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Title: Photoinduced Intra- and Intermolecular Energy Transfer in Chlorophyll a Dimer

Abstract

By applying nonadiabatic excited-state molecular dynamics, we investigate excitation energy transfer and exciton localization dynamics in a chlorophyll a (Chl a) dimer system at the interface of two monomers of light-harvesting complex II trimer. After its optical excitation at the red edge of the Soret (B) band, the Chl a dimer experiences an ultrafast intra- and intermolecular nonradiative relaxation process to the lowest band (Q y). The energy relaxation is found to run faster in the Chl a dimer than in the Chl a monomer. Once the molecular system reaches the lowest Q y band composed of two lowest excited states S 1 and S 2, the concluding relaxation step involves the S 2 → S 1 population transfer, resulting in a relatively slower relaxation rate. The strength of thermal fluctuations exceeds intraband electronic coupling between the states belonging to a certain band (B, Q x, and Q y), producing localized states on individual chromophores. Therefore, time evolution of spatial electronic localization during internal conversion reveals transient trapping on one of the Chl a monomers participating in the events of intermonomeric energy exchange. In the phase space domains where electronic states are strongly coupled, these states become nearly degenerate promotingmore » Frenkel-exciton-like delocalization and interchromophore energy transfer. As energy relaxation occurs, redistribution of the transition density on two Chl a monomers leads to nearly equal distribution of the exciton among the molecules. For a single Chl a, our analysis of excitonic dynamics reveals wave function amplitude transfer from nitrogen and outer carbon atoms to inner carbon atoms during non-radiative relaxation.« less

Authors:
 [1];  [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Nanyang Technological Univ. (Singapore). Division of Materials Science
  2. National Univ. of Quilmes/CONICET, Bernal (Argentina)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division; National Research Foundation (NRF) (Singapore); Ministry of Education (Singapore); National Scientific and Technical Research Council (CONICET) (Argentina); National Agency for Scientific and Technological Promotion (ANPCyT) (Argentina)
OSTI Identifier:
1460648
Report Number(s):
LA-UR-17-21993
Journal ID: ISSN 1520-6106; TRN: US1901887
Grant/Contract Number:  
AC52-06NA25396; NRF-CRP5-2009-04; RG106/15; PICT-2014-2662
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 121; Journal Issue: 21; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 74 ATOMIC AND MOLECULAR PHYSICS

Citation Formats

Zheng, Fulu, Fernandez-Alberti, Sebastian, Tretiak, Sergei, and Zhao, Yang. Photoinduced Intra- and Intermolecular Energy Transfer in Chlorophyll a Dimer. United States: N. p., 2017. Web. doi:10.1021/acs.jpcb.7b02021.
Zheng, Fulu, Fernandez-Alberti, Sebastian, Tretiak, Sergei, & Zhao, Yang. Photoinduced Intra- and Intermolecular Energy Transfer in Chlorophyll a Dimer. United States. doi:10.1021/acs.jpcb.7b02021.
Zheng, Fulu, Fernandez-Alberti, Sebastian, Tretiak, Sergei, and Zhao, Yang. Mon . "Photoinduced Intra- and Intermolecular Energy Transfer in Chlorophyll a Dimer". United States. doi:10.1021/acs.jpcb.7b02021. https://www.osti.gov/servlets/purl/1460648.
@article{osti_1460648,
title = {Photoinduced Intra- and Intermolecular Energy Transfer in Chlorophyll a Dimer},
author = {Zheng, Fulu and Fernandez-Alberti, Sebastian and Tretiak, Sergei and Zhao, Yang},
abstractNote = {By applying nonadiabatic excited-state molecular dynamics, we investigate excitation energy transfer and exciton localization dynamics in a chlorophyll a (Chla) dimer system at the interface of two monomers of light-harvesting complex II trimer. After its optical excitation at the red edge of the Soret (B) band, the Chla dimer experiences an ultrafast intra- and intermolecular nonradiative relaxation process to the lowest band (Qy). The energy relaxation is found to run faster in the Chla dimer than in the Chla monomer. Once the molecular system reaches the lowest Qy band composed of two lowest excited states S1 and S2, the concluding relaxation step involves the S2 → S1 population transfer, resulting in a relatively slower relaxation rate. The strength of thermal fluctuations exceeds intraband electronic coupling between the states belonging to a certain band (B, Qx, and Qy), producing localized states on individual chromophores. Therefore, time evolution of spatial electronic localization during internal conversion reveals transient trapping on one of the Chla monomers participating in the events of intermonomeric energy exchange. In the phase space domains where electronic states are strongly coupled, these states become nearly degenerate promoting Frenkel-exciton-like delocalization and interchromophore energy transfer. As energy relaxation occurs, redistribution of the transition density on two Chla monomers leads to nearly equal distribution of the exciton among the molecules. For a single Chla, our analysis of excitonic dynamics reveals wave function amplitude transfer from nitrogen and outer carbon atoms to inner carbon atoms during non-radiative relaxation.},
doi = {10.1021/acs.jpcb.7b02021},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
number = 21,
volume = 121,
place = {United States},
year = {2017},
month = {5}
}

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