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PreprintCC BYChemRxiv

Symmetric versus asymmetric electron transfer in symmetric molecules

  • Aswin Jyothilakshmi Ravi1,2,3,4
  • Ilya N. Ioffe5,6
  • Samuel Palato5,7
  • Christoph Merschjann1,2
  • Lucia Anghileri8
  • Florian Ortis8
  • Bartholomäus Pieber8
  • Renske M. van der Veen1,2,3,4,5,9
  • Julia Stähler5,7,10,11
  • Sergey A. Kovalenko5,7
11 affiliations
  1. 1Department of Atomic-Scale Dynamics in Light Energy Conversion
  2. 2Helmholtz-Zentrum Berlin für Materialien und Energie
  3. 3Nanoanalytics Division
  4. 4Technische Universität Berlin
  5. 5Department of Chemistry
  6. 6Lomonosov Moscow State University
  7. 7Humboldt-Universität zu Berlin
  8. 8Institute of Science and Technology Austria (ISTA
  9. 9University of Illinois at Urbana−Champaign
  10. 10Department of Physical Chemistry
  11. 11Fritz-Haber-Institute der Max-Plank-Gesellschaft
Open at sourceDOICite

Abstract

Photoinduced electron transfer (ET) in symmetric donor-acceptor-donor (D-A-D) or acceptor-donor-acceptor (A-D-A) molecules attracts attention due to applications in advanced materials. It is normally assumed that ET occurs asymmetrically, from one donor to acceptor, thus breaking molecular symmetry and resulting in a dipole moment in the excited state. However, the symmetry can be preserved with symmetric ET from both donors, leading to a nondipolar state with a high quadrupole moment. Here we report on symmetric ET in a D-A-D probe, 5,5'-di(9H-carbazol-9-yl)-2,2'-bipyridine. This probe is weakly solvatochromic in absorption, but highly solvatochromic in emission, revealing a nonlinear spectral shift and strong decay of the oscillator strength in solvents of increasing polarity. We develope a 3-excited-state model that fits the data quite well for symmetric ET, while no reasonable fit is possible for asymmetric ET. The model predicts the symmetric ET to be barrierless and ultrafast, in good agreement with observations.

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Cite

BibTeXRIS
BibTeX
@misc{ravi2026symmetric,
  title = {{Symmetric versus asymmetric electron transfer in symmetric molecules}},
  author = {Aswin Jyothilakshmi Ravi and Ilya N. Ioffe and Samuel Palato and Christoph Merschjann and Lucia Anghileri and Florian Ortis and Bartholomäus Pieber and Renske M. van der Veen and Julia Stähler and Sergey A. Kovalenko},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15002784/v4},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15002784/v4},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Symmetric versus asymmetric electron transfer in symmetric molecules
AU  - Aswin Jyothilakshmi Ravi
AU  - Ilya N. Ioffe
AU  - Samuel Palato
AU  - Christoph Merschjann
AU  - Lucia Anghileri
AU  - Florian Ortis
AU  - Bartholomäus Pieber
AU  - Renske M. van der Veen
AU  - Julia Stähler
AU  - Sergey A. Kovalenko
PY  - 2026
DA  - 2026/09/24
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15002784/v4
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15002784/v4
AB  - Photoinduced electron transfer (ET) in symmetric donor-acceptor-donor (D-A-D) or acceptor-donor-acceptor (A-D-A) molecules attracts attention due to applications in advanced materials. It is normally assumed that ET occurs asymmetrically, from one donor to acceptor, thus breaking molecular symmetry and resulting in a dipole moment in the excited state. However, the symmetry can be preserved with symmetric ET from both donors, leading to a nondipolar state with a high quadrupole moment. Here we report on symmetric ET in a D-A-D probe, 5,5'-di(9H-carbazol-9-yl)-2,2'-bipyridine. This probe is weakly solvatochromic in absorption, but highly solvatochromic in emission, revealing a nonlinear spectral shift and strong decay of the oscillator strength in solvents of increasing polarity. We develope a 3-excited-state model that fits the data quite well for symmetric ET, while no reasonable fit is possible for asymmetric ET. The model predicts the symmetric ET to be barrierless and ultrafast, in good agreement with observations.
ER  -