Organic Donor-Acceptor Thermally Activated Delayed Fluorescence Photocatalysts in the Photoinduced Dehalogenation of Aryl Halides

We report a family of donor-acceptor thermally activated delayed fluorescent (TADF) compounds based on derivatives of DMAC-TRZ, that are strongly photoreducing. Both Eox and thus E*ox could be tuned via substitution of the DMAC donor with a Hammett series of p-substituted phenyl moieties while Ered remained effectively constant. These compounds were assessed in the photoinduced dehalogenation of aryl halides, and analogues bearing electron withdrawing groups were found to produce the highest yields. Substrates of up to Ered=-2.72 V could be dehalogenated at low PC loading (1 mol %) and under air, conditions much milder than previously reported for this reaction. Spectroscopic and chemical studies demonstrate that all PCs, including literature reference PCs, photodegrade, and that it is these photodegradation products that are responsible for the reactivity. A family of donor-acceptor thermally activated delayed fluorescence compounds based on DMAC-TRZ and containing aryl subtituents on the DMAC donor have been applied as photocatalysts in the dehalogenation of aryl halides having Ered up to -2.72 V vs SCE. Mechanistic studies indicate that these DMAC-TRZ based compounds act as pre-photocatalysts and photodegrade under the reaction conditions, with the photodecomposition product responsible for the photocatalysis. image