The synthesis and photoluminescence characteristics of novel 4-aryl substituted thiophene derivatives with bis-diarylacrylonitrile unit

Article abstract of DOI:10.1016/j.dyepig.2012.05.019

(Z)-2-(4-Bromophenyl)-3-(4-(5-((Z)-2-cyano-2-phenylvinyl)thiophen-3-yl) -phenyl)acrylonitrile was synthesized by (Z)-3-(4-(4-formylphenyl)-thiophen-2- yl)-2-phenylacrylonitrile and 2-(4-bromophenyl)acetonitrile through a base catalyzed condensation reaction, and then reacted with various aryl boronic acids under the catalyzing of Pd(PPh₃)₄ to afford a series of novel 4-aryl substituted thiophene derivatives with bis-diarylacrylonitrile unit. The structures of the products were characterized using FTIR, ¹H NMR, ¹³C NMR, and HRMS. The UV-vis absorption and photoluminescent spectra of these derivatives were investigated. These compounds emit 450-510 nm green fluorescence in the solid state and 446-491 nm emission in CH₂Cl₂ solution under UV irradiation. Analysis revealed good thermal stability with a decomposition temperature ranging from 301 to 378°C.

Full text of DOI:10.1016/j.dyepig.2012.05.019

Dyes and Pigments 95 (2012) 358e364
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
The synthesis and photoluminescence characteristics of novel 4-aryl substituted
thiophene derivatives with bis-diarylacrylonitrile unit
,
Zhaozhe Xu a, Dian Yu b, Mingxin Yu a
*
a Department of Chemistry, Zhejiang University, Hangzhou 310027, China
b Department of Information Science and Electronic Engineering, Zhejiang University, Hangzhou 310027, China
a r t i c l e i n f o
a b s t r a c t
Article history:
(Z)-2-(4-Bromophenyl)-3-(4-(5-((Z)-2-cyano-2-phenylvinyl)thiophen-3-yl)-phenyl)acrylonitrile
was
Received 20 April 2012
Received in revised form
16 May 2012
Accepted 20 May 2012
Available online 1 June 2012
synthesized by (Z)-3-(4-(4-formylphenyl)-thiophen-2-yl)-2-phenylacrylonitrile and 2-(4-bromophenyl)
acetonitrile through a base catalyzed condensation reaction, and then reacted with various aryl boronic
acids under the catalyzing of Pd(PPh3)4 to afford a series of novel 4-aryl substituted thiophene deriva-
tives with bis-diarylacrylonitrile unit. The structures of the products were characterized using FTIR, 1H
NMR, 13C NMR, and HRMS. The UVevis absorption and photoluminescent spectra of these derivatives
were investigated. These compounds emit 450e510 nm green fluorescence in the solid state and 446
e491 nm emission in CH2Cl2 solution under UV irradiation. Analysis revealed good thermal stability
with a decomposition temperature ranging from 301 to 378 ꢀC.
Keywords:
Thiophene derivatives
Aryl boronic acid
Ó 2012 Elsevier Ltd. All rights reserved.
a,b-Acrylonitriles
Synthesis
Pd-catalyzed
Photoluminescence characteristics
1. Introduction
organic light-emitting device materials [24e27], wewere interested
in the preparation of a series of novel functionalistic aryl substituted
As one of the most promising fields in the past few decades,
Organic light-emitting diodes (OLEDs) attracted considerable
researches to develop different materials and various devices [1e4].
Due to their excellent properties such as light weight, self emitting,
wide view angle and flexibility [5e7], OLEDs have significant appli-
cations in replacing cathode ray tubes (CRTs) or liquid crystal displays
(LCDs) [8,9]. Among all these OLED materials, thiophene-based
materials have shown to be one of the most prospective functional
ones[10e12], because of theirintrinsic electron-rich nature, excellent
environmental and thermal stabilities, special optical and electrical
properties, and the easy manipulation of their properties by intro-
ducing functional substituents at different positions [11,13].
thiophene derivatives for potential applications in dyes, pigments
and as hole-transporting emitters in organic light-emitting devices
[24,28e30]. In this paper, we report the synthesis and photophysical
properties of novel fluorescent aryl substituted thiophene deriva-
tives with bis-diarylacrylonitrile unit. The structures of these
compounds were characterized by FTIR, 1H NMR, 13C NMR, and
HRMS. The UVevis absorption (UVevis) and photoluminescent
spectrum (PL) were investigated. And the general properties such as
solubility and thermal properties were reported.
2. Experimental
Thiophene derivatives were also widely used in dyes and
pigments [14e16] due to their interesting optical properties [12,15]
2.1. Materials
and electron-donating functions [15]. a,b-acrylonitriles derivatives
Palladium, aryl boronic acids, Na2CO3, dimethoxyethane were
purchased from Aldrich Chemical Co. Sodium tert-butoxide was
purchased from Alfa-Aesar and stored in a vacuum atmospheres
glove box under nitrogen. All chemicals were used as supplied.
have important uses as organic light-emitting materials [17,18].
They are also versatile intermediates in the synthesis of various
compounds, such as perfumes, Vitamin A, pigments [19,20] and
organic dyes [21e23].
Based on the outstanding properties of thiophene and a,b-dia-
rylacrylonitriles derivatives, as well as our previous studies on
2.2. Instruments and measurements
All melting points were determined with a WRS-1A melting
point apparatus and were uncorrected. Thermogravimetric analysis
(TGA) was performed on Mettler Toledo TGA/SDTA 851e. Nuclear
* Corresponding author. Tel.: þ86 571 87979519; fax: þ86 571 87951895.
E-mail address: mingxinyu@zju.edu.cn (M. Yu).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2012.05.019

Z. Xu et al. / Dyes and Pigments 95 (2012) 358e364
359
magnetic resonance (1H NMR and 13C NMR) spectra were run on
a Bruker AV-400 NMR or a Bruker DMX-500 NMR spectrometer in
CDCl3. IR spectra were recorded in KBr on a Nicolet NEXUS 470 FTIR
spectrophotometer. UVevis spectra were taken using a Hitachi U-
3300 model, while a Hitachi F-4500 fluorescence spectrophotom-
eter was used to take the PL spectra. All the mass spectroscopy data
of the products were collected using a gas chromatography-high
resolution time of flight mass spectrometer made by Waters
Corporation of US (GCT Premier).
108.73, 56.06, 56.04. HRMS (EI): Calcd for C30H22N2O2S: 474.1402.
Found: 474.1409.
2.3.3.2. (Z)-3-(4-(4-((Z)-2-cyano-2-(naphthalen-1-yl)vinyl)phenyl)
thio-phen-2-yl)-2-phenylacrylonitrile (3b). Yellow solid. Yield: 84%.
M.p. 208e210 ꢀC. FTIR (KBr pellet, cmꢁ1): 3104, 3057, 3012, 2920,
2209, 1569, 1444, 1186, 909, 775.1H NMR (400 MHz, CDCl3) dH: 8.20
(d, J ¼ 8.8 Hz, 1H), 8.04e8.00 (m, 3H), 7.93 (d, J ¼ 8.0 Hz, 2H), 7.75
(d, J ¼ 8.8 Hz, 3H), 7.68 (d, J ¼ 7.6 Hz, 3H), 7.62e7.51 (m, 4H),
7.48e7.36 (m, 4H). 13C NMR (400 MHz, CDCl3): dc: 146.99, 141.79,
138.90, 136.80, 133.85, 133.75, 133.68, 133.49, 132.93, 130.75,
130.58, 129.98, 129.90, 129.22, 129.18, 128.77, 127.34, 127.10, 126.80,
126.52, 125.78, 125.68, 125.40, 124.53, 118.68, 118.00, 109.79, 109.18.
HRMS (EI): Calcd for C32H20N2S: 464.1347. Found: 464.1349.
2.3. Synthesis
2.3.1. Synthesis of compound (1)
A
solution of 4-bromothiophene-2-carbaldehyde (0.191 g,
1.00 mmol), benzyl cyanide (0.128 g, 1.10 mmol) and sodium
methoxide (0.54 mg, 0.01 mmol) in 10 mL EtOH was stirred for 4 h
at room temperature in a 100 mL round bottom flask, and then
filtered. The precipitate was washed with cold EtOH.
2.3.3.3. (Z)-2-(4-bromophenyl)-3-(4-(5-((Z)-2-cyano-2-phenylvinyl)
thio-phen-3-yl)-phenyl)acrylonitrile (3c). Yellow solid. Yield: 85%.
M.p. 182e183 ꢀC. FTIR (KBr pellet, cmꢁ1): 3102, 3068, 3051, 2926,
2212, 1592, 1180, 1070, 826, 757. 1H NMR (400 MHz, CDCl3) dH: 7.97
(d, J ¼ 4.8 Hz, 2H), 7.94 (s, 1H), 7.74 (s, 1H), 7.72e7.66 (m, 5H),
7.60e7.52 (m, 5H), 7.48e7.40 (m, 3H). 13C NMR (400 MHz, CDCl3):
dc: 141.69, 141.63, 138.90, 136.76, 133.62, 133.36, 132.72, 132.27,
130.38, 130.09, 129.23, 129.18, 127.44, 127.19, 126.75, 125.76, 125.67,
123.50, 117.99, 117.70, 110.36, 109.20. HRMS (EI): Calcd for
C28H17BrN2S: 492.0296. Found: 492.0289.
2.3.2. Synthesis of compound (2a)
To a 50 ml sidearm flask was added compound 1 (0.291 g,
1.00 mmol), (4-formylphenyl) boronic acid (0.157 g, 1.10 mmol),
Pd(PPh3)4 (0.012 g, 0.01 mmol) and sodium carbonate (0.233 g,
2.20 mmol), EtOH (3.0 mL), dimethoxyethane (7.5 mL),H2O (2.0 mL)
was injected into the flask from a syringe. The reaction mixture was
heated and stirred at 85 ꢀC under nitrogen for 8 h until the reaction
was completed. The reaction mixture was then cooled to room
temperature, filtered through a mixture of celite and silica gel pad
and washed with dichloromethane. The filtrate was washed with
water and then dried by MgSO4. Concentration of the filtrate on
a rotary evaporator followed by washing of the solid material with
ethanol afforded the desired crude product. The crude product was
purified by column chromatography on silica gel using dichloro-
methane/petroleum ether(1/1) as eluents.
2.3.3.4. (Z)-3-(4-(4-((Z)-2-cyano-2-phenylvinyl)phenyl)thiophen-2-
yl)-2-phenylacrylonitrile (3d). Yellow solid. Yield: 87%. M.p.
174e175 ꢀC. FTIR (KBr pellet, cmꢁ1): 3102, 3054, 3030, 2926, 2212,
1589, 1450, 1180, 897, 832, 770. 1H NMR (400 MHz, CDCl3) dH: 7.94
(d, J ¼ 8.4 Hz, 3H), 7.71e7.65 (m, 8H), 7.52 (s, 1H), 7.47e7.36 (m, 6H).
13C NMR (400 MHz, CDCl3): dc: 141.60, 141.18,138.73,136.32,134.26,
133.60, 133.51, 132.89, 130.44, 129.92, 129.17, 129.08, 129.02, 126.55,
125.86, 125.64, 125.52, 118.02, 117.92, 111.31, 108.90. HRMS (EI):
Calcd for C28H18N2S: 414.1191. Found: 414.1194.
2.3.2.1. (Z)-3-(4-(4-formylphenyl)thiophen-2-yl)-2-phenylacrylonitrile
(2a). Pale yellow solid. Yield: 90%. M.p. 186 ꢀC. FTIR (KBr pellet,
cmꢁ1): 3093, 2822, 2718, 2209, 1696, 1605, 1212, 1162, 822, 763. 1H
NMR (400 MHz, CDCl3) dH: 10.03 (s, 1H), 7.99(s, 1H), 7.94 (d,
J ¼ 8.0 Hz, 2H), 7.77e7.75 (m, 3H), 7.67e7.65 (m, 3H), 7.47e7.40 (m,
3H). 13C NMR (400 MHz, CDCl3):dc: 191.58, 141.50, 140.32, 139.06,
135.46, 133.56, 133.50, 130.51, 130.41, 129.30, 129.19, 126.82, 126.39,
125.77, 117.94, 109.46. HRMS (EI): Calcd for C20H13NOS: 315.0718.
Found: 315.0720.
2.3.3.5. (Z)-2-(4-chlorophenyl)-3-(4-(5-((Z)-2-cyano-2-phenylvinyl)
thio-phen-3-yl)phenyl)acrylonitrile (3e). Yellow solid. Yield: 83%.
M.p.175 ꢀC. FTIR (KBr pellet, cmꢁ1): 3102, 3051, 3027, 2206, 1596,
1486, 1403, 1090, 832, 757. 1H NMR (400 MHz, CDCl3) dH: 7.97 (d,
J ¼ 5.2 Hz, 2H), 7.94 (s,1H), 7.75e7.58 (m, 8H), 7.51 (s,1H), 7.46e7.41
(m, 5H). 13C NMR (400 MHz, CDCl3): dc: 141.78, 141.62, 138.93,
136.81, 135.35,133.69,133.65, 132.96,132.78,130.38,130.09, 129.33,
129.19, 127.23, 126.99, 126.79, 125.80, 125.66, 117.98, 117.75, 110.41,
109.29. HRMS (EI): Calcd for C28H17ClN2S: 448.0801. Found:
448.0799.
2.3.3. General procedure for the synthesis of compounds (3ae3g)
A solution of compound 2a (0.299 g, 1 mmol), aromatic aceto-
nitrile halides (1.10 mmol) and sodium methoxide (0.54 mg,
0.01 mmol) in 10 mL EtOH was stirred for 4e8 h at 60 ꢀC in a 25 mL
round bottom flask, and then filtered. The precipitate was washed
with water till PH ¼ 7, and then purified by column chromatog-
raphy on silica gel using ether aceter/dichloromethane/petroleum
ether (1/0.2/2) as eluents.
2.3.3.6. (Z)-3-(4-(4-((Z)-2-cyano-2-(p-tolyl)vinyl)phenyl)thiophen-
2-yl)-2-phenylacrylonitrile (3f). Yellow solid. Yield: 90%. M.p.
156 ꢀC. FTIR (KBr pellet, cmꢁ1): 3084, 3054, 3024, 2920, 2209, 1587,
1186, 894, 831, 757. 1H NMR (400 MHz, CDCl3) dH: 7.97 (d, J ¼ 4.4 Hz,
2H), 7.94 (s, 1H), 7.74 (s, 1H), 7.71e7.67 (m, 5H), 7.59 (d, J ¼ 8.0 Hz,
2H), 7.51 (s, 1H), 7.48e7.40 (m, 3H), 7.26 (d, J ¼ 5.2 Hz, 2H), 2.41 (s,
3H). 13C NMR (400 MHz, CDCl3): dc: 141.71, 140.18, 139.47, 138.77,
133.69, 133.58, 133.10, 131.49, 130.55, 129.88, 129.82, 129.76, 129.14,
126.59, 125.79, 125.70, 125.57, 125.51, 118.18, 117.98, 111.34, 108.91,
21.23. HRMS (EI): Calcd for C29H20N2S: 428.1347. Found: 428.1343.
2.3.3.1. (Z)-3-(4-(4-((E)-2-cyano-2-(3,4-dimethoxyphenyl)vinyl)phenyl)
thiophen-2-yl)-2-phenylacrylonitrile (3a). Yellow solid. Yield: 88%.
M.p. 196e198 ꢀC. FTIR (KBr pellet, cmꢁ1): 3084, 3057, 3030, 2964,
2925, 2834, 2209, 1605, 1514, 1254, 1144, 1022, 825, 766. 1H NMR
(400 MHz, CDCl3) dH: 7.97 (s, 1H), 7.93 (d, J ¼ 8.0 Hz, 2H),
7.72e7.66 (m, 6H), 7.47e7.37 (m, 4H), 7.29e7.26 (m, 1H), 7.16 (s,
1H), 6.92 (d, J ¼ 8.4 Hz, 1H), 3.97 (s, 3H), 3.93 (s, 3H). 13C NMR
(400 MHz, CDCl3): dc: 150.15, 149.31, 141.81, 139.42, 138.80, 136.12,
133.70, 133.63, 133.19, 130.49, 129.80, 129.66, 129.15, 127.21,
126.63, 125.74, 125.48, 119.07, 118.23, 118.01, 111.30, 111.24, 109.02,
2.3.3.7. (Z)-3-(4-(4-((Z)-2-cyano-2-(4-methoxyphenyl)vinyl)phenyl)
thio-phen-2-yl)-2-phenylacrylonitrile (3g). Yellow solid. Yield: 84%.
M.p. 160 ꢀC. FTIR (KBr pellet, cmꢁ1): 3104, 3030, 2968, 2931, 2834,
2209, 1605, 1512, 1294, 1181, 1031, 829, 760.1H NMR (400 MHz,
CDCl3) dH: 7.94 (s, 1H), 7.90 (d, J ¼ 8.0 Hz, 2H), 7.70e7.60 (m, 8H),
7.46e7.38 (m, 4H), 6.95 (d, J ¼ 8.8 Hz, 2H), 3.84 (s, 3H). 13C NMR
(400 MHz, CDCl3): dc: 160.48, 141.82, 139.14, 138.78, 136.04, 133.74,

360
Z. Xu et al. / Dyes and Pigments 95 (2012) 358e364
133.64, 133.27, 130.57, 129.76, 129.15, 127.30, 126.86, 126.62, 125.74,
125.46, 118.23, 118.00, 114.54, 114.45, 111.07, 108.98, 55.44. HRMS
(EI): Calcd for C29H20N2OS: 444.1296. Found: 444.1299.
CDCl3): dc: 159.62, 141.85, 141.70, 140.61, 138.85, 136.47, 133.75,
133.69, 133.15, 132.64, 132.38, 130.54, 130.02, 129.20, 129.17, 128.10,
127.17, 126.74, 126.37, 125.78, 125.58, 118.08, 118.00, 114.39, 111.25,
109.15, 55.40. HRMS (EI): Calcd for C35H24N2S: 504.1660. Found:
504.1558.
2.3.4. General procedure for the synthesis of compounds (4ae4h)
To a 50 ml sidearm flask was added compound 3c (0.246 g,
0.50 mmol), aryl boronic acids (0.55 mmol), Pd(PPh3)4 (0.160 g,
0.05 mmol) and sodium carbonate (0.12 g, 1.10 mmol), EtOH
(5.0 mL), dimethoxyethane (15 mL), H2O (5.0 mL) was injected into
the flask from a syringe. The reaction mixture was heated and
stirred at 85 ꢀC under nitrogen for an appropriate time until the
reaction was completed. The reaction mixture was then cooled to
room temperature, filtered through a mixture of celite and silica gel
pad and washed with dichloromethane. The filtrate was washed
with water and then dried by MgSO4. Concentration of the filtrate
on a rotary evaporator followed by washing of the solid material
with ethanol afforded the desired crude product. The crude product
was purified by column chromatography on silica gel using
dichloromethane/petroleum ether (3/2) as eluents.
2.3.4.5. (Z)-2-(40-chloro-[1,10-biphenyl]-4-yl)-3-(4-(5-((Z)-2-cyano-2-
phenylvinyl)-thiophen-3-yl)-phenyl)acrylonitrile (4e). Bright yellow
solid. Yield: 86%. M.p.197 ꢀC. FTIR (KBr pellet, cmꢁ1): 3087, 3060,
3030, 2923, 2849, 2206, 1587, 1483, 1182, 1090, 998, 814, 757. 1H
NMR (500 MHz, CDCl3) dH: 7.99 (d, J ¼ 7.0 HZ, 3H), 7.78e7.75 (m,
3H), 7.73 (d, J ¼ 8.5 Hz, 2H), 7.68e7.66 (m, 4H), 7.64 (s, 1H), 7.60 (s,
1H), 7.56 (d, J ¼ 8.5 Hz, 2H), 7.48e7.43 (m, 4H), 7.42e7.39 (m, 1H).
13C NMR (500 MHz, CDCl3): dc: 141.80,141.14,140.79,138.89,138.35,
136.64,134.03,133.69,133.67,133.63,132.99,130.44,130.08,129.22,
129.17, 129.12, 128.26, 127.53, 126.77, 126.48, 125.78, 125.62, 117.97,
110.99, 109.22. HRMS (EI): Calcd for C34H21ClN2S: 524.1114. Found:
524.1114.
2.3.4.6. (Z)-3-(4-(4-((Z)-2-cyano-2-(40-methoxy-[1,10-biphenyl]-4-yl)
vinyl) phenyl)-thiophen-2-yl)-2-phenylacrylonitrile (4f). Bright
yellow solid. Yield: 87%. M.p.197e198 ꢀC. FTIR (KBr pellet, cmꢁ1):
3102, 3035, 2968, 2929, 2834, 2210, 1605, 1588, 1497, 1253, 1179,
897, 822, 756. 1H NMR (400 MHz, CDCl3) dH: 7.99e7.98 (m, 3H),
7.76e7.43 (m, 4H), 7.71 (s, 1H), 7.68e7.64 (m, 5H), 7.59e7.56 (m,
3H), 7.48e7.40 (m, 3H), 7.01 (d, J ¼ 8.5 Hz, 2H), 3.87 (s, 3H). 13C NMR
(500 MHz, CDCl3): dc: 159.62, 141.85, 141.70, 140.61, 138.85, 136.47,
133.75, 133.69, 133.15, 132.64, 132.38, 130.54, 130.02, 129.20, 129.17,
128.10, 127.17, 126.74, 126.37, 126.37, 125.78, 125.58, 118.08, 118.00,
114.39, 111.25, 109.15, 55.40. HRMS (EI): Calcd for C35H24N2OS:
520.1609. Found: 520.1609.
2.3.4.1. 3-(4-(4-((Z)-2-cyano-2-(4-(naphthalen-1-yl)phenyl)vinyl)
phenyl) thiophen-2-yl)-2-phenylacrylonitrile (4a). Bright yellow
solid. Yield: 87%. M.p. 203 ꢀC. FTIR (KBr pellet, cmꢁ1):3057, 3030,
2968, 2926, 2209, 1584, 1186, 802, 757. 1H NMR (500 MHz, CDCl3)
dH: 8.01e7.98 (m, 2H), 7.94e7.88 (m, 3H), 7.82 (d, J ¼ 8.0 Hz, 2H),
7.74e7.66 (m, 5H), 7.64 (s, 1H), 7.59 (d, J ¼ 8.0 Hz, 2H), 7.56e7.38 (m,
9H). 13C NMR (500 MHz, CDCl3): dc: 141.88, 141.77, 141.20, 139.03,
138.85, 136.55, 133.81, 133.72, 133.64, 133.34, 133.05, 131.33, 130.77,
130.52, 130.05, 129.18, 129.15, 128.41, 128.12, 126.95, 126.74, 126.30,
125.94, 125.90, 125.75, 125.64, 125.62, 125.38, 118.11, 117.99, 111.19,
109.10. HRMS (EI): Calcd for C38H24N2S: 540.1660. Found: 540.1661.
2.3.4.2. (Z)-3-(4-(4-((Z)-2-cyano-2-(4-(naphthalen-2-yl)phenyl)vinyl)
phenyl)thiophen-2-yl)-2-phenylacrylonitrile (4b). Bright yellow
solid. Yield: 82%. M.p. 224e225 ꢀC. FTIR (KBr pellet, cmꢁ1): 3090,
3051, 3033, 2923, 2212, 1652, 1584, 1498, 1450, 1182, 900, 813. 1H
NMR (500 MHz, CDCl3) dH: 8.10 (s, 1H), 8.01 (d, J ¼ 9.0 Hz, 2H),
7.96e7.88 (m, 4H), 7.83 (s, 3H), 7.82e7.73 (m, 4H), 7.69 (d, J ¼ 7.5 Hz,
2.3.4.7. (Z)-3-(4-(4-((Z)-2-cyano-2-(40-vinyl-[1,10-biphenyl]-4-yl)
vinyl)
phenyl)thiophen-2-yl)-2-phenylacrylonitrile
(4g). Bright
yellow solid. Yield: 81%. M.p.194e196 ꢀC. FTIR (KBr pellet, cmꢁ1):
3084, 3030, 2923, 2209, 1587, 1495, 1186, 998, 900, 829, 757. 1H
NMR (500 MHz, CDCl3) dH: 8.00 (s, 1H), 7.99 (d, J ¼ 3.0 Hz, 2H),
7.79e7.76 (m, 3H), 7.73 (d, J ¼ 8.5 Hz, 2H), 7.71e7.68 (m, 5H),
7.62e7.60 (m, 3H), 7.52 (d, J ¼ 8.0 Hz, 2H), 7.48e7.45 (m, 2H),
7.42e7.39 (m, 1H), 6.78 (dd, J ¼ 11.0 Hz, J ¼ 10.5 Hz, 1H), 5.83 (d,
J ¼ 18.0 Hz, 1H), 5.31(d, J ¼ 11.0 Hz, 1H). 13C NMR (500 MHz, CDCl3):
dc: 141.83, 141.55, 140.93, 139.19, 138.87, 137.19, 136.55, 136.23,
133.74, 133.68, 133.32, 133.08, 130.52, 130.06, 129.21, 129.17, 127.47,
127.11, 126.79, 126.75, 126.40, 125.77, 125.62, 118.03, 117.99, 114.34,
111.14, 109.16. HRMS (EI): Calcd for C36H24N2S: 516.1660. Found:
516.1663.
2H), 7.64 (s, 1H), 7.54e7.41 (m, 7H). 13C NMR (500 MHz, CDCl3): dc
:
141.88, 141.02, 138.91, 137.25, 133.79, 133.66, 133.41, 133.14, 132.90,
129.47, 129.25, 130.56, 130.10, 129.21, 128.71, 128.31, 128.02, 127.98,
127.72, 126.80, 126.59, 126.55, 126.51, 126.32, 125.95, 125.81, 125.77,
125.65, 125.18, 125.15, 111.12, 109.22. HRMS (EI): Calcd for
C38H24N2S: 540.1660. Found: 540.1663.
2.3.4.3. (Z)-2-([1,10-biphenyl]-4-yl)-3-(4-(5-((Z)-2-cyano-2-phenyl
vinyl) thiophen-3-yl)phenyl)acrylonitrile (4c). Bright yellow solid.
Yield: 87%. M.p.173 ꢀC. FTIR (KBr pellet, cmꢁ1): 3051, 3029, 2216,
1589, 1486, 1450, 1413, 1181, 897, 836, 764. 1H NMR (400 MHz,
CDCl3) dH: 7.98 (d, J ¼ 6.8 Hz, 3H), 7.77 (d, J ¼ 8.0 Hz, 2H), 7.73(d,
J ¼ 8.0 Hz, 2H), 7.70e7.67 (m, 6H), 7.63 (d, J ¼ 7.6 Hz, 2H), 7.58 (s,
1H), 7.49e7.43 (m, 4H), 7.40e7.37 (m, 2H). 13C NMR (400 MHz,
CDCl3): dc: 141.99, 141.72, 140.84, 139.87, 138.87, 136.42, 133.70,
133.64, 133.22, 133.03, 130.55, 130.09, 129.20, 129.00, 127.92, 127.67,
127.04, 126.68, 126.38, 126.16, 125.78, 125.65, 118.16, 118.08,
110.99,109.05. HRMS (EI): Calcd for C34H22N2S: 490.1504. Found:
490.1503.
2.3.4.8. (Z)-3-(4-(4-((Z)-2-cyano-2-(30,50-dimethyl-[1,10-biphenyl]-
4-yl) vinyl)phenyl)thiophen-2-yl)-2-phenylacrylonitrile (4h). Bright
yellow solid. Yield: 89%. M.p. 185 ꢀC. FTIR (KBr pellet, cmꢁ1): 3026,
2915, 2212, 1604, 1588, 1182, 897, 832, 760, 694. 1H NMR (400 MHz,
CDCl3) dH: 7.94 (d, J ¼ 8.4 Hz, 3H), 7.72e7.62 (m, 10H), 7.53 (s, 1H),
7.45e7.38 (m, 3H), 7.22 (s, 2H), 7.02 (s, 1H), 2.39 (s, 6H). 13C NMR
(400 MHz, CDCl3): dc: 142.30, 141.77, 140.72, 139.88, 138.84, 138.48,
136.42, 133.70,133.65,133.08, 133.02, 130.52, 129.66,129.54, 129.16,
127.67, 126.68, 126.49, 126.24, 125.76, 125.58, 124.92, 118.08, 118.00,
111.15, 109.08, 21.42. HRMS (EI): Calcd for C36H26N2S: 518.1817.
Found: 518.1820.
2.3.4.4. (Z)-3-(4-(4-((Z)-2-cyano-2-(40-methyl-[1,10-biphenyl]-4-yl)
vinyl)
phenyl)thiophen-2-yl)-2-phenylacrylonitrile
(4d). Bright
3. Results and discussion
yellow solid. Yield: 89%. M.p. 220 ꢀC. FTIR (KBr pellet, cmꢁ1): 3102,
3035, 2968, 2929, 2834, 2210,1605,1588,1497, 1253, 1179, 897, 822,
756. 1H NMR (400 MHz, CDCl3) dH: 7.99e7.98 (m, 3H), 7.76e7.73 (m,
4H), 7.71 (s, 1H), 7.68e7.64 (m, 5H), 7.59e7.56 (m, 3H), 7.48e7.40
(m, 3H), 7.01 (d, J ¼ 8.5 Hz, 2H), 3.87 (s, 3H). 13C NMR (400 MHz,
3.1. Synthesis
The target compounds (3ae3g, 4ae4h) were synthesized
through a four-step procedure. The specific synthesis procedure

Z. Xu et al. / Dyes and Pigments 95 (2012) 358e364
361
was shown in Scheme 1. Compound 1 was prepared through a base
catalyzed condensation reaction of 4-bromothiophene-2-
carbaldehyde and benzyl cyanide, and then reacted with (4-
formylphenyl)-boronic under the catalysis of Pd(PPh3)4 to get
compound 2a. Compound (3ae3g) was then prepared using base
catalyzed reaction of compound 2a and various benzyl cyanide. We
then used compound 3c, via palladium-catalyzed cross-coupling
reaction, to prepare a series of novel fluorescent aryl-substituted
thiophene derivatives (4ae4h) with longer conjugated chain.
In this paper, the Suzuki coupling reaction was used twice to
prepare the target compounds with longer conjugated chain. The
Suzuki cross-coupling reaction has received much attention due to
its versatility in the CeC bond formation and construction of biaryl
skeleton [31e34]. In this paper, we used Pd(PPh3)4 as catalyst to
prepare compounds (4ae4g), Na2CO3 was used as the base and the
solvent system was a mixture of Ethylene glycol dimethyl ether,
EtOH and H2O. The ligand-free catalyst was particularly efficient in
this system, which helped to achieve satisfying yields between 81
and 90%. The specific yields are shown in Table 1.
The thermal properties of 3ae3g and 4ae4h were investigated by
TGA. The decomposition temperature curves show thermal stability
up to 301e378 ꢀC (Table 1), which indicates these compounds may
have applications as materials. Compounds 4ae4h have a significant
thermal stability increase compared to 3ae3g, which indicates the
incorporationofanarylgroup enhances thethermalproperties. Some
representative data have been shown in Fig. 1.
Scheme 1. Synthesis of compounds 3ae3g and 4ae4h.

362
Z. Xu et al. / Dyes and Pigments 95 (2012) 358e364
Table 1
Table 2
Yields and thermal properties of compounds (3ae3g) and (4ae4h).
Photophysical properties of compounds (3ae3g).
a
b
Entry
Yield [%]
Tm [ꢀC]
TD [ꢀC]
Entry
CH2Cl2 labs [nm]
CH2Cl2 lem [nm]
Solid lem [nm]
3a
3b
3c
3d
3e
3f
3g
4a
4b
4c
4d
4e
4f
88
84
85
87
83
90
84
87
82
87
89
86
87
81
89
196
208
182
174
175
156
160
203
224
324
353
322
302
321
313
350
354
351
378
345
328
370
378
361
3a
3b
3c
3d
3e
3f
369
357
344
357
361
360
362
457
445
435
418
425
426
437
489
496
480
468
463
492
476
3g
Table 3
173
220
197
Photophysical properties of compounds (4ae4h).
Entry
CH2Cl2
labs [nm]
CH2Cl2
lem [nm]
THF
labs [nm]
THF
lem [nm]
Solid
lem [nm]
197e198
194
4g
4h
4a
4b
4c
4d
4e
4f
364
361
366
368
366
369
366
370
449
491
446
451
447
462
453
446
355
349
353
350
351
353
351
363
443
448
442
442
444
451
443
444
489
489
483
495
475
484
508
484
185
a
Melting points of compounds 3ae3g and 4ae4h.
Decomposition temperature of compounds 3ae3g and 4ae4h.
b
3.2. Photophysical properties
4g
4h
In order to investigate their photophysical properties, the UV
and PL spectra of compounds (3ae3g, 4ae4h) in CH2Cl2, THF and
solid state were recorded. The spectrum data are summarized in
Tables 2 and 3, respectively.
The UVevis absorption spectra shows similar absorption
behavior between compounds (3ae3g, 4ae4h). The absorption
spectra of 3ae3g, 4ae4h in CH2Cl2 solution are shown in Fig. 2.
Each of them reveals a common low-energy broad band at
300e400 nm assigned to the pep* transitions of the compounds. A
change of solvent from CH2Cl2 to THF resulted in a little blue shift
(7e18 nm) of the absorption maximum (Table 2). Some represen-
tative spectra are shown in Fig. 3.
Photoluminescent spectra of the compounds (3ae3g, 4ae4g)
were also recorded in CH2Cl2 solution. For the emission spectra in
CH2Cl2 solution, the PL spectra of compounds 3ae3g and 4ae4h are
summarized in Tables 2 and 3. The maximal emission peaks of
3ae3g and 4ae4h are mainly located at about 416e457 nm and
446e491 nm respectively. All compounds yield blue or green
emissions in CH2Cl2 solution at room temperature. The Photo-
luminescent spectra of the compounds 4ae4h in THF solution were
recorded and summarized in Table 3 as well. A change of the
Fig. 2. Absorption spectra of compounds 3ae3g, 4ae4h in CH2Cl2 solution.
Fig. 1. The TGA spectrum of compounds (3a, 3d, 3f, 4c, 4d, 4f).
Fig. 3. Absorption spectra of compounds 4a and 4h in different solutions.

Z. Xu et al. / Dyes and Pigments 95 (2012) 358e364
363
Fig. 6. PL spectra of compounds (3d, 3f, 4c, 4d) in CH2Cl2 solution.
Fig. 4. PL spectra of compounds 4a and 4h in different solutions.
solvent from CH2Cl2 to THF resulted in a 2e43 nm red shift of the
emission maximum, which indicates that the polarity of the solvent
plays an important role on the photophysical properties in such
strong donoreacceptor systems. Some representative spectra are
shown in Fig. 4.
Emission spectra of compounds 3ae3g and 4ae4h in the solid
state were determined with an excitation wavelength of 360 nm,
the results are shown in Tables 2 and 3 and Fig. 5. All of the
compounds exhibit green emission with a maximum peak at
450e510 nm. The emission peaks of series 4 (4ae4h) in the solid
state show a red shift compared to compound 3d which is attrib-
uted to the introduction of a phenyl group.
In order to study the effects on photophysical properties after
the introduction of a phenyl group, comparisons between series 3
and series 4 were made. Fig. 6 exhibit the emission spectra of
compounds 3d, 3f, 4c, 4d in CH2Cl2. The only difference between
3de4c, and 3fe4d is the introduction of a biphenyl group which
extend the conjugated pathway. It can be found that PL spectra of
4c, 4d in CH2Cl2 solution and in the solid state are all red shifted
relative to those of 3d, 3f. Similar results can also be found between
Fig. 7. PL spectra of compounds (2a, 2b, 4c, 4d) in CH2Cl2 solution.
3ee4e, and 3ge4f. The red shifts in these compounds result from
the extension of the conjugated length.
Meanwhile, we also studied the effects of the introduction of an
aryl-acrylonitrile group. We compared the absorption bands and
emission spectra of compounds 4c, 4d with (Z)-2-phenyl-3-(4-ph-
enylthiophen-2-yl)acrylonitrile
methoxyphenyl) thiophen-2-yl)-2-phenylacrylonitrile
(2b)
and
(Z)-3-(4-(4-
(2d)
respectively, as shown in Fig. 7. The only difference between these
compounds is the introduction of a biphenyl-acrylonitrile group.
That the UVevis bands and PL spectra of 4c, 4d in CH2Cl2. solution
and in the solid state are all red shifted significantly. With the
introduction of a phenyl-acrylonitrile group, the extended conju-
gated chain attributes to the red shift in these compounds.
4. Conclusions
In conclusion, several novel 4-aryl substituted thiophene
derivatives with bis-diarylacrylonitrile unit have been efficiently
synthesized. The absorption and photoluminescent spectra of these
derivatives in CH2Cl2 and THF were investigated. These compounds
exhibit similar absorption and emission behaviors and emit
strongly in solution and solid state, with the emission maximal in
the range of 400e500 nm.
Fig. 5. PL spectra of compounds (3aeg, 4aeh) in solid state.

364
Z. Xu et al. / Dyes and Pigments 95 (2012) 358e364
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The project is sponsored by the Natural Science Foundation for
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