Seven Schiff base compounds were synthesized via the nucleophilic condensation of 5‐substituted‐3‐thione‐1,2,4‐triazole and 2,4,6‐trimethyl benzaldehyde. All of the synthesized compounds (A1–A3 and B1–B4) were thoroughly characterized by using spectroscopic and physical analytical methods. The in vitro antifungal activities of the prepared compounds were studied, and results showed that A2, B1, B2, and B3 have good biological activity. Molecular docking was used to predict the binding modes of the ligands to 6CR2 protein, and the reasons behind the excellent activities of A2 and B2 were explored. Finally,the highest occupied molecular orbital, lowest unoccupied molecular orbital, and natural bonding orbital of the compounds were calculated by using density functional theory at the B3LYP/6‐31G level.
Seven 4-amino-5-substituted-1,2,4-triazole-3-thione Schiff base compounds were synthesized reacting 4-amino-5-substituted-1,2,4-triazole-3-thione with dichloro-substituted 5-pyrimidines, and the structures were verified by elemental analysis and spectroscopic techniques (FT-IR, 1H NMR). Additionally, in vitro antifungal activities of the compounds (named F1~F2; A1~A5) against Grape anthracnose and Wheat gibberellic have been evaluated. The compounds of F1, A4 and A5 were found to be potentially effective antifungal agents against Grape anthracnose, while the others showed the low bioactivity. The antifungal activity of all compounds against Wheat gibberellic were superior to that of fluconazole (standard drug, SD). Particularly, compounds of F1, A1, A4 and A5 exhibited a broad-spectrum antifungal activity against two fungus as compared to the others. Therefore, molecular docking study was carried out to explore the potential interaction between ligands and Fusarium graminearum (PDB ID: 5E9H). The results showed that four compounds had higher affinity compared with fluconazole and form the stable complex with the receptor. Besides, the frontier molecular orbitals (FMOs) and molecular electrostatic potentials (MEP) of four compounds with broad-spectrum antimicrobial activity were also calculated with DFT/ B3LYP /6-31G (d, p) method. The energy gap values (△ELUMO-HOMO) of all the synthesized compounds ranged from 3.307-3.375 eV, which was lower than that of SD (6.248 eV). Additionally, according to MEP the electrophile reaction of 5-substituted groups was beneficial to improving the biological activity against Wheat gibberellic and Grape anthracnose.
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