Linkage position influences of anthracene and tricyanovinyl groups on the opto-electrical and photovoltaic properties of anthracene-based organic small molecules

Article abstract of DOI:10.1016/j.tet.2013.12.079

Anthracene-based small molecules incorporating an electron accepting tricyanovinyl (TCV) group was prepared to investigate the linkage position influences of the anthracene and TCV groups on the opto-electrical and photovoltaic properties of the molecules. The maximum absorptions of the anthracene-based molecules incorporating the TCV group at the phenyl group of the triphenylamine unit (TCV-TpaA_9,10T, TCV-TpaTA_9,10T, and TCV-TpaA_2,6T) or at the thiophene unit (TpaA_9,10T-TCV, TpaTA_9,10T-TCV, and TpaA_2,6T-TCV) were found to be dependent on the linkage position of the anthracene unit. The HOMO energy levels of the molecules containing TCV group at the phenyl group of the triphenylamine unit were deeper than those of the molecules containing TCV group at the thiophene unit. The solution processed small molecule organic solar cells (SMOSCs) prepared with the structure of ITO/PEDOT:PSS/TCV-TpaA_9,10T or TCV-TpaA_2,6T or TpaA_2,6T-TCV:PC₇₁BM (2:1 wt %)/LiF/Al exhibited a maximum energy conversion efficiency of 1.04%, 1.67%, and 1.95%, respectively, under AM 1.5 irradiation (100 mW cm^-2).

Full text of DOI:10.1016/j.tet.2013.12.079

Tetrahedron 70 (2014) 1176e1186
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Linkage position influences of anthracene and tricyanovinyl groups
on the opto-electrical and photovoltaic properties of anthracene-
based organic small molecules
,
,
Vellaiappillai Tamilavan a y, Myungkwan Song b y, Rajalingam Agneeswari a,
,
Myung Ho Hyun a
*
a Department of Chemistry, Chemistry Institute for Functional Materials, Pusan National University, Busan 690-735, Republic of Korea
b Advanced Functional Thin Films Department, Korea Institute of Materials Science, Changwon 641-831, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Anthracene-based small molecules incorporating an electron accepting tricyanovinyl (TCV) group was
prepared to investigate the linkage position influences of the anthracene and TCV groups on the opto-
electrical and photovoltaic properties of the molecules. The maximum absorptions of the anthracene-
based molecules incorporating the TCV group at the phenyl group of the triphenylamine unit (TCV-
TpaA9,10T, TCV-TpaTA9,10T, and TCV-TpaA2,6T) or at the thiophene unit (TpaA9,10T-TCV, TpaTA9,10T-TCV,
and TpaA2,6T-TCV) were found to be dependent on the linkage position of the anthracene unit. The
HOMO energy levels of the molecules containing TCV group at the phenyl group of the triphenylamine
unit were deeper than those of the molecules containing TCV group at the thiophene unit. The solution
processed small molecule organic solar cells (SMOSCs) prepared with the structure of ITO/PEDOT:PSS/
TCV-TpaA9,10T or TCV-TpaA2,6T or TpaA2,6T-TCV:PC71BM (2:1 wt %)/LiF/Al exhibited a maximum energy
conversion efficiency of 1.04%, 1.67%, and 1.95%, respectively, under AM 1.5 irradiation (100 mW cmꢀ2).
Ó 2014 Elsevier Ltd. All rights reserved.
Received 25 November 2013
Received in revised form 24 December 2013
Accepted 25 December 2013
Available online 3 January 2014
Keywords:
Bulk heterojunction solar cell
Small molecule organic solar cell
Anthracene
Tricyanovinyl
Triphenylamine
1. Introduction
such as facile synthesis and purification at low cost, reproducibility
of the purity and easy structural modification of molecules to tune
The bulk heterojunction solar cells (BHJ) containing the photo-
active layer made up with the bi-continuous network of electron
donating p-conjugated material and electron accepting [6,6]-phe-
nyl-C71-butyric acid methyl ester (PC71BM) derivative are consid-
ered as a promising renewable energy production techniques due
to their advantages, such as light weight, flexible large-area device
fabrication at low cost via solution processability.1,2 The BHJ solar
their absorption and energy levels for optimizing the photovoltaic
device performances, while polymeric donor materials have some
difficulty in the reproducibility of the synthetic characteristics, such
as purity, molecular weight, regioregularity and polydispersity of
each batch of the polymerization.11 In this instance, the electron
donating polymers were replaced with organic small molecules in
BHJ solar cells and the maximum PCE of the small molecule-based
BHJ solar cells (Small Molecule Organic Solar Cells, SMOSCs) was
rapidly improved up to 8.6%.12e23 The high PCE of the SMOSCs in-
spired us to develop new low band gap organic small molecules for
SMOSCs application.
cells prepared with the p-conjugated polymer as an electron donor
and PC71BM as an electron acceptor (polymer-based BHJ solar cells,
PSCs) gave the maximum solar to electrical energy conversion
efficiency of up to 9.2% for single layer PSCs2e7 and 10.6% for tan-
dem structured PSCs.8e10 The high power conversion efficiency
The recent progress of anthracene-based PSCs,24,25 dye sensi-
tized solar cells (DSSCs)26,27 and organic thin film transistor
(OTFTs)28e30 displayed impressive carrier mobility and high energy
conversion efficiency. The planar structured and highly crystalline
anthracene chromophore might be the important factors for the
impressive carrier mobility and high energy conversion efficiency.
In this instance, we expect that the insertion of anthracene chro-
(PCE) of the PSCs induced researcher to evaluate the potential of p-
conjugated organic small molecules in BHJ solar cells application.
Organic small molecules are believed to be a superior candidate
over polymeric donor materials due to their crucial advantages,
mophore as a
p-conjugation linker in organic small molecules
* Corresponding author. Department of Chemistry, Pusan National University,
Busan 609-735, Korea. Tel.: þ82 51 510 2245; fax: þ82 51 516 7421; e-mail address:
mhhyun@pusan.ac.kr (M.H. Hyun).
might induce broad absorption and high carrier mobility, and
consequently, offer high PCE in SMOSCs. To the best of our knowl-
edge anthracene-based small molecules have not yet been applied
y
V. Tamilavan and M. Song made equal contribution to this work.
0040-4020/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.12.079

V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
1177
to SMOSCs. In this anticipation, we liked anthracene moiety with
strong electron donating triphenylamine and thiophene units via
9,10- and 2,6-positions of anthracene. To extend the absorptions of
final molecules towards longer wavelength region of the solar
spectrum or to lower their optical band gaps, we have been in-
terested in incorporating cyano functional group on their back
bone. Among the reported cyano functional groups, tricyanovinyl
(TCV, eC(CN)]C(CN)2) group was found to be quite efficient to
lower the band gap of the organic molecules31 compared with
monocyano (eCH]CHCN), dicyano (eCH]C(CN)2 and DCBP) and
tricyanofuran (TCF) groups.32e34 In addition, our recent study evi-
compound 3 and di-brominated compound along with unreacted
compound 2. The mixture was separated by using column chro-
matography to afford compound 3. Then, the Suzuki coupling re-
action between 4-(diphenylamino)phenylboronic acid and each of
compounds 1 and 3 afforded compounds 4 and 5, respectively. Fi-
nally, the 9,10-linked anthracene-based molecules namely TCV-
TpaA9,10T and TCV-TpaTA9,10T containing the TCV group at the
phenyl group of the triphenylamine unit of the molecules were
obtained by treating each of compounds 4 and 5 with tetracyano-
ethylene (TCNE) in DMF. Notably, the reaction rate between com-
pound 4 or 5 and TCNE was very slow and to increase the reaction
rate and yield at least 10 equiv of TCNE were used. Even though
10 equiv of TCNE were used, only one TCV group was found to be
introduced on one phenyl ring of the triphenylamine unit possibly
because the TCV group introduced first is expected to decrease the
electron density of the other phenyl ring and, consequently, inhibit
the reaction between TCNE and the second phenyl ring. The color of
TCV-TpaA9,10T, TCV-TpaTA9,10T was intense blue. The NMR and high
resolution mass analysis evidenced that the molecules obtained
from the above reaction contain only one TCV group attached on
the phenyl group of the triphenylamine unit. On the contrary, when
we treated each of compounds 4 and 5 with n-BuLi and then TCNE
by using the similar reported procedure,31 9,10-linked anthracene-
based molecules namely TpaA9,10T-TCV and TpaTA9,10T-TCV con-
taining the TCV group at the thiophene unit of the molecules were
obtained. The color of TpaA9,10T-TCV and TpaTA9,10T-TCV was
brown.
dently supports that the band gaps of the relatively less
p-conju-
gated molecules are also significantly lowered with the use of TCV
group.35 To investigate the linkage position influences, we attached
the TCV group at the phenyl group of triphenylamine unit or at the
thiophene unit of 9,10- and 2,6-linked anthracene-bridged mole-
cules. Here, we wish to report the synthesis, optical, electro-
chemical and photovoltaic properties of 9,10- and 2,6-linked
anthracene-based small molecules bearing TCV at two different
positions.
2. Results and discussion
2.1. Synthesis and characterization
The general synthetic strategies for the 9,10-linked anthracene-
based molecules, such as TCV-TpaA9,10T, TpaA9,10T-TCV, TCV-Tpa-
TA9,10T, and TpaTA9,10T-TCV are outlined in Scheme 1. The Stille
coupling reaction between 9,10-dibromoanthracene and 2-(tribu-
tylstannyl)thiophene afforded a mixture of compounds 1 and 2.
After the careful separation, compound 2 was subjected to bromi-
nation by using NBS. This bromination afforded mono-brominated
To confirm the TCV group position on TCV-TpaA9,10T and TCV-
TpaTA9,10T, we treated compound 6 with 10 equiv of TCNE in DMF
at 150 ꢁC for 48 h. The two para-positions of the phenyl groups of
the triphenylamine unit of compound 6 are already occupied by the
methoxy groups. In this instance, the incorporation of the TCV
Scheme 1. Synthetic route for the synthesis of TCV-TpaA9,10T, TpaA9,10T-TCV, TCV-TpaTA9,10T, and TpaTA9,10T-TCV.

1178
V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
group into compound 6 is not expected. Indeed, we found that the
reaction did not happen under this condition. Instead, when we
treated compound 6 with n-BuLi followed by TCNE, we were able to
obtain MTpaA9,10T-TCV as a brown color solid. These results sup-
port that the direct reaction between compound 4 or 5 with TCNE
in DMF leads the TCV group incorporation on the para-position of
the phenyl group of the triphenylamine unit, while the reaction
between compounds 4, 5 or 6 with n-BuLi followed by TCNE leads
the TCV group incorporation on the end thiophene unit of the
molecules. The synthetic route to the synthesis of MTpaA9,10T-TCV
is displayed in Scheme 2.
compound 9 with n-BuLi followed by TCNE. All the synthesized
compounds were characterized by NMR and high resolution mass
spectroscopy.
2.2. Optical properties
The UVeVisible absorption spectra of the synthesized molecules
in 1.00ꢂ10ꢀ5 M chloroform solution and as thin film on glass are
presented in Fig. 1. TCV-TpaA9,10T and TCV-TpaTA9,10T showed rel-
atively weak absorption bands in the range of 300 nme450 nm and
very intense absorption bands in the range of 450 nme700 nm with
Scheme 2. Synthetic route for the synthesis of MTpaA9,10T-TCV.
To study the linkage position influences of the anthracene
chromophore, we also prepared 2,6-linked anthracene-based
molecules containing the TCV group at the phenyl group of the
triphenylamine unit or at the thiophene unit of the molecules. The
synthetic pathway for 2,6-linked anthracene-based molecules TCV-
TpaA2,6T and TpaA2,6T-TCV is presented in Scheme 3. The key in-
termediate 7 was synthesized by using the known literature pro-
cedure.36 Compound 7 was subjected to the Stille coupling reaction
with 2-(tributylstannyl)thiophene to give compound 8, but di-
coupled product was also obtained. After the column separation,
pure compound 8 was obtained. Then, the Suzuki coupling reaction
between compound 8 and 4-(diphenylamino)phenylboronic acid
afforded compound 9. The reaction between compound 9 and TCNE
in DMF yielded TCV-TpaA2,6T containing the TCV group at the
phenyl group of the triphenylamine unit. TpaA2,6T-TCV containing
the TCV group at the thiophene unit was obtained by treating
maximum absorption at 537 nm and 553 nm, respectively, in so-
lution and at 532 nm and 553 nm, respectively, as film. On the other
hand TpaA9,10T-TCV and TpaTA9,10T-TCV showed their strong ab-
sorption bands in the range of 300 nme450 nm with maximum
absorption at 413 nm and 410 nm, respectively, in solution and at
386 nm and 370 nm, respectively, as film and quite weak absorp-
tion bands in the range of 450 nme700 nm with maximum ab-
sorption at 562 nm and 555 nm, respectively, in solution and at
573 nm and 549 nm, respectively, as film. The absorption band of
MTpaA9,10T-TCV was quite similar to that of TpaA9,10T-TCV or
TpaTA9,10T-TCV with the maximum absorption at 412 nm and
562 nm in solution and 402 nm and 564 nm as film. On the other
hand, 2,6-linked anthracene-based molecule TpaA2,6T-TCV
displayed its strong absorption bands in the range of
300 nme520 nm and 520 nme800 nm with three absorption
maximums at 364 nm, 445 nm and 645 nm both in solution and as
Scheme 3. Synthetic route for the synthesis of TCV-TpaA2,6T and TpaA2,6T-TCV.

V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
1179
Fig. 1. Absorption spectra of the molecules in chloroform (1ꢂ10ꢀ5 M) solution and as thin film on glass.
film, while TCV-TpaA2,6T showed its absorption band quite similar
to those of TCV-TpaA9,10T and TCV-TpaTA9,10T both in solution and
as film. The absorption bands of the molecules at shorter wave-
anthracene was found to be poor (almost perpendicular plane) for
all four 9,10-linked anthracene-based molecules TCV-TpaA9,10T,
TpaA9,10T-TCV, TCV-TpaTA9,10T, and TpaTA9,10T-TCV. Even though
length region are expected to be originated from the
pe
p* elec-
the p-conjugation between the donor (electron donating nitrogen)
tronic transitions while the bands at longer wavelength region
might be attributed to the internal chare transfer (ICT) between the
donor and acceptor units.
and acceptor groups (TCV group) is quite short for compounds TCV-
TpaA9,10T and TCV-TpaTA9,10T compared with their structural iso-
mers TpaA9,10T-TCV and TpaTA9,10T-TCV, the efficient ICT is ex-
pected to occur due to the presence of strong electron donating
nitrogen atom near to the TCV group. On the other hand, even
The comparison of the absorption spectra of 9,10-linked
anthracene-based molecules TCV-TpaA9,10T, TpaA9,10T-TCV, TCV-
TpaTA9,10T, and TpaTA9,10T-TCV revealed that the ICT between the
donor and acceptor units quite efficiently occurred for TCV-
TpaA9,10T and TCV-TpaTA9,10T while the ICT was quite much pro-
hibited for TpaA9,10T-TCV and TpaTA9,10T-TCV. To understand those
behaviors of the compounds, we optimized structures of all newly
synthesized compounds by using Gaussian 03 and their optimized
molecular structures are presented in Fig. 2. The planarity between
the 9,10-linked anthracene and the aryl groups attached to the
though the
p-conjugation between the donor (triphenylamine
unit) and acceptor group (TCV group) is quite long for TpaA9,10T-
TCV and TpaTA9,10T-TCV compared with TCV-TpaA9,10T and TCV-
TpaTA9,10T, the ICT is expected to be quite much prohibited due to
the out of planarity of the anthracene moiety. Consequently, TCV-
TpaA9,10T and TCV-TpaTA9,10T displayed strong ICT absorption
bands from 450 nm to 700 nm while TpaA9,10T-TCV and TpaTA9,10T-
TCV showed very weak ICT absorption bands from 450 nm to
Fig. 2. The optimized structures of the molecules.

1180
V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
700 nm. The optimized structure of 2,6-linked anthracene-based
molecules, such as TCV-TpaA2,6T and TpaA2,6T-TCV shown in
Fig. 2 clearly indicates that the planarity between the 2,6-linked
anthracene unit and the neighboring aryl groups is considerably
increased compared to that of 9,10-linked anthracene-based mol-
ecules. The enhanced planarity of 2,6-linked anthracene-based
molecule TpaA2,6T-TCV allows the efficient ICT between the do-
nor and acceptor groups, and consequently, the companied elec-
The optical band gaps (Eg) of TCV-TpaA9,10T, TCV-TpaTA9,10T, and
TCV-TpaA2,6T were calculated to be 1.89 eV, 1.74 eV, and 1.74 eV,
respectively, from the onset wavelength (656 nm, 712 nm and
712 nm, respectively) of the film state absorption spectra. The
band gap values of compounds TpaA9,10T-TCV, TpaTA9,10T-TCV,
MTpaA9,10T-TCV, and TpaA2,6T-TCV were also calculated to be
1.77 eV, 1.82 eV, 1.72 eV, and 1.52 eV, respectively, from the onset
wavelength (700 nm, 681 nm, 720 nm, and 815 nm, respectively) of
the film state absorption spectra. The optical properties, such as
absorption maximum, molar absorptivity and optical band gap of
molecules are summarized in Table 1.
tronic transitions, such as
p-p* and ICT shifted their absorption
band up to 800 nm. On the other hand, even though the planarity of
TCV-TpaA2,6T is quite much improved compared to that of TCV-
TpaA9,10T or TCV-TpaTA9,10T, TCV-TpaA2,6T shows the absorption
band similar to that of TCV-TpaA9,10T or TCV-TpaTA9,10T because
Table 1
the effective
p-conjugation is extended only from the nitrogen
Optical and electrochemical properties of anthracene-based small molecules
atom of the triphenylamine unit to the TCV group in all three
molecules.
Molecule
lmax,solution εꢂ104
lmax,film Eg
HOMO LUMO
b
(nm)a
537
(Mꢀ1 cmꢀ1
)
(nm)c
(eV)d (eV)e (eV)f
To gain more insight on the relatively very weak ICT peaks for
9,10-linked anthracene-based molecules, such as TpaA9,10T-TCV,
TpaTA9,10T-TCV, MTpaA9,10T-TCV and the strong ICT peak for 2,6-
linked anthracene-based molecule TpaA2,6T-TCV, the electron
densities at the HOMO and LUMO energy levels of the molecules
were calculated from their optimized structures and presented in
Fig. 3. The electron densities at the HOMO energy levels of
TpaA9,10T-TCV, TpaTA9,10T-TCV, and MTpaA9,10T-TCV were found to
be strongly distributed on the donor units, such as triphenylamine
and thiophene units and very weakly distributed on the 9,10-linked
anthracene unit while the electron densities at the LUMO energy
levels of the molecules were found to be strongly distributed on the
thiophene and TCV groups. The lack of significant electronic overlap
in the HOMO and LUMO levels of TpaA9,10T-TCV, TpaTA9,10T-TCV,
and MTpaA9,10T-TCV due to the out of planarity of 9,10-linked an-
thracene indicates that the ICT between the donor and acceptor
units is quite much difficult or very week. In contrast, the electron
density was found to be nicely distributed throughout the electron
donor groups, such as triphenylamine and 2,6-linked anthracene at
the HOMO energy level of TpaA2,6T-TCV and the electron density
was found to be distributed partly on 2,6-linked anthracene and
fully on the thiophene and TCV groups at the LUMO energy level of
the molecule. The electronic distribution over the 2,6-linked an-
thracene unit in both HOMO and LUMO suggests that an effective
ICT occurs from the donor to acceptor through the 2,6-linked an-
thracene unit for TpaA2,6T-TCV.
TCV-TpaA9,10
TCV-TpaTA9,10T 553
TCV-TpaA2,6T
TpaA9,10T-TCV
TpaTA9,10T-TCV 410, 555
MTpaA9,10T-TCV 412, 562
T
3.1
2.8
532
553
551
1.89 ꢀ5.23 ꢀ3.34
1.74 ꢀ5.15 ꢀ3.41
1.74 ꢀ5.23 ꢀ3.49
548
3.3
413, 562
3.3, 0.3
3.5, 0.3
3.5, 0.3
3.1, 2.1
386, 573 1.77 ꢀ5.10 ꢀ3.33
370, 549 1.82 ꢀ5.06 ꢀ3.24
402, 564 1.72 ꢀ5.02 ꢀ3.30
445, 645 1.52 ꢀ5.09 ꢀ3.57
TpaA2,6T-TCV
445, 645
a
Absorption maximum measurements in chloroform (1ꢂ10ꢀ5 M).
Molar absorptivity measured from (1ꢂ10ꢀ5 M) chloroform solution.
Absorption maximum measurements in thin film on glass.
b
c
d
The optical band gap estimated from the onset wavelength of the optical
absorption.
e
The HOMO energy level was determined from cyclic voltammetry analysis.
The LUMO energy level was calculated using the equation of LUMO¼HOMOþEg.
f
2.3. Electrochemical properties
In order to evaluate the electrochemical properties of the syn-
thesized compounds, we performed the cyclic voltammetry (CV)
analysis for all seven compounds. Each of the seven compounds
coated as thin film on platinum working electrode was used to
determine the electrochemical properties with the use of Ag/AgCl
as reference electrode and platinum as counter electrode in ace-
tonitrile (ACN) containing 0.1
M tetrabutylammonium tetra-
fluoroborate (Bu4NBF4) as the supporting electrolyte. The cyclic
voltammograms of the molecules are shown in Fig. 4. From the CV
spectra, the onset oxidation potential (Eox,onset) values of the mol-
ecules were estimated and the highest occupied molecular orbital
(HOMO) energy levels were calculated from the Eox,onset values by
using the following equation of EHOMO (eV)¼ꢀ[(Eox,onset
vs Ag/
AgCl)ꢀ(Eox,ferrocene vs Ag/AgCl)]ꢀ4.8, where 4.8 eV is the energy level of
ferrocene below the vacuum level and Eonset(Fe/Feþ vs Ag/AgCl)¼0.51 V.
The Eox,onset values of TCV-TpaA9,10T, TCV-TpaTA9,10T, and TCV-
TpaA2,6T were estimated to be 0.94 V, 0.86 V, and 0.94 V, while
those of TpaA9,10T-TCV, TpaTA9,10T-TCV, MTpaA9,10T-TCV, and
TpaA2,6T-TCV were determined to be 0.81 V, 0.77 V, 0.73 V, and
0.80 V, respectively. The HOMO energy levels of TCV-TpaA9,10T,
TCV-TpaTA9,10T, and TCV-TpaA2,6
T were located in between
ꢀ5.15 eV to ꢀ5.23 eV and those of TpaA9,10T-TCV, TpaTA9,10T-TCV,
MTpaA9,10T-TCV, and TpaA2,6T-TCV were positioned in between
ꢀ5.02 eV to ꢀ5.10 eV. The HOMO energy levels of TCV-TpaA9,10T,
TCV-TpaTA9,10T, and TCV-TpaA2,6T were found to be slightly deeper
than those of TpaA9,10T-TCV, TpaTA9,10T-TCV, MTpaA9,10T-TCV, and
TpaA2,6T-TCV (see Table 1), which suggest that the incorporation of
TCV group on the phenyl group of the triphenylamine unit lowered
the HOMO level more effectively than the incorporation of TCV
group on the thiophene unit of the anthracene-based molecules.
Interestingly, the HOMO energy levels of 9,10-linked anthracene-
based molecule TCV-TpaA9,10T and 2,6-linked anthracene-based
molecule TCV-TpaA2,6T containing the TCV group on the phenyl
Fig. 3. The frontier molecular orbitals of molecules TpaA9,10T-TCV, TpaTA9,10T-TCV,
MTpaA9,10T-TCV, and TpaA2,6T-TCV.

V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
1181
Fig. 4. Cyclic voltammograms of the molecules films cast on platinum working electrode in 0.1 M Bu4NBF4/acetonitrile at 100 mV sꢀ1, potential versus Ag/AgCl.
group of triphenylamine unit were found to be identical with each
other (ꢀ5.23 eV).
1:2 wt %)/LiF/Al. The JeV characteristics of the SMOSC devices
measured under the illumination of AM 1.5 G (100 mW cmꢀ2) are
shown in Fig. 5 and their corresponding photovoltaic parameters,
such as power conversion efficiency (PCE), open circuit voltage
(Voc), current density (Jsc) and fill factor (FF) are presented in Table
2. All three molecules showed highest photovoltaic performances
for the devices constructed with the active layer made up with the
donoreacceptor ratio of 2:1 wt %. The SMOSCs fabricated from TCV-
TpaA9,10T:PC71BM (2:1 wt %) as an active layer shows the PCE of
1.04% with an Voc of 0.56 V, a Jsc of 5.08 mA cmꢀ2, and FF of 36.03%,
while the device fabricated from TCV-TpaA2,6T:PC71BM (2:1 wt %)
and TpaA2,6T-TCV:PC71BM (2:1 wt %) as an active layer shows im-
proved PCE of 1.67% with Voc of 0.61 V, a Jsc of 6.26 mA cmꢀ2, and
a FF of 43.85% and PCE of 1.95% with Voc of 0.63 V, a Jsc of
6.83 mA cmꢀ2, and a FF of 44.63%, respectively. On the other hand,
the SMOSCs constructed by using the donoreacceptor blend ratio
of 1:1 wt % or 1:2 wt % displayed decreased PCE compared to that of
the blend ratio of 2:1 wt % and their corresponding photovoltaic
parameters are presented in Table 2. Interestingly, the shunt re-
sistance was found to be relatively higher and at the same time the
series resistance was found to be lower for the device prepared
with the 2:1 wt % blends than the devices prepared with 1:1 wt %
and 1:2 wt % blends and those values are presented in Table 2.
Those results indicate that the presence of higher content of elec-
tron donating anthracene-based molecules in active layer produces
higher conversion efficiency than the presence of higher content of
electron accepting PC71BM. This result is expected to be more fa-
vorable for SMOSCs application since PC71BM is quite expensive.
The preliminary photovoltaic studies for the 9,10- and 2,6-
linked anthracene-based molecules show reasonable energy con-
version efficiencies. In this instance, the device optimization is
expected to improve the photovoltaic performances. The compar-
ison of the photovoltaic properties of TCV-TpaA9,10T and TCV-
TpaA2,6T suggests that 2,6-linked anthracene-based molecule is
superior to 9,10-linked anthracene-based molecule in terms of
energy conversion efficiency. Interestingly, the photovoltaic prop-
erties of TCV-TpaA2,6T and TpaA2,6T-TCV suggest that the Jsc and FF
are slightly improved when the TCV group was attached at the
thiophene unit of the final molecules, and consequently, the pho-
tovoltaic performances are enhanced.
In addition, the HOMO energy levels of molecules TpaA9,10T-TCV
and TpaA2,6T-TCV containing the TCV group on the thiophene
moiety were found to be almost identical (ꢀ5.10 eV and ꢀ5.09 eV,
respectively). These results revealed that the shift in the HOMO
energy levels of the anthracene-based molecules is mainly origi-
nated from the linkage position of TCV group, not from the linkage
position of anthracene chromophore. In other words, the linkage
position influence of anthracene chromophore on the HOMO en-
ergy level of the anthracene-based molecules is nil. The lowest
unoccupied molecular orbital (LUMO) energy levels of the com-
pounds were calculated by using the following equation
LUMO¼HOMOþEg, where Eg is the optical band gap values ob-
tained from the absorption spectra of the molecules. The LUMO
energy levels of the compounds were positioned in between
ꢀ3.24 eV to ꢀ3.57 eV. The HOMO and LUMO energy levels of the
molecules are presented in Table 1. The LUMO energy levels of the
newly synthesized molecules were found to be higher than that of
the LUMO level of PC71BM, which suggests that they can be utilized
as electron donor materials in the fabrication of SMOSCs with
PC71BM as an electron acceptor material.
2.4. Photovoltaic properties
To investigate the solar to electrical energy conversion efficiency
of the 9,10- and 2,6-linked anthracene-based molecules, we pre-
pared SMOSCs with each of the selected compounds, such as TCV-
TpaA9,10T, TCV-TpaA2,6T, and TpaA2,6T-TCV as an electron donor
and PC71BM as an electron acceptor. It is well known that utilizing
the donor molecules showing broad absorption band or the mol-
ecules showing their absorption band in the region of
500 nme800 nm is crucial because the current density of the
SMOSCs is directly proportional to the light harvesting ability of the
photoactive layer and the light harvesting ability is significantly
influenced by the absorption ability of the donor molecule. In this
instance, compounds TpaA9,10T-TCV, TpaTA9,10T-TCV, and
MTpaA9,10T-TCV were omitted for the preparation of SMOSCs due
to their poor absorption. Compound TCV-TpaTA9,10T was also
omitted because its opto-electrical property was quite similar to
that of compound TCV-TpaA9,10T, and consequently its photovoltaic
property was expected to be similar to that of TCV-TpaA9,10T. In our
attempt, we prepared SMOSCs with each of three compounds TCV-
TpaA9,10T, TCV-TpaA2,6T, and TpaA2,6T-TCV and PC71BM at three
different donoreacceptor ratio, such as 2:1 wt %, 1:1 wt %, and
1:2 wt % with the aim of understanding the linkage position in-
fluences on the photovoltaic properties. The SMOSCs were fabri-
cated with the device structure of ITO/PEDOT:PSS/TCV-TpaA9,10T or
TCV-TpaA2,6T or TpaA2,6T-TCV:PC71BM (2:1 wt %, 1:1 wt %, and
The external quantum efficiency (EQE) spectra of the SMOSC
devices were studied to verify the photoresponse further. The
EQE spectra for the SMOSCs prepared with the configuration of
ITO/PEDOT:PSS/TCV-TpaA9,10T or TCV-TpaA2,6
T
or TpaA2,6T-
TCV:PC71BM (2:1 wt %)/LiF/Al are represented in Fig. 6. The EQE
response of TCV-TpaA9,10T:PC71BM (2:1 wt %)-based SMOSC was
found to be in the range of 300e680 nm with maximum EQE of
45% at 511 nm while TCV-TpaA2,6T:PC71BM (2:1 wt %)-based
SMOSC showed its EQE curve up to 730 nm with EQE maximum of

1182
V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
Fig. 5. JeV characteristics of SMOSCs prepared from ITO/PEDOT:PSS/TCV-TpaA9,10T or TCV-TpaA2,6T or TpaA2,6T-TCV:PC71BM/LiF/Al under AM 1.5 irradiation (100 mW cmꢀ2).
Table 2
Solar cell performances of ITO/PEDOT:PSS/TCV-TpaA9,10T or TCV-TpaA2,6
TpaA2,6T-TCV:PC71BM (2:1 wt % and 1:1 wt % and 1:2 wt %)/LiF/Al devices
T or
Active layer
Voc
Jsc
FF (%)c PCE Rsh
(%)d
Rs
Integrated
(V)a (mA
cmꢀ2
(
U
cm2)e
(
U
cm2)f Jsc (mA
b
g
)
cmꢀ2
4.89
)
TCV-TpaA9,10T: 0.56 5.08
PC71BM
(2:1 wt %)
TCV-TpaA9,10T: 0.56 1.67
PC71BM
(1:1 wt %)
TCV-TpaA9,10T: 0.56 2.51
PC71BM
(1:2 wt %)
TCV-TpaA2,6T: 0.61 6.26
PC71BM
(2:1 wt %)
TCV-TpaA2,6T: 0.61 2.70
PC71BM
(1:1 wt %)
TCV-TpaA2,6T: 0.61 4.78
PC71BM
(1:2 wt %)
TpaA2,6T-TCV: 0.63 6.83
PC71BM
(2:1 wt %)
TpaA2,6T-TCV: 0.62 3.69
PC71BM
(1:1 wt %)
36.03 1.04 3.4ꢂ103 19
26.80 0.25 7.8ꢂ102 36
30.11 0.43 1.0ꢂ103 30
43.85 1.67 5.1ꢂ103 10
36.16 0.60 1.6ꢂ103 25
39.46 1.16 3.8ꢂ103 17
1.52
2.21
6.10
2.53
4.53
6.60
3.57
4.21
Fig. 6. IPCE spectra for the SMOSCs prepared from TCV-TpaA9,10T, TCV-TpaA2,6T, and
TpaA2,6T-TCV (2:1 wt %) as an active layer.
44.63 1.95 6.7ꢂ103
9
52% at 542 nm. Interestingly, the SMOSC containing the active
layer of TpaA2,6T-TCV:PC71BM (2:1 wt %) displayed its EQE band in
the quite broad range of 300e800 nm with three maximum EQE
values of 51% at 340 nm, 50% at 478 nm and 41% at 642 nm. The
EQE spectra were found to be red shifted in the order of TCV-
TpaA9,10T<TCV-TpaA2,6T<TpaA2,6T-TCV and the maximum EQE
values also appeared in the same order mentioned above, and
consequently, the Jsc values obtained from the JeV curves are ex-
pected in the above mentioned order and the same was found to
be correlated well with each other. Moreover, the Jsc values cal-
culated from integration of the EQE spectra concur well with the
Jsc obtained from the JeV measurements. The error range between
35.70 0.82 2.8ꢂ103 20
41.92 1.13 3.0ꢂ103 15
TpaA2,6T-TCV: 0.61 4.38
PC71BM
(1:2 wt %)
a
Open-circuit voltage.
Short-circuit current density.
Fill factor.
Power conversion efficiency.
Shunt resistance.
Series resistance.
b
c
d
e
f
g
Calculated from EQE.

V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
1183
the measured Jsc and integrated photocurrent were ca. 5%, which is
4.3. Fabrication and characterization of solar cell devices
usually in the range of 5e10%.37 Comparisons of the integrals of
the calculated photocurrent densities with those of photocurrent
densities from a solar simulator are summarized in Table 2.
4.3.1. Fabrication. The SMOSCs were constructed as follows. The
transparent ITO electrodes (12 /sq sheet resistance) coated on
U
glass were subjected to ultrasonication sequentially in detergent,
deionized water, acetone, and isopropyl alcohol to clean the
electrode. Then, the substrates were dried and poly(3,4-
3. Conclusion
ethylenedioxythiophene):poly(styrenesulfonate)
(PEDOT:PSS,
In this study, we prepared a series of anthracene-based or-
ganic small molecules for SMOSCs application. In order to in-
vestigate the linkage position influences of the anthracene and
TCV groups on the optical, electrochemical and photovoltaic
properties of organic molecules, we linked the planar structured
anthracene moiety with two different aryl groups via 9,10- and
2,6-positions and the TCV group was attached at the phenyl
group of the triphenylamine unit or at the thiophene unit of the
molecules. The 9,10-linked anthracene-based molecules showed
red shifted absorption maxima when the TCV group was in-
corporated at the phenyl group of the triphenylamine unit. On
the other hand, 2,6-linked anthracene-based molecules displayed
red shifted absorption maxima when the TCV group was in-
corporated at the thiophene unit. Both of the 9,10- and 2,6-linked
anthracene-based molecules containing the TCV group at the
phenyl group of the triphenylamine unit showed almost similar
absorption band. On the contrary, the 2,6-linked anthracene-
based molecule showed very much red shifted and broad ab-
sorption band compared to the 9,10-linked anthracene-based
molecule when the TCV group was incorporated at the thio-
phene unit. The planarity of the 2,6-linked anthracene-based
compounds was found to be much better than that of 9,10-
linked anthracene-based compounds, and consequently, the red
shifted absorption band was resulted. The HOMO energy levels of
the compounds containing TCV group at the phenyl group of the
triphenylamine unit were found to be slightly deeper than those
of the compounds containing TCV group at the thiophene unit.
The preliminary photovoltaic studies of the solution processed
SMOSCs afforded maximum conversion efficiency of 1.04% and
1.95%, respectively, for the 9,10- and 2,6-linked anthracene-based
molecules. From this study, we concluded the linkage position of
the anthracene and TCV units significantly influenced the prop-
erties of final compounds and we believe this study would be
quite useful for the design of new organic compounds for
SMOSCs application.
w50 nm) (CLEVIOUS P:IPA (1:2 v/v)) was spin-coated onto the UV-
ozone treated ITO substrates at 5000 rpm for 40 s. The ITO/
PEDOT:PSS substrates were baked in air at 150 ꢁC for 10 min.
Subsequently, the active layer (w95 nm) made up with the TCV-
TpaA9,10T or TCV-TpaA2,6T or TpaA2,6T-TCV:PC71BM blend solution
in chloroform was spin-coated onto the ITO/PEDOT:PSS substrates
at 900 rpm for 40 s. The blend solution was prepared by mixing
each of molecules TCV-TpaA9,10T, TCV-TpaA2,6T, and TpaA2,6T-TCV
with PC71BM at a weight ratio of 1:1 wt %, 2:1 wt %, and 1:2 wt % in
chloroform. Then, the ITO/PEDOT:PSS/Molecule:PC71BM substrates
were heated at 80 ꢁC for 30 min in glove box to remove the residual
solvent. After drying the solvent, the electron transporting LiF
(w0.7 nm) was spin-coated onto the active layer and subjected to
a vacuum (3ꢂ10ꢀ6 Torr) and then an Al electrode with thickness of
around 100 nm was deposited onto the LiF layer. The top metal
electrode area, comprising the active area of the solar cells, was
found to be 0.38 cm2. All fabrication steps and characterization
measurements were performed in an ambient environment with-
out a protective atmosphere.
4.3.2. Characterization of solar cell devices. The performances of the
SMOSCs were measured under simulated AM 1.5 illumination with
an irradiance of 100 mW cmꢀ2 (PEC-L11, Pecell Technologies Inc.).
The irradiance of the sunlight-simulating illumination was cali-
brated using a standard Si photodiode detector fitted with a KG5
filter. The JeV curves were recorded automatically using a Keithley
2400 SourceMeter source measurement unit. The series resistance
(Rs) and shunt resistance (Rsh) were obtained from the slope of the
dark current curves. The quantum efficiency measurements (IPCE)
were carried out by using Oriel IQE-200. Oriel IQE-200 is made up
by using 250 W quartz tungsten halogen (QTH) lamp, mono-
chromator, an optical chopper, a lock-in amplifier, and a calibrated
silicon photodetector. The thickness of the thin films was measured
using a KLA Tencor Alpha-step IQ surface profilometer with an
accuracy of ꢃ1 nm.
4. Experimental section
4.4. Synthesis
4.1. Materials and general procedure
4.4.1. Synthesis of 2-(10-bromoanthracen-9-yl)thiophene (1) and 2-
(10-(thiophen-2-yl)anthracen-9-yl)thiophene (2). A solution of
9,10-dibromoanthracene (5.0 g, 15.0 mmol) and 2-(tributyl-
stannyl)thiophene (5.70 mL, 18.0 mmol) in toluene (60 mL) was
stirred well under argon atmosphere for 30 min and then
Pd(PPh3)4 (2 mol %) was added. The solution was refluxed for
15 h under argon atmosphere, and then the solvent was com-
pletely removed by using a rotary evaporator. The residue was
dissolved in chloroform (100 mL) and washed with brine solu-
tion, and then dried over anhydrous Na2SO4. The solvent was
concentrated and the residue was purified by column chroma-
tography (silica gel, hexaneemethylene chloride¼90:10, v/v) to
afford compounds 1 and 2 as yellow solids. Compound 1: Yield
The necessary reagents were obtained from Aldrich or TCI
chemicals and used without further purification unless otherwise
noted. The common organic solvents were purified by using stan-
dard procedure and handled in a moisture-free atmosphere. Flash
column chromatography was performed on silica gel (Merck Kie-
selgel 60, 70e230 mesh).
4.2. Instruments and measurements
The nuclear magnetic resonance spectra (1H and 13C NMR)
were recorded by using 300-MHz Varian Mercury Plus spec-
trometer in deuterated chloroform as reference. The absorption
spectra were recorded by using a JASCO V-570 spectrophotometer
in chloroform and as thin films on glass at room temperature. The
cyclic voltammetry analyses of the molecules were performed by
using a CH Instruments Electrochemical Analyzer made up with
the standard three electrode system, such as Ag/AgCl and
platinum.
1.80 g (36%); 1H NMR (300 MHz, CDCl3)
7.31 (dd, 1H), 7.40e7.50 (m, 2H), 7.56e7.68 (m, 3H), 7.84 (d, 2H),
d (ppm) 7.18 (dd, 1H),
8.60 (d, 2H); 13C NMR (75 MHz, CDCl3)
d (ppm) 126.3, 127.2,
127.3, 127.4, 127.5, 128.1, 129.9, 130.4, 132.8, 138.6; HRMS (EIþ, m/
z) [mþ] calcd for C18H11BrS 337.9765, found 337.9771. Compound
2: Yield 2.1 g (41%); 1H NMR (300 MHz, CDCl3)
d
(ppm) 7.22 (dd,
2H), 7.33 (dd, 2H), 7.38e7.46 (m, 4H), 7.64 (dd, 2H), 7.84e7.92 (m,

1184
V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
4H); 13C NMR (75 MHz, CDCl3)
d
(ppm) 125.9, 126.9, 127.1, 127.4,
154.7; HRMS (EIþ, m/z) [mþ] calcd for C41H24N4S 604.1722, found
604.1725.
129.8, 130.5, 131.7, 139.1; HRMS (EIþ, m/z) [mþ] calcd for C22H14S2
342.0537, found 342.0537.
4.4.5. Synthesis of 1-(5-(10-(4-(diphenylamino)phenyl)anthracen-9-
yl)thiophen-2-yl)ethene-1,2,2-tricarbonitrile (TpaA9,10T-TCV). To
4.4.2. Synthesis of 2-(10-(5-bromothiophen-2-yl)anthracen-9-yl)
thiophene (3). To
a
stirred solution of compound
2
(2.0 g,
a stirred solution of compound 4 (0.50 g, 1.00 mmol) in dry tetra-
hydrofuran (THF, 60 mL) was added n-BuLi (2.5 M in hexane,
0.48 mL, 1.20 mmol) drop by drop at 0 ꢁC under argon atmosphere.
The solution was stirred for 30 min in the same bath and then TCNE
(0.15 g, 1.20 mmol) in dry THF (10 mL) was added in one potion at
5.85 mmol) in the mixed solvent of chloroform and acetic acid (1:1
v/v, 50 mL) was added N-bromosuccinimide (NBS, 1.05 g,
5.90 mmol) in one portion at room temperature (RT). The solution
was stirred for 12 h at rt. Then, the solution was poured into 100 mL
water and extracted with chloroform (3ꢂ30 mL). The combined
organic layer was washed with 2 N sodium hydroxide (NaOH) so-
lution until the aqueous layer became basic. Then, organic layer was
washed once with brine solution, and then dried over anhydrous
Na2SO4. The solvent was concentrated and the residue was purified
by column chromatography (silica gel, hexaneemethylene
chloride¼90:10, v/v) to afford compound 3 as a yellow solid. Yield
0
ꢁC. The solution was slowly warmed to room temperature and
stirred at rt for overnight. The solution was poured into brine so-
lution (50 mL), and the aqueous solution was extracted with ethyl
acetate (3ꢂ50 mL). The combined organic layer was dried over
anhydrous Na2SO4. The solvent was removed and the residue was
purified by silica gel column chromatography (silica gel, methylene
chloride) to afford compound TpaA9,10T-TCV as a brown solid. Yield
1.30 g (53%); 1H NMR (CDCl3, 300 MHz, ppm)
d
6.98 (d, 1H), 7.21
(dd, 1H), 7.28 (d, 1H), 7.32 (dd, 1H), 7.38e7.48 (m, 4H), 7.63 (dd, 1H),
7.84e7.96 (m, 4H); 13C NMR (75 MHz, CDCl3)
(ppm) 113.2, 126.0,
0.26 g (43%); 1H NMR (300 MHz, CDCl3)
7.28e7.54 (m, 17H), 7.72 (d, 2H), 7.89 (d, 2H), 8.36 (d, 1H); 13C NMR
(75 MHz, CDCl3) (ppm) 111.9, 112.1, 113.0, 122.9, 123.6, 124.2,125.1,
d (ppm) 7.06e7.14 (m, 2H),
d
d
126.3, 126.6, 127.0, 127.1, 127.5, 129.8, 130.2, 130.4, 131.6, 131.7, 138.9,
141.0; HRMS (EIþ, m/z) [mþ] calcd for C22H13BrS2 419.9642, found
419.9648.
125.4,125.7,127.2,127.9,129.7,130.2,131.0,131.5,132.0,132.8,135.2,
140.6, 141.2, 147.8, 156.5; HRMS (EIþ, m/z) [mþ] calcd for C41H24N4S
604.1722, found 604.1719.
4.4.3. Synthesis of N-phenyl-N-(4-(10-(thiophen-2-yl)anthracen-9-
yl)phenyl)benzenamine (4). A solution of compound 1 (1.52 g,
4.50 mmol) and 4-(diphenylamino)phenylboronic acid (1.45 g,
5.00 mmol) in toluene (30 mL) was stirred under argon for 45 min.
To this solution were added Pd(PPh3)4 (2 mol %) and aqueous 2 M
K2CO3 solution (7 mL). The mixture was heated to reflux under
argon atmosphere. After 24 h, the reaction mixture was cooled to rt
and the solvent was completely removed by using a rotary evapo-
rator. The remaining residue was dissolved in chloroform (60 mL)
and washed with brine solution, and then dried over anhydrous
Na2SO4. The solvent was concentrated and the residue was purified
by column chromatography (silica gel, hexaneemethylene
chloride¼80:20, v/v) to afford compound 4 as a yellow solid. Yield
4.4.6. Synthesis of N-phenyl-N-(4-(5-(10-(thiophen-2-yl)anthracen-
9-yl)thiophen-2-yl)phenyl)benzenamine (5). Compound 5 was syn-
thesized by using the similar synthetic procedure for the synthesis
of compound 4. In this reaction, compound 3 (1.00 g, 2.40 mmol)
and 4-(diphenylamino)phenylboronic acid (0.80 g, 2.80 mmol)
were subjected to Suzuki coupling reaction and the crude product
was purified by using column chromatography (silica gel, hex-
aneemethylene chloride¼80:20, v/v) to afford compound 5 as
a yellow solid. Yield is 1.16 g (83%); 1H NMR (300 MHz, CDCl3)
d
(ppm) 7.02e7.10 (m, 2H), 7.10e7.20 (m, 8H), 7.23 (d, 1H),
7.28e7.34 (m, 3H), 7.38e7.48 (m, 6H), 7.59 (d, 2H), 7.63 (d, 1H),
7.84e7.92 (m, 2H), 8.00e8.08 (m, 2H); 13C NMR (75 MHz, CDCl3)
d
(ppm) 122.5, 123.3, 124.1, 124.7, 125.9, 126.8, 126.9, 127.1, 127.4,
1.87 g (83%). 1H NMR (300 MHz, CDCl3)
7.22 (dd, 1H), 7.28e7.44 (m, 17H), 7.62 (dd, 1H), 7.80e7.92 (m, 4H);
13C NMR (75 MHz, CDCl3)
(ppm) 123.2, 123.4, 125.0, 125.3, 125.8,
d
(ppm) 7.04e7.12 (m, 2H),
128.5, 129.6, 129.8, 130.9, 131.6, 131.7, 137.7, 139.1, 145.9, 147.6, 147.7;
HRMS (EIþ, m/z) [mþ] calcd for C40H27NS2 585.1585, found
585.1587.
d
126.9,127.3, 127.4, 128.8,129.6,129.7,130.2,131.9, 1322, 132.6,138.7,
139.5, 147.5, 148.0; HRMS (EIþ, m/z) [mþ] calcd for C36H25NS
503.1708, found 503.1712.
4.4.7. Synthesis of N-(phenyl-4-ethene-1,2,2-tricarbonitrile)-N-phe-
nyl-4-(5-(10-(thiophen-2-yl)anthracen-9-yl)thiophen-2-yl)benzen-
amine (TCV-TpaTA9,10T). The mixture of compound 5 (0.40 g,
0.68 mmol) and TCNE (0.87 g, 6.80 mmol) in DMF (30 mL) was
heated to 140 ꢁC for 24 h. The similar workup and purification
procedures were used as described in the synthesis of TCV-
TpaA9,10T. The product (TCV-TpaTA9,10T) was obtained as a blue
4.4.4. Synthesis of N-(phenyl-4-ethene-1,2,2-tricarbonitrile)-N-phe-
nyl-4-(10-(thiophen-2-yl)anthracen-9-yl)benzenamine
(TCV-
TpaA9,10T). To a stirred solution of compound 4 (0.50 g, 1.00 mmol)
in DMF (30 mL) was added tetracyanoethylene (TCNE) (0.26 g,
2.00 mmol) at rt and the solution was slowly heated to 140 ꢁC for
12 h. The thin layer chromatography analysis indicates that the
reaction late is very slow. To the stirred solution, TCNE (0.26 g,
2.00 mmol) was added every 2 h four times at 140 ꢁC. After that, the
solution was stirred at 140 ꢁC for 12 h. Total 10 equiv of TCNE were
added. The reaction mixture was refluxed for 36 h. After that the
solution was cooled to rt and the solvent was concentrated by using
a rotary evaporator. The residue was dissolved in ethyl acetate
(50 mL) and the organic solution was washed with brine and dried
over anhydrous Na2SO4. The solution was filtered and concentrated
by using a rotary evaporator. The blue color residue was purified by
column chromatography (silica gel, methylene chloride) to afford
TCV-TpaA9,10T as a blue solid. Yield 0.50 g (83%); 1H NMR (300 MHz,
solid. Yield 0.41 g (87%); 1H NMR (300 MHz, CDCl3)
d (ppm) 7.04 (d,
2H), 7.10e7.24 (m, 4H), 7.28e7.36 (m, 4H), 7.40e7.50 (m, 5H),
7.52e7.66 (m, 4H), 7.75 (d, 2H), 7.86e7.92 (m, 2H), 7.96e8.04 (m,
3H); 13C NMR (75 MHz, CDCl3)
d (ppm) 113.2, 133.4, 114.4, 118.7,
120.8,123.3,124.0,124.7,126.0,126.1,126.7,127.0,127.2,127.4,127.5,
129.6, 129.8, 130.5, 130.9, 131.1, 131.5, 131.7, 132.5, 133.1, 138.3, 139.0,
139.5, 143.7, 144.4, 144.5, 154.4; HRMS (EIþ, m/z) [mþ] calcd for
C45H26N4S2 686.1599, found 686.1603.
4.4.8. Synthesis of 1-(5-(10-(5-(4-(diphenylamino)phenyl)thiophen-
2-yl)anthracen-9-yl)thiophen-2-yl)ethene-1,2,2-tricarbonitrile (Tpa-
TA9,10T-TCV). Compound TpaTA9,10T-TCV was synthesized by using
the similar synthetic procedure for the synthesis of compound
TpaA9,10T-TCV. In this reaction, compound 5 (0.59 g, 1.00 mmol)
was used instead of compound 4. The product (TpaTA9,10T-TCV)
was obtained as a brown solid. Yield 0.27 g (39%); 1H NMR
CDCl3)
(m, 13H), 7.64 (dd, 1H), 7.66e7.74 (m, 2H), 7.88e7.94 (dd, 2H), 8.07
(d, 2H); 13C NMR (75 MHz, CDCl3)
(ppm) 113.2, 113.4, 114.4, 118.5,
d (ppm) 7.13 (d, 2H), 7.23 (dd, 1H), 7.34 (dd, 1H), 7.38e7.58
d
120.7,125.8,125.9,126.7,126.9,127.1,127.2,127.5,127.6,129.6,129.8,
130.0,130.7,131.8, 132.6,133.3,137.1,137.9,138.4,139.2,143.9,144.5,
(300 MHz, CDCl3)
7.26e7.34 (m, 3H), 7.40e7.54 (m, 6H), 7.58 (d, 2H), 7.68e7.74 (m,
d (ppm) 7.02e7.10 (m, 2H), 7.10e7.20 (m, 8H),

V. Tamilavan et al. / Tetrahedron 70 (2014) 1176e1186
1185
2H), 8.04e8.12 (m, 2H), 8.36 (d, 1H); 13C NMR (75 MHz, CDCl3)
(ppm); 112.0, 112.1, 122.5, 123.4, 124.0, 124.8, 125.4, 125.8, 126.3,
126.8, 127.3, 127.5, 128.2, 129.6, 130.9, 131.1, 131.5, 132.8, 133.1, 133.3,
135.3, 136.5, 140.5, 146.4, 147.7, 147.8, 155.9; HRMS (EIþ, m/z) [mþ]
calcd for C45H26N4S2 686.1599, found 686.1603.
1.20e1.40 (m, 6H), 2.00e2.20 (m, 4H), 4.10e4.30 (m, 4H), 7.06e7.10
(m, 2H), 7.12e7.24 (m, 7H), 7.27e7.38 (m, 5H), 7.51 (d, 1H), 7.68 (d,
2H), 7.76 (d, 2H), 8.31 (t, 2H), 8.44 (s, 1H), 8.51 (s, 1H); 13C NMR
d
(75 MHz, CDCl3) d (ppm) 11.0, 11.1, 24.1, 24.2, 78.0, 78.1, 118.9, 119.5,
123.3, 123.6, 123.7, 123.8, 124.0, 124.3, 124.9, 125.0, 125.3, 125.4,
125.9, 128.1, 128.5, 129.6, 131.0, 135.0, 137.2, 145.1, 147.7, 147.9, 147.9,
148.0; HRMS (EIþ, m/z) [mþ] calcd for C42H37NO2S 619.2545, found
619.2549.
4.4.9. Synthesis of 4-methoxy-N-(4-methoxyphenyl)-N-(4-(10-(thio-
phen-2-yl)anthracen-9-yl)phenyl)benzenamine (6). The typical
Suzuki coupling reaction between 4-(bis(4-methoxyphenyl)amino)
phenylboronic acid (0.42 g, 1.20 mmol), which was prepared via the
known procedure,38 and compound 1 (0.34 g, 1.00 mmol) as de-
scribed in the synthesis of compound 4, followed by the typical
workup and purification by column chromatography (silica gel,
hexaneemethylene chloride¼80:20, v/v) afforded compound 6 as
4.4.13. Synthesis of N-(phenyl-4-ethene-1,2,2-tricarbonitrile)-N-
phenyl-4-(9,10-dipropoxy-2-(thiophen-2-yl)anthracen-6-yl)benzen-
amine (TCV-TpaA2,6T). The mixture of compound
9 (0.40 g,
0.65 mmol) and TCNE (0.83 g, 6.50 mmol) in DMF (30 mL) was
heated to 140 ꢁC for 6 h. The similar workup and purification pro-
cedures were used as described in the synthesis of TCV-TpaA9,10T.
The product (TCV-TpaA2,6T) was obtained as a blue solid. Yield
a yellow solid. Yield 0.51 g (91%); 1H NMR (300 MHz, CDCl3)
d (ppm)
3.83 (s, 6H), 6.90 (d, 4H), 7.08e7.24 (m, 9H), 7.31 (dd, 1H), 7.34e7.44
(m, 4H), 7.62 (dd, 1H), 7.80e7.90 (m, 4H); 13C NMR (75 MHz, CDCl3)
0.33 g (71%); 1H NMR (300 MHz, CDCl3)
d (ppm) 1.20e1.40 (m, 6H),
d
(ppm) 55.7, 115.1, 119.9, 125.2, 125.7, 126.9, 127.2, 127.3, 127.4,
2.00e2.20 (m, 4H), 4.10e4.30 (m, 4H), 7.05 (d, 2H), 7.17 (dd, 1H),
7.27e7.40 (m, 5H), 7.42e7.56 (m, 3H), 7.70e7.86 (m, 4H), 8.00 (d,
2H), 8.31 (d,1H), 8.36 (d,1H), 8.49 (d, 2H); 13C NMR (75 MHz, CDCl3)
128.6, 129.7, 130.4, 131.9, 132.0, 139.6, 141.2, 156.3; HRMS (EIþ, m/z)
[mþ] calcd for C38H29NO2S 563.1919, found 563.1921.
d
(ppm) 11.0, 11.1, 24.1, 24.2, 78.0, 78.1, 113.2, 113.4, 114.4, 118.6,
4.4.10. Synthesis of 1-(5-(10-(4-(bis(4-methoxyphenyl)amino)phe-
nyl)anthracen-9-yl)thiophen-2-yl)ethene-1,2,2-tricarbonitrile
(MTpaA9,10T-TCV). Compound MTpaA9,10T-TCV was synthesized by
using the similar synthetic procedure for the synthesis of com-
pound TpaA9,10T-TCV. Compound 6 (0.28 g, 0.50 mmol), 1.2 equiv of
n-BuLi and TCNE were used for this reaction. The product
(MTpaA9,10T-TCV) was obtained as a brown solid. Yield 0.13 g (39%);
118.9, 120.7, 123.9, 124.0, 124.6, 125.0, 125.1, 125.5, 125.7, 125.8,
127.3, 127.5, 128.5, 129.0, 130.5, 131.3, 132.5, 136.3, 139.9, 143.8,
144.5, 145.0, 148.2, 154.5; HRMS (EIþ, m/z) [mþ] calcd for
C47H36N4O2S 720.2559, found 720.2557.
4.4.14. Synthesis of 1-(5-(2-(4-(diphenylamino)phenyl)-9,10-
dipropoxyanthracen-6-yl)thiophen-2-yl)ethene-1,2,2-tricarbonitrile
(TpaA2,6T-TCV). Compound TpaA2,6T-TCV was synthesized by us-
ing the similar synthetic procedure for the synthesis of compound
TpaA9,10T-TCV. Compound 9 (0.40 g, 0.65 mmol), 1.4 equiv of n-BuLi
and TCNE were used for this reaction. The product (TpaA2,6T-TCV)
was obtained as a green solid. Yield 0.22 g (47%); 1H NMR
1H NMR (300 MHz, CDCl3)
7.10e7.25 (m, 7H), 7.10e7.25 (m, 6H), 7.71 (d, 2H), 7.91 (d, 2H), 8.35
(d, 1H); 13C NMR (75 MHz, CDCl3)
(ppm) 112.0, 112.1, 113.0, 115.1,
d (ppm) 3.83 (s, 6H), 6.92 (d, 4H),
d
119.6,124.0,125.4,125.6,127.1,127.3,128.0,129.2,130.2,131.0,131.8,
132.8, 133.3, 135.2, 140.6, 140.9, 141.6, 148.7, 156.4, 156.7; HRMS
(EIþ, m/z) [mþ] calcd for C43H28N4O2S 664.1933, found 664.1938.
(300 MHz, CDCl3)
d (ppm) 1.20e1.40 (m, 6H), 2.00e2.20 (m, 4H),
4.20e4.40 (m, 4H), 7.08 (t, 2H), 7.12e7.25 (m, 6H), 7.27e7.38 (m,
4H), 7.64e7.74 (m, 3H), 7.82 (d, 1H), 8.07 (d, 1H), 8.33 (d, 2H), 8.45
4.4.11. Synthesis of 2-(2-bromo-9,10-dipropoxyanthracen-6-yl)thio-
phene (8). A solution of compound 7 (3.00 g, 6.60 mmol), which
was prepared via the known procedure,36 and 2-(tributylstannyl)
thiophene (2.1 mL, 6.60 mmol) in toluene (50 mL) was stirred well
under argon for 30 min. To this solution was added Pd(PPh3)4
(2 mol %). The reaction mixture was heated to reflux under argon
atmosphere. After 16 h, the reaction mixture was cooled to rt and
the solvent was completely removed by using a rotary evaporator.
The remaining residue was dissolved in chloroform (60 mL) and
washed with brine solution, and then dried over anhydrous Na2SO4.
The solvent was concentrated and the residue was purified by
(s, 1H), 8.67 (s, 1H); 13C NMR (75 MHz, CDCl3)
d (ppm) 11.0, 11.2,
24.2, 24.3, 77.4, 112.4, 112.6, 113.0, 119.4, 122.7, 122.9, 123.6, 123.7,
124.0, 124.6, 125.0, 125.3, 125.5, 125.7, 126.2, 127.7, 127.9, 128.2,
129.6, 132.9, 134.2, 138.7, 141.5, 147.1, 148.1, 148.2, 149.5, 160.0;
HRMS (EIþ, m/z) [mþ] calcd for C47H36N4O2S 720.2559, found
720.2562.
Acknowledgements
This study was financially supported by the 2013 Post-Doc.
Development Program of Pusan National University.
column
chloride¼60:40, v/v) to afford compound 8 as a yellow solid. Yield
1.23 g (41%); 1H NMR (300 MHz, CDCl3)
(ppm) 1.10e1.30 (m, 6H),
chromatography
(silica
gel,
hexaneemethylene
d
References and notes
2.00e2.20 (m, 4H), 4.00e4.20 (m, 4H), 7.16 (dd, 1H), 7.36 (dd, 1H),
7.46e7.54 (m, 2H), 7.77 (dd, 1H), 8.14 (d, 1H), 8.28 (d, 1H), 8.41 (s,
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