Synthesis and electrochromic properties of star-shaped oligothiophene derivatives with triphenylamine as core

Article abstract of DOI:10.1166/jnn.2015.9652

Two star-shaped oligothiophene derivatives with triphenylamine as core, Tris[4-(2-thienyl)-phenyl]amine (3TPA) and Tris[4-(5-cyano-2-thienyl)-phenyl]amine (3TPA-3CN) were synthesized and characterized for photophysical, electrochemical and electrochromic

Full text of DOI:10.1166/jnn.2015.9652

Article
Journal of
Nanoscience and Nanotechnology
Vol. 15, 3029–3034, 2015
Copyright © 2015 American Scientific Publishers
All rights reserved
Printed in the United States of America
www.aspbs.com/jnn
Synthesis and Electrochromic Properties of Star-Shaped
Oligothiophene Derivatives with Triphenylamine as Core
Li Guan1 and Ping Liu
ꢀ∗
2ꢀ∗
1College of Pharmacy, Guangdong Pharmaceutical University, Guangzhou 510006, China
State Key Laboratory of Luminescent Materials and Devices, Research Institute of Materials Science,
South China University of Technology, Guangzhou 510640, China
2
Two star-shaped oligothiophene derivatives with triphenylamine as core, Tris[4-(2-thienyl)-
phenyl]amine (3TPA) and Tris[4-(5-cyano-2-thienyl)-phenyl]amine (3TPA-3CN) were synthesized
and characterized for photophysical, electrochemical and electrochromic properties. The results
show that introduction of cyano group to the ꢀ-position of thiophene unit of 3TPA-3CN makes the
maximum absorption red-shifted in comparison with those of 3TPA, but leads the oxidation poten-
tials shift to positive value. Two electrochromic devices were fabricated using 3TPA and 3TPA-3CN
as electroactive layer, and the electrochromic properties of both compounds were studied. 3TPA-
3
CN exhibits reversible, clear color change from yellow to orange on electrochemical doping and
dedoping. 3TPA is electropolymerized firstly, and then switches the colors when the applied potential
changes.
Delivered by Publishing Technology to: Chinese University of Hong Kong
Keywords: Oligot IhPi o: p1h 1e 7n .e2 5D 3e .r 1i v 0a 7t i .v 3e 2, TOr i pn h: eMn oy lna ,m 2i n8 e D, Ce yc a 2n 0o 1G5 r o0 u8 p: ,5 E4 l: e2 c0 trochromism.
Copyright: American Scientific Publishers
1
. INTRODUCTION
derivatives have high hole mobility and are widely used
as hole-transporting materials in organic light-emitting
Electrochromic (EC) materials exhibit a reversible change
in optical absorption or transmittance upon electrochem-
ical redox. Ever since the discovery of the EC effect,
great efforts have been made with inorganic compounds,
organic molecules, and ꢀ-conjugated polymers for dif-
ferent technological applications, such as construction of
smart windows, rear-view mirrors, optical displays, light-
emitting diodes, camouflage materials and other elec-
1
2
diodes. Many star-shaped molecules consisting of a TPA
core substituted by oligophenylenes, 2-phenylthiophene,
or fluorene have been designed and synthesized for the
applications as organic field-effect transistors (OFETs),
light-emitting diodes (LEDs) and organic photovoltaic
1
ꢁ2
1
3–22
devices.
However, the use of TPA-based materials for
electrochromic devices has been scarcely considered.
In our previous work, we have synthesized several star-
shaped oligothiophene derivatives such as X-5T, X-5T-
3
–7
trochromic devices (ECDs).
with inorganic compounds such as tungsten trioxide
WO ) and iridium dioxide (IrO ). In recent years, organic
Studies on ECDs began
2
3ꢁ24
(
2CN, et al.
It was found that these compounds showed
3
2
materials (viologens, metal phtalocyanines, conjugated
oligomers and polymers) have received much attention for
electrochromic applications because of the different col-
reversible and clear color changes on electrochromic dop-
ing and dedoping. We report herein the synthesis and prop-
erties of two star-shaped triphenylamine oligothiophenes,
which are 3TPA and 3TPA-3CN, and their application in
electrochromic devices.
8
ors observed during switching among their different redox
states. Conjugated oligomers and polymers are used as
electroactive layers due to their ease of color tuning prop-
erties, faster switching speeds, high contrast and flexible
9
–11
2. EXPERIMENTAL DETAILS
chemical-structure modification.
2
.1. Materials
Tris[4-(2-bromo)-phenyl]amine, 2-thiopheneboronic acid,
bis(triphenylphosphine)palladium dichloride (Pd(PPh ꢂ Cl ),
The triphenylamine (TPA) unit possesses a three-
dimensional structure owing to the noncoplanarity of the
three phenyl substituents, which makes molecules contain-
ing TPA unit exhibit good solubility. Furthermore, TPA
3
2
2
N -chlorosulfonyl isocyanate (CSI) and N ,N -dimethyl-
formamide (DMF) were used as received from the suppli-
ers. Dichloromethane for electrochemistry measurements
∗
Authors to whom correspondence should be addressed.
J. Nanosci. Nanotechnol. 2015, Vol. 15, No. 4
1533-4880/2015/15/3029/006
doi:10.1166/jnn.2015.9652
3029

Synthesis and Electrochromic Properties of Star-Shaped Oligothiophene Derivatives with Triphenylamine as Core
Guan and Liu
S
B(OH)2
NC
CN
S
S
S
S
+
PdCl (PPh )
2 3 2
N
CSI, DMF
N
Br
Br
THF, K CO3 aq.
2
CH Cl2
2
N
S
S
CN
Br
3
TPA
3TPA-3CN
Scheme 1. Sythetic route of the star-shaped oligothiophenes.
was dried over calcium oxide and freshly distilled prior to
use. All other chemicals were used as received.
2.3. Measurements
The H NMR and C NMR spectra (Bruker AVANCE
1
13
ꢀ
4
00) were recorded at 25 C in deuterated chloroform
2
.2. Synthesis
The synthetic routes for the target products 3TPA and
TPA-3CN are described in Scheme 1. Both of two com-
and TMS as internal standard. IR spectra were recorded
by a Bruker VECTOR33 IR spectrum. Mass spectra were
obtained using a Shimadzu GCMS-QP2010 mass spec-
trometer. The UV-vis spectra were taken as solutions in
dichloromethane on a Helio-ꢄ spectrophotometer (Thermo
Electron Corporation). Cyclic voltammetry experiments
were performed on an electrochemical analyzer (model
CHI750A). A carbon working electrode, a platinum wire
3
1
pounds were characterized by IR, HNMR and mass
spectrometry.
Tris[4-(2-thienyl)-phenyl]amine (3TPA) was prepared
by Suzuki coupling reactions according to the meth-
ods described in the literature. To a solution of
tris[4-(2-bromo)-phenyl]amine (1.45 g, 3 mmol) and
2
2
5
+
auxiliary (counter) electrode and a saturated Ag/Ag refer-
−1
-thiopheneboronic acid (1.92 g, 15 mmol) in 200 mL of
ence electrode were utilized with a scan rate of 50 mV s .
The solvent used in the experiments was dichloromethane
tetrahydrofuran (THF), were added Pd(PPh ꢀ Cl (90 mg)
3
2
2
Delivered by Publishing Technology to: Chinese University of Hong Kong
and 150 mL of 2 M aqueous K CO solution. The mix-
and the supporting electrolyte was 0.1 M tetrabutylammo-
IP: 117.253.107.32 On: Mon, 28 Dec 2015 08:54:20
ture was heated to reflux for 48 h and then poured into
nium pechlorate. Atomic force microscopy (AFM) exper-
Copyright: American Scientific Publishers
2
3
a saturated solution of ammonium chloride and extracted
iments were carried out using a SEIKO SPI3800N in
tapping mode. Thermal transition behaviors of 3TPA and
its polymer were investigated by DSC (NETZSCH DSC
204F1 Phoenix.
with dichloromethane three times. The combined organic
phase was then washed with brine and dried over anhy-
drous sodium sulfate, filtered and the solvent removed in
vacuo. The solid residue was purified by silica-gel column
chromatography to give a pale yellow crystalline solid.
1
3. RESULTS AND DISCUSSION
Yield: 0.88 g (59%). HNMR (400 MHz, CDCl , ppm):
3
3
.1. Optical Properties
7
7
.61 (d, 6H, PhH), 7.45 (d, 3H, ArH), 7.43 (d, 3H, ArH),
.12 (t, 3H, ArH), 7.09 (d, 6H, PhH). C NMR (400 MHz,
1
3
The UV-vis absorption spectra recorded for 3TPA and
3
TPA-3CN in dichloromethane solutions are showed in
CDCl , ppm), ꢁ: 145.9, 143.0, 128.7, 128.4, 126.6, 125.0,
3
∗
+
Figure 1(a). The ꢄmax for the ꢅ to ꢅ transition is
found at 366 nm for 3TPA, and 396 nm for 3TPA-3CN,
respectively. The maximum absorption of 3TPA-3CN is
red-shifted in comparison with that of 3TPA, which
can be assigned to the extension of the conjugated
ꢅ-system due to the terminal electron-withdrawing cyano
groups.
The solid-state UV-vis spectras for both 3TPA and
3TPA-3CN are shown in Figure 1(b). As expected and
are common in many conjugated oligomers, the absorp-
tion spectra of thin films show red-shifts (3TPA at 381 nm
and 3TPA-3CN at 490 nm) and slight band broaden-
ing as compared to those of the solution spectra, which
could be ascribe to a more extended structure with
fewer conformational defects because of the presence of
interchain interactions in the solid state through ꢅ–ꢅ
stacking.
1
(
24.1, 123.0. MS (APCI): m/z = 492.1 ꢂM ꢀ. ꢃ (KBr)
max
−
1
cm ): 3105, 3024, 2924, 2853, 1596, 1531, 1495.
Tris[4-(5-cyano-2-thienyl)-phenyl]amine (3TPA-3CN)
was prepared by the reaction of TPA (0.4 g, 0.81 mmol)
with CSI (0.7 mL, 8 mmol) in methylene chloride at room
temperature under a nitrogen atmosphere for 4 h, and
then DMF (0.62 mL, 8 mmol) was added. The solution
was stirred for 15 h and then hydrolyzed with water. The
aqueous solution was extracted with dichloromethane and
washed with brine and water. The solvent was removed
under reduced pressure to give 3TPA-3CN. The product
was purified by silica gel column chromatography. Yield:
1
0
.27 g (59%). H NMR (400 MHz, CDCl , ppm), ꢁ: 7.60
3
(
(
d, 3H, ArH), 7. 54 (d, 6H, PhH), 7.24 (d, 3H, ArH), 7.18
1
3
d, 6H, PhH). C-NMR (400 MHz, CDCl , ppm), ꢁ: 151.3,
3
1
(
47.5, 138.5, 127.7, 127.6, 124.7, 122.8, 114.3, 107.8. MS
+ −1
APCI): m/z = 566.2 (M ). IR (KBr, cm ): 2212 ꢂꢃ ꢀ.
CN
3030
J. Nanosci. Nanotechnol. 15, 3029–3034, 2015

Guan and Liu
Synthesis and Electrochromic Properties of Star-Shaped Oligothiophene Derivatives with Triphenylamine as Core
(
a) 1.0
(b) 1.0
0.8
3
3
TPA
TPA-3CN
3TPA
3TPA-3CN
0
0
0
0
0
.8
.6
.4
.2
.0
0.6
0.4
0.2
0.0
2
00
300
400
500
600
300
400
500
600
Wavelength(nm)
Wavelength(nm)
Figure 1. UV-vis absorption spectra of 3TPA and 3TPA-3CN: a, in CH Cl ; b, in film.
2
2
3
.2. Electrochemical Properties
influence of the morphology to its electrochromic property
remains to be further studied.
The electrochemical properties of these compounds were
investigated by cyclic voltammetry, and the results show
in Figure 2. 3TPA exhibits two oxidation waves with the
onset of potential Eox at 0.72 V versus Ag/Ag and
1
3.4. Electrochromic Properties
onset
+
In order to study the electrochromic properties of 3TPA
and 3TPA-3CN, two electrochromic devices were fabri-
cated (the structure of device showed in Fig. 4). 3TPA
and 3TPA-3CN were deposited by vacuum deposition
on indium-tin-oxide (ITO)-coated glass substrate, respec-
tively. The thicknesses of these films were about 80–
100 nm. The ITO-coated glass and a platinum wire were
serviced as the electrode. A 0.1 M solution of tetra-n-
+
onset
.25 V versus Ag/Ag and a reduction wave with Ered
at −0ꢀ68 V. 3TPA-3CN exhibits two oxidation waves with
onset
ox
+
+
E
at 0.85 V versus Ag/Ag and 1.51 V versus Ag/Ag
onset
red
and one reduction wave with E
at −0ꢀ61 V versus
+
Ag/Ag . The results suggest that the electron-withdrawing
cyano group induces an increase of the oxidation potential
and a decrease of the reduction potential compared to com-
pound 3TPA. As we reported in our previous work, only
when the substance could be oxided or reduced under the
applied voltage will the electrochrom Ci s om p yh ra i pg ph et :n .A Tm h ee rr i ec -a n Scientific Publishers
ing were carried out by applying a voltage to the electrode.
butylammonium perchlorate in acetonitrile was used as the
supporting electrolyte. Electrochemical doping and dedop-
Delivered by Publishing Technology to: Chinese University of Hong Kong
IP: 117.253.107.32 On: Mon, 28 Dec 2015 08:54:20
fore, the two compounds could be used as electrochromic
materials. Compared with 3TPA, the oxidation potential of
The color changes were monitored by a Model Helios-ꢁ
spectrophotometer (Thermo, Ltd.).
The results show that quickly reversible, clear color
change have occurred in both electrochromic systems
3
TPA-3CN is shifted to somewhat positive value due to
the electron-drawing effect of cyano group.
(
Fig. 5). When the applied external potential is raised
3
.3. Surface Morphology
from 0 to 2.6 V, the color of 3TPA-3CN film changes
from yellow to orange. When the potential is decreased
to −1ꢀ4 V, the color changes from orange to yellow. The
corresponding absorption spectral change of 3TPA-3CN
is shown in Figure 5(b). The absorbance changes were
noted as the potential was changed. When the 3TPA-3CN
The morphology of film surface of 3TPA-3CN was studied
by AFM, and the result is shown in Figure 3. The AFM
image indicates that there are many rod-like aggregations
on the surface of the active layer. These aggregations are in
nanoscale size, and arrange in a certain order. However, the
3TPA
3TPA-3CN
–1
0
1
2
–1
0
1
2
Potential(V vs Ag/Ag+)
Potential(V vs Ag/Ag+)
Figure 2. Cyclic voltammograms of 3TPA and 3TPA-3CN in CH Cl .
2
2
J. Nanosci. Nanotechnol. 15, 3029–3034, 2015
3031

Synthesis and Electrochromic Properties of Star-Shaped Oligothiophene Derivatives with Triphenylamine as Core
Guan and Liu
(a)
doping
dedoping
(b)
doping
dedoping
Figure 3. AFM image of 3TPA-3CN onto ITO/glass surface.
is oxidized, two peaks appear at about 308 nm and 406 nm
in its absorption spectrum. Upon reduction, the absorption
band at 308 nm decreases whereas the absorption bands
at 406 nm starts to intensify simultaneously. The results
show that 3TPA-3CN is an anode electrochromic material,
and its possible electrochromic mechanism is described in
Scheme 2. As the potential is increased to 2.6 V, electrons
are lost and cation radicals of 3TPA-3CN formed. At the
same time, 3TPA-3CN film changes its color from yellow
3
00
400
500
600
Wavelength(nm)
Figure 5. Electrochromism of 3TPA-3CN (a) and UV-vis absorption
spectra on electrochemical doping and dedoping (b).
between 2.6 and −0ꢀ8 V, the polymer film of P3TPA
changes its color between navy blue and yellow. The
Delivered by Publishing Technology to :U CV h- vi ni se ss pe e Uc t nr ui vme r cs hi tay n go ef Ho fo nP g3 TK P oA n gw ith different applied
to orange. When electrochemical dedoping is carried out,
IP: 117.253.107.32 On: Mon p, o2t e8 n Dt i ae l cs 2i s0 1s h5 o 0w 8n:5 i4n : 2F 0i gure 5(c). Two new absorption
cation radicals of 3TPA-3CN obtain electrons to become
Copyright: American Scientific Publishers
neutral molecules, which corresponding color change from
orange to yellow.
NC
Meanwhile, the 3TPA exhibits different electrochromic
characters from 3TPA-3CN. The color of 3TPA films is
pale yellow. When the applied potential is raised from 0
to 2.6 V, the color of 3TPA film changes from pale yel-
low to navy blue [Fig. 6(a)]. By further applying potential
down to −0ꢀ8 V, the color of the film changes from navy
blue to yellow [Fig. 6(b)]. During the progress of oxida-
tion and reduction, the film changes color between navy
blue and yellow, but the original color of 3TPA could not
be observed. Enlightened by the electropolymerization of
oligothiophene reported, we deduce that 3TPA firstly elec-
tropolymerizes (formed polymer P3TPA) and then dopes
when the potential (2.6 V) is applied continually between
the ITO electrode and the counter electrode. The neutral
P3TPA film is yellow. When the applied potential switches
S
N
S
S
NC
CN
+
e
-e
NC
S
NC
S
N
N
S
S
S
S
NC
CN
NC
CN
NC
NC
S
S
platinum
wire
ITO glass
N
N
Oligothiophene
derivatives
electrolyte
solution
S
S
S
S
NC
Scheme 2. Electrochromic mechanism of 3TPA-3CN.
J. Nanosci. Nanotechnol. 15, 3029–3034, 2015
CN
NC
CN
Figure 4. Schematic
diagram
of
electrochromic
devices:
ITO/electrochromic active layer/electrolyte solution/Pt.
3032

Guan and Liu
Synthesis and Electrochromic Properties of Star-Shaped Oligothiophene Derivatives with Triphenylamine as Core
(c)
doping
(
a)
(b)
dedoping
doping
dedoping
3
00
400
500
600
Wavelength(nm)
Figure 6. Electrochromism of 3TPA. (a): Irreversibale change; (b): Reversibale change; (c): UV-vis absorption spectra on electrochemical doping and
dedoping.
S
S
S
S
S
S
N
–e
N
N
S
N
S
S
S
S
S
S
S
S
S
+
2e
S
N
S
N
–e
+e
N
S
N
S
S
S
S
S
Delivered by Publishing Technology to: Chinese University of Hong Kong
IP: 117.253.107.32 On: Mon, 28 Dec 2015 08:54:20
Copyright: American Scientific Publishers
n
Scheme 3. Electropolymerized mechanism of 3TPA.
S
S
S
N
N
S
e
S
S
n
+
–e
S
S
S
S
S
N
S
N
N
S
N
S
S
S
S
S
n
n
S
S
S
S
S
N
S
N
N
S
N
S
S
S
S
S
n
n
Scheme 4. Electrochromic mechanism of poly(3TPA).
J. Nanosci. Nanotechnol. 15, 3029–3034, 2015
3033

Synthesis and Electrochromic Properties of Star-Shaped Oligothiophene Derivatives with Triphenylamine as Core
Guan and Liu
is found to undergo reversible, clear colour change on
electro-chemical doping and dedoping. Whereas 3TPA is
electropolymerized firstly, and then switches the colors
when the applied potential changed. These two star-shape
compounds based on thiophene and triphenylamine will be
the multipurpose materials attracted increasing attention.
before electrochromism
after electrochromism
Acknowledgments: This work was financially sup-
ported by the National Natural Science Foundation of
China (Nos. 20674022, 20774031 and 21074039), the Nat-
ural Science Foundation of Guangdong province (Nos.
S2013040013904, 2006A10702003, 2009B090300025 and
0
50
100
150
200
250
2
010A090100001) and the Ministry of Education of the
Temperature/ºC
People’s Republic of China (20090172110011).
Figure 7. DSC curves of 3TPA before and after electrochromism.
References and Notes
peaks at 319 nm and 425 nm occur upon applying pos-
itive potentials for P3TPA. As the potential is decreased
to −0ꢀ8 V, the absorption peak at 319 nm blue-shifts to
1
. R. J. Mortimer, Chem. Soc. Rev. 26, 147 (1997).
. P. R. Somani and S. Radhakrishnan, Mater. Chem. Phys. 2002, 117
(2002).
2
3
04 nm, while the other peak weakens. We describe possi-
3. B. Sankaran and J. R. Reynolds, Macromolecules, 30, 2582 (1997).
4. D. R. Rosseinsky and P. M. S. Monk, J. Electrochem. Soc. 147, 1595
ble electropolymerized mechanism of 3TPA in Scheme 3.
When a positive voltage is applied, 3TPA loses electrons
to form cation radicals, and then cation radicals react with
each other to generate dications, which rapidly obtain elec-
trons to form dimers. The dimers can also lose electrons to
generate cation radicals on positive potential. These reac-
tions are repeated continuously when the potential is main-
(2000).
5
6
. D. R. Rosseinsky and R. J. Mortimer, Adv. Mater. 13, 783 (2001).
. P. Chandrasekhar, B. J. Zay, G. C. Birur, S. Rawal, E. A. Pierson,
L. Kauder, and T. Swanson, Adv. Funct. Mater. 12, 95 (2002).
. H. Meng, D. Tucker, S. Chaffins, Y. Chen, R. Helgeson, B. Dunn,
and F. Wudl, Adv. Mater. 15, 146 (2003).
7
8. R. Mortimer, J. Electrochim Acta. 44, 2971 (1999).
9. B. Yigitsoy, S. Varis, C. Tanyeli, I. M. Akhmedov, and L. Toppare,
tained until a polyme Dr ies li fvo er rme ed d b. Uy pP o un b ol i xs ihd i an t gi o Tn ,e t ch he nc oo lloo gr y to: ChTihninesSoelidUFniilvmes r5s1 i 5t y, 3 o8 9f 8H( 2o 0n0 g7 ).Kong
IP: 117.253.107.32 On: Mon 1, 0 2. 8P .DC ea mc u2r l0u 1, 5A .0 C8 i: r5p 4a n: ,2 0a nd L. Toppare, J. Electroanal. Chem.
of the polymer is navy blue at −0ꢀ8 V (reduction form),
Copyright: American Scie n5 t7i f2 i,c6 1P (u2 b0 0l i4s ) h. ers
and the color is yellow. The electrochromic mechanism is
11. O. Turkarslan, A. Erden, E. Sahin, and L. Toppare, J. Macromol.
Sci. 43, 115 (2006).
showed in Scheme 4. We can speculate from above results
that oligothiophenes without ꢁ-subtitution are easily elec-
tropolymerized when a potential is applied.
In order to prove the polymerization of 3TPA during
electrochromic process, DSC testing for P3TPA (com-
pound collected from the ITO slide after electrochromic
test) and 3TPA were studied, and the results are showed
12. Y. J. Shirota, Mater. Chem. 15, 75 (2005).
13. J. Roncali, P. Leriche, and A. Cravino, Adv. Mater. 19, 2045 (2007).
14. L. L. Xue, J. T. He, X. Gu, Z. F. Yang, B. Xu, and W. J. Tian,
J. Phys. Chem. C 113, 12911 (2009).
15. C. He, Q. G. He, Y. P. Yi, G. L. Wu, F. L. Bai, Z. G. Shuai, and
Y. F. Li, J. Mater. Chem. 18, 4085 (2008).
16. G. L. Wu, G. J. Zhao, C. He, J. Zhang, Q. G. He, X. M. Chen, and
Y. F. Li, Sol. Energy Mater. Sol. Cells. 93, 108 (2009).
17. Y. Yang, J. Zhang, Y. Zhou, G. J. Zhao, C. He, Y. F. Li, M. Andersson,
O. Inganas, and F. L. Zhang, J. Phys. Chem. C 114, 3701 (2010).
ꢀ
in Figure 7. There are two endothermic peaks at 148 C
ꢀ
ꢀ
and 180 C and one exothermic peak at 158 C observed
for 3TPA, while no any endothermic or exothermic peak
for P3TPA. The results in some way prove our speculation
about the polymerization of 3TPA.
18. K. Yamamoto, M. Higuchi, K. Uchida, and Y. Kojima, Macro-
molecules 35, 5782 (2002).
19. J. Zhang, D. Deng, C. He, Y. J. He, M. J. Zhang, Z. G. Zhang, Z. J.
Zhang, and Y. F. Li, Chem. Mater. 23, 817 (2011).
2
2
2
0. S. Roquet, A. Cravino, P. Leriche, O. Alévêque, P. Frère, and
4
. CONCLUSION
J. Roncali, J. Am. Chem. Soc. 128, 3459 (2006).
1. A. Cravino, S. Roquet, P. Leriche, O. Alévêque, P. Frère, and
J. Roncali, Chem. Commun. 13, 1416 (2006).
2. H. Kageyama, H. Ohishi, M. Tanaka, Y. Ohmori, and Y. Shirota.
IEEE J. Se. Top. Quantum Electron. 16, 1528 (2010).
Two star-shaped oligothiophene derivatives with pheny-
lamine core, 3TPA and 3TPA-3CN, have been synthesized
and investigated in term of their electronic and optical
properties. Introduction of electron-drawing cyano group
to the ꢁ-position of thiophene unit makes the maximum
absorption of 3TPA-3CN red-shift in comparison with
that of 3TPA, but leads the oxidation potentials shift
to a little positive value. Both oligothiophene derivatives
reveals valuable electrochromic characteristics. 3TPA-3CN
23. B. B. Yin, C. Y. Jiang, Y. G. Wang, M. La, P. Liu, and W. J. Deng,
Synth. Met. 160, 432 (2010).
24. L. Guan, J. Wang, M. La, Y. P. Zhong, P. Liu, and W. J. Deng,
Mater. Sci. Forum 663, 369 (2011).
2
5. X. B. Sun, Y. Q. Liu, S. Y. Chen, W. F. Qiu, G. Yu, Y. Q. Ma, T. Qi,
H. J. Zhang, X. J. Xu, and D. B. Zhu, Adv. Funct. Mater. 16, 917
(2006).
Received: 23 September 2013. Accepted: 20 January 2014.
3034
J. Nanosci. Nanotechnol. 15, 3029–3034, 2015