## 3 Results and Discussion
### Computational Study
#### 3.3.4 Quantum Theory of Atoms in Molecules (QTAIM)  
Figure 7 shows the AIM graph with all of the BCPs displayed. In the reaction pathways of H(54)\(\cdots\)C(50), Cl(19)\(\cdots\)H(8), H(8)\(\cdots\)C(50), H(24)\(\cdots\)C(63), H(22)\(\cdots\)C(49), and H(5)\(\cdots\)C(55), there are six BCPs (BCP147, BCP140, BCP131, BCP108, BCP84, and BCP77) between clonidine and tetraphenylborate. The total electron density \(\rho\)(r), Laplacian electron density \(\
abla^{2}\rho\)(r), and electron energy density H(r), which is composed of the electron potential energy density V(r), characterize the nature of chemical bonds and molecular reactivity. Table 5 lists the values of the AIM topological parameters for the complex of clonidine and tetraphenylborate. As a result, the higher the (r) value at the BCP, the greater the concentration of electronic charge on the surface at this point and the stronger the considered contact. It is a lot smaller than in covalent bonding, where the value of \(\rho\)(r) is about \(\sim\)10\({}^{-1}\) au. For hydrogen bonding, the value of \(\rho\)(r) is \(\sim\)10\({}^{-2}\) and for van der Waals interactions, the value of \(\rho\)(r) is \(\sim\)10\({}^{-3}\) au. The absolute potential energy density \(|\)V(r) \(|\) /G(r), the (r) value at the BCP of interacting atoms and the value of its Laplacian \(\
abla^{2}\rho\)(r), the total energy density H(r), and the ratio  
Figure 7: Topological atoms in molecules (AIM) graph of the clonidine–tetraphenylborate complex. of the absolute potential energy density to the kinetic energy density 1V(r) /G(r) are the most commonly used terms to describe the nature and strength of bonding interactions. In order to explore topological characteristics, such as the Laplacian of the electron density (\(\
abla^{2}\)\(\rho\)(r)), potential energy (V(r)), and electron density (\(\rho\)(r)), among others. This approach resulted in the formation of a density gradient that originates from a location between two atoms, which is referred to as the critical bond point (BCP). The examination of this critical point BCP reveals the type and nature of the interaction between the clonidine and tetraphenylborate ions as a result of their interaction with their active sites. It should be remembered that the total electronic energy (H (r)) is equal to the sum of G(r) and V(r)) and was estimated from the BCP using Equation (9). \[\mathrm{H(r)=G(r)+V(r)}, \tag{9}\]  
The interaction energy can be determined using the equation provided by Equation (10). \[\mathrm{E_{int}=\frac{V(r)}{2}}, \tag{10}\]  
The topological characteristics that characterize the three types of bonding interactions are as follows: (i) \(\
abla^{2}\)\(\rho\)(r) 0, H(r) 0, 1V(r) /G(r) > 2 for shared interactions (covalent bonding); (ii) \(\
abla^{2}\)\(\rho\)(r) > 0, H(r) > 0, 1V(r) /G(r) <1 for closed-shell interactions (van der Waals interactions and weak electrostatic H-bonds); (iii) \(\
abla^{2}\)\(\rho\)(r) > 0, H(r) \(<\) 0, 1 1V(r) /G(r) < 2 for (H-bonding of partially covalent nature). The parameters of the QTAIM analysis are shown in Table 4. \(\
abla^{2}\)\(\rho\)(r) >0 is present in all interactions, indicating that they are non-covalent. This indicates the presence of intermolecular interactions. For the complex, the values of \(\
abla^{2}\)\(\rho\)(r) and H(r) are positive, and the absolute potential energy density 1V(r) /G(r) is less than 1, indicating that the interactions are van der Waals interactions and weak electrostatic H-bonds. The strengths of interactions between the clonidine and tetraphenylborate are represented by the values of the electron density \(\rho\)(r). The values of \(\rho\)(r) are 0.00567 (u.a), 0.0151 (u.a), 0.00831 (u.a), 0.0213 (u.a), 0.0101 (u.a), and 0.00668 (u.a) for BCP147, BCP140, BCP131, BCP108, BCP84 and BCP77, respectively. Therefore, the values of \(\rho\)(r) indicate that N-H\(\cdots\)C and N-H\(\cdots\)Cl interacts more than C-H\(\cdots\)C and C-H\(\cdots\)Cl with the active site of the two ions.