Novel metal-free organic dyes containing linear planar 11,12-dihydroindolo[2,3-a]carbazole donor for dye-sensitized solar cells: Effects of π spacer and alkyl chain

Article abstract of DOI:10.1016/j.dyepig.2019.01.033

Three novel D?π?A type dyes DC1～3, which consisting of indolo[2,3-a]carbazole as donor scaffold linked to the acceptor/anchoring unit cyanoacetic acid via different π-spacers, were successfully designed and synthesized. The structure, photophysical and electrochemical properties, and photovoltaic properties of the three sensitizers were investigated in detail. The results indicate that the donor 11,12-bis(2-ethylhexyl)-11,12-dihydroindolo[2,3-a]carbazole with two branched alkyl chains is effective in inhibiting the intermolecular π?π aggregation effects, and the auxiliary alkyl chains in the π-bridge cause the DC3-based DSSCs to exhibit higher open circuit voltages than that of the devices based on dye DC2. Among all of the devices fabricated with the dyes, the DC3-based cells without chenodeoxycholic acid (CDCA) exhibit the best photovoltaic performance, with a short-circuit current density of 10.98 mA cm^?2, an open circuit voltage of 752 mV and a fill factor of 0.725, corresponding to a highest power conversion efficiency of 5.98% in liquid electrolyte.

Full text of DOI:10.1016/j.dyepig.2019.01.033

Dyes and Pigments 164 (2019) 213–221
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Novel metal-free organic dyes containing linear planar 11,12-dihydroindolo
[
2,3-a]carbazole donor for dye-sensitized solar cells: Effects of π spacer and
alkyl chain
a,∗
a
b
c,∗∗
Hai Zhang , Zhen-E Chen , Jiefang Hu , Yanping Hong
a
School of Chemistry and Chemical Engineering, Academician Workstation, Zunyi Normal College, Guizhou Zunyi, 563006, China
Jiangxi Vocational Technical College of Industry Trade, Nanchang, 330038, China
Jiangxi Key Laboratory of Natural Product and Functional Food, College of Food Science and Engineering, Jiangxi Agricultural University, Nanchang, 330045, China
b
c
A R T I C L E I N F O
A B S T R A C T
Keywords:
Dye-sensitized solar cells
Electron donor
Metal-free sensitizer
Co-adsorption
Three novel D−π−A type dyes DC1∼3, which consisting of indolo[2,3-a]carbazole as donor scaffold linked to
the acceptor/anchoring unit cyanoacetic acid via different π-spacers, were successfully designed and synthe-
sized. The structure, photophysical and electrochemical properties, and photovoltaic properties of the three
sensitizers were investigated in detail. The results indicate that the donor 11,12-bis(2-ethylhexyl)-11,12-dihy-
droindolo[2,3-a]carbazole with two branched alkyl chains is effective in inhibiting the intermolecular π−π
aggregation effects, and the auxiliary alkyl chains in the π-bridge cause the DC3-based DSSCs to exhibit higher
open circuit voltages than that of the devices based on dye DC2. Among all of the devices fabricated with the
dyes, the DC3-based cells without chenodeoxycholic acid (CDCA) exhibit the best photovoltaic performance,
−
2
with a short-circuit current density of 10.98 mA cm , an open circuit voltage of 752 mV and a fill factor of
0.725, corresponding to a highest power conversion efficiency of 5.98% in liquid electrolyte.
1. Introduction
phenothiazine [37–41] have been used as electron donors. Among these
donor groups, triphenylamine donor has been widely used by re-
A series of environmental pollution problems caused by burning
searchers to synthesize numerous high-efficiency sensitizers in view of
the structural deformation and the good electron donating ability.
However, when reducing molecular aggregation, the non-planar
structure of triphenylamine also inevitably decreases the degree of
conjugation inside the molecule as well as the electron transporting
ability, which is disadvantageous for the dyes to produce a wider ab-
sorption band and a higher photocurrent. Therefore, the development
of a donor unit with high-efficiency electron transport capability and
good ability to inhibit molecular aggregation is an important challenge
for researchers.
Based on the above considerations in mind, we prefer to use a fully
planarized structure as the donor unit. Besides, considering that the
rod-like conjugated structure may be easier to suppress aggregation
than the cyclic conjugated structure, herein, the linear planar structure
of the indolo[2,3-a]carbazole was finally selected as electron donor,
and three sensitizers (DC1∼3) were synthesized to evaluate their
photovoltaic properties (Fig. 1). To reduce the π−π stacking of the dye
molecules, two 2-ethylhexyl groups were integrated to the nitrogen
fossil fuels as well as the growing global energy demand make it urgent
to develop new and clean energy sources to meet the needs of industrial
production and the environment protection. Dye-sensitized solar cells
(
DSSCs), as a new generation of photovoltaic technology and an alter-
native and effective solution to the problems mentioned above, have
been received remarkable attention in the past 20 years. Up to date,
DSSCs based on ruthenium complexes [1–3], porphyrins [4–7] and
metal-free organic dyes [8–21] have made great progress and achieved
more than 10% power conversion efficiency (PCE), especially metal-
free organic dyes have extensively studied due to their variable struc-
ture and simple synthesis.
In general, a typical organic sensitizer contains a D−π−A or
D−A−π−A framework, of which the π-bridge is the focus of attention,
and various new structures have been used as π spacers to gain higher
photovoltaic performance. In contrast, the research of electron donor is
still far from sufficient. Currently, only a few structures such as tri-
phenylamine [22–30], carbazole [31–34], anthracene [35,36] and
∗
Corresponding author.
∗∗
Corresponding author.
E-mail addresses: haizhang@vip.sina.com (H. Zhang), xyqcjx@163.com (Y. Hong).
https://doi.org/10.1016/j.dyepig.2019.01.033
Received 20 September 2018; Received in revised form 20 January 2019; Accepted 22 January 2019
Available online 23 January 2019
0143-7208/ © 2019 Published by Elsevier Ltd.

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
2. Results and discussion
The synthetic routes for DC1∼3 are depicted in Scheme 1. The
synthesis of donor unit first involved the alkylation reaction on the
dihydroindolocarbazole nitrogen atom and the 2-ethylhexyl chain was
introduced into the dihydroindolocarbazole moiety to produce inter-
mediate compound 2 [42]. The bromination of the compound 2 was
performed by N-bromosuccinimde (NBS) to provide monobrominated
compound 3. Then the key intermediate compound, pinacol boronic
ester 4, was afforded by coupling of bis(pinacolato)diboron with com-
pound 3. Required precursors 5-(5-bromothieno[3,2-b]thiophen-2-yl)
thiophene-2-carbaldehyde (7) [43] and 5″-bromo-[2,2':5′,2″-terthio-
phene]-5-carbaldehyde (9) [44] were synthesized and purified ac-
cording to the references. Suzuki-Miyaura cross-coupling reaction of 2-
(3-hexylthiophen-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (11)
with 2,5-dibromothiophene under modified conditions with tetrakis
Fig. 1. Chemical structure of the dyes DC1∼3.
(
triphenylphosphine)-palladium (0) as the catalyst precursor in a bi-
atoms in the skeleton of indolo[2,3-a]carbazole. In addition, the brid-
ging units of thieno[3,2-b]thiophene + thiophene and terthiophene
were used to explore the effect of the conjugate mode on the photo-
voltaic performances of the dyes DC1 and DC2, respectively. At the
same time, in order to more effectively inhibit the aggregation of dyes,
two auxiliary hexyl groups were further attached to the thiophene ring
to obtain the dye DC3.
In this work, in order to understand the influence of this novel
planar donor structure on the photoelectric properties of DSSCs, the
photophysical, electrochemical and optoelectronic properties of these
sensitizers in liquid electrolyte and quasi-solid electrolyte were sys-
tematically investigated. Meanwhile, the effect of alkyl chains on in-
hibition of molecular aggregation was also verified by CDCA co-ad-
sorption experiments.
phasic mixture of aqueous K CO and THF afforded the compound 12.
2
3
Subsequent compound 13 was obtained via Vilsmeier-Haak formylation
reaction of compound 12, then compound 14 was obtained by bromi-
nation reaction of compound 13 using N-bromosuccinimide followed by
the Michaelis-Arbuzov reaction according to the reported literature
procedure [45]. In the next step, the corresponding aldehyde inter-
mediates 8, 10 and 15 were obtained by one-step Suzuki coupling re-
action. Finally, in the presence of glacial acetic acid and ammonium
acetate, these aldehyde derivatives were subjected to Knoevenagel
condensation reaction with tert-butyl cyanoacetate, respectively, and
the products were further hydrolyzed in trifluoroacetic acid to obtain
1
the target dyes. All the new compounds were well characterized by H
NMR, 13C NMR and HRMS spectra. Peak splitting occurs in some
NMR spectra and these values are not counted.
13
C
Scheme 1.
214

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
Fig. 3. Cyclic voltammograms curves of DC1∼3 and ferrocene/ferrocenium
internal reference.
3
Fig. 2. UV–Vis spectra of DC1∼3 in CHCl solution.
2
.1. Optical properties
ground and excited states of the molecule (ie, the possibility of forming
the charge transfer state), which facilitates hole injection from the
D−π−A type dye to the TiO valence band.
2
The UV–Vis absorption of the dyes DC1∼3 in CHCl
3
solutions are
depicted in Fig. 2, and the corresponding data are summarized in
Table 1. It can be seen that the absorption spectra of the three dyes are
very similar, exhibiting two main absorption bands at 250–350 nm and
2.2. Electrochemical properties
4
00–600 nm, respectively. The former corresponds to the π−π* tran-
sition of the conjugated system, while the latter can be attributed to the
effective charge separation state resulting from intramolecular charge
transfer (ICT) between the donor and acceptor moiety. The dye DC2,
with terthiophene as the π-bridge, has a red-shift absorption peak
Cyclic voltammogram measurements of dye sensitized films were
performed in CH CN solution containing 0.1 M TBAPF as the sup-
3
6
porting electrolyte with addition of ferrocene as the internal standard.
The first oxidation potential vs. NHE (Eox) corresponding to the highest
occupied molecular orbital (HOMO vs. NHE) is 1.01, 0.87 and 0.85 V
for DC1∼3, respectively (Fig. 3, Table 1). Apparently, their Eox are all
sufficiently positive than the iodide/triiodide redox couple (0.4 V vs.
NHE), indicating that the oxidized dyes generated by the electron in-
jection process can efficiently accept electrons from electrolyte and
regenerated. The excitation transition energies (E0-0) (2.18, 2.25 and
(
(
λ
max = 483 nm) and
a
higher molar extinction coefficient
−1
−1
ε = 40100 M cm ) compared to those of DC1 (λmax = 479 nm,
−1
−1
ε = 38400 M cm ). In addition, DC2 is also observed to have a
broader range of absorption in the visible region. Compared to those of
DC2, however, the absorption spectrum of DC3 is blue-shifted by
4
nm at the maximum absorption wavelength, and it showing a lower
molar extinction coefficient. The phenomenon can be attributed to the
spatial effect caused by the n-hexyl chains attached to the thiophene
units.
2.16 eV for DC1, DC2 and DC3, respectively) are calculated from the
intersection points (λint) of normalized UV–Vis absorption and emission
spectra of the sensitizers with the equation E0-0 = 1240/λint. The ex-
cited-state oxidation potentials (Eox*) corresponding to the LUMO le-
vels, calculated from Eox − E0-0, are −1.17, −1.38 and −1.31 V for
DC1∼3 respectively, which are more negative than the conduction
3
The fluorescence emission spectra of the three dyes in CHCl are
shown in Fig. S20 (in ESI†). A blue-shift is observed in the emission
spectra of the dye DC2, and the fluorescence intensity of DC1 and DC3
is significantly lowered with respect to DC2. Comparing the π-bridge
unit, it can be found that the dye DC1 with thieno[3,2-b]thiophene has
the strongest fluorescence emission, while when the π-bridge part are
the same (DC2 and DC3), the dye DC3 containing two alkyl chains has
a distinct red shift. Evidently, DC1 and DC3 show a larger Stokes shift
than DC2, which indicates a larger structural difference between the
band edge of TiO
2
(−0.5 V vs. NHE), indicating that the electron in-
jection process from the photo-excited dye molecule to the conduction
band of TiO is energetically permitted.
2
Table 1
Absorption and Emission Data for organic dyes in CHCl
3
.
maxa/nm
ε /M
a
−1
cm−1
λ
emb/nm
λ
intc/nm
E
oxd/V (vs. NHE)
E
0-0e/eV
E
ox*f/V (vs. NHE)
E
HOMOg/eV
E
LUMOg/eV
dye
λ
DC1
DC2
DC3
479
483
479
38400
40100
30500
666
650
668
569
551
575
1.01
0.87
0.85
2.18
2.25
2.16
−1.17
−1.38
−1.31
−5.11
−5.04
−4.94
−2.71
−2.73
−2.60
a
−5
Absorption maximum of the dyes measured in CHCl
3
with a concentration of 2 × 10 M. ε: Molar extinction coefficient at λmax.
b
c
max
Emission maxima of dye in CHCl
λ
3
excited at their λabs
.
int (λintersection) obtained from the cross point of normalized absorption and emission spectra in CHCl
3
solution.
d
CN with 0.1 M TBAPF6 as supporting electrolyte, Fc+/Fc as an internal standard, scan
The ground state oxidation potential (Eox) of dyes were measured in CH
3
rate 50 mV/s.
e
E
0-0 was estimated from the wavelength at the intersection (λint) of normalized absorption and emission spectra with the equation E0-0 = 1240/λint
.
f
The Eox* was calculated from the equation of Eox* = Eox – E0-0
E
.
g
HOMO and ELUMO by DFT calculation (B3LYP, 6–31 G (d) level).
215

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
Fig. 4. Optimized structures and electron distributions in HOMO and LUMO levels of DC1∼3.
2.3. Theoretical calculations
Density functional theory (DFT) calculations were performed using
the Gaussian 09 program suite at the B3LYP/6–31 G(d) level to gain
insight into the spatial structure and the frontier orbitals. As shown in
Fig. 4, the dihedral angle between the benzene ring and the thieno[3,2-
ο
b]thiophene ring in sensitizer DC1 is calculated to be 28.78 , while the
dihedral angle between the thieno[3,2-b]thiophene unit and the
ο
neighboring thiophene ring is calculated to be 1.06 . For the sensitizer
DC2, when the bridging unit is replaced by terthiophene, the dihedral
angle between the benzene ring and the adjacent thiophene ring is
ο
ο
2
7.71 , and the dihedral angles between the thiophene rings are 10.69
ο
and 2.68 , respectively. Further, when an auxiliary alkyl chain is in-
troduced on two thiophene rings in the sensitizer DC3, these dihedral
ο
ο
ο
angles are increased to 27.71 , 17.12 and 11.85 , respectively. It is
apparent that the sensitizer DC3 has a more twisted molecular structure
than that of DC2 and thus resulting in a worse charge delocalization,
which weakens the ICT interaction and is consistent with the absorption
spectrum in Fig. 2.
Fig. 4 shows the calculated frontier molecular orbitals of the dyes
DC1∼3. It can be clearly found that the three dyes have similar char-
acteristics in the spatial distribution of these frontier molecular orbitals,
the HOMO levels mainly delocalize on the indolo[2,3-a]carbazole
moiety with extension to the bridged thiophene moieties, while the
LUMO levels are largely π* with dominating contributions from the π-
bridge moiety (thiophene ring) and the acceptor part unit (cyanoacrylic
acid). Undoubtedly, the overlap of the HOMO level and the LUMO level
facilitates the transfer of charge from the electron donor unit to the
electron acceptor unit.
2.4. Photovoltaic properties of DSSCs
The incident photo-current conversion efficiency (IPCE) action
spectra and the photocurrent-voltage (J−V) curves of liquid electro-
lyte-based DSSCs on DC1∼3 with or without CDCA are collected in
Fig. 5. Notably, the device based on dye DC1 shows the highest re-
sponse at 400–600 nm and a maximum IPCE value of 61% at 450 nm,
while the dyes DC2 and DC3 get lower IPCE values of 58% at 420 nm
and 58% at 460 nm, respectively, and the dye DC3 exhibits a wider and
higher response in the long wavelengths 440–700 nm compared to
DC2-based device. The result indicates that the introduction of thieno
Fig. 5. (a) IPCE action spectra and (b) J−V characteristics of DSSCs based on
DC1∼3 with liquid electrolyte (L: liquid DSSCs).
[
3,2-b]thiophene or n-hexylthiophene instead of the thiophene group in
the π-conjugated spacer has a positive effect on IPCE value. The IPCE
values of DSSCs co-adsorbed with 0.5 mM CDCA show a similar trend
for the three dyes, but are much lower than those of their counterparts,
indicating lower short circuit photocurrent densities (Jsc).
CDCA, the DC3-based device gives the best power conversion efficiency
(PCE) of 5.98%, having a short circuit photocurrent density (J ) of
sc
−2
10.98 mA cm , an open circuit voltage (Voc) of 752 mV, and a fill
3
As seen in Fig. 5b and Table 2, in pure solvent CHCl system without
216

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
Table 2
Photovoltaic parameters for DSSCs of organic dyes.
oca(Vocb)/mV
J
sca(Jscb)/mA·cm−2
FF (FF )/%
a
b
PCE (PCE )/%
a
b
Dye loading (mol cm−2
)
Dyes
V
−7
−7
−7
−7
−7
−8
DC1
DC2
DC3
729 (731 ± 5)
680 (680 ± 2)
752 (754 ± 3)
675 (674 ± 1)
665 (665 ± 1)
684 (684 ± 2)
707 (709 ± 7)
10.83 (10.73 ± 0.13)
9.73 (9.81 ± 0.08)
10.98 (10.95 ± 0.11)
8.28 (8.30 ± 0.10)
9.41 (9.42 ± 0.03)
8.07 (8.12 ± 0.16)
17.28 (17.01 ± 0.32)
73.21 (73.72 ± 1.32)
79.90 (78.40 ± 1.50)
72.47 (72.31 ± 0.61)
90.39 (89.22 ± 1.17)
80.47 (79.94 ± 0.53)
91.15 (90.15 ± 2.17)
68.64 (69.15 ± 0.68)
5.78 (5.78 ± 0.01)
5.28 (5.23 ± 0.05)
5.98 (5.97 ± 0.01)
5.05 (4.99 ± 0.10)
5.04 (5.01 ± 0.03)
5.03 (5.00 ± 0.03)
8.38 (8.34 ± 0.04)
2.20 × 10
2.35 × 10
1.62 × 10
1.71 × 10
2.15 × 10
6.65 × 10
/
DC1 + 0.5 mM CDCA
DC2 + 0.5 mM CDCA
DC3 + 0.5 mM CDCA
N719
2
2
TiO
2
thickness 8 + 4 μm and 0.16 cm , [dye] = 0.2 mM, dipping solvent CHCl
3
, dipping time 16 h, under AM 1.5 illumination (100 mW/cm ).
a
The best device parameters.
b
The average device parameters (obtained from five devices).
factor (FF) of 0.72. Without alkyl chain on the thiophene ring, the de-
vice fabricated by DC2 shows a higher FF than that of the DSSC based
on DC3, whereas the
J
sc and
Voc of the DC2-cell decrease to
−2
9.73 mA cm
and 680 mV, respectively, resulting in a PCE of 5.28%.
With the addition of the CDCA in the dye solution, the performance of
the DC1∼3-based devices reduce significantly, exhibiting poorer Jsc
−
2
−2
and Voc values of (8.28 mA cm , 675 mV), (9.41 mA cm , 665 mV)
−
2
and (8.07 mA cm , 684 mV), respectively, which lead to inferior PCEs
of 5.05%, 5.04% and 5.03%. The results may be attributed to the co-
adsorbed CDCA molecules occupying the binding sites on the TiO
2
film,
inducing a decrease in the amount of organic dyes loaded on the TiO
2
films. It is clear that the DC3-based device without CDCA obtain both
the highest photocurrent and photovoltage, indicating that the alkyl
substituted thiophene ring can suppress effectively dye aggregation.
The characteristic J−V and IPCE curves of DC1∼3 sensitized de-
vices based on quasi-solid-state electrolyte are shown in Fig. 6 and the
photovoltaic parameters are listed in Table 3. Compared to liquid
electrolyte, the trend of the three curves is the same. QSS-DSSC based
on DC1 gives a relatively high IPCE action spectrum with a maximum
IPCE value of 66% at 450 nm, and the response range of QSS-DSSCs
based on the three dyes are slightly broader compared to the liquid
electrolyte. As listed in Table 3, the QSS-DSSC using DC1 as sensitizer
−
2
gives a PCE of 5.14% with a Jsc value of 11.08 mA cm , a Voc of
6
82 mV and a FF of 0.681. Under the same conditions, the QSS-DSSCs
−2
based on DC2 and DC3 obtain Jsc values of 10.78 and 11.38 mA cm
,
V
oc of 655 and 705 mV and FF of 0.678 and 0.704, corresponding to
PCE values of 4.78 and 5.65%, respectively. Similarly, DC3 shows
higher PCE than that of DC1 or DC2 in QSS-DSSCs, which may be at-
tributed to its higher Jsc, and the fact that the π-bridge groups sub-
stituted by n-hexyl causes better inhibition of aggregation.
2.5. Electrochemical impedance spectroscopy analysis
Electrochemical impedance spectroscopy (EIS) was next employed
in the dark to investigate the electron recombination processes in DSSCs
based on the series of DC dyes. EIS analysis of the liquid electrolyte-
6
based DSSCs were performed over the frequency range of 0.1 Hz–10 Hz
with an applied bias set at −0.65 V. The small semicircle in the Nyquist
plot (Fig. 7) represents the electron transfer from the Pt counter elec-
−
3
trode to I
ions in the electrolyte, that is, the charge transfer resistance
at the Pt/electrolyte interface. The large semicircle in the Nyquist plot
Fig. 6. (a) IPCE action spectra and (b) J−V characteristics of DSSCs based on
DC1∼3 with quasi-solid-state electrolyte (QSS: quasi-solid-state DSSCs).
indicates the charge recombination between the injected electrons in
−
TiO
2
and I
3
ions in the electrolyte, that is, the charge transfer re-
/dye/electrolyte interface. The radius of the large
sistance at the TiO
2
3. Conclusions
semicircle in the middle-frequency region corresponds to the value of
the recombination resistance (Rrec), with a smaller Rrec value means a
larger charge recombination rate. The charge recombination resistance
decreases in the order of DC3 ﹥ DC1 ﹥ DC2, which is in good accordance
with the Voc values in the DSSCs based on these dyes.
Three novel metal-free sensitizers DC1∼3 have been developed and
applied in dye-sensitized solar cells by using a planar indolo[2,3-a]
carbazole electron donor. In an earlier study, Yi-Zhou Zhu et al. syn-
thesized three sensitizers based on triazatruxene [46]. Due to the larger
conjugate plane and the shorter alkyl chain, the photovoltage of devices
217

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
Table 3
Photovoltaic parameters for DSSCs of organic dyes.
oca(Vocb)/mV
J
sca(Jscb)/mA·cm−2
FF (FF )/%
a
b
PCE (PCE )/%
a
b
Dyes
electrolyte
V
DC1
DC2
DC3
quasi-solid
quasi-solid
quasi-solid
682 (684 ± 2)
655 (655 ± 1)
705 (706 ± 3)
11.08 (11.07 ± 0.01)
10.78 (10.84 ± 0.07)
11.38 (11.48 ± 0.10)
68.05 (67.43 ± 0.62)
67.79 (66.93 ± 0.86)
70.38 (69.29 ± 1.09)
5.14 (5.10 ± 0.04)
4.78 (4.75 ± 0.05)
5.65 (5.62 ± 0.04)
2
2
TiO
2
3
thickness 8 + 4 μm and 0.16 cm , [dye] = 0.2 mM, dipping solvent CHCl , dipping time 16 h, under AM 1.5 illumination (100 mW/cm ).
a
The best device parameters.
b
The average device parameters (obtained from five devices).
4. Experimental
4.1. Measurement and characterizations
1H and 13C NMR spectra of the all intermediate and final products
were measured on a Bruker Avance 600 MHz spectrometer by using
CDCl or THF-d and tetramethylsilane as an internal standard. The
3
8
mass spectra of the prepared compounds were carried out at Finnigan
MAT 95 XP analyzer spectrometer (Thermo Electron Corporation). For
melting point XT4B microscopic melting point apparatus was used and
uncorrected. UV3600 Plus spectrophotometer (Shimadzu Corporation)
and Hitachi F–4600 spectrophotometers were used for the measure-
ment of absorption and fluorescence spectra. Electrochemical redox
potentials were measured by Cyclic Voltammetry (CV), using three
electrode cells in a one compartment at a scan rate of 50 mV/s. The Ag/
AgCl in KCl (3 M) solution and an auxiliary platinum wire were utilized
as reference and counter electrode, respectively, while dye coated TiO
films were used as working electrode. Tetra-n-Butylammonium
Hexafluorophosphate (n-C NPF 0.1 M in CH CN was used as
2
4
H
9
)
4
6
3
supporting electrolyte. The photocurrent-voltage (J−V) characteristics
of the DSSCs were measured by Keithley 2400 source meter under si-
mulated AM 1.5 G (100 mW/cm ) illumination with a solar light si-
mulator (Pecell-L15, Japan) without mask. A 1 KW Xenon arc lamp
Fig. 7. EIS Nyquist plots for liquid DSSCs based on the three sensitizers mea-
sured in the dark under −0.65 V bias (L: liquid DSSCs).
2
(
Oriel) served as a light source and its incident light intensity was ca-
based on the three sensitizers appeared between 654 mV and 686 mV.
In addition, several novel indolo[3,2-b]carbazole-based dyes have been
reported by He Tian and Linxi Hou et al., respectively [47,48]. In order
to inhibit the aggregation of dye molecules, they all chose to introduce
two large benzene rings into indolo[3,2-b]carbazole. This strategy has
undoubtedly played a good role, devices based on these dyes exhibited
higher photovoltages, with the highest photovoltages of 768 mV
librated with a BS-520 standard silicon solar cell. The incident mono-
chromatic photon-to-current conversion efficiency (IPCE) spectra of the
DSSCs were conducted by illuminating monochromatic light from 300
to 800 nm on the basis of a PEC-S20 action spectrum measurement
system. The electrochemical impedance spectroscopy (EIS) was con-
ducted on the CS16X electrochemical workstation (Wuhan, China) in
dark condition for analyzing the internal impedance characteristics of
DSSCs by fitting the impedance spectra using Z-view software. Dye load
amount on the films was measured by desorbing with 0.1 M NaOH in
(
DDC1) and 757 mV (QX04). In this study, we tried to inhibit molecular
aggregation with a branched alkyl chain of appropriate length. The
results show that the molecular aggregation has been effectively sup-
pressed in the dyes DC1 and DC2, which is beneficial to heighten open
circuit voltages of the DSSCs based on the two dyes, and the auxiliary
alkyl chain as the π-bridge side chain in DC3 helps to further promote
this effect. Therefore, we believe that the introduction of benzene rings
or 2-ethylhexyl groups in a rod-shaped donor unit has similar effects on
inhibiting molecular aggregation, but the latter synthetic route is ob-
viously simpler.
In conclusion, we have demonstrated for the first time that electron-
rich rod structures are promising donor moieties for the development of
highly efficient sensitizers, this work provides an alternative direction
for rational molecular strategy to achieve high power conversion effi-
ciency, especially to increase electron transfer efficiency and Jsc as well
as avoiding reducing Voc. Considering the structural characteristics and
energy level distribution, it is expected that the D−A−π−A type
structure will further improve the light-harvesting ability, and thereby
increasing the photocurrent. The relative investigation is undergoing.
2
THF/H O (1:1) and measured by UV–Vis spectrum.
4
.2. Fabrication of DSSCs
The working electrode composed of mesoporous TiO
2
layer (8 μm
nanocrystalline transparent layer and 4 μm scattering layer) on FTO
glass was prepared according to previous reported procedure [49]. The
2
active area of the TiO
photovoltaic performance measurements. The TiO
mersed into a solution of the dyes (0.2 mM dye in CHCl
namely sensitization. The liquid electrolyte used in this work was
composed of 0.6 M 1-methyl-3-propylimidazolium iodide (PMII), 0.1 M
2
film was controlled to be 0.4 × 0.4 cm for
2
films were im-
) for 16 h,
3
2
guanidinium thiocyanate, 0.07 M I , 0.05 M LiI, and 0.5 M tert-butyl-
pyridine. Sodium lauryl sulfate, ammonium persulfate, sodium hydro-
gencarbonate and deionized water were heated and stirred in a constant
temperature water bath, and nitrogen was passed for 20 min. After the
resultant mixture was copolymerized with methyl methacrylate and
vinyl acetate for 1 h, added aluminum sulfate to break emulsion and
then filtered, washed with water and alcohol, respectively, and vacuum
dried to prepare the polymer [50]. The quasi-solid-state gel electrolyte
was prepared as follows: 12% (wt%) of poly(methyl methacrylate-co-
218

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
vinyl acetate) and the liquid electrolyte were mixed in 3-methox-
ypropionitrile, heated at 60–70 °C for 1 h, then cooled and repeated
several times, until all solids dissolved and a clear gel appeared.
120.19, 119.73, 112.10, 111.90, 83.91, 51.93, 51.67, 37.97, 37.67,
29.95, 29.91, 27.98, 27.82, 25.28, 25.25, 25.22, 25.18, 23.31, 23.28,
22.82, 22.80, 13.89, 13.85, 10.04, 10.03.
4.3. Synthesis and characterization of the dyes
4.3.4. Synthesis of 5-(5-(11,12-bis(2-ethylhexyl)-11,12-dihydroindolo
[2,3-a]carbazol-3-yl)thieno[3,2-b]thiophen-2-yl)thiophene-2-carbaldehyde
4.3.1. Synthesis of 11,12-bis(2-ethylhexyl)-11,12-dihydroindolo[2,3-a]
(8)
carbazole (2)
To stirred solution of 11,12-dihydroindolo[2,3-a]carbazole
2.00 g, 7.80 mmol) in 50 mL N,N-dimethylformamide (DMF) was
added KOH (1.10 g, 19.64 mmol). The mixture was stirred for 30 min at
room temperature under argon atmosphere. Then, 2-ethylhexyl bro-
mide (3.37 mL, 19.64 mmol) was slowly injected. The resulting mixture
was stirred continually for an additional 12 h. The reaction mixture was
Under argon, compound 4 (756 mg, 1.25 mmol), compound 7
(300 mg, 0.91 mmol), tetrakis(triphenylphosphine)palladium(0)
(63 mg, 0.055 mmol), potassium carbonate (502 mg, 3.64 mmol) were
dissolved in a mixture of THF/water. The solution was stirred and he-
ated to 80 °C for 16 h. After cooling, the reaction mixture was poured
into water and extracted with DCM, and the organic phase washed with
a
(
4
water, dried over anhydrous MgSO . The solvent was removed by ro-
poured into water and extracted with CH
was washed with brine and dried over anhydrous MgSO
solvent was removed, the product was purified by column chromato-
2
Cl
2
(DCM). The organic phase
. After the
tary evaporation, 8 was obtained as an orange solid by column chro-
4
matography on silica gel using PE:DCM:Acetone = 40:20:1 as the
eluent (yield: 56%, 440 mg), mp 78–81 °C. 1H NMR (CDCl
, 600 MHz,
3
graphy on silica gel using petroleum ether (PE) as the eluent (yield:
ppm): δ 9.90 (s, 1H), 8.11 (d, J = 7.2 Hz, 1H), 7.94 (s, 1H), 7.72 (d,
J = 3.6 Hz, 1H), 7.67–7,65 (m, 2H), 7.57–7.54 (m, 2H), 7.50–7.47 (m,
1H), 7.46 (s, 1H), 7.43–7.41 (m, 1H), 7.34 (d, J = 4.2 Hz, 1H),
1
87%, 3.29 g), mp 71–72 °C. H NMR (CDCl
3
, 600 MHz, ppm): δ 8.16 (d,
J = 7.2 Hz, 2H), 7.96 (s, 2H), 7.56 (d, J = 7.8 Hz, 2H), 7.49–7.47 (m,
2
1
H), 7.32–7.30 (m, 2H), 4.64–4.57 (m, 4H), 1.99–1.95 (m, 2H),
7.31–7.29 (m, 1H), 7.09–7.06 (m, 1H), 4.62–4.59 (m, 4H), 1.94–1.88
.04–0.91 (m, 6H), 0.85–0.73 (m, 10H), 0.62–0.58 (m, 12H). 13C NMR
(m, 2H), 0.95–0.52 (m, 28H). C NMR (CDCl , 150 MHz, ppm): δ
13
3
(
CDCl
3
, 150 MHz, ppm): δ 142.87, 130.40, 126.06, 124.72, 124.04,
182.53, 147.96, 147.74, 143.33, 143.02, 141.77, 140.08, 139.99,
137.52, 136.41, 130.80, 130.71, 125.90, 125.46, 125.27, 124.89,
124.20, 123.47, 122.28, 121.95, 121.74, 120.38, 120.22, 119.92,
119.24, 118.80, 116.23, 112.34, 112.20, 52.04, 51.92, 38.10, 38.01,
1
2
4
20.01, 119.86, 112.94, 111.92, 51.87, 38.15, 29.82, 27.80, 23.34,
2.80, 13.83, 10.20. HRMS (ESI, m/z): [M]+ calcd for [C34
+
44 2
H N ] :
80.3499, found: 480.3483.
2
9.88, 29.80, 27.65, 27.59, 23.52, 23.49, 22.77, 22.76, 13.82, 13.80,
+
+
4.3.2. Synthesis of 3-bromo-11,12-bis(2-ethylhexyl)-11,12-dihydroindolo
48 2 3
10.37, 10.31. HRMS (ESI, m/z): [M + K] calcd for [C45H N OS K] :
[
2,3-a]carbazole (3)
767.2560, found: 767.2563.
Under argon, compound 2 (1.66 g, 3.45 mmol) was dissolved in
100 mL DMF then N-bromosuccinimide (NBS) (615 mg, 3.45 mmol) was
4.3.5. Synthesis
of
(E)-3-(5-(5-(11,12-bis(2-ethylhexyl)-11,12-
added at 0 °C. After 2 h of reaction, the temperature was gradually
raised to room temperature, and the reaction was continued for 24 h.
The reaction mixture was poured into water and extracted with DCM,
and the organic phase washed with water, dried over anhydrous
MgSO . After the solvent was removed, the product was purified by
4
column chromatography on silica gel with PE as eluent to afford
dihydroindolo[2,3-a]carbazol-3-yl)thieno[3,2-b]thiophen-2-yl)thiophen-2-
yl)-2-cyanoacrylic acid (DC1)
A mixture of compound 8 (420 mg, 0.576 mmol), tert-butyl cya-
noacetate (244 mg, 1.73 mmol), ammonium acetate (133 mg,
1.73 mmol), and acetic acid (2 mL) in toluene (20 mL) was placed in a
flask. The solution was stirred at reflux under argon atmosphere for
3.5 h. After cooling, the reaction was quenched by addition of water
and the mixture was extracted with DCM. The organic layer was dried
compound 3 as a yellow-green solid (yield: 97%, 1.88 g), mp 72–74 °C.
1
H NMR (CDCl , 600 MHz, ppm): δ 8.95 (d, J = 7.8 Hz, 1H), 8.09–8.08
3
(
4
(
m, 2H), 7.57–7.47 (m, 4H), 7.37–7.34 (m, 1H), 7.32–7.29 (m, 1H),
.60–4.54 (m, 4H), 1.90–1.83 (m, 2H), 0.97–0.88 (m, 6H), 0.77–0.65
m, 10H), 0.59–0.54 (m, 12H). 13C NMR (CDCl
, 150 MHz, ppm): δ
4
over anhydrous MgSO and evaporated under vacuum. The ester in-
termediate was obtained as a red solid by column chromatography on
silica gel using PE:DCM:Acetone = 40:20:1 as the eluent (yield: 71%,
348 mg). The ester intermediate was stirred with trifluoroacetic acid
(20 mL) for 4 h, 100 mL of water was added and the resulting dark solid
DC1 was collected by filtration. The pure product was obtained by re-
peatedly water washing and centrifugation as a black power (yield:
3
1
1
1
2
43.38, 142.76, 131.78, 129.61, 125.92, 125.42, 125.26, 124.83,
22.78, 121.32, 120.35, 120.24, 120.00, 116.99, 112.40, 111.97,
08.33, 52.09, 51.81, 38.00, 37.83, 29.81, 29.78, 27.74, 27.70, 27.07,
+
3.35, 22.77, 13.80, 10.15, 10.12. HRMS (ESI, m/z): [M] calcd for
+
64%, 295 mg), mp 132–134 °C. 1H NMR (THF-d
0.82 (s, 1H), 8.37 (s, 1H), 8.13 (d, J = 7.8 Hz, 1H), 7.99 (s, 1H), 7.92
[
C
34
H43BrN
2
]
: 558.2604, found: 558.2605.
8
, 600 MHz, ppm): δ
1
4
.3.3. Synthesis of 11,12-bis(2-ethylhexyl)-3-(4,4,5,5-tetramethyl-1,3,2-
(s, 1H), 7.86 (d, J = 3.6 Hz, 1H), 7.66–7.61 (m, 3H), 7.53–7.52 (m, 1H),
7.48 (d, J = 3.6 Hz, 1H), 7.45–7.42 (m, 1H), 7.37–7.34 (m, 1H),
7.26–7.23 (m, 1H), 7.02–6.99 (m, 1H), 4.71–4.68 (m, 4H), 1.96–1.91
dioxaborolan-2-yl)-11,12-dihydroindolo[2,3-a]carbazole (4)
Under argon, compound 3 (4.11 g 7.34 mmol), bis(pinacolato)di-
boron (B
KOAc) (2.16 g, 22.05 mmol), dichloro[1,1‘-bis(diphenylphosphino)-
ferrocene]palladium(II) (Pd(dppf)Cl ) (323 mg, 0.441 mmol) were dis-
solved in 1,4-dioxane (100 mL). The solution was stirred and heated at
0 °C for 24 h. After cooling, the solvent was distilled off under reduced
pressure and the residue was poured into water and extracted with
DCM, the organic extract was dried over MgSO . After the solvent was
2
pin
2
) (5.6 g, 22.05 mmol), anhydrous potassium acetate
(m, 2H), 0.96–0.48 (m, 28H). 13C NMR (THF-d
8
, 150 MHz, ppm): δ
(
164.17, 148.67, 148.11, 146.47, 144.51, 144.24, 141.37, 141.17,
140.24, 137.37, 135.92, 131.87, 131.75, 126.98, 126.46, 126.15,
125.75, 125.34, 124.61, 123.14, 122.97, 122.91, 121.28, 121.02,
120.78, 120.42, 120.19, 117.07, 116.81, 113.38, 113.21, 99.99, 52.69,
2
8
52.59, 39.14, 39.05, 30.71, 30.46, 28.66, 28.23, 24.41, 24.27, 23.69,
+
4
4
23.64, 14.21, 14.15, 10.75, 10.48. HRMS (ESI, m/z): [M + NH ]
calcd for [C48H N O S ] : 813.3325, found: 813.3305.
53 4 2 3
+
removed, the product was purified by column chromatography on silica
gel using PE:DCM = 5:1 as the eluent to afford compound 4 as a brown
1
viscous oil (yield: 97%, 1.88 g). H NMR (CDCl
(
(
1
3
, 600 MHz, ppm): δ 9.11
4.3.6. Synthesis of 5''-(11,12-bis(2-ethylhexyl)-11,12-dihydroindolo[2,3-
a]carbazol-3-yl)-[2,2':5′,2″-terthiophene]-5-carbaldehyde (10)
d, J = 7.8 Hz, 1H), 8.47 (s, 1H), 8.19 (d, J = 7.8 Hz, 1H), 7.52–7.50
m, 2H), 7.45–7.43 (m, 2H), 7.30–7.27 (m, 2H), 4.58–4.51 (m, 4H),
.84–1.80 (m, 2H), 1.54 (s, 12H), 0.99–0.46 (m, 30H). C NMR
, 150 MHz, ppm): δ 143.14, 142.98, 142.97, 132.83, 130.82,
27.48, 126.33, 124.72, 124.53, 123.97, 123.14, 122.96, 120.43,
Under argon, compound 4 (700 mg, 1.15 mmol), compound 9
1
3
(300 mg,
0.84 mmol),
tetrakis(triphenylphosphine)palladium(0)
(
CDCl
3
(57 mg, 0.049 mmol), potassium carbonate (466 mg, 3.38 mmol) were
dissolved in a mixture of THF/water. The solution was stirred and
1
219

H. Zhang et al.
Dyes and Pigments 164 (2019) 213–221
heated to 80 °C for 16 h. After cooling, the reaction mixture was poured
into water and extracted with DCM, and the organic phase washed with
J = 7.8 Hz, 2H), 1.92–1.89 (m, 2H), 1.83–1.71 (m, 4H), 1.51–1.44 (m,
1
3
4H), 1.37–1.34 (m, 8H), 0.92–0.73 (m, 22H), 0.63–0.53 (m, 12H).
C
water, dried over anhydrous MgSO
tary evaporation, 10 was obtained as a dark red solid by column
chromatography on silica gel using PE:DCM = 2:1 as the eluent (yield:
4
. The solvent was removed by ro-
NMR (CDCl , 150 MHz, ppm): δ 182.66, 143.34, 142.98, 142.27,
3
141.54, 140.54, 140.34, 140.22, 139.25, 139.12, 134.17, 130.90,
130.44, 130.36, 129.63, 128.04, 126.05, 125.98, 125.69, 125.13,
124.73, 123.57, 122.36, 121.81, 121.71, 120.26, 120.20, 119.72,
115.91, 112.30, 112.14, 52.01, 51.82, 38.05, 37.94, 31.93, 31.80,
30.89, 30.48, 29.92, 29.85, 29.66, 29.49, 29.35, 27.78, 27.52, 23.53,
1
9
1
7
7
7
5%, 608 mg), mp 80–81 °C. H NMR (CDCl
3
, 600 MHz, ppm): δ 9.87 (s,
H), 8.11 (d, J = 7.2 Hz, 1H), 7.92 (s, 1H), 7.77 (d, J = 8.4 Hz, 1H),
.68 (d, J = 4.2 Hz, 1H), 7.57–7.54 (m, 2H), 7.50–7.47 (m, 1H),
.44–7.41 (m, 1H), 7.37 (d, J = 3.6 Hz, 1H), 7.32–7.25 (m, 4H),
.22–7.21 (m, 1H), 7.13–7.10 (m, 1H), 4.62–4.58 (m, 4H), 1.94–1.88
23.47, 23.44, 22.82, 22.78, 22.76, 14.27, 14.23, 13.84, 13.82, 10.34,
+
10.27, 10.16. HRMS (ESI, m/z): [M
+
Na]
calcd for
(
m, 2H), 0.95–0.71 (m, 16H), 0.64–0.52 (m, 12H). 13C NMR (CDCl
3
,
[C59 OS
H
74
N
2
3
Na]+: 945.4856, found: 945.4827.
1
1
1
1
1
2
50 MHz, ppm): δ 182.52, 147.17, 143.86, 143.34, 142.98, 141.61,
39.87, 137.54, 136.10, 134.22, 130.87, 130.56, 128.00, 127.17,
25.93, 125.59, 125.20, 124.81, 124.72, 124.45, 124.09, 123.53,
22.29, 121.93, 121.39, 120.32, 120.19, 119.84, 116.05, 112.32,
12.15, 52.00, 51.86, 38.07, 37.98, 29.84, 29.80, 23.50, 23.47, 22.83,
2.77, 22.75, 22.73, 13.81, 13.79, 10.29, 10.16. HRMS (ESI, m/z):
4.3.9. Synthesis
of
(E)-3-(5''-(11,12-bis(2-ethylhexyl)-11,12-
dihydroindolo[2,3-a]carbazol-3-yl)-3,3″-dihexyl-[2,2':5′,2″-terthiophen]-
5-yl)-2-cyanoacrylic acid (DC3)
A mixture of compound 15 (166 mg, 0.18 mmol), tert-butyl cya-
noacetate (76 mg, 0.54 mmol), ammonium acetate (42 mg, 0.54 mmol),
and acetic acid (2 mL) in toluene (20 mL) was placed in a flask. The
solution was stirred at reflux under argon atmosphere for 3.5 h. After
cooling, the reaction was quenched by addition of water and the mix-
ture was extracted with DCM. The organic layer was dried over anhy-
+
+
[
M] calcd for [C47
H
50
N
2
OS
3
]
: 754.3080, found: 754.3055.
4.3.7. Synthesis
of
(E)-3-(5''-(11,12-bis(2-ethylhexyl)-11,12-
dihydroindolo[2,3-a]carbazol-3-yl)-[2,2':5′,2″-terthiophen]-5-yl)-2-
cyanoacrylic acid (DC2)
4
drous MgSO and evaporated under vacuum. The ester intermediate
A mixture of compound 10 (560 mg, 0.74 mmol), tert-butyl cya-
noacetate (314 mg, 2.22 mmol), ammonium acetate (172 mg,
was obtained as a red solid by column chromatography on silica gel
using PE:DCM:Acetone = 60:30:1 as the eluent (yield: 66%, 125 mg).
The ester intermediate was stirred with trifluoroacetic acid (20 mL) for
4 h, 100 mL of water was added and the resulting dark solid DC3 was
collected by filtration. The pure product was obtained by repeatedly
water washing and centrifugation as a brown power (yield: 51%,
2
.22 mmol), and acetic acid (2 mL) in toluene (20 mL) was placed in a
flask. The solution was stirred at reflux under argon atmosphere for
.5 h. After cooling, the reaction was quenched by addition of water
and the mixture was extracted with DCM. The organic layer was dried
over anhydrous MgSO and evaporated under vacuum. The ester in-
3
92 mg), mp 145–147 °C. 1H NMR (THF-d
, 600 MHz, ppm): δ 8.31 (s,
4
8
termediate was obtained as a red solid by column chromatography on
silica gel using PE:DCM:Acetone = 40:20:1 as the eluent (yield: 77%,
1H), 8.13 (d, J = 7.8 Hz, 1H), 7.94 (s, 1H), 7.82 (d, J = 7.8 Hz, 1H),
7.78 (s, 1H), 7.64–7.62 (m, 2H), 7.45–7.42 (m, 2H), 7.39–7.36 (m, 1H),
7.31 (d, J = 3.6 Hz, 1H), 7.26–7.22 (m, 2H), 7.07–7.04 (m, 1H),
4.71–4.67 (m, 4H), 2.99–2.91 (m, 4H), 1.95–1.93 (m, 2H), 1.85–1.80
(m, 2H), 1.78–1.74 (m, 2H), 1.55–1.45 (m, 4H), 1.39–1.29 (m, 10H),
503 mg). The ester intermediate was stirred with trifluoroacetic acid
(
20 mL) for 4 h, 100 mL of water was added and the resulting red solid
DC2 was collected by filtration. The pure product was obtained by re-
peatedly water washing and centrifugation as a dark red power (yield:
0.92–0.48 (m, 32H). 13C NMR (THF-d
8
, 150 MHz, ppm): δ 164.15,
1
7
1
1%, 435 mg), mp 125–127 °C. H NMR (THF-d
8
, 600 MHz, ppm): δ
146.40, 144.50, 144.17, 143.43, 142.04, 141.56, 141.46, 141.29,
139.93, 135.03, 134.60, 131.94, 131.53, 131.37, 130.61, 129.35,
127.28, 127.03, 126.64, 126.06, 125.64, 124.68, 123.17, 122.80,
122.64, 121.22, 120.98, 120.62, 116.77, 116.68, 113.37, 113.19,
100.07, 52.62, 52.48, 39.08, 38.96, 32.94, 32.82, 31.86, 31.32, 30.68,
30.44, 30.32, 30.25, 28.38, 28.22, 24.27, 24.21, 23.76, 23.71, 23.68,
0.83 (s, 1H), 8.35 (s, 1H), 8.12 (d, J = 7.8 Hz, 1H), 7.94 (s, 1H), 7.82
(
7
(
0
1
1
1
1
9
2
d, J = 4.2 Hz, 1H), 7.74 (d, J = 7.8 Hz, 1H), 7.64–7.61 (m, 2H),
.50–7.47 (m, 2H), 7.45–7.42 (m, 2H), 7.39–7.33 (m, 2H), 7.25–7.23
m, 2H), 7.05–7.03 (m, 1H), 4.73–4.67 (m, 4H), 1.95–1.91 (m, 2H),
1
3
8
.95–0.47 (m, 28H). C NMR (THF-d , 150 MHz, ppm): δ 164.14,
47.17, 146.49, 144.79, 144.50, 144.21, 140.59, 140.38, 137.19,
35.83, 135.22, 131.93, 131.63, 129.06, 128.46, 126.99, 126.57,
26.10, 125.89, 125.72, 125.69, 125.37, 124.66, 123.11, 122.94,
22.39, 121.24, 120.99, 120.71, 116.92, 116.78, 113.37, 113.20,
9.90, 52.63, 52.60, 39.12, 39.03, 30.70, 30.53, 28.40, 28.21, 24.34,
4.27, 23.68, 23.65, 14.21, 14.19, 10.75, 10.63. HRMS (ESI, m/z):
23.67, 14.67, 14.63, 14.25, 14.22, 14.18, 10.72, 10.60, 10.46. HRMS
(ESI, m/z): [M]+ calcd for [C62
H
75
N
S
]
+
:
989.5016, found:
3
O
2
3
989.5052.
Acknowledgments
+
+
[
M + NH
4
]
calcd for [C50
H
55
N
4
O
2
S
3
]
: 839.3482, found: 839.3518.
This work was financially supported by the NSFC (21462054 and
1368006); Supported by the Scientific Research Fund of Guizhou
6
4
.3.8. Synthesis of 5''-(11,12-bis(2-ethylhexyl)-11,12-dihydroindolo[2,3-
Provincial Science and Technology Department (LH[2015]7036 and
[2015]4003); Supported by the Science and Technology Cooperation
talent Project of Zunyi City, China ([2016]14).
a]carbazol-3-yl)-3,3″-dihexyl-[2,2':5′,2″-terthiophene]-5-carbaldehyde
15)
Under argon, compound 4 (486 mg, 0.8 mmol), compound 14
300 mg, 0.57 mmol), tetrakis(triphenylphosphine)palladium(0)
40 mg, 0.035 mmol), potassium carbonate (317 mg, 2.3 mmol) were
(
(
(
Appendix A. Supplementary data
dissolved in a mixture of THF/water. The solution was stirred and he-
ated to 80 °C for 16 h. After cooling, the reaction mixture was poured
into water and extracted with DCM, and the organic phase washed with
Supplementary data to this article can be found online at https://
doi.org/10.1016/j.dyepig.2019.01.033.
water, dried over anhydrous MgSO
4
. The solvent was removed by ro-
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(
yield: 36%, 194 mg), mp 90–93 °C. H NMR (CDCl
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, 600 MHz, ppm): δ
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