Sciknow Publications Ltd. JSMR 2014, 2(4):80-90 Journal of Single Molecule Research DOI: 10.12966/jsmr.12.04.2014 ©Attribution 3.0 Unported (CC BY 3.0) Investigation of Spectroscopic (FT-IR and NMR), Structural and Non-linear Optical Properties of 4-Chloro-2-[(4-chlorobenzylidene)amino]phenol by using DFT Quantum Chemical Calculations Kürşat EFIL 1,3,* , Fatih ŞEN 2 ,Yunus BEKDEMIR 3 and Muharrem DINÇER 4 1 Ondokuz Mayıs University, Arts and Sciences Faculty, Department of Chemistry, Samsun, Turkey 2 Kilis 7 Aralık University, Vocational High School of Health Services, Department of Opticianry, Kilis, Turkey 3 Canik Başarı University, Arts and Sciences Faculty, Department of Molecular Biology and Genetics, Samsun, Turkey 4 Ondokuz Mayıs University, Arts and Sciences Faculty, Department of Physics, Samsun, Turkey *Corresponding author (Email: kursatefil@gmail.com) Received: 15 October 2014; Revised: 20 October 2014; Accepted: 29 October 2014; Published: 20 November 2014 Abstract - In this study, 4-chloro-2-[(4-chlorobenzylidene)-amino]phenol molecule (C 13 H 9 Cl 2 NO) was investigated using experimental spectroscopic techniques and quantum chemical methods. The structure of molecule has been characterized by using both FT-IR and NMR ( 1 H, 13 C) spectroscopic techniques. The IR spectrum of the title molecule was recorded in the 400-4000 cm -1 region. The 1 H and 13 C-NMR spectra of the molecule were recorded. The geometry, vibrational frequencies, 1 H and 13 C-NMR chemical shift values of the title molecule in the ground state were calculated by using the DFT/B3LYP method with 6-31G*, 6-311G** and LANL2DZ basis sets. The calculated geometric parameters, vibrational frequencies and chemical shift values were compared with experimental data of title molecule. In addition to all this non-linear optical properties, potential energy surface (PES), frontier molecular orbitals (FMOs), molecular electrostatic potential and Mulliken population analysis for corresponding molecule were theoretically investigated using quantum mechanical calculations. The results showed a good agreement between experimental and calculated data and provide some important estimates for title molecule . Keywords - Schiff base, Spectral characterization, Density functional theory (DFT), Non-linear optical properties, HOMO–LUMO analysis 1. Introduction Schiff bases (also imines orazomethines),which have carbon=nitrogen double bonds, can be readily synthesized by refluxing of primary amines and active carbonyl compounds (aldehydes and ketones)[1–3]. They were first introduced by Hugo Schiff in 1864[4] and have a wide variety of applications in many fields, such as biological[5], inorganic[6], analytical[7,8] and material chemistry[9]. Schiff bases and their complexes with metal show catalytic activity in various biological systems, and they are also used as active materials for polymerization, functional dyes and pigments, as well as in the field of pharmaceutical medicine[10,11]. Most of Schiff bases show antibacterial[12], anticancer[13], anti-inflammatory[14] and antitoxic activities[15], and their sulfur-containing derivatives were shown to be particularly more effective[16]. On the other hand, Schiff bases have photochromic property, which is photo-induced alteration of molecular structure based on inherent keto-enoltautomerism. Such compounds having photochromic properties have potential applications for photo-electronic devices such as optical memory and switches[17]. They received more attention recently due to their potential uses in the field of optical communication, and many of such compounds show nonlinear optical (NLO) properties[18,19]. The theoretical modeling studies for drug design and functional material design have improved with recent advances in computational chemistry. Some important physical and chemical properties of chemical and biological systems can be predicted by various computational methods and techniques[20]. In recent years, density functional theory (DFT) has had considerable significance for theoretical modeling. The development of better and better exchange–correlation functional has made it possible to