Structural investigation of (2E)-2-(ethoxycarbonyl)-3-[(4-methoxyphenyl)amino]prop-2-enoic acid: X-ray crystal structure, spectroscopy and DFT

The title compound, (2E)-2-(ethoxycarbonyl)-3-[(4-methoxyphenyl)amino]prop-2-enoic acid is characterized by means of X-ray crystallography, spectroscopic methods and quantum chemical calculations. The title compound crystallizes in centrosymmetric space group P2(1)/c. Moreover, the crystal structure is primarily stabilized through intramolecular N-H center dot center dot center dot O and O-H center dot center dot center dot O and intermolecular N-H-center dot center dot center dot O and C-H center dot center dot center dot O interactions along with carbonyl center dot center dot center dot carbonyl and C-H center dot center dot center dot C contacts. These intermolecular interactions are analysed and quantified by using Hirshfeld surface analysis, PIXEL energy, NBO, AIM and DFT calculations. The overall lattice energies of the title and parent compounds suggest that the title compound is stabilized by a 4.5 kcal mol(-1) higher energy than the parent compound. The additional stabilization force comes from the methoxy substitution on the title molecule, which is evident since the methoxy group is involved in the intermolecular C-H center dot center dot center dot-O interaction as an acceptor. The vibrational modes of the interacting groups are investigated using both experimental and theoretical FT-IR and FT-Raman spectra. The experimental and theoretical UV-Vis spectra agree well. The time dependent DFT spectra show that the ligand-to-ligand charge transfer is responsible for the intense absorbance of the compound. (C) 2016 Elsevier B.V. All rights reserved.