The synthesis, characterization and theoretical study on nicotinic acid [1-(2,3-dihydroxyphenyl)methylidene]hydrazide Necmi Dege a , Nuray S ßenyüz b , Hümeyra Batı b , Nergin Günay c , Davut Avcı c,⇑ , Ömer Tamer c , Yusuf Atalay c a Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139 Samsun, Turkey b Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Chemistry, 55139 Samsun, Turkey c Sakarya University, Faculty of Arts and Sciences, Department of Physics, 54140 Sakarya, Turkey highlights  The title compound was solved by means of X-ray diffraction, FT-IR and NMR.  HOMO–LUMO analysis, charge distributions and the total electron density were investigated.  The NLO and NBO analysis were carried out.  This paper presents a combined experimental and theoretical investigation. graphical abstract The contour map of electrostatic potential (ESP) surfaces for nicotinic acid [1-(2,3-dihydroxyphenyl)methyl- idene]hydrazide (obtained from B3LYP/6-311++G(d,p) level). article info Article history: Received 10 July 2013 Received in revised form 7 October 2013 Accepted 8 October 2013 Available online 17 October 2013 Keywords: Nicotinic acid X-ray diffraction FT-IR and NMR Ab initio calculations Electrostatic potential molecular surfaces abstract In this study, we reported a combined experimental and theoretical study on nicotinic acid [1-(2,3-dihy- droxyphenyl)methylidene]hydrazide (C 13 H 11 N 3 O 3 ) molecule. The title compound was prepared and char- acterized by 1 H and 13 C FT-NMR, FT-IR and single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2 1 /c with a = 6.2681(3) Å, b = 16.5309(7) Å, c = 12.4197(6) Å, a = 90°, b = 111.603(4)°, c = 90° and Z = 4. In addition, the molecular geometry, vibrational frequencies, gauge including atomic orbital (GIAO), continuous set of gauge transformations (CSGT), individual gauges for atoms in molecules (IGAIM) 1 H and 13 C NMR chemical shift values, natural bond orbital (NBO), nonlinear optical (NLO) and HOMO–LUMO analyses, molecular electrostatic potentials (MEPs) and thermodynamic properties of the title compound in the ground state were investigated by using Hartree–Fock (HF) and density functional theory (DFT/B3LYP) methods with 6-311++G(d,p). Besides, the hardness and electro- negativity parameters were obtained from HOMO and LUMO energies. Obtained results indicate that there is a good agreement between the experimental and theoretical data. Ó 2013 Elsevier B.V. All rights reserved. Introduction Compounds which include XC = NY structure are known as Schiff bases, which are usually synthesized from the condensation of primary amines and active carbonyl groups. Schiff bases are used as starting materials in the synthesis of important drugs, such as antibiotics and antiallergic, antiphlogistic, and antitumor sub- stances [1]. In recent years, schiff bases have been intensively investigated in many fields of chemistry and biochemistry, because of their coordination properties, diverse applications and versatile metal binding ability [2,3]. 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.10.030 ⇑ Corresponding author. Tel.: +90 264 295 6097; fax: +90 264 295 5950. E-mail address: davci@sakarya.edu.tr (D. Avcı). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 120 (2014) 323–331 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa