The synthesis and photoluminescence characteristics of novel α,β-diarylacrylonitrile derivatives containing both a biphenyl group and a triphenylamine unit

Article abstract of DOI:10.1016/j.dyepig.2010.07.010

2-(4-Bromophenyl)-3-(4-diphenylaminophenyl)acrylonitrile was prepared by the base catalysed condensation of 4-diphenylaminobenzaldehyde and 2-(4-bromophenyl)acetonitrile. A series of α,β-diarylacrylonitrile derivatives containing both a biphenyl group and a triphenylamine unit were synthesized from 2-(4-bromophenyl)-3-(4-diphenylaminophenyl)acrylonitrile and boronic acids via a Suzuki reaction. The structures of these compounds were characterized using FTIR, ¹H NMR, ¹³C NMR, MS and elemental analysis. The UV-vis absorption and photoluminescent spectra of these derivatives were investigated. These compounds emit green fluorescence with maximum emission peaks of 500-550 nm in CH₂Cl₂ solution and in the solid state under UV irradiation. Analysis revealed good thermal stability with a decomposition temperature ranging from 279-386 °C.

Full text of DOI:10.1016/j.dyepig.2010.07.010

Dyes and Pigments 88 (2011) 301e306
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
The synthesis and photoluminescence characteristics of novel a,b-
diarylacrylonitrile derivatives containing both a biphenyl group and
a triphenylamine unit
*
Bao Li, Qian Li, Bin Liu, Youfeng Yue, Mingxin Yu
Department of Chemistry, 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:
2-(4-Bromophenyl)-3-(4-diphenylaminophenyl)acrylonitrile was prepared by the base catalysed
condensation of 4-diphenylaminobenzaldehyde and 2-(4-bromophenyl)acetonitrile. A series of a,b-dia-
Received 19 April 2010
Received in revised form
27 July 2010
Accepted 27 July 2010
Available online 5 August 2010
rylacrylonitrile derivatives containing both a biphenyl group and a triphenylamine unit were synthesized
from 2-(4-bromophenyl)-3-(4-diphenylaminophenyl)acrylonitrile and boronic acids via a Suzuki reac-
tion. The structures of these compounds were characterized using FTIR, 1H NMR, 13C NMR, MS and
elemental analysis. The UVevis absorption and photoluminescent spectra of these derivatives were
investigated. These compounds emit green fluorescence with maximum emission peaks of 500e550 nm
in CH2Cl2 solution and in the solid state under UV irradiation. Analysis revealed good thermal stability
with a decomposition temperature ranging from 279e386 ꢀC.
Keywords:
Triphenylamine
Diarylacrylonitrile
Suzuki reaction
Photoluminescence
Biphenyl
Ó 2010 Elsevier Ltd. All rights reserved.
OLEDs
1. Introduction
triphenylamine derivatives. In the present article, we report the
design and synthesis of a series of novel
a,b-diarylacrylonitrile
Considerable studies have been made on organic light emitting
diodes (OLEDs) for their potential applications in next generation
full-colour displays as a promising alternative to the conventional
liquid crystal displays [1e4]. Among the various kinds of OLED
materials, triarylamine derivatives have been widely investigated
for almost two decades because these compounds have showed
excellent thermal and electrochemical stability, electron-donating
ability, optoelectronic properties [5e9] and they are standard hole
transport materials [10e14].
derivatives containing both a biphenyl group and a triphenylamine
unit and which offer potential application as dyes, pigments and
OLED materials [20e24]. The structure of the compounds was
characterized using FTIR, 1H NMR, 13C NMR, MS and elemental
analysis. The general properties such as solubility and thermal
properties are reported. Their ultravioletevisible spectrum
(UVevis) and photoluminescence (PL) properties were recorded.
2. Experimental
Triphenylamine derivatives have been widely used as dyes [7,14]
and a,b-diarylacrylonitriles attract interest since nitriles serve as
2.1. Materials
versatile intermediates in the synthesis of variety of products such
as perfumes, sex-pheromones, vitamin A, and pigments [15,16].
Furthermore, aromatic compounds based on biphenyls also play an
important role in their applications in OLEDs as well as in dyes and
Palladium, boronic acids, Na2CO3, dimethoxyethane were
purchased from Aldrich Chemical Co. Sodium tert-butoxide was
purchased from Alfa-Aesar. Toluene was distilled under nitrogen
from molten sodium. All chemicals were used as supplied.
pigments because of their easy synthesis and highly polarizable
electron systems [17,18].
p-
Based on our studies in the field of organic light emitting devices
[5,19], as well as in palladium-catalysed coupling reactions [6,10,11],
we became interested in the preparation of new functionalized
2.2. Instruments and measurements
All melting points were determined with a WRS-1A melting
point apparatus and were uncorrected. 1H and 13C NMR spectra
were run on a Bruker AV-400 NMR spectrometer in CDCl3. IR
* Corresponding author. Tel.: þ86 571 87979519; fax: þ86 571 87951895.
E-mail address: mingxinyu@css.zju.edu.cn (M. Yu).
0143-7208/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2010.07.010

302
B. Li et al. / Dyes and Pigments 88 (2011) 301e306
spectra were recorded in KBr on a Nicolet NEXUS 470 FTIR spec-
trophotometer. Vibrational transition frequencies were reported in
wave numbers (cmꢁ1). Mass spectra were obtained on HP5989B
mass spectrometer. Elemental analyses were determined using
a PerkineElmer 240 analyzer. UVevis spectra were recorded on
a Hitachi U-3300 model while PL spectra were taken using a Hitachi
F-4500 fluorescence spectrophotometer. Thermo gravimetric
analysis (TGA) was performed on Waters DSC Q100.
(s, 1H), 7.32 (m, 4H), 7.10e7.17 (m, 6H), 7.03 (d, J ¼ 8.8 Hz, 2H). 13
C
NMR (400 MHz, CDCl3): dc: 150.3, 146.5, 142.0, 134.1, 132.1, 130.7,
129.6, 127.1, 126.0, 125.8, 124.5, 122.6, 120.7, 118.4, 106.4. MS m/z:
465 (Mþ). Anal. Calcd for C28H22BrN2: C, 72.11; H, 4.75; N, 6.01.
Found: C, 72.02; H, 4.83; N, 6.12.
2.3.2. General procedure for the synthesis of a,b-diarylacrylonitrile
derivatives containing both biphenyl group and triphenylamine
(4aee)
2.3. Synthesis
A degassed mixture of 2-(4-bromophenyl)-3-(4-diphenylami-
nophenyl) acrylonitrile (1.0 mmol), Na2CO3 (2.2 mmol), water
(1.1 mL), EtOH (0.8 mL), dimethoxyethane (2.5 mL), boronic acids
(1.2 mmol), and Pd(PPh3)4 (0.01 mmol) was heated under reflux for
an appropriate length of time. The reaction mixture was allowed to
cool to room temperature, and the inorganic material was filtered
off. The filtrate was concentrated under reduced pressure, and the
resulting crude oil was chromatographed on silica gel to afford the
target compounds 4aee (eluent: ethyl acetate and hexane).
2.3.1. General procedure for the synthesis of triphenylamines
containing a,b-diarylacrylonitriles (3aee)
A solution of the aromatic aldehyde (1.0 mmol) and aromatic
acetonitrile (1.0 mmol) in absolute EtOH (10 mL) was treated
portion wise with NaOMe (0.1 mmol), stirred at room temperature
for 1e2 h, cooled to 0 ꢀC, and filtered. The precipitate was washed
with cool EtOH.
2.3.1.1. (Z)-2-(4-chlorophenyl)-3-(4-diphenylaminophenyl)acryloni-
trile (3a). Yellow solid. Yield: 82%. M.p. 147e148 ꢀC. FTIR (KBr
pellet, cmꢁ1): 3063, 3034, 2214, 1608, 1585, 1514, 1491, 1329, 1298,
2.3.2.1. (Z)-2-biphenyl-4-yl-3-(4-diphenylaminophenyl)acrylonitrile
(4a). Yellow solid. Yield: 92%. M.p. 185 ꢀC. FTIR (KBr pellet, cmꢁ1):
3029, 2210, 1582, 1506, 1488, 1450, 1428, 1333, 1298, 1273, 1194,
1179, 846, 834, 763, 757, 704, 696. 1H NMR (400, CDCl3) dH: 7.80 (d,
J ¼ 8.4 Hz, 2H), 7.73 (d, J ¼ 8.4 Hz, 2H), 7.67e7.62(m, 4H), 7.47 (d,
J ¼ 4.0 Hz), 7.45(s, 1H), 7.40e7.31(m, 5H), 7.18e7.11(m, 6H),
7.07e7.05(d, J ¼ 8.4 Hz, 2H). 13C NMR (400 MHz, CDCl3) dc: 150.0(C),
146.6(CH), 141.3(C), 141.3(C), 140.1(C), 133.9(C), 130.7(CH), 129.6
(CH), 128.9(CH), 127.7(C), 127.6(CH), 127.0(CH), 126.4(C), 126.1(CH),
125.7(CH), 124.4(CH), 120.1(CH), 118.8(C), 107, 2(C). MS m/z: 448
(Mþ). Anal. Calcd for C33H24N2: C, 88.36; H, 5.39; N, 6.25. Found: C,
88.33; H, 5.37; N, 6.30.
1251, 1185, 1178, 829, 757, 706, 696. 1H NMR (400 MHz, CDCl3) dH
:
7.75 (d, J ¼ 8.4 Hz, 2H), 7.56 (d, J ¼ 2.0 Hz, 1H), 7.54 (d, J ¼ 2.0 Hz,
1H), 7.35e7.38 (m, 3H), 7.28e7.32 (m, 4H), 7.09e7.15 (m, 6H), 7.02
(d, J ¼ 9.2 Hz, 2H). 13C NMR (400 MHz, CDCl3): dc: 155.5, 148.2,
136.4, 135.0, 134.3, 133.0, 129.8, 129.5, 129.2, 129.0, 128.4, 127.5,
127.4, 126.3, 119.3. MS m/z: 406 (Mþ). Anal. Calcd for C27H19ClN2: C,
79.70; H, 7.71; N, 6.88. Found: C, 79.66; H, 7.73; N, 6.85.
2.3.1.2. (Z)-3-(4-diphenylaminophenyl)-2-phenylacrylonitrile
(3b)
[25]. Yellow solid. Yield: 89%. M.p. 145e146 ꢀC. FTIR (KBr pellet,
cmꢁ1): 3058, 3033, 2216, 1584, 1507, 1489, 1329, 1297, 1274, 1178,
759, 696. 1H NMR (400 MHz, CDCl3) dH: 7.80 (d, J ¼ 8.8 Hz, 2H), 7.66
(d, J ¼ 8.0 Hz, 2H), 7.43e7.46 (m, 3H), 7.32e7.39 (m, 5H), 7.12e7.19
2.3.2.2. (Z)-3-(4-diphenylaminophenyl)-2-(40-methylbiphenyl-4-yl)
acrylonitrile (4b). Yellow solid. Yield: 94%. M.p. 192e194 ꢀC. FTIR
(KBr pellet, cmꢁ1): 3033, 2923, 2211, 1583, 1507, 1489, 1332, 1297,
1270, 1194, 1180, 1074, 1008, 810, 759, 700, 532. 1H NMR (400,
CDCl3) dH: 7.79(d, J ¼ 8.0 Hz, 2H), 7.70(d, J ¼ 8.0 Hz, 2H), 7.63(d,
J ¼ 8.4 Hz, 2H), 7.52 (d, J ¼ 8.0 Hz, 2H), 7.46(s,1H), 7.33e7.25(m, 6H),
7.17e7.10(m, 6H), 7.06(d, J ¼ 8.4 Hz, 2H), 2.40(s, 3H). 13C NMR
(400 MHz, CDCl3) dc: 149.9(C), 146.6(CH), 141.3(C), 141.2(C), 137.6
(C), 133.6(C), 130.7(CH), 129.6(CH), 129.6(CH), 127.4(CH), 126.8(CH),
126.5(C), 126.0(CH), 125.7(CH), 124.3(CH), 120.9(CH), 118.8(C), 107.3
(C), 21.1(CH3). MS m/z: 462 (Mþ). Anal. Calcd for C34H26N2: C, 88.28;
H, 5.67; N, 6.06. Found: C, 88.23; H, 5.73; N, 6.04.
(m, 6H), 7.07 (d, J ¼ 8.8 Hz, 2H). 13C NMR (400 MHz, CDCl3): dc
:
148.0, 146.4, 141.8, 137.9, 130.7, 129.9, 129.7, 127.8, 127.6, 125.8,
122.9, 122.6, 122.4, 118.8, 108.5.
2.3.1.3. (Z)-3-(4-diphenylaminophenyl)-2-p-tolylacrylonitrile
(3c). Yellow solid. Yield: 85%. M.p. 120e121 ꢀC. FTIR (KBr pellet,
cmꢁ1): 3052, 3035, 2214, 1585, 1512, 1504, 1488, 1328, 1296, 1192,
1178, 828, 815, 757, 695. 1H NMR (400 MHz, CDCl3) dH: 7.79 (d,
J ¼ 8.8 Hz, 2H), 7.56 (d, J ¼ 8.8 Hz, 2H), 7.41 (s, 1H), 7.32e7.36 (m,
4H), 7.24e7.27 (m, 2H), 7.13e7.20 (m, 6H), 7.07 (d, J ¼ 7.2 Hz, 2H),
2.40 (s, 3H). 13C NMR (400 MHz, CDCl3): dc: 149.7, 146.7, 140.7, 138.7,
132.2, 130.5, 129.7, 129.5, 126.7, 125.6, 125.5, 124.3, 121.0, 118.8,
107.8, 21.2. MS m/z: 386 (Mþ). Anal. Calcd for C28H22N2: C, 87.01; H,
5.74; N, 7.52. Found: C, 86.89; H, 5.83; N, 7.63.
2.3.2.3. (Z)-3-(4-diphenylaminophenyl)-2-(40-methoxybiphenyl-4-
yl)acrylonitrile (4c). Yellow solid. Yield: 96%. M.p. 171e173 ꢀC. FTIR
(KBr pellet, cmꢁ1): 3034, 2957, 2835, 2212, 1583, 1506, 1493, 1333,
1286, 1273, 1194, 1180, 1040, 1027, 818, 732, 700, 531. 1H NMR (400,
CDCl3) dH: 7.78(d, J ¼ 8.4 Hz, 2H), 7.68(d, J ¼ 8.4 Hz, 2H), 7.60(d,
J ¼ 8.0 Hz, 2H), 7.55(d, J ¼ 8.4 Hz, 2H), 7.45(s,1H), 7.31(dd, J ¼ 8.0 Hz,
J ¼ 7.6 Hz, 4H), 7.17-7.10(m, 6H), 7.05(d, J ¼ 8.8 Hz, 2H), 6.99(d,
J ¼ 8.4 Hz, 2H), 3.85(s, 3H). 13C NMR (400 MHz, CDCl3) dc: 159.5(C),
149.9(C), 146.6(CH), 141.0(C), 140.9(C), 133.3(C), 132.5(C), 130.6(CH),
129.6(CH), 128.0(CH), 127.1(CH), 126.5(C), 126.0(CH), 125.7(CH),
124.4(CH), 120.9(CH), 118.8(C), 114.3(CH), 107.3(C), 55.4(CH3). MS
m/z: 478 (Mþ). Anal. Calcd for C34H26N2O: C, 85.33; H, 5.48; N, 5.85.
Found: C, 85.38; H, 5.54; N, 5.74.
2.3.1.4. (Z)-3-(4-diphenylaminophenyl)-2-(4-methoxyphenyl)acrylo-
nitrile (3d) [26]. Yellow solid. Yield: 90%. M.p.118e120 ꢀC. FTIR (KBr
pellet, cmꢁ1): 3052, 3031, 2214, 1608, 1585, 1514, 1491, 1298, 1251,
1185, 1178, 1035, 829, 757, 696. 1H NMR (400 MHz, CDCl3) dH: 7.80
(d, J ¼ 8.4 Hz, 2H), 7.63 (d, J ¼ 8.8 Hz, 2H), 7.35e7.39 (m, 5H),
7.15e7.22 (m, 6H), 7.11 (d, J ¼ 8.4 Hz, 2H), 7.00 (d, J ¼ 8.4 Hz, 2H),
3.90 (s, 3H). 13C NMR (400 MHz, CDCl3): dc: 160.0, 149.6, 146.8,
139.8, 130.4, 129.6, 127.6, 127.0, 126.9, 125.6, 124.2, 121.2, 118.8,
114.4, 107.6, 55.4.
2.3.2.4. (Z)-2-(30,50-dimethylbiphenyl-4-yl)-3-(4-diphenylamino-
phenyl)acrylonitrile (4d). Yellow solid. Yield: 75%. M.p. 75 ꢀC. FTIR
(KBr pellet, cmꢁ1): 3027, 2913, 2348, 2204, 1584, 1506, 1492, 1380,
1332, 1285, 1193, 1179, 836, 755, 697. 1H NMR (400, CDCl3) dH: 7.83(d,
J ¼ 8.4 Hz, 2H), 7.73(d, J ¼ 8.4 Hz, 2H), 7.48(s, 1H), 7.35(dd, J ¼ 6.8 Hz,
J ¼ 8.0 Hz, 4H), 7.27 (s, 2H), 7.21e7.16(m, 6H), 7.10(d, J ¼ 7.6 Hz, 2H),
2.3.1.5. (Z)-2-(4-bromophenyl)-3-(4-diphenylaminophenyl)acryloni-
trile (3e). Yellow solid. Yield: 85%. M.p. 143e144 ꢀC. FTIR (KBr
pellet, cmꢁ1): 3063, 3034, 2212, 1638, 1578, 1535, 1508, 1492, 1333,
1193, 1179, 1075, 751, 698. 1HNMR (400 MHz, CDCl3) dH: 7.76 (d,
J ¼ 8.8 Hz, 2H), 7.54 (d, J ¼ 8.8 Hz, 2H), 7.49 (d, J ¼ 8.8 Hz, 2H), 7.39

B. Li et al. / Dyes and Pigments 88 (2011) 301e306
303
7.06(s, 1H), 2.43(s, 6H). 13C NMR (400 MHz, CDCl3) dc: 149.9(C), 146.7
was synthesized according to
a
literature procedure [12].
(CH), 141.6(C), 141.2(C), 140.1(C), 138.5(CH), 133.7(C), 130.7(CH), 129.7
(CH), 129.4(C), 127.6(CH), 126.5(C), 126.0(CH), 125.8(CH), 125.0(CH),
124.4(CH), 120.9(CH), 118.9(C), 107.4(C), 21.5(CH3). MS m/z: 476 (Mþ).
Anal. Calcd for C35H28N2: C, 88.20; H, 5.92; N, 5.88. Found: C, 88.15; H,
5.91; N, 5.94.
a,bediarylacrylonitrile derivatives 3aee were prepared by the base
catalysed condensation between compound 2 and an aromatic
acetonitrile. In the last step of the sequence compound 3e was
coupled with various boronic acids to afford a series of a,b-diary-
lacrylonitrile derivatives containing both a biphenyl group and
a triphenylamine unit by the Suzuki reaction.
2.3.2.5. (Z)-3-(4-diphenylaminophenyl)-2-(4-(naphthalen-2-yl)
phenyl)acrylonitrile (4e). Yellow solid. Yield: 78%. M.p. 199e200 ꢀC.
FTIR (KBr pellet, cmꢁ1): 3057, 2352, 2209, 15814, 1507, 1490, 1334,
1274, 1193, 1179, 815, 756, 700. 1H NMR (400, CDCl3) dH: 8.09(s, 1H),
7.95(d, J ¼ 8.8 Hz, 1H), 7.93(d, J ¼ 7.6 Hz, 1H), 7.89(d, J ¼ 8.0 Hz, 1H),
7.84e7.77(m, 7H), 7.52(d, J ¼ 6.8 Hz, 3H), 7.34(dd, J ¼ 8.0 Hz,
J ¼ 7.6 Hz, 4H), 7.20e7.13(m, 6H), 7.08(d, J ¼ 8.8 Hz, 2H). 13C NMR
(400 MHz, CDCl3) dc: 150.0(C), 146.6(CH), 141.4(C), 141.2(C), 137.4
(C), 134.0(C), 133.6(C), 132.8(C), 130.7(CH), 129.6(CH), 128.6(CH),
128.2(CH), 127.8(CH), 127.7(CH), 126.5(C), 126.4(CH), 126.2(CH),
126.1(CH), 125.8(CH), 125.7(CH), 125.2(CH), 124.4(CH), 120.9(CH),
118.8(C), 107.2(C). MS m/z: 498 (Mþ). Anal. Calcd for C37H26N2: C,
89.13; H, 5.26; N, 5.62. Found: C, 89.03; H, 5.41; N, 5.56.
Palladium-catalysed cross coupling reaction is widely used in the
construction of aryl CeC bond [29e32]. Suzuki coupling of aryl
halides and aryl boronic acids is a powerful method for the synthesis
of biaryl compounds [33e36]. In this work, we used the catalytic
system of Pd(PPh3)4 to prepare compounds (4aee), Na2CO3 was
used as the base and the solvent system employed was a mixture of
DME, EtOH and H2O. The ligand-free catalyst was particularly effi-
cient in this system and the yields were consistently in the 78e96%
range. The reaction times and yields are shown in Table 1.
The thermal properties of 3aee and 4aee were investigated by
TGA. Decomposition temperature curves are shown in Fig. 1. The
TGA data (Table 1) show thermal stability up to 279e386 ꢀC. Series
4 have higher decomposition temperature than series 3, the results
indicate that the incorporation of a biphenyl group into series 3
enhances the thermal properties significantly.
3. Results and discussion
3.1. Synthesis
3.2. Photophysical properties
The target compounds 4aee were prepared via a four-step
procedure which is shown in Scheme 1.
Compound 1 was prepared from diphenylamine and 1-bromo-
benzene according to well-known chemistry [27,28]. Compound 2
Most light emitting electrofluorescent molecules were designed
based on the electron-donating and electron-withdrawing groups on
a conjugated system. Here a nitrile function is employed as an electron
Br
R
O
CN
N
NH
N
H
ii
i
iii
1
2
N
R
N
NC
R
R
3a-d
3a:R= Cl, 3b:R= H,
3c:R=CH3, 3d:R= OCH3
NC
4a, 4b, 4c
(HO)2B
4a: R=H, 4b: R=CH3, 4c: R=OCH3
CH3
CH3
(HO)2B
N
CH3
Br
N
NC
iv
NC
3e
CH3
4d
B(OH)2
i
v
N
NC
4e
Conditions: (i) Pd(OAc)2, P(o-tolyl)3, NaO-t-Bu, Toluene, 110°C; (ii) DMF, POCl3 ;
(iii) NaOCH3, Ethanol, rt, (iv) Pd(PPh3)4, Na2CO3, DME, Ethanol:
H2O(1:1.25).
Scheme 1. Synthesis of a,b-diarylacrylonitrile derivatives (3aee) and (4aee).

304
B. Li et al. / Dyes and Pigments 88 (2011) 301e306
Table 1
Reaction times, yields and thermal properties of compounds (3aee) and (4aee).
3a
3b
3c
3d
3e
4a
4b
4c
4d
4e
1.0
0.8
0.6
0.4
0.2
0.0
a
b
Entry
Reaction time [h]
Yield [%]
Tm [ꢀC]
Td [ꢀC]
3a
3b
3c
3d
3e
4a
4b
4c
4d
4e
1.5
1
1
2
2
4
4
4
8
82
85
89
85
90
92
94
96
85
78
148
145
121
118
144
185
193
172
75
279
285
284
288
283
356
333
386
311
341
10
199
a
Melting points of compounds 3aee and 4aee.
Decomposition temperature of compounds 3aee and 4aee.
b
300
350
400
450
500
3a
3b
3c
3d
3e
4a
4b
4c
4d
4e
Wavelength (nm)
100
80
60
40
20
0
Fig. 2. Absorption spectra of compounds (3aee) and (4aee) in CH2Cl2 solution.
3a
1.0
3b
3c
0.8
3d
3e
0.6
4a
4b
0.4
0
100
200
300
400
500
4c
Temperature (OC)
4d
0.2
4e
Fig. 1. TGA spectra of compounds (3aee) and (4aee).
0.0
withdrawing group and the triphenylamine group is the election
donor function. In order to investigate the photophysical properties of
these groups, the UVevis absorption and PL spectra of compounds
(3aee, 4aee) in different solutions were recorded. The spectral data
are summarized in Table 2, and the UVevis and PL spectra of these
compounds in CH2Cl2 solution are shown in Figs. 2 and 3.
-0.2
450
500
550
600
650
700
Wavelength (nm)
Fig. 3. PL spectra of compounds (3aee) and (4aee) in CH2Cl2 solution.
In the UVevis absorption spectra between 280 and 450 nm, two
bands were clearly observed for these derivatives and the behavior
are quite similar to each other. They reveal a common low-energy
toluene were also recorded in Table 2. These absorption bands are
relatively insensitive to the solvents compared with the corre-
sponding emission bands. Variations of less than 7 nm were
observed in different polar solvents.
For the emission spectra in CH2Cl2 solution, as shown in Fig. 3,
all of the compounds display similar behavior and yield green
broad band at 350e450 nm assigned to the
compounds. The absorption bands at 280e350 nm come from the
combination of the ne * transition of triphenylamine moieties.
pep* transitions of the
p
The absorption bands of each compound in cyclohexane and
Table 2
Photophysical properties of compounds (3aee) and (4aee).
Entry
CH2Cl2
labs [nm]
CH2Cl2
lem [nm]
Toluene
labs [nm]
Toluene
lem [nm]
Cyclohexane
labs [nm]
Cyclohexane
lem [nm]
Solid
lem [nm]
3a
Ffb
[mol Lꢁ1 cmꢁ1
]
[%]
3a
3b
3c
3d
3e
4a
4b
4c
4d
4e
305, 409
306, 403
307, 402
308, 402
304, 409
308, 416
308, 411
308, 414
308, 413
310, 412
535
524
513
512
529
522
524
520
526
525
306, 408
307, 402
308, 401
309, 402
306, 409
309, 419
309, 417
308, 410
308, 412
310, 409
483
471
473
470
479
487
486
485
484
487
305, 405
306, 397
307, 397
308, 397
305, 406
307, 412
307, 410
307, 407
307, 406
308, 406
466
445
448
446
461
457
457
457
457
463
512
504
505
503
523
511
525
545
530
547
14172, 25208
14568, 28128
16126, 30146
19108, 34944
22407, 39159
22837, 31561
23402, 29924
26858, 32982
18469, 23634
27258, 30981
8.2
9.8
7.6
14.2
8.5
27.2
12.6
18.7
11.2
12.4
a
Extinction coefficients determined in CH2Cl2 solutions when the concentration of each compound is 1.0 ꢂ 10ꢁ5 M.
Relative quantum yields (with fluorescein in THF Ff ¼ 0.93 as a standard).
b

B. Li et al. / Dyes and Pigments 88 (2011) 301e306
305
emission at room temperature. The maximal emission peaks are
3c in CH2Cl2
1.0
0.8
0.6
0.4
0.2
0.0
mainly located at about 510e540 nm. The emission spectra of these
compounds in cyclohexane and toluene were also recorded in Table
2. It can be seen that the emission spectra of compounds 3aee and
4aee show significant difference in different solvents, the average
maximal emission peak is about 520 nm in CH2Cl2 solution, while
in cyclohexane and toluene solution, they are 460 nm and 480 nm
respectively. A change of the solvent from cyclohexane to toluene
resulted in about 20 nm red shift of the emission maximum,
similarly, when the solvent changed from toluene to CH2Cl2, about
a 40 nm red shift of the emission maximum of these compounds
occurred. The polarity of the solvent plays an important role on the
photophysical properties in such strong donoreacceptor systems.
Emission spectra of compounds 3aee and 4aee in the solid state
were determined with an excitationwavelength of 400 nm, the results
are showninTable 2 andFig. 4. Thesecompounds haverelativelysmall
stokes shifts in the range 100e150 nm. The emission peaks of
compounds 4aee in the solid state show a small red shift compared to
3b which is attributed to the introduction of biphenyl groups.
Extinction coefficients of UVevis absorption maximum were
calculated and recorded in Table 2, compounds 3aee and 4aee have
extinction coefficients range of 1.4 ꢂ 104e2.7 ꢂ 104 mol Lꢁ1 cmꢁ1 at
300 nm and 2.3 ꢂ 104e3.9 ꢂ 104 mol Lꢁ1 cmꢁ1 at 400 nm in CH2Cl2
solution. The fluorescence quantum efficiencies of compounds 3aee
and 4aee were determined in tetrahydrofuran (Table 2). Their Ff is
between 7.6 and 27.2%.
3c in Cyclohexane
3c in Toluene
4b in CH2Cl2
4b in Cyclohexane
4b in Toluene
450
500
550
600
650
700
Wavelength (nm)
Fig. 6. PL spectra of compounds 3c and 4b in different solutions.
The introduction of a biphenyl group into series 3 resulted in the
change of their photophysical properties (Table 2). In order to study
the effects on photophysical properties after introducing the
biphenyl group, comparisons between series 3 and series 4 were
made. Figs. 5 and 6 exibit the absorption bands and emission
spectra of compounds 3c and 4b in different solvents. Compounds
3c and 4b have the same R group (eCH3), the only difference is that
4b has a biphenyl group thus it has a longer conjugation pathway. It
can be found that the UVevis bands and PL spectra of 4b in
different solvents and in the solid state are all red shifted relative to
those of 3c. Furthermore, quantum yields are also improved when
the conjugation of the system increased. Similar results can also be
found between 3b and 4a, and 3d and 4c when the R groups are H,
and OMe, respectively.
3a
1.0
3b
3c
0.8
3d
3e
0.6
4a
4b
0.4
0.2
0.0
4c
4d
4e
4. Conclusions
In conclusion, several novel
a,b-diarylacrylonitrile derivatives
containing both a biphenyl group and a triphenylamine unit have
been efficiently synthesised. The absorption and photoluminescent
spectra of these derivatives in different solutions were investigated.
These compounds exhibit similar absorption and emission
behavior and emit strongly in solution and in the solid state, with
the emission maxima in the range of 500e550 nm. The compounds
exhibit good thermal stability with a decomposition temperature
range from 279e386 ꢀC.
450
500
550
600
650
700
Wavelength (nm)
Fig. 4. PL spectra of compounds (3aee) and (4aee) in the solid state.
3c in CH2Cl2
Acknowledgements
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
3c in Cyclohexane
3c in Toluene
4b in CH2Cl2
The project is sponsored by the Natural Science Foundation for
the Education Ministry of Zhejiang Province.
4b in Cyclohexane
4b in Toluene
References
[1] Tang CW, Slyke Van. Organic electroluminescent diodes. Applied Physics
Letters 1987;51:913e5.
[2] Lin HQ, Chen BJ, Zhang XH, Lee CS, Kwong HL, Lee ST. A novel yellow fluo-
rescent dopant for high-performance organic electroluminescent devices.
Chemistry of Materials 2001;13:456e8.
[3] Namai H, Ikeda H, Hoshi Y, Kato N, Morishita Y, Mizuno K. Thermolumines-
cence and a new organic light-emitting diode (OLED) based on triplet-triplet
fluorescence of the trimethylenemethane (TMM) biradical. Journal of the
American Chemical Society 2007;129:9032e6.
[4] Froehlich JD, Young R, Nakamura T, Ohmori Y, Li S, Mochizuki A. Synthesis of
multi-functional POSS emitters for OLED applications. Chemistry of Materials
2007;19:4991e7.
300
350
400
450
500
Wavelength (nm)
Fig. 5. Absorption spectra of compounds 3c and 4b in different solutions.

306
B. Li et al. / Dyes and Pigments 88 (2011) 301e306
[5] Yu MX, Chang LC, Lin CH, Duan JP, Wu FI, Chen IC, et al. Luminescence
[21] Li ZH, Wong MS, Tao Y, D’Iorio M. Synthesis and functional properties of
strongly luminescent diphenylamino end-capped oligophenylenes. The Jour-
nal of Organic Chemistry 2004;69:921e7.
[22] Vezzu DAK, Deaton JC, Shayeghi M, Li YM, Huo SQ. Acridinone/amine(carba-
zole)-based bipolar molecules: efficient hosts for fluorescent and phospho-
rescent emitters. Organic Letters 2009;11:4310e3.
properties of aminobenzanthrones and their application as host emitters in
organic light-emitting devices. Advanced Functional Materials 2007;17:
369e78.
[6] Yue YF, Kang JH, Yu MX. The synthesis and photophysical properties of novel tri-
phenylamine derivatives containing a, b-diarylacrylonitrile. Dyes and Pigments
2009;83:72e80.
[23] Ge ZY, Hayakawa T, Ando S, Ueda M, Akiike T, Miyamoto H, et al. Spin-coated
highly efficient phosphorescent organic light-emitting diodes based on
bipolar triphenylamine-benzimidazole derivatives. Advanced Functional
Materials 2008;18:584e90.
[7] Ning ZJ, Zhang Q, Wu WJ, Pei HC, Liu B, Tian H. Starburst triarylamine based
dyes for efficient dye-sensitized solar cells. The Journal of Organic Chemistry
2008;73(10):3791e7.
[8] Hua JL, Li B, Meng FS, Ding F, Qian SX, Tian H. Two-photon absorption prop-
erties of hyperbranched conjugated polymers with triphenylamine as the
core. Polymer 2004;45(21):7143e9.
[24] Ko CW, Tao YT. Organic light-emitting diodes based on 2-(stilben-4-yl) ben-
zoxazole derivatives: an implication on the emission mechanism. Chemistry
of Materials 2001;13:2441e6.
[9] Meng FS, Mi J, Qian SX, Chen KC, Tian H. Linear and tri-branched copolymers
for two-photon absorption and two-photon fluorescent materials. Polymer
2003;44:6851e5.
[10] Yu MX, Chen XH, Cheng CH. Study on synthesis of organic light emitting diode
materials of aminoanthrancenes and their light emitting property. Chinese
Journal of Organic Chemistry 2005;25:218e21.
[11] Yu MX, Wang MJ, Chen XH, Hong BB, Zhang XY, Cheng CH. Synthesis of OLED
materials of several triarylamines by palladium catalysts and their light
emitting property. Journal of Chemical Research 2005;9:558e60.
[12] Sengupta S, Sadhukhan SK, Muhuri S. A tetraphenylmethane based starburst
triarylamine cluster:spectroscopy, electrochemistry and morphological
studies. Tetrahedron Letters 2002;43:3521e4.
[13] Zhao HD, Tanjutco C, Thayumanavan S. Design and synthesis of stable triaryl-
amines for hole-transport applications. Tetrahedron Letters 2001;42:4421e4.
[14] Tian HN, Yang XC, Chen RK, Zhang R, Hagfeldt A, Sun LC. Effect of different dye
baths and dye-structures on the performance of dye-sensitized solar cells
based on triphenylamine dyes. The Journal of Physical Chemistry C 2008;112
(29):11023e33.
[25] Hisahiro H, Kazumasa W, Akira K. Electrophotographic photoreceptors. JP
61259256(A), 1986e11e17.
[26] Masabumi O, Teruyuki O, Fumio K, Hirota S, Toshihiko T. Electroluminescent
devices. JP 03205477(A), 1991e9e6.
[27] Wolfe JP, Tomori H, Sadighi JP, Yin J, Buchwald SL. Simple, efficient catalyst
system for the palladium-catalyzed amination of aryl chlorides, bromides, and
triflates. The Journal of Organic Chemistry 2000;65:1158e74.
[28] Goodson FE, Hauck SI, Hartwig JF. Palladium-catalyzed synthesis of pure,
regiodefined polymeric triarylamines. Journal of the American Chemical
Society 1999;121(33):7527e39.
[29] Hassan J, Svignon M, Gozzi C, Schulz E, Lemaire M. Arylꢁaryl bond formation
one century after the discovery of the Ullmann reaction. Chemical Review
2002;102:1359e469.
[30] Han J, Liu Y, Guo R. Facile synthesis of highly stable gold nanoparticles and
their unexpected excellent catalytic activity for Suzuki-Miyaura cross-
coupling reaction in water. Journal of the American Chemical Society
2009;131:2060e1.
[31] Cho JK, Najman R, Dean TW, Ichihara O, Muller C, Bradley M. Captured and
cross-linked palladium nanoparticles. Journal of the American Chemical
Society 2006;128:6276e7.
[32] Navarro O, Kelly III RA, Nolan SP. A general method for the Suzuki-Miyaura
cross-coupling of sterically hindered aryl chlorides: synthesis of di-and tri-
ortho-substituted biaryls in 2-propanol at room temperature. Journal of the
American Chemical Society 2003;125:16194e5.
[15] Fringuelli F, Pani G, Piermatti O, Pizzo F. Condensation reactions in water of
active methylene compounds with arylaldehydes: one-pot synthesis of
flavonols. Tetrahedron 1994;50:11499e508.
[16] D’Sa BA, Kisanga P, Verkade JG. Direct synthesis of alpha, beta- unsaturated
nitriles catalyzed by nonionic superbases. The Journal of Organic Chemistry
1998;63:3961e7.
[17] LyeJ, FreemanHS,CoxRD. MolecularmodelingofCongoRedanaloguescontaining
terphenyl and quarterphenyl moieties. Dyes and Pigments 2000;47:53e64.
[18] Dinçer HA, Gonca E, Gul A. The synthesis and spectral properties of novel
[33] Suzuki A. Recent advances in the cross-coupling reactions of organoboron
derivatives with organic electrophiles, 1995e1998. Journal of Organometallic
Chemistry 1999;576:147e68.
}
phthalocyanines with pendant bulky units. Dyes and Pigments
2008;79:166e9.
[19] Yu MX, Duan JP, Lin CH, Cheng CH, Tao YT. Diaminoanthracene derivatives as
high-performance green host electroluminescent materials. Chemistry of
Materials 2002;14:3958e63.
[20] Zhou Y, He QG, Yang Y, Zhong HZ, He C, Sang GY, et al. Binaphthyl-containing
green- and red-emitting molecules for solution-processable organic light-
emitting diodes. Advanced Functional Materials 2008;18:3299e306.
[34] Brath H, Mesková M, Putala M. Suzuki cross-coupling at the chiral groove of
1,10-binaphthyl:Stereoconservation versus deracemization pathway. Euro-
pean Journal of Organic Chemistry; 2009:3315e8.
[35] Yin JJ, Buchwald SL. A catalytic asymmetric Suzuki coupling for the synthesis
of axially chiral biaryl compounds. Journal of the American Chemical Society
2000;122:12051e2.
[36] Yu MX, Fang HY, Yue YF, Chen YC, Chen SW. Synthesis of a novel ligand
containing phenyl pyridine. Synthetic Communications 2010;40:58e63.