2 research outputs found
Excitonic Interactions in Bacteriochlorin Homo-Dyads Enable Charge Transfer: A New Approach to the Artificial Photosynthetic Special Pair
Excitonically coupled
bacteriochlorin (BC) dimers constitute a
primary electron donor (special pair) in bacterial photosynthesis
and absorbing units in light-harvesting antenna. However, the exact
nature of the excited state of these dyads is still not fully understood.
Here, we report a detailed spectroscopic and computational investigation
of a series of symmetrical bacteriochlorin dimers, where the bacteriochlorins
are connected either directly or by a phenylene bridge of variable
length. The excited state of these dyads is quenched in high-dielectric
solvents, which we attribute to photoinduced charge transfer. The
mixing of charge transfer with the excitonic state causes accelerated
(within 41 ps) decay of the excited state for the directly linked
dyad, which is reduced by orders of magnitude with each additional
phenyl ring separating the bacteriochlorins. These results highlight
the origins of the excited-state dynamics in symmetric BC dyads and
provide a new model for studying the primary processes in photosynthesis
and for the development of artificial, biomimetic systems for solar
energy conversion
What Is the Optoelectronic Effect of the Capsule on the Guest Molecule in Aqueous Host/Guest Complexes? A Combined Computational and Spectroscopic Perspective
Encapsulation
of dye molecules is used as a means to achieve charge
separation across different dielectric environments. We analyze the
absorption and emission spectra of several coumarin molecules that
are encapsulated within an octa-acid dimer forming a molecular capsule.
The water-solvated capsule effect on the coumarin’s electronic
structure and absorption spectra can be understood as due to an effective
dielectric constant where the capsule partially shields electrostatically
the dielectric solvent environment. Blue-shifted emission spectra
are explained as resulting from a partial intermolecular charge transfer
where the capsule is the acceptor, and which reduces the coumarin
relaxation in the excited state