## 2 Results and Discussion
### Vibrational Analysis
The values of the electronegativity (x) were calculated by the expression \(\chi=(\mathrm{I}+\mathrm{A})/2\), where \(\mathrm{I}\) is the vertical ionization energy that is equal to minus the energy of the HOMO (\(\mathrm{I}=-\mathrm{E}_{\mathrm{HOMO}}\)), and \(\mathrm{A}\) is vertical electron affinity that is equal to minus the energy of the LUMO (\(\mathrm{A}=-\mathrm{E}_{\mathrm{LUMO}}\)) [27 ]. Variations in the intermolecular interactions produce changes in the dipole moment during the vibration, and therefore affect the infrared bands. In crystals, the infrared bands tend to be more intense when the fingerprinting intermolecular interactions are  
Figure 6: Experimental FT-Raman spectra of chalcones 1 and 2. Figure 7: Experimental spectra of ATR-FTIR of the chalcones 1 and 2.  
weak [10]. For this reason, as chalcone 2 has stronger fingerprinting intermolecular interactions than chalcone 1, it is expected that the infrared bands have lower intensities when compared with those of the chalcone 1. Moreover, in this region, it is possible to observe deformation modes of the methyl groups. In fact, _wagging_ vibrations and asymmetric deformations in the methyl groups are clearly observed in these substances between 1426 and 1490 cm\({}^{-1}\), as well as in the HYTHENYL chalcone [10]. The presence of the _target_ and substituted nitro groups caused subtle displacements in these vibrational modes among themselves, and, when compared with HYTHENYL, due to the effect of removing electrons from this group, which causes a displacement of electronic density and consequently a variation in the intensity and region of vibrational, assisted in the differentiation of the spectrum for chalcones 1 and 2. The carbonyl stretching modes (C=O1) for chalcones are in the range of 1594 to 1671 cm\({}^{-1}\). In both spectra, it is possible to observe that the stretching modes C=O1, of carbonyl, are associated with the stretching modes NO, CC, and C\(\alpha\)C\(\beta\), being in infrared observed in 1618 cm\({}^{-1}\) and 1636 cm\({}^{-1}\) for the chalcones, respectively. It is worth mentioning that the stretching modes C=O1 in the infrared spectra have a lower intensity than those observed in other classes of organic compounds. In addition, the presence of different functional groups can cause displacements in and characteristic intensities for each sample [10]. In the region with a scaled wavenumber greater than 2913 cm\({}^{-1}\) present, the molecular vibrations are associated with the symmetrical and asymmetrical stretching modes of the CH, CH3, and OH groups of the chalcones as well as those of the HYTHENYL chalcone [10]. It is noteworthy that the stretching modes of the OH hydroxyl in the infrared spectra have a lower intensity in the chalcone 2 than those observed in the chalcone 1. This effect is expected, since the intensity of the OH stretching band can increase when hydroxyl group is forming a hydrogen bond [10]. A complete description of all the modes that appear in the Raman and infrared spectra of the chalcones 1 and 2 is provided in Tables S5 and S6 (see supplementary material), respectively. In the experimental spectra of FT-Raman, the bands with higher absorption were related to the symmetrical and asymmetrical stretching modes of the NO\({}_{2}\) groups. The effect on the higher intensity of these bands is due to the presence of NO\({}_{2}\) groups' increasing polarizability (inducing a potential resonant effect among the oxygen directly linked to it) in these structures, which is more easily detected by the FT-Raman technique.