Singlet Oxygen Generation from Polyaminoglycerol by Spin-Flip-Based Electron Transfer

[Image: see text] Reactive oxygen species have drawn attention owing to their strong oxidation ability. In particular, the singlet oxygen ((1)O(2)) produced by energy transfer is the predominant species for controlling oxidation reactions efficiently. However, conventional (1)O(2) generators, which rely on enhanced energy transfer, frequently suffer from poor solubility, low stability, and low biocompatibility. Herein, we introduce a hyperbranched aliphatic polyaminoglycerol (hPAG) as a (1)O(2) generator, which relies on spin-flip-based electron transfer. The coexistence of a lone pair electron on the nitrogen atom and a hydrogen-bonding donor (the protonated form of nitrogen and hydroxyl group) affords proximity between hPAG and O(2). Subsequent direct electron transfer after photo-irradiation induces hPAG(•+)-O(2)(•–) formation, and the following spin-flip process generates (1)O(2). The spin-flip-based electron transfer pathway is analyzed by a series of photophysical, electrochemical, and computational studies. The (1)O(2) generator, hPAG, is successfully employed in photodynamic therapy and as an antimicrobial reagent.