Molecular structure and vibrational assignment of 1-[N-(2-pyridyl) aminomethylidene}-2(1H)-Naphtalenone by density functional theory (DFT) and ab initio Hartree–Fock (HF) calculations Hasan Tanak a,⇑ , Mehmet Toy b a Department of Physics, Faculty of Arts and Sciences, Amasya University, 05100 Amasya, Turkey b Faculty of Education, Department of Science Education Amasya University, Amasya, Turkey highlights  The spectroscopic (FT-IR and UV–vis) properties of the compound were examined.  The molecular geometry and vibrations were calculated using the DFT and HF methods.  HOMO and LUMO energies, absorption wavelength and excitation energies were calculated.  The TD-DFT calculations lead to a very closer agreement with the experiment. graphical abstract article info Article history: Received 23 June 2014 Received in revised form 10 October 2014 Accepted 1 November 2014 Available online xxxx Keywords: Schiff base IR Electronic absorption spectra DFT HF abstract The molecular geometry and vibrational frequencies of 1-[N-(2-pyridyl)aminomethylidene}-2(1H)- Naphtalenone in the ground state have been calculated by using the Hartree–Fock (HF) and density func- tional method (B3LYP) with 6-311++G(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibrational frequencies were used to determine the types of molecular motions associated with each of the experimental bands observed. In addition, calculated results are related to the linear correlation plot of computed data versus experimental geometric parameters and IR data. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies. Using the time-dependent density functional theory (TD-DFT) and Hartree–Fock (TD-HF) methods, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and experimental ones is determined. Ó 2014 Elsevier B.V. All rights reserved. Introduction Schiff bases (Azomethines) are used as starting materials in the synthesis of important drugs, such as antiallergic and antibiotics, antitumor and antiphlogistic substances [1–3]. On the industrial scale, they have a wide range of applications, such as dyes and pig- ments [4]. Schiff base complexes have been playing an important role in the development of coordination chemistry related to catal- ysis and enzymatic reactions [5–9], molecular architectures and magnetism [10,11]. Schiff base compounds display interesting pho- tochromic and thermochromic features in the solid state and can be classified in terms of these properties [12]. Photo- and thermochro- mism arise via H-atom transfer from the hydroxy O atom to the http://dx.doi.org/10.1016/j.saa.2014.11.002 1386-1425/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +90 358 242 16 13; fax: +90 358 242 16 16. E-mail address: hasantanak@gmail.com (H. Tanak). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy xxx (2014) xxx–xxx Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa Please cite this article in press as: H. Tanak, M. Toy, Molecular structure and vibrational assignment of 1-[N-(2-pyridyl) aminomethylidene}-2(1H)-Naph- talenone by density functional theory (DFT) and ab initio Hartree–Fock (HF) calculations, Spectrochimica Acta Part A: Molecular and Biomolecular Spectro- scopy (2014), http://dx.doi.org/10.1016/j.saa.2014.11.002