Multicomponent Crystals with Competing Intermolecular Interactions: In Situ X‐ray Diffraction and Luminescent Features Reveal Multimolecular Assembly under Mechanochemical Conditions

Supramolecular chemistry under mechanochemical conditions has drawn attention because it can induce low‐solubility molecules to self‐assemble, although most of the reported examples have been limited to two‐component systems. We applied mechanochemical synthesis to achieve multimolecular self‐assembly in more challenging three‐component systems. The produced crystals showed multicolor solid‐state luminescence depending on the components when exposed to UV light. Optical outputs and X‐ray diffraction studies were used to examine the self‐assembling behavior in greater depth. Using synchrotron radiation, in situ X‐ray diffraction permitted direct observation of the milling process, which started the self‐assembly process within 1 min. This research emphasizes the importance of multicomponent molecules with optical functions and self‐assembling behavior and offers the possibility of developing more complicated multicomponent crystals and organic solid solutions for advanced materials. The self‐assembly of multicomponent molecules with three or more components, which is considered difficult, can be solved by using pre‐stored intermolecular interactions. The fast progression of mechanochemical synthesis has been revealed by in situ X‐ray diffraction, whereby the self‐assembly behavior could be expressed as a function of solid‐state luminescence driven by the combination of components.