FT-IR and FT-Raman spectroscopies and DFT modelling of benzimidazolium salts

The molecular vibrations of polycrystalline 1,3-dimethylbenzimidazolium chlorate(VII) and 1,3-di-1-adamantylbenzimidazolium chlorate(VII) were investigated by FT-IR and FT-Raman spectroscopies. In addition, density functional method (B3LYP) was used to determine the geometrical and vibrational characteristics of the titled compounds. In computation, the cation-chlorate(VII) anion interaction was neglected. The experimental bands were assigned to normal modes on the basis of potential energy distribution analysis. It is worth noting that very good agreement between the calculated and observed frequencies for both compounds was obtained. Also, the charge distribution of benzimidazolium cations and aromaticity of the phenyl and imidazolium rings were discussed in view of the substituent effect. Calculations showed delocalization of the positive (+1) charge among the heterocyclic ring atoms. In a view of obtained results, investigated derivatives of the benzimidazolium cation would be treated as aromatic compounds.