Greenly Synthesized Ni(II) Schiff Base Complexes with Enhanced Broad-Spectrum Antimicrobial Activity: Mechanistic Insights and Potential Applications.

Metal-based complexes have garnered significant interest as potential candidates for broad-spectrum antimicrobial applications. This study presents the synthesis of two Ni(II) Schiff base complexes, denoted as NiSBC1 and NiSBC2, utilizing microwave-assisted irradiation - a method recognized for its environmental benefits. The complexes were extensively characterized using FT-IR, UV–Visible spectroscopy, SEM, elemental analysis, and thermogravimetric analysis, all confirming the successful formation of stable chelated structures. The synthesized complexes were evaluated for antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria, fungi, and algae. Both NiSBC1 and NiSBC2 exhibited pronounced broad-spectrum antimicrobial activity. Notably, stronger antibacterial effects were observed against Gram-positive bacteria such as Staphylococcus aureus and Bacillus subtilis, compared to Gram-negative bacteria like Escherichia coli and Pseudomonas aeruginosa. This difference in activity may be attributed to variations in the composition of the cell walls that influence the penetration of the metal complexes. Furthermore, the complexes demonstrated significant antifungal activity against Aspergillus niger and effective anti-algal activity toward Chlorella vulgaris. Overall, the findings underscore the significant potential of NiSBC1 and NiSBC2 as broad-spectrum antimicrobial agents with prospective applications in pharmaceutical and environmental disinfection fields. They also highlight the crucial role of metal-ligand coordination in enhancing biological activity