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 E_ox and thus E*_ox could be tuned via substitution of the DMAC donor with a Hammett series of p-substituted phenyl moieties while E_red 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 E_red = -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.