Novel route for the synthesis of azepine derivative using tin-based catalyst: Spectroscopic characterization and theoretical investigations Kollur Shiva Prasad a, * , Renyer A. Costa b , Adjane D.S. Branches b , Kelson M.T. Oliveira b a Chemistry Group, Manipal Centre for Natural Sciences, Manipal Academy of Higher Education, Manipal, Karnataka, 576 104, India b Department of Chemistry, Federal University of Amazonas (DQ-UFAM), 69077-000 Manaus, AM, Brazil article info Article history: Received 18 July 2018 Received in revised form 16 October 2018 Accepted 16 October 2018 Available online 23 October 2018 Keywords: Azepine Spectroscopy Electronic structure HOMO-LUMO DFT calculations abstract Synthesis of azepine-based compounds are of highly interest due to their vast applications in medicinal filed. In this work, is described the synthesis of a azepine-based derivative, 11-methoxy-6,6a-dihydro- 5H-dibenzo[b,e]azepine (MDDA) by new route using dibutyltin dilaurate (DBTDL) as catalyst. The structural elucidation of MDDA was done by FT-IR, 1 H NMR, and mass spectrometry techniques. Also is presented the experimental and theoretical DFT study of the vibrational, structural and quantum properties of MDDA using B3LYP exchange-correlation functional with 6-311G (2d, p) basis set. The theoretical DFT geometry optimization data was compared with the X-ray data in the associated liter- ature promoting a good comprehension of the structural arrangement. In complementation, mapped molecular electrostatic potential surface (MEPS), HOMO-LUMO orbitals and NBO energy calculations were also performed using the same calculation approach. The calculated UV spectrum is in good agreement with the experimental one, making the bands assignments possible. The comparative IR studies clearly confirmed the intermolecular hydrogen bonds of the proposed dimeric form for MDDA and also showed several characteristic vibrations within the molecular structure. © 2018 Published by Elsevier B.V. 1. Introduction Azepines and their derivatives such as Carbamazepine (CBZ) and Oxcarbazepine (OCBZ) are well-known anticonvulsant and anti- depressant drugs, respectively [1e3]. The latter compound, OCBZ, is also one of the important antiepileptic drug primarily used in the treatment of Parkinson's disease [4]. However, synthesizing mole- cules of this kind is not an easy task, as it involves complicated preparation procedure with expensive catalyst and special equip- ments [5]. Thus, it is always a challenging task for researchers to find simple synthetic approaches which are cost-effective. (see Scheme 1) Theoretical quantum models such as density functional theory (DFT) and advanced software make theoretical chemistry a powerful tool for the study of vibrational, structural and quantum properties of molecules. The improvement in the various physical and chemical properties of new materials or molecules depends on the computational methods, as it can be structurally designed prior to their synthesis [6e11]. In these regards, DFT calculations have proven to be particularly useful. In order to evaluate the electro- static interactions within the molecule or between the molecules, molecular electrostatic potential surfaces (MEPS) has been calculated. In this present study, the synthesis of an azepine derivative,11- methoxy-6,6a-dihydro-5H-dibenzo[b,e]azepine (MDDA) has been carried via new synthetic approach using DBTDL as catalyst, which was also used as catalyst in our recent work to synthesize a benz- imidazole derivative [12]. Further, this work emphasize on MDDA molecule from the theoretical view (geometry optimization and molecular electrostatic potential map surface, MEPS, calculations) based on experimental data (X-ray, UV, FTIR), providing a better description of its structure and a detailed investigation of the spectroscopic behavior by DFT calculations. To the best of our knowledge, theoretical molecular study that describing the HOMO- LUMO energies, geometry, NBO molecular electrostatic potential surface calculations, IR and UVeVis spectra by DFT approach was not previously reported for title compound. * Corresponding author. E-mail address: shivachemist@gmail.com (K. Shiva Prasad). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc https://doi.org/10.1016/j.molstruc.2018.10.050 0022-2860/© 2018 Published by Elsevier B.V. Journal of Molecular Structure 1178 (2019) 491e499