C-H activation: Making diketopyrrolopyrrole derivatives easily accessible

Article abstract of DOI:10.1039/c2ta01318e

Diketopyrrolopyrrole (DPP) derivatives are an important class of high-performance pigment used in inks, paints, plastics, and organic electronics. Until now, DPP derivatives containing sophisticated aryl units at the DPP core have usually been obtained via Suzuki, Stille, or Negishi cross-coupling reactions, which require organometallic precursors. In this work, a series of DPP-based π-conjugated molecules bearing diverse aryl substituents on the thiophene- or benzene-DPPs were facilely synthesized in moderate to excellent yields through the Pd-catalyzed direct arylation of C-H bonds. The synthetic procedures feature advantages over traditional C-C cross-coupling reactions such as: (1) avoidance of the use of organometallic reagents in the starting materials leading to simpler byproducts and higher atom economy, (2) fewer synthetic steps, (3) higher yields, (4) better compatibility with chemically sensitive functional groups, and (5) simpler catalytic systems free of phosphine ligands. These advantages make the present protocol an ideal and versatile strategy for the synthesis of DPP derivatives, especially for structurally complicated DPPs that may possess chemically sensitive functionalities. The optical and electrochemical properties of the synthesized DPPs (17 compounds) were systematically investigated using UV-vis spectroscopy, steady-state fluorescence spectroscopy, and cyclic voltammetry (CV).

Full text of DOI:10.1039/c2ta01318e

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C–H activation: making diketopyrrolopyrrole derivatives
easily accessible†
Cite this: DOI: 10.1039/c2ta01318e
Shi-Yong Liu,ab Min-Min Shi, Jia-Chi Huang,a Zheng-Neng Jin,ab Xiao-Lian Hu,a
a
*
a
a
ac
a
*
*
and Hong-Zheng Chen
Jun-Ying Pan, Han-Ying Li, Alex K.-Y. Jen
Diketopyrrolopyrrole (DPP) derivatives are an important class of high-performance pigment used in inks,
paints, plastics, and organic electronics. Until now, DPP derivatives containing sophisticated aryl units at
the DPP core have usually been obtained via Suzuki, Stille, or Negishi cross-coupling reactions, which
require organometallic precursors. In this work, a series of DPP-based p-conjugated molecules bearing
diverse aryl substituents on the thiophene- or benzene-DPPs were facilely synthesized in moderate to
excellent yields through the Pd-catalyzed direct arylation of C–H bonds. The synthetic procedures
feature advantages over traditional C–C cross-coupling reactions such as: (1) avoidance of the use of
organometallic reagents in the starting materials leading to simpler byproducts and higher atom
economy, (2) fewer synthetic steps, (3) higher yields, (4) better compatibility with chemically sensitive
functional groups, and (5) simpler catalytic systems free of phosphine ligands. These advantages make
the present protocol an ideal and versatile strategy for the synthesis of DPP derivatives, especially for
structurally complicated DPPs that may possess chemically sensitive functionalities. The optical and
electrochemical properties of the synthesized DPPs (17 compounds) were systematically investigated
using UV-vis spectroscopy, steady-state fluorescence spectroscopy, and cyclic voltammetry (CV).
Received 30th November 2012
Accepted 21st December 2012
DOI: 10.1039/c2ta01318e
www.rsc.org/MaterialsA
used for small molecule bulk heterojunction (BHJ) OPVs,6,7
FETs,8 dye-sensitized solar cells (DSSCs),9 and chemical
1 Introduction
sensors10 in addition to their extensive applications in inks,
paints, and the plastics industry.
Numerous diketopyrrolopyrrole (DPP) derivatives have been
synthesized since DPP was discovered by Farnum et al. in 1974
(ref. 1) and the synthetic pathway was subsequently improved in
the early 1980s, showing their technological and scientic
importance.2 DPP derivatives were rst commercialized as
pigments. In recent years, DPPs have also been widely explored
for optoelectronic applications because of their unique
p-conjugated systems as well as their exceptional stability.3 For
example, the DPP unit functions as an excellent electron-with-
drawing unit in low-bandgap donor–acceptor copolymers for
organic photovoltaic cells (OPVs)4 and eld effect transistors
(FETs),5 which display some of the highest mobilities reported
due to the remarkable aggregating properties of the DPP
moieties.3c,d,5a Small DPP-based molecules have also been widely
Among various DPP derivatives that have been studied,
thiophene-functionalized DPPs have attracted extensive atten-
tion for their applications in organic electronics.3b–d,4–7 This is
due to the fact that the electron richness of the thiophene
moiety can induce strong intramolecular charge transfer with
the electron-decient DPP core and p–p stacking of the
resulting conjugating units to create improved optical and
electrochemical properties. For example, the derivatives of
benzene-terminated thiophene-DPPs have been used either as
electron donors or electron acceptors in small molecule based
BHJ solar cells.6a,d,e,7a Recently, DPP-based small molecules with
two bithiophene units connected to both sides of the DPP core
have also been explored, generating very promising results in
BHJ solar cells. Due to their bipolar charge-transporting prop-
erties, bithiophene-functionalized DPP compounds could be
used both as electron donor6c,f and acceptor materials.7b
Usually, these thiophene-DPP functional molecules are
synthesized via the Suzuki, Stille, or Negishi cross-coupling
reactions, which involve the preparation of organoboron,
organotin, or organozinc reagents, respectively.6,7a,11 Neverthe-
less, thiophene has been regarded as an ideal moiety in
synthetic organic chemistry for direct arylation with aryl
halides due to the ease of palladation through a concerted
aMOE Key Laboratory of Macromolecular Synthesis and Functionalization, State Key
Laboratory of Silicon Materials, Department of Polymer Science and Engineering,
Zhejiang University, Hangzhou 310027, P. R. China. E-mail: hzchen@zju.edu.cn;
minminshi@zju.edu.cn; ajen@u.washington.edu
bDepartment of Pharmacy & Chemistry, Taizhou University, Taizhou 317000, P. R.
China
cDepartment of Materials Science and Engineering, University of Washington, Seattle,
WA 98198, USA
† Electronic supplementary information (ESI) available: The detailed synthetic
routes of all DPPs, 1H NMR spectra of parent DPP 1a–e, PL, 1H and 13C NMR,
and some MALDI-TOF MS spectra of DPP 1–17. See DOI: 10.1039/c2ta01318e
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Table 1 Optimization of reaction conditions for the direct arylation of DPPa
metalation–deprotonation (CMD) pathway.12 This results in a
highly selective reaction at the 2/5 positions on the thiophene
ring. The excellent CMD pathway introduced by Fagnou et al.12
and the similar proton abstraction mechanism proposed by
Echavarren and Maseras13 have enabled various electron-de-
cient aromatics and thiophene rings to be used as valid arene
coupling partners for direct arylations.14 These reactions
possess numerous advantages over traditional cross-coupling
reactions such as: (1) avoidance of the use of organometallic
reagents in the starting materials leading to simpler byproducts
and higher atom economy, (2) fewer synthetic steps, (3) higher
yields, (4) better compatibility with chemically sensitive func-
tional groups, and (5) simpler catalytic systems free of phos-
phine ligands.15
Entry
Time
Solvent
Ligand
Additive
Yieldd
b
1
2
3
24 h
12 h
2 h
Toluene
DMA
DMA
PCy3
PivOHc
None
96%
96%
96%
None
None
PivOHc
With these advantages, DPP-containing thiophene deriva-
tives should be ideal candidates for the exploration of direct
arylation reactions. However, there is very little information
regarding the synthesis of DPP derivatives via direct arylation.
During the preparation of this paper, Marder et al. recently
reported the synthesis of several bis-arene-functionalized DPPs
through direct arylation reactions.16 In our independent study,
we have systematically investigated the conditions of direct
arylation for DPPs. Four types of DPP that are being extensively
studied in the organic electronics eld including various
derivatives of benzene-thiophene-DPP, bithiophene-DPP, thio-
phene-benzene-DPP, pentauorophenyl capped DPP, and
sophisticated multi DPP cores, have all been synthesized via
direct arylation. Most of these compounds could be obtained in
moderate to excellent yields. The results from this study provide
a generally applicable methodology for the broad application of
direct arylation to synthesize DPPs and other useful p-conju-
gated materials.
a
DPP 1a (105 mg, 0.2 mmol), bromobenzene (78 mg, 0.5 mmol),
anhydrous K2CO3 (69 mg, 0.5 mmol), anhydrous solvent 2 mL,
Pd(OAc)2 (2.3 mg, 0.010 mmol), carried out at 110 ꢀC under an N2
b
c
atmosphere. PCy3$HBF4 (0.02 mmol, 7.4 mg). PivOH (6.1 mg,
0.06 mmol, 30 mol%). Isolated yields.
d
with the addition of PivOH, the reaction time could be short-
ened to 2 h with 96% yield. The color change of the reaction
mixture observed was obvious even aer 0.5 h. This result
demonstrates that pivalic acid plays a key role in direct arylation
involving the CMD pathway.12–14 The similar high reactivity in
ligandless catalysis with pivalic acid in DMA solvent has also
been observed by Hartwig and Tan.15
The optimized reaction conditions found in Table 1 (5 mol%
Pd(OAc)2, 30 mol% PivOH, 2.5 equiv. K2CO3, anhydrous DMA)
were subsequently applied to the preparation of a series of DPP-
based conjugated molecules starting from the ve parent DPPs
shown in Fig. 1 (DPP 1a–e) with various bromoarenes, thio-
phene derivatives, and pentauorobenzene. The parent DPP 1a,
1b, 1d and 1e were prepared according to our previous report
and the literature;4b,19,20 and DPP 1c was synthesized from the
Suzuki coupling of phenylboronic acid with mono-bromo-
thiophene DPP (see Experimental section and ESI, Scheme S1†).
Fig. 1 shows the photos of the CHCl3 solutions of each
individual DPP made and their simplied synthetic routes.
Interestingly, the seventeen DPP dyes synthesized from ve
parent DPPs cover a broad color spectrum ranging from yellow,
orange, red-purple, purple, blue-purple, blue, to green as
shown in Fig. 1.
2 Results and discussion
2.1 Optimization of reaction conditions for direct arylation
of DPP
To determine the appropriate conditions for direct arylation, a
model reaction involving the coupling between thiophene-DPP
(DPP 1a, Table 1) and bromobenzene was carried out under
three sets of conditions. The results are summarized in Table 1.
Because tricyclohexylphosphine (PCy3) has been reported as an
effective ligand for the Pd-catalyzed direct arylation of thio-
phene derivatives in toluene,17 the catalytic system combining
Pd(OAc)2 with PCy3 was examined rst. The catalysis using PCy3
gave DPP 1 with a 96% yield in 24 h (entry 1). During the
reaction, a color change from red to purple was observed in the
reaction mixture aer 12 h. In addition to phosphine ligands,
the direct arylation of thiophene derivatives using phosphine-
free catalytic systems in polar solvents has been developed in
recent years.18 We have also examined the catalytic system
without using phosphine ligands. Entry 2 in Table 1 shows that
the use of Pd(OAc)2, K2CO3 in dimethylacetamide (DMA) as a
catalytic system gave DPP 1 in 96% yield with a shorter reaction
time (12 h). To our surprise, the reaction in this phosphine-free
Table 2 summarizes the substrates and the seventeen DPP
derivatives synthesized from the ve DPP cores. The seventeen
synthesized DPPs, which are divided into four categories as
benzene-derivative-thiophene DPPs (DPP 1–9), thiophene-
derivative-thiophene or thiophene-derivative-benzene DPPs
(DPP 10–15), pentauorophenyl capped DPPs (DPP 6 and 16)
and DPP–DPP-based oligomers (DPP 9 and 17), are described in
detail later.
2.2 Direct arylation of thiophene-DPP with the bromides of
benzene derivatives
catalytic system could be further accelerated greatly in the Firstly, we investigated the arylation of DPP 1a using the
presence of pivalic acid (PivOH). As shown in entry 3 in Table 1, bromides of benzene derivatives. As shown in entries 1–9 of
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Fig. 1 Digital photos of CHCl3 solutions of all the DPPs and the simplified synthetic routes for DPP 1–17 from the corresponding reactants, the given values indicate
the yields for the reactions.
Table 2, DPPs functionalized with various benzene derivatives could be replaced with an aryl bromide and the simpler DPP 1a,
were readily obtained through direct C–H arylation with good to respectively. Entry 3 in Table 2 shows that the direct arylation
excellent yields in short reaction times. The reaction time (4 h) proceeded smoothly using a catalytic amount of Pd(OAc)2 with
is much shorter than that used for traditional Suzuki, Stille and 30 mol% pivalic acid and 2.5 equiv. K2CO3 in DMA to give DPP 3
Negishi cross coupling reactions, indicating that thiophene- in 92% yield (For comparison, see ESI, case 1 of Scheme S20†).
DPPs are ideal substrates for direct arylation. It is noteworthy The direct arylation of the activated C–H bond provides a more
that no phosphine ligand is needed under these conditions.
straightforward pathway employing simpler starting materials.
In a previous report, DPP 3 was used as an electron donor in
As indicated in entries 5 and 6, DPP 5 and DPP 6 containing
small molecule BHJ solar cells devices.6d An analogue of DPP 3 uorine atoms were synthesized by the direct arylation of DPP
with dodecyl groups on N atoms has also been used as an 1a with the corresponding bromoarenes in 93% and 87% yield,
electron acceptor in BHJ solar cells by the same research respectively. It should be noted that we also tried to prepare DPP
group.7a DPP 3 was produced previously in 69% yield from a 5 using the Suzuki coupling of (2,6-diuorophenyl) boronic
Pd(PPh3)4-catalyzed Suzuki coupling reaction between DPP 1b acid with DPP 1b, but no desired product was obtained.
and 4-(triuoromethyl) phenylboronic acid.6d However, using This is because the electron density on the carbon atom in
direct arylation, the aryl boronic acid and di-bromide DPP 1b the C–B bond is signicantly reduced due to the strong
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Table 2 Synthesis of the 17 DPP derivatives from five parent DPPs via direct arylationa
Entry
Parent DPP
Ar0–R2
Product
Yieldb (%)
Entry
Parent DPP
Ar0–R2
Product
Yieldb (%)
1
2
3
4
DPP 1a
DPP 1a
DPP 1a
DPP 1a
DPP 1c
DPP 2
DPP 3
DPP 4
96
10
11
12
13
DPP 1a
DPP 1b
DPP 1b
DPP 1b
DPP 10
DPP 10
DPP 11
DPP 12
45e (10)7b
40e
94
92 (69)6d
91
53e (25)6c
47e
5
DPP 1a
DPP 5
93
14
DPP 1b
DPP 13
46e (31)11
6
7
8
DPP 1a
DPP 1a
DPP 1a
DPP 6
DPP 7
DPP 8
87
15
16
17
DPP 1d
DPP 1d
DPP 1b
DPP 14
DPP 15
DPP 6
75e
60e
95
95 (45)6e
92 (98)6e
9
DPP 1c
DPP 9
90d
18
19
DPP 1e
DPP 1d
DPP 16
DPP 17
95 (13)26
95f
DPP 1c
a
Parent DPP (0.2 mmol), Ar0–R2 (0.5 mmol), anhydrous K2CO3 (69 mg, 0.5 mmol), Pd(OAc)2 (2.3 mg, 0.010 mmol), PivOH (6.1 mg, 0.06 mmol),
b
anhydrous DMA 2 mL, carried out at 110 ꢀC for 4 h under an N2 atmosphere. Isolated yield, the yields in parentheses are from the literature.
c
d
e
f
Reaction time 2 h. Dibromo-carbazole (0.2 mmol), DPP 1c (0.5 mmol), reaction time 10 h. Reaction temperature 100 ꢀC. DPP 1d
(0.2 mmol), DPP 1c (0.5 mmol), reaction time 12 h.
electron-withdrawing effect of the two adjacent C–F bonds,
To obtain DPP derivatives containing multi DPP cores, a
leading to the reduced reactivity of the Suzuki coupling. A thiophene-DPP capped with a phenyl group on one side was
similar experimental result was also observed in (per- designed (DPP 1c, Fig. 1). If the remaining 50 C–H bond of the
uorophenyl) boronic acid with no DPP 6 being obtained from thiophene ring on DPP 1c could be arylated by a di-bromide, it
the corresponding Suzuki coupling. The cases of DPP 5 and DPP would give a DPP derivative with two DPP cores. To test this
6 demonstrate that direct arylation could proceed effectively idea, a 2,7-dibromo-carbazole derivative was chosen to couple
with compounds that the commonly used C–C coupling reac- with DPP 1c. Scheme 1 shows the route (entry 9, Table 2).
tions cannot work with.
As expected, the target DPP 9 was obtained in 90% yield
DPP 7 and an analogue of DPP 8 have previously been used (calculated from carbazole). Such a large molecule with a
as electron donors in small molecule BHJ solar cells.6e In this
previous report, DPP 7 and DPP 8 were produced from the
Suzuki coupling of dibromo-thiophene-DPP with an aryl
boronic ester or acid with a total yield of 45% or 98%, respec-
tively.6e Herein, DPP 7 and DPP 8 were obtained via the direct
arylation of thiophene-DPP with the corresponding aryl
bromides in yields of 95% and 92%, respectively (entries 7 and
8), with no organo-boron reagent used (ESI, cases 2 and 3 in
Scheme S20†).
Scheme 1 Synthesis of DPP 9 from 2,7-dibromo-carbazole and DPP 1c.
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molecular weight of 1477.14 was veried by H and 13C NMR, study, DPP 11 can be obtained straightforwardly via the direct
MALDI-TOF MS (found, 1477.04) and elemental analysis (see arylation between ethyl thiophene-2-carboxylate and DPP 1b to
ESI, Fig. S16†). By extending this strategy to multi-bromide aryl afford DPP 11 in 53% yield in one step (entry 12). Additionally, it
analogs, DPP derivatives with multi-DPP cores can be obtained. was found that the analog hexyl thiophene-2-carboxylate could
also be directly arylated by DPP 1b under the same conditions to
give DPP 12 in 47% yield (Table 2, entry 13).
In this work, the direct arylation of the a-C–H bond of a
thiophene by DPP 1d leading to the formation of thiophene-
2.3 Direct arylation for the synthesis of bithiophene or
thiophene-benzene-DPP
Previously, a DPP derivative containing two bithiophene units at benzene-DPP was also investigated. Two thiophene derivatives,
the DPP core has been mentioned in a patent on DPP uo- thiophene-2-carbaldehyde and ethyl thiophene-2-carboxylate,
rophores21 and its detailed synthesis was described in 2008.22 were arylated by DPP 1d and gave the targets DPP 14 and DPP 15
Bithiophene-functionalized DPP compounds have been used as shown in Table 2 with yields of 75% and 60%, respectively (entry
both electron donors6c,f and acceptors7b in BHJ solar cells. 15 and 16, Table 2), which are higher than those of their thio-
Bithiophene-functionalized DPPs are usually obtained by phene-DPP counterparts (entries 10–12).
palladium-catalyzed cross coupling reactions. Recently, the
improvement of synthetic procedures for DPP derivatives
2.4 Direct arylation of pentauorobenzene for the synthesis
of pentauorophenyl functionalized DPPs
bearing bithiophene moieties has been investigated by several
groups.11,23 For example, Wurthner and co-workers tried
¨
different C–C couplings to synthesize 5-carbonitrile-bithio-
phene functionalized DPP (DPP 13 in Table 2). The synthesis
proceeded smoothly to give the target DPP in 31% total yield,
rst by the deprotonation of DPP 1a, followed by the quenching
of the reactive intermediate with a boronic ester to install the
requisite boron for the subsequent Suzuki coupling reaction.11
Alternatively, DPP 13 could be obtained in one step (46% yield)
by reacting DPP 1b with thiophene-2-carbonitrile through direct
arylation (as shown in entry 14 (Table 2)), while avoiding
organoboron reactants (for comparison of routes, see ESI,
Scheme S20†).
As reported by Janssen et al., a 5-carbaldehyde-bithiophene-
DPP with a low-lying HOMO level can be synthesized and used
as an acceptor in BHJ solar cells.7b In their reported synthetic
procedure, the corresponding aldehyde-DPPs were prepared by
the deprotonation of the Stille coupling-obtained bithiophene-
DPP using lithium diisopropylamide (LDA), followed by the
quenching of the dianion with N,N-dimethylformamide (DMF)
to afford a total yield of <10%. In contrast, as shown in Table 2
(entry 10), 5-carbaldehyde-bithiophene-DPP (DPP 10) can be
obtained in one step with a 45% yield using the direct arylation
between 5-bromothiophene-2-carbaldehyde and DPP 1a, while
avoiding organometallic intermediates and low-temperature
conditions (ESI, case 4, Scheme S20†). Alternatively, DPP 10
can be synthesized in 40% yield from the arylation of thio-
phene-2-carbaldehyde with DPP 1b (Fig. 1, and entry 11 in
Table 2), demonstrating the versatility of the direct arylation
methodology.
Like thiophene derivatives, pentauorobenzene is also an ideal
moiety for direct arylation via the CMD pathway, which renders
the relatively acidic H on pentauorobenzene highly reactive
toward aryl bromide.12,17,25 The introduction of electron-with-
drawing substituents, such as uoro groups, onto the DPP or
other p-structures should provide the molecules with high
electron affinities.7a,24 The introduction of a pentauorophenyl
group onto a DPP is expected to produce a molecule with an
improved electron affinity and a well-ordered stacking structure
due to its electron-withdrawing ability and the p-conjugation
extension. Herein, two bromides, DPP 1b and DPP 1e, were
chosen as coupling partners to arylate pentauorobenzene
(entries 17 and 18 in Table 2). The routes are shown in Scheme
2. Gratifyingly, the arylation of pentauorobenzene by DPP 1b
and DPP 1e gave the targets DPP 6 and DPP 16, respectively,
with 90% and 95% yields under the optimized conditions.
As described above, DPP 6 has also been obtained in high
yield from the direct arylation of DPP 1a by pentauorophenyl
bromide (Fig. 1, and entry 6 in Table 2). The examples of entries
6 and 17 in Table 2 demonstrate that in cases where both arenes
have been demonstrated to undergo direct arylation, such as
with thiophenes and pentaourobenzene, it is possible to
switch the bromine substitution such that bromothiophene and
a simple arene are utilized as coupling partners (ESI, Scheme
S8†).17 The examples also demonstrate that direct arylation is a
versatile tool for the synthesis of functionalized DPPs.
It is noteworthy that an analogue of DPP 16 has been previ-
ously synthesized by Kanbara et al. via Suzuki C–C coupling of
the biphenyl-DPP boronic ester with pentauorophenyl
During the course of this study, an ester-functionalized
bithiophene-DPP was synthesized and applied to BHJ solar cells
by our group. An impressive power conversion efficiency (PCE)
of 4.02% was achieved for this material.6c In that study, the
5-carboxylate-bithiophenyl-DPP (DPP 11 in Table 2) was
synthesized via a Stille coupling reaction between 3,6-bis[(5-
(trimethylstannyl)thiophen-2-yl)]-DPP with ethyl 5-bromothio-
phene-2-carboxylate. The DPP tin precursor was obtained via
the deprotonation of DPP 1a followed by quenching with
Me3SnCl. The synthetic procedure comprised of two key steps
that afforded DPP 11 in <25% yield.6c However, in our current Scheme 2 Direct arylation of pentafluorobenzene by DPP 1b and 1e.
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iodide.26 However, the reported procedure was comprised of in Fig. 2 and Table 3, the absorption peaks of DPP 1–17 in CHCl3
two key steps, with a total yield of only 13% (see ESI, case 6 of solution range from 482 nm to 626 nm, in accordance with the
Scheme S20†).
various colours observed. The structures of DPP 1–6 are slightly
different from each other. However, it is interesting to observe
that the solution of DPP 4 has a blue color, which differs much
from that of DPP 1–3, 5 and 6 (Fig. 1). DPP 4 exhibits an
absorption peak at a longer wavelength of 623 nm (Fig. 2). This
can be ascribed to the fact that the sp2 N in the –NO2 group
extends the effective p-conjugation length of DPP 4, resulting in
the red shi of the absorption.
2.5 Direct arylation between DPPs
Anthopoulos et al. have recently reported a DPP–DPP-based
conjugated copolymer synthesized via a Suzuki reaction.27 Due
to the strong inter- and intra-molecular donor–acceptor inter-
actions between DPP units, the copolymer exhibited a high
electron mobility of over 1 cm2 Vꢁ1 sꢁ1. The intense donor–
acceptor interactions should also be expected to improve the
optical and electronic properties of DPP–DPP-based molecules
or oligomers, whose synthesis has been rarely reported,
however. For these reasons, we decided to prepare the DPP–
DPP-based oligomer via direct arylation. The successful
synthesis of DPP 9 (entry 9 in Table 2 and Scheme 1) demon-
strates that DPP 1c can be effectively arylated by a multi-
brominated aromatic molecule, affording molecules with more
extended p-conjugation containing multiple DPP cores. To
obtain DPP–DPP-based oligomers, DPP 1d, as an aryl di-
bromide, was tested for the arylation of the 50 C–H bond on the
thiophene ring of DPP 1c (entry 19, Table 2). Scheme 3 shows
the synthetic route. Interestingly, under the above-mentioned
conditions, a p-conjugated molecule involving three DPP cores
(DPP 17) was obtained in one step with 95% yield (calculated
from DPP 1d).
The structure and molecular weight of DPP 17 (1710.44) were
veried by using 1H and 13C NMR, MALDI-TOF MS (found,
1710.39), and elemental analysis (see ESI, Fig. S24†). It is
noteworthy that, if traditional C–C coupling was applied to the
synthesis of DPP 17, either DPP 1c or DPP 1d should be further
converted to organo-boronic or organo-tin compounds and
more steps would be involved. The direct arylation provides a
simpler and more efficient method. This example demonstrates
that this methodology not only can be generally applicable to
reactions between common aryl derivatives and DPPs, but
also between DPPs themselves, leading to DPP–DPP-based
oligomers.
The absorption band-edges (lonset) of the DPPs and the cor-
responding optical band-gaps (Eogpt) calculated from 1240/lonset
are also summarized in Table 3. The electrochemical properties
of DPP 1–17 were investigated by cyclic voltammetry (CV). The
CV curves were recorded versus the potential of the SCE, which
was calibrated by the ferrocene–ferrocenium (Fc/Fc+) redox
couple (4.8 eV below the vacuum level). The cyclic voltammo-
grams of the seventeen DPPs are shown in Fig. 3, and the
electrochemical data are summarized in Table 3. The HOMO
energy levels were calculated from the CV and the correspond-
ing LUMO levels were estimated from ELUMO ¼ EHOMO + Egopt
.
The HOMO levels of DPP 1–17 decrease with the increase of
the electron-withdrawing ability of the substituents at the 3, 6
positions of the DPP cores. The electron-withdrawing abilities
of the substituents follow the order DPP 16 > DPP 14 > DPP 15 >
DPP 6 > DPP 4 > DPP 13 > DPP 10 > DPP 3 > DPP 11 z DPP 12 >
DPP 5 > DPP 8 > DPP 1 > DPP 2 > DPP 17 > DPP 9 > DPP 7.
Accordingly, the HOMO levels of DPP 1–17 obtained from the
CV interestingly follow the order DPP 16 < DPP 14 < DPP 15 <
DPP 6 < DPP 4 < DPP 13 < DPP 10 < DPP 3 < DPP 11 z DPP 12 <
DPP 5 < DPP 8 < DPP 1 < DPP 2 < DPP 17 < DPP 9 < DPP 7
(Table 3).
Table 3 Optical and electrochemical properties of DPP 1–17a
lem
lonset
Eogpt
DPP
labs (nm)
(nm)
HOMO (eV)
(nm)
(eV)
LUMO (eV)
1
2
3
4
5
6
7
8
596.5
600.5
597.5
623.7
590.0
587.5
632.0
587.0
626.0
632.0
622.0
623.0
618.0
503.0
499.5
482.0
624.0
625
630
628
665
621
622
674
651
657
678
664
664
662
592
581
553
676
5.25
5.19
5.34
5.39
5.31
5.44
5.09
5.25
5.14
5.36
5.318
5.313
5.38
5.58
5.55
5.62
5.15
631
635
635
666
625
627
678
645
663
685
673
668
672
570
565
536
683
1.97
1.95
1.95
1.86
1.98
1.98
1.83
1.92
1.87
1.81
1.84
1.86
1.85
2.18
2.20
2.31
1.82
3.28
3.23
3.38
3.53
3.33
3.46
3.27
3.32
3.27
3.55
3.48
3.46
3.54
3.41
3.36
3.31
3.33
2.6 Optical and electrochemical properties of DPP 1–17
As shown in Fig. 1, the solutions of the synthesized DPP 1–17
cover a broad color spectrum including various colors. The
optical properties of DPP 1–17 were studied by UV-vis and
steady-state uorescence spectroscopy. The signicant optical
properties are listed in Table 3.
9
Fig. 2 shows the UV-vis spectra. All the DPPs show a broad
absorption band in the visible to near-infrared region. As shown
10
11
12
13
14
15
16
17
a
All data were obtained from the solutions of the DPPs. UV-vis spectra
were recorded in CHCl3 solutions. CV was done with a Pt disk, a Pt plate,
and an SCE as the working electrode, counter electrode, and reference
electrode, respectively, in a 0.1 mol Lꢁ1 Bu4NPF6 CH2Cl2 solution.
Scheme 3 Direct arylation of DPP 1c by DPP 1d.
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Fig. 3 Cyclic voltammograms of DPP 1–17 in dry CH2Cl2 solution; scan rate
50 mV sꢁ1 in 0.1 M NBu4PF6.
comparison indicates that the LUMO can be more effectively
lowered by the DPP core than the HOMO.
3 Conclusion
Fig. 2 UV-vis absorption spectra of DPP 1–17 in CHCl3.
In summary, direct arylation has been demonstrated as a
powerful, versatile and straightforward tool for the synthesis
of diketo-pyrrolo-pyrrole dyes. Seventeen DPPs, including
compounds that are unreactive for commonly used C–C
couplings, benzene-thiophene-DPPs, thiophene-thiophene-
DPPs, thiophene-benzene-DPPs, and DPP–DPP-based oligo-
mers, have all been facilely synthesized via the direct arylation
of C–H bonds in moderate to excellent yields. The obtained
DPPs have broad absorption bands from the visible to near-
infrared region, and some of them show suitable HOMO and
LUMO energy levels for photovoltaic applications. It is
believed that more DPP-based molecules or other functional
materials could be synthesized via the direct arylation. Also, as
a valuable alternative, direct arylation combined with tradi-
tional C–C coupling should make the synthesis of p-conju-
gated functional molecules or polymers more facile and
versatile.
The low bandgap DPPs such as DPP 4, DPP 9, DPP 11, DPP 12
and DPP 17 may have applications in OPVs. The appropriate
frontier orbital energy levels and good absorption in the NIR
region would make DPP 17 an ideal molecule for OPV applica-
tions. Alternatively, the DPPs, including DPP 6, DPP 14, DPP 15
and DPP 16, with strong electron-withdrawing groups may serve
as n-type and electron acceptor materials. Marks et al. reported
an n-type semiconducting peruorophenyl-capped quarter-
thiophene with HOMO and LUMO levels of ꢁ5.48 and ꢁ2.85 eV,
respectively.24a Compared with Marks' molecule, DPP 6 exhibi-
ted a comparable HOMO (ꢁ5.44 eV) but much lower LUMO
(ꢁ3.46 eV) (Table 3). The structural difference between Marks'
molecule and DPP 6 is that the central bi-thiophene unit of
the former is changed to a diketopyrrolopyrrole core. This
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that for DPP 1d except that the 2-ethylhexyl bromide was
changed to 2-hexyldecyl bromide. H NMR (300 MHz, CDCl3) d
4 Experimental section
4.1 Synthesis of parent DPP 1a–e
1
7.64 (s, 8H), 3.70 (d, J ¼ 7.2 Hz, 4H), 1.49 (d, J ¼ 19.2 Hz, 2H),
DPP 1a (2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]
pyrrole-1,4(2H,5H)-dione) was synthesized according to the
reported literature.4b,19 1H NMR (300 MHz, CDCl3) d 8.88 (dd, J ¼
3.9, 1.2 Hz, 2H), 7.62 (dt, J ¼ 2.1, 1.1 Hz, 2H), 7.28–7.27 (m, 2H),
4.08–3.91 (m, 4H), 1.86 (m, 2H), 1.32–1.15 (m, 16H), 0.95–0.73
(m, 12H).
DPP 1b19 (3,6-bis(5-bromothiophen-2-yl)-2,5-bis(2-ethylhexyl)
pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). DPP 1a (2.62 g, 5 mmol)
and N-bromosuccinimide (1.78 g, 10 mmol) were dissolved into
chloroform (150 mL) in a two-necked round ask under argon
protection, and then the solution was protected from light and
stirred at room temperature. Aer 40 h, the mixture was poured
into 200 mL of methanol and then ltered. The lter cake was
washed by hot methanol twice. Aer drying in vacuum, the pure
product was obtained as a purple-black solid (DPP 1b, 2.7 g,
yield 80%). 1H NMR (300 MHz, CDCl3) d 8.65 (d, J ¼ 4.2 Hz, 2H),
7.25–7.18 (m, 2H), 3.93 (dd, J ¼ 7.8, 3.6 Hz, 4H), 1.83 (s, 2H),
1.36 (m, 16H), 0.94–0.75 (m, 12H).
1.24–1.05 (m, 48H), 0.89–0.80 (m, 12H).
4.2 Synthesis of DPP derivatives DPP 1–17
A typical procedure for C–H arylation towards the seventeen
DPPs (Table 2) is as follows. The parent DPP (0.2 mmol), Ar–R2
(0.5 mmol), anhydrous K2CO3 (69 mg, 0.5 mmol), pivalic acid
(6.1 mg, 0.06 mmol), Pd(OAc)2 (2.3 mg, 0.010 mmol) were stir-
red in anhydrous DMA (2 mL) for 2–4 h (DPP 1, 2 h; DPP 2–8 and
10–16, 4 h) at 100–110 ꢀC (DPP 1–8 and 16, 110 ꢀC; DPP 10–15,
ꢀ
100 C) under a nitrogen atmosphere in a Schlenk tube. Aer
cooling to room temperature, the mixture was poured into a
150 mL aqueous solution of NaCl to remove the salts and high
boiling point solvent DMA. The precipitate was extracted with
ethyl acetate (3 ꢂ 20 mL). The combined organic layer was
washed with distilled water and dried over MgSO4. Removal of
the ethyl acetate by a rotary evaporator afforded the crude
products, which were then puried by column chromatography
on silica gel using the mixture of CH2Cl2 and petroleum ether as
eluent and gave the product.
For DPP 9, 2,7-dibromo-9-(2-ethylhexyl)-9H-carbazole
(0.2 mmol), DPP 1c (0.5 mmol), reaction time 10 h, reaction
temperature 110 ꢀC. The other conditions were similar to those
above.
DPP 1c19 (2,5-bis(2-ethylhexyl)-3-(5-phenylthiophen-2-yl)-6-
(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). N-Bromo-
succinimide (0.85 g, 4.76 mmol) was added in portions to a
solution of DPP 1a (2.5 g, 4.76 mmol) in CHCl3 (50 mL) in a two-
necked ask at 5 ꢀC. The mixture was warmed to room
temperature and stirred overnight. CH2Cl2 was added and then
the solution was washed with brine. The organic phase was
dried (MgSO4) and the solvent was evaporated under reduced
pressure. The crude product was puried chromatographically
(silica gel; CH2Cl2–petroleum ether, 2 : 1) to yield a red solid
For DPP 17, DPP 1d (132 mg, 0.2 mmol), DPP 1c (300 mg,
0.5 mmol), reaction time 12 h, reaction temperature 110 ꢀC. The
other conditions were similar to those above.
DPP
1 (2,5-bis(2-ethylhexyl)-3,6-bis(5-phenylthiophen-2-yl)
1
(1.70 g, 63%). H NMR (300 MHz, CDCl3) d 8.90 (d, J ¼ 3.9 Hz,
pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2 and
petroleum ether (2 : 1, v/v) as eluent gave a dark purple crys-
talline solid (129 mg, 96% yield), 1H NMR (300 MHz, CDCl3) d
8.96 (d, J ¼ 4.1 Hz, 2H), 7.68 (dd, J ¼ 7.1, 1.0 Hz, 4H), 7.51–7.29
(m, 8H), 4.16–4.00 (m, 4H), 1.94 (d, J ¼ 5.9 Hz, 2H), 1.58–1.15
(m, 16H), 0.99–0.70 (m, 12H); 13C NMR (126 MHz, CDCl3) d
161.75, 149.67, 139.91, 136.78, 133.20, 129.16, 128.84, 128.81,
126.14, 124.49, 108.21, 45.99, 39.24, 30.35, 28.57, 23.70,
23.10, 14.05, 10.58; MALDI-TOF MS (m/z): [M]+ calcd for
1H), 8.64 (d, J ¼ 4.2 Hz, 1H), 7.65 (d, J ¼ 5.1 Hz, 1H), 7.29–7.18
(m, 2H), 4.03–3.92 (m, 4H), 1.84 (m, 2H), 1.38–1.23 (m, 16H),
0.91–0.83 (m, 12H).
The above mono-bromo-DPP (1.21 g, 2 mmol), phenylboronic
acid (305 mg, 2.5 mmol), and K2CO3 (345 mg, 2.5 mmol) were
dissolved in 30 mL of toluene and ethanol (3 : 1) followed by 1 mL
H2O aꢀnd Pd(PPh3)4 (45 mg, 0.04 mmol), and was stirred for 24 h
at 85 C under a nitrogen atmosphere. The solvent was evapo-
rated under vacuum and the residue was partitioned between
CH2Cl2 and water; the organic phase was washed with brine and
dried (MgSO4) and then the solvent was evaporated. The residue
was puried chromatographically (silica gel; CH2Cl2–petroleum
ether, 1 : 1) and yielded a red purple solid (DPP 1c, 1.1 g, 91%). 1H
NMR (500 MHz, CDCl3) d 8.97 (d, J ¼ 4.1 Hz, 1H), 8.89 (d, J ¼
3.5 Hz, 1H), 7.68 (d, J ¼ 7.4 Hz, 2H), 7.62 (d, J ¼ 4.8 Hz, 1H),
7.42 (ddd, J ¼ 33.7, 14.1, 5.7 Hz, 4H), 7.30–7.27 (m, 1H), 4.16–3.89
(m, 4H), 1.93 (d, J ¼ 5.6 Hz, 2H), 1.37–1.25 (m, 16H), 0.88 (ddd,
J ¼ 20.0, 13.0, 7.0 Hz, 12H).
C
42H48N2O2S2, 676.9727; found, 676.3343; elemental analysis:
calcd for C42H48N2O2S2, C, 74.52; H, 7.15; N, 4.14%. Found: C,
74.54; H, 7.14; N, 4.12%.
DPP
2
(2,5-bis(2-ethylhexyl)-3,6-bis(5-(p-tolyl)thiophen-2-yl)
pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2 and
petroleum ether (2 : 1, v/v) as eluent gave a dark purple crys-
1
talline solid (132 mg, 94% yield), H NMR (500 MHz, CDCl3) d
8.95 (d, J ¼ 3.9 Hz, 2H), 7.57 (d, J ¼ 8.0 Hz, 4H), 7.43 (d, J ¼
4.1 Hz, 2H), 7.24–7.19 (m, 4H), 4.13–3.95 (m, 4H), 2.40 (s, 6H),
1.94 (d, J ¼ 5.5 Hz, 2H), 1.38–1.27 (m, 16H), 0.89 (dt, J ¼ 13.9,
7.3 Hz, 12H); 13C NMR (126 MHz, CDCl3) d 161.80, 149.96,
139.90, 139.05, 136.84, 130.50, 129.87, 128.37, 126.07, 124.02,
108.10, 45.99, 39.27, 30.39, 29.74, 28.66, 23.74, 23.15, 21.36,
14.10, 10.63; MALDI-TOF MS (m/z): [M]+ calcd for C44H52N2O2S2,
705.0259; found, 705.3841; elemental analysis: calcd for
DPP 1d (3,6-bis(4-bromophenyl)-2,5-bis(2-ethylhexyl)pyrrolo
[3,4-c]pyrrole-1,4(2H,5H)-dione) was synthesized according to
the reported literature.19a,20 1H NMR (500 MHz, CDCl3) d 7.65 (s,
8H), 4.12–3.94 (m, 4H), 1.46 (s, 2H), 1.07 (m, 16H), 0.88 (ddd, J ¼
20.0, 13.0, 7.5 Hz, 12H).
DPP 1e (3,6-bis(4-bromophenyl)-2,5-bis(2-hexyldecyl)pyrrolo
[3,4-c]pyrrole-1,4(2H,5H)-dione). The synthesis was similar to
C
44H52N2O2S2, C, 74.96; H, 7.43; N, 3.97%. Found: C, 74.86; H,
7.42; N, 3.98%.
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DPP
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3
(2,5-bis(2-ethylhexyl)-3,6-bis(5-(4-(triuoromethyl) (m, 16H), 4.20–3.82 (m, 4H), 1.94 (d, J ¼ 5.6 Hz, 2H), 1.39–1.25
phenyl)thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using (m, 16H), 0.92–0.84 (m, 12H); 13C NMR (126 MHz, CDCl3) d
CH2Cl2 and petroleum ether (2 : 1, v/v) as eluent gave a dark 148.56, 147.10, 139.66, 137.04, 129.44, 127.90, 126.93, 125.00,
purple crystalline solid (149 mg, 92% yield), 1H NMR (500 MHz, 123.68, 122.82, 45.98, 39.22, 30.31, 28.52, 23.68, 23.11, 14.08,
CDCl3) d 8.97 (dd, J ¼ 12.7, 6.9 Hz, 2H), 7.79 (d, J ¼ 8.2 Hz, 4H), 10.61; MALDI-TOF MS (m/z): [M]+ calcd for C66H66N4O2S2,
7.70–7.68 (m, 4H), 7.55–7.54 (d, 2H), 4.17–3.90 (m, 3H), 1.93 (d, 1011.3858; found, 1011.1261; elemental analysis: calcd for
J ¼ 5.5 Hz, 2H), 1.47–1.28 (m, 16H), 0.94–0.87 (m, 12H); 13C
C66H66N4O2S2, C, 78.38; H, 6.58; N, 5.54%. Found: C, 78.27; H,
NMR (126 MHz, CDCl3) d 161.65, 147.45, 139.84, 136.67, 136.46, 6.55; N, 5.58%.
130.05, 126.24, 126.17, 125.72, 125.00, 122.83, 108.70, 46.03,
DPP 8 (2,5-bis(2-ethylhexyl)-3,6-bis(5-(pyren-1-yl)thiophen-2-yl)
39.29, 30.37, 28.56, 23.72, 23.08, 14.05, 10.58; MALDI-TOF MS pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2 and
(m/z): [M]+ calcd for C44H46F6N2O2S2, 812.9687; found, petroleum ether (2 : 1, v/v) as eluent gave a dark purple crys-
1
813.3820; elemental analysis: calcd for C44H46F6N2O2S2, C, talline solid (170 mg, 92% yield), H NMR (500 MHz, CDCl3) d
65.01; H, 5.70; N, 3.45%. Found: C, 65.12; H, 5.72; N, 3.48%.
9.18 (d, J ¼ 3.9 Hz, 2H), 8.57 (d, J ¼ 9.3 Hz, 2H), 8.29–8.21
DPP 4 (2,5-bis(2-ethylhexyl)-3,6-bis(5-(4-nitrophenyl)thiophen- (m, 6H), 8.21–7.99 (m, 10H), 7.60 (d, J ¼ 3.9 Hz, 2H), 4.28–
2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2 and 3.85 (m, 4H), 2.06 (d, J ¼ 5.4 Hz, 2H), 1.42–1.26 (m, 16H), 0.98–
petroleum ether (3 : 1, v/v) as eluent gave a dark blue crystalline 0.87 (m, 12H); 13C NMR (126 MHz, CDCl3) d 161.87, 148.47,
solid (138 mg, 91% yield), 1H NMR (500 MHz, CDCl3) d 8.96 (d, 140.08, 136.31, 131.67, 131.42, 130.86, 130.40, 129.40, 128.99,
J ¼ 4.2 Hz, 2H), 8.29 (d, J ¼ 8.8 Hz, 4H), 7.82 (d, J ¼ 8.8 Hz, 4H), 128.55, 128.26, 128.17, 128.15, 127.27, 126.37, 125.76, 125.42,
7.62 (d, J ¼ 4.2 Hz, 2H), 4.08 (t, J ¼ 7.2 Hz, 4H), 1.91 (s, 2H), 1.41– 125.10, 124.69, 124.65, 124.47, 108.18, 46.11, 39.38, 30.36,
1.20 (m, 16H), 0.90 (dt, J ¼ 14.0, 7.3 Hz, 12H); 13C NMR 28.55, 23.69, 23.15, 14.09, 10.61; MALDI-TOF MS (m/z): [M]+
(126 MHz, CDCl3) d 161.58, 147.42, 146.29, 139.79, 139.10, calcd for C62H56N2O2S2, 925.2502; found, 925.5685; elemental
136.79, 131.17, 126.83, 126.45, 124.65, 109.15, 46.07, 39.33, analysis: calcd for C62H56N2O2S2, C, 80.48; H, 6.10; N, 3.03%.
30.35, 28.56, 23.71, 22.70, 14.11, 10.58; MALDI-TOF MS (m/z): Found: C, 80.56; H, 6.14; N, 3.10%.
[M]+ calcd for C42H46N4O6S2, 766.2859; found, 766.4314;
elemental analysis: calcd for C42H46N4O6S2, C, 65.77; H, 6.05; N, (thiophene-5,2-diyl))bis(2,5-bis(2-ethylhexyl)-3-(5-phenylthiophen-
7.30%. Found: C, 65.65; H, 6.07; N, 7.29%. 2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2 and
DPP 9
(6,60-(5,50-(9-(2-ethylhexyl)-9H-carbazole-2,7-diyl)bis-
DPP 5 (3,6-bis(5-(2,6-diuorophenyl)thiophen-2-yl)-2,5-bis(2- petroleum ether (3 : 1, v/v) as eluent gave a dark blue crystalline
ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2 solid (264 mg, 90% yield, calculated from dibromo-carbazole).
and petroleum ether (2 : 1, v/v) as eluent gave a dark purple 1H NMR (500 MHz, CDCl3) d 9.06 (s, 2H), 8.97 (s, 2H), 8.07 (d, J ¼
crystalline solid (139 mg, 93% yield), 1H NMR (500 MHz, CDCl3) 8.2 Hz, 2H), 7.64 (s, 4H), 7.56–7.52 (m, 6H), 7.42–7.34 (m, 8H),
d 9.06 (d, J ¼ 4.2 Hz, 2H), 7.76 (d, J ¼ 4.2 Hz, 2H), 7.34–7.23 (m, 4.07 (m, 10H), 2.00 (d, J ¼ 37.4 Hz, 5H), 1.41–1.25 (m, 40H),
2H), 7.04 (t, J ¼ 8.8 Hz, 4H), 4.16–3.97 (m, 4H), 1.94 (d, J ¼ 0.97–0.88 (m, 30H); 13C NMR (126 MHz, CDCl3) d 161.76, 161.63,
5.6 Hz, 2H), 1.49–1.25 (m, 16H), 0.93–0.84 (m, 12H); 13C NMR 150.71, 141.99, 139.76, 139.55, 137.22, 136.80, 135.18, 133.07,
(126 MHz, CDCl3) d 161.73, 160.78 (d), 158.76 (d), 140.09, 131.05, 129.12, 128.88, 128.73, 128.63, 126.04, 124.40, 124.30,
135.55, 134.99 (d), 130.41 (t), 129.25 (t), 112.18 (dd), 111.44 (t), 123.02, 120.99, 117.89, 108.16, 106.15, 45.99, 39.29, 31.93,
108.67, 46.09, 39.35, 30.31, 28.46, 23.64, 23.12, 14.02, 10.50; 30.36, 30.17, 29.71, 29.37, 28.61, 24.48, 23.73, 23.15, 23.02,
MALDI-TOF MS (m/z): [M]+ calcd for C42H44F4N2O2S2, 748.9346; 22.69, 14.10, 11.00, 10.50; MALDI-TOF MS (m/z): [M]+ calcd for
found, 749.1391; elemental analysis: calcd for C42H44F4N2O2S2,
C, 67.36; H, 5.92; N, 3.74%. Found: C, 67.39; H, 5.93; N, 3.72%. ysis: calcd for C92H109N5O4S4, C, 74.81; H, 7.44; N, 4.74%.
DPP (2,5-bis(2-ethylhexyl)-3,6-bis(5-(peruorophenyl)thio- Found: C, 74.77; H, 7.45; N, 4.75%.
phen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). Using CH2Cl2
DPP 10 (50,5000-(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahy-
C92H109N5O4S4, 1477.1410; found, 1477.0412; elemental anal-
6
and petroleum ether (2 : 1, v/v) as eluent gave a dark purple dropyrrolo[3,4-c]pyrrole-1,4-diyl)bis(([2,20-bithiophene]-5-carbal-
crystalline solid (154 mg, 90% yield), 1H NMR (300 MHz, CDCl3) dehyde))). Using CH2Cl2 and petroleum ether (7 : 1, v/v) as
d 9.03 (dt, J ¼ 4.2, 1.1 Hz, 2H), 7.71 (d, J ¼ 4.3 Hz, 2H), 4.06 (dd, eluent gave a dark blue crystalline solid (67 mg, 45% yield), 1H
J ¼ 7.7, 3.2 Hz, 4H), 1.90 (s, 2H), 1.47–1.25 (m, 16H), 0.99–0.83 NMR (500 MHz, CDCl3) d 9.84 (d, J ¼ 19.5 Hz, 2H), 8.86 (d, J ¼
(m, 12H); 13C NMR (126 MHz, CDCl3) d 161.68, 160.36, 145.18, 3.6 Hz, 2H), 7.64 (d, J ¼ 3.1 Hz, 2H), 7.46–7.37 (m, 4H), 3.98 (d,
143.29, 139.91, 137.27, 135.51, 131.78, 131.17, 109.07, 46.13, J ¼ 22.1 Hz, 4H), 1.88 (s, 2H), 1.35–1.25 (m, 16H), 0.83 (dd, J ¼
39.41, 30.33, 28.45, 23.58, 23.08, 13.97, 10.39; MALDI-TOF MS 18.5, 11.0 Hz, 12H); 13C NMR (126 MHz, CDCl3) d 182.34, 161.35,
(m/z): [M]+ calcd for C42H38F10N2O2S2, 856.8774; found, 145.10, 143.06, 140.83, 139.40, 137.05, 136.66, 130.43, 127.01,
856.9487; elemental analysis: calcd for C42H38F10N2O2S2, C, 125.50, 109.21, 46.04, 39.29, 30.29, 29.70, 28.46, 23.67, 23.07,
58.87; H, 4.47; N, 3.27%. Found: C, 58.67; H, 4.49; N, 3.24%.
DPP (3,6-bis(5-(4-(diphenylamino)phenyl)thiophen-2-yl)- 745.0484; found, 745.3813; elemental analysis: calcd for
2,5-bis(2-ethyl hexyl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione). 40H44N2O4S4, C, 64.48; H, 5.95; N, 3.76%. Found: C, 64.54; H,
14.06, 10.54; MALDI-TOF MS (m/z): [M]+ calcd for C40H44N2O4S4,
7
C
Using CH2Cl2 and petroleum ether (2 : 1, v/v) as eluent gave a 5.97; N, 3.69%.
dark purple crystalline solid (190 mg, 95% yield), 1H NMR
DPP 11 (diethyl-50,5000-(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-
(500 MHz, CDCl3) d 8.98 (s, 2H), 7.52 (d, J ¼ 5.4 Hz, 4H), 7.36 (d, tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)bis([2,20-bithiophene]-5-
J ¼ 3.8 Hz, 2H), 7.28 (dd, J ¼ 16.6, 8.8 Hz, 8H), 7.18–7.02 carboxylate)). Using CH2Cl2 and petroleum ether (6 : 1, v/v) as
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eluent gave a dark blue crystalline solid (88 mg, 53% yield), 1H yield), 1H NMR (500 MHz, CDCl3) d 7.82 (d, J ¼ 8.3 Hz, 4H), 7.72
NMR (300 MHz, CDCl3, Me4Si) d 8.91 (d, J ¼ 4.1 Hz, 2H), 7.72 (d, (dd, J ¼ 13.8, 6.1 Hz, 6H), 7.33 (d, J ¼ 3.9 Hz, 2H), 4.39 (q, J ¼ 7.1
J ¼ 3.9 Hz, 2H), 7.39 (d, J ¼ 3.9 Hz, 2H), 7.26 (d, J ¼ 4.1 Hz, 2H), Hz, 4H), 3.77 (dd, J ¼ 7.0, 4.6 Hz, 4H), 1.60 (s, 2H), 1.38 (dt, J ¼
4.37 (q, J ¼ 7.1 Hz, 4H), 3.95–4.10 (m, 4H), 1.82–1.97 (m, 2H), 14.3, 6.4 Hz, 6H), 1.26–1.10 (m, 16H), 0.87–0.66 (m, 12H); 13C
1.21–1.46 (m, 22H), 0.82–0.98 (m, 12H); 13C NMR (75 MHz, NMR (126 MHz, CDCl3) d 162.60, 162.02, 149.49, 147.86, 135.61,
CDCl3, Me4Si) d 161.99, 161.73, 142.49, 141.57, 139.65, 136.87, 134.19, 133.61, 129.44, 128.40, 126.10, 124.42, 110.02, 61.32,
134.38, 133.73, 129.76, 126.34, 125.36, 109.09, 61.70, 46.12, 45.00, 38.47, 30.30, 28.24, 23.76, 22.83, 14.35, 13.93, 10.42;
39.52, 30.58, 28.77, 23.92, 23.33, 14.56, 14.30, 10.79; MALDI- MALDI-TOF MS (m/z): [M]+ calcd for C48H56N2O6S2, 821.0980;
TOF MS (m/z): [M]+ calcd for C44H52N2O6S4, 833.1535; found, found, 821.2950; elemental analysis: calcd for C48H56N2O6S2, C,
833.8249; anal. calcd for C44H52N2O6S4: C, 63.43; H, 6.29; N, 70.21; H, 6.87; N, 3.41%. Found: C, 70.17; H, 6.84; N, 3.43%.
3.36%. Found: C, 63.54; H, 6.27; N, 3.21%.
DPP
16
(2,5-bis(2-hexyldecyl)-3,6-bis(pentauoro-[1,10-
Using
DPP 12 (dihexyl-50,5000-(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6- biphenyl]-4-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione).
tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl)bis([2,20-bithiophene]-5- CH2Cl2 and petroleum ether (2 : 1, v/v) as eluent gave a bright
carboxylate)). Using CH2Cl2 and petroleum ether (6 : 1, v/v) as yellow solid (203 mg, 95% yield), H NMR (500 MHz, CDCl3) d
1
eluent gave a dark blue crystalline solid (88 mg, 47% yield), 1H 7.90 (d, J ¼ 8.3 Hz, 4H), 7.56 (d, J ¼ 8.1 Hz, 4H), 3.77 (d, J ¼
NMR (500 MHz, CDCl3) d 8.92 (d, J ¼ 4.1 Hz, 2H), 7.73 (d, J ¼ 7.3 Hz, 4H), 1.47 (d, J ¼ 45.5 Hz, 2H), 1.25–1.15 (m, 48H), 0.86–
3.9 Hz, 2H), 7.41 (d, J ¼ 4.1 Hz, 2H), 7.28 (d, J ¼ 3.9 Hz, 2H), 4.31 0.80 (m, 12H); 13C NMR (126 MHz, CDCl3) d 162.60, 148.01,
(t, J ¼ 6.7 Hz, 4H), 4.04 (s, 4H), 1.93 (s, 2H), 1.76 (m, 4H), 1.39– 145.13, 143.19, 138.87, 136.97, 130.57, 129.32, 128.97, 128.87,
1.25 (m, 28H), 0.89 (dt, J ¼ 20.1, 7.1 Hz, 18H); 13C NMR (126 110.27, 45.35, 37.27, 31.88, 31.68, 31.29, 31.33, 29.87, 29.64,
MHz, CDCl3) d 161.85, 161.56, 142.25, 141.38, 136.62, 134.14, 29.52, 29.42, 29.35, 26.14, 26.08, 22.62, 14.09, 14.05; MALDI-
133.60, 129.55, 126.15, 125.19, 108.91, 65.64, 46.02, 39.30, TOF MS (m/z): [M]+ calcd for C62H74F10N2O2, 1069.2472; found,
31.42, 30.34, 29.69, 28.64, 28.58, 25.61, 23.69, 23.09, 22.53, 1069.2670; elemental analysis: calcd for C62H74F10N2O2, C,
14.03, 10.55; MALDI-TOF MS (m/z): [M]+ calcd for C52H68N2O6S4, 69.64; H, 6.98; N, 2.62%. Found: C, 69.56; H, 6.92; N, 2.64%.
945.3661; found, 944.8873; elemental analysis: calcd for
DPP 17 (6,60-(5,50-((2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tet-
52H68N2O6S4, C, 66.07; H, 7.25; N, 2.96%. Found: C, 66.10; H, rahydropyrrolo[3,4-c]pyrrole-1,4-diyl)bis(4,1-phenylene))bis(thio-
C
7.26; N, 2.89%.
phene-5,2-diyl))bis(2,5-bis(2-ethylhexyl)-3-(5-phenylthiophen-2-yl)
DPP 13 (50,5000-(2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahy- pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione)). Using CH2Cl2 and
dropyrrolo[3,4-c]pyrrole-1,4-diyl)bis(([2,20-bithiophene]-5-carbon- petroleum ether (4 : 1, v/v) as eluent gave a dark blue solid
itrile))). Using CH2Cl2 and petroleum ether (6 : 1, v/v) as eluent (324 mg, 95% yield, calculated from DPP 1d). 1H NMR
1
gave a dark blue crystalline solid (67 mg, 46% yield), H NMR (500 MHz, CDCl3) d 8.94 (s, 2H), 8.74 (s, 2H), 7.70 (d, J ¼ 8.0 Hz,
(500 MHz, CDCl3) d 8.89 (d, J ¼ 4.1 Hz, 2H), 7.58 (d, J ¼ 3.9 Hz, 4H), 7.52–7.45 (m, 8H), 7.35–7.29 (m, 8H), 7.13 (s, 2H), 4.05–3.95
2H), 7.41 (d, J ¼ 4.2 Hz, 2H), 7.30 (m, 2H), 3.96 (t, J ¼ 8.1 Hz, 4H), (m, 8H), 3.70–3.60 (m, 4H), 1.87–1.83 (m, 4H), 1.64 (s, 2H), 1.38–
1.60 (d, J ¼ 5.5 Hz, 2H), 1.25–1.10 (m, 16H), 0.93–0.85 (m, 12H); 1.25 (m, 32H), 1.10–0.99 (m, 16H), 0.90–0.80 (m, 24H), 0.77–0.70
13C NMR (126 MHz, CDCl3) d 161.46, 142.87, 139.53, 139.41, (m, 12H); 13C NMR (126 MHz, CDCl3) d 161.29, 161.16, 161.05,
138.36, 136.46, 130.32, 126.90, 124.67, 113.72, 109.24, 109.18, 149.61, 147.85, 140.03, 138.37, 137.32, 135.92, 134.72, 133.00,
46.03, 39.30, 30.30, 28.45, 23.65, 22.99, 14.04, 10.54; MALDI- 130.24, 129.77, 128.96, 128.86, 128.53, 127.91, 125.84, 125.04,
TOF MS (m/z): [M]+ calcd for C40H42N4O2S4, 739.0471; found, 124.78, 124.04, 109.31, 108.35, 107.75, 45.94, 44.36, 39.20,
739.3151; elemental analysis: calcd for C40H42N4O2S4, C, 65.01; 38.01, 30.36, 29.69, 28.66, 28.28, 23.77, 23.18, 23.09, 22.85,
H, 5.73; N, 7.58%. Found: C, 64.95; H, 5.71; N, 7.60%.
14.08, 13.93, 10.67, 10.46; MALDI-TOF MS (m/z): [M]+ calcd for
106H126N6O6S4, 1710.4471; found, 1710.3909; elemental anal-
DPP 14 (5,50-((2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetra
C
hydropyrrolo[3,4-c]pyrrole-1,4-diyl)bis(4,1-phenylene))bis(thio- ysis: calcd for C106H126N6O6S4, C, 74.52; H, 7.43; N, 4.92%.
phene-2-carbaldehyde)). Using CH2Cl2 and petroleum ether Found: C, 74.43; H, 7.40; N, 4.89%.
(7 : 1, v/v) as eluent gave a dark red crystalline solid (109 mg,
75% yield), 1H NMR (500 MHz, CDCl3) d 9.90 (s, 2H), 7.85 (d, J ¼
Acknowledgements
8.4 Hz, 4H), 7.75 (dd, J ¼ 10.9, 6.1 Hz, 6H), 7.46 (d, J ¼ 3.9 Hz,
2H), 3.77 (dd, J ¼ 7.1, 4.8 Hz, 4H), 1.25 (s, 2H), 1.10 (m, 16H), This work was supported by the NSFC (no. 21244008, 50990063,
0.78–0.71 (m, 12H); 13C NMR (126 MHz, CDCl3) d 182.73, 162.57, 51011130028, and 91233114). The work was also partly
152.54, 147.81, 143.28, 137.25, 135.19, 129.53, 129.09, 126.47, supported by the Fundamental Research Funds for the
124.99, 110.24, 45.06, 38.54, 30.32, 28.26, 23.77, 22.83, 13.93, Central Universities (2012QNA4025) and 863 Program (no.
10.42; MALDI-TOF MS (m/z): [M]+ calcd for C44H48N2O4S2, 2011AA050520).
732.9929; found, 733.1593; elemental analysis: calcd for
C
44H48N2O4S2, C, 72.10; H, 6.60; N, 3.82%. Found: C, 72.15;
H, 6.58; N, 3.81%.
DPP 15
Notes and references
(diethyl-5,50-((2,5-bis(2-ethylhexyl)-3,6-dioxo-
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J. Mater. Chem. A
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