**2. Materials and Methods**

By varying the component ratios or the solvent during the grinding experiments, it was possible to access cocrystals of A:2B **3** and A:C **2** as well as the ternary cocrystal 2A:2B:C **1**. Modified parameters include the ratio of the used components; grinding conditions like neat, drop-, or liquid-assisted grinding; and the choice of the solvents tetrahydrofuran vs. *n*-hexane. Only liquid-assisted grinding experiments in the presence of tetrahydrofuran were successful. Modification of the grinding conditions or the usage of *n*-hexane resulted in the observation of physical component mixtures. The experiments were either done as one-pot reactions of three components or by adding a component to sequentially synthesized and characterized binary cocrystals (Scheme 2).

PXRD was performed on each of the received crystalline products. Furthermore, single crystalline entities suitable for X-ray structure analysis of these multicomponent crystals was grown from solution (Table 1).

Preparation of **2**: 1 mmol of A and 2 mmol of B were placed in a mortar. Ten drops of tetrahydrofuran (THF) were added, and the resulting mixture was ground for 5 min. The resulting powder was characterized by PXRD.

Preparation of **3**: 1 mmol of A and C, respectively, were placed in a mortar. Ten drops of THF were added, and the resulting mixture was ground for 5 min. The resulting powder was characterized by PXRD.

Preparation of **1**:


All obtained crystalline materials were characterized by powder X-ray diffraction (PXRD) (Figure 1), measured on a Bruker D2 PHASER diffractometer in flat mode and Bragg–Brentano geometry using filtered CuKα and CuKβ radiation.

**Figure 1.** The diffractograms show the diffraction patterns of the obtained multicomponent crystals **1** (2A:2B:C) green graph, **2** (A:2B) red graph, and **3** (A:C) blue graph.

Single-crystal X-ray diffraction measurements of **2**, **3** were carried out on a Rigaku Synergy diffractometer using monochromated Mo Kα radiation (λ = 0.71073). Single-crystal X-ray diffraction measurement of **1** was carried out on a Rigaku Supernova using monochromated Cu Kα radiation (λ = 1.54184). Structures were solved by direct methods, and all nonhydrogen atoms were refined anisotropically on *F*<sup>2</sup> (program SHELXTL-97, G.M. Sheldrick, University of Göttingen, Göttingen, Germany). Crystallographic crystal data and processing parameters are shown in Table 1. CIF-files giving X-ray data with details of refinement procedures for **1**, **2,** and **3** CCDC Nr. 1981507-1981509 are available free of charge via the Internet at http://pubs.acs.org.

The UNI Force Field Calculations of Mercury crystallography package were used to calculate inter-molecular potentials of the crystal structure **2** with normalized hydrogens (kJ/mol).


**Table 1.** Summary of crystal data, data collection, and refinement parameters for **1**, **2**, and **3**.

**Scheme 2.** Performed synthesis routes for the multicomponent crystal 1 (2A:2B:C).
