Structural and spectroscopic characterization of 2-mesityl-1H-benzo[d]imidazol-3-ium chloride: A combined experimental and theoretical analysis

The title molecular salt, 2-mesityl-1H-benzo[d]imidazol-3-ium chloride (C16H17N2+·Clˉ), was synthesized unexpectedly from the reaction of N-[(1E)-mesitylmethylene]benzene-1,2-diamine and CoCl2·6H2O, and characterized by elemental analysis, 1H NMR and FT-IR spectroscopies, and single-crystal X-ray diffraction technique. In addition, quantum chemical calculations employing density functional theory (DFT) method with the 6−311++G(d,p) basis set were performed to study the molecular, spectroscopic and some electronic structure properties of the title compound, and the results were compared with the experimental findings. The computational result shows that the optimized geometry can well reproduce the crystal structural parameters. The intermolecular proton transfer process between the ionic (C16H17N2+·Clˉ) and nonionic forms (C16H16N2·HCl) of the title salt is investigated and found to be almost barierless with an energy value of 0.20 kcal mol−1. The NLO properties of the compound are bigger than those of urea.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► A novel benzimidazole molecular salt was synthesized. ► The compound was characterized by IR–NMR and X-ray single crystal diffraction. ► The intermolecular proton transfer process was investigated.