Structural and spectroscopic investigation of the chalcones
(E)-1-(4-aminophenyl)-3-(4 `-ethoxyphenyl)-prop-2-en-1-one and
(E)-1-(aminophenyl)-3-(4 `-methoxyphenyl)-prop-2-en-1-one
VIBRATIONAL SPECTROSCOPY, (2020)DOI: 10.1016/j.vibspec.2020.103118
Abstract
In this study, two 4'-aminochalcones with structural similarity were
structurally characterized using the NMR technique of H-1 and C-13.
Polycrystalline samples of these chalcones were analyzed by FT-Raman and
ATR-FTIR spectroscopy at room temperature in the regions 40-4000 cm(-1)
and 400-4000 cm(-1), respectively. The DFT calculations using the B3LYP
functional with 6-311 G(d,p) basis set were performed, revealing the
optimized molecular geometry and the vibrational wavenumbers for these
chalcones. Conformational analysis was done from the optimized
structures to obtain different conformers. The calculated harmonic
vibrational wavenumbers were scaled to improve the agreement between
theoretical and experimental wavenumbers. A complete vibrational
assignment using Potential Energy Distributions (PED) was provided for
the observed Raman and infrared spectra. The scaled wavenumbers were
found to be in good agreement with experimental wavenumbers.
Furthermore, a comparative structural and vibrational analysis was
performed. The structural analysis allowed us concluding that in
addition to differences in the position 4' - where one chalcone has a
methoxy group and the other, an ethoxy group - the molecular
conformation of them is significantly different, especially regarding
the torsion angles linking the enone chains with the rings of these
chalcones. The vibrational analysis allowed us to identify all Raman and
infrared bands of the two chalcones, highlighting the main differences
and correspondences between them.