DIIODINE BASICITY OF SOME 1,2,4-TRIAZOLE-THIONES

The basicity toward diiodine of three N-methylated 1,2,4-triazole-thio nes has been studied by means of the measure of formation constants in dichloromethane at 298K using UV-Visible spectroscopy. The preferred site of fixation of diiodine is the sulphur atom of the exocyclic thio carbonyl group. This result agree with ''HSAB'' Pearson's theory of ac ids and bases. The experimental results are confirmed by theoretical c alculations using ab-initio method and 3-21G basis set. The standard G ibbs energies of complexation in solution are well correlated to the e lectronic changes Delta E-o calculated by ab-initio method.