For the ET steps an error of roughly 0.1 V is obtained with CCSD(T) while the error bars for pK a values are also of the same order of magnitude. Note that by comparing the energy of the orbitals of the spin-up and spin-down channels, as shown in Figure (a) and (b), it can be seen that the HOMO spin-up channel has a higher energy level than the spin-down channel for the reactants participated in the ET and PET reactions through the oxidation reactions. Therefore, when we discuss HOMO, we are referring to the spin-up channel orbitals. Through SHAP, we carried out feature importance analysis that determines the attribution of feature variables of each sample on the model prediction. HOMO state is the most important feature in model training to predict E red. and E 0 , as shown in Figure . The absence of this feature in some samples can deteriorate E red. prediction beyond ±1.5 V. This value for E 0 is around ±1 V. For the pK a prediction, those orbitals positioned at the edge of the HOMO-LUMO gap are the most important.