## 3 Results and Discussion  
### Global Reactivity Descriptors  
Analysis of density functional theory descriptors gives more information about the characteristics of stability, electrophilicity, and nucleophilicity of the compounds. Therefore, the global reactivity descriptors were calculated for the 43 compounds under investigation using the DFT method with the B3 LYP/6-31G basis set. The results obtained are summarized in Table 3.  
Note: \(\Delta\)E: energy gap, \(\eta\): chemical hardness, S: chemical softness, \(\mu\): chemical potential, \(\omega\): electrophilicity, and N: nucleophilicity.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Compd** & **HOMO (eV)** & **LUMO (eV)** & \(\Delta\)**E (eV) \({}^{\text{a}}\)** & **n (eV) \({}^{\text{a}}\)** & **S** & \(\mu\) & \(\omega\)**(eV)** & **N (eV)** \\ \hline
**1** & \(-6.38\) &  
Table 3 shows that all compounds have a similar trend in all descriptors except for **21** and the reference compounds **1** and **2**. Affinity (A = \(-\)E\({}_{\text{LUMO}}\)) and potential ionization (I = \(-\)E\({}_{\text{HOMO}}\)) are related to one-electron orbital energies of HOMO and LUMO, respectively. They can be used to measure electronegativity and hardness. Compound **21** has the lowest potential ionization (4.94 eV) while the reference compounds **1** and **2** have the larger affinity (1.63 eV and 1.29 eV, respectively). Therefore, compound **21** acts as a good electron donor (the strongest nucleophile, N = 3.80 eV) while the reference compounds **1** and **2** act as good electron acceptors (the strongest electrophiles; \(\omega\) = 3.38 and 3.00 eV, respectively).  
The \(\Delta\)E is used to measure the chemical reactivity and the kinetic stability of molecules. A large \(\Delta\)E gap indicates high kinetic stability, low reactivity, and a poorly polarizable molecule (i.e., a weak reactivity). The lowest \(\Delta\)E value was observed for compounds **19** and **21** (4.02 and 4.06 eV, respectively), and the highest \(\Delta\)E was seen for the reference compounds **1** and **2** (4.75 and 5.67 eV, respectively). Such a result indicates that compounds **19** and **21** are highly polarizable and therefore develop a high reactivity. The high chemical hardness and low chemical softness are indicators of the overall stability of the system. The lowest \(\eta\) was observed for compounds **19** and **21** (2.01 and 2.03 eV, respectively), while the reference compounds **1** and **2** showed the highest chemical hardness as 2.37 and 2.83 eV, respectively. On the other hand, compounds **19** and **21** showed the highest chemical softness (S = 184.41 and 182.20), and the reference compounds **1** and **2** showed the smallest S values (155.96 and 130.71, respectively). Clearly, compounds **19** and **21** are the softest and most reactive molecules compared to the others.  
The electronic chemical potential (\(\mu\)) reflects the charge transfer from a system with a high electronic chemical potential to another with a lower \(\mu\). Compound **21** has the highest \(\mu\) (\(-\)2.90 eV), while the references **1** and **2** have the lowest values as \(-\)4.00 eV and \(-\)4.12 eV, respectively. According to these results, **21** can exchange electron density with the environment efficiently and better than other compounds.  
In terms of nucleophilicity, organic molecules can be classified as strong (N > 3 eV), moderate (2.0 eV \(\leq\) N \(\leq\) 3.0 eV), and marginal nucleophiles (N \(<\) 2.0 eV) [41; 45]. The biological activity of the anti confine analogues can be predicted using the electrophilicity (\(\omega\)) and nucleophilicity (N) indexes. In addition, electrophilicity (\(\omega\)) provides important information about the reactivity of organic compounds that are involved in polar reactions (\(\omega\) > 2.0 eV) [41; 45]. The results obtained indicated that compound **21** (N = 3.72 eV) is the strongest nucleophile, while the reference compounds **1** and **2** (\(\omega\) = 3.38 and 3.00 eV, respectively) are the strongest electrophiles.