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

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.

Automated summary

Here, we report the first examples of air-stable, deep-lowest unoccupied molecular orbital (LUMO) polycyclic aromatic molecules with emission in the near-infrared (NIR) region, achieved through nitration. Despite the non-emissive nature of nitroaromatics, the choice of a relatively electron-rich terrylene core allowed for fluorescence in these molecules. The degree of nitration directly influenced the stability of the LUMOs. The tetra-nitrated terrylene diimide exhibited the lowest LUMO (<=-4.5 eV) of -5.0 eV vs. Fc/Fc(+), making it the lowest among larger RDIs. These are also the only examples of emissive nitro-RDIs, with larger quantum yields.