The rich redox chemistry of Bi is brought to bear in recent reports that showcase its ability to engage in both 1e -and 2e -redox manifolds, featuring both analogous and complementary reactivity to that exhibited by transition-metal species. Recently, our group reported that (N,C,N)-bismuthinidenes undergo oxidative addition into aryl iodides and aryl thianthrenium species under red-light irradiation, thus mimicking one of the fundamental organometallic steps in metal-catalyzed reactions (Figure ). Notably, the photoactive bismuthinidene harnesses low-energy red light (660 nm, 43.3 kcal mol -1 ) to enable the activation of aryl iodides with exquisite selectivity over other carbon-(pseudo)halogen bonds. Unlike most photoredox catalysts employed in the literature, the Bi species is not only the photoactive species but is also responsible for orchestrating the activation and downstream coupling of aryl iodides through elementary steps at the Bi center, thus merging aspects of photoredox and transition-metal catalysis in a single maingroup species. 47 Prompted by the unique reactivity of 1a under red-light irradiation and buoyed by the unique photophysical behavior of other heavy atom complexes, we sought to characterize the nature of the excited-state species responsible for the observed reactivity and delineate the mechanism of the downstream oxidative addition into aryl iodides. In this study we report that the red-light absorption of bismuthinidene 1a is attributed to an intense S0 → S1 MLCT transition (ε = 3620 M -1 cm -1 @ 630 nm), which rapidly undergoes ISC to a highly reducing triplet state (-2.62 V vs Fc +/0 in MeCN) (Figure ). However, unlike most transition-metal chromophores, the bismuthinidene features a remarkably small S1-T1 gap, leading to minimal dissipative losses during ISC. The subsequent oxidative addition into aryl iodides is interrogated using kinetic studies as well as intra-and intermolecular competition experiments. When considered holistically, the data suggest that the key MLCT state engages with aryl iodides via an outer-sphere SET-based mechanism, thus discarding concerted SNAr-type, inner-sphere SET, or halogen-atom transfer (XAT) pathways.