Multireference excitation energies for bacteriochlorophylls A within light harvesting system 2
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Multireference excitation energies for bacteriochlorophylls A within light harvesting system 2. / Anda, Andre; Hansen, Thorsten; De Vico, Luca.
I: Journal of Chemical Theory and Computation, Bind 12, Nr. 3, 2016, s. 1305-1313.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Multireference excitation energies for bacteriochlorophylls A within light harvesting system 2
AU - Anda, Andre
AU - Hansen, Thorsten
AU - De Vico, Luca
PY - 2016
Y1 - 2016
N2 - Light-harvesting system 2 (LH2) of purple bacteria is one of the most popular antenna complexes used to study Nature's way of collecting and channeling solar energy. The dynamics of the absorbed energy is probed by ultrafast spectroscopy. Simulation of these experiments relies on fitting a range of parameters to reproduce the spectra. Here, we present a method that can determine key parameters to chemical accuracy. These will eliminate free variables in the modeling, thus reducing the problem. Using MS-RASPT2/RASSCF calculations, we compute excitation energies and transition dipole moments of all bacteriochlorophylls in LH2. We find that the excitation energies vary among the bacteriochlorophyll monomers and that they are regulated by the curvature of the macrocycle ring and the dihedral angle of an acetyl moiety. Increasing the curvature lifts the ground state energy, which causes a red shift of the excitation energy. Increasing the torsion of the acetyl moiety raises the excited state energy, resulting in a blue shift of the excitation energy. The obtained results mark a giant leap for multiconfigurational multireference quantum chemical methods in the photochemistry of biological systems, which can prove instrumental in exposing the underlying physics of photosynthetic light-harvesting.
AB - Light-harvesting system 2 (LH2) of purple bacteria is one of the most popular antenna complexes used to study Nature's way of collecting and channeling solar energy. The dynamics of the absorbed energy is probed by ultrafast spectroscopy. Simulation of these experiments relies on fitting a range of parameters to reproduce the spectra. Here, we present a method that can determine key parameters to chemical accuracy. These will eliminate free variables in the modeling, thus reducing the problem. Using MS-RASPT2/RASSCF calculations, we compute excitation energies and transition dipole moments of all bacteriochlorophylls in LH2. We find that the excitation energies vary among the bacteriochlorophyll monomers and that they are regulated by the curvature of the macrocycle ring and the dihedral angle of an acetyl moiety. Increasing the curvature lifts the ground state energy, which causes a red shift of the excitation energy. Increasing the torsion of the acetyl moiety raises the excited state energy, resulting in a blue shift of the excitation energy. The obtained results mark a giant leap for multiconfigurational multireference quantum chemical methods in the photochemistry of biological systems, which can prove instrumental in exposing the underlying physics of photosynthetic light-harvesting.
U2 - 10.1021/acs.jctc.5b01104
DO - 10.1021/acs.jctc.5b01104
M3 - Journal article
C2 - 26796483
VL - 12
SP - 1305
EP - 1313
JO - Journal of Chemical Theory and Computation
JF - Journal of Chemical Theory and Computation
SN - 1549-9618
IS - 3
ER -
ID: 155554543