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Abstract In this study, benzoyl isothiocyanate was first obtained by the reaction of benzoyl chloride with ammonium thiocyanate. The ligand N-(2-amino-5-methylpyridine)-N′-benzoylthiourea (HL) was then synthesized by condensing benzoyl isothiocyanate with 2-amino-5-methylpyridine. Subsequently, mixed-ligand metal(II) complexes were prepared by reacting HL with L-phenylalanine or L-alanine in the presence of copper(II) or zinc(II) acetate dihydrate salts. The HL ligand was characterized by elemental analysis, FT-IR, 1 H and 13 C NMR spectroscopy. The metal complexes were characterized by elemental analysis, FT-IR, molar conductivity, magnetic susceptibility, and thermal analysis, supported by DFT calculations. Among the complexes, complex ZnL(phe)(H 2 O) 2 (2) stood out due to its high stability, low toxicity (LD 50 =3200 mg/kg, toxicity class 5), and favorable ADMET profile. Molecular docking studies against lipoteichoic acid synthase (2W5T, Gram-positive) revealed that complex ZnL(phe)(H 2 O) 2 (2) exhibited a strong binding affinity, with a docking score of -9.7 kcal/mol. This in silico finding was consistent with the in vitro antibacterial results, where complex ZnL(phe)(H 2 O) 2 (2) showed the highest zone of inhibition (16 mm) against Staphylococcus aureus. Complex CuL(phe)(H 2 O) 2 (1) demonstrated superior antioxidant activity, with an IC₅₀ value of 6.91 µg/mL in the ABTS assay, outperforming the reference antioxidants. Complexes CuL(Ala)(H 2 O) 2 (3) and CuL 2 (H 2 O) 2 (4) exhibited potent antibacterial activity against Pseudomonas aeruginosa, with MIC values of 256 µg/mL. These results demonstrate that varying the metal center and co-ligand in mixed-ligand complexes can yield distinct bioactivity profiles, from potent antioxidant effects to targeted antibacterial action.
Qebchaq et al. (Mon,) studied this question.