Characterization of novel ternary transition metal complexes of Co(II) and Ni(II): Molecular docking and assessment of cytotoxicity and biological activity

In this study, the preparation of novel nanosized Cobalt (II) and Nickel (II) complexes incorporating L-cysteine (Cys) and glutamic acid (Glu) as bidentate ligands are reported. Cetyltrimethylammonium bromide (CTAB) was used as a capping agent to control nanoparticle size and enhance biological activity. Bulk counterparts were also synthesized for comparative analysis. Comprehensive characterization using FTIR, UV–Vis, magnetic susceptibility, TGA, mass spectrometry, elemental analysis, and atomic absorption spectroscopy confirmed distorted octahedral geometries with the formulas [Co(Cys)(Glu)(H₂O)₂]·3H₂O and [Ni(Cys)(Glu)(H₂O)₂]·1.5H₂O. Transmission electron microscopy (TEM) and FTIR verified nanoscale dimensions. The nanocomplexes exhibited potent antimicrobial activity was evaluated against Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans. Cytotoxicity assays against HepG2 cells revealed IC₅₀ values comparable to 5-fluorouracil, highlighting their promising anticancer potential. DFT and TD-DFT calculations performed using the B3LYP/6-311G** and B3LYP/6-311G**-LANL2DZ methods offered valuable information on the electronic configuration, bonding characteristics, and optical behavior. Remarkably, the nanocomplexes exhibited significant nonlinear optical (NLO) responses, indicating potential for optoelectronic applications. Molecular docking revealed strong binding of the complexes to the nucleocapsid protein of human coronavirus NL63, blocking its active site and suggesting antiviral potential consistent with experimental antimicrobial results. These findings emphasize the novelty and multifunctionality of CTAB-stabilized Co(II) and Ni(II) nanocomplexes, supporting their future use as promising antimicrobial, anticancer, and antiviral agents—particularly relevant in the context of emerging viral threats like COVID-19.