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Properties and applications of photoexcited chromophore–radical systems

Nature Reviews Chemistry volume 7, pages 75–90 (2023)Cite this article

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Abstract

Photoexcited organic chromophore–radical systems hold great promise for a range of technological applications in molecular spintronics, including quantum information technology and artificial photosynthesis. However, further development of such systems will depend on the ability to control the magnetic properties of these materials, which requires a profound understanding of the underlying excited-state dynamics. In this Review, we discuss photogenerated triplet–doublet systems and their potential to be used for applications in molecular spintronics. We outline the theoretical description of the spin system in the different coupling regimes and the invoked excited-state mechanisms governing the generation and transfer of spin polarization. The main characterization techniques used to evaluate the optical and magnetic properties of chromophore–radical systems are discussed. We conclude by giving an overview of previously investigated covalently linked triplet–radical systems, and highlight the need for further systematic investigations to improve our understanding of the magnetic interactions in such systems.

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Fig. 1: Photogenerated triplet–radical systems and their applications.
Fig. 2: Schematic illustration of the formation of trip-quartet and trip-doublet states from a radical and triplet state precursor by enhanced intersystem crossing.
Fig. 3: Illustration of the different coupling regimes.
Fig. 4: Illustration of possible excited-state processes in chromophore–radical compounds.
Fig. 5: Optical characterization of chromophore–radical systems.
Fig. 6: Identification and characterization of different spin states by transient continuous wave electron paramagnetic resonance.
Fig. 7: Pulse electron paramagnetic resonance characterization of photogenerated triplet–radical systems.
Fig. 8: Overview of investigated triplet–radical systems grouped according to different chromophore classes.

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Acknowledgements

This work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), project number 417643975.

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  1. Institute of Physical Chemistry, University of Freiburg, Freiburg, Germany

    Theresia Quintes, Maximilian Mayländer & Sabine Richert

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Quintes, T., Mayländer, M. & Richert, S. Properties and applications of photoexcited chromophore–radical systems. Nat Rev Chem 7, 75–90 (2023). https://doi.org/10.1038/s41570-022-00453-y

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