The challenges facing further development of photocatalysis, including reaction setup, reaction scale-up, optoelectronic characterisation of the photocatalyst (PC), mechanistic investigation and caveats concerning reaction yields, have been recently discussed. In the context of replicating a literature photocatalytic reaction and understanding the resultant yields obtained, the reaction setup and mechanistic evidence for said reaction become points of critical importance. Differences in yield when repeating literature photoreactions are to be expected since factors such as temperature, light source, and stirring rate can influence the reaction outcome. Moreover, limited evidence is often provided to corroborate the putative mechanism, leaving doubt as to whether the reaction proceeds via the proposed photocatalytic cycle or whether other pathways may be plausible, as already discussed in recent reports. The importance of these factors came into stark relief during our assessment of the reactivity of the PC, 9,9′-(sulfonylbis(pyrimidine-5,2-diyl))bis (3,6-di-tert-butyl-9H-carbazole), pDTCz-DPmS (Figure ). We previously demonstrated that pDTCz-DPmS was a capable PC across a range of reactions covering disparate photocatalytic mechanisms: oxidative quenching, reductive quenching, energy transfer photocatalysis and dual metallaphotoredox catalysis with a Ni(II) co-catalyst, generally replicating or outcompeting the literature PC in terms of yield under similar reaction conditions. One of the reactions that was probed was the C(sp)-C(sp 3 ) cross-coupling of bromoalkynes with N-(acyloxy)phthalimides (Figure ). First reported by Yang et al. using [Ru(bpy)3](PF6)2 as the PC (Figure ), the authors found that the activation of bromoalkynes was challenging, instead focusing on sulfonyl alkynes (28 vs 76% for coupling of N-(acyloxy)phthalimides with bromoalkynes and sulfonyl alkynes, respectively). The reaction was conducted over 30 minutes in dichloromethane under 4 W 468 nm (blue) LED irradiation, placed 10 cm from the reaction vial. The putative mechanism (see Scheme 1) implicated that either diisopropylethylamine (DIPEA) or the Hantzsch ester (HE) would reductively quench the PC given that such sacrificial reductants are so easy to oxidize[(E(DIPEA •+ /DIPEA) = 0.81 V vs SCE and E(HE •+ /HE) = 1.00 V vs SCE ]. This was supported by Stern-Volmer quenching, which identified both could quench the excited PC. The absence of either DIPEA or HE resulted in a decrease in the yield for sulfonyl alkynes, from 76 to 37% (for no DIPEA) and 28% (for no HE), with no product forming when both DIPEA and HE were removed. As such, it was concluded that both sacrificial reductants were necessary for the reaction. Closure of the photocatalytic cycle was proposed to occur through single electron transfer (SET) from the reduced PC to the N- (acyloxy)phthalimide, which typically have reduction potentials ranging from Ered = -1.26 V to -1.37 V vs SCE. Scheme 1. Putative reaction mechanism for the C(sp)-C(sp 3 ) cross-coupling reaction, first proposed in Ref .