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On the Role of the Special Pair in Photosystems as a Charge Transfer Rectifier
journal contribution
posted on 2020-02-28, 18:41 authored by Huseyin Aksu, Alexander Schubert, Srijana Bhandari, Atsushi Yamada, Eitan Geva, Barry D. DunietzThe
special pair, a bacteriochlorophyll a (BChl) dimer found at
the core of bacterial reaction centers, is known to play a key role
in the functionality of photosystems as a precursor to the photosynthesis
process. In this paper, we analyze the inherent affinity of the special
pair to rectify the intrapair photo-induced charge transfer (CT).
In particular, we show that the molecular environment affects the
nuclear geometry, resulting in symmetry breaking between the two possible
intrapair CT processes. To this end, we study the relationships of
the intrapair CT and the molecular geometry with respect to the effective
dielectric constant provided by the molecular environment. We identify
the special pair structural feature that breaks the symmetry between
the two molecules, leading to CT rectification. Excited state energies,
oscillator strengths, and electronic coupling values are obtained
via time-dependent density functional theory, employing a recently
developed framework based on a screened range-separated hybrid functional
within a polarizable continuum model (SRSH-PCM). We analyze the rectification
capability of the special pair by calculating the CT rates using a
first-principles-based Fermi’s golden rule approach.
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Keywords
symmetryCharge Transfer Rectifierintrapair CToscillator strengthspolarizable continuum modeltime-dependent densityintrapair photo-induced charge transferSRSH-PCMreaction centersintrapair CT processesSpecial PairExcited state energiesCT rectificationphotosynthesis processrectification capabilityCT ratesrule approach