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Many pathogenic organisms have developed resistance to many antibiotics, which leads to an increase in the spread of many microbial infections. There is an urgent need to find more effective drugs to curb widespread transmission. Hence, this study synthesized and evaluated the antimicrobial activities of mixed-ligand complexes of Cu(II), Co(II), Ni(II), Mn(II), and Zn(II) ions with barbituric acid and 1,10 phenanthroline ligands in effort to find more effective antibiotics. The complexes were characterized using elemental analysis, metal analysis, melting points, solubility tests, and spectroscopic analyses (IR and UV-visible). The antimicrobial activities of the complexes were evaluated against two gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), two gram-negative bacteria (Pseudomonas aeruginosa and Clostridium spp.), and four pathogenic fungi (Candida albicans, Aspergillus flavus, Aspergillus niger, and Saccharomyces cerevisiae). The biological activities of the metal complexes were compared to the activities of some conventional antibiotics. The molecular formulas for the complexes in 1:1:1 (L-M-L) were established based on the results of the elemental and metal analyses. The IR spectroscopic data results showed the coordination of 1,10-phenanthroline to the metal ions through the nitrogen donor atom, while barbituric acid coordinated with the metal ions through nitrogen and oxygen atoms. The formation of the complexes was confirmed by UV-visible spectroscopic data. Many of the mixed-ligand metal complexes demonstrated higher biological activities than the standard drugs and also succeeded where the conventional antibiotics failed. Therefore, the metal complexes could be considered as more efficacious antibiotics that could be added to the arsenal of effective antibiotics for the prevention of the intrinsic problems of multidrug resistance.
Keywords: Bacteria, Fungi, Ligands, Metal complexes, Multidrug resistance, Barbituric acid