Synthesis, Quantum Chemical Calculation, And Antibacterial Activity Evaluation Of Novel Triazole Related Derivatives

1,2,4-Triazoles derivatives, owing to their especial structure, have got extensive application in the fileds of medicine, pesticide and material, related theory research and application development has attracted more and more scientists. In this article, a series of novel 1,2,4-triazoles dertivatives were systhesized, and confirmed by 1H-NMR spectral, mass spectral, Fourier transform- infrared(FT-IR) spectral and elemental analysis. All the newly synthesized componds were screened for their in vitro antibacterial activities. The relationship between the structures and the antibacterial activities of the compounds was discussed. The main works are as follows:(1) 5,5'-(pyridine-2,6-diyl)bis(4-amino-3-mercapto-1,2,4-triazole) was prepared staring from 2,6-pyridine dicarboxylic acid via esterification, hydrazinolysis, and cyclization. The reaction of 5,5'-(pyridine-2,6-diyl)bis(4-amino-3-mercapto-1,2,4- triazole) with various substituted phenyl aldehydes in acetic acid yielded the correspoding 5,5'-(pyridine- 2,6-diyl)bis(4-arylideneamino-3-mercapto -1,2,4- triazole) derivatives. The structures of the newly synthesized compounds as well as their intermediates were confirmed by 1H-NMR spectral, mass spectral, Fourier transform- infrared (FT-IR) spectral and elemental analysis. All the newly synthesized componds were screened for their antibacterial activities, and some of them showed good activitives against three Gram-postive bacteria, and two Gram-negative bacteria, particulary against the tested Gram-negative bacteria. The relationship between the structures and biological activities was discussed, and the results indicted that the antibacterial activtiy of the derivatives with substituent were higher than that of the derivatives without substituent for the title compounds with the same sketch structure, and the para-derivatives were better than the ortho and meta derivatives, and the derivatives substituted by the donative electron group were better than the derivatives substituted by the electrophilic groups.(2) The reaction of 5,5'-( pyridine-2,6-diyl)bis(4-amino-3-mercapto-1,2,4-triazole) with various carboxylic acid in phosphorus oxychloride yielded the correspoding 2,6-bis(6-aliphatic/aryl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-3-yl)pyridine. The structures of newly synthesized compounds were confirmed by 1H-NMR spectral, mass spectral, Fourier transform- infrared (FT-IR) spectral and elemental analysis. All the newly synthesized componds were screened for their antibacterial activities and some of them showed good activitives against three Gram-postive bacteria, and two Gram-negative bacteria, particulary against the tested Gram-negative bacteria. The relationship betwwen the structures and biological activities was discussed, and the result indicted that the antimicrobial activtiy of the aryl substituted derivatives were better than the aliphatic substituted derivatives, and the phenyl substituted derivatives werer better than the heterocyclic substituted derivatives, and the para-derivatives were better than the ortho and meta derivatives.(3) The molecules structures of the synthesized 1,2,4-Trazoles Schiff base and 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazol were fully geometry optimized and frequency calculated by using quantum chemical density functional theory meyhod at B3LYP/6-31G* level. The pure charge distributions of every atom, molecule energy and IR spectrum of the title compounds were calculated. The results showed that the calculated IR spectrum was well confirmed by the experimental data, and the reason was discussed.