Next, we theoretically assessed the electronic consequences of an electron-transfer from PS to POM-PtCl, which is a key redox step of the HER catalytic cycle. To this end, single-point calculations were performed on the oneelectron reduced POM-PtCl as well as the one-electron reduced reference systems (i.e., [Pt(bpy)Cl2] and POM-ref). This allowed us to compare the Hirshfeld net charges of the one-electron reduced systems with the charge-distribution of the non-reduced systems. Note that this procedure is analogous to determining condensed Fukui functions. While Fukui functions are often used as descriptors for the chemical reactivity of a molecule (with respect to its electrophilic and nucleophilic regions), here, the function for a nucleophilic attack will serve as a measure for the uptake and distribution of additional electron density in the systems studied. The Fukui function 𝑓 + is given by the difference between the electron densities of the initial state 𝜌(𝑁) and the state featuring one additional electron 𝜌(𝑁 + 1):