Synthesis, spectroscopic characterization and DFT calculations of N-Methyl-2-(2 '-hydroxyphenyl)benzimidazole derivatives

Abstract

1-Methy1-2-(2'-hydroxyphenyl)benzimidazole (1) and 1-Methy1-2-(2'-hydroxy-4'-methylphenyl)benzimidazole (2) compounds have been synthesized and characterized by XRD, IE-MS, FT-IR, UV Vis and H-1, C-13 NMR techniques. The crystal structure of both compounds is stabilized with very strong O-H center dot center dot center dot N hydrogen-bond and pi-pi interactions. In the compound 1, an infinite chain structure with a trans-zigzag type was formed along the crystallographic 11011 direction. Quantum mechanical calculations of energies, geometries, vibrational wavenumbers, NMR and electronic transitions were carried out by DFT using B3LYP functional combined with 6.31G(d,p) basis set. Calculated bond lengths, bond angles and dihedral angles were only slightly different from the experimental ones. The vibrational study was interpreted by means of potential energy distribution (PED). The electronic absorption spectra of the both compounds were predicted by using the time-dependent DFT methods and good agreement was found between the computational and the experimental values. The chemical shifts (H-1 and (1)3C NMR) and isotropic shielding values were calculated by using the gauge-invariant atomic orbital (GIAO) method. The analyses of HOMO and LUMO have been used to explain the charge transfer within the molecule. (C) 2015 Elsevier B.V. All rights reserved.