Synthesis, Characterization, Biological Evaluation, and Computational Study of Mo(VI) Complexes Derived from Hydrazone Schiff Base Ligands

The growing challenge of bacterial resistance to antibiotics and the rising threat of oxidative stress emphasize the urgent need for versatile therapeutic agents to combat these intertwined issues effectively. This study focuses on the synthesis of hydrazone Schiff bases (L1-L4) through the condensation reaction of salicylaldehyde and its halogen derivatives (─Cl, ─Br, and ─I) with benzohydrazide. These ligands were then complexed with MoO₂(acac)₂ to yield Mo(VI) complexes. Various spectroscopic and analytical techniques were employed to structurally characterize the ligands and their resulting complexes. The analysis revealed that the ligands acted as tridentate bi-negative, coordinating with Mo(VI) through ONO donor atoms, forming heteroleptic mononuclear complexes (C1–C4) of the composition [MLn(X)], where M = Mo, n = 1, 2, 3, or 4, and X = CH₃OH. The solid-state structure of C1 was elucidated through single crystal X-ray diffraction, confirming the proposed coordination mode of the ligands. Subsequently, the antibacterial and antioxidant activities of the compounds were assessed through in vitro screening against Gram-positive and Gram-negative bacteria and the DPPH assay. The results show that the compounds exhibited moderate to high antibacterial and radical scavenging capabilities. In particularly, complexes bearing chlorine and iodine substituents, demonstrating low MIC values with IC₅₀ values ranging from 1.35 to 2.38 mg/mL, surpassing that of the standard antioxidant, ascorbic acid (2.48 mg/mL). To delve deeper into the electronic properties of the compounds and their mechanism of action against specific receptors, DFT calculations and molecular docking studies were conducted. The results obtained corroborated with experimental findings, and provide differ understanding into the electronic properties and binding mode against the receptors.