## 4 Conclusions  
The complexation potential of 2,4-dTu and its derivatives was demonstrated for Au(III) and Cu(II), leading to the synthesis of new metal chelate complexes. A combination of various atomic and molecular spectroscopic techniques was used to determine the elemental compositions, as well as the possible structures of the proposed coordination compounds. The interpretation of the presented NMR data was the key factor for determining the possible type of ligands in the Au and Cu complexes. The antimicrobial activity of the newly formed complexes was studied in vitro against yeasts and Gram-positive and Gram-negative bacteria. The Cu(II) complex showed no significant improvement in the inhibition of most test-microorganisms, while the addition of Au(III) to 2,4-dithiouracil increased its antimicrobial effect, especially on _Staphylococcus aureus_ ATCC 25923, _Eterococcus faecalis_ ATCC 19433, and _Klebsiella pneumoniae_ ATCC 13883. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14156601/s1](https://www.mdpi.com/article/10.3390/app14156601/s1)]([https://www.mdpi.com/article/10.3390/app14156601/s1](https://www.mdpi.com/article/10.3390/app14156601/s1)), Figure S1: 1H NMR spectrum of 2,4-DTu; Figure S2: 13C NMR spectrum of 2,4-DTu; Figure S3: HSQC spectrum of 2,4-DTu; Figure S4: HMBC spectrum of 2,4-DTu; Figure S5: 1H-1H COSY spectrum of 2,4-DTu; Figure S6: 1H NMR spectrum of the Au complex; Figure S7: 1H NMR spectrum of the Cu complex; Figure S8: HSQC spectrum of the Au complex; Figure S9: HSQC spectrum of the Cu complex; Figure S10: Raman spectrum of 2,4-DTu; Figure S11: ATR spectrum of 2,4-DTu; Figure S12: Raman spectrum of the Au complex; Figure S13: \begin{table}
\begin{tabular}{l c c c c} \hline \hline \multirow{2}{*}{**Test Microorganisms**} & **DMSO** & **2,4-DTu** & **Cu(II)** & **Au(III)** \\ \cline{2-5}  & \multicolumn{4}{c}{**Inhibition Zone, mm**} \\ \hline _Staphylococcus aureus_ ATCC 25923 & - & \(14\pm 1.00\) & \(15\pm 0.58\) & \(19\,\,^{*}\pm 1.00\) \\ _Eterococcus faecalis_ ATCC 19433 & - & \(12\pm 1.00\) & \(13\pm 1.00\) & \(16\pm 0.58\) \\ _Listeria monocytogenes_ ATCC 8787 & - & \(12\pm 1.00\) & \(12\pm 0.58\) & \(14\pm 0.58\) \\ _Bacillus subtilis_ ATCC 6633 & - & \(11\pm 0.58\) & \(11\pm 0.58\) & \(13\pm 0.58\) \\ _Bacillus cereus_ ATCC 11778 & - & \(11\pm 0.58\) & \(11\pm 0.58\) & \(14\,\,^{*}\pm 0.58\) \\ _Escherichia coli_ ATCC 8739 & - & \(14\pm 0.58\) & \(15\pm 0.58\) & \(14\,\,^{*}\pm 1.00\) \\ _Salmonella enterica ssp. enterica_ ser. [PERSON] & - & \(14\pm 0.00\) & \(15\pm 0.00\) & \(15\pm 0.58\) \\ ATCC 13076 & - & \(13\pm 1.00\) & \(12\pm 0.58\) & \(15\pm 0.00\) \\ _Pseudomonas aeruginosa_ ATCC 9027 & - & \(12\,\,^{*}\pm 0.58\) & \(12\,\,^{*}\pm 0.58\) & \(14\,\,^{*}\pm 1.00\) \\ _Proteus vulgaris_ G & - & \(12\,\,^{*}\pm 0.58\) & \(11\,\,^{*}\pm 0.58\) & \(15\,\,^{*}\pm 0.58\) \\ _Klebsiella pneumoniae_ ATCC 13883 & - & \(12\,\,^{*}\pm 0.58\) & \(11\,\,^{*}\pm 0.58\) & \(15\pm 0.58\) \\ _Candidia albicans ATCC 10231 & - & \(10\pm 0.58\) & \(11\,\,^{*}\pm 0.58\) & \(12\pm 0.58\) \\ _Saccharomyces cerevisiae_ & - & \(11\pm 1.00\) & \(10\pm 0.00\) & \(12\pm 1.00\) \\ \hline \hline \end{tabular}  
* Well diameter—7 mm; \({}^{*}\) Inhibition zone with single cell colonies.  
\end{table} 
Table 7: Antimicrobial activity of 2,4-DTu and its Cu(II) and Au(III) complexes. ATR spectrum of the Au complex; Figure S14: Raman spectrum of the Cu complex; Figure S15: ATR spectrum of the Cu complex; Figure S16: \({}^{1}\)H solid state NMR of Au complex; Figure S17: \({}^{13}\)C CP MAS NMR of Au complex; Figure S18: \({}^{13}\)C CPI MAS NMR of Au complex; Figure S19: \({}^{1}\)H solid state NMR of Cu complex; Figure S20: \({}^{13}\)C CP MAS NMR of Cu complex; Figure S21: \({}^{13}\)C CPPI MAS NMR of Cu complex. Conceptualization, P.M. and P.P. ; methodology, P.M.; formal analysis, P.P., N.B., D.S., S.T., E.V. ; investigation, S.T., N.B., E.V. ; resources, N.B.