## 2 Results and Discussion
### Quantum Chemical Parameters  
The molecular orbital frontier theory developed by [PERSON] in the 1950s plays a key role in the understanding of chemical reactivity [10]. HOMO is the most external orbital that contains electron donors, and LUMO is the most internal orbital that contains free places to accept electrons. The chemical behavior of the chalcones can be predicted by the following parameters: HOMO energy, LUMO energy, energy difference (\(\Delta\)E = \(-\)ELUMO \(-\) EHOMO), vertical ionization energy (I-EHOMO), vertical affinity of electrons (A = \(-\)ELUMO), chemical potential (\(\mu\) = \(-\)(I + A)/2), electronegativity (\(\eta\) = \(-\mu\)), overall hardness (\(\eta\) = \((I-A)\)/2) and electrophilicity index (\(\omega\) = \(\mu^{2}\)/2\(\eta\)) [10]. These quantum chemical parameters for the optimized geometries of the substances and the graphical structures of the molecular orbitals (Table 2). \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Chalcone** & **EHOMO** & **ELUMO** & **\(\Delta\)E** & **I** & **A** & \(\mu\) & \(\chi\) & \(\eta\) & \(\omega\) \\ \hline
**1** & \(-\)5.74 & \(-\)2.44 & 3.30 & 5.74 & 2.44 & \(-\)4.09 & 4.09 & 1.65 & 5.07 \\
**2** & \(-\)5.83 & \(-\)2.76 & 3.07 & 5.83 & 2.73 & \(-\)4.30 & 4.30 & 1.54 & 6.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Quantum chemical parameters for optimized geometries of chalcones in (eV). Figure 3: Cyclic voltammograms obtained for chalcone 1 (**a**) and 2 (**b**) in dichloromethane at 50 mV s\({}^{-1}\) and at room temperature (\(\cong\)25 \({}^{\circ}\)C). According to Figure 77, the aromatic ring A of the chalcones acts as an electron donor and the ring B acts as an electron acceptor, which was already expected, since the ring A has methoxy donor groups and the aromatic ring B has nitro (NO\({}_{2}\)) withdrawal groups with a different substitution pattern for the molecular structures of the chalcones. The values of the energy gap, hardness, and chemical potential in chalcone 2 are lower than the values found for chalcone 1. Therefore, the reduction in these chemical parameters indicates that the reactivity of chalcone 2 is higher than that observed in chalcone 1. Consequently, chalcone 2 has a better electrophilic character than chalcone 1, as observed in the electrophilicity index values of these molecules (6.00 eV for chalcone 2 versus 5.07 eV for chalcone 1). A possible explanation for this result can be attributed to the nature of the intramolecular charge transfer by the resonance effect between nitrogen and the two oxygen atoms of its structure and by the difference in the pattern of _target_ substitution and _for_ oriented nitro groups present [??]. For the chalcone 1, the electron removal effect of the NO\({}_{2}\) group acts on the pi electrons (\(\pi\)) in the B ring leaving the oxygen with higher charge density, which leads to an increase in the electronic polarizability of the NO\({}_{2}\) group and, consequently, a decrease in the polarizability of the connections with the rest of the structure. For the chalcone 2, the nature of the intramolecular charge transfer occurs more easily due to the fact that it has a flatter structure than the chalcone 1, thus allowing greater conjugation and displacement of the system \(\pi\)\(\pi\)\(\pi^{\star}\) (of the HOMO and LUMO orbitals) than with the carbonylic system (C=C-C=O) caused by a possible resonance effect, as can be seen in Figure 78b. It is worth remembering that ring A of the chalcones is made up of electron donor groups and can influence the stability and/or reactivity of each molecule.