Aromaticity-Engineered Open-Shell Radical Anions for Air-Stable Doublet Emission in N-Annulated Perylene Diimide.

We report the doublet emissive open-shell radical anions, where the N-annulated perylene diimide (PDIN-H) is functionalized with aromatic rings. This resulting [PDI-MeR]•- (R = BZ, benzene; NP, naphthalene; PY, pyrene) shows a high quantum yield, a long lifetime, and a high stability in air, as the ring size increases. The key to these properties is the combination of PDIN's aromaticity with predominant through-space charge-transfer (TSCT). This finding provides fundamental insights into unique open-shell electronic structures and tunable optical functions, thereby paving the way for the development of novel doublet emitters and electroactive materials.