Dual-Function Schiff Base/Nitro-Phenanthroline Cu(II), Co(II), and Mn(II) Complexes: Exploring Cytotoxic Activity, Catalytic Efficiency, and Molecular Docking Insights

This study reports the synthesis and characterization of mixed-ligand Cu(II), Co(II), and Mn(II) complexes derived from 2-(((2-hydroxyphenyl)imino)methyl)-4-methoxy-6-nitrophenol (L1) and 5-nitro-1,10-phenanthroline (L2). The ligand and complexes were characterized by 1H/13C NMR (L1 only), FT-IR, UV–vis, LC-MS/MS, TGA, and elemental analysis. Cytotoxicity studies against A549 and HTB-54 lung cancer cells identified the Cu(II) complex as the most active compound, with IC50 values of 24.05 and 22.08 µM, respectively, while showing lower toxicity toward BEAS-2B normal cells (IC50 = 39.08 µM). The Cu(II) complex significantly inhibited cell migration and induced apoptosis, supported by increased Bax expression in qPCR analysis. Molecular docking with selected cancer-related protein targets further supported its proposed anticancer mechanism. The catalytic activity of the complexes was investigated for the solvent-free cycloaddition of CO2 with epoxides. The Co(II) complex exhibited the highest catalytic performance, affording 86.5% yield and 97.0% selectivity in the presence of DMAP under optimized conditions. Density functional theory (DFT) calculations provided the EHOMO, ELUMO, chemical potential, hardness, softness, electrophilicity index, and MEP profile of the ligand and complexes, demonstrating their multifunctional potential for anticancer and sustainable catalytic applications. © 2026 Wiley-VCH GmbH.