Manganese, Cobalt, and Cadmium Complexes of Quinazoline Schiff Base Ligand and Methionine: Synthesis, Characterization, DFT, Docking studies and biomedical application

Mixed ligand complexes of MnII, CoII and CdII with a novel Schiff base ligand 4-(2-((1E,2E)-1-(2-(p-tolyl)hydrazineylidene)propan-2-ylidene)hydrazineyl) as principal ligand (L1) and Methionine (L2) as an ancillary ligand were successfully synthesized and thoroughly characterized by employing various analytical methods, including Elemental analysis, FT-IR, UV-Visible, Mass spectra, and conductometric measurements. Density functional theory (DFT) computations have being executed employing LANL2DZ basis sets, conjoined with the B3LYP correlation functional, to elucidate the stable electronic configuration, (HOMO–LUMO) energy gap, dipole moment, and chemical hardness of the hybrid ligand complexes. The proposed geometry for the complexes is a distorted octahedral structure. Additionally, the structural parameters and (MEP) Molecular Electrostatic Potential of these compounds were calculated using a DFT level basis set and allied with the experimental records. The antimicrobial potential of these compounds were assessed in contradiction of a diverse range of bacterial and fungal strains, encompassing Gram(+ve) bacteria such as Streptococcus mutans and Staphylococcus aureus, Gram(-ve) bacteria like Klebsiella Pneumonia and Escherichia coli, and the fungus Candida albicans. Significantly, these complexes demonstrated noteworthy antimicrobial activities, with the Cd (II) complex exhibiting the greatest efficacy against all the checked organisms. In the pursuit of exploring their broader medical potential, these compounds were also investigated for their antibiotic properties against H. pylori, showing substantial potential as effective antibiotics against this bacterium. Furthermore, the synthesized complexes were considered for their antitumor properties against MCF-7 Breast carcinoma cells. Among them, the (L1) (L2) Co (Cl).3H2O complex displayed the most potent activity, with the lowest IC50 value of 17 μg/ml compared to cisplatin. Moreover, it exhibited reduced cytotoxicity towards normal cells (VERO cells) in comparison to cisplatin, establishing it as the supreme potent compound in the study. Moreover, molecular docking studies were conducted using DFT-optimized structures of the Schiff base ligand (L1) and its Cd (II) complex to elucidate their interactions with selected protein structures involving (3AHU, 1GHP, 2ZIC, 4N74, 5JPE, 3HB5, and 6W41), providing insights into their preferred modes of interaction. This comprehensive study underscores the multifaceted applications and promising bioactive properties of these synthesized compounds.