Reimagining <i>o</i> ‐Carborane‐Based Fluorophores: Charge‐Transfer from Boron Substituents Triggers Aggregation‐ and Crystallization‐Induced Emission

Abstract o ‐Carborane‐based fluorophores are widely recognized for their aggregation‐induced and crystallization‐induced emission (AIE and CIE) properties, making them valuable building blocks for materials used in fluorescence applications such as bioimaging or optoelectronics. Until now, observing AIE/CIE required the fluorophore to be attached via the carbon atom of the carborane, inherently limiting further functionalization possibilities. Herein, we report for the first time that boron‐substituted carboranes (substituent is at position 9) exhibit AIE/CIE activity, which originates from photoexcitation‐induced electron‐transfer from the substituents linked to the carborane cage via its boron vertices. Furthermore, the solid state emission can be tailored by the proper selection of the substituents. This finding not only significantly broadens the scope of AIE‐active compounds but also offers new design strategies for the development of luminescent carborane‐based materials.