Intramolecular Singlet Fission in Individual Graphene Nanoribbons─Competition with a Charge Transfer
Journal of the American Chemical Society,
Год журнала:
2025,
Номер
unknown
Опубликована: Март 19, 2025
Graphene
nanoribbons
(NRs)
constitute
a
versatile
platform
for
developing
novel
materials,
where
their
structure
governs
optical,
electronic,
and
magnetic
properties
while
also
shaping
excited-state
dynamics.
Here,
we
investigate
set
of
three
twisted
N-doped
molecular
NRs
increasing
length,
obtained
by
linearly
fusing
perylene
diimide
to
pyrene
pyrazino-
or
thiadiazolo-quinoxaline
residues.
By
employing
various
temperature-dependent
time-resolved
spectroscopy
techniques,
reveal
how
the
flexible
NR
geometry
promotes
formation
mixed
electronic
state
with
varying
contributions
from
locally
excited
charge-transfer
(CT)
states.
The
fate
this
is
highly
sensitive
geometry,
solvent
polarity.
For
shortest
NR,
intersystem
crossing
dominates
deactivation
pathway,
efficiently
generating
triplets
in
low-polarity
solvents.
In
contrast,
extended
NRs,
intramolecular
singlet
fission
(SF)
takes
place
within
single
nanoribbon.
This
enabled
enhanced
superexchange
coupling
due
pronounced
push-pull
nature
existence
multiple
localized
π-electron
states
caused
heteroatom
doping,
thereby
circumventing
need
dimeric
interactions
typically
associated
conventional
SF
systems.
higher-polarity
environments,
evidence
(diabatic)
CT
emerges.
These
findings
underscore
intricate
relationship
between
energy
levels,
dynamics
NRs.
Язык: Английский
Reversible gating of singlet fission by tuning the role of a charge-transfer state
Nature Communications,
Год журнала:
2025,
Номер
16(1)
Опубликована: Март 26, 2025
Abstract
Stimulus-responsive
triplet
excited
states
and
multiexcitonic
logic
gates
have
garnered
increasing
interest.
Singlet
fission
is
an
efficient
multiple
exciton
generation
process,
in
which
one
singlet
converts
into
two
triplets.
is,
however,
rarely
reported
to
be
switchable
by
external
stimuli.
Here
we
design
a
meta
-diethynylphenylene-linked
tetracene
dimer
featuring
pyridyl
endgroups
that
function
as
acid/base-responsive
switch,
enabling
the
reversible
modulation
of
fission.
In
its
neutral
form,
interchromophore
charge-transfer
state
facilitates
promotes
formation
correlated
triplet-pair
state.
Upon
treatment
with
acid,
protonation
nitrogens
generates
more
strongly
electron-accepting
pyridinium,
leading
intra-chromophore
state,
inhibits
Finally,
IMPLICATION
gate
constructed
using
acid
base
inputs
monitoring
based
on
Язык: Английский
Molecular Acenes for Light Capture, Conversion, and Storage
Accounts of Materials Research,
Год журнала:
2024,
Номер
unknown
Опубликована: Дек. 19, 2024
ConspectusEfficient
photovoltaics
(PV)
require
capturing
and
converting
solar
energy
across
a
broad
range
of
energy.
Losses
due
to
thermalization
sub-bandgap
photons
place,
however,
significant
boundaries
on
the
performance
cells.
For
conventional
single-junction
cells,
theoretical
maximum
power
conversion
efficiency
is
capped
at
33%,
constraint
known
as
detailed
balance
limit.
Realizing
full
potential
PVs
requires
developing
novel
strategies
overcome
this
fundamental
obstacle.
This
Account
describes
photon-management
capabilities
acenes
addresses
these
losses
en-route
toward
enhancing
PV
performances.For
high-energy
that
exceed
semiconductor's
bandgap
energy,
singlet
fission
(SF)
down-conversion
pathway
mitigate
losses.
SF
process
in
organic
materials,
which
excited
state
split
into
two
independent
triplet
states,
effectively
doubling
number
charge
carriers.
Pentacenes
stand
out
among
their
exergonic
nature
SF.
Numerous
molecular
pentacene
dimers
have
been
synthesized
elucidate
relationship
between
structure
efficiency.A
broader
light-harvesting
materials
realized
by
covalently
attaching
complementary
absorbing
donors
set
up
donor–acceptor
conjugates.
Förster
resonance
transfer
(FRET)
operative
donor-acceptor
conjugates,
extending
absorption
donor
efficiently
transfers
its
absorbed
excitation
acceptor.
Our
studies
various
binding
motifs
show
FRET
depends
not
only
parameters
like
distance
spectral
overlap
but
also
subtle
factors
such
alignment
transition
dipoles,
significantly
affect
dynamics
efficiency.Turning
low-energy
photons,
triplet–triplet
annihilation
up-conversion
(TTA-UC)
provides
means
light
and,
thereby,
reduction
In
TTA-UC,
potent
enough
generate
carriers
formed
combining
excitons.
It
reverse
The
higher
tetracene
an
endergonic
renders
them
highly
effective
for
TTA-UC.
We
focus
tetracene-based
systems
maximize
TTA-UC
efficiency.Besides
two-photon
(TPA)
yet
another
mechanism
leverage
below-bandgap
photons.
nonlinear
optical
(NLO)
process,
reveal
NLO
properties
are
essential
near-infrared
still
powering
demonstrate
our
proof-of-concept
how
TPA
further
broadens
application
systems.The
outlined
illustrate
valuable
addressing
mechanistic
final
section,
we
examine
storage
following
interfacial
electron
transfer.
Efficient
charge-injection
powered
more
research
before
being
implemented
large-scale
designs.Overall,
advances
discussed
highlight
pivotal
role
model
investigate
photon
down-
processes
paint
promising
picture
efficient
schemes
exceeding
detailed-balance
limit
can
be
implementing
materials.
Язык: Английский
Ultrafast Intramolecular Singlet Fission in Homoconjugated Oligomers of Azapentacene with Rigid Connecting Unit
Advanced Optical Materials,
Год журнала:
2024,
Номер
unknown
Опубликована: Сен. 27, 2024
Abstract
A
novel
series
of
homoconjugated
oligomers
azapentacene,
linked
via
the
rigid
connecting
unit
bicyclo[2.2.2]octane
bridge
is
presented.
The
investigation
delves
into
intramolecular
singlet
fission
(iSF)
within
these
dimeric
and
trimeric
frameworks,
employing
various
time‐resolved
spectroscopies
quantum
chemical
calculations.
Combining
merits
both
through‐space
through‐bond
couplings
between
constituent
chromophores
structures,
iSF
proceeds
a
few
picoseconds,
exhibiting
2–3
orders
magnitude
acceleration
compared
to
traditional
covalently
achieving
an
efficiency
approaching
unity.
In
trimer,
larger
interplanar
angle
neighboring
leads
relatively
slower
rate
that
dimer.
Furthermore,
active
involvement
charge
transfer
state
demonstrated
accelerate
process
in
while
exerting
no
influence
on
study
provides
avenues
for
investigating
molecular
geometry
reveals
crucial
role
interplay
spatial
covalent
coupling
facilitating
fission.
Язык: Английский
The Interplay of Strongly and Weakly Exchange-Coupled Triplet Pairs in Intramolecular Singlet Fission
Journal of the American Chemical Society,
Год журнала:
2024,
Номер
146(43), С. 29664 - 29674
Опубликована: Окт. 17, 2024
Singlet
fission
(SF)
and
triplet-triplet
annihilation
upconversion
(TTA-UC)
nominally
enable
the
interconversion
of
higher-energy
singlet
states
with
two
lower-energy
triplet
vice
versa,
both
processes
having
envisaged
application
for
enhanced
solar
power
devices.
The
mechanism
SF/TTA-UC
involves
a
complex
array
different
multiexcitonic
triplet-pair
that
are
coupled
by
exchange
interaction
to
varying
extents.
In
this
work
family
bounded
intramolecular
SF
materials,
based
upon
chromophore
1,6-diphenyl-1,3,5-hexatriene,
were
designed
synthesized.
Their
behavior
was
characterized
using
fluorescence
lifetime,
transient
absorption,
magnetic
field
dependence
studies.
capacity
formation
weakly
exchange-coupled
pairs,
subsequent
spin-evolution,
is
shown
be
strongly
dependent
combined
factors
oligomer
size
geometry.
By
contextualizing
these
results
wider
literature,
we
present
general
schematic
model
greater
completeness
than
portrayed
elsewhere.
Язык: Английский