Synthesis, structural and spectroscopic studies of two new benzimidazole derivatives: A comparative study

In the present work, structural and spectroscopic studies on 1-Methyl-2-(2'-hydroxy-4'-chlorophenyl) benzimidazole (1) and 1-Methyl-2-(2'-hydroxy-4'-methoxyphenyl)benzimidazole (2), have been carried out extensively by X-ray diffraction, HRMS, UV-Vis, FT-IR and H-1 and C-13 NMR spectroscopy. The crystal structure of both compounds is stabilized by O-H center dot center dot center dot N hydrogen bond and pi-pi interactions. Contrary to compound 1, the skeleton of compound 2 is considerably deviated from the planarity probably caused by intermolecular hydrogen bonding. The experimental results were compared to the theoretical ones, obtained at DFT level. Ground state geometry, electronic structure, vibrational and NMR spectra have been performed using the B3LYP functional with the 6-31 G(d,p) basis set. It was observed that the bond distances and angles in the both compounds were in good with those of the experiment. The energetic behaviors of the both compounds in methanol solvent were examined using by time-dependent DFT (TD-DFT) method by applying the polarizable continuum model (PCM). Isotropic chemical shifts (C-13 and H-1 NMR) were calculated using the gauge-invariant atomic orbital (GIAO) method. The HOMO and LUMO analyses were used to elucidate information regarding charge transfer within the molecule. (C) 2016 Elsevier B.V. All rights reserved.