Near-Infrared Excitation of the peri-Xanthenoxanthene Radical Cation Drives Energy-Demanding Hole Transfer Reactions

Strongly oxidizing photosensitizers (superoxidants) based on organic radical cations are capable of driving energy-demanding reactions using low-energy photons. Here, we show that the peri-xanthenoxanthene radical cation (PXX+•) has an electronic excited state (D1) with a τ = 124 ps lifetime in CH3CN at 295 K. Photoexcitation of PXX+• covalently attached to electron deficient 9,10-bis(trifluoromethyl)anthracene (TMFA) using an 885 nm laser pulse drives oxidation of TFMA with unity quantum yield. Extending the PXX+•-TFMA dyad to a molecular triad having a 9,10-diphenylanthracene terminal hole acceptor, PXX+•-TFMA-DPA, and selectively exciting PXX+• results in formation of PXX-TFMA-DPA+• with a 46% quantum yield and a τ = 11.5 ± 0.6 ns lifetime. This work demonstrates that the PXX+• D1 electronic excited state can serve as a promising superoxidant for challenging oxidation reactions relevant to solar-energy applications.