Cocrystal Engineering Using Structural Modularity: Modulating Solid-State Fluorescence through a Stoichio-Morphic Ternary Cocrystal

Organic cocrystals offer excellent opportunities for the fabrication of functional solids. Generally, cocrystals are formed with two coformers, and the resulting structures are dominated by strong intermolecular interactions and close-packing criteria, leading to a lack of diversity. In this study, structural modularity in a binary solid is utilized to design ternary cocrystals. This novel strategy bypasses the requirement of symmetry inequivalence or strong interaction anisotropy and recovers a synthetic dead end in a crystal engineering venture. Moreover, using the genotype-phenotype concept, functional ternary solids consisting of benzilic acid, 4,4′-bipyridine, and pyrene were synthesized that showed stark differences in photoluminescent properties. Single crystal structural analysis and DFT calculations provide insights into the structure–property relationship in these stoichio-morphs.