In the ERC StG project, we initially focused on studies of redox switches and their interaction with suitable amine-based electron donors. We successfully found suitable partners for efficient photoinduced reduction, forming oxidized stable charge separated states. We managed to completely hinder background processes, even though significant unexpected issues occurred due to (i) high electrophilicity of the redox switches, (ii) non-equilibrium thermal discharging of the irradiated mixture back to the initial state, (iii) limited solubility and solvent choice for photoinduced electron transfer (interference with hydrogen atom abstraction and other redox processes). Nevertheless, by fine-tuning their chemical and redox properties, we found several partners being able to efficiently quantitatively reduce the redox switch to its charged state.
In the second objective, we achieved efficient discharging of the redox switches on electrodes in electrolytic setup with applied bias voltage. The oxidation of the first electron is much more demanding than that of the second one and therefore, the initiation of the oxidation needs to be performed upon external trigger. Besides electrochemical activation, the most successful method for discharging neutral reduced redox switches is photochemical activation with single electron accepting oxidants. While most classical photoredox catalysts are chemically and photochemically not compatible with the system (or suffer significant bleaching and cannot be used efficiently), we found that electron deficient photocatalysts are suitable for photoinduced discharging of neutral reduced redox switches.
Within the third objective, we have synthesized various dyads containing redox switch and donor molecules in different molar ratios. We have investigated the mechanism of photoinduced electron transfer by ultrafast transient spectroscopy. We focused mainly on the stoichiometry and efficiency of the electron transfer.
