Design, synthesis, biological activities and DFT calculation of novel 1,2,4-triazole Schiff base derivatives

Series of novel 1,2,4-triazole Schiff bases were synthesized and evaluated for antifungal and antibacterial activities. The bioassay showed compound 2a has potential to developing candidate compound. The DFT calculation indicated triazole ring, S atom and benzene ring in both of the 2a and 3a make a major contribution to the activity. [Display omitted] •Compound 2a exhibited excellent antifungal and antibacterial activities.•No substitution at position 5 of 1,2,4-triazole caused increase in activity.•HOMO and LUMO of compounds 2a and 3a were first calculated by DFT/B3LYP. Series of 1,2,4-triazole Schiff bases (2a-2d, 2f-2h and 3a-3h) have been designed and synthesized. The structure of title compounds was confirmed on the basis of their spectral data and elemental analysis. All the target compounds were screened for their in vitro antifungal activity and antibacterial activity. Two of the tested compounds (2a and 2b) exhibited significant antifungal activity against most fungi, especially compound 2a showed better antifungal activity than triadimefon. Meanwhile, the antibacterial activity assay also indicated compound 2a exhibited excellent antibacterial activities comparable to chloramphenicol. The SAR manifested no substitution at position 5 of the triazole ring caused an increase in activity, and 3-phenoxy phenyl group introduced in 1,2,4-triazole scaffold can enhance the antibacterial activity. The DFT calculation indicated triazole ring, S atom and benzene ring in both of the 2a and 3a make a major contribution to the activity.