Fe (III) and Ni (II) NANO COMPLEXES OF METRONIDAZOLE; SYNTHESIS, CHARACTERIZATION AND ANTIOXIDADANT STUDIES

Abstract

Metronidazole (MTZ), a nitroimidazole antibiotic widely used for the treatment of anaerobic bacterial and protozoal infections, is increasingly limited by reduced efficacy, toxicity concerns, and emerging microbial resistance. In this study, nano-sized Fe(III) and Ni(II) complexes of MTZ were synthesized via a sonochemical method and characterized using UV–Visible, FTIR, and ¹H NMR spectroscopic techniques, alongside morphological analysis. The complexes were obtained in high yields of 89% for [Fe(MTZ)₂] and 80% for [Ni(MTZ)₂], with distinct colour changes (black and blue, respectively) and melting points of 157 °C and 200 °C, compared to 160 °C for free MTZ, confirming complex formation. FTIR analysis revealed shifts in key vibrational bands, including O–H stretching from 3204 cm⁻¹ to 3190 cm⁻¹ (Ni complex) and its disappearance in the Fe complex, indicating deprotonation, while the C=N band shifted from 1530 cm⁻¹ to 1521–1517 cm⁻¹, confirming coordination through the imidazole nitrogen. ¹H NMR spectra showed corresponding changes, including disappearance of the hydroxyl proton in the Fe(III) complex and slight shifts in aromatic and methyl proton signals. UV–Visible spectra exhibited ligand-centered π→π* transitions at 257 nm shifting to 260 nm (Fe) and 242 nm (Ni), with additional weak d–d transition observed at ~794 nm for the Fe(III) complex, consistent with an octahedral geometry. Transmission electron microscopy revealed nanoscale particles with sizes predominantly in the range of 2.70–5.32 nm, confirming successful nano-complex formation. Antioxidant evaluation using DPPH and FRAP assays showed negligible activity for both MTZ and its complexes, with absorbance values close to zero across concentrations of 25–400 µg mL⁻¹, indicating a lack of significant radical scavenging and reducing power. The results confirm the successful synthesis of nano-sized Fe(III) and Ni(II) metronidazole complexes with modified structural and physicochemical properties. However, these modifications do not translate into enhanced antioxidant activity, suggesting that the complexes may be better suited for applications in drug delivery and nanomedicine rather than as direct antioxidant agents.