Regensburg 2022 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 39: Molecular Electronics and Excited State Properties
CPP 39.5: Vortrag
Donnerstag, 8. September 2022, 12:30–12:45, H38
Understanding charge transfer excitations in Bacteriochlorophyll dimers from first principles — •Zohreh Hashemi1, Matthias Knodt1, and Linn Leppert1,2 — 1Institute of Physics, University of Bayreuth, Germany — 2MESA+ Institute for Nanotechnology, University of Twente, Netherlands
Bacteriochlorophyll (BCL) molecules are the main pigments driving the primary excitation and charge transfer processes in photosynthetic bacteria. They are organized in highly coordinated multichromophoric complexes, embedded in protein, guaranteeing an efficient transfer of excitation energy from the light harvesting antennae to the reaction center where a charge transfer excitation triggers. In this contribution we focus on the electronic and excited state structure of BCL monomers and dimers found in the reaction center and light harvesting apparatus of the purple bacterium Rhodobacter sphaeroides. We asses the accuracy of ab initio GW+Bethe-Salpeter equation approach for BCL monomers considering a wide range of excitation energies, and find excellent agreement with experimental data and correlated wavefunction-based approaches. We also discuss notable differences to results from state-of-the-art time-dependent density functional theory, which can be traced back to the treatment of electron-hole interactions in both methods [1]. For dimeric systems we show that the energy and character of charge transfer excitations is strongly affected by distance and orientation of the BCL molecules, providing an intuitive understanding for the role of these excitations in different parts of the photosynthetic apparatus.