Thermodynamic equilibrium between locally excited and charge-transfer states through thermally activated charge transfer in 1-(pyren-2′-yl)-o-carborane

Lei Ji*, Stefan Riese, Alexander Schmiedel, Marco Holzapfel, Maximillian Fest, Jörn Nitsch, Basile F.E. Curchod, Alexandra Friedrich, Lin Wu, Hamad H. Al Mamari, Sebastian Hammer, Jens Pflaum, Mark A. Fox, David J. Tozer, Maik Finze, Christoph Lambert, Todd B. Marder

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Reversible conversion between excited-states plays an important role in many photophysical phenomena. Using 1-(pyren-2′-yl)-o-carborane as a model, we studied the photoinduced reversible charge-transfer (CT) process and the thermodynamic equilibrium between the locally-excited (LE) state and CT state, by combining steady state, time-resolved, and temperature-dependent fluorescence spectroscopy, fs- and ns-transient absorption, and DFT and LR-TDDFT calculations. Our results show that the energy gaps and energy barriers between the LE, CT, and a non-emissive ‘mixed’ state of 1-(pyren-2′-yl)-o-carborane are very small, and all three excited states are accessible at room temperature. The internal-conversion and reverse internal-conversion between LE and CT states are significantly faster than the radiative decay, and the two states have the same lifetimes and are in thermodynamic equilibrium.

Original languageEnglish
JournalChemical Science
Publication statusAccepted/In press - 2022
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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