Leakage through the membrane was excluded through various reference experiments (Section S8), leading to the conclusion that, indeed, transmembrane electron transfer takes place. Based on the analysis of the thermodynamic properties, the excited state of [1] 2+ is reduced by NADH with a driving force of -0.53 V and a driving force of -0.98 V to oxidize by XTT. These values showed that it is easier to oxidize [1] 2+ than to reduce it (Section S11).