Synthesis, spectral (FT-IR, UV-visible, NMR) features, biological activity prediction and theoretical studies of 4-Amino-3-(4hydroxybenzyl)-1H-1,2,4-triazole-5(4H)-thione and its tautomer

Triazole compounds constitute an important class of organic chemistry due to their various biological and corrosion inhibition activities. The synthesis scheme of a new triazole compound namely, 4-Amino3-(4-hydroxybenzy1)-1H-1,2,4-triazole-5(4H)-thione (4AHT) has been theoretically analyzed. Our density functional theory (DFT) based calculations show that the synthesis of 4AHT is energetically feasible at the room temperature as the reaction is exothermic, spontaneous as well as favored in forward direction. The calculated bond-lengths are found to be in good agreement with corresponding crystallo-graphic values. We have considered two possible tautomers of 4AHT viz. thione and thiol forms. The FTIR (KBr disc), UV-visible (ethanol) and H-1-NMR (DMSO) spectra of 4AHT have been recorded. The vibrational modes have been assigned on the basis of their potential energy distributions and scaled wavenumbers agree well with the FT-IR wavenumbers. Time dependent DFT calculations are performed to analyze the electronic transitions for various excited states which reproduce the experimental peak observed in UV-visible spectrum. Using gauge independent atomic orbital method 1H-NMR chemical shifts have been calculated and correlated with the experimental chemical shifts with the linear correlation coefficient of 0.9453. Our spectral analyses reveal the dominance of thione over thiol form of 4AHT. The chemical reactivity of 4AHT has been discussed by molecular electrostatic potential surface as well as various electronic parameters. The biological activities of 4AHT have also been explored theoretically and it has been found that the title molecule can act as a potential inhibitor of cyclin-dependent kinase 5 enzyme. These findings may guide the synthesis and design of new triazole compounds with interesting biological activity. (C) 2015 Elsevier B.V. All rights reserved.