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-N’-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (H2L1) and 4-bromo-N’-(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 Bacillus subtilis. Complex 1 has the most active activity against B. subtilis, with IC50 value of 1.77 µg mL−1, which is comparable to that of Penicillin G.