HEs are a common and versatile additive in the photocatalysis literature. Predominately, HEs are used as an electron donor and/or proton source in photoredox catalysis. If, however, they have an alkyl group in the 4 position, they can also be useful as radical precursors, and through an oxidative fragmentation mechanism, have been employed as alkylating agents, generated through both photocatalysis and direct irradiation. 32 There are also examples of HEs being used as stoichiometric photoreductants but as far as we are aware, there are no reports of HEs being used as photoreductants in combination with an external PC. Therefore, the mechanism proposed in this C(sp)-C(sp 3 ) reaction is distinct to those reported in the literature in that product forms as a result of photoexcitation of both pDTCz-DPmS and HE, independently, with the greatest product yields obtained when both species are present.