## 3 Results and Discussion
### Molecular Docking  
Molecular docking is a computational software regularly used to understanding protein-receptor interaction with complexes [17; 44]. The docking process was carried out by simulating the interaction of the Schiff base and their metal complexes with three types of protein-receptors; (M14) melanoma cancer (PDB = _2 OPZ_), (Ovar3) ovarian cancer (PDB = _3W2S_), and (HOP-62) (NSCLC) cancer (PDB = _1S9I_) which have selected according to the literature and previous studies [20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35]. The docking study results of the complexes are summarized in Table 4.  
We found that the compounds obtained a high negative value indicating practical bound to the protein. Obviously, Cu(II), Zn(II), and Co(II) complexes gave better results than the ligand. Both Cu(II) and Zn(II) complexes showed the best value compared to the rest of the complexes. We can discuss this binding by way of the following points:  
* Cu(II) complex was associated with three hydrogen bonds (\(\pi\)-H) with _2 OPZ_ protein, through the carbon 20 in the complex with the hexagonal ring of the TRP 323, and the five-pointed ring of the TRP 323 amino acid residue, and the benzene ring in the copper complex also associated with the LEU 307 amino acid residue, Table 5 shows the best possible conformation inside the Melanoma cancer _2 OPZ_ protein both the ligand and their metal complexes.
* Cu(II) complex was associated with four hydrogen bonds with _3W2S_ protein, through the carbon 27 in the complex with the ASP 855 amino acid residue by H-donor bond, nitrogen 19 in the complex with a nitrogen atom in MET 793 amino acid residue by H-acceptor bond, and the benzene ring in the copper complex also associated with the LEU 718 and GLY 796 amino acid residues by \(\pi\)-H bond, are tabulated in Table 5.
* Zn(II) complex was associated with two hydrogen bonds (\(\pi\)-H) with _1S9I_ protein, through the benzene ring in the complex with the ALA 220 and ASN 221 amino acid residues by \(\pi\)-H bond, are tabulated in Table 5 shows the best possible conformation inside the (NSCLC) cancer _1S9I_ protein both the ligand and their metal complexes.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Compounds**} & \multicolumn{3}{c}{**S**} \\ \cline{2-4}  & **Melanoma Cancer** & **Ovarian Cancer** & **(NSCLC) Cancer** \\  & **2 OPZ Protein** & **3W2S Protein** & _1S9I_ **Protein** \\ \hline L & \(-\)4.82 & \(-\)5.80 & \(-\)6.20 \\ Zn(II) & \(-\)5.51 & \(-\)6.55 & \(-\)7.39 \\ Cu(II) & \(-\)5.68 & \(-\)6.69 & \(-\)7.29 \\ Ni(II) & \(-\)3.79 & \(-\)3.86 & \(-\)4.06 \\ Co(II) & \(-\)5.50 & \(-\)6.32 & \(-\)6.97 \\ Mn(II) & \(-\)4.31 & \(-\)6.13 & \(-\)5.85 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Docking energies for three types of protein with the compounds.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Compounds**} & \multirow{2}{*}{**K\({}_{\text{b}}\) (M\({}^{-1}\))**} & \multirow{2}{*}{**\(\boldsymbol{\Lambda}\)max Free (nm)**} & \multirow{2}{*}{**\(\boldsymbol{\lambda}_{\text{max}}\) Bound (nm)**} & \multirow{2}{*}{**Type of Chromism**} \\ \hline Zn(II) & \(5\times 10^{5}\) & 326 & 321 blue-shift & Hyperchromic \\ Mn(II) & \(3.33\times 10^{5}\) & 300 & 295 red-shift & Hyperchromic \\ Ni(II) & \(8\times 10^{5}\) & 322 & 316 blue-shift & Hypochromic \\ Cu(II) & \(3.33\times 10^{5}\) & 294 & 299 red-shift & Hypochromic \\ Co(II) & \(4\times 10^{5}\) & 326 & 318 blue-shift & Hypochromic \\ \hline \hline \end{tabular}
\end{table}
Table 3: Absorption spectral titrations data.  
\begin{table}
\begin{tabular}{c c c} \hline
**Protein Receptor** & **Code** & **3D** & **2D** \\ \hline Ligand & & \\ \hline \end{tabular}
\end{table}
Table 5: The docking mode of the ligands and their metal complexes, 3D and 2D snapshot showing the hydrophilicity interaction to melanoma cancer target (_2 OPZ_) receptor, ovarian cancer target (3W2S) receptor and (NSCLC) cancer target (IS9J) receptor.