Unraveling the Mechanism of Photoinduced Charge Transfer
in Carotenoid–Porphyrin–C<sub>60</sub> Molecular Triad
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Abstract
Photoinduced
charge transfer (CT) plays a central role in biologically
significant systems and in applications that harvest solar energy.
We investigate the relationship of CT kinetics and conformation in
a molecular triad. The triad, consisting of carotenoid, porphyrin,
and fullerene is structurally flexible and able to acquire significantly
varied conformations under ambient conditions. With an integrated
approach of quantum calculations and molecular dynamics simulations,
we compute the rate of CT at two distinctive conformations. The linearly
extended conformation, in which the donor (carotenoid) and the acceptor
(fullerene) are separated by nearly 50 Å, enables charge separation
through a sequential CT process. A representative bent conformation
that is entropically dominant, however, attenuates the CT, although
the donor and the acceptor are spatially closer. Our computed rate
of CT at the linear conformation is in good agreement with measured
values. Our work provides unique fundamental understanding of the
photoinduced CT process in the molecular triad