Synthesis, crystal structures and urease inhibition of two methoxido(methanol)oxovanadium(V) acylhydrazone complexes

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Two mononuclear oxovanadium(V) complexes, [VOL¹(OCH₃)(CH₃OH)] (1) and [VOL²(OCH₃)(CH₃OH)] (2), where H₂L¹ = N'-(3-bromo-5-chloro-2-hydroxybenzylidene)-2,3-dimethoxybenzohydrazide and H₂L² = N'-(3-bromo-5-chloro-2-hydroxybenzylidene)-2-methylbenzohydrazide, were synthesized and characterized by elemental analysis, IR, UV–Vis and ¹H NMR spectroscopy, and single crystal X-ray diffraction. In both complexes, the acylhydrazone ligand adopts a doubly deprotonated tridentate O,N,O coordination mode, and the vanadium(V) center exhibits a distorted octahedral geometry completed by terminal oxido, methoxido, and methanol ligands. The crystal structures reveal closely related coordination environments, while the different acyl substituents are associated with variations in selected V–O bond lengths and intermolecular hydrogen-bonding interactions. Both complexes exhibit pronounced urease inhibitory activity, with IC₅₀ values of 5.7 ± 1.2 μM for 1 and 7.3 ± 1.5 μM for 2, compared with 33 ± 2 μM for acetohydroxamic acid and >100 μM for VO(acac)₂ under the same assay conditions. The structural and biological results provide further information on the coordination chemistry and urease-inhibitory behavior of oxovanadium(V) acylhydrazone complexes. The reported IC₅₀ uncertainties overlap, so a statistically significant difference between the two complexes has not been demonstrated.