Quantum-Chemical, IR, NMR, and X-ray Diffraction Studies on 2-(4-Chlorophenyl)-1-methyl- 1H-benzo[d]imidazole NAMIK O ¨ ZDEM _ IR, 1 B _ ILGE EREN, 2 MUHARREM D _ INC ¸ ER, 1 YUNUS BEKDEM _ IR 3 1 Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit, Samsun, Turkey 2 Department of Chemistry, Faculty of Arts and Sciences, Bilecik University 11100, Bilecik, Turkey 3 Department of Chemistry, Faculty of Arts and Sciences, Ondokuz Mayıs University, 55139 Kurupelit, Samsun, Turkey Received 24 October 2009; accepted 25 February 2010 Published online 27 July 2010 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/qua.22697 ABSTRACT: The title molecule, 2-(4-chlorophenyl)-1-methyl-1H-benzo[d]imidazole (C 14 H 11 ClN 2 ), was prepared and characterized by 1 H NMR, 13 C NMR, IR, and single- crystal X-ray diffraction. The molecular geometry, vibrational frequencies, and gauge including atomic orbital (GIAO) 1 H and 13 C NMR chemical shift values of the title compound in the ground state have been calculated by using the Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method with 6-31G(d) basis sets, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters, and the theoretical vibrational frequencies and GIAO 1 H and 13 C NMR chemical shifts show good agreement with experimental values. The energetic behavior of the title compound in solvent media has been examined using B3LYP method with the 6-31G(d) basis set by applying the Onsager and the polarizable continuum model (PCM). Besides, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis, and nonlinear optical (NLO) properties of the title compound were investigated by theoretical calculations. V C 2010 Wiley Periodicals, Inc. Int J Quantum Chem 111: 3112–3124, 2011 Key words: 2-(4-chlorophenyl)-1-methyl-1H-benzo[d]imidazole; crystal structure; IR and NMR spectroscopy; ab initio calculations; nonlinear optical (NLO) properties Correspondence to: N. O ¨ zdemir; e-mail: namiko@omu.edu.tr Contract grant sponsor: Research Centre of Ondokuz Mayıs University, Project No: F-461. International Journal of Quantum Chemistry, Vol 111, 3112–3124 (2011) V C 2010 Wiley Periodicals, Inc.