bis-(1H-Benzimidazol-2-yl)-methanone: New preparation method, crystal structure, vibrational spectroscopy and DFT calculations

This study reports a new preparation of bis-(1H-benzimidazol-2-yl)-methanone, 3, an interesting compound prepared by the oxidation of bis-(1H-benzimidazol-2-yl)-methane using two methods: (i) Fe(II)/O2 in ethanol–water and (ii) hydrogen peroxide in acetic acid. Products of both methodologies were properly characterized by elemental analysis, IR, Raman, (1H and 13C) NMR and X-ray crystallography. DFT calculations [B3LYP/6-31+G(d,p)] also showed good agreement between the theoretical and experimental values of optimized and X-ray structures as well as between the vibrational and NMR spectroscopy. The study of the conformational dynamics of 3 found a low energy barrier (0.41 kcal mol−1) between the two conformations in the DMSO phase.