Aminoboranes as Rationally Tuned Organic Photosensitizers for Energy Transfer Catalysis

We report a new class of rationally designed organic photosensitizers based on boron–nitrogen-substituted scaffolds, capable of mediating challenging triplet energy transfer (EnT) reactions under visible-light irradiation. Guided by DFT and TD-DFT calculations, we modulated the twisted intramolecular charge transfer(TICT) character of the excited state through strategic substitution on the carbazole–borane framework, allowing fine-tuning of both absorption and triplet energy levels (ET = 63–70 kcal mol−1 ). The most effective catalyst outperformed traditional Ir- and xanthone-based sensitizers across benchmark EnT reactions, including E/Z isomerizations, [2 + 2] photocycloadditions, and[1,3]-sigmatropic rearrangement. This B–N system enables the sensitization of coumarin-related substrates with ET ≥ 65 kcal mol−1 , which was previously inaccessible to fully organic EnT photocatalysts. These results establish a new design principle for modular, high-energy triplet sensitizers based on organic aminoborane scaffolds.