinuclear Ni(II) complex [Ni(L)(μ_1,1-N₃)Ni(L)(OH₂)₂]·ClO₄ (1), where L = Me₂N(CH₂)₂NCH–C₆H₃(O⁻)(OCH₃). The complex has been characterized by X-ray diffraction analysis and different spectroscopic techniques. The coordination geometry around the Ni(II) centres is a distorted octahedron, with the azide ligand and the phenolato oxygen atom bridging in μ_1,1 and μ₂ mode, respectively. The EPR spectra, recorded at liquid nitrogen temperature (77 K) and room temperature (298 K), show g factors of 2.080 and 2.085, in agreement with the structure determined by X-ray diffraction analysis. The VTM study confirms that there are ferromagnetic interactions between the bridging binuclear Ni(II) ions (S = 1). The evaluation of cytotoxic effects on different human cancer cell lines (A-549, MCF-7 and CaCo-2) suggests that both the ligand and complex 1 have potential anticancer properties. Furthermore, they also exhibit anti-mycobacterial activity against M. tuberculosis H37Rv (ATCC 27294) and M. tuberculosis H37Ra (ATCC 25177) strains. Molecular docking of HL with the enoyl acyl carrier protein reductase of M. tuberculosis H37R_v (PDB ID: 4U0K) has been examined, showing that HL forms two hydrogen bonds with Lys165 (1.94 and 2.53 Å) in its best docked pose.