Journal of the American Chemical Society,
Год журнала:
2024,
Номер
146(32), С. 22818 - 22828
Опубликована: Июль 30, 2024
The
cage
escape
yield,
i.e.,
the
separation
of
geminate
radical
pair
formed
immediately
after
bimolecular
excited-state
electron
transfer,
was
studied
in
11
solvents
using
six
Fe(III),
Ru(II),
and
Ir(III)
photosensitizers
tri-p-tolylamine
as
donor.
Among
all
complexes,
largest
yields
(0.67–1)
were
recorded
for
photosensitizer,
showing
highest
potential
a
photocatalyst
photoredox
catalysis.
These
dropped
to
values
around
0.65
both
Ru(II)
0.38
Os(II)
photosensitizer.
Interestingly,
open-shell
Fe(III)
small
(<0.1)
with
dielectric
constant
greater
than
20
but
shown
reach
up
0.58
low
constants.
results
presented
herein
on
closed-shell
suggest
that
rate
triplet–singlet
intersystem
crossing
within
manifold
states
implies
charge
recombination
toward
ground
state
is
spin-forbidden
process,
favoring
large
are
not
influenced
by
effects.
Geminate
metal
such
two
herein,
no
longer
process
becomes
highly
sensitive
solvent
Altogether,
this
study
provides
general
guidelines
factors
influencing
reactivity
prototypical
also
allows
one
foresee
great
development
2LMCT
excited
catalysis,
providing
constants
used.
Chemical Reviews,
Год журнала:
2024,
Номер
124(11), С. 7379 - 7464
Опубликована: Май 14, 2024
The
utilization
of
visible
light
to
mediate
chemical
reactions
in
fluid
solutions
has
applications
that
range
from
solar
fuel
production
medicine
and
organic
synthesis.
These
are
typically
initiated
by
electron
transfer
between
a
photoexcited
dye
molecule
(a
photosensitizer)
redox-active
quencher
yield
radical
pairs
intimately
associated
within
solvent
cage.
Many
these
radicals
undergo
rapid
thermodynamically
favored
"geminate"
recombination
do
not
diffuse
out
the
cage
surrounds
them.
Those
escape
useful
reagents
may
subsequent
important
above-mentioned
applications.
process
factors
determine
yields
remain
poorly
understood
despite
decades
research
motivated
their
practical
fundamental
importance.
Herein,
state-of-the-art
on
light-induced
appeared
since
seminal
1972
review
J.
P.
Lorand
entitled
"The
Cage
Effect"
is
reviewed.
This
also
provides
some
background
for
those
new
field
discusses
both
homolytic
bond
photodissociation
bimolecular
induced
reactions.
concludes
with
key
goals
directions
future
promise
elevate
this
very
vibrant
even
greater
heights.
Journal of the American Chemical Society,
Год журнала:
2024,
Номер
unknown
Опубликована: Апрель 10, 2024
Substituting
precious
elements
in
luminophores
and
photocatalysts
by
abundant
first-row
transition
metals
remains
a
significant
challenge,
iron
continues
to
be
particularly
attractive
owing
its
high
natural
abundance
low
cost.
Most
complexes
known
date
face
severe
limitations
due
undesirably
efficient
deactivation
of
luminescent
photoredox-active
excited
states.
Two
new
iron(III)
with
structurally
simple
chelate
ligands
enable
straightforward
tuning
ground
state
properties,
contrasting
recent
examples,
which
chemical
modification
had
minor
impact.
Crude
samples
feature
two
luminescence
bands
strongly
reminiscent
complex,
this
observation
was
attributed
dual
luminescence,
but
our
case,
there
is
clear-cut
evidence
that
the
higher-energy
stems
from
an
impurity
only
red
photoluminescence
doublet
ligand-to-metal
charge
transfer
(2LMCT)
genuine.
Photoinduced
oxidative
reductive
electron
reactions
methyl
viologen
10-methylphenothiazine
occur
nearly
diffusion-limited
kinetics.
Photocatalytic
not
previously
reported
for
compound
class,
particular
C–H
arylation
diazonium
salts
aerobic
hydroxylation
boronic
acids,
were
achieved
low-energy
light
excitation.
Doublet–triplet
energy
(DTET)
2LMCT
anthracene
annihilator
permits
proof
principle
triplet–triplet
annihilation
upconversion
based
on
molecular
photosensitizer.
These
findings
are
relevant
development
featuring
photophysical
photochemical
properties
competitive
noble-metal-based
compounds.
Journal of the American Chemical Society,
Год журнала:
2024,
Номер
146(37), С. 25799 - 25812
Опубликована: Сен. 3, 2024
Photocatalysis
holds
great
promise
for
changing
the
way
value-added
molecules
are
currently
prepared.
However,
many
photocatalytic
reactions
suffer
from
quantum
yields
well
below
10%,
hampering
transition
lab-scale
to
large-scale
or
even
industrial
applications.
Molecular
dyads
can
be
designed
such
that
beneficial
properties
of
inorganic
and
organic
chromophores
combined,
resulting
in
milder
reaction
conditions
improved
reactions.
We
have
developed
a
novel
approach
obtaining
advantages
molecular
without
time-
resource-consuming
synthesis
these
tailored
photocatalysts.
Simply
by
mixing
cationic
ruthenium
complex
with
an
anionic
pyrene
derivative
water
salt
bichromophore
is
produced
owing
electrostatic
interactions.
The
long-lived
triplet
state
obtained
static
quantitative
energy
transfer
preorganized
complex.
exploited
this
so-called
Coulombic
dyad
catalysis
similar
reactivity
higher
photostability
compared
reference
photosensitizers
several
photooxygenations.
In
addition,
it
was
shown
system
also
used
maximize
yield
photoredox
This
due
intrinsically
cage
escape
after
photoinduced
electron
purely
compounds
heavy
atom-containing
molecules.
combination
laboratory-scale
as
mechanistic
irradiation
experiments
detailed
spectroscopic
investigations
provided
deep
insights
into
easy-to-use
photocatalyst
class.
Chemical Physics Reviews,
Год журнала:
2022,
Номер
3(4)
Опубликована: Ноя. 9, 2022
Metal-centered
(MC)
excited
states
(ESs)
of
3d
transition
metal
complexes
(TMCs)
often
possess
rather
low
energies
so
that
these
represent
the
lowest
energy
ESs.
Additionally,
MC
are
strongly
distorted,
hence
they
efficiently
decay
non-radiatively
to
ground
state.
As
bimolecular
photoinduced
electron
transfer
(PET)
and
(EnT)
processes
require
contact
substrate,
confinement
ES
wavefunction
makes
challenging.
Consequently,
considered
less
useful
as
compared
long-lived
charge
higher
with
wavefunctions
extending
onto
ligands.
Despite
supposed
drawbacks,
some
classes
TMCs
can
successfully
engage
in
PET
EnT
being
photoactive
states.
We
discuss
initial
examples
reactivity
covering
chromium,
manganese,
iron,
cobalt
aim
gain
a
deeper
understanding
identify
decisive
key
parameters.
Finally,
we
present
catalytic
photoredox
using
photosensitizers
suitable
Journal of the American Chemical Society,
Год журнала:
2023,
Номер
145(38), С. 20786 - 20791
Опубликована: Сен. 13, 2023
Increasing
interest
in
sustainable
chemistry
coupled
with
the
quest
to
explore
new
reactivity
has
spurred
research
on
first-row
transition
metal
complexes
for
potential
applications
a
variety
of
settings.
One
more
active
areas
is
photoredox
catalysis,
where
synthetically
tunable
nature
their
electronic
structures
provides
rich
palette
options
tailoring
desired
chemical
transformation.
Understanding
mechanism
excited-state
critical
informed
development
next-generation
catalysts,
which
turn
requires
information
concerning
propensity
excited
states
engage
electron
or
energy
transfer
processes.
Herein
we
provide
direct
evidence
highly
oxidizing
lowest-energy
ligand-field
(LF)
state
d6-low-spin
Co(III)
photosensitizer
[Co(4,4′-Br2bpy)3]3+
(where
4,4′-Br2bpy
4,4′-dibromo-2,2′-bipyridine).
The
redox
associated
LF
complex
was
bracketed
by
performing
bimolecular
quenching
studies
using
series
simple
organic
donors.
Time-resolved
absorption
spectroscopy
confirmed
dynamic
process
attributed
reductive
chromophore.
Analysis
Stern–Volmer
plots
each
chromophore-quencher
pair
revealed
limiting
value
Ered*
∼
1.25
V
vs
Fc/Fc+
metal-centered
state,
significantly
stronger
than
that
commonly
employed
metal-based
agents
such
as
[Ru(bpy)3]2+
(Ered*
=
0.32
Fc/Fc+)
and
[Ir(ppy)2(bpy)]+
0.27
Fc/Fc+).
These
results
suggest
this
class
chromophores
could
find
utility
requiring
activation
oxidatively
resistant
substrates
catalysis.
Angewandte Chemie International Edition,
Год журнала:
2023,
Номер
63(7)
Опубликована: Дек. 8, 2023
Abstract
Luminescent
metal
complexes
based
on
earth
abundant
elements
are
a
valuable
target
to
substitute
4d/5d
transition
as
triplet
emitters
in
advanced
photonic
applications.
Whereas
Cu
I
have
been
thoroughly
investigated
the
last
two
decades
for
this
purpose,
no
structure‐property‐relationships
efficient
luminescence
involving
excited
states
from
Zn
II
established.
Herein,
we
report
design
of
monomeric
carbene
zinc(II)
dithiolates
(CZT)
featuring
donor‐acceptor‐motif
that
leads
highly
thermally
activated
delayed
fluorescence
(TADF)
with
compounds
unprecedented
radiative
rate
constants
k
TADF
=1.2×10
6
s
−1
at
297
K.
Our
high‐level
DFT/MRCI
calculations
revealed
relative
orientation
ligands
involved
ligand‐to‐ligand
charge
transfer
(
1/3
LLCT)
is
paramount
control
process.
Specifically,
dihedral
angle
36–40°
very
reverse
intersystem‐crossing
(rISC)
order
10
9
due
spin‐orbit
coupling
(SOC)
mediated
by
sulfur
atoms
combination
small
ΔE
S1‐T1
ca.
56
meV.
