Transient photochemistry of diflunisal: Photoejection and trapping of hydrated electrons leading to the formation of phenoxy radicals, photostimulated defluorination, and cross combination reaction

The transient photochemistry of diflunisal has been investigated in aqueous solution. The photoreactivity of the compound is quite unusual for fluorin ated derivatives. The loss of fluoride does not occur from an excited state , as expected, but is photostimulated through a reaction involving trapping by the ground state of electrons photoejected from diflunisal. Mono- and b iphotonic pathways are involved in the photoionization process. A phenoxy r adical generated after photoionization has been characterized as the main t ransient species involved in the photodegradation. A cross combination reac tion between phenoxy and aryl radicals is controlled by the persistent radi cal effect and is responsible for the formation of the stable photoproduct.