*3.4. Thermal Analysis*

DSC was used to evaluate the thermal behaviour and to determine the melting point of the new DIC phases. Figure 5 shows the melting point of DIC, as well as the DSC traces of DIC–ADE, DIC–CYT, and DIC–ICT. Each plot shows a well-defined endothermic event that corresponds with the melting point of the material. A single endothermic transition indicates the absence of solvation or hydration phenomena and also demonstrates the stability of the phase until the melting point. Above the melting point, some endothermic events are also observed, corresponding to the degradation of the samples. The multicomponent materials display a melting point that falls in a region between the melting point of DIC (179 ◦C) and the coformer (ADE: 360 ◦C; CYT: 320–325 ◦C; ICT:248–254 ◦C). This feature has already been described by other researchers [46]. A higher melting point was obtained through multicomponent crystallization, resulting in better thermal stability, probably due to stronger intermolecular interactions between DIC and nucleobases. TGA showed no weight loss until melting, suggesting that the new DIC phases were not hydrated or solvated. The occurrence of mass loss was observed after melting points, which was attributed to the degradation of cocrystals (Figure S5).

**Figure 5.** Differential scanning calorimetry (DSC) traces of DIC and multicomponent compounds DIC–ADE, DIC–CYT, and DIC–ICT.
