Colour by design: tuning the solid-state emission of coronene bisimide by tailored matrices

A photofunctional coronene bisimide (CBI) has been equipped with two bulky terphenyl imide substituents that control self-assembly, restricting it to the formation of well-defined dimers with a remarkably high association constant of K = 3.0 × 10⁵ M^-1 in methylcyclohexane/1,1,2,2-tetrachloroethane (TCE). Further, the electron-poor CBI acts as a versatile supramolecular host capable of forming charge-transfer (CT) complexes with various electron-rich guest molecules, including perylene, triphenylene, and 3,6-diiodocarbazole with binding affinities up to K = 10³ M^-1 in TCE. As shown in this article, the variety of supramolecular assemblies formed by CBI enables a unified strategy for emission colour tuning over a wide spectral range. In the crystalline solid-state, the photoluminescence can be tuned from green up to the near-infrared region through either monomer-like or dimer-like polymorphs, or guest binding. Further, the external heavy-atom effect of 3,6-diiodocarbazole allows for dual emission of thermally activated delayed fluorescence and phosphorescence, making the cocrystal with diiodocarbazole the first example of a CBI cocrystal with delayed emission. This study presents a general design strategy for emission tuning of CBIs, which is expected to be extendable to a variety of luminescent host systems.