Synthesis, characterization, biological evaluation and molecular docking of a Schiff base ligand and its metal complexes.

Abstract

Condensation of 2,3-diaminopyridine with 2,4-dihyrodybenzaldehyde yielded a 4,4'-[(1E,1 ~ E)-(pyridine-2,3-diyl)bis(azanylylidene)]bis(methanylylidene)bis(benzene-1,3-diol) monobasic tridentate Schiff base ligand (HL) with an ONN donor sequence. Elemental analyses, conductivity tests, magnetic susceptibility data, FT-IR, UV-vis spectra, x-ray diffraction, and mass spectrum data of the ligand and its complexes were used for the characterization of the structures. Computational HF/3-21G calculations were performed to optimize their geometrical structures and assess their HOMO-LUMO energy gaps. The low molar conductance of the complexes indicates that they are not electrolytic. From the spectrophotometric and gravimetric analyses, the complexes (2-4) are in the ratio of 1:2, while complexes (1 & 5) (1:1) metal to ligand. 2,3-Diaminopyridine, 2,4-dihydroxybenzaldehyde, ligand (HL) and its complexes were screened for antibacterial and antifungal activities against some bacterial (Enterococcus faecalis, Salmonella typhi, and Staphylococcus epidermidis) and fungal isolates (Aspergillus flavus, Alternaria solani, and Candida albicans). The result reveals that 2,4-dihyrodybenzaldehyde has the strongest antibacterial activity among the other compounds followed by Mn(II) complex. The antimicrobial activity increases by increasing the compound concentration. To assess the inhibitory impact of ligand and its complexes on binding sites of B. cereus (PDB ID: 1FEZ), S. epidermidis (PDB ID: 3KP7), E. faecalis (PDB ID: 5V5U) and S. typhi (PDB ID: 5V2W) proteins, molecular modeling has been implemented offer a fresh concept for medication design. Molecular docking studies confirmed strong binding interactions between the metal complexes and bacterial proteins, validating their biological potential. These findings demonstrate the promising antimicrobial properties of Schiff base metal complexes, making them potential candidates for pharmaceutical and medicinal applications.