Over Visible-light photocatalysis has become a widely used technique in synthetic organic chemistry. Photocatalysis functions by harnessing the electronic excited state of a photocatalyst (PC*), generated via the absorption of a photon, to interact with an organic substrate through either electron or energy transfer. Photocatalytic photoinduced single electron transfer (PET), commonly known as photoredox catalysis, proceeds either via a reductive or an oxidative quenching mechanism, dependent on whether the PC* gains or loses an electron, respectively, during the initial PET. Alternatively, photoinduced energy transfer (PEnT) implicates the transfer of energy from the PC* to the substrate through either a Dexter or Förster energy transfer mechanism, regenerating the ground state photocatalyst (PC). Organometallic complexes based on Ru(II) and Ir(III) are the most widely used PCs (Figure ). They possess an attractive suite of properties including suitably long-lived stable excited states, absorption that extends into the visible region where most organic substrates are transparent, plus (especially for Ir(III) complexes), the capacity to modulate both the ground and excited state redox properties through ligand variation. However, the scarcity, toxicity and cost of the noble metals employed has spurred intense efforts to find alternative PCs. There are now many established examples of Earth-abundant metal complexes and metal-free organic photocatalysts, and numerous examples where these perform comparably to the noble metal PCs. While organic photocatalysts, such as xanthene dyes, phenothiazines, and acridinium-based compounds are commonplace (Figure ), their ground and excited state redox potentials are difficult to tune. Donor-acceptor (D-A) thermally activated delayed fluorescent (TADF) PCs, most widely exemplified by the compound 4CzIPN, have rapidly been adopted in the field as their properties are readily tunable through substituent variation (Figure ). 9,10 4CzIPN, initially developed as an emitter for organic light-emitting diodes a decade ago, luminesces via a TADF mechanism. As a result, 4CzIPN possesses microsecond-long emission lifetimes that, coupled with similar redox properties to that of the widely used [Ir(dF(CF3)ppy)2(dtbbpy)]PF6, endows it with similar photochemical reactivity. 4CzIPN was first used as a photocatalyst by Luo and Zhang to achieve a dual catalysed (C)sp 3 -(C)sp 2 cross-coupling reaction. 12 Subsequent work by Speckmeier et al. demonstrated the versatility of this class of D-A TADF photocatalyst and the tunability of their redox potentials by varying the nature and number of electron-donating and electron-accepting groups. A growing number of structurally related D-A PCs have since been reported. TADF operates when the energy gap between the lowest energy singlet and triplet excited states, ΔEST, is sufficiently small such that there is an endothermic upconversion of triplet excitons into singlets by reverse intersystem crossing (RISC). This is possible when the exchange integral between the frontier orbitals involved in the emissive excited state is sufficiently small, which occurs in D-A compounds where the donor and acceptor groups are poorly conjugated such as when they adopt a highly twisted conformation, Ground state redox potentials of DiKTa and Mes3DiKTa in MeCN. Excited state redox properties of DiKTa and Mes3DiKTa calculated from the experimentally determined Eox/Ered and E0,0 values in MeCN, using Eox(PC •+ /PC*) = Eox -E0,0 and Ered(PC*/PC •-) = Ered + E0,0. 16 as is the case for 4CzIPN and its derivatives. An alternative molecular design strategy to reduce the exchange integral is based on the exploitation of opposing resonance effects of p-and n-dopants in nanographenes that is embodied in multi-resonance TADF (MR-TADF) emitters. Herein we present the use of two MR-TADF compounds as photocatalysts for the first time, using DiKTa and Mes3DiKTa, previously reported by us as emitters in OLEDs, as typical examples (Figure ).