Near-Infrared Emission in Organic Cocrystals Based on Twisted-Component Pseudoencapsulation

Near-infrared (NIR) fluorescence, prized for deep optical penetration and high spatial resolution, can be achieved in organic cocrystals via donor–acceptor (D–A) charge-transfer (CT) emissions. We have rationally synthesized a series of cocrystals consisting of a twisted tetrachloroperylene dianhydride (TCPDA) as the electron-deficient acceptor, incorporating respectively with three different polycyclic aromatic hydrocarbons─i.e., triphenylene (TP), coronene (Cor), and perylene (Per)─as electron-rich donors. The introduction of a twisted component provides a pseudoencapsulation strategy to achieve fine-tuned control over stoichiometries, solid-state superstructures, and D–A interactions. Fluorescence emission spectra of these three cocrystals cover a wide range of wavelengths up to 861 nm. TP–TCPDA cocrystals with a two-photon absorption band reach into the NIR-II region because of the manipulation of the twisted configuration and noncovalent interactions. The pseudoencapsulation strategy of applying twisted components in cocrystals holds considerable promise for the future design and synthesis of advanced optical materials.