Substituent effect on molecular structure of the triazolium ring: Geometrical analysis, atomic charges, aromaticity and vibrational spectra

FT-IR and FT-Raman spectra of two 1,3,4-substituted-1,2,4-triazolium salts in the polycrystalline state were recorded in the 4000–100 cm−1 spectral region as part of a series of spectroscopic and theoretical analysis of azolium salts. The molecular structures and the vibrational spectra (including PED calculations) were described by using the DFT hybrid functional (B3LYP). The results of computation were then compared to the experimental data. Our assignment of the observed vibrational modes is proposed on the basis of these calculations. Furthermore, we focused our attention on electron delocalization inside the N-heterocyclic ring. This problem was analyzed by using geometrical parameters and electron density distribution evaluated by using calculation of atomic charges. Besides, aromaticity of the triazolium ring was expressed by HOMA index. All physico-chemical parameters were discussed with respect to the substituents’ effect on the triazolium cation. This research is a part of ongoing in our laboratory program to understand structure–function relationship of such salts that is getting growing attention from many scientific laboratories and industry.Figure optionsDownload full-size imageDownload as PowerPoint slide