Diindole-annulated naphthalene diimides: Synthesis and optical and electronic properties of syn - And anti -isomers

Article abstract of DOI:10.1021/jo402365s

Here we report a selective method for the core-extension of naphthalene diimide (NDI) with two annulated indole rings leading to carbazolo[2,3-b] carbazole diimides (CbDIs) with exclusive syn-connectivity based on a regioselective nucleophilic substitution reaction of Br₄-NDI with arylamines, followed by palladium-catalyzed intramolecular C-C coupling. The oxygen analogues of anti-CbDIs, namely anti-benzofurobenzofuran diimides (anti-BfDIs), were obtained from 2,6-Br₂-NDI and 2-bromophenol. The syn- and anti-isomers of CbDIs were unambiguously characterized by single-crystal X-ray analysis. The optical properties of the present core-enlarged NDIs were studied, revealing clear differences in the absorption characteristics of the syn- and anti-isomers of CbDI, on one hand, and CbDI vs BfDI derivatives, on the other hand. Cyclic voltammetry studies showed that the redox properties are dependent on the substituents at the CbDI-core and oxygen atom containing BfDIs are more prone to reduction than the respective nitrogen analogues CbDIs. Vacuum-processed organic field effect transistors reveal CbDI and BfDI derivatives with n-channel, p-channel, as well as ambient transport characteristics with mobility values up to 0.2 cm²/(V s).

Full text of DOI:10.1021/jo402365s

Article
pubs.acs.org/joc
Diindole-Annulated Naphthalene Diimides: Synthesis and Optical
and Electronic Properties of Syn- and Anti-Isomers
Sabin-Lucian Suraru, Christian Burschka, and Frank Wurthner*
̈
Universitat Wurzburg, Institut fur Organische Chemie & Center for Nanosystems Chemistry, Am Hubland, 97074 Wurzburg,
̈
̈
̈
̈
Germany
S
* Supporting Information
ABSTRACT: Here we report a selective method for the core-extension of naphthalene diimide (NDI) with two annulated
indole rings leading to carbazolo[2,3-b]carbazole diimides (CbDIs) with exclusive syn-connectivity based on a regioselective
nucleophilic substitution reaction of Br4-NDI with arylamines, followed by palladium-catalyzed intramolecular C−C coupling.
The oxygen analogues of anti-CbDIs, namely anti-benzofurobenzofuran diimides (anti-BfDIs), were obtained from 2,6-Br2-NDI
and 2-bromophenol. The syn- and anti-isomers of CbDIs were unambiguously characterized by single-crystal X-ray analysis. The
optical properties of the present core-enlarged NDIs were studied, revealing clear differences in the absorption characteristics of
the syn- and anti-isomers of CbDI, on one hand, and CbDI vs BfDI derivatives, on the other hand. Cyclic voltammetry studies
showed that the redox properties are dependent on the substituents at the CbDI-core and oxygen atom containing BfDIs are
more prone to reduction than the respective nitrogen analogues CbDIs. Vacuum-processed organic field effect transistors reveal
CbDI and BfDI derivatives with n-channel, p-channel, as well as ambient transport characteristics with mobility values up to 0.2
cm2/(V s).
thalene diimides (NDIs), have been developed as highly
powerful, air-stable n-type semiconductors due to their good
packing behavior and electron-poor character.18−20
INTRODUCTION
■
The extension of conjugated π-systems is a widely applied
approach in the fields of small molecule based organic
electronics and photovoltaics.1−5 This strategy leads to
molecules with desirable electronic characteristics such as
reduced band gap. Moreover, extension of aromatic systems is
often accompanied by an enhanced intermolecular overlap of
the π-systems in the bulk, improving electronic coupling
between the molecules and thus the charge transport.6 For
these reasons polycyclic aromatic compounds such as acenes7
have been emerged in the early stage of development as one of
the most important class of p-type organic semiconductor
materials. However, extension of the conjugated π-systems to
linearly fused acenes goes along with a lack of stability and
solubility of these compounds and thus several strategies have
been applied to circumvent such drawbacks by structural
modification. For example, the incorporation of heteroatoms in
to the polycyclic conjugated core leading to heteroacenes,8−14
and functionalization of peri-substituted acenes with bulky
silylethinyl groups15−17 were shown to be very promising in
this regard. During the last years, lower homologue rylene
diimides, in particular perylene diimides (PDIs) and naph-
Motivated by the aforementioned advancements during the
past few years, several synthetic strategies have been developed
to enlarge the π-core of NDIs, the latter being the smallest
acene diimides, leading to core-expanded acene21−23 and
heteroacene-like24−28 derivatives functionalized with diimide
moieties along the short axis of the molecules. Along this line,
sulfur-containing core-enlarged NDIs were introduced by Zhu
et al. as an outstanding class of solution-processable n-type
semiconductors.29−31 As one of the earlier examples of core-
extended NDIs, we reported in our previous communication a
carbazolo[2,3-b]carbazole-6,7:13,14-tetracarboxylic acid dii-
mide (CbDI) that exhibits ambipolar charge transport behavior
with good hole mobility (structure Ia in Chart 1).32 The core
enlargement of NDI was achieved by a one-pot, two-step
reaction of 2,6-dibromo-NDI (2,6-Br2-NDI) with 2-bromoani-
line. Recently, Wang et al. have reported a sulfur analogue of Ia
Received: October 24, 2013
Published: November 26, 2013
© 2013 American Chemical Society
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Article
be prone to intramolecular arylation by C−C coupling. Thus,
we have synthesized a series of 2,7-diphenylamino-3,6-
dibromo-NDIs 1a−f bearing different substituents in the
imide positions and on the phenylamino group by the
regioselective nucleophilic substitution reaction of Br4-NDIs
(R = DIPP, C8H17, C3H7) with the respective aniline derivatives
in chloroform or toluene. Indeed, the subsequent palladium-
catalyzed intramolecular C−C coupling of 1a−f afforded the
respective syn-CbDIs 2a−f (Scheme 1). The reaction of Br4-
NDI-C8H17 in chloroform with excess aniline (ca. 90 equiv)
afforded 1b selectively as the only disubstitution product within
2 h in a yield of 87%. NDI derivative 1a with a 2,6-
diisopropylphenyl (DIPP) group in the imide positions was
obtained by the same procedure in 82% yield. With 3- or 4-tert-
butylaniline the corresponding derivatives 1c and 1d were
obtained highly regioselectively (2,7-isomer) in 76% yield,
respectively. Substitution of Br4-NDI-C3H7 with 3-tert-butylani-
line gave NDI 1e, bearing the same substitution pattern at the
NDI core as in NDI 1c. For the reaction of Br4-NDI-C8H17
with electron-poor and less nucleophilic 3,5-bis(trifluoro-
methyl)aniline prolonged reaction time was required, and the
respective 2,7-diamino-NDI 1f was obtained after several days
of reaction in toluene at 70 °C in 81% yield. Subsequently, the
intramolecular cyclization of diaminodibromo-NDIs 1a−f to
the respective syn-CbDIs was performed with Pd(OAc)2 as a
catalyst and K2CO3 as base in DMF. A temperature of 100 °C
turned out to be sufficient for these reactions, and derivatives
2a−e were obtained after 1−1.5 h reaction time in 28−54%
yield. However, for the synthesis of CbDI 2f bearing CF3
groups a higher temperature (ca. 150 °C) is required.
For the purpose of comparative studies of molecular
properties of syn- and anti-isomers, we have also synthesized
the anti-CbDIs 3a,b. The one-pot reaction of 2,6-Br2-NDI
bearing 2,6-diisopropylphenyl substituents in the imide
positions with 2-bromoaniline in the presence of Pd(OAc)2
and K2CO3 in DMF afforded 3a in 13% yield (Scheme 2).32
The anti-CbDI derivative 3b with a branched alkyl chain in the
imide positions was synthesized in 10% isolated yield. It is
remarkable that in contrast to CbDI 3a, derivative 3b lacks of
good solubility despite bearing branched 2-ethylhexyl groups.
To assess the scope of this synthetic method for NDI-core
expansion, we have performed analogous annulation reactions
of 2,6-Br2-NDIs with 2-bromophenol as oxygen nucleophile
and obtained the benzofurobenzofuran diimides (BfDIs) 4a
and 4b with anti-connectivity in 16−35% isolated yields
(Scheme 2). Remarkably, in contrast to anti-CbDI 3a, anti-
Chart 1
(Ib in Chart 1), which was synthesized from the 2,6-distannyl-
NDI in three steps.33 Very recently, Takimiya et al. have
achieved the synthetic access to naphthodithiophene diimides, a
four-ring annulated analogue to Ib, by cyclization of a 2,6-
diethynyl-NDI in the presence of sodium sulfide.34 The
aforementioned examples represent core-enlarged NDIs with
an inversion symmetry and anti-connectivity of the hetero-
atoms to the NDI core. This constitution derives from the
readily accessible 2,6-regioisomer of 2,6-dibromonaphthalene
dianhydride (2,6-Br2-NDA) precursor.35 However, a selective
synthesis of syn-isomeric heteroatom-containing ring-annulated
NDIs of general structure II (shown in Chart 1) has not been
reported so far. The reason might be that an analogous route to
syn-isomers is apparently not very attractive because the
required symmetrically positioned 2,7-dihalogenated NDI
precursors are not easily accessible.36
Herein we present a novel synthetic method for hitherto
unknown core-diindole-annulated NDIs with syn-connectivity
(syn-CbDIs) based on highly regioselective nucleophilic
substitution of Br4-NDI at 2,7-positions with aniline,37 followed
by palladium-catalyzed intramolecular C−C coupling (Scheme
1). Furthermore, we have synthesized anti-CbDIs (Ia, Chart 1)
as well as oxygen analogues (Ic, Chart 1) and studied the
optical and electronic properties of anti- and syn-isomers in a
comparative manner.
RESULTS AND DISCUSSION
■
Synthesis. Our synthetic route to syn-CbDIs is based on
our recent observation that nucleophilic substitution of Br4-
NDIs with aniline leads with high regioselectivity to 2,7-
diphenylamino-3,6-dibromo-NDIs.37 Such NDI derivatives
possessing carbon−bromine bonds in the NDI core and
carbon−hydrogen bonds located at the core-bound phenyl-
amino group in the ortho-position to the nitrogen atom should
Scheme 1. Synthesis of syn-CbDIs 2a−f
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of aryl bromides on palladium is facilitated by the electron-
withdrawing groups, i.e., imide in the present case, and CH
activation is favored for electron-rich substituents, i.e., amino-
phenyl. Consequently, a deactivating effect is provoked by
electron-withdrawing CF3 groups during the above-mentioned
transformation of 1f to 2f.
Scheme 2. Synthesis of anti-CbDIs 3a,b and Their Oxygen
Analogues 4a and 4b and Tetraester 6
We further wanted to explore the possibility of subsequent
functionalization of parent CbDI, and thus investigated
exemplarily the chlorination of anti-CbDI 3a with N-
chlorosuccinimide (NCS) affording a mixture of di-, tri-, and
tetrachloro CbDIs (Scheme 3). 1H NMR analysis revealed that
the chlorination occurred exclusively at the CbDI-core and the
aromatic imide substituents remained intact.
The substitution pattern of the chlorinated compounds 7a−c
could be determined by NMR analysis and is discussed later
(vide infra). The TLC monitoring of the reaction indicated
successive product formation; thus the substitution first takes
place in the para-position of both carbazole amino groups,
followed by chlorination in the ortho-position. This is in
accordance with the well-established para- and ortho-directing
effect of amino groups in electrophilic aromatic substitution
reaction. A direct tetrachlorination of the syn-CbDI 2a with
NCS was also possible, exhibiting the same regioselectivity in
para- and ortho-positions to the amino groups (Scheme 4).
BfDI 4a with 2,6-diisopropylphenyl groups in imide positions
exhibits only poor solubility even in chlorinated solvents. The
solubility of 4b bearing an n-octyl group is deficient as well.
Interestingly, the present π-core expansion method is not
contingent on the presence of imide groups as the reaction of
2,6-dibromonaphthalene alkylester 5, which is accessible from
isomerically pure 2,6-Br2-NDA,38,39 with 2-bromoaniline
afforded the carbazolocarbazole 6 in 13% yield (Scheme 2).
A comparison of the ring-closure reaction of 2,7-
diphenylamino-3,6-dibromo NDIs 1a−f to syn and one-pot,
two-step reaction of 2,6-Br2-NDIs with 2-bromoaniline to anti-
CbDI derivatives (Scheme 1 and 2) reveals that the former
reaction can be performed under relatively milder conditions
(in DMF at 100 °C) than those for the latter reaction (in
refluxing DMF). Both cyclization reactions are formally of
identical nature comprising a C−C coupling between a metal-
activated aryl bromide and a CH-bond. However, in 2,7-
diphenylamino-3,6-dibromo NDIs 1a−f the bromine atom is
located on the electron-poor aromatic unit (NDI-core) and the
CH activation takes place at the electron-rich peripheral
phenylamino ring. For the anti-isomers, presumably an
intermediate is formed in situ by nucleophilic substitution of
2,6-Br2-NDI with 2-bromoaniline that bears the bromine atoms
on the phenylamino units, and hence, the situation is reversed.
The differences in the required reaction conditions for syn- and
anti-CbDI derivatives are in accordance with the generally
accepted mechanistic assumptions40,41 that oxidative addition
Scheme 4. Tetrachlorination of syn-CbDI 2a with NCS
Structural Assignment by 1H NMR Analysis. A common
feature in the 1H NMR spectra of all CbDIs (except 2f) as well
as BfDIs is a lowfield-shifted proton signal at around 9−10 ppm
(for spectra, see the Supporting Information). This signal can
be assigned to the H atoms in positions 1 and 8 for the anti-
CbDIs and to the H atoms in positions 1 and 12 for the syn-
CbDIs, respectively (Figure 1), since those protons are located
in the deshielded region of the anisotropy cone of the carbonyl
groups. A prerequisite for this deshielding effect is the
coplanarity of the extended core and the carbonyl groups. As
for the tetraester 6, this effect is much less pronounced and the
signal for the corresponding protons is found at 8.68 ppm. It is
Scheme 3. Chlorination of anti-CbDI 3a with NCS
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Figure 1. Structures of compounds 2a, 3a, and 6 with the positions and chemical shifts of the characteristic proton signals measured in CD2Cl2
marked.
Figure 2. Structure, chemical shift, and coupling constants of relevant protons of CbDIs (a) 2c,d and (b) 7a,c, determined by 1H NMR spectroscopy
in CD2Cl2 and CDCl3, respectively.
worthy of note that the loss of planarity in tetraester 6 also
affects a highfield shift of the NH protons, compared to those
of CbDIs at ca. 11.5 ppm due to the absence of the
intramolecular hydrogen bonding in former compound. The
lowfield shifted signal at around 9−10 ppm is helpful to
determine the substitution pattern of core-substituted CbDIs in
combination with the coupling pattern of the aromatic protons.
For instance, the syn-isomers 2c and 2d can be distinguished by
third and fourth chlorination took place at the ortho-position to
the amino group. Based on similar considerations the structure
of the tetrachloro syn-CbDI 8 could be assigned as well.
Structural Properties by Single-Crystal X-ray Analysis.
We could unambiguously assign the syn- and anti-connectivity
of indole moieties in the CbDI structure by single-crystal X-ray
analyses for compounds 3a, 2a, 2d, and 2e (see Figures 3, 4,
and S3−S6, Supporting Information). The single-crystal X-ray
analysis of CbDI 3a clearly reveals an anti-connectivity of the
carbazole nitrogen atoms to the NDI-core (Figure 3a). CbDI
3a crystallizes together with a toluene solvent molecule in a
monoclinic space group P21/c (Figures 3 and S3, Supporting
Information). The enlarged NDI-core shows nearly perfect
planarity with the biggest deviation observed for the carbonyl
groups in the 7 and 14 positions of the CbDI core with a
torsion angle of 2.9°. The proximity of the carbonyl groups to
the adjacent amino group implies the formation of an
intramolecular hydrogen bond, corroborated by the close N−
O distance of 2.69 Å. The coplanar phenyl groups in imide
3
1H NMR as the protons in 1 and 12 positions show either a J
4
or a J coupling, depending on the position of the tert-butyl
group (Figure 2a). More importantly, the constitution of the
chlorinated derivatives 7a−c could be assigned unambiguously
from the 1H NMR data. While for the core-unsubstituted CbDI
3a a doublet at 9.71 ppm with a 3J coupling of 7.3 Hz is found,
the dichlorinated compound 7a exhibits a doublet with a
4
smaller J coupling constant of 2.1 Hz, indicating chlorination
in para-position to the amino group (Figure 2b). The
tetrachlorinated compound 7c shows similar resonances at
4
9.72 and 7.75 ppm with a J coupling clearly showing that the
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structure clearly shows the syn-connectivity of the nitrogen
atoms of indole moieties. In contrast to its anti-isomer 3a, the
structure of the CbDI 2a π-scaffold is not planar since the imide
and naphthalene units are twisted. Conspicuously, the imide-
carbonyl groups adjacent to the secondary amino groups are
less twisted from planarity (torsion angles 5.3−8.1°) compared
to those on the opposite side (torsion angles 16.4−16.6°). This
partial planarization is apparently caused by the intramolecular
hydrogen bond. Moreover, the aromatic imide substituents are
not coplanar, comprising an angle of 38.6° (Figure S4,
Supporting Information). The packing motif of 2a is shown
in Figure 4b,c. For this syn-CbDI, two-dimensional stacks of the
nearly flat π-systems, resembling a brick stone arrangement, are
formed, which are separated by the bulky imide substituents.
The arising gaps between the 2,6-diisopropylphenyl groups are
filled by the dichloromethane molecules. Within the stack a
complete overlap of the enlarged NDI-core is prevented by the
isopropyl groups of the bulky imide substituent, leading to four
π-contacts to neighboring molecules for each CbDI. A more
pronounced overlap of the π-surfaces is observed for the
antiparallel neighbors, whereas the less intense π−π-interaction
limited to the outer benzene rings is found to the parallel
oriented neighboring CbDI molecules. The π−π distance was
determined to be 3.4−3.6 Å.
Figure 3. (a) Molecular structure with relevant torsion angles of anti-
CbDI 3a determined by single-crystal X-ray analysis (thermal
ellipsoids are set at 50% probability) and (b) packing motif with
alternating 3a and toluene in π-stacks. Disorder of toluene is shown.
In contrast to 2a, containing solvent inclusion of dichloro-
methane, for core-substituted CbDI 2d with n-octyl groups in
imide positions solvent-free crystals were obtained. The crystals
of core-substituted CbDIs 2d show a less distorted molecular
structure than 2a (Figures 4 and S5,6, Supporting Information).
Nevertheless, also for these molecules the imide moiety
adjacent to the amino groups is nearly planar, whereas the
opposite side deviates from planarity with torsion angles
around 6−7° for 2d. syn-CbDI 2d crystallizes in the monoclinic
space group P21 (Figures 4 and S5, Supporting Information).
The alkyl chain is oriented along the molecular short axis and is
extended perpendicularly to the π-surface. This facilitates an
intimate π-overlap between neighbors leading to a slip-stacked
arrangement of parallel molecules. The stacks are extended
along the b-axis and are assembled as pairs, enclosing an angle
of 71.2°. These pairs are isolated from each other by the n-octyl
groups (Figure S5b−d, Supporting Information) exhibiting a
one-dimensional packing motif. The single crystal obtained for
CbDI 2e contains ethyl acetate as solvent inclusion, lying
directly in the same plane as the CbDI molecule and forming a
hydrogen bond to the amino group (Figure S6, Supporting
Information). As in the case of 2d, the CbDI 2e forms one-
dimensional stacks with intimate π−π-overlap due to the
sterically less demanding n-propyl groups where antiparallel
molecules are stacked on top of each other with π−π distances
of 3.3 and 3.5 Å, respectively.
Optical Properties. The optical properties of the new core-
enlarged NDIs were investigated by UV−vis absorption
spectroscopy in dichloromethane, and the results are
summarized in Table 1. The UV−vis absorption spectra of
syn-CbDI 2a, anti-CbDI 3a, and anti-BfDI 4a, bearing 2,6-
diisopropylphenyl groups in imide positions, are shown for
comparison in Figure 5. anti-BfDI 4a exhibits an absorption
band in the visible region with a maximum at 474 nm and a
vibronic fine structure, causing the yellow color of this
chromophore in dichloromethane solution. In contrast, the
CbDI derivatives absorb strongly over a broad visible region
(ca. 400−660 nm). The replacement of oxygen atoms in anti-
BfDI by secondary amino groups leads to a new bathochromic
Figure 4. (a) Molecular structure with relevant torsion angles (thermal
ellipsoids are set at 50% probability), (b) packing behavior, and (c) π-
stacking in single crystals of CbDIs 2a (left) and 2d (right)
determined by X-ray analysis. For CbDI 2a dichloromethane was
found as solvent inclusion.
position are oriented perpendicular to the carbazolocarbazole
core. The packing motif is strongly determined by the toluene
molecule. Each solvent molecule is sandwiched by two CbDIs
exhibiting a close π−π distance of 3.32 Å forming one-
dimensional stacks separated by the imide groups (Figure 3b).
The measured single crystal of 2a contains dichloromethane
as solvent inclusion and crystallizes in the triclinic space group
P1 (Figures 4 and S4, Supporting Information). This crystal
̅
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with a maximum at 641 nm possessing a quantum yield of
5%.32
Table 1. Optical Absorption Data and Optical Band Gaps of
Core-Enlarged NDI Derivatives Measured in
Dichloromethane (10−5 M)
The UV−vis spectra of further syn-CbDIs 2b−e with
different substituents on the CbDI-core and n-octyl groups in
the imide positions reveal some interesting substituent effects
on the absorption properties of this new type of core-extended
NDIs (Figure S1c, Supporting Information). syn-CbDIs 2c and
2d bearing tert-butyl groups in the meta- and para-positions to
the amino groups show a slight bathochromic shift of the
intensive band (from 526 to 532 and 535 nm) compared to
that of respective H atom containing CbDI 2b. The less
intensive band which can be found at ca. 580 nm for both 2b
and 2c appears as a shoulder at ca. 600 nm for derivative 2d.
More striking is the strong blue-shift of the absorption
spectrum caused by the electron-withdrawing CF3 groups
located at the meta-positions to the amino group of syn-CbDI
2f with absorption maxima at 568 and 502 nm. Noteworthy, a
similar significant blue-shift of absorption maxima was also
observed for the correspondent NDI precursor 1f, whereas tert-
butyl groups provoke only small bathochromic shifts of
absorption bands for 1c and 1d (Figure S1e, Supporting
Information). Similarly to NDIs (Figure S1f, Supporting
Information), imide substituents of CbDIs do not attain any
considerable effect on their absorption properties. However, the
tetraester 6 that has the same aromatic core as CbDI 3a shows
less intense but strongly blue-shifted absorption bands at 500
and 400 nm, compared to those of 3a (see Table 1 and Figure
S1d, Supporting Information).
a
λmax
ε (M−1
cm−1
λmax
ε (M−1
cm−1
bandgap
(eV)
(nm)
)
(nm)
)
2a
2b
2c
2d
2e
2f
3a32
3b
4a
6
531
526
532
535
532
502
491
486
474
400
483
476
470
531
34300
34600
40600
31500
40700
26700
38600
34100
46200
27000
30000
30400
30000
28000
589
580
12400
11900
11500
9400
2.10
2.14
2.14
2.07
2.14
2.18
1.99
2.02
2.62
2.48
1.95
1.96
1.97
2.08
b
580
b
600
b
580
11500
13700
24200
20800
-
568
622
615
-
500
635
632
629
597
10100
19900
19800
20100
11600
7a
7b
7c
8
a
b
Calculated from the long wavelength absorption. A shoulder is
observed instead of a maximum.
We have also studied the optical properties of the chlorinated
products 7a−c and 8 of anti-CbDI 3a and syn-CbDI 2a,
respectively. For the di-, tri-, and tetrachloro anti-CbDIs 7a−c,
a bathochromic shift up to 13 nm of the absorption band at
longer wavelength was observed compared to that of the parent
CbDI 3a, whereas the absorption band at shorter wavelength is
hypsochromically shifted (Figure S1b, Supporting Information,
and Table 1). The tetrachlorinated syn-CbDI 8 exhibits only a
slight red-shift of 8 nm of the less intensive band at higher
wavelength in comparison to that of its parent compound 2a.
However, the highest intensity band remains unchanged at 531
nm.
Figure 5. UV−vis absorption spectra of anti-BfDI 4a (yellow), syn-
CbDI 2a (red), and anti-CbDI 3a32 (green) in dichloromethane (10−5
M).
Redox and Transistor Properties. Next, we investigated
the redox potentials of the core-enlarged NDIs by cyclic
voltammetry in dry dichloromethane with ferrocene as an
internal standard (Table 2, Figures 6 and S2, Supporting
Information). The results are collected in Table 2, and the CVs
of syn-CbDI 2a, anti-BfDI 4a, and carbazolocarbazole tetraester
6 are shown in Figure 6 as representative examples for
comparison (for CVs of other compounds, see Figure S2,
Supporting Information). As the data in Table 2 reveal, only the
reduction processes are reversible for CbDI and BfDI
derivatives while the oxidation waves are either irreversible or
even outside of the accessible range of our electrolyte system
(>1.2 V vs Fc/Fc+).
absorption band with a maximum at 622 nm for anti-CbDI 3a
in addition to the blue-shifted band with a maximum at 491 nm,
which is similar to the absorption band of anti-BfDI derivate 4a.
The occurrence of these two bands provokes, similar as for
chlorophylls, the green color of 3a solutions. Interestingly, for
the corresponding syn-isomer CbDI 2a the two bands
apparently overlap resulting in one broad band with local
maxima at 589 and 531 nm, the latter possessing the highest
intensity. The solution of 2a in dichloromethane is accordingly
red in color. Noteworthy, the annulation evokes a different
absorption behavior than it can be observed for core-
disubstituted 2,6-diphenylamino-NDI derivatives, exhibiting a
single broad absorption band at 600 nm.35 Moreover, the
emission properties of these two new derivatives 2a and 4a
were investigated, and the fluorescence spectra are shown in
Figure S1a (Supporting Information), along with that of anti-
CbDI 3a32 for comparison. For anti-BfDI 4a, a fluorescence
quantum yield of 19% and an emission band maximum at 510
nm was observed, while the emitting CbDI 2a (Φfl = 1%)
exhibits an emission maximum at 622 nm. The emission band
of the corresponding anti-isomer 3a is bathochromically shifted
syn-CbDI 2a shows indeed reduction potentials E1/2 = −1.11
and −1.54 V very similar to those of its anti-isomer 3a (E1/2
=
−1.07 and −1.49 V),32 revealing that the structural isomers
have no significant influence on the reduction behavior of these
core-extended NDIs. As expected, the replacement of amino
groups in CbDI 3a by oxygen resulted in higher (less negative)
reduction potentials for anti-BfDI 4a with E1/2 values of −0.94
and −1.42 V, which can be attributed to the lower donor
character of oxygen compared to nitrogen. For the
carbazolocarbazole derivative 6, where the imide groups are
133
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Article
or by replacing the amino group with oxygen (Table 2).
Toward a more comprehensive picture, we further calculated
the frontier molecular orbitals and their energy for syn- and
anti-CbDIs 2a and 3a as well as of the anti-BfDI 4a by DFT
calculations (B3-LYP). For simplicity, methyl groups instead of
the 2,6-diisopropylphenyl group in the imide positions were
used (for details, see Tables 3 and S1−S3, Supporting
Table 2. Redox Properties of Core-Enlarged NDIs
Determined by Cyclic Voltammetry (vs Fc/Fc+; 100 mV s−1;
TBAHFP 0.1 M) and Calculated LUMO Energy
a
Red2
Red1
E1/2
(V)
E1/2
(V)
EOx1 (V)
ε(LUMO) (eV)
b
2a
2b
2c
2d
2f
3a32
4a
6
−1.54
−1.50
−1.56
−1.56
−1.27
−1.49
−1.42
−1.96
−1.38
−1.35
−1.30
−1.35
−1.11
−1.15
−1.21
−1.19
−0.88
−1.07
−0.94
−1.74
−0.94
−0.90
−0.85
−0.90
1.15
−3.69
−3.74
−3.59
−3.61
−3.92
−3.73
−3.86
−3.06
−3.86
−3.90
−3.95
−3.90
b
1.06
b
1.05
b
1.02
Table 3. Calculated FMOs of anti-BfDI 4a, anti-CbDI 3a,
and syn-CbDI 2a and the Corresponding Energy Level ε
c
>1.2
b
a
1.11
Determined by the B3-LYP-DFT Method
c
>1.2
0.73
c
7a
7b
7c
8
>1.2
c
>1.2
c
>1.2
c
>1.2
a
Calculated with a potential of −4.8 eV for Fc/Fc+ against the vacuum
level:42 ε(LUMO) = −4.8 eV−E1/2
oxidation potential could not been determined because it is beyond
.
Peak potential. The
b
c
Red1
the accessible window of our electrolyte system.
a
For simplicity, methyl groups in the imide positions were used for
calculations.
Information). According to these calculations, LUMO gas-
phase energies are about 0.2 eV higher than those obtained
from the CV data which can be explained in terms of neglected
solvent effects. The trend observed for the energy levels based
on CV experiments could also be found for the calculated
values, showing for the anti-BfDI derivative a higher LUMO
level of −3.68 eV than for syn- and anti-CbDI with values
around −3.48 and −3.52 eV, respectively. Moreover, the anti-
BfDI derivative has a significantly lower HOMO level of −6.55
eV compared to syn- and anti-CbDI with energies of −6.02 and
−5.91 eV, respectively, as reflected by the larger optical band
gap for the anti-BfDI derivative and the absence of an oxidation
wave in our accessible electrochemical window. For all three
systems, the HOMO is delocalized over the whole enlarged
NDI-core, whereas the LUMO remains localized on the parent
NDI unit resembling a typical LUMO of NDI derivatives.43 We
consider this last point as very important because the more
widespread delocalization of the HOMO increases the chance
for close contacts between HOMO orbitals of neighboring
molecules in the bulk material compared to contact between
LUMOs.32 Therefore, larger transfer integrals are expected for
charge transport within the HOMO manifold leading to higher
p-mobility.
Figure 6. Cyclic voltammograms of anti-BfDI 4a (yellow), syn-CbDI
2a (red), and tetraester 6 (black) measured in dichloromethane by
using Fc/Fc+ couple as an internal standard (scan rate 100 mV s−1;
supporting electrolyte TBAHFP).
replaced by the less electron-withdrawing and less conjugated
ester moieties, the redox potentials are shifted markedly to
more negative values of −1.74 and −1.96 V. For this compound
even a reversible oxidation was observed at 0.73 V
corroborating the more electron-rich character of this π-scaffold
where the four carbonyl groups are rotated out of plane.
Within the series of CbDIs bearing different substituents at
the carbazole rings, electron-withdrawing groups make the
corresponding derivatives more prone to reduction. Thus, the
functionalization of anti-isomer 3a with two, three, or four
chlorine atoms to CbDI 7a, 7b, and 7c, respectively, provokes a
gradual increase of the reduction potentials (less negative
values) from −1.07 and −1.49 V for 3a to −0.94 and −1.38 V
for 7a to −0.85 and −1.30 V for 7c. A similar effect was also
observed for the tetrachlorinated syn-CbDI 8 with reduction
potentials of −0.90 and −1.35 V corresponding to shifts of 0.21
and 0.19 V compared to those of parent syn-CbDI 2a. A similar
effect as provided by four chlorine substituents is also given by
four CF3 groups in syn-CbDI 2f, which shows reduction
potentials at −0.88 and −1.27 V.
In our previous communication,32 we could indeed
demonstrate good hole and rather low electron mobility for
anti-CbDI 3a in organic thin-film transistors (TFTs) and
rationalized these results on the basis of good intermolecular
HOMO overlap directed by the steric demand of the bulky 2,6-
diisopropylphenyl substituent in imide position, which on the
other hand prohibits close spatial contacts between the LUMOs
of neighboring molecules. Our preliminary results on the field
effect mobilities44 of our so far investigated new core-enlarged
NDI derivatives show that the corresponding syn-CbDIs 2a,
along with several other derivatives, are good organic
The reduction potentials discussed above suggest that the
LUMO level of CbDI derivatives can be tuned from ca. −3.7
eV down to nearly −4.0 eV with electron-withdrawing groups
134
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Article
semiconductors as well (Table S4, Supporting Information).
The syn-isomer 2a, whose bulky 2,6-diisopropylphenyl imide
substituent direct the molecules’ packing into layer structures
with slipped π−π-contact surfaces (Figure 4c), shows a hole
mobility in the same range (0.2 cm2/(V s)) as previously
reported for its anti-congener.32 Like for 3a, we could also
observe n-channel transport for OTFTs of 2a with one to 2
orders of magnitude lower mobility that complies with our
expectations based on the slipped packing arrangement in the
crystals, which owing to the transversal offset of the NDI cores
cannot provide significant LUMO−LUMO overlap (Figure 4c).
Whereas for CbDIs 2a and 3a32 ambipolar transport
properties with superior p-channel transport was observed,
anti-BfDI 4a with the same imide substituent (DIPP) shows
only n-type behavior with appreciable mobility up to 0.06 cm2/
(V s). This observation is in good accordance with the lowered
FMO levels (Tables 2 and S1, Supporting Information) of the
oxygen analogue, where n-type behavior is now provided by the
low LUMO level close to −3.9 eV while the too deep lying
HOMO level disfavors charge injection for p-transport from the
gold electrode. A similar trend is also found for syn-CbDIs 2b
and 2f with n-octyl groups in imide position. The former
derivative, and similarly the tert-butyl substituted derivatives 2c
and 2d, exhibits only p-type behavior with hole mobility of 10−2
cm2/(V s), whereas for CF3-substituted derivative 2f with its
low LUMO level of −3.92 eV only n-type behavior with
electron mobility of up to 10−3 cm2/(V s) was measured. With
regard to our transistor measurements, we have to point out,
however, that we could not achieve the high quality thin films
for several of our new molecules so far, which obviously makes
a comparison of the given mobility values in terms of HOMO−
HOMO or LUMO−LUMO contacts impossible. Unfortu-
nately, we are as yet not in the position to carry out the
measurements under inert atmosphere but only under ambient
conditions, where only for very densely packed molecules in
closed multilayers can n-channel transport be achieved for
molecules with a LUMO level above a value of around −3.9
eV45 (earlier work even considered −4.3 eV as the upper
limit).18 Obviously 2a and 3a with rather high LUMO levels of
−3.7 eV have to exhibit such densely packed layers that enable
ambient n-channel operation despite the absence of commonly
applied fluoroalkyl chains to repel the penetration of humidity.
Accordingly, more in-depth studies on the utilization of CbDI
and BfDI compounds in transistor devices are strongly
motivated and will be addressed in our future research.
synthesized core-extended NDI derivatives are highly promis-
ing organic semiconductors whose HOMO and LUMO levels
can be tuned toward p- or n-channel transport.
EXPERIMENTAL SECTION
■
Materials and Methods. 2,6-Dibromonaphthalenetetracarboxylic
dianhydride (2,6-Br2-NDA),35 N,N′-bis(2,6-diisopropylphenyl)-2,6-
dibromonaphthalenetetracarboxylic acid diimide (2,6-Br2-NDI-
DIPP),46 N,N′-bis(2-ethylhexyl)-2,6-dibromonaphthalenetetracarbox-
ylic acid diimide (2,6-Br2-NDI-Ethex),47 N,N′-di-(n-octyl)-2,3,6,7-
tetrabromonaphthalenetetracarboxylic acid diimide (Br4-NDI-
C8H17),48 and N,N′-bis(2′,6′-diisopropylphenyl)-2,3,6,7-tetrabromo-
naphthalenetetracarboxylic acid diimide (Br4-NDI-DIPP)49 were
synthesized according to the literature procedures. Aniline was
distilled under argon and stored under exclusion of light. DMF was
dried over P2O5 and stored under argon and exclusion of light. All
other reagents and solvents were obtained from commercial suppliers
and purified and dried according to standard procedures.50 Column
chromatography was performed on silica gel (particle size 0.040−0.063
mm). A preparative recycling GPC with 2H + 2.5H columns was used
for further purification. Solvents for spectroscopic studies were of
spectroscopic grade and used as received. For cyclic voltammetry
measurements, a standard commercial electrochemical analyzer with a
three-electrode single-compartment cell was used. Dichloromethane
(HPLC grade) was dried over calcium hydride under argon and
degassed before use. The supporting electrolyte tetrabutylammonium
hexafluorophosphate (TBAHFP) was prepared according to the
literature51 and recrystallized from ethanol/water. The measurements
were carried out in dichloromethane at a concentration of <10−4
M
with ferrocene (Fc) as an internal standard for the calibration of the
potential. A Ag/AgCl reference electrode was used. A Pt disc and a Pt
wire were applied as working and auxiliary electrodes, respectively.
UV−vis measurements were performed in a conventional quartz cell
(light pass 10 mm) on a standard, commercial spectrometer.
Fluorescence quantum yields were determined under dilute conditions
in CH2Cl2 (<10−6 M) versus N,N′-bis(2,6-diisopropylphenyl)-
1,6,7,12-tetraphenoxyperylene-3,4:9,10-tetracarboxylic acid bisimide
(Φfl = 0.96 in CHCl3)52 or N,N′-bis(2,6-diisopropylphenyl)-3,4:9,10-
tetracarboxylic acid bisimide (Φfl = 1 in CHCl3).53 1H and 13C spectra
were recorded in CD2Cl2 or CDCl3 on a 400 or 600 MHz
spectrometer. Residual undeuterated solvent was used as internal
standard. High-resolution mass spectra were measured by ESI-TOF
and EI experiments. The measurements of single crystals of 2a, 2d, and
2e were performed on a diffractometer with a CMOS APS detector
under monochromated Cu Kα radiation. The crystal data of 3a were
collected on a diffractometer with a CCD area detector and graphite-
monochromated Mo Kα radiation. The structures were solved using
direct methods, refined with the SHELX software packag,e54 and
expanded using Fourier techniques. All non-hydrogen atoms were
refined anisotropically. Hydrogen atoms were included in structure
factors calculations. All hydrogen atoms were assigned to idealized
geometric positions.
CONCLUSION
■
We have synthesized a series of core-enlarged NDI derivatives
consisting of six annulated rings bearing heteroatoms. In
particular, a selective synthetic route to unknown syn-CbDIs is
presented, completing the series of core-extended NDIs with
annulated indole moieties. For further tuning the electronic
properties, we have synthesized core-functionalized CbDIs,
either starting from precursors containing the desired func-
tional groups or by subsequent functionalization of the parent
CbDI, particularly by chlorination. Furthermore, oxygen
analogues to the anti-CbDIs with benzofurofuran units were
synthesized. Single-crystal X-ray analyses confirmed unambig-
uously the syn- and anti-connectivity in CbDI derivatives and
revealed the influence of imide substituents on the π-stacking of
these compounds in the solid state. The optical and
electrochemical properties of CbDI derivatives are shown to
be dependent on their structural features. The hereby
N,N′-Bis(2′,6′-diisopropylphenyl)-2,7-dibromo-3,6-diphenylami-
no-1,4,5,8-naphthalenetetracarboxylic Acid Diimide (1a). To a
solution of Br4-NDI-DIPP (149 mg, 0.165 mg) in chloroform (50 mL)
was added aniline (1.8 mL). The solution was refluxed for 40 min, the
solvent was removed under reduced pressure, and the residue was
purified by column chromatography (dichloromethane/pentane 1:1)
yielding a dark blue solid (162 mg, 82%). Mp: 285−288 °C. 1H NMR
(400 MHz, CD2Cl2): 11.84 (s, 2H, NH) 7.53−7.47 (m, 2H), 7.37−
7.31 (m, 8H), 7.16 (t, 3J = 7.6 Hz, 2H), 7.07 (d, 3J = 7.6 Hz, 4H), 2.77
3
3
3
(sept, J = 6.8 Hz, 2H), 2.65 (sept, J = 6.8 Hz, 2H), 1.18 (d, J = 6.8
Hz, 12H), 1.11 (d, 3J = 6.8 Hz, 12H). 13C NMR (101 MHz, CD2Cl2):
165.3, 161.7, 151.6, 146.3, 146.1, 141.9, 131.3, 131.0, 130.2, 129.5,
128.5, 125.1, 124.64, 124.56, 122.1, 119.8, 119.0, 108.3, 29.8, 29.6,
24.1, 24.0. HRMS (ESI, acetonitrile/chloroform, pos mode): m/z
925.1960 [M + H]+, calcd for C50H47Br2N4O4 925.1959. UV−vis
(CH2Cl2): λmax/nm (ε/M−1 cm−1) = 570 (23500).
135
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Article
N,N′-Di(n-octyl)-2,7-dibromo-3,6-diphenylamino-1,4,5,8-naph-
thalenetetracarboxylic Acid Diimide (1b). To a solution of Br4-NDI-
C8H17 (170 mg, 0.211 mmol) in chloroform (50 mL) was added
aniline (1.8 mL) was added. The solution was refluxed for 2 h, the
solvent was removed under reduced pressure, and the residue was
purified by column chromatography (dichloromethane/pentane 1:1)
yielding a dark blue solid (153 mg, 87%). The product obtained by an
alternative procedure was previously described and characterized.37
N,N′-Di(n-octyl)-2,7-dibromo-3,6-di(3-tert-butylphenylamino)-
naphthalenetetracarboxylic Acid Diimide (1c). To a solution of Br4-
NDI-C8H17 (144 mg, 0.179 mmol) in chloroform (10 mL) was added
3-tert-butylaniline (0.2 mL, 1.26 mmol). The solution was refluxed for
45 min, the solvent was removed under reduced pressure, and the
residue was purified by column chromatography (dichloromethane/
pentane 1:1) yielding a dark blue solid (129 mg, 76%). Mp: 135−137
°C. H NMR (400 MHz, CDCl3): 12.09 (s, 2H, NH), 7.25 (dd, J =
7.8 Hz, 2H), 7.18 (ddd, 3J = 7.8 Hz, 4J = 1.6 Hz, 4J = 1.0 Hz, 2H), 7.07
(dd, 4J = 1.8 Hz, 2H), 6.82 (ddd, 3J = 7.8 Hz, 4J = 2.2 Hz, 4J = 1.0 Hz,
2H), 4.20 (t, 3J = 7.7 Hz, 2H), 4.15 (t, 3J = 7.7 Hz, 2H), 1.79−1.67 (m,
4H), 1.47−1.17 (m, 38H), 0.90−0.82 (m, 6H). 13C NMR (101 MHz,
CDCl3): 164.7, 161.1, 152.5, 151.06, 141.2, 128.81, 128.79, 127.2,
121.8, 118.8, 118.7, 118.6, 118.5, 107.7, 42.4, 41.4, 34.9, 31.9, 31.4,
29.8, 29.44, 29.39, 29.34, 28.1, 27.9, 27.4, 27.3, 22.77, 22.75, 14.23,
14.21. HRMS (ESI, acetonitrile/chloroform, pos mode): m/z
941.3216 [M + H]+ calcd for C50H63Br2N4O4 941.3211. UV−vis
(CH2Cl2): λmax/nm (ε/M−1 cm−1) = 573 (22100).
N,N′-Di-(n-octyl)-2,7-dibromo-3,6-di(4-tert-butylphenylamino)-
1,4,5,8-naphthalenetetracarboxylic Acid Diimide (1d). To a solution
of Br4−NDI-C8H17 (199 mg, 0.247 mg) in chloroform (30 mL) 4-tert-
butylaniline (0.1 mL, 0.63 mmol) was added. The solution was
refluxed for 3 h 15 min, the solvent was removed under reduced
pressure and the residue was purified by column chromatography
(dichloromethane/pentane 1:1) yielding a dark blue solid (177 mg,
76%); mp 205−206 °C. 1H NMR (400 MHz, CDCl3): 12.0 (bs, 2H),
7.37−7.30 (m, 4H), 6.99−6.93 (m, 4H), 4.24−4.08 (m, 4H), 1.82−
1.62 (m, 4H), 1.45−1.17 (m, 38H), 0.92−0.82 (m, 6H). 13C NMR
(101 MHz, CDCl3): 164.6, 161.1, 151.3, 147.9, 139.1, 128.8, 126.9,
126.2, 121.3, 118.9, 118.5, 107.7, 42.5, 42.3, 34.6, 31.9, 31.5, 29.4, 29.3,
28.1, 27.9, 27.4, 27.3, 22.8, 22.7, 14.22, 14.21. HRMS (ESI,
acetonitrile/chloroform, pos mode): m/z 941.3209 [M + H]+, calcd
for C50H63Br2N4O4: 941.3211. UV−vis (CH2Cl2): λmax/nm (ε/M−1
cm−1) = 575 (22600).
1.85−1.70 (m, 4H), 1.31 (s, 9H), 1.02 (t, 3J = 7.4 Hz, 3H), 1.01 (t, 3J
= 7.4 Hz, 3H). 13C NMR (101 MHz, CDCl3): 164.8, 161.1, 152.5,
151.1, 141.2, 128.8, 127.2, 121.8, 118.81, 118.76, 118.6, 107.7, 43.8,
42.8, 34.9, 31.4, 21.4, 21.2, 11.7, 11.6. HRMS (ESI, acetonitrile/
chloroform, pos mode): m/z 801.1650 [M + H]+, calcd for
C40H43Br2N4O4 801.1646. UV−vis (CH2Cl2): λmax/nm (ε/M−1
cm−1) = 573 (23100).
N,N′-Di(n-octyl)-2,7-bis((3,5-bis(trifluormethyl)phenyl)amino)-
3,6-dibromo-1,4,5,8-naphthalenetetracarboxylic Acid Diimide (1f).
To a solution of Br4-NDI-C8H17 (72.3 mg, 89.8 μmol) in toluene (5
mL) was added 3,5-bis(trifluoromethyl)aniline (0.2 mL, 1.2 mmol).
The solution was stirred at 70 °C for 4 d, and a second portion of the
amine (0.1 mL, 0.6 mmol) was added. After a further 2 d, the solvent
was removed under reduced pressure and the residue was purified by
column chromatography (dichloromethane/pentane 1:4) yielding a
1
3
1
red solid (80.6 mg, 81%). Mp: 192−196 °C. H NMR (400 MHz,
CDCl3): 12.00 (s, 2H), 7.63 (s, 2H), 7.38 (s, 4H), 4.26−4.17 (m, 4H),
1.82−1.68 (m, 4H), 1.47−1.19 (m, 20H), 0.92−0.81 (m, 6H). 13C
NMR (101 MHz, CDCl3): 164.6, 160.4, 149.6, 143.1, 132.8 (2J(C,F) =
34 Hz), 128.1, 127.4, 123.2 (1J(C,F) = 275 Hz), 120.65, 120.62,
120.59, 117.6, 110.0, 42.8, 41.9, 31.91, 31.89, 29.9, 29.4, 29.34, 29.30,
28.1, 27.8, 27.32, 27.29, 22.8, 22.7, 14.21, 14.17. HRMS (ESI,
acetonitrile/chloroform, pos mode): m/z 1101.1457 [M + H]+, calcd
for C46H43Br2F12N4O4 1101.1454. UV−vis (CH2Cl2): λmax/nm (ε/
M−1 cm−1) = 535 (23900).
N,N′-Bis(2,6-diisopropylphenyl)-5H,8H-carbazolo[2,3-b]-
carbazole[6,7:13,14]tetracarboxylic Acid Diimide (2a). NDI 1a (76.2
mg, 82.2 μmol), K2CO3 (22.8 mg, 0.165 mmol), and Pd(OAc)2 (5.4
mg, 26 μmol) were placed under argon, and dry DMF (5 mL) was
added. The reaction mixture was stirred for 60 min at 100 °C. After
removal of the solvent under reduced pressure, the residue was
purified by column chromatography (dichloromethane/pentane 1:1)
yielding a dark red solid (20.8 mg, 33%). Mp: >400 °C. 1H NMR (400
MHz, CD2Cl2): δ = 11.4 (s, 2H), 9.57 (dd, 3J = 8.16 Hz, 4J = 0.76 Hz,
3
2H), 7.73−7.66 (m, 4H), 7.66−7.57 (m, 2H), 7.49 (d, J = 7.6 Hz,
2H), 7.46 (d, 3J = 7.6 Hz, 2H), 7.41−7.37 (m, 2H), 2.98 (sept, 3J = 6.8
Hz, 2H), 2.87 (sept, 3J = 6.8 Hz, 2H), 1.22 (d, 3J = 6.8 Hz, 12H), 1.20
3
(d, J = 6.8 Hz, 12H).13C NMR (100 MHz, CD2Cl2): 166.0, 164.9,
146.71, 146.66, 144.5, 144.1, 132.0, 131.0, 130.9, 130.20, 130.15,
130.0, 128.8, 125.8, 124.8, 124.6, 122.5, 122.1, 121.6, 118.8, 111.8,
103.3, 29.8, 29.7, 24.2, 24.1. HRMS (ESI, acetonitrile/chloroform, pos
mode): m/z 765.3437 [M + H]+, calcd for C50H45N4O4 765.3435.
UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 589 (12400), 531
N,N′-Di(n-propyl)-2,3,6,7-tetrabromo-1,4,5,8-naphthalenetetra-
carboxylic Acid Diimide. Br4-NDA (3.0 g, 5.1 mmol) and n-
propylamine (1.3 mL, 16 mmol) were refluxed in acetic acid (40
mL) for 40 min. After addition of a second portion on amine (0.6 mL,
7 mmol), the mixture was refluxed for further 20 min and poured into
water (150 mL). The resulting precipitate was filtered off and dried.
Then it was suspended in dry toluene (200 mL), and PBr3 (3 mL) was
added. The mixture was refluxed for 8 h, and the solvent was removed
under reduced pressure. The residue was dissolved in dichloromethane
(60 mL) and washed with water (2 × 50 mL), and the organic phases
were combined. After evaporation of solvent, the crude product was
purified by column chromatography (dichloromethane/pentane 1:1)
(34300). Fluorescence (CH2Cl2, λex = 516 nm): λmax = 622 nm; Φfl =
Red2
1%. CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2
E1/2
= −1.54 V,
Red1
= −1.11 V, EpOx(X/X+) = 1.15 V.
N,N′-Di(n-octyl)-5H,8H-carbazolo[2,3-b]carbazole[6,7:13,14]-
tetracarboxylic Acid Diimide (2b). NDI 1b (153 mg, 0.184 mmol),
K2CO3 (102 mg, 0.738 mmol), and Pd(OAc)2 (14 mg, 62 μmol) were
placed under argon, and dry DMF (10 mL) was added. The reaction
mixture was stirred for 80 min at 100 °C. After removal of the solvent
under reduced pressure, the residue was purified by column
chromatography (chloroform/hexane 1:1) yielding a dark red solid
1
(35 mg, 28%). Mp: 273−274 °C. H NMR (400 MHz, CDCl3): 11.1
1
3
3
yielding a yellow crystalline solid (89 mg, 3%). Mp: 338−340 °C. H
(s, 2H, NH), 9.51 (d, J = 8.4 Hz, 2H), 7.55 (t, J = 7.8 Hz, 2H),
7.43−7.32 (m, 4H), 4.35−4.20 (m, 4H), 1.92−1.78 (m, 4H), 1.52−
1.19 (m, 20H), 0.89 (t, 3J = 6.9 Hz, 6H). 13C NMR (151 MHz,
CDCl3): 163.3, 163.8, 143.5, 143.3, 130.4, 129.8, 127.6, 124.0, 121.84,
121.77, 121.3, 117.2, 111.2, 102.2, 41.6, 40.4, 32.03, 32.00, 29.59,
29.58, 29.48, 29.45, 28.40, 28.35, 27.54, 27.50, 22.83, 22.81, 14.3.
HRMS (APCI, acetonitrile/chloroform 1:1, pos mode): m/z 669.3434
NMR (400 MHz, CD2Cl2): 4.24−4.12 (m, 4H), 1.86−1.76 (m, 4H),
1.04 (t, 3J = 7.4 Hz, 6H). 13C NMR (101 MHz, CDCl3): 160.0, 135.8,
126.8, 125.8, 44.5, 21.5, 11.6. HRMS (ESI, acetonitrile/chloroform,
pos mode): m/z 662.7757 [M + H]+, calcd for C20H15Br4N2O4
662.7760. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 425 (13800).
N,N′-Di(n-propyl)-2,7-dibromo-3,6-di(3-tert-butylphenylamino)-
1,4,5,8-naphthalenetetracarboxylic Acid Diimide (1e). To a solution
of Br4-NDI-C3H7 (81.1 mg, 0.122 mmol) in chloroform (10 mL) was
added 3-tert-butylaniline (0.14 mL, 0.88 mmol). The solution was
refluxed for 2 h, the solvent was removed under reduced pressure, and
the residue was purified by column chromatography (dichloro-
methane/pentane 4:1) yielding a dark blue solid (85 mg, 87%). Mp:
[M + H]+, calcd for C42H45N4O4 669.3435. UV−vis (CH2Cl2): λmax
/
nm (ε/M−1 cm−1) = 580 (11900), 526 (34600). CV (CH2Cl2, 0.1 M
TBAHFP, vs Fc/Fc+): E1/2Red2 = −1.50 V, E1/2Red1 = −1.15 V, EpOx(X/
X+) = 1.06 V.
N,N′-Di(n-octyl)-5H,8H-3,10-di-tert-butylcarbazolo[2,3-b]-
carbazole[6,7:13,14]tetracarboxylic Acid Diimide (2c). NDI 1c (99.0
mg, 0.105 mmol), K2CO3 (29.0 mg, 0.210 mmol), and Pd(OAc)2 (7.0
mg, 31 μmol) were placed under argon, and dry DMF (7 mL) was
added. The reaction mixture was stirred for 60 min at 100 °C. After
1
3
263 °C. H NMR (400 MHz, CDCl3): 12.1 (s, 2H), 7.25 (t, J = 7.8
Hz, 2H), 7.18 (d, 3J = 7.8 Hz, 2H), 7.07 (t, 4J = 2.0 Hz, 2H), 6.83 (d,
3J = 8.0 Hz, 2H), 4.24−4.16 (m,2H), 4.16−4.08 (m, 2H) (m, 4H),
136
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The Journal of Organic Chemistry
Article
Red2
Red1
removal of the solvent under reduced pressure, the residue was
(CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2
−0.88 V.
= −1.27 V, E1/2
=
purified by column chromatography (dichloromethane/pentane 1:1)
1
yielding a dark red solid (30 mg, 37%). Mp: 353−355 °C. H NMR
N,N′-Bis(2,6-diisopropylphenyl)-5H,12H-carbazolo[2,3-b]-
carbazole[6,7:13,14]tetracarboxylic Acid Diimide (3a). 2,6-Br2-NDI-
DIPP (60.0 mg, 80.6 μmol), 2-bromoaniline (38.8 mg, 0.226 mmol),
Pd(OAc)2 (4.0 mg, 17.8 μmol), PCy3 (11.0 mg, 35.4 μmol), and
Cs2CO3 (52.2 mg, 16.2 μmol) were placed in dry dimethylacetamide
(5 mL) under argon atmosphere and stirred for 1 h at 125 °C and an
additional 1 h at 175 °C. The solvent was removed under reduced
pressure, and the residual crude product was purified by column
chromatography (dichloromethane/pentane 1:1) and recycling GPC
yielding a dark green solid (3.0 mg, 8%), mp >400 °C. The product
obtained by an alternative procedure was previously described and
characterized.32
3
(400 MHz, CD2Cl2): 11.16 (s, 2H, NH), 9.47 (d, J = 8.7 Hz, 2H),
4
3
4
7.60 (d, J = 1.8 Hz, 2H), 7.50 (dd, J = 8.7 Hz, J = 1.8 Hz, 2H),
4.13−4.02 (m, 4H), 1.82−1.68 (m, 4H), 1.52 (s, 9H), 1.50−1.24 (m,
18H), 0.93−0.84 (m, 6H). 13C NMR (151 MHz, CDCl3): 165.1,
163.7, 154.7, 144.0, 143.7, 129.5, 127.5, 123.5, 121.1, 119.8, 119.0,
117.1, 108.0, 102.0, 41.2, 40.1, 35.6, 32.02, 31.99, 31.6, 29.6, 29.54,
29.45, 29.42, 28.34, 28.3, 27.5, 27.4, 22.83, 22.81, 14.26. HRMS (ESI,
acetonitrile/chloroform, pos mode): m/z 780.4607 [M]+, calcd for
C50H60N4O4: 780.4609. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) =
Red2
532 (40600). CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2
−1.56 V, E1/2
=
Red1
= −1.21 V, EpOx(X/X+) = 1.05 V.
N,N′-Di(n-octyl)-5H,8H-2,11-di-tert-butylcarbazolo[2,3-b]-
carbazole[6,7:13,14]tetracarboxylic Acid Diimide (2d). NDI 1d (160
mg, 0.170 mmol), K2CO3 (48.0 mg, 0.347 mmol), and PdOAc2 (11.1
mg, 49.4 μmol) were placed under argon, and dry DMF (8 mL) was
added. The reaction mixture was stirred for 60 min at 100 °C. After
removal of the solvent under reduced pressure, the residue was
purified by column chromatography (dichloromethane/pentane 1:1)
yielding a dark red solid (42.8 mg, 32%). Mp: 285−288 °C. 1H NMR
N,N′-Bis(2-ethylhexyl)-5H,12H-carbazolo[2,3-b]carbazole-
[6,7:13,14]tetracarboxylic Acid Diimide (3b). 2,6-Br2-NDI-EtHex
(156 mg, 0.241 mmol), 2-bromoaniline (177 mg, 0.680 mmol),
Pd(OAc)2 (18.2 mg, 81.1 μmol), and K2CO3 (66.0 mg, 0.478 mmol)
were placed under argon, and dry DMF (10 mL) was added. The
mixture was refluxed for 50 min, and DMF was removed under
reduced pressure. The residue was purified by column chromatog-
raphy (dichloromethane/pentane 1:1) yielding a dark green solid (16
mg, 10%). Mp: 359−360 °C. 1H NMR (400 MHz, CDCl3): 11.52 (s,
4
(400 MHz, CD2Cl2): 11.25 (s, 2H), 9.78 (d, J = 2.0 Hz, 2H), 7.74
3
(dd, J = 8.4 Hz, 4J = 2.0 Hz, 2H), 7.51 (dd, 3J = 8.4 Hz, 5J = 0.5 Hz,
3
3
2H), 9.76 (d, J = 8.1 Hz, 2H), 7.70−7.68 (m, 2H), 7.56 (d, J = 8.0
Hz, 2H), 7.46−7.41 (m, 2H), 4.42−4.21 (m, 4H), 2.19−2.01 (m, 2H),
2H), 4.43 (t, 3J = 7.5 Hz, 2H), 4.30 (t, 3J = 7.5 Hz, 2H), 2.00−1.88 (m,
2H), 1.88−1.76 (m, 2H), 1.55 (s, 9H), 1.52−1.22 (m, 20H), 0.92−
0.85 (m, 6H). 13C NMR (101 MHz, CDCl3): 165.5, 164.0, 144.5,
144.0, 141.4, 128.2, 127.9, 126.2, 122.1, 121.3, 117.1, 110.6, 102.0,
41.3, 40.3, 35.4, 32.2, 32.1, 32.0, 29.6, 29.45, 29.44, 29.36, 28.4, 28.2,
27.6, 27.3, 22.83, 22.80, 14.27, 14.25. HRMS (ESI, acetonitrile/
chloroform, pos mode): m/z 780.4607 [M]+, calcd for C50H60N4O4:
780.4609. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 535 (31500).
3
3
1.50−1.27 (m, 16H), 0.99 (t, J = 7.2 Hz, 6H), 0.90 (t, J = 7.4 Hz,
6H). 13C NMR (151 MHz, CDCl3): 165.8, 164.3, 144.2, 142.0, 131.0,
130.3, 130.1, 121.4, 121.0, 120.7, 119.4, 111.2, 104.4, 44.5, 38.1, 31.0,
28.8, 24.3, 23.3, 14.3, 10.9. HRMS (ESI, acetonitrile/chloroform, pos
mode): m/z 669.3437 [M + H]+, calcd for C42H45N4O4 669.3435.
UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 615 (20800), 486
(34100).
Red1
CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2Red2 = −1.56 V, E1/2
N,N′-Bis(2,6-diisopropylphenyl)benzofuro[2,3-b]benzofuran-
[6,7:13,14]tetracarboxylic Acid Diimide (4a). 2,6-Br2-NDI-DIPP
(200 mg, 0.268 mmol), 2-bromophenol (0.08 mL, 0.75 mmol),
Pd(OAc)2 (18.0 mg, 80.6 μmol), and K2CO3 (74.0 mg, 0.537 mmol)
were placed under argon in dry DMF (15 mL) and refluxed for 3 h.
The solvent was removed under reduced pressure, and the residue was
purified by column chromatography (dichloromethane/pentane 2:1)
and washing with hot chloroform yielding a yellow solid (73.0 mg,
= −1.19 V, EpOx(X/X+) = 1.02 V.
N,N′-Di(n-propyl)-5H,8H-3,10-di-tert-butylcarbazolo[2,3-b]-
carbazole[6,7:13,14]tetracarboxylic Acid Diimide (2e). NDI 1e (76.0
mg, 95.0 μmol), K2CO3 (26.5 mg, 0.192 mmol), and Pd(OAc)2 (6.0
mg, 27 μmol) were placed under argon and dry DMF (7 mL) was
added. The reaction mixture was stirred for 90 min at 100 °C. After
removal of the solvent under reduced pressure, the residue was
purified by column chromatography (dichloromethane/pentane 1:1)
yielding a dark red solid (33.0 mg, 54%). Mp: 399−402 °C. 1H NMR
(400 MHz, CD2Cl2): 11.11 (s, 2H), 9.44 (d, 3J = 8.7 Hz, 2H), 7.59 (d,
1
3
35%). Mp: >400 °C. H NMR (400 MHz, CD2Cl2): 9.53 (ddd, J =
8.3 Hz, 4J = 1.4 Hz, 5J = 0.6 Hz, 2H), 7.81 (ddd, J = 8.5 Hz, 4J = 1.2
3
5
3
Hz, J = 0.6 Hz, 2H), 7.84−7.79 (m, 2H), 7.61 (t, J = 7.7 Hz, 2H),
7.56−7.50 (m, 2H), 7.46 (d, 3J = 7.7 Hz, 4H), 2.89 (sept, 3J = 6.8 Hz,
3
4
4J = 1.8 Hz, 2H), 7.50 (dd, J = 8.7 Hz, J = 1.8 Hz, 2H), 4.05−3.98
(m, 4H), 1.82−1.69 (m, 4H), 1.52 (s, 18H), 1.08−0.98 (m, 6H). 13C
NMR (101 MHz, CDCl3): 165.2, 163.8, 154.8, 144.0, 143.7, 129.5,
127.6, 123.5, 121.1, 119.8, 119.0, 117.1, 107.9, 102.0, 42.7, 41.5, 35.6,
31.6, 21.6, 21.5, 11.83, 11.78. HRMS (APCI, dichloromethane, pos
mode): m/z 640.3058 [M]+, calcd for C40H40N4O4: 640.3044. UV−vis
(CH2Cl2): λmax/nm (ε/M−1 cm−1) = 532 (40700).
4H), 1.22 (d, J = 6.84 Hz, 12H), 1.19 (d, J = 6.84 Hz, 12H). 13C
(151 MHz, CDCl3, 55 °C): 163.8, 161.0, 160.7, 157.7, 146.1, 132.9,
132.8, 130.8, 130.5, 130.1, 124.6, 134.5, 134.3, 121.4, 120.8, 112.4,
109.1, 29.73, 24.24, 24.18. HRMS (ESI, acetonitrile/chloroform, pos
mode): m/z 767.3119 [M + H]+, calcd for C50H43N2O6 767.3116.
UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 474 (46200).
Fluorescence (CH2Cl2, λex = 445 nm): λmax = 502 nm; Φfl = 19%.
3
3
N,N′-Di(n-octyl)-5H,8H-1,3,10,12-tetrakis(trifluoromethyl)-
carbazolo[2,3-b]carbazole[6,7:13,14]tetracarboxylic Acid Diimide
(2f). NDI 1f (83.8 mg, 76.0 μmol), K2CO3 (21.5 mg, 0.156 mmol),
and Pd(OAc)2 (5.2 mg, 23 μmol) were placed under argon, and dry
DMF (5 mL) was added. The reaction mixture was stirred for 45 min
at 100 °C. Since no product formation was detected by TLC, the
mixture was refluxed for 1 h. After removal of the solvent under
reduced pressure, the residue was purified by column chromatography
(dichloromethane/pentane 1:1) yielding a dark red solid (22.8 mg,
CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2Red2 = −1.42 V, E1/2
Red1
= −0.94 V.
N,N′-Di(n-octyl)benzofuro[2,3-b]benzofuran[6,7:13,14]-
tetracarboxylic Acid Diimide (4b). 2,6-Br2-NDI-C8H17 (180 mg,
0.278 mmol), 2-bromophenol (0.08 mL, 0.750 mmol) Pd(OAc)2
(18.7 mg, 83.3 μmol), and K2CO3 (76.6 mg, 0.554 mmol) were placed
under argon in dry DMF (7 mL) and refluxed for 3 h. The solvent was
removed under reduced pressure, and the residue was purified by
column chromatography (dichloromethane) yielding a yellow solid
(30.1 mg, 16%). Mp: 376−378 °C. 1H NMR (600 MHz, C2D2Cl4, 78
1
32%). Mp: 216−220 °C. H NMR (400 MHz, CDCl3): 11.3 (s, 2H),
8.03 (s, 2H), 7.92 (s, 2H), 4.36−4.25 (m, 2H), 4.21 (t, 3J = 7.4
3
3
Hz,2H), 2.01 (tt, J = 6.8 Hz, 2H), 1.77 (tt, J = 6.8 Hz, 2H), 1.62−
1.18 (m, 20H), 0.93 −0.83 (m, 6H). 13C NMR (151 MHz, CDCl3):
164.5, 164.2, 144.7, 143.3, 131.7 (2J(C,F) = 34 Hz), 129.8 (2J(C,F) =
34 Hz), 127.7, 125.9, 123.9 (1J(C,F) = 272 Hz), 123.4 (1J(C,F) = 272
Hz), 123.1, 120.5, 118.7, 111.9 (3J(C,F) = 3.9 Hz), 42.7, 40.4, 31.98,
31.95, 29.5, 29.37, 29.35, 29.3, 28.3, 28.1, 27.3, 27.2, 22.82, 22.78,
14.24, 14.23. HRMS (ESI, acetonitrile/chloroform, pos mode): m/z
941.2929 [M + H]+, calcd for C46H41F12N4O4 941.2931. UV−vis
(CH2Cl2): λmax/nm (ε/M−1 cm−1) = 568 (13700), 502 (26700). CV
3
3
°C): 9.61 (d, J = 7.8 Hz, 2H), 7.85 (d, J = 7.8 Hz, 2H), 7.78−7.73
3
3
(m, 2H), 7.58−7.51 (m, 2H), 4.36 (t, J = 7.8 Hz, 4H), 1.88 (tt, J =
7.8 Hz, 4H), 1.55−1.20 (m, 10H), 0.86 (t, 3J = 7.1 Hz, 6H).13C NMR
(151 MHz, C2D2Cl4, 78 °C): 163.4, 161.1, 160.5, 157.2, 132.8, 132.3,
130.3, 124.6, 123.4, 121.3, 120.7, 112.3, 108.9, 41.4, 32.0, 29.6, 29.4,
28.4, 27.6, 22.8, 14.25. HRMS (EI, 70 eV): m/z 670.3030, calcd for
C42H42N2O6: 670.3037. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) =
470 (54000).
137
dx.doi.org/10.1021/jo402365s | J. Org. Chem. 2014, 79, 128−139

The Journal of Organic Chemistry
Article
Red2
2,6-Dibromonaphthalene-1,4,5,8-tetracarboxylic Acid n-Octyl
Ester (5). 2,6-Br2-NDA (2.13 g, 5.00 mmol) was added to a solution
of KOH (1.4 g, 25 mmol) in water (400 mL) and stirred for 30 min at
room temperature. 1-Bromooctane (8.0 mL, 46 mmol) and tetra(n-
octyl)ammonium bromide (2.0 g, 3.7 mmol) were added, and the
mixture was refluxed for 2.5 h. After the mixture was cooled to room
temperature, the aqueous mixture was extracted with dichloromethane
and the aqueous phase was washed with dichloromethane. The organic
phases were combined, the solvent was removed under reduced
pressure, and the residue was purified by column chromatography
(dichloromethane/pentane 1:3) yielding a colorless oil (1.62 g, 36%).
1H NMR (400 MHz, CDCl3): 8.05 (s, 2H), 4.30 (t, 3J = 6.8 Hz, 8H),
476 (30400). CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2
=
Red1
−1.35 V, E1/2
= −0.90 V.
N,N′-Bis(2,6-diisopropylphenyl)-5H,12H-2,4,9,11-tetrachloro-
carbazolo[2,3-b]carbazole[6,7:13,14]tetracarboxylic Acid Diimide
1
(7c). Green solid: 3 mg (11%). Mp: >400 °C. H NMR (400 MHz,
CDCl3): 11.7 (s, 2H), 9.72 (d, 4J = 1.8 Hz, 5J = 0.6 Hz, 2H), 7.75 (d,
4J = 1.8 Hz, 2H), 7.65 (t, 3J = 7.8 Hz, 2H), 7.50 (d, 3J = 7.8 Hz, 4H),
2.86 (sept, J = 6.8 Hz, 4H), 1.24 (2xd, J = 6.9 Hz, 24H). 13C NMR
(151 MHz, CDCl3): 165.4, 163.9, 145.9, 142.4, 140.3, 130.7, 130.63,
130.56, 130.2, 128.6, 127.3, 124.8, 123.0, 122.7, 120.9, 117.1, 105.7,
29.7, 24.3, 24.1. HRMS (APCI, dichloromethane, pos mode): m/z
901.1869 [M + H]+, calcd for C50H41Cl4N4O4 901.1876. UV−vis
(CH2Cl2): λmax/nm (ε/M−1 cm−1) = 629 (20100), 470 (30000). CV
3
3
1.82−1.73 (m, 8H), 1.49−1.22 (m, 40H), 0.90−0.85 (m, 12H). 13C
NMR (101 MHz, CDCl3): 166.6, 166.5, 134.61, 134.57, 132.9, 128.7,
121.3, 66.7, 66.6, 31.9, 29.36, 29.34, 29.31, 29,30, 28.6, 28.4, 26.2, 26.0,
22.9, 14.2. HRMS (ESI, acetonitrile/chloroform, pos mode): m/z
947.3074 [M + K]+, calcd for C46H70Br2KO8 947.3069.
Red2
Red1
(CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2
= −1.30 V, E1/2
=
−0.85 V.
N,N′-Bis(2,6-diisopropylphenyl)-5H,8H-2,4,7,9-tetrachloro-
carbazolo[2,3-b]carbazole[6,7:13,14]tetracarboxylic Acid Diimide
(8). CbDI 2a (53.5 mg, 69.9 μmol) and N-chlorosuccinimide (40.0
mg, 0.300 mmol) were dissolved in a mixture of chloroform (8 mL)
and acetonitrile (10 mL) and refluxed for 3 d. After addition of a
further portion of N-chlorosuccinimide (120 mg, 0.900 mmol), the
reaction was refluxed again for 8 h. The solvent was removed under
reduced pressure, and the residue was purified by column
chromatography and HPLC (dichloromethane/pentane 1:1). The
tetrachloro product was obtained as a dark red solid (25 mg, 40%).
Mp: >400 °C. 1H NMR (400 MHz, CD2Cl2): 11.55 (s, 2H), 9.55 (dd,
Tetraoctyl 5,12-Dihydrocarbazolo[3,2-b]carbazole-6,7,13,14-tet-
racarboxylate (6). Tetetraester 5 (142 mg, 0.156 mmol), 2-
bromoaniline (76.0 mg, 0.442 mmol), Pd(OAc)2 (10.5 mg, 46.8
μmol), and K2CO3 (43.8 mg, 0.317 mmol) were placed under argon.
After addition of dry DMF (10 mL), the mixture was refluxed for 40
min. The solvent was removed under reduced pressure, and the
residue was purified by column chromatography (dichloromethane/
pentane 1:1) and HPLC (NP, chloroform) yielding an orange solid
(19 mg, 13%). Mp: 70−77 °C. 1H NMR (400 MHz, CD2Cl2): 9.75 (s,
5
4
3
4J = 1.8 Hz, J = 0.5 Hz, 2H), 7.75 (d, J = 1.8 Hz, 2H), 7.65 (t, J =
3
3
7.5 Hz, 1H), 7.61 (t, 3J = 7.5 Hz, 1H), 7.55−7.42 (m, 4H), 2.91 (sept,
2H), 8.68 (d, J = 8.2 Hz, 2H), 7.61−7.56 (m, 2H), 7.51 (d, J = 8.1
Hz, 2H), 7.32−7.23 (m, 2H), 4.50−4.35 (m, 8H), 1.84−1.62 (m, 8H),
1.42−1.12 (m, 40H), 0.85−0.74 (m, 12H). 13C NMR (101 MHz,
CDCl3): 168.5, 168.0, 143.5, 140.2, 129.5, 126.3, 126.2, 123.5, 121.2,
120.4, 110.6, 109.7, 65.7, 65.6, 31.9, 29.33, 29.32, 29.2, 28.67, 28.66,
26.05, 26.04, 22.72, 22.71, 14.16. HRMS (ESI, acetonitrile/chloro-
form, pos mode): m/z 930.5755 [M]+, calcd for C58H78N2O8:
3J = 6.8 Hz, 2H), 2.84 (sept, J = 6.8 Hz, 2H), 1.22 (t, J = 6.8 Hz,
3
3
2H), 1.21 (t, J = 6.8 Hz, 2H). 13C NMR (151 MHz, CDCl3): 165.3,
3
163.9, 145.9, 145.8, 144.1, 139.6, 130.8, 130.6, 130.5, 130.1, 129.6,
128.2, 128.0, 127.7, 126.2, 124.8, 124.7, 123.6, 123.5, 119.2, 117.2,
103.7, 29.8, 29.6, 24.22, 24.19. HRMS (ESI, acetonitrile/chloroform,
pos mode): m/z 901.1881 [M + H]+, calcd for C50H41Cl4N4O4
901.1877. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 597
(11600), 531 (28000). CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+):
930.5753. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 500 (10100),
Red2
400 (27000). CV (CH2Cl2, 0.1 M TBAHFP, vs Fc/Fc+): E1/2
=
Red1
Ox
Red2
Red1
−1.96 V, E1/2
= −1.74 V, E1/2 = 0.73 V.
E1/2
= −1.35 V, E1/2
= −0.90 V.
Chlorination of CbDI Derivative 3a. CbDI 3a (24.0 mg, 36.6
μmol) and N-chlorosuccinimide (20.0 mg, 0.150 mol) were dissolved
in a mixture of chloroform (10 mL) and acetonitrile (10 mL) and
refluxed for 5 d. After removal of the solvent under reduced pressure,
the residue was purified by column chromatography (dichloro-
methane/pentane 1:1) yielding the following compounds.
ASSOCIATED CONTENT
■
S
* Supporting Information
Figures S1−S6 and Tables S1−S4 mentioned in the text, NMR
spectra of new compounds (Figures S7−S48), and CIF files of
compounds 3a (CCDC 965679), 2a (CCDC 965680), 2d
(CCDC 965681), and 2e (CCDC 965682). This material is
available free of charge via the Internet at http://pubs.acs.org.
N,N′-Bis(2,6-diisopropylphenyl)-5H,12H-2,9-dichlorocarbazolo-
[2,3-b]carbazole[6,7:13,14]tetracarboxylic Acid Diimide (7a). Green
1
solid: 15 mg (57%). Mp: >400 °C. H NMR (400 MHz, CDCl3):
11.55 (s, 2H), 9.78 (d, 4J = 1.8 Hz, 2H), 7.68 (dd, 3J = 8.5 Hz, 4J = 2.0
3
Hz), 7.64 (t, 3J = 7.6 Hz, 2H), 7.52 (d, J = 8.4 Hz, 5J = 0.5 Hz, 2H),
7.49 (d, 3J = 7.8 Hz, 4H), 2.87 (sept, 3J = 6.9 Hz, 4H), 1.26−1.21 (m,
24H). 13C NMR (101 MHz, CDCl3): 165.7, 164.1, 145.9, 142.9,
142.8, 131.7, 130.5, 130.31, 130.29, 129.9, 127.3, 124.6, 122.2, 122.1,
120.3, 112.2, 105.0, 29.61, 24.22, 24.14. HRMS (ESI, acetonitrile/
chloroform, pos mode): m/z 833.2660 [M + H]+, calcd for
C50H43Cl2N4O4 833.2656. UV−vis (CH2Cl2): λmax/nm (ε/M−1
cm−1) = 635 (19900), 483 (30000). CV (CH2Cl2, 0.1 M TBAHFP,
AUTHOR INFORMATION
■
Corresponding Author
*Fax: +49 (0)931 31 84756. Tel: +49 (0)931 31 85340. E-mail:
wuerthner@chemie.uni-wuerzburg.de.
Notes
The authors declare no competing financial interest.
Red2
Red1
vs Fc/Fc+): E1/2
= −1.38 V, E1/2
= −0.94 V.
N,N′-Bis(2,6-diisopropylphenyl)-5H,12H-2,4,9-trichlorocarbazolo-
[2,3-b]carbazole[6,7:13,14]tetracarboxylic Acid Diimide (7b). Green
solid: 7.0 mg (26%). Mp: >400 °C.1H NMR (400 MHz, CD2Cl2):
11.64 (s, 1H), 11.58 (s, 1H), 9.74 (d, 4J = 2.0 Hz, 1H), 9.68 (dd, 4J =
2.0 Hz, 5J = 0.68 Hz, 1H), 7.76 (d, 4J = 2.0 Hz, 1H), 7.72 (dd, 3J = 8.6
ACKNOWLEDGMENTS
■
We thank Hagen Klauk and Ute Zschieschang for the
evaluation of the transistor properties. Financial support by
the German Ministry of Education and Research (BMBF) for
this work within the project POLYTOS (FKZ: 13N10205) in
the Leading Edge Cluster “Forum Organic Electronics” is
gratefully acknowledged.
4
3
Hz, J = 2.0 Hz, 2H), 7.66−7.60 (m, 3H), 7.48 (d, J = 7.8 Hz, 2H),
3
7.48 (d, J = 7.8 Hz, 2H), 2.95−2.83 (m, 4H), 1.26−1.19 (m, 24H).
13C NMR (151 MHz, CDCl3): 165.6, 165.5, 164.0, 145.92, 145.89,
143.2, 142.9, 142.1, 140.2, 132.0. 130.9, 130.5, 130.42, 130.40, 130.37,
130.34, 130.06, 130.05, 128.5, 127.5, 127.1, 124.8, 124.7, 123.1,
122.48, 122.46, 122.1, 120.8, 120.4, 117.0, 112.3, 105.9, 104.9, 29.66,
29.63, 24.3, 24.24, 24.16, 24.1. HRMS (ESI, acetonitrile/chloroform,
neg mode): m/z 865.2125 [M − H]−, calcd for C50H40Cl3N4O4:
868.2121. UV−vis (CH2Cl2): λmax/nm (ε/M−1 cm−1) = 632 (19800),
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