Based on the obtained experimental data, the authors proposed a probable scheme for obtaining the Cd(II) and Hg(II) complexes with 2-thiouracil and 2,4-dithiouracil. This indicates that the ligand forms a bidentate chelation, involving the nitrogen atom in the third position and the sulfur atom in the second position. [PERSON] et al. have shown that thiouracil-containing complexes are effective antitumor and arthritic  
Figure 1: Different applications of 2-thiouracil and its derivatives and their metal complexes (antithyroid drugs [2]; antitumor [3]). compounds in vivo [20]. Initial findings from testing for antiarthritic activity in rats regarding the new complexes were also disclosed, demonstrating that certain complexes exhibit greater efficacy or lower toxicity compared to current clinically utilized gold(I) thiolates. Recently, [PERSON] and [PERSON] presented a review about the gold complexes with N, S, P, C donor ligands and with oxygen-based ligands [21]. [PERSON] and [PERSON] studied the conformations, adsorption sites, and orientation of 2-thiouracil on gold substrates at different pH values using SERS (surface-enhanced Raman scattering) and DFT calculations [22]. The use of spherical gold nanoparticles, modified with biologically active molecules, shows considerable promise for diverse medical applications [23]. Specifically, considering the established uses of 2-thiouracil (2-TU) in the treatment of hyperthyroidism and skin cancer, the compound 2-TUAuNPs (gold nanoparticles) stands out as a potential drug candidate for these conditions, providing the benefit of markedly reduced side-effects [23]. [PERSON] et al. presented the antitumor properties of gold complexes with biologically relevant ligands [24]. New anionic _bis_(thiolate)gold(I) complexes were obtained by [PERSON] et al. [25]. Recently, [PERSON] et al. published a review that explored the properties of molecular gold strings consisting of a theoretically infinite set of monomeric gold complexes, which are held together by aurophilic interactions, based on a direct gold-gold contact [26]. The synthesis of Rh(II), Ir(III), Pd(II), and Pt(II) complexes with dithiouracil was described [27], as their structures were determined by means of UV-Vis and IR spectroscopy and compared to the structures of some pyrimidine-containing complexes. The chelating ligands in the corresponding complexes bind to rhodium or iridium by forming octahedral structures, while their coordination with palladium and platinum leads to the formation of square planar complexes. In both cases, the ligand utilizes the N(3) and the C=S moieties to bind, although in the case of the divalent metals, the ligand is anionic. The synthesis of new complexes of Pt(IV) [28] and Pt(II) [29] with 2-thiouracil, 4-thiouracil, and 2,**4**-thiouracil was also published. Many authors have reported the in vitro antimicrobial activity of different complexes of metal ions with thiouracil derivatives against Gram-negative and Gram-positive bacteria, filamentous fungi, and yeasts [18; 19; 30; 31; 32; 33; 34; 35]. Metal complexes of thiouracil derivatives have also exhibited cytotoxic effects against various tumor cell lines [17; 30; 36; 37; 38]. [PERSON] and [PERSON] (2024) published a review focused on the synthesis and the biological activities of 2-thiouracil and its derivatives [39]. The possible coordination of 2,4-dithiouracil resembles its non-sulfur derivatives, and the schematic representations can be found in our previous paper [32]. Some complexes exhibit a monodentate coordination binding through atoms, such as S (e.g., Cu(I), Au(I), Pt(IV) complexes) [17; 20; 28], and/or forming bidentate chelate through N3 and S2 (e.g., Cu(II), Cd(II), Hg(II), Pd(II), Pt(II), Pt(IV), Rh(III), Ir(III) complexes) [12; 19; 27; 28]. This paper describes the synthesis and structure elucidation of novel metal complexes of 2,4-dithiouracil and its derivatives. Although a crystal growth system was employed for isolating a single crystal from each complex, the attempts were unsuccessful.