Synthesis, characterization and crystal structures of oxidovanadium(V) complexes derived from hydrazone ligands with antibacterial activity

A pair of new oxidovanadium(V) complexes, [VOL¹(OEt)(EtOH)] (1) and [VOL²(OEt)] (2), where L¹ and L² are the dianionic form of 3-fluoro-<i>N’</i>-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (H₂L¹) and 4-bromo-<i>N’</i>-(2-hydroxy-3-methoxybenzylidene)benzohydrazide (H₂L²), respectively, were prepared and characterized by elemental analysis, infrared and electronic spectra, and ¹H NMR spectra. Structures of the complexes were further confirmed by single crystal X-ray determination. The V atom in complex 1 is in octahedral coordination, and that in complex 2 is in square pyramidal coordination. Both hydrazone ligands coordinate to the V atoms through the phenolate O, imino N, and enolate O atoms. In complex 1, one ethanol and one deprotonated ethanol ligands coordinate to the V atom, while in complex 2, only one deprotonated ethanol ligand coordinates to the V atom. The complexes show effective antibacterial activity against <i>Bacillus subtilis</i>. Complex 1 has the most active activity against <i>B. subtilis</i>, with IC₅₀ value of 1.77 µg mL⁻¹, which is comparable to that of Penicillin G.