The Journal of Physical Chemistry C,
Journal Year:
2024,
Volume and Issue:
128(43), P. 18170 - 18181
Published: Oct. 17, 2024
Multiresonance
thermally
activated
delayed
fluorescence
(MR-TADF)
emitters
have
gained
popularity
given
their
potential
of
attaining
negligible
singlet–triplet
energy
gaps,
i.e.,
ΔEST,
without
hindering
emission,
thus
increasing
the
reverse
and
direct
intersystem
crossing
rates
affecting
fluorescence.
This
is
achieved
due
to
singlet
triplet
states'
short-range
charge
transfer
character
(SRCT).
Thus,
obtaining
quantitative
information
about
SRCT
would
help
develop
new
MR-TADF
emitters.
work
studies
three
different
families
emitters:
DOBOA,
DiKTa,
OQAO.
First,
we
compute
adiabatic
ΔEST
with
four
methods
(TDA-CAM-B3LYP,
STEOM-DLPNO-CCSD,
ADC(2),
SCS-CC2).
Then,
(kr),
(kISC),
rate
constants.
For
kr,
assessed
effect
levels
approximations
on
calculations.
We
show
that
kr
does
not
depend
significantly
harmonic
models
(adiabatic
Hessian
or
vertical
Hessian),
coordinate
systems,
broadening
widths.
Moreover,
Herzberg–Teller
effects
are
for
but
main
contribution
kISC
kRISC.
The
computed
constants
agree
well
experimental
results.
propose
use
two
wave
function
descriptors,
Qat
LOCa,
based
1-particle
transition
density
matrix,
which
assigns
amount
centered
atoms.
these
descriptors
transitions:
S0
→
S1,
T1,
S1
T1.
studied
cases,
independent
choice
electronic
structure
method
optimal
geometry.
decreases
increase
T1
Qat,
while
increases
an
Qat.
These
trends
showcase
how
values
can
act
as
guiding
design
small
values.
Journal of Chemical Theory and Computation,
Journal Year:
2024,
Volume and Issue:
20(13), P. 5655 - 5678
Published: June 17, 2024
In
the
realm
of
photochemistry,
significance
double
excitations
(also
known
as
doubly
excited
states),
where
two
electrons
are
concurrently
elevated
to
higher
energy
levels,
lies
in
their
involvement
key
electronic
transitions
essential
light-induced
chemical
reactions
well
challenging
nature
from
computational
theoretical
chemistry
point
view.
Based
on
state-of-the-art
structure
methods
(such
high-order
coupled-cluster,
selected
configuration
interaction,
and
multiconfigurational
methods),
we
improve
expand
our
prior
set
accurate
reference
excitation
energies
for
states
exhibiting
a
substantial
amount
[Loos
et
al.
J.
Chem.
Theory
Comput.
2019,
15,
1939].
This
extended
collection
encompasses
47
across
26
molecular
systems
that
separate
into
distinct
subsets:
(i)
28
"genuine"
almost
exclusively
involve
configurations
(ii)
19
"partial"
which
exhibit
more
balanced
character
between
singly
configurations.
For
each
subset,
assess
performance
coupled-cluster
(CC3,
CCSDT,
CC4,
CCSDTQ)
(CASPT2,
CASPT3,
PC-NEVPT2,
SC-NEVPT2).
Using
probe
percentage
single
involved
given
transition
(%T1)
computed
at
CC3
level,
also
propose
simple
correction
reduces
errors
by
factor
3,
both
sets
excitations.
We
hope
this
complete
diverse
compilation
will
help
future
developments
excited-state
methodologies.
Journal of Chemical Theory and Computation,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Sept. 12, 2024
The
discovery
of
singlet-triplet
(ST)
inversion
in
some
π-conjugated
triangle-shaped
boron
carbon
nitrides
is
a
remarkable
breakthrough
that
defies
Hund's
first
rule.
Deeply
rooted
strong
electron-electron
interactions,
ST
has
garnered
significant
interest
due
to
its
potential
revolutionize
triplet
harvesting
organic
LEDs.
Using
the
well-established
Pariser-Parr-Pople
model
for
correlated
electrons
systems,
we
employ
combination
CISDT
and
restricted
active
space
configuration
interaction
calculations
investigate
photophysics
several
triangular
nitrides.
Our
findings
reveal
these
systems
primarily
driven
by
network
alternating
electron-donor
electron-acceptor
groups
molecular
rim,
rather
than
structure
itself.
The Journal of Physical Chemistry C,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Dec. 3, 2024
Aromatic
imide-based
thermally
activated
delayed
fluorescence
(TADF)
emitters
have
become
increasingly
popular
due
to
their
unique
properties
such
as
rigid
structures,
pronounced
thermal
stability,
strong
electron-withdrawing
ability,
and
exceptional
photoluminescence
characteristics.
In
this
work,
the
phthalimide
unit
is
integrated
with
carbazole
donor
in
different
molecular
designs
(D-π-A,
π-A-D,
π-A-D2,
D-π-A-D)
TADF
room-temperature
phosphorescence
(RTP)
are
theoretically
investigated.
Descriptors
energy
gap
between
singlet
triplet
excited
states
(ΔEST),
spin
orbit
coupling
(SOC),
charge
transfer
(CT)
indices,
rate
constants
of
state
processes
were
analyzed
study
nature
state.
The
D-π-A
D-π-A-D
molecules
possess
small
ΔEST,
CT-dominated
S1
T1
states,
relatively
low
SOC
values,
high
radiative
reverse
intersystem
crossing
(RISC)
rates,
while
π-A-D
π-A-D2
direct
substitution
on
core
showed
large
state,
hybridized
local
SOC,
crossing,
RISC
rates.
Careful
analysis
energy-level
diagram
hole–electron
distribution
revealed
role
closely
lying
T2
fast
up-conversion
excitons
through
a
multichannel
process
π-A-D2-
D-π-A-D-based
molecules.
Overall,
parameters
indicative
emission,
inherit
facilitating
RTP
emission.
Additionally,
can
display
emission;
contrary,
poor
propensity.
Radical
emitters
have
attracted
considerable
interest
because
of
their
potential
to
surpass
the
limitations
singlet
due
spin
statistics,
thereby
revolutionizing
organic
LEDs.
Utilizing
well-known
Pariser-Parr-Pople
(PPP)
model
for
correlated
electrons
in
π-conjugated
systems,
we
perform
extended
CISDT
(XCISDT)
calculations
explore
photophysics
various
phenalenyl
radicals
differently
decorated
with
nitrogen
atoms.
By
introducing
PPP
particle-hole
difference
operator
and
connecting
it
DFT
calculations,
offer
a
new
tool
predicting
highly
emissive
using
ground
state
quantum
chemistry
methods.
ChemPhotoChem,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Oct. 1, 2024
Abstract
During
the
last
decade,
thermally
activated
delayed
fluorescence
has
been
topic
of
intense
research
due
to
its
great
potential
for
highly
efficient
all
organic
light
emitting
devices.
While
quinazoline
heterocycle
used
electron
withdrawing
ability
in
various
push‐pull
dyes,
derivatives
have
rarely
considered
TADF
emitters.
Here
we
design
and
synthesize
a
new
series
dyes
with
phenyl‐
or
methoxy‐substituted
rings
combined
9,9‐dimethylacridan,
phenoxazine
phenothiazine
either
1,4‐phenylene
2,5‐thienylene
as
linker.
Combining
optical
spectroscopy
theoretical
investigations,
demonstrate
that
is
observed
solid
state
phenyl‐substituted
which
both
quasi‐equatorial
quasi‐axial
conformations
are
predicted
coexist.
Calculations
further
suggest
reversed
intersystem
crossing
likely
involve
second
triplet
shows
small
energy
splitting
first
singlet
state.
These
results
prompt
investigations
based
TADF.
Advanced Optical Materials,
Journal Year:
2024,
Volume and Issue:
unknown
Published: Nov. 18, 2024
Abstract
Embedding
donor–acceptor
type
thermally
activated
delayed
fluorescence
(TADF)
molecules
in
a
rigid
surrounding
lead
to
structural
inhomogeneity,
and
deteriorating
emission
decay
rates.
Designing
TADF
structures
with
hampered
rotational
flexibility
between
donor
acceptor
units
is
shown
lower
the
conformational
disorder.
However,
this
work,
it
that
not
always
enough.
In
fact,
negative
impact
of
inhomogeneity
may
be
reduced
by
lowering
singlet‐triplet
energy
gap
(Δ
E
ST
)
boosting
reverse
intersystem
crossing
(rISC)
rate
while
preserving
same
donor‐acceptor
orientation.
such
cases
Δ
enables
early
triplet
upconversion
even
from
conformers
unfavorably
low
D‐A
twist
angles,
which
observed
compounds
larger
.
way,
temporal
shifts
prompt
are
evidently
reduced.
When
inactive
at
temperatures,
nearly
peak
observed,
as
expected
for
similar
molecular
geometry.
rapid
rISC
fundamental
importance
only
efficiency
but
also
dynamics
solid‐state.
