Synthesis, spectroscopic characterization and antimicrobial studies of oxovanadium(IV) complexes with substituted acetylacetones and pyridines.

Monomeric six-coordinated adducts of 1,5-disubstituted bis(acetylacetonato) oxovanadium (IV) complexes having the general formula [VO(RCOCH₂COR')₂(L)] [where R = CH₃, (CH₃)4; R' = CF₃, (C4H3S); and L = 4-methylpyridine or 3-amino-4-hydroxypyridine] were synthesized. The adducts with 4-methylpyridine and 3-amino-4-hydroxypyridine were successfully synthesized and isolated. The Oxovanadium (IV) complexes were characterized using molar conductance, magnetic susceptibility, mass spectrometry, ESR spectroscopy, powder X-ray diffraction techniques, IR, UV-Visible, Conductivity and analytical studies validated a 1:2 metal-to-ligand stoichiometry, supporting the predicted coordination environment. The adducts were found to be paramagnetic, with magnetic moment values at room temperature lying in the range of 1.68-1.79 BM, confirming the presence of one unpaired electron. These values are consistent with an octahedral geometry around the vanadium (IV) centre. Spectroscopic data, along with magnetic measurements, strongly indicate a monomeric octahedral geometry around the vanadium (IV) ion. The synthesized complexes were evaluated for antimicrobial activity against selected Gram-positive and Gram-negative bacteria as well as fungal strains using the paper disc method (Kirby-Bauer method). The results revealed that the metal complexes exhibited enhanced antimicrobial activity compared to the free ligands, suggesting the role of metal coordination in improving biological activity. Oxovanadium (IV) -based antimicrobial agents with increased ability and specificity against resistant pathogens due to the chelation effect, which facilitates improved lipophilicity and increased interaction with microbial cell membranes. These observations highlight the strenth of oxovanadium (IV) complexes as potential bioactive agents for further pharmacological studies.