3-Amino-1,2,4-triazolium ion in [24(3at)]Cl and [24(3at)]2SnCl6·H2O. Comparative X-ray, vibrational and theoretical studies

Crystal structures of 3-amino-1,2,4-triazolium chloride and bis(3-amino-1,2,4-triazolium) hexachloridostannate monohydrate were determined by means of X-ray single crystal diffraction. The route of protonation of organic molecule and tautomer equilibrium constants for the cationic forms were calculated using B3LYP/6-31G* method. The most stable protonated species is 2,4-H2-3-amino-1,2,4-triazolium ion, 24(3at)+. Very good agreement between theoretical and experimental frequencies was achieved due to very weak interactions existing in studied compounds. Significantly weaker intermolecular interactions are found in [24(3at)]2SnCl6·H2O than in [24(3at)]Cl. The differences in strength of interactions are manifested in red and blue shifts for stretching and bending motions, respectively. PED calculations show that for 24(3at)+ ion the stretching type of motion of two NringH bonds is independent, whereas bending is coupled.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► X-ray structures of [24(3at)]Cl and [24(3at)]2SnCl6·H2O were determined. ► Route of protonation of 3at was theoretically studied. ► Tautomeric equilibrium constants for protonation species of 3at were calculated. ► Weak hydrogen bonds exist in the crystal structures exclusively. ► Exact theoretical reproduction of vibrational spectra was made.