Considering the effectiveness of multicomponent systems, in which photoexcitation triggers a cascade of short range electron transfers, we report on two sets of novel multicomponent DA1A2s – Figure 2. These DA1A2 types feature electron transport chains with C60 and C70 of different electron acceptor strengths to create an electrochemical gradient. As a complement to electron accepting C60 / C70 either zinc porphyrins (ZnP) and zinc phthalocyanines (ZnPc) were employed. The motivation for our pump-probe investigations was to establish the role of ZnPc or ZnP as light harvester and electron donor to power unidirectional (reductive) charge shift reactions along a variety of electron transport chains.
In summary, we will demonstrate the control over unidirectional charge shift along electron transport chains en route towards highly energetic, long-lived charge separated states. Key is, however, a charge shift mediating state, whose relative energy determines the overall efficiency. If the energy of the mediating state, on one hand, is higher than the charge separated state, resonance conditions enable efficiencies as high as 50%. If the energy, on the other hand, is lower than the charge separated state, deactivation to the ground state limits the efficiency to 10%.