Abstract: In this work, the ketocoumarin derivatives have been studied as a sensitizer for iodonium salts by laser flash photolysis method. Results show that the excited triplet state of ketocon-marin derivatives can be quenched by iodonium salts through the mechanism of electron transfer. The methyl viologen (PQ²⁺) was used as a model compound instead of iodonium salt and the same phenomenon of triplet state quenching was also observed. Simultaneously, a new signal placed at 610 nm, which indicates the cationic radical (PQ⁺) formation of methyl viologen, was observed. These results show that the ketocoumarin derivatives are certainly applied as electron donors in the electron transfer reactions. The calculated result by weller equation demonstrates that the electron transfer process may be occured between ketocoumarin derivatives and iodonium salts.

Key words: ketocoumarin, laser flash photolysis, iodonium salt, cationic photoinitiator, electron transfer, photoinitiation polymerization