Diaryl-substituted perylene bis(imides): Synthesis, separation, characterization and comparison of electrochemical and optical properties of 1,7-and 1,6-regioisomer

Article abstract of DOI:10.1002/ejoc.201101825

A series of diaryl-substituted perylene bis(imides) (PBIs) containing electron-donating and-withdrawing aryl groups in the bay region (1-, 6-, 7-and/or 12-positions of the perylene core) were synthesized by Suzuki coupling reaction. The corresponding regioisomers, namely, 1,7-and 1,6-regioisomer, were separated from the mixture by conventional column chromatography without any need of recrystallization. All the individual regioisomers were fully characterized by ¹H NMR and HRMS spectroscopy. The compounds were studied by optical spectroscopy and electrochemical techniques. The optical and electrochemical properties of 1,7-regioisomer are slightly different from the 1,6-regioisomer of the respective diaryl-PBI. Significant redshift and broadening of the absorption and emission maxima were observed in all synthesized PBIs depending upon the electronic nature of the attached aryl group. This is very first time such large series of 1,6- diarylperylenetetracarboxydiimides with their corresponding 1,7-regioisomers were synthesized, separated, characterized and studied in detail. 1,7-and 1,6-rsegioisomers of a series of diarylperylenetetracarboxydiimide derivatives were synthesized, separated, and electrochemical and spectroscopic studies have been done in detail. The regioisomers are chromatographically separable and fully characterized by ¹H NMR spectroscopy.

Full text of DOI:10.1002/ejoc.201101825

FULL PAPER
DOI: 10.1002/ejoc.201101825
Diaryl-Substituted Perylene Bis(imides): Synthesis, Separation,
Characterization and Comparison of Electrochemical and Optical Properties of
1,7- and 1,6-Regioisomer
Somnath Dey,*[a] Alexander Efimov,[a] and Helge Lemmetyinen[a]
Keywords: Conducting materials / Semiconductors / Regioisomers / Cross-coupling / Voltammetry / Perylene
A series of diaryl-substituted perylene bis(imides) (PBIs) con-
taining electron-donating and -withdrawing aryl groups in
the bay region (1-, 6-, 7- and/or 12-positions of the perylene
core) were synthesized by Suzuki coupling reaction. The cor-
responding regioisomers, namely, 1,7- and 1,6-regioisomer,
were separated from the mixture by conventional column
chromatography without any need of recrystallization. All
the individual regioisomers were fully characterized by 1H
NMR and HRMS spectroscopy. The compounds were studied
by optical spectroscopy and electrochemical techniques. The
optical and electrochemical properties of 1,7-regioisomer are
slightly different from the 1,6-regioisomer of the respective
diaryl-PBI. Significant redshift and broadening of the absorp-
tion and emission maxima were observed in all synthesized
PBIs depending upon the electronic nature of the attached
aryl group. This is very first time such large series of 1,6-
diarylperylenetetracarboxydiimides with their corresponding
1,7-regioisomers were synthesized, separated, characterized
and studied in detail.
as xerographic photoreceptors in electro-photography[11]
and as liquid crystalline material,[12] generated lot of inter-
est in perylene chemistry.
Introduction
Organic photovoltaics based on small molecules received
considerable attention in last few decades.[1] Even though,
modern inorganic solar cells dominate most of the commer-
cial market, thin-film based organic semiconductors be-
come attractive alternative owing to their low cost pro-
duction, ease of fabrication, intergration into devices and
large scale manufacturing.[2] Organic semiconductors have
also been applied in e.g. organic light-emitting diodes
(OLEDs) in modern electronic devices, memories and field-
effect transistors.[3]
Perylene-3:4,9:10-tetracarboxydiimides [“perylene bis-
(imides)”, PBIs] are a unique class of molecules with re-
markable optical, electronic and physical properties. High
molar absorption coefficient, fluorescence quantum yield,
high electron affinity and charge carrier mobility, ease of
functionalization in addition to excellent chemical, thermal
and photo stabilities establish PBIs as one of the most
promising n-type organic semiconductor.[4] Potential appli-
cations in photovoltaic cells[5] and OLEDs,[6] as organic
field-effect transistors,[7] photo-sensitizers,[8] fluorescent
dyes for single molecule spectroscopy[9] and bio-imaging,[10]
Since, the parent PBA [perylenetetracarboxylic bis(an-
hydride)] possess a very narrow absorption band (ca.
520 nm) and is insoluble in all organic solvents, the tuning
of optical properties and improving the solubility of PBIs
are the two major challenges before organic chemists. The
broader absorption range is desirable because it helps to
capture more photons for optical devices and higher solu-
bility improves the processability. Tuning of the properties
can be achieved by introducing functional groups to the
anhydride or to the bay region of perylene bis(anhydride)
(Figure 1). The introduction of substituents in the anhydride
region improves the solubility of PBIs in common organic
solvents but has negligible impact on electronic and optical
properties, because the nodes of HOMO–LUMO lie at the
long molecular axis; hence, substituents are not expected
to induce any electronic interaction between the attached
chromophore and the perylene core.[4b,13] This makes intro-
duction of functional groups in the bay region more attract-
ive as it not only modifies the electronic and optical proper-
ties but also improves the solubility.
The landmark merging of two concepts was first re-
ported by Böhm et al. in 1997,[14] as they selectively di-
brominated perylene bis(anhydride) and with subsequent
imidation, which led to more soluble functional PBIs. This
method has been used extensively by other over last decade
for synthesizing bis(substituted) PBIs without any suspi-
cion. Würthner et al. in 2004, however, demonstrated that
the current bromination method produces two regioiso-
[a] Department of Chemistry and Bioengineering, Tampere
University of Technology,
P. O. Box 541, 33101 Tampere, Finland
Fax: +358-3-31152108
E-mail: somnath.dey@tut.fi
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101825.
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S. Dey, A. Efimov, H. Lemmetyinen
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ED/EW groups is well known strategy to modify the
HOMO–LUMO energy levels of the compound and thus,
it’s the electronic and optical properties,[4d,19] which were
compared for the 1,7- and 1,6-regioisomers of diaryl-PBIs
in detail. We were able to isolate the individual regioisomers
by conventional chromatographic method without any need
of recrystallization. This work is the first time as such wide
series of 1,6-diaryl-PBIs were synthesized, separated and
their optical and electrochemical properties were compared
with their respective 1,7-regioisomer.
Results and Discussion
Synthesis, Separation and Characterization
The syntheses of 1,7- and 1,6-diaryl-PBIs are shown in
Schemes 1 and 2. The synthesis of dibromo-PBI 2 was done
according to the literature procedure (Scheme 1).[18,20]
Figure 1. Chemical structure of perylenetetracarboxylic bis(an-
hydride) and different functional regions of perylene.
mers, namely, 1,7-dibromo-PBA and 1,6-dibromo-PBA in
(3:1) ratio. Würthner and co-workers also developed a
method (repeated recrystallization) to separate 1,7-re-
gioisomer from the mixture after imidation.[15] Unfortu-
nately, recrystallization method is cumbersome and protrac-
ted (6–10 weeks for pure 1,7-regioisomer). Moreover, it is
also not possible to obtain pure 1,6-dibromo-PBI by this
method and consequently, the 1,6-bis(substituted) PBIs. On
this basis, they postulated that previously reported 1,7-
bis(substituted) PBIs might also be contaminated with 1,6-
bis(substituted) PBIs. However, even after the clear demon-
stration, most of the research groups still neglected the pres-
ence of 1,6-regioisomer[16] but there are also some notable
exceptions.[17] Recently, we showed that 1,7- and 1,6-
bis(substituted) PBIs can have very different and interesting
optical and electrochemical properties depending upon the
electronic nature of the substituents attached.[18]
In this paper, we report the detailed synthesis, separation
and characterization, as well as some optical and electro-
chemical properties of a series of bis(substituted) PBIs hav-
ing electron-donating (ED) and electron-withdrawing (EW)
aryl groups attached to the bay region of perylene (Fig-
ure 2). The Suzuki coupling reaction was employed to at-
tach aryl groups to the perylene core. The introduction of Scheme 1. Synthesis of dibromo-PBI 2.
Figure 2. Structures of synthesized 1,7- and 1,6-diaryl-PBIs.
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Diaryl-Substituted Perylene Bis(imides)
0.2 ppm). Unequivocal assignments of individual regioiso-
mers were performed on the basis of the signal of methylene
protons (in α-position to imide group) which appear ca.
4.2 ppm. For 1,7-regioisomers both the methylene groups
are equivalent and appear as one triplet whereas the 1,6-
regioisomers produce two distinct triplets for the same two
methylene groups (Figure 3). Hence, we can unambiguously
characterize 1,7- and 1,6-regioisomers by 300 MHz 1H
NMR spectroscopy. One notable exception is a pair of
DMA-PBI (4a, 4b) isomers. Both 1,6- and 1,7- compound
showed identical signal of α-imide methylene protons,
which made the assignment more difficult. However, the
difference in chemical shifts for their perylene core signals
is very similar to that of 1,6- and 1,7-Ph-PBI pair. Namely,
the perylene proton signals of the faster isomer are evi-
dently shifted to the lower field by 0.05 ppm. Taking into
account this difference and the relative mobility of the two
DMA-PBI isomers, we identified the faster fraction as 1,6-
DMA-PBI, and the slower one as 1,7-DMA-PBI. It should
be also mentioned that, on the contrary to the present hy-
pothesis for the need of bulky bay-substituents for facile
chromatographic separation, we did not use any excessively
bulky aryls in the present synthetic work.[18,21]
Scheme 2. Syntheses of diaryl-PBIs 3–7.
It should be mentioned that, 2 is a regioisomeric mixture
of dibromo-PBI, namely, 1,7- and 1,6-dibromo-PBI in 3:1
ratio. Unfortunately, regioisomers of dibromo-PBI could
not be separated using normal phase silica gel chromatog-
raphy and used without further purification as a mixture of
regioisomers. The syntheses of ED/EW diaryl-substituted
PBIs 3–7 were done according to Scheme 2. Suzuki cou-
pling reactions were employed between dibromo-PBI 2 and
aryl-pinacolborane in a toluene/water biphasic system by
using PdCl2(dppf)·CH2Cl2 (8 mol-%) catalyst [dppf = 1,1Ј-
bis(diphenylphosphanyl)ferrocene] producing PBI deriva-
tives 3–7. Aryl-pinacolboranes were synthesized by the sim-
ilar method reported earlier.[19a] Even though, presence of
steric hindrance in perylene bay region is expected, all the
Suzuki couplings gave high yields (75–80%). The regioiso-
mers were separated by normal silica gel (very slow run-
ning, 2–3 d) column chromatography. Three fractions were
generally collected, the first one and the last one contained
pure regioisomers and the middle one had a mixture of the
two. Detailed separation methods are described in Exp. Sec-
tion.
1
Figure 3. H NMR spectra of 1,7-and 1,6-Ph-PBIs.
Albeit, it is possible to separate regioisomers by chroma-
tographic methods, but needs repeated columns and final
yield of individual regioisomers were only 20–35%, with
large amount of regioisomeric mixtures.
It should be noted that, even though, dibromo-PBI 2 has
1,7- and 1,6-regioisomers in 3:1 ratio, almost all the Suzuki
coupling reaction produce 1,7- and 1,6-regioisomer in a ra-
1
tio of Ͼ 2:1 (from H NMR analysis of regioisomeric mix-
ture). This small regio-specificity might be due to less steric
interaction between perylene bay-hydrogen atoms and aryl
moieties for the 1,6-regioisomer than the 1,7-regioisomer.[22]
Steady-State Absorption Measurements
The pure regioisomers were consequently fully charac-
terized by 300 MHz 1H NMR and HRMS spectroscopy.
The spectroscopic parameters of all synthesized PBI de-
Both 1,7- and 1,6-regioisomers show characteristic one sin- rivatives are summarized in Table 1. All the measurements
glet, and two doublets for perylene core protons. Significant were done in 1–2 μm chloroform solution to prevent strong
difference in the chemical shift values were not observed (Ͻ perylene π-π aggregation.
Eur. J. Org. Chem. 2012, 2367–2374
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Table 1. Optical properties, absorption maxima (λmax), molar ex-
tinction coefficient (ε), emission maxima (λF), fluorescence quan-
tum yield (ΦF) and fluorescence life times (τ), of 1,7- and 1,6-re-
gioisomers of diaryl-PBIs.
λmax
[nm]
ε
λF
[nm]
ΦF
τ [ns]
[mol–1 cm–1]
dioctyl-PBI 525
78600
42200
35400
535
609
617
–
1
4.32
7.25
6.82
–
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
555
551
0.61
0.56
–
481, 647 38100, 22000
470, 631 29400, 17300
–
–
–
561
557
544
538
546
541
31700
26600
33300
31900
31600
33800
634
641
586
592
591
600
0.37
0.35
0.48
0.43
0.46
0.49
8.26
7.53
6.32
6.14
6.21
6.53
Figure 4. UV/Vis absorption spectra of Ph-PBI pair in chloroform.
Steady-State Emission and Life Time Measurements
All the synthesized compounds except DMA-PBI (4a,
4b) pair are fluorescent and have broad emission in the 550–
800 nm range as listed in Table 1. The fluorescence quan-
tum yields ΦF were determined using fluorescein (in 0.1 n
NaOH, quantum yield 0.92) as a standard.[12c] All the PBI
derivatives have high fluorescence with quantum yields
(0.35–0.61). Strong steric perylene core twisting by di-tBu-
phenyl unit results in considerable lower fluorescence quan-
tum yield (0.35 for 5b) compared to less steric crowding
diaryl-PBIs. Fluorescence of Ph-PBI pair in chloroform is
shown in Figure 5 and others in Supporting Information.
Their emissions are almost mirror image of their S0 – S1
absorption bands with Stokes shift of ca. 60 nm. Re-
gioisomeric pair of PBIs all show slight different fluores-
cence spectra. For 1,7-Ph-PBI the emission maxima is
609 nm and for 1,6-Ph-PBI is 617 nm. The DMA-PBI (4a,
4b) pair does not show any fluorescence which mainly re-
sults from more charge-transfer in the excited state of the
molecule.
Depending upon the nature of aryl substituents attached,
the solutions of compounds exhibit various colours from
dark red (DTB-PBI 5) to deep green (DMA-PBI 4). The
absorption spectra of all PBIs are dominated by character-
istic π–π* transitions. The strongest absorption can be as-
signed to S0 – S1 electronic transitions while the shoulder
band can be assigned to S0 – S2 transitions. In comparison
to unsubstituted PBI (dioctyl-PBI), the absorption spectra
show a significant bathochromic shift of 13–122 nm along
with considerable band broadening. These results could be
attributed to the inductive effect impose by the aryl substit-
uents on the perylene core. The negative inductive effect
of 4-nitrophenyl or 4-cyanophenyl unit on compound 6–7
results in small red shift in their absorption spectra com-
pared to other PBI derivatives.
The absorption spectra of 1,7- and 1,6-regioisomers of
Ph-PBIs are shown in Figure 4 and others in the Support-
ing Information. For both the regioisomers the absorption
spectra resemble each other but characteristic S0 – S1 elec-
tronic transition appear at 555 nm for 1,7-regioisomer 3a
and at 551 nm for 1,6-regioisomer 3b. It can be clearly note
that, all regioisomeric pair has slightly different absorption
spectra. Moreover, molar extinction coefficient is signifi-
cantly lower for 1,6-regioisomer in comparison to 1,7-re-
gioisomer of Ph-PBI. This trend is universal with notable
exception for BN-PBI (7a, 7b) pair (Table 1). It is also inter-
esting to note that, DMA-PBI (4a, 4b) pair shows broad
absorption spectrum (see Supporting Information, Fig-
ure S1) covering almost whole visible solar spectrum with
unusual dual absorption band, one peak at ca. 475 nm and
another one at ca. 640 nm. While the first one can be attrib-
uted to charge transfer electronic transition from electron-
rich dimethylaniline unit to electron-deficient perylene core
while the later one usually is a π–π* transition.[17a] Small
charge-transfer band can also be observed for DTB-PBI
Figure 5. Fluorescence spectra of Ph-PBI pair in chloroform.
For the fluorescence lifetime measurements, the solutions
(5a, 5b) pair (see Figure S1). From absorption spectra of of all the PBIs were excited at 483 nm and emission time
all PBI derivatives it can be stated that diaryl-PBIs have profiles were collected at corresponding emission maxi-
significantly broader absorption in the visible solar spec- mum. By fitting the experimental data, it is clear that all
trum which is definitely useful for building optical devices PBIs display mainly mono-exponential decay with time
involving these derivatives.
constants (τ) in the range of 6–9 ns depending upon the
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Diaryl-Substituted Perylene Bis(imides)
aryl substituents. The fluorescence life times of all PBIs are
summarized in Table 1. Fastest fluorescence decay was ob-
served for PBI with EW aryls (for 6b, τ = 6.14 ns), whereas
PBI with ED aryl showed the slowest decay (for 5a, τ =
8.26 ns). Hence, it can said that fluorescence lifetimes are
longer for the PBI with larger Stokes shifts. It can be also
said that, fluorescence life times of 1,7-regioisomers were
longer than 1,6-regioisomer of the respective diaryl-PBI.
Conclusions
We have synthesized, separated and characterized an ar-
ray of 1,7- and 1,6-regiosiomers of diaryl-PBIs. The re-
gioisomers are isolated using conventional normal phase
silica gel column chromatography. The presented 1,6-diaryl-
PBIs had previously been unreported in literature and have
interesting optical and electrochemical properties. The de-
scribed separation method of regioisomers is useful alterna-
tive as it does not involve prolonged repetitive recrystalli-
zation. The individual regioisomers were unambiguously
identified by 1H NMR spectroscopy by observing the chem-
ical shift of four methylene protons next to imide nitrogens
and by the chemical shifts of perylene core protons.
We also compared the photophysical properties of the
regioisomers by spectroscopic and electrochemical tech-
niques. Obtained results allow us to conclude that, 1,7- and
1,6-regioisomers of same diaryl-PBI possess slightly dif-
ferent electrochemical and spectroscopic properties which
might be important while designing a system for optoelec-
tronic applications. We hope these results will further moti-
vate chemists to build functional PBIs using cross-coupling
reactions.
All the synthesized PBI derivatives show broad absorp-
tion in visible solar spectrum. Specifically those absorbing
in the red-to-NIR region could be useful to convert solar
energy to electricity. Solid state properties and solar cell ex-
periments involving these PBIs are also under investigation
and the data will be published in due course as a separate
manuscript. Moreover, molecular orbital (MO) calculation
might be helpful to explain the apparent similar photophys-
ical properties of 1,7- and 1,6-regioisomers and we continue
to investigate these in near future.
Electrochemical Studies
Besides their excellent absorption and high fluorescence
quantum yields, PBIs have also have useful electrochemical
properties. The electrochemical properties of all diaryl-PBIs
were determined by differential pulse voltammetry (DPV)
method in benzonitrile containing 0.1 m TBABF4 as sup-
porting electrolyte. As the PBIs generally considered as n-
type organic semiconductor, i.e. electron acceptor, hence,
only the reduction potentials and calculated HOMO and
LUMO energy levels (see the calculation details in the Exp.
Section) are shown in Table 2. All the PBIs undergo suc-
cessive reversible reductions to corresponding radical
anions and dianions. The reduction potentials of all the PBI
derivatives are comparable to the parent PBI (dioctyl-PBI,
E1red = –1.02 V). The reduction potentials can be directly
correlated to the electronic nature of the aryl (ED/EW)
groups attached to the perylene bay region. The reduction
potentials of ED diaryl-PBIs are higher (E1red = –1.15 V for
4a) than EW diaryl-PBIs (E1red = –0.91 V for 6a), which
indicate that upon reduction PBI radical anion is more
stable for ED diaryl-PBIs. Their high reduction potentials
indicate that they all are essentially strong electron ac-
ceptor. It is also evident that all the corresponding re-
gioisomeric pair has slightly different reduction potentials,
which suggests that this property can be accentuated when
designing materials for optical devices.
Experimental Section
General: All the reagents utilized in the synthesis were purchased
from Sigma–Aldrich Co. and used as received. The solvents were of
HPLC grade and purchased from VWR and used without further
purification. The sorbents for column chromatography (Silica 60,
Silica 100), TLC plates (aluminium sheets coated with silica gel
60F254) were purchased from Merck. NMR spectra were recorded
with Varian Mercury 300 MHz spectrometer in CDCl3 at room
temperature. All chemical shifts are quoted relative to TMS (δ =
0.0 ppm); δ values are given in ppm and J values in Hz. Mass spec-
tra were measured with Waters LCT Premier XE ESI-TOF
benchtop mass spectrometer.
Table 2. Reduction potentials (given in V vs. Fc/Fc+) and calculated
HOMO–LUMO energy levels of 1,7- and 1,6-regioisomers of di-
aryl-PBIs.
E1red
[V]
E2red
[V]
HOMO
[eV]
LUMO Eopt
g
[eV]
[eV]
Dioctyl-PBI
–1.02
–1.08
–1.11
–1.15
–1.13
–1.12
–1.14
–0.91
–0.94
–0.94
–0.96
–1.23
–1.28
–1.32
–1.35
–1.33
–1.32
–1.35
–1.18
–1.20
–1.19
–1.21
–6.12
–5.99
–5.95
–5.56
–5.63
–5.89
–5.88
–6.16
–6.16
–6.12
–6.13
–3.78
–3.72
–3.69
–3.65
–3.67
–3.68
–3.66
–3.89
–3.86
–3.86
–3.84
2.36
2.33
2.25
1.91
1.96
2.21
2.22
2.27
2.30
2.26
2.29
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
If not otherwise indicated, all the spectroscopic measurements were
carried out at room temperature. The absorption spectra were re-
corded with Shimadzu UV-2501PC spectrophotometer and the
fluorescence spectra using a Fluorolog-3 (SPEX Inc.) Fluorimeter.
The emission spectra were corrected using a correction function
supplied by the manufacturer. Optical densities at excitation wave-
lengths were maintained at around 0.1 to avoid re-absorption.
Fluorescence decays of the samples in the nanosecond and sub-
nanosecond time scales were measured using a time-correlated sin-
gle photon counting (TCSPC) system (PicoQuant GmbH) con-
sisting of PicoHarp 300 controller and PDL 800-B driver. Fluores-
cence decays were measured at the wave-length of emission maxi-
mum. The signals were detected with a micro channel plate photo-
The calculated HOMO energy levels are in the range of
–6.16 to –5.56 eV and LUMO energy levels are –3.89 to
–3.65 eV, which means all the synthesized PBI derivatives
are suitable for electron-transport materials in optoelec-
tronic devices.
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S. Dey, A. Efimov, H. Lemmetyinen
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multiplier tube (Hamamatsu R2809U). The time resolution of the
TCSPC measurements was 110 ps for 483 nm excitation wavelength
(fwhm of the instrument response function).
2 H), 8.10 (d, J = 8.6 Hz, 2 H), 7.71 (d, J = 8.6 Hz, 2 H), 7.50 (M,
10 H), 4.18 (t, 4 H), 1.71 (t, 4 H), 1.22–1.35 (m, 20 H), 0.86 (dis-
torted triplet, 6 H) ppm. 13C NMR (75 MHz, CDCl3, TMS): δ =
163.6, 163.5, 142.2, 141.2, 135.4, 134.9, 132.6, 130.4, 129.5, 129.3,
129.4, 129.8, 127.7, 122.4, 122, 32, 29.6, 29.45, 28.4, 27.4, 22.9,
14.3 ppm. HRMS ESI-TOF: m/z for C52H51N2O4 [M + H]+ calcd.
767.3849; found 767.3848.
Differential pulse voltammetry was carried out at room tempera-
ture under high-purity nitrogen flow and recorded using a po-
tentiostat (Iviumstat Compactstat IEC 61326 Standard) controlled
by an IBM computer with the software Iviumsoft (Version 1.752)
in three-electrode single-compartment cell consisting platinum in
glass as working electrode, Ag/AgCl as reference electrode and
graphite as counter electrode. Benzonitrile containing 0.1 m
TBABF4 was used as solvent. The measurements were done under
continuous flow of nitrogen. All potentials were internally refer-
enced to the Fc/Fc+ couple. Under these conditions the Fc/Fc+
couple potential was determined to be +0.48 V and the data have
been recalculated to the reference. The measurements were carried
out in both directions: toward the positive and negative potential.
The peak reduction and oxidation potentials were calculated as an
average of the two scans. HOMO and LUMO energy levels were
calculated by using commonly used procedure,[19b] through the
equation as follows:
1,6-Diphenyl-N,NЈ-dioctyl-3:4,9:10-perylenetetracarboxydiimides
1
(3b): Yield 25%. H NMR (CDCl3, 300 MHz, TMS): δ = 8.62 (s,
2 H), 8.13 (d, J = 8.6 Hz, 2 H), 7.77 (d, J = 8.6 Hz, 2 H), 7.50 (M,
10 H), 4.23 (t, 2 H), 4.11 (t, 2 H), 1.71 (t, 4 H), 1.22–1.35 (m, 20
H), 0.85 (distorted triplet, 6 H) ppm. 13C NMR (75 MHz, CDCl3,
TMS): δ = 163.7, 163.4, 141.9, 141.4, 135.4, 134.8, 132.5, 130.3,
129.8, 129.3, 129.6, 129, 127.9, 122.4, 122, 32.4, 29.6, 29.3, 28.3,
27.4, 23, 14.5 ppm. HRMS ESI-TOF: m/z for C52H51N2O4 [M +
H]+ calcd. 767.3849; found 767.3874.
The synthesis and crude product separation of product 4–7 were
done by the same method described for product 3.
1,7- and 1,6-Bis[4-(dimethylamino)phenyl]-N,NЈ-dioctyl-3:4,9:10-
perylenetetracarboxydiimides (4): Reaction time 24 h. Yield 76%.
The regioisomers were separated by slow silica gel (silica 60) col-
umn chromatography over 3 d using dichloromethane/ethanol,
200:1 (Rf = 0.6) as eluent. From the 1H NMR analysis, first fraction
was identified as 1,6-regioisomer, second fraction was mixture of
regioisomers while the last fraction was 1,7-regioisomer.
LUMO = –(E1red + 4.8) eV, in which E1red is the reduction poten-
tials referenced against ferrocene.
HOMO = (LUMO – Eoptg) eV, in which optical band gap, Eopt
=
g
1240/λmax
.
The value for Fc with respect to the zero vacuum level is estimated
as –4.8 eV, determined from –4.6 eV for the standard electrode po-
tential E° of normal hydrogen electrode (NHE) on the zero vacuum
level, and 0.2 V for Fc vs. NHE.
1,7-Bis[4-(dimethylamino)phenyl]-N,NЈ-dioctyl-3:4,9:10-perylenetetra-
carboxydiimide (4a): Yield 28 %. 1H NMR (CDCl3, 300 MHz,
TMS): δ = 8.58 (s, 2 H), 8.13 (d, J = 8.1 Hz, 2 H), 7.94 (d, J =
7.95 Hz, 2 H), 7.39 (d, J = 7.4 Hz, 4 H), 6.76 (d, J = 6.8 Hz, 4 H),
4.18 (t, 4 H), 3.06 (s, 6 H), 1.72 (t, 4 H), 1.22–1.35 (m, 20 H), 0.87
(distorted triplet, 6 H) ppm. 13C NMR (75 MHz, CDCl3, TMS): δ
= 162.9, 162.8, 147.1, 146.5, 145.1, 140.4, 135.3, 134.6, 132.4, 130.1,
129.7, 129.5, 129.4, 129.2, 129.1, 128.8, 128.0, 124.7, 123.7, 123.6,
123.3, 121.8, 121.4, 29.5, 24.4, 24.3, 14.3 ppm. HRMS ESI-TOF:
m/z for C52H51N2O4 [M + H]+ calcd. 853.4693; found 853.4689.
1H NMR, 13C NMR, UV-visible absorption spectra and emission
spectra are included in the Supporting Information.
1,7- and 1,6-Diphenyl-N,NЈ-dioctyl-3:4,9:10-perylenetetracarboxydi-
imides (3): 200 mg (0.26 mmol) of dibromo-N,NЈ-dioctyl-3:4,9:10-
perylenetetracarboxydiimides 2, 116 mg (0.57 mmol) of phenylpin-
acolborane, 15 mg (0.052 mmol) of tetrabutylammonium chloride
and 17 mg (0.021 mmol) of PdCl2(dppf)·CH2Cl2 were added to a
two-phase mixture of toluene (12 mL) and aqueous 1 m potassium
carbonate solution (12 mL). The reaction mixture was intensively
stirred under argon atmosphere at 90 °C for 16 h. The organic layer
was separated and the aqueous phase was extracted with toluene
(3ϫ20 mL). The organic layers were combined, washed with water
(2ϫ20 mL) and dried with anhydrous sodium sulfate and evapo-
rated in vacuo. TLC of the reaction mixture often shows 2–4 spots.
Starting material 2, disubstituted-PBI, very small amount of mono-
substituted and debrominated-PBI can be observed. But, the
amount of other side products are small in most of the cases and
can be easily separated before the isolation of individual regioiso-
mers. The individual regioisomers are generally cannot be distin-
guished by their Rf values.The crude product was purified on silica
60 using chloroform as eluent. First, the orange band was collected
and concentrated by rotary evaporation to afford the product
(159 mg, 81%), which was found to be regioisomeric mixture of
1,7- and 1,6-diphenyl-N,NЈ-dioctyl-3:4,9:10-perylenetetracarboxy-
1,6-Bis[4-(dimethylamino)phenyl]-N,NЈ-dioctyl-3:4,9:10-perylenetetra-
carboxydiimide (4b): Yield 16 %. 1H NMR (CDCl3, 300 MHz,
TMS): δ = 8.63 (s, 2 H), 8.15 (d, J = 8.14 Hz, 2 H), 7.99 (d, J =
8 Hz, 2 H), 7.41 (d, J = 7.4 Hz, 4 H), 6.76 (d, J = 6.8 Hz, 4 H),
4.17 (t, 4 H), 3.07 (s, 6 H), 1.73 (t, 4 H), 1.22–1.35 (m, 20 H), 0.87
(distorted triplet, 6 H) ppm. 13C NMR (75 MHz, CDCl3, TMS): δ
= 163.1, 162.9, 148, 146.6, 145.5, 140.5, 135.3, 134.6, 132.4, 130.2,
129.7, 129.5, 129.4, 129.2, 129, 128.9, 128.0, 124.5, 123.4, 123.6,
123.3, 121.9, 121.4, 29.6, 24.5, 24.2, 14.1 ppm. HRMS ESI-TOF:
m/z for C52H51N2O4 [M + H]+ calcd. 853.4693; found 853.4697.
1,7- and 1,6-Bis(3,5-di-tert-butylphenyl)-N,NЈ-dioctyl-3:4,9:10-per-
ylenetetracarboxydiimides (5): Reaction time 22 h. Yield 76%. The
regioisomers were separated by slow silica gel (silica 60) column
chromatography over 2 d using dichloromethane/hexane, 5:3 (Rf =
0.55) as eluent. From the 1H NMR analysis, first fraction was iden-
tified as 1,6-regioisomer, second fraction was mixture of regioiso-
mers, while the last fraction was 1,7-regioisomer.
1
diimides 3 in a 2:1 ratio (according to H NMR analysis).
1,7-Bis(3,5-di-tert-butylphenyl)-N,NЈ-dioctyl-3:4,9:10-perylenetetra-
carboxydiimide (5a): Yield 32 %. 1H NMR (CDCl3, 300 MHz,
TMS): δ = 8.67 (s, 2 H), 8.09 (d, J = 8.2 Hz, 2 H), 7.75 (d, J =
8.2 Hz, 2 H), 7.55 (t, 2 H), 7.37 (d, J = 1.8 Hz, 4 H), 4.17 (t, 4 H),
1.73 (t, 4 H), 1.38 (s, 36 H), 1.22–1.33 (m, 20 H), 0.87 (distorted
triplet, 6 H) ppm. 13C NMR (75 MHz, CDCl3, TMS): δ = 163.3,
The regioisomers were separated by slow silica gel (silica 60) col-
umn chromatography over 2 d using dichloromethane (Rf = 0.7) as
eluent. The From the 1H NMR analysis, first fraction was iden-
tified as 1,6-regioisomer, second fraction was mixture of regioiso-
mers while the last fraction was 1,7-regioisomer.
1,7-Diphenyl-N,NЈ-dioctyl-3:4,9:10-perylenetetracarboxydiimides 163.2, 145.4, 141.8, 141.3, 135.6, 135.4, 133.1, 130.5, 130.4, 130.3,
1
(3a): Yield 36%. H NMR (CDCl3, 300 MHz, TMS): δ = 8.55 (s,
130.1, 129.5, 129.4, 128.8, 128.7, 128.3, 124.1, 122, 121.9, 29.3,
2372
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 2367–2374

Diaryl-Substituted Perylene Bis(imides)
24.2, 24.1 14.1 ppm. HRMS ESI-TOF: m/z for C52H51N2O4 [M +
112.7, 77.4, 76.8, 76.4, 31.8, 29.5, 29.6, 29.4, 29.3, 29.1, 27.2, 22.6,
14 ppm. HRMS ESI-TOF: m/z for C52H51N2O4 [M + H]+ calcd.
817.3754; found 817.3748.
H]+ calcd. 991.6353; found 991.6374.
1,6-Bis(3,5-di-tert-butylphenyl)-N,NЈ-dioctyl-3:4,9:10-perylenetetra-
carboxydiimide (5b): Yield 17 %. 1H NMR (CDCl3, 300 MHz,
TMS): δ = 8.65 (s, 2 H), 8.08 (d, J = 8.2 Hz, 2 H), 7.70 (d, J =
8.2 Hz, 2 H), 7.52 (t, 2 H), 7.24 (d, J = 1.8 Hz, 4 H), 4.23 (t, 2 H),
4.11 (t, 2 H), 1.73 (t, 4 H), 1.38 (s, 36 H), 1.22–1.33 (m, 20 H), 0.87
(distorted triplet, 6 H) ppm. 13C NMR (75 MHz, CDCl3, TMS): δ
= 163.4, 163.2, 146, 141.9, 141.3, 135.6, 135.4, 133, 130.6, 130.4,
130.3, 130.2, 129.6, 129.4, 128.8, 128.7, 128.3, 124.4, 122.2, 121.9,
29.3, 24.3, 24.2 14.2 ppm. HRMS ESI-TOF: m/z for C52H51N2O4
[M + H]+ calcd. 991.6353; found 991.6381.
Supporting Information (see footnote on the first page of this arti-
cle): Absorption spectra of compounds 4–7, emission spectra of
1
compounds 5–7, H and 13C NMR spectra of compounds 3–7.
Acknowledgments
Financial support of Academy of Finland is greatly acknowledged.
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1
1,7-Bis(4-nitrophenyl)-N,NЈ-dioctyl-3:4,9:10-perylenetetracarboxy-
1
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7.75 (m, 6 H), 4.18 (t, 4 H), 1.72 (t, 4 H), 1.38 (s, 36 H), 1.22–1.33
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130, 129.5, 128.2, 127.3, 123, 121.6, 119.6, 106.6, 31.9, 29.6, 29.5,
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1
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7.75 (m, 6 H), 4.20 (distorted triplet, 4 H), 1.73 (t, 4 H), 1.38 (s,
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Eur. J. Org. Chem. 2012, 2367–2374
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www.eurjoc.org
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Published Online: March 13, 2012
2374
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Eur. J. Org. Chem. 2012, 2367–2374