Unlocking red-to-near-infrared luminescence via ion-pair assembly in carbodicarbene borenium ions

Achieving efficient red and near-infrared (NIR) emission in boron cation-based emitters remains challenging owing to their intrinsic instability, strong electrophilicity of the boron centre and pronounced non-radiative decay governed by the energy gap law. Here we report a family of air- and moisture-stable carbodicarbene (CDC)-borabenzo[c]anthanthrenium ions exhibiting solid-state red-to-NIR luminescence (maximum emission wavelength up to 730 nm) with competitive quantum yields. Crystallographic, photophysical and computational analyses reveal that the CDC ligand plays a dual role by electronically stabilizing the boron centre and directing ion-pair assembly via charge localization, thereby modulating exciton coupling and aggregate-state emission. These cationic π-extended boron frameworks represent rare examples of monoboron-doped luminophores displaying deep-red-to-NIR emission. Our findings highlight that the combination of π-extension, a charge-directing CDC ligand and ion-pair assembly constitutes an effective strategy to access efficient red/NIR emitters, providing guiding principles for the design of functional long-wavelength emitting main-group materials.