The deeper it goes, the brighter it glows: NIR emissive nitro-terrylene diimides with deep LUMOs

Chem Sci. 2023 Jan 30;14(12):3147-3153. doi: 10.1039/d2sc06162g. eCollection 2023 Mar 22.

Abstract

Herein, we present the first examples of air-stable, deep-lowest unoccupied molecular orbital (LUMO) polycyclic aromatic molecules with emission in the near-infrared (NIR) region, using nitration as a strategy. Despite the fact that nitroaromatics are non-emissive, the choice of a comparatively electron-rich terrylene core proved to be beneficial for achieving fluorescence in these molecules. The extent of nitration proportionately stabilized the LUMOs. Tetra-nitrated terrylene diimide exhibited a deep-LUMO (≤-4.5 eV) of -5.0 eV vs. Fc/Fc+, the lowest for any larger RDIs. These are also the only examples of emissive nitro-RDIs, with larger quantum yields.