Speaker: Clara Zens, Friedrich Schiller University Jena

Nowadays organic batteries are promising approaches in energy storage, e.g. due to their mechanical flexibility and sustainability.[1] Conjugated polymers were widely investigated in the scope of such batteries.[2] However, an unstable cell voltage over a broad capacity range prevents their application.[3] Alternatively, stable organic radicals show highly promising properties,[4] yet lacking the desired conductivity. Recently, in a joint-theoretical project, a new approach was realised by combining stable organic radicals with a conductive polymer-based backbone.[5,6] Thereby, the focus was set on the tetramethylpiperidinyl-N-oxyl radical (TEMPO) in combination with a polythiophene backbone.

Particular emphasis was set on the molecular and quantum mechanical modelling of intra- and intermolecular charge transfer (CT) processes of these materials.[5–7] First insights were gained by modelling the potential energy curves (PEC) of the intramolecular CT with multi-configurational methods. The CT was then assessed by Marcus theory. Key properties were explored and how they affect the PECs and thereby the CT.[5] Recent research endeavours focus on the influence of the surrounding environment on the inter- and intramolecular CT. Thereby, the environmental configurations are assessed via molecular mechanics, while quantum mechanical “snapshots” are taken with time-dependent density functional theory. Finally, PECs of intramolecular CT processes of other combinations of thiophene with organic radicals are explored. With these methods, in-depth insights are gained, that allow to tailor new organic radical batteries with optimal CT properties.

[1] C. Friebe, U. S. Schubert, Top. Curr. Chem. 2017, 375, 19.
[2] K. Nakahara et al., Chem. Phys. Lett. 2002, 359, 351–354.
[3] P. Novák et al., Chem. Rev. 1997, 97, 207–282.
[4] K. Hatakeyama-Sato et al., Adv. Mater. (Weinheim, Ger.) 2018, 30, e1800900.
[5] C. Zens et al., ChemSusChem 2023, 16, e202201679.
[6] C. Friebe et al., J. Phys. Chem. C 2023, 127, 1333–1344.
[7] S. Mitra et al., J. Chem. Phys. 2024, 161.