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Probing the Electronic Structure of Bacteriochlorophyll Radical Ions—A Theoretical Study of the Effect of Substituents on Hyperfine Parameters
Author(s) -
Sinnecker Sebastian,
Lubitz Wolfgang
Publication year - 2017
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12724
Subject(s) - hyperfine structure , chemistry , radical ion , electron paramagnetic resonance , bacteriochlorophyll , quadrupole , ion , photochemistry , radical , density functional theory , electronic structure , crystallography , computational chemistry , nuclear magnetic resonance , atomic physics , photosynthesis , organic chemistry , biochemistry , physics
In reaction centers ( RC s) of photosynthesis, a light‐induced charge separation takes place creating radical cations and anions of the participating cofactors. In photosynthetic bacteria, different bacteriochlorophylls ( BC hl) are involved in this process. Information about the electronic structure of the BC hl radical cations and anions can be obtained by measuring the electron spin density distribution via the electron–nuclear hyperfine interaction using EPR and ENDOR techniques. In this communication, we report isotropic hyperfine coupling constants (hfcs) of the BC hl b and g radical cations and anions, calculated by density functional theory, and compare them with the more common radical ions of BC hl a and with available experimental data. The observed differences in the computed hyperfine data are discussed in view of a possible distinction between these species by EPR / ENDOR methods. In addition, 14 N nuclear quadrupole coupling constants (nqcs) computed for BC hl a , b , g , and also for Chl a in their charge neutral, radical cation and radical anion states are presented. These nqcs are compared with experimental values obtained by ESEEM spectroscopy on several different radical ions.