## 3 Results and Discussion
### Synthesis of the Metal Complexes
In each couple, one of the resonances was observed for the free ligand (the L2) and the other for the coordinated L2. The couples at 12.20/10.77 ppm and 12.32/10.87 ppm were observed for NH at the first and third positions. The couple at 5.68/5.31 ppm was observed for olefin proton 5. The three couples at 2.32 ppm (t.7.3)/2.25 (t.7.3) ppm, 1.54 ppm (sx, 7.6)/1.48 ppm (m), and 0.87 ppm (t, 7.3)/0.82 ppm (m) were observed for propyl protons (H-1\({}^{\prime}\)), (H-2\({}^{\prime}\)), and (H-3\({}^{\prime}\)), respectively. A singlet at 2.54 ppm was observed, which corresponds to DMSO-h6. It is interesting to note that all resonances were shifted for coordinated L2 compared to the free L2 but the shifts were higher for NHs. In PdL2, the singlets for NH-1 and NH-3 were upfield shifted by 1.43 and 1.44 ppm, respectively. The \({}^{13}\)C NMR solution spectrum of PdL2 showed seven groups of signals. The two signals with the highest chemical shift, at 176.02 ppm and 164.19 ppm, were for the C=S and C=O groups in PdL2, respectively. There was also a resonance at 161.09 ppm (free ligand), i.e., there was downfield shift of 2.97 ppm. This shows that the C=O group of the ligand participated in the coordination with Pd(II). In the CP NMR spectrum of PdL2, the signal for C=S was upfield shifted by 3.2 and 2.6 ppm. In the same spectrum, there were three signals for C=O, shown in Table 8. One was upfield shifted by 4.5 ppm and the other was downfield shifted by 2.2 ppm. This shows that the C=S and C=O groups of the ligand participated in the coordination with the palladium in two different ways. The ATR spectra of CuL2 and PdL2 showed the presence of H\({}_{2}\)O and/or OH\({}^{-}\). According to the solid-state NMR, clear shifts in the signals of the carbon atoms were observed in the complex of Cu(II) with L1, indicating the presence of the complex. There were also signals corresponding to the starting ligand L1, which may or may not be included in the second coordination sphere. In the case of ligand L2, the ligand itself showed doubled signals for the carbon atoms C-5, C-2\({}^{\prime}\), and C-3\({}^{\prime}\), possibly due to a different spatial arrangement of these atoms in the crystalline lattice of the ligand (Figure 4a). In the case of the Cu(II)L2 complex, the ligand signals could still be observed, accompanied by the complex signals. However, in this case, the DMSO in the complex was present as a ligand. Despite the presence of many C-1\({}^{\prime}\) signals around it in the CP spectrum (Figure 4b), the DMSO signal could be easily identified in the CPPI spectrum (Figure 4c). \begin{table}
\begin{tabular}{c c c c} \hline
**Atom** & \(\delta\)**(\({}^{13}\)C) ppm, L2** & **CuL2** & **PdL2** \\ \hline
1 (NH) & - & - & - \\ \hline
2 (C=S) & 176.08 & & 176.02 \\ \hline
3 (NH) & - & - & - \\ \hline
4 (C=O) & 161.22 & & 164.19 and 161.09 \\ \hline
5 & 103.06 & & 98.03 \\ \hline
6 & 156.74 & & 156.61 and 156.33 and 151.71 \\ \hline
1\({}^{\prime}\) & 33.21 & 33.24 & 33.56 and 33.14 \\ \hline
2\({}^{\prime}\) & 20.58 & 20.55 & 20.50 and 20.24 \\ \hline
3\({}^{\prime}\) & 13.26 & 13.25 & 13.20 \\ \hline \end{tabular} In DMSO-\(d\)6 solution.  
\end{table} 
Table 11: \({}^{13}\)C NMR spectral data (in ppm) for complexes of 6-propyl-2-thiouracil with Cu(II) and Pd(II). The \({}^{13}\)C spectrum of PdL2 obtained by cross-polarization (Figure 4d) showed unexpected results. There were multiple signals for each type of carbon atom in the ligand, indicating the presence of more than one palladium complex or a palladium complex with two ligands in the coordination sphere simultaneously. The representation of coordination binding sites for 6-methyl-2-thiouracil and 6-propyl-2-thiouracil with copper and palladium ions is shown in Figure 5.  
Figure 4: Solid-state \({}^{13}\)C NMR of the ligand L2 and its complexes: (**a**) \({}^{13}\)C CP spectrum of L2, (**b**) \({}^{13}\)C CP spectrum of Cu(II)L2, (**c**) \({}^{13}\)C CPI spectrum of Cu(II)L2, and (**d**) \({}^{13}\)C CP spectrum of Pd(II)L2.