Electron Push-Pull Effects on Intramolecular Charge Transfer in Perylene-Based Donor-Acceptor Compounds

Article abstract of DOI:10.1021/acs.joc.0c02149

A series of asymmetric donor-acceptor (D-A) perylene-based compounds, 3-(N,N-bis(4′-(R)-phenyl)amino)perylene (Peri-DPA(R)), were successfully prepared to explore their intramolecular charge transfer (ICT) properties. To induce ICT between the donor and acceptor, diphenylamine (DPA) derivatives (electron donor units) with the same functional groups (R = CN, F, H, Me, or OMe) at both para positions were linked to the C-3 position of perylene to produce five Peri-DPA derivatives. A steady-state spectroscopy study on Peri-DPA(R)s exhibited a progressively regulated ICT trend consistent with the substituent effect as it progressed from the electron-withdrawing group to the electron-donating group. In particular, a comparative study using a D-A-D (donor-acceptor-donor) system demonstrated that not only the electron push-pull substituent effect but also subunit combinations influence photophysical and electrochemical properties. The different ICT characters observed in Lippert-Mataga plots of D-A(CN) and D-A-D(CN) (CN-substituted D-A and D-A-D) led to the investigation on whether ICT emission of two systems with differences in subunit combinations is of the same type or of a different type. The femtosecond transient absorption (fs-TA) spectroscopic results provided direct evidence of ICT origin and confirmed that D-A(CN) and D-A-D(CN) exhibited the same transition mix of ICT (from donor to acceptor) and reverse ICT (rICT, from arylamine to CN unit). Density functional theory (DFT)/TD-DFT calculations support the presence of ICT for all five compounds, and the experimental observations of rICT presented only for CN-substituted compounds.

Full text of DOI:10.1021/acs.joc.0c02149

pubs.acs.org/joc
Article
Electron Push−Pull Effects on Intramolecular Charge Transfer in
Perylene-Based Donor−Acceptor Compounds
Mina Ahn, Min-Ji Kim, Dae Won Cho,* and Kyung-Ryang Wee*
Cite This: https://dx.doi.org/10.1021/acs.joc.0c02149
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: A series of asymmetric donor−acceptor (D−A) perylene-based compounds,
3-(N,N-bis(4′-(R)-phenyl)amino)perylene (Peri−DPA(R)), were successfully prepared to
explore their intramolecular charge transfer (ICT) properties. To induce ICT between the
donor and acceptor, diphenylamine (DPA) derivatives (electron donor units) with the same
functional groups (R = CN, F, H, Me, or OMe) at both para positions were linked to the C-
3 position of perylene to produce five Peri−DPA derivatives. A steady-state spectroscopy
study on Peri−DPA(R)s exhibited a progressively regulated ICT trend consistent with the
substituent effect as it progressed from the electron-withdrawing group to the electron-
donating group. In particular, a comparative study using a D−A−D (donor−acceptor−
donor) system demonstrated that not only the electron push−pull substituent effect but also
subunit combinations influence photophysical and electrochemical properties. The different
ICT characters observed in Lippert−Mataga plots of D−A(CN) and D−A−D(CN) (CN-
substituted D−A and D−A−D) led to the investigation on whether ICT emission of two
systems with differences in subunit combinations is of the same type or of a different type.
The femtosecond transient absorption (fs-TA) spectroscopic results provided direct evidence of ICT origin and confirmed that D−
A(CN) and D−A−D(CN) exhibited the same transition mix of ICT (from donor to acceptor) and reverse ICT (rICT, from
arylamine to CN unit). Density functional theory (DFT)/TD-DFT calculations support the presence of ICT for all five compounds,
and the experimental observations of rICT presented only for CN-substituted compounds.
Recently, our group reported the ICT properties on the
perylene-based donor−acceptor−donor (D−A−D) system
with regard to the electron push−pull substituent effect.24
Specifically, good linear correlations between photophysical
properties and Hammett substituent constants showed that all
perylene-based D−A−D compounds with electron-withdraw-
ing and donating R groups (R = CN, F, H, Me, and OMe)
followed the same ICT trend. In addition, the ICT properties
of these systems were systematically controlled by donor
modulation, which allowed emission colors to be effectively
tuned. However, in Lippert−Mataga plots, a different charge-
transfer character was observed for the CN-substituted
perylene-based D−A−D compound. As a result, we suggested
that emission color tuning for the D−A−D molecular system is
limited in terms of generating high-energy blue emission due
to reverse ICT (rICT) from arylamine to CN unit caused by
the presence of a strong electron-withdrawing group. In this
report, along the line of the study, we carefully investigated the
INTRODUCTION
■
Donor−acceptor molecules containing dipolar organic chro-
mophores exhibiting intramolecular charge transfer (ICT) are
a class of functional π-conjugated organic systems, which are
useful tunable molecules in the solar energy conversion and
storage,1,2 molecular electronic,3−5 photovoltaic,6−8 photo-
eletrochemical cell (PEC),9 and light-emitting diode10−12
fields. ICT generally occurs in push−pull molecular systems
containing an electron donor (D) and an electron acceptor
(A).13−16 Various push−pull molecules are known to have
small band gaps and relatively strong dipoles, which contribute
to efficient ICT.17,18 The ICT character of a D−A system is
critical in terms of its optical and electronic properties19−21
and can be controlled by using suitable combinations of the
donor and acceptor components.22,23 Also, combinations of D
and A strongly affect frontier orbital levels, and thus, can be
used to tune the optoelectronic properties.17
Received: September 6, 2020
https://dx.doi.org/10.1021/acs.joc.0c02149
© XXXX American Chemical Society
J. Org. Chem. XXXX, XXX, XXX−XXX
A

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
a
Scheme 1. Synthetic Route to Peri−DPA(R)
a
Reagents and conditions: (i) CuI, LiNH2, K3PO4, DMF, reflux, 24 h. (ii) NBS, anhydrous tetrahydrofuran (THF), 24 h, r.t. (iii) Pd(dba)3,
Xantphos, NaOt-Bu, toluene, reflux, 24 h.
Figure 1. ORTEP drawings of compound 1a. Ellipsoid contour percent probability level is 50%.
electron push−pull effects of substituents in a perylene-based
D−A system with a particular focus on ICT and rICT.
To allow comparisons with our previous study on a D−A−D
system, we prepared an asymmetric D−A molecular structure,
similar to the D−A−D system using diphenylamine (DPA)
derivatives as electron donors and perylene as the electron
acceptor. The electron-rich diphenylamine (DPA) is widely
used as a functional group to facilitate electron donor and/or
hole transport properties.25−28 On the other hand, perylene
derivatives have been intensively investigated as functional
materials in optoelectronics due to their chemical, thermal, and
photochemical stabilities,29,30 high fluorescence quantum
yields,31,32 and planar geometries.33,34 Given the symmetry of
perylene, the attachment of the donor or acceptor subunit in
the same direction as the direction of ICT intensifies the
oscillator strength and increases the absorption capacity.35
Therefore, we selected a series of well-conjugated perylene D−
A molecules by connecting DPA at 3-position, an active site on
the perylene core.36−39 In addition, to simplify the comparison,
identical substituents were introduced at the para positions of
N,N-diphenylamine.
Although the ICT properties for various D−A and D−A−D
derivatives have been investigated, however, molecular
structure−property relationship studies that have compared
the ICT properties of analogous perylene-based D−A and D−
A−D molecular systems are limited.40,41 In the present study,
we aimed to investigate and compare how push−pull
substituent influences ICT properties in perylene-based D−A
and D−A−D systems. The photophysical ICT properties of
both systems were compared and analyzed using steady-state
and time-resolved optical spectroscopy. The optical absorption
spectroscopic and electrochemical properties confirmed that
highest-energy occupied molecular orbital−lowest-energy
unoccupied molecular orbital (HOMO−LUMO) gaps were
modulated by the introduction of substituents, showing that
the D−A system with one DPA substituent had a larger gap
than the D−A−D system with two DPA substituents. With
regard to energy band-gap control, the optical emission
spectroscopic properties showed a wider color tuning range
with larger width variation by substituents, for the D−A system
than the D−A−D system. In particular, steady-state spectro-
scopic results in various solvents showed that the dipole
B
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
moments of molecules affected by substituents varies with the
subunit combinations, which may lead to differences in the
type of ICT emission control between the two systems.
Furthermore, femtosecond transient absorption (fs-TA)
spectroscopic results demonstrated that the origins of
emissions in D−A and D−A−D systems, even in systems
containing the CN unit (D−A(CN) and D−A−D(CN)), were
identical.
RESULTS AND DISCUSSION
■
Synthesis. The target perylene-based D−A compounds
(Peri−DPA(R)s), 3-(p-(R)-diphenylamino)perylene (1) (R:
CN (1a), F (1b), H (1c), Me (1d), and OMe (1e)), were
synthesized as outlined in Scheme 1. Donor precursors, p-(R)-
diphenylamine (2) (R: CN (2a), F (2b), H (2c), Me (2d),
and OMe (2e)) with the same electron-donating or -with-
drawing group at the para-positions of diphenylamines, were
prepared according to the previously reported procedures.50
The acceptor precursor, 3-bromoperylene (3), was prepared by
the bromination using N-bromosuccinimide (NBS). Perylene-
based D−A compounds were successfully synthesized by Pd-
catalyzed Buchwald amination between 1 molar ratio of p-(R)-
diphenylamine (2) and 3-bromoperylene (3). Specifically, the
five 3-(p-(R)-diphenylamino)perylenes (1a−1e) were pre-
pared in the presence of 5 mol % Pd2(dba)3 using Xantphos
as a catalyst and excess amounts of NaOt-Bu as a base; they
were obtained as a yellow or orange solid in the toluene solvent
with a yield of 64−72%. All five compounds were purified by
silica gel column chromatography using hexane/dichloro-
methane mixtures as eluents and were further purified by
recrystallization. The molecular structures of all of the
compounds were determined by 1H and 13C{1H} NMR
(Figures S1−S10), elemental analysis, and mass spectrometry
(Figure S11). Finally, the structure of 1a was authenticated by
single-crystal X-ray crystallography. The Experimental Section
and the Supporting Information (SI) provide detailed synthetic
procedures and characterization data.
A single crystal of 1a was grown by slow evaporation from a
CH2Cl2/hexane mixture (1:2 v/v) at room temperature (RT),
and analyzed by single-crystal X-ray diffraction (XRD)
crystallography using synchrotron radiation. Compound 1a
crystallized in the monoclinic space group P21/n; crystal data
and collection parameters are summarized in Tables S1 and S2.
Figures 1, S12, and S13 show Oak Ridge thermal ellipsoid plot
(ORTEP) drawings and packing of 1a, respectively. In the
packing diagram (Figure S13), 1a molecules were stacked in a
herringbone fashion42 without face-to-face π−π overlap
between perylene cores. As shown in Figure 1, the two para-
substituted phenyl rings in 1a were twisted in different
directions with respect to the perylene core at angles of
45.0(6)° (C1−N1−C21−C22) and 16.5(6)° (C1−N1−C28−
C29), which was consistent with that obtained by density
functional theory (DFT) optimization of ground-state
geometry.
Figure 2. UV−vis absorption (top) and emission (bottom) spectra:
1a (blue), 1b (red), 1c (green), 1d (purple), 1e (orange) in CH2Cl2
at 10 μM.
(DPA) and perylene moieties, respectively. This transition
explicitly shows characteristic absorbances of each subunit of
the perylene core S0 → S2 excitation and the DPA series, while
maintaining its intrinsic spectral shape, as shown in Figures
S14 and S15. A broad, structureless band at 400−525 nm
1
corresponds to the S0 → CT transition, which showed the
presence of an intramolecular interaction in the ground state
regarding electronic coupling between the DPA and perylene
units. As was expected based on considerations of substituent
effects, red shift of the CT band followed the order 1a < 1b <
1c < 1d < 1e. In particular, the CT band of 1a exhibited a
structured peak similar to S0 → S1 excitation of the perylene
core (vibration energy of 1441 cm−1) (Figure S16) because the
strong electron-withdrawing ability of the CN unit caused
weak electronic coupling with the perylene unit.
As compared with the D−A−D system, the D−A system
showed a shorter wavelength range and a smaller shift in the
absorption maxima wavelength (Figure S20 top), indicating
the reduced conjugation length and relatively weak energy
control by fewer DPA substituents in the ground state.
Moreover, the structured CT band of 1a was more clearly
observed in the D−A system than in the D−A−D system
(Figure S17), which showed that the asymmetric D−A system
retains the electronic structure of perylene itself, while the
symmetric D−A−D system loses some of the electronic
structure of perylene itself. For this reason, the properties of
subunits were more prominent in the D−A system than in the
D−A−D system. Regarding intermolecular interactions, thin-
film absorption and emission spectra of 1a−1e (Figure S18)
Photophysical Properties. Steady-state optical absorp-
tion and emission spectra of the five Peri−DPA(R)s were
measured both in solution (Figure 2) and in solid state (Figure
S18), and the spectral parameters are summarized in Table 1.
As shown in Figure 2 (top), the spectrum of each compound
exhibited two types of absorption bands, that is, high-energy
absorption at 250−350 nm and low-energy absorption at 400−
525 nm. Absorption vibronic structures at 250−350 nm
1
correspond to the S0 → LE transitions of the diphenylamine
C
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
Table 1. Photophysical Properties of 1a−1e
c
λmaxabs (nm)
λmaxPL(nm)
Φf
a
b
a
b
a
d
7
−1
7
−1
Stokes shift (cm−1
)
sol
τF (ns)
krad × 10 (s
)
knr × 10 (s
)
krad/knr
e
e
compd
sol /film
sol /film
1a
1b
1c
1d
1e
453/472
459/482
459/483
468/492
476/512
486/560
517/549
523/567
543/570
592/599
1499
3012
3377
3747
5034
0.60
0.58
0.54
0.55
0.17
4.076
6.368
6.616
9.058
6.467
14.7
9.11
8.16
6.07
9.83
6.59
6.95
4.97
12.8
1.50
1.38
1.17
1.22
0.20
2.63
a
b
c
Absorption and emission maximum for the lowest energy band in CH2Cl2 at room temperature (RT). Measured in thin films. Fluorescence
d
e
quantum yields, with 9,10-diphenylanthracene (ΦPL = 0.95, ethanol) as the standard, in CH2Cl2 at RT. Fluorescence lifetime in CH2Cl2. Values
of krad and knr were calculated using krad = Φf/τF and knr = (1/τF) − krad
.
were found to exhibit red shifts as compared with spectra
obtained in hexane, which suggested that as was observed in
the D−A−D system, the D−A system also forms J-aggregates.
The fluorescence properties of the Peri−DPA(R)s in
CH2Cl2 solutions were studied and compared. As was observed
for maximum absorption, emission maxima were greatly
influenced by substituents. The emission maxima of the
Peri−DPA(R)s are in the range of 486−592 nm for systematic
red shifts and the extended spectral bandwidth (Figure 2,
bottom). The emission spectrum of 1a had a structured peak
as observed in the CT absorption spectrum (Figures 2 and S20
left), indicating a small structural change between the ground
and excited states. In other words, unlike other members of the
Peri−DPA(R), the excited state of 1a retained some of the
characteristics of the ground state, due to a strong electron-
withdrawing effect of the CN unit. In addition, as shown in
Table 1 and Figure S21, depending on the substituent effect,
the increase in Stokes shifts, that is, 1499 cm−1 for 1a, 3012
cm−1 for 1b, 3377 cm−1 for 1c, 3747 cm−1 for 1d, and 5034
cm−1 for 1e, was observed, indicating an increase in the CT
character in the excited state. The fluorescence quantum yields
(Φf) of Peri−DPA(R)s showed a gradual decrease of 17−60%
as the electron-donating power of substituents increased.
Fluorescence lifetimes varied from 4 to 10 ns in CH2Cl2, and
all fluorescence decay profiles showed exponential decay,
suggestive of radiative decay from a single excited state (Figure
S19). Using the Φf and τF values of Peri−DPA(R)s, the
radiative and nonradiative decay rate constants (krad and knr)
were calculated and determined in the range of ∼107. From the
electron-withdrawing group (EWG) to the electron-donating
group (EDGs) substitution, the krad values gradually decreased,
while the knr value did not show a gradual increase (Table 1).
These results show that the krad values are controlled by the
electron push−pull substituent effects that influence the typical
single CT emission band.
Considering the above-mentioned results on the D−A
system, the CT emission properties of D−A and D−A−D
subunit combinations were compared. The D−A system
showed a slightly larger shift range of maximum emission
wavelengths than the D−A−D system (Figure S20 bottom),
which shows a relatively wider energy control range by
substituents in the excited state caused by more polarization of
the asymmetric D−A system. In both systems, the spectral shift
intervals were broader in the excited states than in the ground
states, but the degrees of change in shift intervals between the
ground and excited states were significantly greater in the D−A
system (Figure S20), which was ascribed to charge
delocalization in the symmetric D−A−D system and relatively
more localization in the asymmetric D−A system than in the
D−A−D system. For the same substituents, the D−A system
exhibited a larger Stokes shift than the D−A−D system (Figure
S21), leading to lower Φf and longer τF values, which was
caused by structural flexibility due to greater reorganization
energy in the excited state. However, for CN unit substitution,
Stokes shifts in the D−A−D system were larger (Figure S21).
This is due to rICT from arylamine to the CN unit by strong
EWG ability of the CN unit as well as ICT from DPA donor to
perylene acceptor, which means that the polarization region
was expanded by ICT and rICT, in the delocalization D−A−D
system; as a result, the larger Stokes shifts in the D−A−
D(CN) was observed.
Solvatochromic Properties. The absorption and emis-
sion behaviors of the Peri−DPA(R)s in different solvents were
investigated to study the solvatochromic effect (Table S3,
Figures S22, and S23). Generally, D−A molecules exhibiting
ICT are more solvated in the excited state than in the ground
state.43,44 As was expected, more significant red shifts were
observed in the emission spectra than in the absorption spectra
(Figures S22 and S23), due to stabilization of the more
polarized emitting state by polar solvents. In particular, the
solvatochromic shift in the emission spectra gradually
increased from EWGs to EDGs, indicating that the Peri−
DPA(R)s well demonstrated the substituent effect. To
quantitatively estimate the experimental dipole moment
changes between the ground and excited states, Stokes shifts
(Δv) of compounds 1a−1e were plotted as a function of
solvent polarity parameters (Δf), according to the Lippert−
Mataga method using eq 1
2
ε − 1
n2 − 1
i
y
j
j
j
j
z
z
z
z
Δν = ν − ν =
+
a
f
hca03
2n2 + 1
2ε + 1
k
{
× (μ − μ )2 + constant
e
g
Δμ2
= 2Δf ×
+ constant
hca03
(1)
where μe − μg (Δμ) is the difference between the dipole
moments in the excited and ground states, c is the speed of
light, h is Planck’s constant, and a0 is the radius of the Onsager
cavity around the fluorophore. The dielectric constants (ε)
(1.9 n-hexane, 2.02 cyclohexane, 2.38 toluene, 7.6 THF, 9.1
CH2Cl2, and 37.5 CH3CN) and the refractive indices (n) of
solvents are included in the term Δf, which is known as
orientation polarizability. Onsager radii, obtained using
B3LYP/6-31G, were considered to be half the average size
for 1a−1e, that is, 16.0, 14.6, 14.4, 15.6, and 16.2 Å,
respectively. Using the slopes in eq 1, increments in dipole
moment changes (Δμ) for 1a−1e were estimated to be 11.6,
16.8, 17.0, 21.9, and 26.7 D, respectively. Table S4 shows the
D
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
values of the ground-state dipole moment (μg) obtained by the
DFT method for energy-minimized structures. These were >0
due to the asymmetries of these compounds (7.0 D for 1a, 1.8
D for 1b, 0.2 D for 1c, 0.4 D for 1d, and 0.4 D for 1e). From
ground-state dipole moments (μg) and dipole moment changes
(Δμ), excited-state dipole moments (μg) were calculated to be
18.6 D for 1a, 18.6 D for 1b, 17.2 D for 1c, 22.3 D for 1d, and
27.2 D for 1e. As EWGs and EDGs in the D−A system are
substituted, μg and μe values became large. The largest μg value
was the CN-substituted 1a, and the largest μe value was the
OMe-substituted 1e. In particular, 1a substituted with strong
EWGs showed the largest μg value among the Peri−DPA(R)s.
However, μe was relatively small and this led to the smallest
Δμ value for 1a. As was observed for the D−A system, the μg
and μe values of the D−A−D system were affected by the
electron push−pull substituent effect and showed the same
trend as values of the D−A system. As shown in Table S5, for
CN-substituted compounds, the μg and μe values were
relatively large for substituent series in the D−A−D system.
Due to the molecular symmetry of the D−A−D system, the μg
value was close to 0, and thus, the relatively large μe value
affected the Δμ value. D−A and D−A−D systems with the
same substituents were compared (Tables S4 and S5), and it
was found that the μg, μe, and Δμ values of the D−A system
were mostly greater than those of the D−A−D system.
However, for CN-substituted compounds, the μe and Δμ
values of the D−A−D system were larger than the D−A
system. For the CN-substituted D−A−D system, expansion of
the polarization region by ICT and rICT and the more
expanded polarization region due to an increase in donor
subunits increased μe and Δμ values in the D−A−D system
more than those in the D−A system.
slope tendency observed for D−A−D(CN) showed notable
ICT properties, which distinguished it from other D−A−Ds.
More specifically, for D−A−D(CN), we suggest the additional
rICT property from the arylamine to the CN unit, along with
the ICT property common to all D−A−D series. Of these two
ICT properties, rICT, which was observed only in D−A−
D(CN), was ascribed to the strong electron-withdrawing effect
of the CN unit within DPA substituents. Considering the area
where rICT occurs, D−A(CN) with the same DPA substituent
could also cause rICT like D−A−D(CN). Based on the above
results, it is unclear whether D−A(CN) and D−A−D(CN)
have identical ICT origins.
Femtosecond Transient Absorption (fs-TA) Measure-
ments. To determine whether ICT origins differed for D−
A(CN) and D−A−D(CN) and between D−A and D−A−D
systems containing other functional groups, femtosecond
transient absorption (fs-TA) measurements were performed
in CH2Cl2 using laser excitation at 350 nm. The TA spectra
exhibited a strong excited-state absorption (ESA) band at
600−800 nm and a negative band at 460−550 nm (Figures 4
As shown in Figures 3 and S24, the Lippert−Mataga plot for
the D−A system showed a linear correlation with solvent
Figure 4. Transient absorption spectra of D−A(CN) and D−A−
D(CN) in CH2Cl2 solution. The excitation wavelength was 350 nm.
Inset: decay profiles were monitored at selected wavelengths.
and S28), and spectral shapes were not changed at different
time delays (Figure S26). Imran et al.39 reported that the
strong positive ESA band in the range 600−750 nm is
attributed to the S1 → Sn transition of perylene and the
negative band at ∼440 nm corresponds to the ground-state
bleaching (GSB) and the stimulated emission (SE) of
perylene. Based on the steady-state spectroscopic result, the
negative TA band in the range 460−550 nm is attributed to the
GSA and SE, and the strong positive TA bands in the 600−800
nm region are attributed to the ICT state than to the S1 → Sn
transition for all perylene-based D−A and D−A−D systems
including D−A(CN) and D−A−D(CN). The transient
absorption spectra between D−A and D−A−D systems are
qualitatively similar, suggesting that D−A−D system, including
D−A−D(CN), indirectly can behave as a D−A system due to
the symmetry breaking in the excited state (Figure S28).45,46
For fs-TA spectra of longer wavelength (600−800 nm), D−A
and D−A−D systems were divided into a broad, intense band
at 600−750 nm and a shoulder band at 750−800 nm. The
broad TA band at 600−750 nm showed a spectral shift by
substituents with a larger shift interval for the D−A system
than for the D−A−D system (Figure S28), due to the large
polarization of the asymmetric system. In addition, the weak
TA band at 750−800 nm was also affected by substituents, and
Figure 3. Lippert−Mataga plots for 1a−1e in different solvents: 1, n-
hexane; 2, cyclohexane; 3, toluene; 4, THF; 5, CH2Cl2; 6, CH3CN.
polarity and followed a substituent effect on its slope. The
slope of the fitting line from EWGs to EDGs increased steadily
in proportion to (Δμ)2 in the order 1a < 1b < 1c < 1d < 1e,
which resulted in an effective ICT control. In contrast, in the
D−A−D system, the Lippert−Mataga plot was not entirely
consistent with the substituent effect (Figure S25), due to the
relatively large Δμ value of D−A−D(CN). In addition,
comparing D−A(CN) and D−A−D(CN) a discrepancy in
the slope tendencies of Lippert−Mataga plots indicated that
the ICT properties of these CN-substituted compounds
depend on subunit combinations. In particular, the exceptional
E
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
intensity changes by substituents were greater for the D−A
system than for the D−A−D system (Figure S28). In
particular, unlike that observed for other substituents, both
D−A(CN) and D−A−D(CN) exhibited a distinctive TA band
at 750−800 nm (Figure 4). Based on TA spectral comparisons,
we believe that the emission origin of D−A(CN) and D−A−
D(CN) differed from that of other members of the D−A and
D−A−D series.
Decay profiles were analyzed to investigate the excited-state
kinetics of D−A and D−A−D. As was expected, on a
picosecond time scale, similar decay patterns were observed
for the respective systems (inset in Figure S28), except for
those containing the CN unit (Figure S27). D−A(CN) and
D−A−D(CN) were observed with a long time scale (≈5 ns)
for a clear comparison between the two (inset in Figure 4).
Measured on a long time scale, the time profile of D−A−
D(CN) monitored at 695 nm was fitted as the lifetime of 3.75
0.06 ns, and the time profile of D−A(CN) monitored at 716
Figure 5. Schematic potential curves for D−A and D−A−D systems.
pink line: D−A(CN) and D−A−D(CN); black line: D−A(F−OMe)
and D−A−D(F−OMe).
nm was fitted as the lifetime of 3.74
0.07 ns. This
consistency between the TA spectra of D−A(CN) and D−A−
D(CN) was attributed to similar ICT properties. On the other
hand, at 772 nm, new TA peaks decayed with a lifetime of 2.90
0.3 and 3.98 0.1 ns for D−A−D(CN) and D−A(CN),
respectively. These decay times were different from that
observed at ESA maxima wavelengths of 695 and 716 nm,
respectively. This means that for both D−A(CN) and D−A−
D(CN), the overall TA spectral behavior appeared to be mixed
with an emission origin other than the ICT mentioned above.
In a previous report on D−A−D(CN), its unique transition
origin was demonstrated using steady-state spectroscopic and
calculation results, and this uniqueness was assumed to be due
to rICT from the arylamine to the CN unit. Although the
steady-state spectroscopic results of D−A(CN) and D−A−
D(CN) did not delineate with certainty whether the two CN-
substituted compounds had the same or different origins,
transient absorption measurements clearly indicated that
emission origins were similar. In conclusion, unlike members
of the D−A and D−A−D series with one ICT origin, both D−
A(CN) and D−A−D(CN) had in common a transition mix of
ICT and rICT.
In combination with the above-mentioned results, the ICT
emission origin for perylene based D−A and D−A−D systems
can be summarized as follows as shown in Figure 5. All D−A
and D−A−D systems upon ultrafast excitation indicated
dynamics involved in transition from Franck−Condon (FC)
state to ICT state, where the ICT occur from arylamine to
perylene unit. The observed TA spectra showed the red-shift as
the EDG ability increased, which means that this ICT state was
stabilized, and it is in agreement with the electron push−pull
substituent effect. In particular, by comparing the TA spectra
and decay profile, we suggest that both D−A(CN) and D−A−
D(CN) mixed with an emission origin from arylamine to CN
unit, different from ICT mentioned above, as well as the ICT.
Therefore, perylene-based D−A and D−A−D systems
indicated the ICT process was in good agreement with the
electron push−pull substituent effect, but D−A(CN) and D−
A−D(CN) occurred the additional emission origin by strong
EWG ability of CN unit. As a result, F−OMe unit of D−A and
D−A−D system showed one ICT origin from DPA donor to
perylene acceptor, while CN unit of D−A and D−A−D system
showed mixture of the emission origin, ICT and rICT (from
arylamine to CN unit).
Electrochemical Properties. Cyclic voltammetry (CV) of
the Peri−DPA series was performed in 1 mM CH2Cl2 solution
containing n-Bu4NClO4 (0.1 M) as a supporting electrolyte to
investigate redox properties and energy levels (Figure S29).
HOMO/LUMO energy levels were determined using
oxidation onset potentials and electronic spectral data
(summarized in Table 2 and Figure S30). All five compounds
showed only one reversible oxidation wave and no reduction
wave. The first oxidation onset potentials (Eoonxset) were
determined to be 0.89 V for 1a, 0.74 V for 1b, 0.72 V for
1c, 0.65 V for 1d, and 0.58 V for 1e, which can be explained by
the stabilities of the cationic species generated from the Peri−
DPA unit. As electron-donating propensities of the DPA
substituents increased, the Peri−DPA unit is first oxidized and
its unstable oxidized species is compensated by the effective π-
conjugation. Furthermore, the introduction of a substituent
influences the experimental and calculated EHOMO and ELUMO
values, which was −5.53
0.17 and −3.08
0.02 for
experimental values and −4.87 0.48 and −2.05 0.38 for
calculated values. As shown in Figure S31, EHOMO values were
more affected by the electron push−pull substituent effect than
the ELUMO values. In particular, the experimentally estimated
ELUMO values were similar for all five compounds due to the
same perylene acceptor, which indicated that the electron
acceptor was largely unaffected by the electron donor at the
LUMO level.
The optical band gaps (Eogpt) from absorption edges were
determined to be 2.60, 2.48, 2.47, 2.39, and 2.31 eV for 1a−1e,
respectively, that is, band gaps widened on increasing the
electron-withdrawing character of substituents. The theoretical
band gaps (Egcal) from DFT calculations for 1a−1e were
determined to be 2.92, 2.82, 2.82, 2.77, and 2.67 eV,
respectively and this trend agreed well with optical band
gaps. For the D−A−D molecules previously reported, a similar
trend to the D−A system was observed between band gaps and
substituent effects. In addition, when comparing the effects of
one and two donors with the same substituent type, one-donor
systems had larger optical and theoretical energy band gaps
(Figure S32). This indicates that in both D−A and D−A−D
systems, electronic communication occurs between the DPA
nitrogen and perylene and is affected by the substituents
through the π-conjunction system of the phenyl linked to the
F
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
Table 2. Energy Band-Gap Properties of 1a−1e
experimental
calculated
a
b
c
c
compd
HOMO (eV)
LUMO (eV)
Eogpt (eV)
HOMO (eV)
LUMO (eV)
Ecgal (eV)
d
e
1a
1b
1c
1d
1e
−5.70 (−6.00 )
−3.10
−3.06
−3.06
−3.07
−3.08
2.60
2.48
2.47
2.39
2.31
−5.35
−4.87
−4.78
−4.68
−4.53
−2.43
−2.05
−1.96
−1.91
−1.86
d
2.92
2.82
2.82
2.77
2.67
d
e
−5.54 (−5.85 )
d
e
−5.53 (−5.83 )
d
e
−5.46 (−5.76 )
d
e
−5.39 (−5.69 )
LUMO (eV) = −e(EHOMO + Egopt). Obtained by the DFT calculation. Estimated assuming that the
a
ox
b
c
E
HOMO (eV) = −e(E
+ 4.8)
.
E
onset
HOMO energy of ferrocene lies 4.80 eV below the vacuum level.47 Estimated assuming that the HOMO energy of ferrocene is −5.11 eV in
e
CH2Cl2.48
Figure 6. Frontier orbital distributions (HOMO − 1, HOMO, LUMO, LUMO + 1) of 1a−1e calculated by the DFT using the B3LYP function
and 6-31G(d,p) basis.
N atom. These results show that band gaps are predictable
based on considering the substituent effect and subunit
composition.
Considering the results of TD-DFT calculations (B3LYP/6-
31G) shown in Figures S38−S42 and Tables S12−S16, all five
compounds demonstrated a major charge-transfer transition
from an amino-delocalized HOMO to a perylene-localized
LUMO, due to efficient HOMO/LUMO overlap on the
perylene core. In addition, transitions from the diarylamino-
delocalized H-1 to the perylene-localized LUMO and from the
amino-delocalized HOMO to the diarylperylene-delocalized L
+ 1 were minor charge-transfer transitions. In contrast to the
other compounds, for 1a, the strong electron-withdrawing
ability of the CN unit facilitated the transition from the
HOMO to L + 1 at ca 412 nm rather than from H-1 to the
LUMO. In our previous study on the D−A−D system, we
reported that additional rICT, a minor transition from the
HOMO to L + 1 at ca 372 nm can occur within the DPA
moiety due to the strong electron-withdrawing character of the
CN unit. Likewise, in the D−A system, a similar phenomenon
was observed, which means that in D−A−D and D−A systems,
strong electron-withdrawal and vulnerable HOMO/L + 1
overlap cause a weak electronic coupling between the donor
and acceptor. In addition, the D−A−D system, which
possesses an added donor subunit as compared with the D−
A system, is relatively favorable for rICT due to enhanced ICT
in the two donor components. Summarizing, for both D−A−D
and D−A systems, ICT is mainly controlled by the electronic
transition from HOMOs to LUMOs, and the rICT seen only
in the CN-substituted compounds was observed in both D−A
and D−A−D systems.
Density Functional Theory (DFT). To gain deeper
understanding of the geometric and electronic properties of
the target molecules, density functional theory (DFT)
calculations and time-dependent DFT (TD-DFT) calculations
were conducted using the Gaussian 16 program. Geometric
optimization was performed in the gas phase at the B3LYP/6-
31G(d,p) level. The B3LYP DFT method provided sufficiently
reliable qualitative insights rather than quantitative analysis of
experimental results. The frontier orbital distributions of 1a−
1e estimated from DFT calculations are depicted in Figure 6.
HOMO-1, HOMO, and LUMO+1 molecular orbitals, but not
LUMOs, were influenced by substituents. HOMO orbitals of
1a−1e were delocalized over perylene and DPA moieties, and
distribution in the two phenyls of DPA increased on increasing
electron donation. The H-1 orbitals of 1a−1e were delocalized
over DPA and perylene moieties, which is expanded from DPA
moiety to perylene moiety as the electron-donating character
of substituents increases. However, LUMO orbitals of 1a−1e
were localized on the perylene moiety, whereas L + 1 orbital
distribution decreased in the two phenyl groups of DPA and
increased in the perylene, as the electron-donating propensity
increases. Unlike the other four compounds, the molecular
orbitals of 1a were highly localized on either perylene or DPA,
which is attributed to the weak electronic coupling between
donor and acceptor.
G
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
(silica gel, CH2Cl2/hexane mixture eluent). Finally, 3-(p-(R)-
diphenylamino)perylene compounds were further purified by using
hexane hot filter washing.
CONCLUSIONS
■
Along the line of the perylene-based donor−acceptor−donor
(D−A−D) system, the donor−acceptor (D−A) system, Peri−
DPA(R) (1a−1e), were designed and synthesized by
modifying only a subunit combination under the same
substituent conditions. To investigate the influence of the
electron push−pull substituent effect on ICT control, the
photophysical and electrochemical properties of the five Peri−
DPA(R)s were examined and compared to those of the D−A−
D system. Steady-state spectroscopic results of Peri−DPA(R)s
showed predictable ICT properties in that the D−A system
was in good agreement with the substituent effect. In
particular, Lippert−Mataga plots for the D−A system
demonstrated systematic ICT control by substituents, which
differed from that observed for the D−A−D system.
Comparisons of the D−A and D−A−D systems for each
substituent suggested that different slope tendencies in
Lippert−Mataga plots of D−A(CN) and D−A−D(CN) were
caused by different emission origins. However, considering that
both have the same subunits required for ICT and rICT
formation, the same emission origin for D−A(CN) and D−A−
D(CN) was also suggested. The femtosecond transient
absorption (fs-TA) spectroscopic results confirmed that
emissions of D−A(CN) and D−A−D(CN) were from the
same origin based on ICT and rICT. In addition, DFT
calculations supported the notion that ICT and rICT exist only
for CN-substituted compounds regardless of subunit combi-
nation. The results presented in this study are helpful in
designing D−A molecules for efficient ICT and understanding
its fundamental structure−property relationship.
Peri−DPA(CN) (1a) 3-(N,N-Bis(4′-cyanophenyl)amino)perylene.
1
Yield: 0.42 g, 64%, orange powder. Eluent (DCM/hexane = 2:1). H
NMR (500 MHz, CDCl3, ppm) δ 8.26−8.22 (m, 4H), 7.79−7.77 (m,
2H), 7.57−7.53 (m, 7H), 7.45 (t, J = 7.5 Hz, 1H), 7.36 (d, J = 8.0 Hz,
1H), 7.18 (d, J = 9.0 Hz, 4H). 13C{1H} NMR (125 MHz, CDCl3,
ppm) δ 150.0 (2C), 139.7, 134.6, 133.7 (4C), 132.5, 132.0, 131.8,
130.6, 130.6, 130.5, 130.2, 128.8, 128.6, 128.5, 128.4, 128.1, 126.8,
126.7, 122.4, 121.5 (4C), 121.1, 121.0 (2C), 120.6, 119.0, 105.6
(2C). anal. calcd for C34H19N3: C, 86.97; H, 4.08; N, 8.95. found: C,
86.74; H, 4.11; N, 8.87. GC-MS (m/z) calcd: 469.53; found: 469.2
Peri−DPA(F) (1b) 3-(N,N-Bis(4′-fluorophenyl)amino)perylene.
Yield: 0.43 g, 68%, yellow powder. Eluent (DCM/hexane = 1:4).
1H NMR (500 MHz, CDCl3, ppm) δ 8.12−8.05 (m, 4H), 7.68 (d, J =
8.0 Hz, 1H), 7.61 (t, J = 8.0 Hz, 2H), 7.40 (td, J = 8.0, 2.5 Hz, 2H),
7.29 (t, J = 7.5 Hz, 1H), 7.15 (d, J = 8.0 Hz, 1H), 6.94−6.90 (m, 4H),
6.84 (t, J = 8.0 Hz, 4H). 13C{1H} NMR (125 MHz, CDCl3, ppm) δ
159.2, 157.3, 144.7 (2C), 143.3, 134.7, 131.9, 131.8, 131.1, 130.9,
130.5, 129.4, 128.5, 128.1, 127.8, 127.0 (2C), 126.7, 123.9, 123.4
(4C), 120.8, 120.7, 120.5, 120.2, 116.1 (4C), 115.9. anal. calcd for
C32H19F2N: C, 84.38; H, 4.20; N, 3.08. found: C, 84.40; H, 4.11; N,
3.18. GC-MS (m/z) calcd: 455.50; found: 455.1
Peri−DPA(H) (1c) 3-(N,N-Diphenylamino)perylene. Yield: 0.42 g,
1
72%, yellow powder. Eluent (DCM/hexane = 1:4). H NMR (500
MHz, CDCl3, ppm) δ 8.11−8.06 (m, 4H), 7.72 (d, J = 8.0 Hz, 1H),
7.72 (dd, J = 5.5, 2.5 Hz, 2H), 7.40 (t, J = 7.5 Hz, 2H), 7.27 (t, J = 8.0
Hz, 1H), 7.23 (d, J = 8.0 Hz, 1H), 7.14 (t, J = 8.0 Hz, 4H), 7.01 (d, J
= 8.5 Hz, 4H), 6.88 (t, J = 7.0 Hz, 2H). 13C{1H} NMR (125 MHz,
CDCl3, ppm) δ 148.2 (2C), 143.3, 134.7, 132.2, 131.8, 131.2, 131.0,
130.4, 129.5, 129.4, 129.2 (4C), 128.5, 127.9, 127.8, 127.7, 127.0
(2C), 126.6, 124.2, 122.0 (4C), 121.9, 120.9, 120.6, 120.4, 120.2.
anal. calcd for C32H21N: C, 91.62; H, 5.05; N, 3.34. found: C, 91.60;
H, 5.12; N, 3.28. GC-MS (m/z) calcd: 419.52; found: 419.2
EXPERIMENTAL SECTION
Peri−DPA(Me) (1d) 3-(N,N-Bis(4′-methylphenyl)amino)-
■
perylene. Yield: 0.41 g, 66%, yellow powder. Eluent (DCM/hexane
General. Based on the standard Schlenk techniques, all of the
synthesis experimental procedures were performed under a dry argon
condition. Reagents and solvents were purchased from commercial
sources and used as received without further purification, unless
otherwise stated. All reactions were monitored with thin-layer
chromatography (TLC) using commercial TLC plates (Merck Co.).
Silica gel column chromatography was performed on silica gel 60 G
(230−400 mesh ASTM, Merck Co.). The synthesized compounds
were characterized by 1H NMR or 13C{1H} NMR and elemental
analysis. The 1H and proton-decoupled 13C spectra were recorded on
a Bruker500 spectrometer operating at 500 and 125 MHz,
respectively, and all proton and carbon chemical shifts were measured
relative to the internal residual chloroform (99.5% CDCl3) from the
lock solvent. The elemental analyses (C, H, N, O) were performed
using a Thermo Fisher Scientific Flash 2000 series analyzer. The GC-
MS analysis was performed using a highly sensitive gas chromato-
graph/mass selective detector spectrometer (Agilent, 7890B-5977B
GC/MSD). The 3-bromoperylene49 and p-(R)-diphenylamine50 were
prepared based on the previously published method. The crystal
structure was determined by single-crystal X-ray diffractometer at the
Western Seoul Center of Korea Basic Science Institute.
Synthesis of Peri−DPA(R) (1). A mixture of 3-bromoperylene
(0.46 g, 1.39 mmol), p-(R)-diphenylamine (1.46 mmol, R: CN (2a),
F (2b), H (2c), Me (2d), and OMe (2e)), sodium tert-butoxide (0.96
g, 10 mmol), Xantphos (0.04 g, 5 mol %), Pd2(dba)3 (0.06 g, 5 mol
%) in toluene (30 mL) was refluxed under an argon atmosphere at
110 °C via a heating mantle overnight. After the reaction mixture was
cooled to room temperature (RT), deionized water (40 mL) was
poured, and organic layer was separated using a separating funnel.
The water layer was washed using methylene chloride (×3) for the
extracted remaining organic residue. After combining all of the
organic solvents, the organic layer was dried over anhydrous MgSO4
and then filtered off. The solvent was removed under reduced
pressure, and the residue was purified with column chromatography
1
= 1:4). H NMR (500 MHz, CDCl3, ppm) δ 8.10−8.04 (m, 4H),
7.73 (d, J = 8.0 Hz, 1H), 7.59 (t, J = 8.0 Hz, 2H), 7.39 (td, J = 8.0, 2.5
Hz, 2H), 7.27 (t, J = 8.0 Hz, 1H), 7.18 (d, J = 8.0 Hz, 1H), 6.94 (d, J
= 8.0 Hz, 4H), 6.88 (d, J = 8.5 Hz, 4H), 2.21 (s, 6H). 13C{1H} NMR
(125 MHz, CDCl3, ppm) δ 146.2 (2C), 143.9, 134.7, 132.1, 131.7,
131.3, 131.2 (2C), 131.1, 130.4, 129.8 (4C), 128.9, 128.5, 127.9,
127.5, 127.3, 126.8, 126.6, 126.6, 124.4, 122.1 (4C), 120.9, 120.6,
120.3, 120.0, 20.7 (2C). anal. calcd for C34H25N: C, 91.24; H, 5.63;
N, 3.13. found: C, 91.74; H, 5.21; N, 3.05. GC-MS (m/z) calcd:
447.57; found: 447.3
Peri−DPA(OMe) (1e) 3-(N,N-Bis(4′-methoxyphenyl)amino)-
perylene. Yield: 0.45 g, 68%, orange powder. Eluent (DCM/hexane
1
= 1:1). H NMR (500 MHz, CDCl3, ppm) δ 8.20−8.13 (m, 4H),
7.85 (d, J = 8.5 Hz, 1H), 7.69 (t, J = 8.5 Hz, 2H), 7.49 (td, J = 8.0, 3.5
Hz, 2H), 7.36 (t, J = 8.0 Hz, 1H), 7.23 (d, J = 8.0 Hz, 1H), 7.00 (d, J
= 9.0 Hz, 4H), 6.80 (d, J = 9.0 Hz, 4H), 3.79 (s, 6H). 13C{1H} NMR
(125 MHz, CDCl3, ppm) δ 154.8 (2C), 144.4, 142.6, 134.7, 131.7,
131.6, 131.3, 131.2, 130.4, 128.5, 128.4, 127.8, 127.4, 126.6 (2C),
126.6, 126.5, 126.4, 124.5, 123.6 (4C), 120.9, 120.5, 120.2, 119.9,
114.6 (4C), 55.5 (2C). anal. calcd for C34H25NO2: C, 85.15; H, 5.25;
N, 2.92. found: C, 85.34; H, 5.16; N, 2.88. GC-MS (m/z) calcd:
479.57; found: 479.2
Preparation of Single Crystal 1a. For the crystallization of
compound 1a, a vacuum-dried pure sample of 1a was taken in a vial
and dissolved in 1:2 dichloromethane/hexane mixed solvent. Slow
evaporation of the solvent at room temperature for one month yielded
the orange needle-shaped crystal. Then the crystals were picked up
from the vial and a single-crystal XRD study was performed.
X-ray Crystal Structure Analysis. The preliminary examination
and data collection were performed using a Bruker SMART CCD
detector system single-crystal X-ray diffractometer equipped with a
sealed-tube X-ray source (50 kV × 30 mA) using graphite-
monochromated Mo Kα radiation (λ = 0.71073 Å). Preliminary
H
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
unit cell constants were determined using a set of 45 narrow-frame
(0.3° in ω) scans. The double-pass method of scanning was used to
exclude noise. Collected frames were integrated using an orientation
matrix determined from narrow-frame scans. The SMART software
package was used for data collection, and SAINT was used for frame
integration.51 Final cell constants were determined by global
refinement of the xyz centroids of reflections harvested from the
entire data set. Structure solution and refinement were carried out
using the SHELXTL-PLUS software package.52
Spectroscopic Measurements. The UV−vis absorption spectra
were recorded using a Sinco Mega-2100 spectrophotometer in the
dual-beam mode, and the fluorescence emission measurements were
carried out using a Shimadzu fluorometer (RF-6000) with a
wavelength resolution of ∼1 nm. Fluorescence lifetimes were
measured by PicoQuant FluoTime 200 that takes advantage of the
time-correlated single photon counting method. A pulsed diode laser
operated at 20 MHz repetition rate was used as the excitation source.
The FWHM of a laser pulse was typically 45 ps, and the instrument
response function was ∼190 ps when the Hamamatzu photomultiplier
tube (H5783-01) was used. The emission quantum yields (ΦPL) were
calculated using William’s comparative method for samples of five
different concentrations of (1−10) μM, using 9,10-diphenylanthra-
cene (ΦPL = 0.95, ethanol) as a reference standard.53
The sub-picosecond time-resolved absorption spectra were
collected using a pump−probe transient absorption spectroscopy
system (Ultrafast Systems, Helios). The pump light was generated
using a regenerative amplified titanium sapphire laser system (Spectra
Physics, Spitfire Ace, 1 kHz) pumped by a diode-pumped Q-switched
laser (Spectra Physics, Empower). The seed pulse was generated
using a titanium sapphire laser (Spectra Physics, MaiTai SP). The
pulses (350 nm) generated from an optical parametric amplifier
(Spectra Physics, TOPAS prime) were used as the excitation pulse.
Further, a white light continuum pulse, which was generated by
focusing the residual of the fundamental light to a thin Sapphire
crystal after the controlled optical delay, was used as a probe beam
and directed to the sample cell with 2.0 mm of the optical path and
detected with a CCD detector installed in the absorption
spectroscope. The pump pulse was chopped by the mechanical
chopper synchronized to one-half of the laser repetition rate, resulting
in a pair of the spectra with and without the pump, from which the
absorption change induced by the pump pulse was estimated.
Cyclic Voltammetry (CV). A CH Instruments 701D potentiostat
was used for electrochemical measurements, and cyclic voltammetry
(CV) was performed in an electrolytic solution prepared using 1 mM
of electroactive compounds and 0.1 M tetrabutyl ammonium
perchlorate (NBu4ClO4) in deoxygenated dichloromethane. A three-
electrode configuration, glassy carbon, platinum wire, and saturated
calomel electrode (SCE), were used as working, counter, and
reference electrodes, respectively.
Density Functional Theory Calculations. Density functional
theory (DFT) calculations were performed using the Gaussian’16
software package. Full geometry optimizations in their ground state
were performed using the B3LYP functional and the 6-31G(d,p) basis
set for all atoms. The excitation energies and oscillator strengths for
the lowest 100 singlet−singlet transitions at the optimized geometry
in the ground state were obtained in time-dependent DFT (TD-DFT)
calculations using the same basis set and functional as for the ground
state. All isodensity plots of the frontier orbitals were visualized by
Chem3D Ultra and GaussView software. More detailed DFT/TD-
DFT calculation results for 3-(p-(R)-diphenylamino)perylenes are
described in the SI.
ties of D−A and D−A−D systems; absorption, and
emission spectra in various solvents and in the solid
state, emission lifetime profile; Lippert−Mataga plots
and dipole moment values of D−A and D−A−D
systems; femtosecond transient absorption spectroscopic
data; CV, HOMO and LUMO energy levels and
Hammett plots; comparison of the energy band gap of
D−A and D−A−D systems; and DFT/TD-DFT
calculation results; X-ray crystallographic data of
compound 1a (PDF)
Accession Codes
CCDC 2042435 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
AUTHOR INFORMATION
Corresponding Authors
■
Dae Won Cho − Department of Chemistry, Yeungnam
University, Gyeongsan, Gyeongbuk 38541, Republic of
Korea; orcid.org/0000-0001-8000-8413;
Email: dwcho00@yu.ac.kr
Kyung-Ryang Wee − Department of Chemistry and Institute
of Natural Science, Daegu University, Gyeongsan 38453,
Republic of Korea; orcid.org/0000-0002-9923-8902;
Email: krwee@daegu.ac.kr
Authors
Mina Ahn − Department of Chemistry and Institute of Natural
Science, Daegu University, Gyeongsan 38453, Republic of
Korea
Min-Ji Kim − Department of Chemistry and Institute of
Natural Science, Daegu University, Gyeongsan 38453,
Republic of Korea
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.joc.0c02149
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research was supported by the Basic Science Research
Program through the National Research Foundation of Korea
(NRF-2020R1C1C1009007) and Korea Basic Science In-
stitute (National Research Facilities and Equipment Center)
grant, funded by the Ministry of Education
(2020R1A6C103A028).
REFERENCES
■
(1) Bullock, J. E.; Carmieli, R.; Mickley, S. M.; Vura-Weis, J.;
Wasielewski, M. R. Photoinitiated charge transport through π-stacked
electron conduits in supramolecular ordered assemblies of donor−
acceptor triads. J. Am. Chem. Soc. 2009, 131, 11919−11929.
(2) Urbani, M.; Ohkubo, K.; Islam, D. S.; Fukuzumi, S.; Langa, F.
Photoinduced Energy and Electron Transfer in Phenylethynyl-
Bridged Zinc Porphyrin−Oligothienylenevinylene−C60 Ensembles.
Chem. - Eur. J. 2012, 18, 7473−7485.
(3) Guldi, D. M. Putting a positive spin on molecular bridges. Angew.
Chem., Int. Ed. 2010, 49, 7844−7846.
(4) Fan, C.; Zhu, L.; Liu, T.; Jiang, B.; Ma, D.; Qin, J.; Yang, C.
Using an organic molecule with low triplet energy as a host in a highly
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.joc.0c02149.
■
sı
NMR spectra; GC−MS data; X-ray crystallography;
absorption spectra of DPA donor, perylene acceptor, and
D−A compounds; comparison of photophysical proper-
I
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
efficient blue electrophosphorescent device. Angew. Chem. 2014, 126,
2179−2183.
Derivatives: Influence of Substitution Pattern on Their Photophysical
Properties. J. Org. Chem. 2017, 82, 5111−5121.
̈
(23) Uebe, M.; Sakamaki, D.; Ito, A. Electronic and Photophysical
Properties of 9,10-Anthrylene-Bridged B-π-N Donor-Acceptor Mol-
ecules with Solid-State Emission in the Yellow to Red Region.
ChemPlusChem 2019, 84, 1305−1313.
(5) Mishra, A.; Fischer, M. K.; Bauerle, P. Metal-free organic dyes
for dye-sensitized solar cells: From structure: Property relationships to
design rules. Angew. Chem., Int. Ed. 2009, 48, 2474−2499.
(6) Bottari, G.; de la Torre, G.; Guldi, D. M.; Torres, T. Covalent
and noncovalent phthalocyanine−carbon nanostructure systems:
synthesis, photoinduced electron transfer, and application to
molecular photovoltaics. Chem. Rev. 2010, 110, 6768−6816.
(7) Chen, C.-H.; Ting, H.-C.; Li, Y.-Z.; Lo, Y.-C.; Sher, P.-H.; Wang,
J.-K.; Chiu, T.-L.; Lin, C.-F.; Hsu, I.-S.; Lee, J.-H.; Liu, S.-W.; Wong,
K.-T. New D−A−A-Configured Small-Molecule Donors for High-
Efficiency Vacuum-Processed Organic Photovoltaics under Ambient
Light. ACS Appl. Mater. Interfaces 2019, 11, 8337−8349.
(8) Gautam, P.; Misra, R.; Siddiqui, S. A.; Sharma, G. D.
Unsymmetrical Donor−Acceptor−Acceptor−π−Donor Type Benzo-
thiadiazole-Based Small Molecule for a Solution Processed Bulk
Heterojunction Organic Solar Cell. ACS Appl. Mater. Interfaces 2015,
7, 10283−10292.
(9) Wee, K.-R.; Sherman, B. D.; Brennaman, M. K.; Sheridan, M. V.;
Nayak, A.; Alibabaei, L.; Meyer, T. J. An aqueous, organic dye
derivatized SnO2/TiO2 core/shell photoanode. J. Mater. Chem. A
2016, 4, 2969−2975.
(10) Hancock, J. M.; Gifford, A. P.; Zhu, Y.; Lou, Y.; Jenekhe, S. A.
n-Type conjugated oligoquinoline and oligoquinoxaline with
triphenylamine endgroups: efficient ambipolar light emitters for
device applications. Chem. Mater. 2006, 18, 4924−4932.
(11) Zhu, M.; Yang, C. Blue fluorescent emitters: design tactics and
applications in organic light-emitting diodes. Chem. Soc. Rev 2013, 42,
4963−4976.
(12) Sharma, C. P.; Gupta, N. M.; Singh, J.; Yadav, R. A. K.; Dubey,
D. K.; Rawat, K. S.; Jha, A. K.; Jou, J.-H.; Goel, A. Synthesis of
Solution-Processable Donor−Acceptor Pyranone Dyads for White
Organic Light-Emitting Devices. J. Org. Chem. 2019, 84, 7674−7684.
(13) Slama-Schwok, A.; Blanchard-Desce, M.; Lehn, J. Intra-
molecular charge transfer in donor-acceptor molecules. J. Phys.
Chem. A. 1990, 94, 3894−3902.
(14) Kulkarni, A. P.; Kong, X.; Jenekhe, S. A. High-Performance
Organic Light-Emitting Diodes Based on Intramolecular Charge-
Transfer Emission from Donor−Acceptor Molecules: Significance of
Electron-Donor Strength and Molecular Geometry. Adv. Funct. Mater.
2006, 16, 1057−1066.
(15) Chen, R.; Zhao, G.; Yang, X.; Jiang, X.; Liu, J.; Tian, H.; Gao,
Y.; Liu, X.; Han, K.; Sun, M.; Sun, L. Photoinduced intramolecular
charge-transfer state in thiophene-π-conjugated donor−acceptor
molecules. J. Mol. Struct. 2008, 876, 102−109.
(16) Panja, S. K.; Dwivedi, N.; Saha, S. Tuning the intramolecular
charge transfer (ICT) process in push−pull systems: effect of nitro
groups. RSC Adv. 2016, 6, 105786−105794.
(24) Ahn, M.; Kim, M.-J.; Wee, K.-R. Electron Push−Pull Effects in
3,9-Bis(p-(R)-diphenylamino) perylene and Constraint on Emission
Color Tuning. J. Org. Chem. 2019, 84, 12050−12057.
(25) Liu, C.-L.; Zheng, C.-J.; Liu, X.-K.; Chen, Z.; Yang, J.-P.; Li, F.;
Ou, X.-M.; Zhang, X.-H. Multifunctional terpyridine/diphenylamine
derivatives as highly efficient blue fluorescent emitters and red
phosphorescent hosts. J. Mater. Chem. C 2015, 3, 1068−1076.
(26) Jhulki, S.; Moorthy, J. N. Small molecular hole-transporting
materials (HTMs) in organic light-emitting diodes (OLEDs):
structural diversity and classification. J. Mater. Chem. C 2018, 6,
8280−8325.
(27) Lee, H. L.; Lee, K. H.; Lee, J. Y. Indoloindole as a new building
block of a hole transport type host for stable operation in
phosphorescent organic light-emitting diodes. J. Mater. Chem. C
2019, 7, 5988−5994.
(28) Zhang, Y.; Zheng, Y.; Wang, B.; Ran, H.; Wang, X.; Hu, J.-Y.;
Wang, Q. Diphenylamine/triazine hybrids as bipolar hosts for
phosphorescent organic light-emitting diodes. J. Mater. Chem. C
2020, 8, 4461−4468.
(29) Avlasevich, Y.; Li, C.; Mu
core-enlarged perylene dyes. J. Mater. Chem. 2010, 20, 3814−3826.
(30) Chen, L.; Li, C.; Mullen, K. Beyond perylene diimides:
̈
llen, K. Synthesis and applications of
̈
synthesis, assembly and function of higher rylene chromophores. J.
Mater. Chem. C 2014, 2, 1938−1956.
(31) Dawson, W. R.; Windsor, M. W. Fluorescence yields of
aromatic compounds. J. Phys. Chem. B. 1968, 72, 3251−3260.
(32) Icil, H.; Arslan, E. Synthesis and spectroscopic properties of
highly pure perylene fluorescent dyes. Spectrosc. Lett. 2001, 34, 355−
363.
(33) Camerman, A. T.; Trotter, J. The crystal and molecular
structure of perylene. Proc. R. Soc. London, Ser. A 1964, 279, 129−146.
́
́
(34) Lin, M.-J.; Jimenez, A. J.; Burschka, C.; Wurthner, F. Bay-
̈
substituted perylene bisimide dye with an undistorted planar scaffold
and outstanding solid state fluorescence properties. Chem. Commun.
2012, 48, 12050−12052.
(35) Liu, X.; Xu, Z.; Cole, J. M. Molecular design of uv−vis
absorption and emission properties in organic fluorophores: toward
larger bathochromic shifts, enhanced molar extinction coefficients,
and greater stokes shifts. J. Phys. Chem. C 2013, 117, 16584−16595.
(36) Toguchi, S.; Morioka, Y.; Ishikawa, H.; Oda, A.; Hasegawa, E.
Novel red organic electroluminescent materials including perylene
moiety. Synth. Met. 2000, 111−112, 57−61.
́
̈
(37) Torres, E.; Bogel-Lukasik, R.; Berberan-Santos, M. N.; Hofle,
S.; Colsmann, A.; Brites, M. J. N, N′-Diaryl-perylene-3, 9-diamine
derivatives: synthesis, characterization and electroluminescence
properties. RSC Adv. 2016, 6, 107180−107188.
̈
(17) Zophel, L.; Beckmann, D.; Enkelmann, V.; Chercka, D.; Rieger,
llen, K. Asymmetric pyrene derivatives for organic field-effect
R.; Mu
̈
transistors. Chem. Commun. 2011, 47, 6960−6962.
(38) Li, Y.; Zhu, R.; Wang, J.; Li, Z. S.; Xu, N.; Zhang, J.; Wang, P.
N-Annulated Perylene-Based Hole Transporters for Perovskite Solar
Cells: The Significant Influence of Lateral Substituents. ChemSu-
sChem 2018, 11, 672−680.
(18) Lu, X.; Fan, S.; Wu, J.; Jia, X.; Wang, Z.-S.; Zhou, G.
Controlling the charge transfer in D−A−D chromophores based on
pyrazine derivatives. J. Org. Chem. 2014, 79, 6480−6489.
́
(19) Delmond, S.; Letard, J.-F.; Lapouyade, R.; Rettig, W.
(39) Imran, M.; Sukhanov, A. A.; Wang, Z.; Karatay, A.; Zhao, J.;
Mahmood, Z.; Elmali, A.; Voronkova, V. K.; Hayvali, M.; Xing, Y. H.;
Weber, S. Electronic coupling and spin−orbit charge-transfer
intersystem crossing in phenothiazine−perylene compact electron
donor/acceptor dyads. J. Phys. Chem. C 2019, 123, 7010−7024.
Photoinduced intramolecular charge transfer in planar vs. twisted
donor-acceptor terphenyls. J. Photochem. Photobiol., A 1997, 105,
135−148.
(20) Ma, W.; Wu, Y.; Han, J.; Gu, D.; Gan, F. Large three-photon
absorption and intramolecular charge transfer of the bis-donor
fluorene-based molecules. J. Mol. Struct. 2005, 752, 9−13.
(21) Kim, M.-J.; Ahn, M.; Shim, J. H.; Wee, K.-R. Terphenyl
backbone-based donor−π−acceptor dyads: geometric isomer effects
on intramolecular charge transfer. Phys. Chem. Chem. Phys. 2020, 22,
3370−3378.
(40) Merz, J.; Steffen, A.; Nitsch, J.; Fink, J.; Schurger, C. B.;
̈
Friedrich, A.; Krummenacher, I.; Braunschweig, H.; Moos, M.; Mims,
D.; Lambert, C.; Marder, T. B. Synthesis, photophysical and
electronic properties of tetra-donor-or acceptor-substituted ortho-
perylenes displaying four reversible oxidations or reductions. Chem.
Sci. 2019, 10, 7516−7534.
(22) Kurata, R.; Ito, A.; Gon, M.; Tanaka, K.; Chujo, Y.
Diarylamino- and Diarylboryl-Substituted Donor−Acceptor Pyrene
(41) Merz, J.; Dietrich, L.; Nitsch, J.; Krummenacher, I.;
Braunschweig, H.; Moos, M.; Mims, D.; Lambert, C.; Marder, T. B.
J
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX

The Journal of Organic Chemistry
pubs.acs.org/joc
Article
Synthesis, Photophysical and Electronic Properties of Mono-, Di-, Tri-
Amino-Substituted Ortho-Perylenes, and Comparison to the Tetra-
Substituted Derivative. Chem. - Eur. J. 2020, 12050−12059.
(42) Dong, H.; Wang, C.; Hu, W. High performance organic
semiconductors for field-effect transistors. Chem. Commun. 2010, 46,
5211−5222.
(43) Detert, H.; Schmitt, V. Quadrupolar donor−acceptor
substituted oligo (phenylenevinylene) ssynthesis and solvato-
chromism of the fluorescence. J. Phys. Org. Chem. 2004, 17, 1051−
1056.
(44) Clarke, T. M.; Gordon, K. C.; Kwok, W. M.; Phillips, D. L.;
Officer, D. L. Tuning from π,π* to charge-transfer excited states in
styryl-substituted terthiophenes:An ultrafast and steady-state emission
study. J. Phys. Chem. A 2006, 110, 7696−7702.
(45) Dereka, B.; Rosspeintner, A.; Li, Z.; Liska, R.; Vauthey, E.
Direct visualization of excited-state symmetry breaking using ultrafast
time-resolved infrared spectroscopy. J. Am. Chem. Soc. 2016, 138,
4643−4649.
(46) Beckwith, J. S.; Rosspeintner, A.; Licari, G.; Lunzer, M.; Holzer,
̈
B.; Frohlich, J.; Vauthey, E. Specific monitoring of excited-state
symmetry breaking by femtosecond broadband fluorescence upcon-
version spectroscopy. J. Phys. Chem. Lett. 2017, 8, 5878−5883.
(47) Pommerehne, J.; Vestweber, H.; Guss, W.; Mahrt, R. F.;
̈
Bassler, H.; Porsch, M.; Daub, J. Efficient two layer leds on a polymer
blend basis. Adv. Mater. 1995, 7, 551−554.
(48) Connelly, N. G.; Geiger, W. E. Chemical redox agents for
organometallic chemistry. Chem. Rev. 1996, 96, 877−910.
́
(49) Torres, E.; Berberan-Santos, M. N.; Brites, M. J. Synthesis,
photophysical and electrochemical properties of perylene dyes. Dyes
Pigm. 2015, 112, 298−304.
(50) Tlili, A.; Monnier, F.; Taillefer, M. Selective one-pot synthesis
of symmetrical and unsymmetrical di-and triarylamines with a
ligandless copper catalytic system. Chem. Commun. 2012, 48, 6408−
6410.
(51) SMART and SAINT; Bruker Analytical X-ray Division:
Madison, WI, 2002.
(52) Sheldrick, G. M. SHELXTL-PLUS Software Package; Bruker
Analytical X-ray Division: Madison, WI, 2002.
(53) Morris, J. V.; Mahaney, M. A.; Huber, J. R. Fluorescence
quantum yield determinations. 9,10-Diphenylanthracene as a
reference standard in different solvents. J. Phys. Chem. C. 1976, 80,
969−974.
K
https://dx.doi.org/10.1021/acs.joc.0c02149
J. Org. Chem. XXXX, XXX, XXX−XXX