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Volpert, Sabrina ; Hashemi, Zohreh ; Förster, Johannes ; Marques, Mario R. G. ; Schelter, Ingo ; Kümmel, Stephan ; Leppert, Linn:
Delocalized electronic excitations and their role in directional charge transfer in the reaction center of Rhodobacter sphaeroides.
In: The Journal of Chemical Physics.
Bd. 158
(2023)
Heft 19
.
- 195102.
ISSN 0021-9606
DOI: https://doi.org/10.1063/5.0139691
Abstract
In purple bacteria, the fundamental charge-separation step that drives the conversion of radiation energy into chemical energy proceeds
along one branch—the A branch—of a heterodimeric pigment–protein complex, the reaction center. Here, we use first principles time-
dependent density functional theory (TDDFT) with an optimally-tuned range-separated hybrid functional to investigate the electronic and
excited-state structure of the six primary pigments in the reaction center of Rhodobacter sphaeroides. By explicitly including amino-acid
residues surrounding these six pigments in our TDDFT calculations, we systematically study the effect of the protein environment on energy
and charge-transfer excitations. Our calculations show that a forward charge transfer into the A branch is significantly lower in energy
than the first charge transfer into the B branch, in agreement with the unidirectional charge transfer observed experimentally. We further
show that the inclusion of the protein environment redshifts this excitation significantly, allowing for energy transfer from the coupled
Qx excitations. Through analysis of transition and difference densities, we demonstrate that most of the Q-band excitations are strongly
delocalized over several pigments and that both their spatial delocalization and charge-transfer character determine how strongly affected
they are by thermally-activated molecular vibrations. Our results suggest a mechanism for charge-transfer in this bacterial reaction center and
pave the way for further first-principles investigations of the interplay between delocalized excited states, vibronic coupling, and the role of
the protein environment in this and other complex light-harvesting systems.
Weitere Angaben
| Publikationsform: | Artikel in einer Zeitschrift |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten Fakultäten > Fakultät für Mathematik, Physik und Informatik Fakultäten > Fakultät für Mathematik, Physik und Informatik > Physikalisches Institut Fakultäten > Fakultät für Mathematik, Physik und Informatik > Physikalisches Institut > Lehrstuhl Theoretische Physik IV Graduierteneinrichtungen > Elitenetzwerk Bayern > Biological Physics |
| Titel an der UBT entstanden: | Ja |
| Themengebiete aus DDC: | 500 Naturwissenschaften und Mathematik > 530 Physik 500 Naturwissenschaften und Mathematik > 540 Chemie |
| Eingestellt am: | 16 Mai 2023 06:33 |
| Letzte Änderung: | 16 Mai 2023 06:33 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/76445 |