Comparison between NIR and UV-Sensitized Radical and Cationic Reactivity of Iodonium Salts Comprising Anions with Different Coordination Behavior

摘要

Substituted diaryliodonium salts bearing weak coordinating anions ([(CF3SO2)(3)C](-); [(CF3SO2)(2)N](-); [PF6](-); [PF3(C2F5)(3)](-); [PF3(n-C4F9)(3)](-)) were tested regarding their efficiency as radical initiator to initiate radical polymerization according to a sensitized mechanism. A NIR LED emitting at 790 nm was applied to initiate sensitized polymerization applying the polymethine S2265 as sensitizer. Change of the sensitizer resulting in spectral overlap with emission of UV-LED emitting at 395 nm complimented the experiments to understand the behavior of these iodonium salts under different exposure conditions. Furthermore, formation of protons was quantitatively probed by Rhodamine B lactone showing that UV sensitization resulted in a significant higher yield compared to NIR-sensitized photopolymerization. Surprisingly, the iodonium salt bearing the [(CF3SO2)(3)C](-)-anion exhibited a good performance in both radical photopolymerization and photoinduced formation of protons. Thioxanthon (ITX) served as sensitizer for all UV-LED experiments.