In order to assess the photostability of the PCs when applied to reactions not involving sacrificial amine donors, we selected two other photoredox reactions: an atom transfer radical addition (ATRA) reaction of tosyl chloride with styrene (Figure ) and the Giese type addition of N-Cbz-Pro to diethyl maleate (Figure ). The 1 H NMR yields obtained in these reactions for the PCs in MeCN are provided in Tables and. For both reactions, literature yields could be replicated in our set-up; in the ATRA reaction [Ru(bpy)3](PF6)2 achieved 75% yield of the target product, which is comparable to the literature yield of 80%. Similarly, in the Giese type addition reaction, 4CzIPN yielded 77% of the functionalized product using our set-up, comparable to the 80% literature yield. The UV-Vis absorption profiles before and after irradiation for all PCs employed in both reactions are given in Figures . In general, PCs that did not promote the formation of the target product or did so only in very low yields largely retained their UV-Vis absorption profile. For example, 4CzIPN yielded only 3% of the target product in the ATRA reaction and the UV-Vis absorption spectrum is essentially unchanged after the reaction compared to that prior to irradiation (Figure ). In contrast, when PCs can photocatalyze the reaction, the UV-Vis absorption profile is significantly altered. This is exemplified for [Ru(bpy)3](PF6)2, which produces 75% of the product in the ATRA reaction and after irradiation, the characteristic MLCT absorption band at 450 nm is blue-shifted to 400 nm (Figure ).