Synthesis, Characterization, and Antioxidant/Antibacterial Activities of New Mono- and Bi-Nuclear Complexes of Zn(II), Cu(II), and Co(II) Based on the Ligand 4-(benzo[d]thiazol-2-yl)-N, N-dimethylaniline

Abstract

New mono- and bimetallic copper, zinc, and cobalt complexes derived from the ligand 4-(benzo[d]thiazol-2-yl)-N, N-dimethylaniline (L) were successfully synthesized and characterized using UV-visible, FT-IR, 1H-NMR, 13C-NMR, mass spectrometry, and molar conductance measurements. The molar conductance data confirmed that all synthesized complexes are non-electrolytes. Spectroscopic analyses indicated that the ligand coordinates with the metal ions in a monodentate fashion through its nitrogen atom. The antioxidant activity of the ligand and its metal complexes was tested using the DPPH assay, revealing that complexation significantly enhanced radical scavenging ability. The Cu(II) complex exhibited the strongest activity with an IC₅₀ value of 0.008 ± 0.005 mg/mL, followed by Co(II) (0.014 ± 0.003 mg/mL), Zn(II) (0.024 ± 0.007 mg/mL), and the free ligand (0.043 ± 0.004 mg/mL), compared to ascorbic acid (0.046 ± 0.003 mg/mL). Antibacterial screening using the well-diffusion method on agar demonstrated that the metal complexes had greater inhibitory activity than the free ligand, particularly against Staphylococcus aureus and Pseudomonas aeruginosa, with minimum inhibitory concentration (MIC) values ranging from 0.25 to 1.0 mg/mL. Overall, this study reports the successful synthesis and comprehensive characterization of benzothiazole-based Schiff base metal complexes with markedly improved antioxidant and antibacterial properties, highlighting their potential as promising candidates for further pharmacological investigations.