*3.1. Coformer Selection*

Before the experimental trials were conducted, a virtual cocrystal screening was performed to improve the success ratio. A survey on the Cambridge Structural Database (CSD version 5.43, update from June 2022) based on DIC resulted in 70 hits. After excluding the three reported polymorphs [28,30,31] and metal complexes [32–41], the dataset contained 28 hits corresponding to multicomponent forms (salts, cocrystals, hydrates, and solvates). Only in one hit, the dimer DIC–DIC, observed in the monoclinic DIC polymorphs [28,30], was maintained; meanwhile, the remaining hits exhibited common structural features for DIC salts, COO−···amine and COO−··· ammonium synthons, or cocrystals: COOH···N(pyridine) and COOH···N(imidazole) synthons. According to the above-mentioned, our main prerequisite for the coformer selection was having the abovereferred N-groups and being a safe molecule. From our library of coformers, two groups of molecules fulfil these criteria: amino acids and nucleobases. COSMOQuick software was used to validate our selection. Table 2 shows calculations from a list of candidates to form multicomponent crystals with DIC. The list includes our reported coformers and other coformer molecule involved in the formation of cocrystals/salts reported in the survey. Compounds with negative Hex values show an increased probability of forming cocrystals.


**Table 2.** Ranking of potential DIC coformers used in this work, based on COSMOQuick calculations.
