## 3 Results and Discussion
### Synthesis of the Metal Complexes
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Assignment** & **L1** & **CuL1** & **PdL1** \\ \hline v(OH) & - & - & 3442 \\ \hline v(NH) & 3115 sh & 3115 & 3111 \\ \hline v(NH) & 3080 & 3080 & 3071 \\ \hline v(=CH) & 3014 & 3003 & 3052 \\ \hline v(C=O) & 1676 m & 1637 & 1678 \\ \hline  & 1560 w & 1559 & 1559 \\ \hline v(C=S) & 1242 & 1242 & 1244 \\ \hline  & 1167 s & 1167 & 1168 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Selected experimental IR data (in KBr, wavenumber in cm\({}^{-1}\)) for 6-methyl-2-thiouracil and its complexes. The \({}^{1}\)H NMR and \({}^{13}\)C NMR spectra in the DMSO-d6 solution of CuL1 had the same values of chemical shift as those of L1, but the solid-state NMR differentiated between them (see Tables 6-8 and Figure 3). The \({}^{13}\)C NMR spectrum of the L1 registered with the cross-polarization (CP) experiment showed five signals. Two of them were observed for the C=S and C=O groups at 174.6 and 163.0 ppm, respectively. In the \({}^{13}\)C NMR solid-state spectrum of CuL1, the two couples at 171.7/174.8 ppm and 162.9/169.5 ppm were observed for the C=S and C=O groups, respectively. This \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Atom**} & **L1** & **CuL1** & **PdL1** \\  & **(6-Methyl-2-Thiouracil)** & **Multiplicity (J, Hz)** & **Multiplicity (J, Hz)** \\ \hline
1 (NH) & 12.29 s & 12.24 s and 10.80 \\ \hline
2 (C=S) & - & - & - \\ \hline
3 (NH) & 12.29 s & 12.29 s & 12.30 s and 10.86 \\ \hline
4 (C=O) & - & - & - \\ \hline
5 & 5.68 & 5.68 s & 5.68 s and 5.31 \\ \hline
6 & - & - & - \\ \hline
1\({}^{\prime}\) & 2.06 & 2.07 & 2.07 and 2.01 \\ \hline DMSO-H6 & & 2.54 s & 2.54 s \\ \hline \hline \end{tabular}
\end{table} 
Table 6: \({}^{1}\)H NMR spectral data (in ppm) for complexes of 6-methyl-2-thiouracil with Cu(II) and Pd(II). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Atom**} & \multirow{2}{*}{\(\delta\)**(\({}^{13}\)C) ppm**} & **DEPT-135** & \(\delta\)**(\({}^{1}\)H) ppm** & **Multiplicity (J, Hz)** & \({}^{1}\)**H-\({}^{1}\)H** & **H-\({}^{1}\)H** & **H-\({}^{1}\)H** \\ \hline
1 (NH) & & 12.29 & s & & \\ \hline
2 (C=S) & 175.87 & C & & & \\ \hline
3 (NH) & & 12.29 & s & & \\ \hline
4 (C=O) & 161.06 & C & & & \\ \hline
5 & 103.72 & CH & 5.68 & d (0.9) & 7 & 4 b, 6, 7 \\ \hline
6 & 153.20 & C & & & \\ \hline
1\({}^{\prime}\) & 18.11 & CH\({}_{3}\) & 2.06 & d (0.7) & 5 & 5, 6 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: \({}^{1}\)H and \({}^{13}\)C NMR spectral data and \({}^{1}\)H-\({}^{1}\)H COSY and HMBC correlations for **6-methyl-2-thiouracil** [600.13 MHz (\({}^{1}\)H) and 150.903 MHz (\({}^{13}\)C)] a.  
means that the resonance for C=S was upfield shifted by 2.9 ppm, and the signal for C=O was downfield shifted by 6.5 ppm, respectively. This shows that the C=S and C=O groups of the ligand participated in the coordination with the copper. The two couples at 104.7/105.4 ppm and 154.0/156.4 ppm (Table 8), were observed for the carbon atom in positions 5 and 6, respectively. The \({}^{1}\)H NMR solution spectrum of PdL1 showed that the signals for the two amine protons (H-1 and H-3) were upfield shifted by 1.49 and 1.43 ppm. Also, all resonances of the free ligand are present in excess; this could be from the remaining reagent L1 or from the decomposition of PdL1 in the solution. In the \({}^{13}\)C NMR solution spectrum of PdL1, only methyl and olefin resonances of the coordinated ligand can be seen; the others are indistinguishable from the noise. This once again shows the limited solubility of the complexes. The \({}^{1}\)H NMR spectrum of 6-propyl-2-thiouracil (L2) showed six signals: two broad singlets at 12.20 ppm (H-1) and 12.31 ppm (H-3) and the olefin proton at 5.67 ppm (H-5)