Dihydroindeno[2,1-c]fluorene-based imide dyes: Synthesis, structures, photophysical and electrochemical properties

Article abstract of DOI:10.1021/jo4028616

A new kind of imide dyes based on dihydroindeno[2,1-c]fluorene have been developed. Consequently, a series of the organic dyes were conveniently and efficiently synthesized. The single crystal structure showed the dihydroindeno[2,1-c]fluorene core was almost planar, and the dye molecule could pack into herringbone-like structure in the solid state. It was found that the imide dyes all showed strong fluorescence emissions in tetrahydrofuran, and they also exhibited obvious red shifts with the increase of the π-conjugation system and the enhancement of the electronic-donating effect. Moreover, the electrochemical cyclic voltammograms of the imide dyes displayed irreversible redoxes in the film state. The electronic structures of aryl substituted imide dyes were also studied by the density functional theory (DFT), which gave a further explanation for their electrochemical behaviors.

Full text of DOI:10.1021/jo4028616

Article
pubs.acs.org/joc
Dihydroindeno[2,1‑c]fluorene-Based Imide Dyes: Synthesis,
Structures, Photophysical and Electrochemical Properties
Yang-Yang Li,†,‡ Hai-Yan Lu,*,‡ Meng Li,†,‡ Xiao-Jun Li,†,‡ and Chuan-Feng Chen*,†
†Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100190, China
‡University of Chinese Academy of Sciences, Beijing 100049, China
S
* Supporting Information
ABSTRACT: A new kind of imide dyes based on dihydroindeno[2,1-c]fluorene have been
developed. Consequently, a series of the organic dyes were conveniently and efficiently
synthesized. The single crystal structure showed the dihydroindeno[2,1-c]fluorene core was
almost planar, and the dye molecule could pack into herringbone-like structure in the solid
state. It was found that the imide dyes all showed strong fluorescence emissions in
tetrahydrofuran, and they also exhibited obvious red shifts with the increase of the π-
conjugation system and the enhancement of the electronic-donating effect. Moreover, the
electrochemical cyclic voltammograms of the imide dyes displayed irreversible redoxes in the
film state. The electronic structures of aryl substituted imide dyes were also studied by the
density functional theory (DFT), which gave a further explanation for their electrochemical
behaviors.
perylene-3,4:9,10-bis(dicarboximides) (PDIs),21−23 naphtha-
INTRODUCTION
■
lene-1,8-dicarboximides (NMI),24 naphthalene-1,4:5,8-bis-
Dihydroindenofluorenes are a class of scaffold-shaped poly-
(dicarboximides) (NDI),25−27 and anthracene diimide.28,29
cyclic aromatic hydrocarbons (PAHs) that consist of terphenyl
bridged by two methylene groups.1 Its chemistry has not been
These imide dyes have been applied in wide research areas
including fluorescent sensing and imaging,30 and dye-sensitized
solar cells31−33 for their good stability, high electron affinities,
and charge transmission ability.34,35 We deduced that by the
combination of imide moiety and dihydroindeno[2,1-c]fluorene
core, a new kind of organic dyes could be developed. In this
paper, we report (1) the convenient and efficient synthesis of a
series of imide dyes based on dihydroindeno[2,1-c]fluorene
core; (2) the crystal structure of the dye containing two 3-
thienyl groups and its assembly in the solid state; (3) the strong
fluorescence emissions of the imide dyes in tetrahydrofuran;
(4) the electrochemical properties of the imide dyes in the film
state; and (5) their electronic structures studied by the density
functional theory (DFT).
well developed2 since Gabriel synthesized the first indeno-
fluorene dione in the late nineteenth century.3 Until very recently
the dihydroindenofluorenes were identified as a semiconducting
material in devices,3−5 and since then the molecules with
dihydroindenofluorene frameworks have been attracting more
and more attention.6−9 The dihydroindenofluorene family is
comprised of five constitutional isomers,1 among which most of
the researches were focused on the dihydroindeno[1,2-b]fluorene
for its simple and high-yield synthetic routes.10−12 However, the
studies on the other kinds of dihydroindenofluorenes were rather
limited. Therefore, it is of great importance to have a more
comprehensive understanding on other kinds of dihydroindeno-
fluorene systems.
Among all the dihydroindenofluorene isomers, dihydro-
indeno[2,1-c]fluorene is the only one that possessed helicene-
like structure with ortho-fused aromatic rings.1−3,13 Although
Haley group recently reported the first example of a fully
conjugated indeno[2,1-c]fluorene, and the X-ray crystal structures
of the P- and M-enantiomers were also shown,2,3 almost no
dihydroindeno[2,1-c]fluorene derivatives with a unique structure
have been reported so far14−18 probably due to their synthetic
difficulties, such as complicated precursors, harsh reaction
conditions, and difficulties for further functionalization.
RESULTS AND DISCUSSION
■
Synthesis of the Imide Dyes. Synthesis of imide 5 is
depicted in Scheme 1. Starting from the commercially available
6-methoxy-2,3-dihydro-1H-inden-1-one 1, diene 2 was ob-
tained in 44% yields for two steps. The Diels−Alder reaction
between diene 2 and maleic anhydride gave product 3 in 86%
yield, which then underwent the dehydrogenation with lead
tetraacetate as the oxidant to give the anhydride 4 in 90% yield.
Imides, as a kind of common electronic-withdrawing group,
are often fused with electronic-rich π-conjugated structures,
such as perylene, naphthalene, and anthracene, to form different
organic dyes like perylene-3,4-dicarboximides (PMIs),19,20
Received: December 25, 2013
Published: February 18, 2014
© 2014 American Chemical Society
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Scheme 1. Synthesis of Imide 5
Scheme 2. Synthesis of Imide Dyes 8a−n
Figure 1. (a) Top view and (b) side view of crystal structure of 8j. Hydrogen atoms are omitted for clarity.
Finally, imide 5 was obtained in 90% yield by the reaction of 4
with isoamylamine in DMF under argon.
As shown in Scheme 2, when acid anhydride 3 underwent
found that the dibromo-substituted anhydride 6 could be
obtained in 95% yield. Compound 6 is an excellent precursor
for the further functionalization. Consequently, the reaction of
6 with isoamylamine in the presence of imidazole gave the
the dehydrogenation by bromine in dichloromethane, it was
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Figure 2. (a) Head to tail arrangement of molecule 8j, and (b) its herringbone-like packing viewed along the a axis.
dibromo-substituted imide 7 in 85% yield, which then
underwent Suzuki−Miyaura cross-coupling reactions with a
variety of boric acids to give diaryl-substituted imide dyes 8a−n
in 62−95% yields. All of these new imide dyes showed good
solubility in common organic solvents including toluene, DCM,
THF, EA, TCM, and DMSO at room temperature.
Crystal Structure of Imide Dye 8j. A single crystal of 8j
suitable for X-ray diffraction was obtained by slow evaporation
of its solution in chloroform and cyclohexane. The crystal
structure was shown in Figure 1. It was found that the torsion
angle of C7−C6−C19−C23 was 4.90°, indicating that the
dihydroindeno[2,1-c]fluorene core had an approximate plane
structure. The bond lengths of C8−C9 (1.50 Å), C5−C9 (1.49 Å);
C20−C21 (1.50 Å), C21−C22 (1.49 Å) were all shorter than the
C−C single bond (1.54 Å), but longer than the C−C double bond
(1.34 Å), suggesting that the electrons in the dihydroindeno[2,1-
c]fluorene core were delocalized. Moreover, it was also found that
Figure 3. (a) Fluorescence spectra of 8h in different solvents (1 ×
10−5 M), and (b) images for the fluorescent colors of 8h in
corresponding solution under ultraviolet light (365 nm).
by the head to tail arrangement (Figure 2a) with the distances of
3.20 and 3.26 Å between the adjacent molecules, molecule 8j could
pack into a herringbone-like structure (Figure 2b).
Photophysical Properties. In order to explore the
influence of solvents on the imide dyes, we first investigated
the photophysical properties of the phenyl substituted
derivative 8h in different solvents, and the results were
summarized in Table 1. It was found that the maximum
different solvents (1 × 10−5 M) showed that by increasing the
polarity of the solvent, the maximum emission band increased
from 460 nm (toluene) to 503 nm (DMSO). And the Stokes
shift also changed largely from less polar solvent (toluene 55 nm)
to more polar solvent (ACN 91 nm and DMSO 90 nm).
Moreover, the fluorescence lifetime (τf) showed that with the
increase of the solution polarity, the life expectancy also increases
dramatically from 2.55 ns (toluene) to 6.41 ns (DMSO). These
results indicated that 8h showed not only a polar character but
also a strong push−pull electronic effect in the excited state
compared with those ones in its ground state. Furthermore, it was
found that the fluorescence color of 8h under ultraviolet light
(365 nm) could be changed from blue in toluene to green in
DMSO, and these color changes in different solvents could be
visually seen as well (Figure 3b).
The photophysical properties of the imide dyes 8a−n with
different aromatic groups in THF at a concentration of
1 × 10−5 M were further investigated in details, and the
photophysical data were summarized in Table 2. In the UV−vis
absorption spectra (Figures S40−S42, Supporting Information),
two absorption bands were observed in general. A narrow one
located at 250−320 nm, which may be caused by the π−π*
transition absorption of conjugated diene in the benzene ring,
and a wide one located at 320−440 nm, which may be caused by
the π−π* transition absorption of the big conjugate system, and
that was common in the push−pull type molecules.9,38
Moreover, it was also found that with the increase of the
Table 1. Photophysical Data of 8h in Different Solvents
λ
λ
Δλ
τf
(ns)
a
abs b
(nm)
em c
stokdes
e
f
solvent
log ε
(nm)
(nm)
Φf
toluene
DCM
THF
EA
376, 405 4.40, 4.38
376, 411 4.38, 4.36
375, 408 4.42, 4.41
374, 405 4.41, 4.40
377, 414 4.35, 4.34
460
489
469
468
492
486
497
503
55
78
61
63
78
79
91
90
0.48
0.63
0.55
0.61
0.64
0.38
0.46
0.47
2.55
5.64
3.71
3.99
5.95
5.36
6.33
6.41
TCM
acetone 375, 407 4.43, 4.43
ACN
375, 406 4.41, 4.38
377, 413 4.35, 4.36
DMSO
a
DCM: dichloromethane; THF: tetrahydrofuran; EA: ethyl acetate;
TCM: trichloromethane; ACN: acetonitrile; DMSO: dimethyl
b
sulfoxide. The maximum absorption bands more than 300 nm.
c
d
Excited at the longest maximum absorption band. Stokes shift =
e
36,37
λmax − λmaxabs. Perylene as the standard (cyclohexane, 0.98).
em
f
Fluorescent lifetime.
absorption of 8h at the concentration of 1 × 10−5 M changed
slightly from toluene to DMSO. On the contrary, its
fluorescence emission spectra showed obvious solvatochrom-
ism. As shown in Figure 3a, the fluorescence spectra of 8h in
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Table 2. Photophysical Properties of 8a−n in THF
a
b
c
d
e
compd
Ar
λabs (nm)
log ε
λem (nm)
Δλstokes (nm)
Φf
τf (ns)
8a
8b
8c
8d
8e
8f
4-pyridyl
296, 372, 407
299, 373, 404
304, 375, 409
283, 376, 409
310, 376, 414
296, 375, 406
293, 374, 405
294, 375, 405
296, 377, 411
299, 383, 417
296, 382, 417
315, 398, 433
310, 428
4.66, 4.38, 4.38
4.72, 4.43, 4.43
4.78, 4.50, 4.53
4.77, 4.51, 4.54
4.74, 4.52, 4.57
4.72, 4.46, 4.46
4.72, 4.48, 4.47
4.67, 4.42, 4.41
4.70, 4.46, 4.47
4.63, 4.40, 4.42
4.71, 4.50, 4.51
4.69, 4.51, 4.57
4.89, 4.59
456
458
460
461
462
466
468
469
476
487
493
505
563
593
49
54
51
52
48
60
63
64
65
70
76
72
135
0.42
0.45
0.51
0.11
0.52
0.52
0.52
0.53
0.67
0.55
0.59
0.53
0.12
0.02
2.24
2.43
2.10
1.43
1.83
3.05
3.77
3.87
3.92
3.42
4.42
3.18
4.14
1.01
4-trifluoromethyl-phenyl
4-cyano-phenyl
4-nitryl-phenyl
4-formyl-phenyl
4-chloro-phenyl
4-fluoro-phenyl
phenyl
8g
8h
8i
4-methyl-phenyl
3-thienyl
8j
8k
8l
4-methoxy-phenyl
2-thienyl
8m
triphenylamine
8n
4-N,N-dimethyl-phenyl
309, 440
4.72, 4.51
153
a
b
c
abs
The maximum absorption bands (1 × 10−5 M) were only shown. Excited at the longest maximum absorption peak. Stokes shift = λmaxem − λmax
.
d
e
Perylene as the standard (cyclohexane, 0.98).36,37 Fluorescent lifetime.
electron donating ability of the substituents, the dyes showed not
only more red-shift absorption, but also considerably enhanced
molar absorption coefficient. Similar to the absorption spectra,
the fluorescence spectra of dyes 8a−n also exhibited red-shift
emission bands compared with imide 5, and the greater red-shift
was found with the increase of the electron-donating ability of
the substituents (Figure 4a). Furthermore, it was found that
process, which suggested that the ionic species were either very
stable or transformed into the electroinactive species. It was
also found that the electronic-withdrawing aromatic substitu-
ents of 8a−e had main influence on the negative potential
region, and made the reduction potential shift to a more
positive direction for the electronic-withdrawing groups, which
could strengthen the electron affinity ability. Meanwhile, the
electronic-donating aromatic substituents of 8j−n had main
influence on the positive potential region and made the
oxidation potential to a negative direction for the electronic-
donating groups, which could reduce the ionization potential.
We further found that along with the enhancement of aromatic
substituents electron-withdrawing ability, the reduction poten-
tial moved more positive, but the oxidation potential moved
just the opposite.
Theoretical Studies. In order to get insight into the
electronic effects of peripheral aromatic substituents on the
imide dyes, we further performed density functional theory
(DFT) calculations on compounds 8c, 8h, 8k, and 8l at the
B3LYP39,40/6-31G(d) level with Gaussian 09 program. It was
noted that 8c, 8h, 8k, and 8l successively involve the aromatic
substituent of an electron-withdrawing 4-cyano-phenyl, a
phenyl, an electron-donating 4-methoxy-phenyl, and a 2-
thienyl. The calculated energies including the electron-state-
density distribution of the highest occupied molecular orbital
(HOMO) and the lowest unoccupied molecular orbital
(LUMO) of 8c, 8h, 8k, and 8l were shown in Figure 6 and
Figure 7, respectively, and served as the representative systems
to study the electronic influences of the aromatic substituents
on imide dyes.
Figure 6 showed the optimized geometries with the electron-
state density distributions of the LUMO, HOMO, and HOMO-
1 for compounds 8c, 8h, 8k, and 8l. We could find that (1)
aromatic substituents showed well conjugated effect with the
dihydroindeno[2,1-c]fluorene core, which extended the con-
jugation system greatly; (2) the HOMO-1 orbitals of all
compounds were more or less delocalized over the conjugated
part of the entire molecule; (3) the electron density of the
HOMO were mainly distributed on the peripheral aromatic
substituent and also spread over the entire dihydroindeno[2,1-
c]fluorene core, while the electron density of the LUMO
showed a decrease generally in the electron density on the
aromatic substituents moieties and a concomitant increase in
Figure 4. (a) Fluorescence spectra of 8a−n in THF (1 × 10−5 M), and
(b) the fluorescent image of corresponding solutions under ultraviolet
light (365 nm).
these imide dyes had good photoluminescence capabilities with
Φf values between 0.42 and 0.67 except for 8d (0.12), 8m (0.12),
8n (0.02). The fluorescence images of 8a−n under ultraviolet
light (365 nm) showed that most of the colors of the imide dyes
were blue, while green, orange and red color for 8l, 8m, and 8n,
respectively, could be obviously observed (Figure 4b).
Electrochemical Properties. The electrochemical proper-
ties of 8a−n were measured by cyclic voltammetry (CV) in a
0.1 M n-Bu4NPF6 solution in acetonitrile at a scan rate of 100
mV/s at room temperature under the protection of argon, and
the corresponding data were summarized in Table 3. Figure 5
shows the cyclic voltammetry curves of 8a−e (left) and 8j−n
(right). It was found that all of compounds 8a−n exhibited
completely irreversible peaks in both oxidation and reduction
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Table 3. Electrochemistry Properties of 8a−n
a
a
onset
b
b
c
onset
compd
Ar
Eox
Ered
HOMO
LUMO
Eg
8a
8b
8c
8d
8e
8f
4-pyridyl
1.45
1.40
1.27
1.38
1.13
1.21
1.25
1.13
1.08
0.96
0.96
0.98
0.63
0.37
−1.49
−1.78
−1.65
−1.48
−1.70
−1.72
−2.17
−1.75
−1.77
−1.81
−2.04
−1.99
−2.07
−1.84
−6.26
−6.21
−6.08
−6.19
−5.94
−6.02
−6.06
−5.94
−5.89
−5.77
−5.77
−5.79
−5.44
−3.18
−2.89
−3.02
−3.19
−2.97
−2.95
−2.50
−2.92
−2.90
−2.86
−2.63
−2.68
−2.60
−2.83
3.08
3.32
3.06
3.00
2.97
3.07
3.56
3.02
2.99
2.91
3.14
3.11
2.84
2.35
4-trifluoromethyl-phenyl
4-cyano-phenyl
4-nitryl-phenyl
4-formyl-phenyl
4-chloro-phenyl
4-fluoro-phenyl
phenyl
8g
8h
8i
4-methyl-phenyl
3-thienyl
8j
8k
8l
4-methoxy-phenyl
2-thienyl
8m
triphenylamine
8n
4-N,N-dimethyl-phenyl
−5.18
a
b
c
All potentials are versus Ag/AgNO3. HOMO = −EoxvsFc/Fc+−4.8 eV. LUMO = −EredvsFc/Fc+−4.8 eV. Electrochemical band gaps were determined
by Eg = EHOMO − ELUMO
.
Figure 5. Cyclic voltammograms of 8a−8e (left) and 8j−n (right) in n-Bu4NPF6 solution in acetonitrile at a sweep rate of 100 mV/s. Working
electrode: Platinum inlaid disk (diameter ∼2 mm). Counter electrode: platinum wire. Reference electrode: Ag/AgNO3 (0.01 M in acetonitrile).
the electron-withdrawing imide moiety; (4) dihydroindeno[2,1-
c]fluorene core involving both the HOMO and LUMO orbitals
possesses more electron density, which indicates that the
dihydroindenofluorene moiety played an important role in the
charge transfer process of π−π* conversion from the HOMO
to the LUMO orbitals.
of 8h (less than 0.1 eV), the HOMO energy levels showed an
obvious upshift (more than 0.2 eV), which resulted in smaller
energy gaps of 8l (3.05 eV) and 8m (2.91 eV) than that of 8h
(3.20 eV). These results could also give an explanation in theory
to that the aromatic substituent group with electronic-donating
property had main influence on the oxidation process of the dye.
Figure 7 shows the calculated energy levels of 8c, 8h, 8k, and
8l. It was found that aromatic substituent group with electron-
withdrawing property (e.g., 8c) could make the HOMO and
LUMO downshift at the same time, but the HOMO downshifts
more seriously, which thus made the energy gap of 8c (3.26
eV) be bigger than that of 8h (3.20 eV) with electron-donating
property. This lower LUMO energy level could explan why the
dye with electron-withdrawing aromatic substituent groups
showed a more positive reduction potential. Moreover, although
the LUMO energy levels in dyes 8l and 8m with electron-
donating aromatic substituent groups were almost the same as that
CONCLUSIONS
■
In summary, we have developed a new kind of dihydroindeno-
[2,1-c]fluorene-based imide dyes. Consequently, a series of the
imide dyes were conveniently and efficiently synthesized
starting from the commercially available 6-methoxy-2,3-
dihydro-1H-inden-1-one. The crystal structure of 8j showed
that the dihydroindeno[2,1-c]fluorene core has an approximate
plane structure, and the molecule can pack into a herringbone-like
assembly by the head to tail arrangements in the solid state. It was
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Figure 6. Molecular orbital surfaces of the HOMO-1, HOMO, and LUMO of 8c, 8h, 8k, 8l obtained at the B3LYP/6-31G(d) level.
mixture was heated to reflux for 6 h. The remained anhydride and
acetic acid were then removed under reduced pressure to give deep
red sticky residue, which was dissolved in CH2Cl2 and washed by
NaHCO3 aqueous solution (3 × 150 mL). The combined organic layer
was washed with water, dried over MgSO4, and then concentrated under
reduced pressure to give a residue, which was separated by
chromatography with CH2Cl2 and petroleum ether (1:5, v/v) as eluent
1
to give pure diene 2 (7.8 g, 44%) as yellow powder: mp 84−86 °C; H
NMR (300 MHz, CDCl3) δ 7.37 (d, J = 8.2 Hz, 2H), 7.11 (d, J = 2.4 Hz,
2H), 6.81 (d, J = 2.4 Hz, 1H), 6.78 (d, J = 2.4 Hz, 1H), 6.74 (s, 2H), 3.76
(s, 6H), 3.47 (d, J = 1.5 Hz, 4H); 13C NMR (75 MHz, CDCl3) δ 159.2,
145.9, 139.1, 136.6, 132.9, 124.6, 111.2, 106.8, 55.6, 37.9; HR ESI-MS
m/z calcd for [M + H+]+ C20H19O2, 291.1380, found 291.1380.
2,12-Dimethoxy-5,5a,8b,9-tetrahydroindeno[2′,1′:3,4]-
fluoreno[1,2-c]furan-6,8(5bH,8aH)-dione (3). The mixture of
diene 2 (4 g, 13.8 mmol) and maleic anhydride (13 g, 138 mmol)
was heated at 150 °C for 4 h. The reaction mixture was treated with
hot water (50 mL), cooled to room temperature, and then performed
by filtration. The crude product was purified by recrystallization with
acetic anhydride to give the anhydride 3 (4.2 g, 81%) as pale yellow
powder: mp >300 °C; 1H NMR (300 MHz, CDCl3) δ 7.64 (d, J = 2.2
Hz, 2H), 7.23 (d, J = 4.5 Hz, 2H), 6.86 (dd, J = 8.4, 2.3 Hz, 2H), 3.85
(d, J = 3.4 Hz, 8H), 3.59−3.57 (m, 2H), 3.34−3.23 (m, 4H); 13C NMR
(125 MHz, CDCl3) δ 171.1, 158.8, 139.7, 139.0, 137.0, 126.2, 115.7,
108.4, 55.6, 43.3, 42.7, 31.3; HR ESI-MS m/z calcd for [M + H+]+
C24H21O5, 389.1384, found 389.1382.
2,12-Dimethoxyindeno[2′,1′:3,4]fluoreno[1,2-c]furan-6,8-
(5H,9H)-dione (4). The mixture of 3 (2 g, 5.15 mmol) and lead
tetraacetate (2.2 equiv) in acetic acid and acetic anhydride (1:1, v/v)
was stirred at 100 °C for 4 h. After the mixture was cooled to room
temperature, water was added and then collected by filtration to give
compound 4 (1.8 g, 91%) as yellow powder. Further purification was
not performed for its poor solubility: mp >300 °C; HR ESI-MS m/z
calcd for [M + H+]+ C24H17O5, 385.1071, found 385.1072.
Figure 7. Calculated energy levels of molecular orbitals of 8c, 8h, 8k,
and 8l.
found that these aryl substituted imide dyes showed fluorescent
emission from blue to red (456 to 593 nm), and most of them
also exhibited moderate to high quantum yields (0.42−0.67),
which could thus make them be suitable candidates for organic
luminescent materials. Moreover, the electrochemical properties of
the aryl-substituted imide dyes were measured by cyclic
voltammetry, and they showed great dependent on their structural
features. The theoretical calculations were also performed and gave
a further explanation for their electrochemical behaviors.
EXPERIMENTAL SECTION
■
6,6′-Dimethoxy-3H,3′H-1,1′-biindene (2). A mixture of acti-
vated aluminum flake (3.2 g, 119 mmol), 6-methoxy-2,3-dihydro-1H-
inden-1-one 1 (20 g, 123 mmol), toluene (70 mL), absolute ethanol
(40 mL), HgCl2 (0.25 g, 0.92 mmol) was heated to reflux for 10 h.
After the reaction mixture was cooled to room temperature, aqueous
HCl (10%, 100 mL) and excess sulfur were added and vigorously
stirred for another 12 h. The mixture was filtrated, and the filtrate was
extracted with ethyl acetate (3 × 150 mL). The combined organic
layer was washed with water, dried over MgSO4, and then
concentrated under reduced pressure to give a residue. To the residue
was added anhydride (24 mL) and acetic acid (16 mL), and the
7-Isopentyl-2,12-dimethoxy-5H-diindeno[2,1-e:1′,2′-g]-
isoindole-6,8(7H,9H)-dione (5). To a solution of compound 4
(200 mg, 0.52 mmol) in DMF under argon was added isoamylamine
(10 equiv), and the mixture was stirred at 80 °C for 12 h. The solvent
was removed under reduced pressure to give a residue, which was
purified by chromatography with CH2Cl2 and petroleum ether (1:1, v/v)
as eluent to give compound 5 (212 mg, 90%) as yellowish-green powder:
1
mp 236−237 °C; H NMR (300 MHz, CDCl3) δ 7.74 (d, J = 2.0 Hz,
2H), 7.38 (d, J = 8.3 Hz, 2H), 6.89 (dd, J = 8.3, 2.1 Hz, 2H), 3.85
2144
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Article
(s, 10H), 3.60 (t, J = 7.5 Hz, 2H), 1.73−1.50 (m, 3H), 0.99 (d, J = 6.4 Hz,
6H); 13C NMR (75 MHz, CDCl3) δ 168.6, 158.8, 142.1, 141.7, 140.7,
137.3, 125.7, 124.1, 114.2, 109.7, 55.6, 37.5, 36.2, 34.6, 26.0, 22.4; HR ESI-
MS m/z calcd for [M + H+]+ C29H28NO4, 454.2013, found 454.2015.
3,11-Dibromo-2,12-dimethoxyindeno[2′,1′:3,4]fluoreno[1,2-
c]furan-6,8(5H,9H)-dione (6). To the solution of anhydride 3 (1 g,
2.6 mmol) in CH2Cl2 (100 mL) was added bromine (1 mL) in
CH2Cl2 (10 mL) dropwise. After 4 h, sodium hydrogen sulfite was
added to the mixture until the color of the mixture was changed into
yellow. The solid was collected by filtration to give the dibromo-
substituted anhydride 6 (1.2 g, 86%) as a yellow powder: mp >300 °C;
1H NMR (300 MHz, CDCl3) δ 8.05 (s, 2H), 7.94 (s, 2H), 4.30 (s,
(d, J = 8.8 Hz, 4H), 8.21 (s, 2H), 7.80 (d, J = 8.8 Hz, 4H), 7.69 (s,
2H), 4.34 (s, 4H), 4.01 (s, 6H), 3.78−3.70 (t, J = 6.0 Hz, 2H), 1.71−
1.58 (m, 3H), 1.00 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ
168.7, 156.1, 147.0, 144.9, 142.23, 142.16, 141.7, 138.6, 130.4, 129.5,
127.5, 125.0, 123.4, 107.4, 56.4, 37.5, 36.5, 35.2, 26.0, 22.4; HR ESI-
MS m/z calcd for [M + H+]+ C41H34N3O8, 696.2340, found 696.2342.
4,4′-(7-Isopentyl-2,12-dimethoxy-6,8-dioxo-6,7,8,9-tetrahy-
dro-5H-diindeno[2,1-e:1′,2′-g]isoindole-3,11-diyl)-
dibenzaldehyde (8e). Yellowish-green powder. Yield: 62%; mp
1
248−250 °C; H NMR (300 MHz, CDCl3) δ 10.09 (s, 2H), 8.13 (s,
2H), 7.97 (d, J = 8.2 Hz, 4H), 7.79 (d, J = 8.2 Hz, 4H), 7.63 (s, 2H),
4.21 (s, 4H), 3.99 (s, 6H), 3.63 (t, J = 7.5 Hz, 2H), 1.68−1.58
(m, 3H), 0.97 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ
191.9, 168.6, 156.2, 144.4, 142.1, 142.0, 141.2, 138.5, 135.2, 130.4,
130.2, 129.6, 127.5, 124.6, 107.6, 56.5, 37.5, 36.4, 35.1, 26.0, 22.4; HR
ESI-MS m/z calcd for [M + H+]+ C43H36NO6, 662.2537, found
662.2537.
4H), 4.06 (s, 6H); 13C NMR (125 MHz, DMSO-d6) δ 163.4, 155.3,
144.1, 143.1, 139.7, 139.3, 130.5, 124.4, 113.4, 108.5, 57.1, 35.1; HR
EI-MS m/z calcd for [M]+ C24H14Br2O5, 539.9208, found 539.9202.
3,11-Dibromo-7-isopentyl-2,12-dimethoxy-5H-diindeno-
[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (7). The mixture of
compound 4 (200 mg, 0.37 mmol), isoamylamine (322 mg, 3.7 mmol),
imidazole (6 g) and the quantity of a microspatulum of zinc acetate
dehydrate was stirred at 130 °C for 4 h, and then ethanol (100 mL) was
added. The reaction mixture was extracted with aqueous CH2Cl2, and the
organic layer was concentrated in vacuo to give a residue, which was then
purified by chromatography with CH2Cl2 and petroleum ether (1:1, v/v) as
eluent to give 7 (192 mg, 85%) as a yellowish-green powder: mp >300 °C;
1H NMR (300 MHz, CDCl3) δ 8.00 (s, 2H), 7.86 (s, 2H), 4.22 (s, 4H),
4.05 (s, 6H), 3.71 (t, J = 7.5 Hz, 2H), 1.61 (m, 3H), 0.99 (d, J = 6.2 Hz,
6H); 13C NMR (125 MHz, CDCl3) δ 168.6, 155.3, 141.7, 140.4, 139.3,
130.3, 125.0, 113.4, 107.8, 57.0, 37.5, 36.5, 34.9, 26.0, 22.4; HR ESI-MS
m/z calcd for [M + H+]+ C29H26Br2NO4, 612.0208, found 612.0195.
General Procedure for Suzuki−Miyaura Cross Coupling.
After a mixture of compound 7 (61 mg, 0.1 mmol), K2CO3 (138 mg, 1
mmol), boronic acid (0.3 mmol) in toluene (18 mL), ethanol (12 mL)
and water (6 mL) was degassed three times and kept under argon
atmosphere, catalytic amount (∼10%) of Pd(PPh3)4 was then added.
The resulting mixture was heated to reflux for 8 h, cooled to room temp-
erature, and then poured into 5% aqueous hydrochloric acid (15 mL).
The mixture was extracted with dichloromethane (3 × 5 mL), and the
combined organic layer was washed with water and dried over anhydrous
MgSO4. The solvent was removed in vacuo to give a residue, which was
purified by chromatography.
3,11-Bis(4-chlorophenyl)-7-isopentyl-2,12-dimethoxy-5H-
diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8f). Yellow-
ish-green powder. Yield: 93%; mp 296−297 °C; 1H NMR (300 MHz,
CDCl3) δ 8.19 (s, 2H), 7.64 (s, 2H), 7.57 (d, J = 8.5 Hz, 4H), 7.44 (d,
J = 8.5 Hz, 4H), 4.32 (s, 4H), 3.97 (s, 6H), 3.74 (t, J = 7.5 Hz, 2H),
1.67−1.59 (m, 3H), 1.00 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz,
CDCl3) δ 168.4, 155.9, 141.82, 141.77, 140.3, 138.4, 136.3, 133.5,
130.8, 130.4, 128.4, 127.2, 124.1, 107.5, 56.4, 37.4, 36.2, 34.9, 26.0,
22.3; HR ESI-MS m/z calcd for [M + H+]+ C41H34Cl2NO4, 674.1859,
found 674.1858.
3,11-Bis(4-fluorophenyl)-7-isopentyl-2,12-dimethoxy-5H-
diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8g). Yellow-
ish-green powder. Yield: 92%; mp 270 °C; 1H NMR (300 MHz,
CDCl3) δ 7.98 (s, 2H), 7.56 (t, J = 6.0 Hz, 4H), 7.49 (s, 2H), 7.13
(t, J = 8.5 Hz, 4H), 4.03 (s, 4H), 3.93 (s, 6H), 3.52 (t, J = 7.2 Hz, 2H),
1.66−1.44 (m, 4H), 0.94 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz,
CDCl3) δ 168.6, 164.0, 160.7, 155.9, 141.9, 140.2, 138.4, 133.9, 131.2,
131.1, 130.7, 127.3, 124.2, 115.3, 115.0, 107.5, 56.4, 37.5, 36.2, 34.9,
26.0, 22.4; HR ESI-MS m/z calcd for [M + H+]+ C41H34F2NO4,
642.2450, found 642.2437.
7-Isopentyl-2,12-dimethoxy-3,11-diphenyl-5H-diindeno-
[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8h). Yellowish-green
powder. Yield: 85%; mp 259−261 °C; 1H NMR (300 MHz,
CDCl3) δ 8.13 (s, 2H), 7.63 (s, 2H), 7.61 (s, 4H), 7.46 (t, J = 7.3
Hz, 4H), 7.38 (m, 2H), 4.19 (s, 4H), 3.95 (s, 6H), 3.64 (t, J = 7.5 Hz,
2H), 1.69−1.58 (m, 3H), 0.97 (d, J = 6.3 Hz, 6H); 13C NMR
(75 MHz, CDCl3) δ 168.8, 156.1, 142.2, 142.1, 140.3, 138.4, 138.1,
131.9, 129.5, 128.2, 127.6, 127.4, 124.3, 107.6, 56.5, 37.5, 36.3, 35.1,
26.0, 22.4; HR ESI-MS m/z calcd for [M + H+]+ C41H36NO4,
606.2639, found 606.2637.
7-Isopentyl-2,12-dimethoxy-3,11-di(pyridin-4-yl)-5H-
diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8a). Yellow
powder. Yield: 80%; mp 270 °C (dec.); 1H NMR (300 MHz, CDCl3)
δ 8.69 (d, J = 5.8 Hz, 4H), 8.09 (s, 2H), 7.62 (s, 2H), 7.55 (d, J = 6.0
Hz, 4H), 4.18 (s, 4H), 3.99 (s, 6H), 3.61 (t, J = 7.5 Hz, 2H), 1.71−
1.52 (m, 3H), 0.97 (d, J = 6.3 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ
168.5, 156.2, 149.8, 145.7, 142.1, 142.0, 141.5, 138.5, 128.8, 127.2,
124.7, 124.1, 107.5, 56.4, 37.5, 36.3, 35.0, 26.0, 22.4; HR ESI-MS m/z
calcd for [M + H+]+ C39H34N3O4, 608.2544, found 608.2536.
7-Isopentyl-2,12-dimethoxy-3,11-bis(4-(trifluoromethyl)-
phenyl)-5H-diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione
7-Isopentyl-2,12-dimethoxy-3,11-di-p-tolyl-5H-diindeno-
[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8i). Yellowish-green
1
powder. Yield: 85%; mp 250 °C; H NMR (300 MHz, CDCl3) δ
8.20 (s, 2H), 7.65 (s, 2H), 7.53 (d, J = 8.1 Hz, 4H), 7.28 (d, J = 8.1
Hz, 4H), 4.31 (s, 4H), 3.96 (s, 6H), 3.74 (t, J = 7.5 Hz, 2H), 2.43 (s,
6H), 1.71−1.59 (m, 3H), 1.00 (d, J = 6.2 Hz, 6H); 13C NMR (75
MHz, CDCl3) δ 168.6, 156.0, 142.0, 141.9, 139.9, 138.3, 137.1, 135.2,
131.7, 129.4, 128.9, 127.4, 124.0, 107.5, 56.4, 37.5, 36.2, 35.0, 26.0,
22.4, 21.3; HR ESI-MS m/z calcd for [M + H+]+ C43H40NO4,
634.2952, found 634.2945.
1
(8b). Pale yellow powder. Yield: 91%; mp 274−275 °C; H NMR
(300 MHz, CDCl3) δ 8.18 (s, 2H), 7.78−7.67 (m, 8H), 7.64 (s, 2H),
4.28 (s, 4H), 3.98 (s, 6H), 3.70 (t, J = 7.5 Hz, 2H), 1.71−1.57 (m, 3H),
0.99 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ 168.7, 156.1,
142.2, 141.1, 138.5, 130.4, 129.9, 127.5, 125.11, 125.06, 124.7, 107.5,
56.4, 37.5, 36.4, 35.1, 26.0, 22.4; HR ESI-MS m/z calcd for [M + H+]+
C43H34F6NO4, 742.2392, found 742.2387.
7-Isopentyl-2,12-dimethoxy-3,11-di(thiophen-3-yl)-5H-
diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8j). Yellow
powder. Yield: 95%; mp 296−297 °C; 1H NMR (300 MHz,
CDCl3) δ 8.18 (s, 2H), 7.82 (s, 2H), 7.75 (dd, J = 3.0, 1.2 Hz,
2H), 7.55 (dd, J = 5.1, 1.2 Hz, 2H), 7.42 (dd, J = 5.0, 3.0 Hz, 2H), 4.31
(s, 4H), 4.05 (s, 6H), 3.73 (t, J = 7.5 Hz, 2H), 1.69−1.60 (m, 3H),
1.00 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ 168.2, 155.7,
141.6, 141.4, 139.3, 138.1, 137.7, 128.3, 125.8, 125.6, 124.7, 124.0,
123.6, 107.4, 56.1, 37.4, 36.1, 34.7, 26.1, 22.3; HR ESI-MS m/z calcd
for [M + H+]+ C37H32NO4S2, 618.1767, found 618.1766.
4,4′-(7-Isopentyl-2,12-dimethoxy-6,8-dioxo-6,7,8,9-tetrahy-
dro-5H-diindeno[2,1-e:1′,2′-g]isoindole-3,11-diyl)-
dibenzonitrile (8c). Yellowish-green powder. Yield: 66%; mp 292−
1
294 °C; H NMR (300 MHz, CDCl3) δ 8.20 (s, 2H), 7.75 (s, 8H),
7.67 (s, 2H), 4.36 (s, 4H), 3.99 (s, 6H), 3.76 (t, J = 6.0 Hz, 2H), 1.66−
1.61 (m, 3H), 1.01 (d, J = 6.2 Hz, 6H); 13C NMR (75 MHz, CDCl3) δ
168.7, 156.1, 142.8, 142.2, 142.1, 141.5, 138.6, 131.9, 130.2, 129.8, 127.4,
124.9, 118.9, 111.0, 107.5, 56.4, 37.5, 36.4, 35.1, 26.0, 22.4; HR ESI-MS
m/z calcd for [M + H+]+ C43H34N3O4, 656.2544, found 656.2541.
7-Isopentyl-2,12-dimethoxy-3,11-bis(4-nitrophenyl)-5H-
diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8d). Yellow
powder. Yield: 88%; mp 249 °C; 1H NMR (300 MHz, CDCl3) δ 8.32
7-Isopentyl-2,12-dimethoxy-3,11-bis(4-methoxyphenyl)-5H-
diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione (8k). Yellow
powder. Yield: 74%; mp 233 °C; 1H NMR (300 MHz, CDCl3) δ 7.98
(s, 2H), 7.54 (d, J = 8.6 Hz, 4H), 7.49 (s, 2H), 6.98 (d, J = 8.6 Hz, 4H),
2145
dx.doi.org/10.1021/jo4028616 | J. Org. Chem. 2014, 79, 2139−2147

The Journal of Organic Chemistry
Article
4.01 (s, 4H), 3.92 (s, 6H), 3.88 (s, 6H), 3.51 (t, J = 7.5 Hz, 2H), 1.63
− 1.44 (m, 3H), 0.94 (d, J = 6.4 Hz, 6H); 13C NMR (75 MHz,
CDCl3) δ 168.6, 159.1, 156.0, 141.94, 141.90, 139.7, 138.4, 131.3,
130.7, 130.4, 127.2, 124.0, 113.7, 107.6, 56.4, 55.3, 37.5, 36.2, 34.9,
26.0, 22.4; HR ESI-MS m/z calcd for [M + H+]+ C43H40NO6,
666.2850, found 666.2850.
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thoxy-5H-diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione
(8m). Orange powder. Yield: 65%; mp >300 °C; 1H NMR (300 MHz,
CD2Cl2) δ 8.11 (s, 2H), 7.60 (s, 2H), 7.54−6.83 (m, 28H), 4.20
(s, 4H), 3.92 (s, 6H), 3.62 (t, J = 7.1 Hz, 2H), 1.57−1.48 (m, 3H),
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131.8 131.3, 130.3, 129.3, 127.2, 124.7, 124.1, 123.1, 122.9, 107.5, 56.4,
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3,11-Bis(4-(dimethylamino)phenyl)-7-isopentyl-2,12-dime-
thoxy-5H-diindeno[2,1-e:1′,2′-g]isoindole-6,8(7H,9H)-dione
1
(8n). Red powder. Yield: 80%; mp 255 °C; H NMR (300 MHz,
CDCl3) δ 8.20 (s, 2H), 7.65 (s, 2H), 7.57 (d, J = 8.8 Hz, 4H), 6.83
(d, J = 8.9 Hz, 4H), 4.30 (s, 4H), 3.97 (s, 6H), 3.74 (t, J = 7.1 Hz, 2H),
3.03 (s, 12H), 1.67−1.59 (m, 3H), 1.00 (d, J = 6.2 Hz, 6H); 13C NMR
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131.9, 130.3, 126.9, 126.0, 123.8, 112.2, 107.7, 56.4, 40.5, 37.5, 36.2, 35.0,
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found 692.3473.
Computational Methods. DFT calculations were performed with
the Gaussian 09 program package. The geometries were optimized
using the B3LYP method with the 6-31G(d) (for C, H, and O). The
natures of the stationary points were assessed by means of vibration
frequency analysis.
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ASSOCIATED CONTENT
■
S
* Supporting Information
1
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UV−vis absorption spectra of 8h in different solvents and 8a−n
in THF; the cyclic voltammograms of 8f−i; the DFT
calculation data of 8c, 8h, 8k, 8l; and the crystallographic
information file (CIF) for 8j. These materials are available free
of charge via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
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Corresponding Authors
*E-mail: haiyanlu@ucas.ac.cn
*E-mail: cchen@iccas.ac.cn
(27) Polander, L. E.; Tiwari, S. P.; Pandey, L.; Seifried, B. M.; Zhang,
́
Q.; Barlow, S.; Risko, C.; Bredas, J.-L.; Kippelen, B.; Marder, S. R.
Chem. Mater. 2011, 23, 3408−3410.
́
(28) Tyson, D. S.; Carbaugh, A. D.; Ilhan, F.; Santos-Perez, J.;
Notes
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The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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■
We thank the National Natural Science Foundation of China
(21072220, 21272264), the National Basic Research Program
(2011CB932501), and Beijing National Laboratory for
Molecular Sciences for financial support. We also thank Yan-
Feng Dang and Prof. Zhi-Xiang Wang for their helps in
theoretical calculations.
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