To assess the supramolecular interactions between photosensitizer and catalyst, we examined the emission quenching of PS by the electron acceptor POM-PtI or the sacrificial electron donor TEA (Figure ): The steadystate emission spectra and emission lifetimes of PS (λexcitation = 420 nm) were measured upon addition of TEA or POM-PtI to a DMF of PS solutions (see Figure ,c and SI, Figure ). The corresponding Stern-Volmer plots (Figure and) are analyzed by linear fitting resulting in quenching rate constants (kq) of 7.1×10 7 M -1 s -1 (reductive quenching, TEA) and 8.4×10 10 M -1 s -1 (oxidative quenching, POM-PtI). The calculated mutual diffusion rate constants (kD) in DMF are 7.7×10 9 M -1 s -1 (for PS/TEA) and 8.2×10 9 M -1 s -1 (for PS/POM-PtI), respectively (see SI, Section 7). Comparison between kD and kq however shows that for reductive quenching (PS*/TEA) kD is ~100 times higher than kq, indicating a quenching efficiency per encounter of ca. 1%. In contrast, for the oxidative quenching (PS*/POM-PtI) kD is ~10 times smaller than kq, indicating a quenching efficiency per encounter of formally >100%. Two interpretations are in line with these observations: (a) the interactions of the PS cation and the POM-PtI anion increase the rate of interaction beyond the frequency calcu-lated for neutral reaction partners within the Collins-Kimball model (see SI, Section 7); 51 (b) a supramolecular preassembly of cationic PS and anionic POM-PtI enables PS* quenching at significantly faster rates than the mutual diffusion, i.e., in the limit of static quenching. As a result, the oxidative quenching of PS* has to occur via both, static and dynamic quenching.