## 3 Results and Discussion
### Theoretical Calculations
The energy values \(E_{2}\) for the interaction between the filled orbital \(i\) (donors) and the vacant orbital \(j\) (acceptors) or other molecular subsystem, calculated according to the theory of the second order perturbation, Equation (1), predicts the occurrence of delocalization or hyperconjugation [55; 56]. The higher the value of \(E_{2}\), the more intense the interaction between electron donors and the greater the degree of conjugation of the whole system [57]. \[E_{2}=\Delta E_{ij}=q_{i}\frac{F(i,j)^{2}}{\varepsilon_{j}-\varepsilon_{i}} \tag{1}\]  
\(q_{i}\) = Occupation or electronic density of the donor orbital. \(E_{i}\) and \(E_{j}\) are the diagonal elements and \(F(i,j)\) is the element of the Fock NBO diagonal matrix. Therefore, we calculated the hyperconjugative interaction and density transfer of lone pair electron (LP) of the N\({}_{3}\) and N\({}_{12}\) atoms to neighboring \(\pi\) antibonding orbitals. Similarly, the conjugation of carbonyl groups to neighboring atoms via \(\pi^{\bullet}\rightarrow\pi^{\bullet}\), see Table 7. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Acceptor not Lewis**} & \multirow{2}{*}{**Type**} & \multirow{2}{*}{**Electronic Density**} & \multirow{2}{*}{**Hybridization**} & \multicolumn{3}{c}{**Contribution of Natural Atomic Orbitals (\%)**} \\ \cline{5-6}  & & & & & **s** & **p** & **d** \\ \hline C\({}_{4}\)-O\({}_{21}\) & \(\sigma^{\bullet}\) & 0.00892 & 0.8036 (\(sp^{2.01}\))C \(-\) 0.5952 (\(sp^{1.43}\))O & C & 33.23 & 66.68 & 0.09 \\  & & & O & 41.00 & 58.65 & 0.34 \\ \hline C\({}_{4}\)-O\({}_{21}\) & \(\pi^{\bullet}\) & 0.35268 & 0.8357 (\(sp^{1.00}\))C \(-\) 0.5492 (\(sp^{1.00}\))O & C & 0.01 & 99.81 & 0.18 \\  & & & O & 0.01 & 99.69 & 0.31 \\ \hline C\({}_{6}\)-O\({}_{22}\) & \(\sigma^{\bullet}\) & 0.00782 & 0.8078 (\(sp^{2.31}\))C \(-\) 0.5895 (\(sp^{1.38}\))O & C & 30.22 & 69.68 & 0.11 \\  & & & O & 41.88 & 57.80 & 0.01 \\ \hline C\({}_{6}\)-O\({}_{22}\) & \(\pi^{\bullet}\) & 0.20945 & 0.8137 (\(sp^{99.99}\))C \(-\) 0.5813 (\(sp^{99.99}\))O & C & 0.01 & 99.84 & 0.14 \\  & & & O & 0.02 & 99.67 & 0.31 \\ \hline C\({}_{11}\)-O\({}_{23}\) & \(\sigma^{\bullet}\) & 0.00754 & 0.8085 (\(sp^{2.30}\))C \(-\) 0.5885 (\(sp^{1.38}\))O & C & 30.26 & 69.63 & 0.11 \\  & & & O & 41.89 & 57.79 & 0.32 \\ \hline C\({}_{11}\)-O\({}_{23}\) & \(\pi^{\bullet}\) & 0.19366 & 0.8177 (\(p^{1.00}\))C \(-\) 0.5756 (\(p^{1.00}\))O & C & 0.00 & 99.85 & 0.15 \\  & & & O & 0.00 & 99.69 & 0.310 \\ \hline C\({}_{15}\)-C\({}_{18}\) & \(\sigma^{\bullet}\) & 0.02406 & 0.7121 (\(sp^{1.38}\))C \(-\) 0.7021 (\(sp^{1.51}\))C & C & 35.30 & 64.66 & 0.04 \\  & & & C & 39.87 & 60.10 & 0.03 \\ \hline C\({}_{15}\)-C\({}_{18}\) & \(\pi^{\bullet}\) & 0.24133 & 0.6949 (\(p^{1.00}\))C \(-\) 0.7191 (\(p^{1.00}\))C & C & 0.00 & 99.94 & 0.06 \\  & & & C & 0.00 & 99.95 & 0.05 \\ \hline C\({}_{2}\)-S\({}_{19}\) & \(\sigma^{\bullet}\) & 0.05230 & 0.6683 (\(sp^{2.38}\))C \(-\) 0.7439 (\(sp^{5.04}\))S & C & 29.51 & 70.38 & 0.10 \\  & & & S & 16.44 & 82.84 & 0.73 \\ \hline C\({}_{27}\)-O\({}_{44}\) & \(\sigma\) & 0.02955 & 0.8213 (\(sp^{3.02}\))C \(-\) 0.5705 (\(sp^{2.01}\))O & C & 24.82 & 74.97 & 0.21 \\  & & & O & 33.17 & 66.76 & 0.07 \\ \hline N\({}_{12}\)-H\({}_{31}\) & \(\sigma^{\bullet}\) & 0.02603 & 0.5110 (\(sp^{2.52}\))N \(-\) 0.8596 (\(sp^{99.89}\))H & N & 28.02 & 71.96 & 0.02 \\  & & & H & 99.89 & 0.11 & \\ \hline N\({}_{3}\)-H\({}_{30}\) & \(\sigma\) & 0.01822 & 0.5184 (\(sp^{2.61}\))N \(+\) 0.8551 (\(sp^{99.90}\))H & N & 27.68 & 72.29 & 0.02 \\  & & & H & 99.90 & 0.10 & \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Occupation of natural bond orbitals (NBO) no Lewis and hybrids for **4c** calculated by the DFT/B-3 LYP/6-31G(d,p) method for the representative atoms. In Table 7, the important contribution of LP N \(\rightarrow\)\(\pi^{\bullet}\) interactions to the overall stability of the system is observed. Stability explained by the intramolecular electron transfer that occurs with these interactions.