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Bridge-mediated hopping or superexchange electron-transfer processes in bis(triarylamine) systems

Nature Materials volume 1, pages 69–73 (2002)Cite this article

Abstract

Hopping and superexchange are generally considered to be alternative electron-transfer mechanisms in molecular systems. In this work we used mixed-valence radical cations as model systems for the investigation of electron-transfer pathways. We show that substituents attached to a conjugated bridge connecting two triarylamine redox centres have a marked influence on the near-infrared absorption spectra of the corresponding cations. Spectral analysis, followed by evaluation of the electron-transfer parameters using the Generalized Mulliken–Hush theory and simulation of the potential energy surfaces, indicate that hopping and superexchange are not alternatives, but are both present in the radical cation with a dimethoxybenzene bridge. We found that the type of electron-transfer mechanism depends on the bridge-reorganization energy as well as on the bridge-state energy. Because superexchange and hopping follow different distance laws, our findings have implications for the design of new molecular and polymeric electron-transfer materials.

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Figure 1
Figure 2: The ultraviolet/visible/near-infrared spectrum of 4 + measured in CH 2 Cl 2 (solid line).
Figure 3: The three diabatic states that are coupled in equation (1).
Figure 4: Plot of the ground-state PES of : a, 1+ and b, 4+.

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Acknowledgements

This work was supported by the Fonds der Chemischen Industrie and the Deutsche Forschungsgemeinschaft. We thank JASCO GmbH Deutschland for their support.

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  1. Institut für Organische Chemie, Bayerische Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg, D-97074, Germany

    Christoph Lambert, Gilbert Nöll & Jürgen Schelter

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Correspondence to Christoph Lambert.

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Lambert, C., Nöll, G. & Schelter, J. Bridge-mediated hopping or superexchange electron-transfer processes in bis(triarylamine) systems. Nature Mater 1, 69–73 (2002). https://doi.org/10.1038/nmat706

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