Exploring N-Benzylidene-Isonicotinohydrazide Schiff Base and Its Ni(II), Cu(II), and Co(II) Complexes: Synthesis, Spectroscopic, Computational, and Molecular Docking Insights with the COVID-19 Protein Receptor
Md. Ashraful Islam
Department of Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh.
Md. Sohanur Rahman
Department of Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh.
Faria Tasnim
Department of Genetic Engineering and Biotechnology, Rajshahi University, Rajshahi-6205, Bangladesh.
Toukir Biswas
Department of Applied Chemistry and Chemical Engineering, Rajshahi University, Rajshahi-6205, Bangladesh.
Md. Faruk Hossen
Department of Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh.
Md. Kudrat-E-Zahan
Department of Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh.
Md. Ali Asraf *
Department of Chemistry, Rajshahi University, Rajshahi-6205, Bangladesh.
*Author to whom correspondence should be addressed.
Abstract
A Schiff base ligand (L), N-benzylidene-isonicotinohydrazide (C₁₃H₁₁N₃O), was synthesized via the condensation of benzaldehyde and isoniazid in an ethanolic medium. The ligand was characterized by FT-IR, ¹HNMR, UV-Vis, ESI-MS, and elemental analysis, confirming its successful formation. Metal complexes of Ni(II), Co(II), and Cu(II) were synthesized by reacting the ligand with corresponding metal acetate salts under reflux conditions. Spectroscopic data revealed that coordination occurred through the azomethine nitrogen and carbonyl oxygen, as evidenced by shifts in characteristic IR bands. Electronic spectra and magnetic moment studies indicated that all three complexes adopted a distorted square planar geometry. Molar conductivity measurements confirmed their non-electrolytic nature. Density functional theory (DFT) calculations provided insight into the optimized geometries and electronic properties of the ligand and complexes, with HOMO-LUMO energy gap analysis suggesting enhanced reactivity upon complexation. Molecular docking of the free ligand and its metal complexes was performed against the SARS-CoV-2 main protease (PDB ID: 6XBH), yielding promising results.
Keywords: Schiff base, metal complex, density functional theory (DFT), molecular docking