Having established that Ir(pmi)3 is a competent energy transfer photocatalyst, we next explored its capacity to engage in photoredox catalysis. We investigated the dehalogenation of aryl halides as a model reaction. This transformation can proceed via an oxidative quenching pathway in the presence of an amine, which acts as a sacrificial reductant to close the photocatalytic cycle. Alternatively, the PC* can initially undergo reductive quenching by the amine, after which the PC -• reduces the aryl halide substrate to turn over the cycle. Reduction of the aryl halide substrate becomes progressively more difficult with increasing electronegativity of the halide group (|Ered| = -I < -Br < -Cl) and in the presence of electron-donating substituents (|Ered| = EWG < EDG). Much progress has been made in photocatalytic dehalogenation of aryl and alkyl halides by transition metal photocatalysts since the first report by Stephenson and co-workers. Jui and co-workers examples of other transition metal or organic PCs. Following the protocol of Connell and co-workers, we investigated first the dechlorination of methyl 4-chlorobenzoate (Ered = -1.98 V vs. SCE), employing 1 mol% mer-Ir(pmi)3 as the PC and 10 equivalents of triethylamine (TEA). Under these conditions methyl benzoate was produced in 39% yield ble ). The product yield was significantly improved to 79% with a change in the amine to N,N-diisopropylethylamine (DIPEA) (Figure ). This is likely due to its less positive ground-state oxidation potential (Eox = 0.68 V vs. SCE) compared to that of TEA (Eox = 0.96 V vs. SCE), producing a greater thermodynamic driving force for the reduction of the PC +• to re-form the PC. Decreasing the amount of DIPEA to one equivalent resulted in a decrease in the yield to 59% (Table ). With the optimized conditions in hand, using 10 equivalents of DIPEA, with fac-Ir(pmi)3 a slightly lower yield of 70% was obtained (Figure ). This decrease in yield is attributed to the slightly less negative E*ox of this isomer (E*ox = -2.67 V vs SCE) compared to mer-Ir(pmi)3 (E*ox = -2.71 V vs SCE). Pleasingly, both isomers outperformed fac-Ir(ppy)3, which produced only 65% of the dehalogenated product (Figure ). Under these conditions, yields of ≤ 5% were obtained when either the PC, the sacrificial amine, or the light were absent (Table , entries 2-4, respectively). When the reaction was conducted under air with mer-Ir(pmi)3, the yield decreased to 55% (Table ), indicating that oxygen is a competitive though somewhat inefficient quencher of the triplet excited state of this PC. Stern-Volmer quenching studies revealed that for fac-Ir(pmi)3, the mechanism proceeds through oxidative quenching by the aryl halide (Figures S24), while there was no quenching of the excited state with DIPEA for fac-Ir(pmi)3