## 3 Results and Discussions
### Computational Methods  
The experimental results indicate a enhanced surface coverage of the electrode and a reduction in corrosion currents in the presence of EEA4 NB. Therefore, from a computational standpoint, it becomes imperative to assess the corrosion inhibition potential of EEA4 NB, including its anions and cations. Theoretical methods, particularly quantum chemical calculations, have consistently demonstrated their utility in unraveling the intricate mechanisms underlying the inhibition of materials. The calculated values for E\({}_{\text{HOMO}}\) (highest occupied molecular orbital energy), E\({}_{\text{LUMO}}\) (lowest unoccupied molecular orbital energy), energy gap (E\({}_{\text{gap}}\)), hardness (\(\eta\)), electronegativity (\(\chi\)), polarizability (p), dipole moment (\(\mu\)), and fraction of the transferred electrons (\(\Delta\)N) are presented in Table 3.  
The highest E\({}_{\text{HOMO}}\) value was observed for the anion, indicating superior inhibition efficiency. This can be attributed to its ability to accept electrons from the \(d\)-orbital of the metal, form a feedback bond. The reduction in separation energy (E\({}_{\text{gap}}\)) corresponds to an increase in the molecule's inhibition efficiency. Notably, the anion exhibits the lowest E\({}_{\text{gap}}\) value, signifying higher reactivity compared to EEA4 NB and the cation. The electron density distributions of the frontier orbitals play a crucial role in determining the adsorption preference of inhibitors. The HOMO identifies regions of the molecule prone to donating electrons to electrophilic species, while the LUMO predicts regions with a high tendency to accept electrons from nucleophilic species. The calculated HOMO-LUMO electron density distributions for EEA4 NB, the anion, and the cation are illustrated in Figure 6. In EEA4 NB and the anion, the HOMO is strongly localized on O4 and O5 atoms (Figure 7), while the LUMO is distributed throughout the aromatic cycles and NO\({}_{2}\)-groups. In the cation, both HOMO and LUMO are predominantly located on the O20 and C22 atoms. Polarizability plays a significant role in the corrosion inhibition process [27]. Higher values of polarizability, defined as the ratio of the induced dipole moment to the intensity of the electric field, facilitate the adsorption process of inhibitors on a metal surface. The calculated values of polarizability exhibit the following trend: EEA4 NB > anion > cation. This same trend is observed in the calculated dipole moments of the potential inhibitors under study (Table 3). Dipole moment is another frequently employed parameter in corrosion inhibition studies, and a high dipole moment likely enhances adsorption on the metal surface [27]. Absolute hardness and softness are important properties for assessing molecular stability and reactivity. Chemical hardness (\(\eta\)) essentially indicates the resistance to the deformation or polarization of the electron cloud of atoms, ions, or molecules under a small perturbation of a chemical reaction [28]. In the context of material corrosion, the softest base inhibitors prove to be the most effective, and the portions of the inhibitor with the highest softness and lowest hardness are particularly useful [27]. The results presented in Table 4 show that the anion exhibits the lowest hardness among the various potential inhibitors. Electronegativity (\(\chi\)) measures the ability of a group of atoms to attract electrons towards itself when chemically combined with another atom. In the context of corrosion inhibition, effective inhibitors are those that donate electrons to the metallic surface. Therefore, it is anticipated that electronegativity values will decrease with the improvement of inhibitive efficiencies [27]. The anion with the lowest electronegativity value demonstrates