Synthesis, calf thymus DNA binding, in-vitro cytotoxicity, molecular docking, and antimicrobial studies of novel metal complexes containing a 2,3-diaminopyridine derivative Schiff base

In this work, a tetradentate ONNO Schiff base ligand, namely 4,4'-[(1E,1`E)-(pyridine-2,3-diyl)bis(azanylylidene)bis(methanylylidene)bis (benzene-1,3-diol] (H₂L) was prepared and characterized. Cu(II), Co(II), Mn(II), and Ni(II) complexes have an octahedral geometry. Pd(II) complex exhibits diamagnetic behavior and attains stability in square planar locations. The complexes are non-electrolytes, according to the molar conductivity investigations. By means of two phenolic OH and two azomethine nitrogen, the ligand is thought to be tetradentate and coordinated with Co(II) and Ni(II) ions, according to spectral data. Cu(II), Mn(II), and Pd(II) complexes, on the other hand, were coordinated by two phenolic oxygen and two azomethine nitrogen with deprotonation of OH groups. Antimicrobial activities, ligands, and metal complexes were screened against bacteria, such as E. faecalis, Salmonella sp., B. cereus, and S. epidermidis, and fungi, such as A. flavus, A. solani, and C. albicans. Notably, all synthesized compounds demonstrated good results of inhibition against the chosen pathogenic fungi compared to their antibacterial properties. Molecular docking was utilized to explore possible interactions between the studied compounds (H₂L and complexes) and the breast cancer cell line. The abovementioned compounds were proven to have potential anticancer effects against protein receptors (PDB IDs: 1QNT, 3FC2, and 4AJY). The least binding energy was used to predict the receptor's binding site with compounds, offering a better understanding of the process. Furthermore, the MTT test was employed to assess the in vitro cytotoxicity of the compounds against the MCF-7 cancer cell line in order to assess the anticancer characteristics of the Schiff base and its complexes. The findings demonstrated that each combination has exceptional antitumor activity.