Photocatalyzed Dehalogenation Using Iron(III) Photosensitizers

Due to its high abundance, low cost and low toxicity, photosensitizers based on iron have long been considered as the holy grail for photochemical applications. Unfortunately, with a few exceptions, these photosensitizers suffer from extremely short, sub-nanosecond, excited-state lifetimes that limit diffusional reactivity. We have determined key parameters that have allowed to circumvent these limitations and achieve efficient excited-state electron transfer with large cage-escape yields using green light irradiation. Dehalogenation reactions operated with large yields and a clear view of the mechanistic pathway with the associated rate constants was obtained by a combination of time-resolved spectroscopic methods, such as femtosecond and nanosecond transient absorption or infrared spectroscopy (TRIR)