ALEXANDRU C. RAZUS, LIVIU BIRZAN, MIHAELA CRISTEA, VICTORITA TECUCEANU, CONSTANTIN DRAGHICI, ANAMARIA HANGANU, MARIA MAGANU, LUCIA PINTILIE, ELEONORA MIHAELA UNGUREANU NEW (AZULEN-1-YLDIAZENYL)-HETEROAROMATIC COMPOUNDS CONTAINING 1,2,5-THIADIAZOL-3-YL MOIETIES
(E)-2-(Azulen-1-yldiazenyl)-1,3,4-thiadiazoles, unsubstituted or substituted either at azulen-1-yl moiety or at 5-position of thiadiazole ring were synthesized. Among the acids used as diazotization medium, dichloroacetic acid was the best choice. In several cases the by-products such as thioether 9 were isolated along with the normal coupling derivatives. The generated products were characterized and their MS and UV-vis spectra discussed. A computational study on (E)-2-(azulen-1-yldiazenyl)-1,3,4-thiadiazoles was undertaken based on density functional theory (DFT) to determine frontier orbital energies and other physical properties. The absorption maxima and the basicity of the new compounds are close to those of the corresponding diazenes containing thiazole, previously described. They have brick color in neutral medium and violet in strong acidic solutions. The redox potentials were also determined remarking the influence of the substituents on these potentials.
Keywords: Azulene, diazene, thiadiazoles, azo coupling, isosbestic point, reduction and oxidation potentials