Periodic Reporting for period 1 - SOLBATT (Storage of Electrons into Chemical Bonds: Towards Molecular Solar Electrical Batteries)
Reporting period: 2022-07-01 to 2024-12-31
In the first period of ERC StG project SOLBATT, we were working on all three objectives of the project. The most significant progress was finding optimal partners for bidirectional photoinduced electron transfer among tens of different redox switches and hundreds of different electron donors and acceptors. In addition, we were successful in advancing photoinduced charging and discharging. Additional experiments and development are needed mainly in the development of solar cells, solar batteries, and redox switching in solid state.
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.
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.
The most significant achievement of our team is the ability to precisely control photoinduced electron transfer in a certain direction between two molecules by light of a certain wavelength. This goes beyond the state of the art and opens new possibilities for advanced manipulation with electrons by light. Excited state and ground state potentials are therefore not the only condition needed for the design of efficient electron relay system, but incorporation of redox active systems with hysteresis may completely change the rules of the game. Many features of our system were unexpected, especially the complex photochemistry of some tested species has complicated the development process, but the general idea of the system seems to be working as initially proposed.