Molecular structure and spectroscopic analysis of 1,4-Bis(1-methyl-2-benzimidazolyl)benzene; XRD, FT-IR, dispersive-Raman, NMR and DFT studies Bilge Eren a,⇑ , Arslan Ünal b a Department of Chemistry, Science and Arts Faculty Bilecik S ßeyh Edebali University, 11210 Bilecik, Turkey b Department of Physics, Science and Arts Faculty Bilecik S ßeyh Edebali University, 11210 Bilecik, Turkey highlights " 1,4-Bis(1-methyl-2- benzimidazolyl)benzene was synthesized under microwave conditions. " It was characterized by using XRD, FT-IR, dispersive-Raman, NMR and DFT. " Conformational analysis was also carried out. " A complete assignments of the vibrational modes were proposed. " The theoretical results were compared with the experimental findings. graphical abstract article info Article history: Received 9 August 2012 Received in revised form 5 October 2012 Accepted 10 October 2012 Available online 7 November 2012 Keywords: 1,4-Bis(1-methyl-2- benzimidazolyl)benzene Bis-benzimidazole XRD Vibrational spectra NMR DFT abstract This study reports the structural characterization of a bis-benzimidazole derivative, 1,4-Bis(1-methyl-2- benzimidazolyl)benzene (BMBB), by using spectroscopic and quantum chemical methods. The BMBB molecule was synthesized under microwave conditions and was characterized by using single-crystal X-ray diffraction, FT-IR, dispersive Raman and NMR spectroscopies. The potential energy surface scan study was carried out for the conformation of the theoretical structure. Quantum chemical calculations of relative energies, molecular geometry, vibrational wavenumbers, frontier molecular orbitals, atomic charges and gauge including atomic orbital (GIAO) 1 H and 13 C-NMR chemical shifts of the compound were carried out by using density functional method (DFT) at B3LYP/6-311++G(d,p) theory level. The complete assignments of the vibrational modes were performed with DFT calculations combined with scaled quantum mechanics force field (SQMFF) methodology. A satisfactory consistency between the experimental and theoretical findings was obtained. On account of the relative energies, population anal- ysis and XRD results, the most stable conformational form of the molecule was also determined. Ó 2012 Elsevier B.V. All rights reserved. Introduction Vibrational (IR, Raman) and NMR spectroscopies are extensively used in order to investigate dynamical and structural properties of molecules. With the recent developments in computational meth- ods, it is possible to describe molecular properties of molecules with close chemical accuracy using theoretical methods [1,2]. The density functional theory (DFT) calculations using B3LYP method shows good agreement with the experimental data at molecular electrostatic potentials, bond energies, optical proper- ties, vibrational frequencies and geometric parameters of organic compounds [3–11]. Bis-benzimidazoles are an important class of bioactive molecules in the field of chemistry and pharmacology. Bis-benzimidazole 1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2012.10.055 ⇑ Corresponding author. Tel.: +90 228 214 1481; fax: +90 228 216 0080. E-mail address: bilge.eren@bilecik.edu.tr (B. Eren). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 103 (2013) 222–231 Contents lists available at SciVerse ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa