Taming Inert B-H Bond with Low Energy Light: A Near-Infrared Light-Induced Approach to Facile Carborane Cluster-Amino Acid Coupling.

The selective functionalization of inert B-H bonds in carborane clusters has been a formidable challenge. Recent advances have witnessed such reactions through photoredox methods utilizing ultraviolet or visible light irradiation. However, high-energy light sources often suffer from poor energy efficiency, a limited substrate scope, undesired side reactions, and low scalability. Here, we present the first successful B-H bond functionalization under low-energy near-infrared (NIR) light using a carborane-based electron donor-acceptor complex. Both photophysical investigations and theoretical modeling reveal a facile single-electron transfer from the carborane cage to the electron-deficient photocatalyst, generating a carborane cage radical under NIR light irradiation. The follow-up radical pathway enables the direct coupling of carboranes with amino acids or oligopeptides, yielding a diverse array of carborane-functionalized amino acids or oligopeptides. Beyond expanding the known chemical space of boron cluster derivatives, we further demonstrate that carborane-based amino acids with imaging and targeting capabilities could serve as promising multifunctional boron carriers for boron neutron capture therapy. Thus, the selective B-H bond functionalization of the carboranes via NIR light not only provides a straightforward and practical strategy in boron cluster synthetic chemistry but also lays the foundation for the development of next-generation boron-containing biomolecules and advanced functional materials.