Copper(II), cobalt(II), nickel(II), and iron(II) mixed complexes formed by Schiff base and 1,10-phenanthroline as secondary chelates: Preparation, characterization, antimicrobial, antioxidant, and molecular docking studies

This study details the synthesis and characterization of new metal complexes formed by combining 2-((2-mercaptophenylimino)methyl)-4-methoxy-6-nitrophenol (L1) and 1,10-phenantroline (L2) ligands. The ligand (L1) and its mixed-ligand complexes with Co (II), Cu (II), Fe (II), and Ni (II) salts was analyzed using elemental analysis, FT-IR, UV–Vis, mass spectrometry, 1H and 13C NMR, magnetic susceptibility, and molar conductivity studies. The development of non-electrolytic compounds in a 1:1:1 M (L1:M:L2) ratio was verified by elemental analysis and conductance measurements. The complexes displayed an octahedral configuration. Biological uses of newly synthesized complexes were suggested by their antibacterial and antioxidant properties. Especially, the Fe (II) complex exhibited higher antimicrobial activity than free ligand on all the tested microbial strains according to the results of agar disc difffusion assay (inhibition zones ranging from 09.50 ± 0.70 and 19.50 ± 0.70 mm) and broth microdilution test (MIC values ranging between 97.66 and 781.25 μM) The highest antioxidant activity, among ligand and its metal complexes, were recorded for Ni (II) complex with IC50 value 59.17 ± 01.94 μM. The compounds with antimicrobial and antioxidant effects were further investigated via in silico approaches. The binding parameter values were calculated for the effectiveness of [FeL1L2H2O].3H2O complexes on the antimicrobial target and [NiL1L2H2O].2H2O complexes on the antioxidant target in molecular docking. © 2025 Elsevier B.V.