Journal Article

Synthesis of Novel Tritopic Hydrazone Ligands: Spectroscopy, Biological Activity, DFT, and Molecular Docking Studies

S. M. Tareque Abedin, Sharmin Akther Rupa, Md. Aminul Haque, Jamal Uddin, Md. Mayez Mahmud, Md. Rassel Moni, Md. Abdul Majed Patwary

2022

Overview

Polytopic organic ligands with hydrazone moiety are at the forefront of new drug research among many others due to their unique and versatile functionality and ease of strategic ligand design. Quantum chemical calculations of these polyfunctional ligands can be carried out in silico to determine the thermodynamic parameters. In this study two new tritopic dihydrazide ligands, N’2, N’6-bis[(1E)-1-(thiophen-2-yl) ethylidene] pyridine-2,6-dicarbohydrazide (L1) and N’2, N’6-bis[(1E)-1-(1H-pyrrol-2-yl) ethylidene] pyridine-2,6-dicarbohydrazide (L2) were successfully prepared by the condensation reaction of pyridine-2,6-dicarboxylic hydrazide with 2-acetylthiophene and 2-acetylpyrrole. The FT-IR, 1H, and 13C NMR, as well as mass spectra of both L1 and L2, were recorded and analyzed. Quantum chemical calculations were performed at the DFT/B3LYP/cc-pvdz/6-311G+(d,p) level of theory to study the molecular geometry, vibrational frequencies, and thermodynamic properties including changes of ∆H, ∆S, and ∆G for both the ligands. The optimized vibrational frequency and (1H and 13C) NMR obtained by B3LYP/cc-pvdz/6-311G+(d,p) showed good agreement with experimental FT-IR and NMR data. Frontier molecular orbital (FMO) calculations were also conducted to find the HOMO, LUMO, and HOMO–LUMO gaps of the two synthesized compounds. To investigate the biological activities of the ligands, L1 and L2 were tested using in vitro bioassays against some Gram-negative and Gram-positive bacteria and fungus strains. In addition, molecular docking was used to study the molecular behavior of L1 and L2 against tyrosinase from Bacillus megaterium. The outcomes revealed that both L1 and L2 can suppress microbial growth of bacteria and fungi with variable potency. The antibacterial activity results demonstrated the compound L2 to be potentially effective against Bacillus megaterium with inhibition zones of 12 mm while the molecular docking study showed the binding energies for L1 and L2 to be −7.7 and −8.8 kcal mol−1, respectively, with tyrosinase from Bacillus megaterium.

• Publisher: MDPI AG,MDPI
• Subject: Anti-Bacterial Agents - chemical synthesis / Anti-Bacterial Agents - chemistry / Anti-Bacterial Agents - pharmacology / Antimicrobial agents / Bacteria / Binding sites / Crystal structure / Density Functional Theory / DFT / DFT; vibrational frequencies; FMO; tritopic; polydentate; molecular docking / FMO / Geometry / Gram-positive bacteria / Hydrazones / Hydrazones - chemical synthesis / Hydrazones - chemistry / Hydrazones - pharmacology / Ligands / Magnetic Resonance Spectroscopy / Microbial Sensitivity Tests / molecular docking / Molecular Docking Simulation / Molecular Structure / Organic chemistry / polydentate / Proteins / QD241-441 / Software packages / Spectroscopy, Fourier Transform Infrared / Thermodynamics / tritopic / vibrational frequencies