Experimental FTIR and FT-Raman and theoretical studies on the molecular structures of monomer and dimer of 3-thiopheneacrylic acid

This work presents an experimental and theoretical investigation on the properties of 3-thiopheneacrylic acid (3TAA) by using the FT-Raman and FT-IR spectra in the solid state. The structural, electronic, topological and vibrational properties of 3TAA were theoretically studied by using the hybrid B3LYP method with the 6-311++G (d,p) basis set. The complete assignments of the bands observed in both spectra were performed taking into account the presence of both monomer and dimer species of the acid. Two bands observed at 1682 and 1625 cm(-1) attributed to the C=C and C=O stretching modes, respectively support the presence of the dimeric species in the solid phase. The percentages of intermolecular interactions are analyzed by Fingerprint plots of Hirshfeld surface. The natural bond orbital (NBO), atoms in molecules (AIM), frontier molecular orbitals (FMOs) and molecular electrostatic potential surface (MEPs) calculations were employed to determine the structural properties while the chemical selectivity or reactivity sites were revealed by using the Fukui functions. The GIAO and time dependent density functional theory (TD-DFT) methods were used to predict the H-1 and C-13 NMR and electronic spectra of the acid. The diagrams of the density of state of that acid have been also presented. Finally, reasonable correlations between experimental and theoretical vibrational spectra were found. Effect of positioning and orientation of the acrylic group on the inhibitor characteristics on human MAOB enzyme of stable conformers of 3TAA is investigated in comparison with that of 3-2TAA and four selective inhibitors via molecular docking. (C) 2017 Elsevier B.V. All rights reserved.