Spectroscopic and DFT studies of 3-(m-nitrophenyl)-4-allyl-5-mercapto-1,2,4-triazole and 3-furyl-4-allyl-5-mercapto-1,2,4-triazole

In this study, the synthesized derivatives of 1,2,4-triazoles, 3-(m-nitrophenyl)-4-allyl-5-mercapto-1,2,4-triazole and 3-furyl-4-allyl-5-mercapto-1,2,4-triazole, were characterized using NMR, FTIR, Raman, and UV-Vis spectroscopies. A theoretical study of the thione-thiol tautomeric forms of these triazole molecules was performed by the density functional theory (DFT) method at the B3LYP/6–311 + +G(d,p) level in the gas phase and solvent media. The calculated vibrational wavenumbers were compared with experimental ones, and a full assignment of the fundamental vibrational modes was performed using potential energy distribution (PED) analysis. The electronic properties, such as electronic absorption wavelengths, HOMO-LUMO energies, and molecular electrostatic potential, as well as gauge-including atomic orbital (GIAO) 1 H and 13 C chemical shift values, were also determined. The results show that the studied 1,2,4-triazole derivatives exist in both thiol and thione forms and exhibit slight differences in their properties depending on the position of the substituent on the triazole ring. The presence of electron-withdrawing acceptor substituents at the 3-position of the triazole ring affects the S-H and N-H bonds in terms of both bond length and reactivity. • 3-(m-nitrophenyl)- and 3-furyl-4-allyl-5-mercapto-1,2,4-triazole were synthesized. • DFT was used to study the thione-thiol tautomeric forms of these triazoles. • They differ in properties depending on the position of the substituent in the triazole ring. • The thione tautomeric form predominates in solvents. • Spectroscopic (NMR, FTIR and UV/Vis) are in good agreement with DFT results.