Synthesis of oligo(p-phenylene-vinylene-thienylene)s as potential red light-emitting materials

Article abstract of DOI:10.1016/S0040-4020(03)00783-X

Several potential red light-emitting oligomers containing alkoxylated phenylene-vinylene-thienylene backbones with and without cyano groups at the olefin moieties have been designed and synthesized. The influences of the skeleton as well as the position of the cyano groups in the vinylene moiety to the absorption and emission spectra of these new oligomers are also discussed.

Full text of DOI:10.1016/S0040-4020(03)00783-X

Tetrahedron 59 (2003) 5193–5198
Synthesis of oligo(p-phenylene–vinylene–thienylene)s as potential
red light-emitting materials
Cuihua Xuea,b and Fen-Tair Luoa
,
*
aInstitute of Chemistry, Academia Sinica, 128, Academia Road, Nankang, Taipei 11529, Taiwan
bThe Faculty of Chemistry, Sichuan University, Chengdu 610064, China
Received 12 April 2003; revised 21 May 2003; accepted 21 May 2003
Abstract—Several potential red light-emitting oligomers containing alkoxylated phenylene–vinylene–thienylene backbones with and
without cyano groups at the olefin moieties have been designed and synthesized. The influences of the skeleton as well as the position of the
cyano groups in the vinylene moiety to the absorption and emission spectra of these new oligomers are also discussed. q 2003 Elsevier
Science Ltd. All rights reserved.
1. Introduction
showed that thiophene ring could cause large red shifts in
the absorption spectra.11 The presence of the alkoxy unit
should enhance the solubility of oligomers and the
introduction of high electron affinity of cyano groups on
the vinylene linkages of OPV derivatives has been reported
to lower the energy of the LUMO and reduces the barrier to
the electron injection in LED.12 Thus, PPV derivatives
containing cyano groups on the vinylene linkage present
high electron affinity and therefore exhibit a relatively low
threshold voltage and high quantum efficiency in LED
devices even using stable aluminum electrodes.13 However,
despite its interesting properties in this field, as to our
knowledge, there is no report in the literature about the
synthesis of the oligo(phenylene–vinylene-thiophene)s
(OPVTs) containing with or without cyano groups on the
vinylene linkage.14 Herein, we report the design and
synthesis of a new family of functionalized OPVTs 1–4
(Fig. 1) with definable skeletons that containing a cyano
group at the various position of the vinylene moiety to
strengthen the efficiency of the electron delocalization
within conjugation skeletons.15 This design was aimed at
producing an efficient red OPVT dye.
The synthesis of new oligo(phenylene–vinylene) (OPV)
derivatives has attracted considerable attention1 because of
their widespread application in light-emitting diodes,2
chemical sensors,3 nonlinear optics,4 organic magnetic
materials,5 and flat-panel displays.6 For full-color appli-
cations, it is necessary to have a set of red, green, and blue
emitters with sufficiently high luminous efficiency and
proper chromaticity. After one decade of intensive research,
organic materials for green and blue organic light-emitting
diodes (OLED) with high luminance, high efficiency,
saturated emission, and practical lifetimes have been
developed.7 However, to date, the corresponding develop-
ment of organic materials for red electroluminescence lags
significantly behind that for the other two primary colors.
Presently, most high-performance red OLED are made by
doping a red dye into a suitable host.8 However, their
performance as red emitters is still significantly inferior to
that of the prototypical green and blue emitters. This
problem of color purity is partly due to the fact that a
significant portion of the photoluminescence (PL) peaks of
their emission spectra of these compounds are below
600 nm, and thus they cannot emit a saturated red color.
Thus, the emission peaks of the dopants have to be shifted
further to the long wavelength region, so that the emission
below 600 nm can be substantially reduced. Therefore, there
still remains much room for improvement on the materials
for red OLED. Our preliminary results from ZINDO
calculations9 on our previous PPV type oligomers10 and
with thiophene ring to replace the phenylene moieties
2. Results and discussion
Scheme 1 shows the synthetic protocols for the four target
molecules 1–4. Thus, the Horner–Wadsworth–Emmons
reaction of 2,5-bishexyloxybenzenedicarbaldehyde 516 and
2-(diethoxyphosphorylmethyl)thiophene17 could give mono
condensation product 6 along with some condensation
product at both ends (,25% yield). After column
chromatography, compound 6 was isolated in 39% yield.
The Horner–Wadsworth–Emmons reaction of 2,5-bis-
(diethoxyphosphorylmethyl)thiophene18 with 2 equiv. of
Keywords: CN-OLED; red OLED; oligo(p-phenylene–vinylene–
thienylene); OPVT.
*
Corresponding author. Tel.: þ886-2-27898576; fax: þ886-2-27888199;
e-mail: luoft@chem.sinica.edu.tw
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00783-X

5194
C. Xue, F.-T. Luo / Tetrahedron 59 (2003) 5193–5198
stereochemistry of the vinylene moieties in compound 2
were determined by its 2D NOESY 1H NMR spectral
analysis. The condensation of 2,5-dihexyloxybenzaldehyde
821 with thiophene-2-acetonitrile can afford compound 9 in
97% yield. Formylation of compound 9 via Vilsmeier–
Haack reaction by using phosphorus oxychloride and N,N-
dimethylformamide gave mono-aldehyde 10 regioselec-
tively at a-position of the thienyl group. Knoevenagel
reaction of 2 equiv. of compound 10 with 1 equiv. of 2,5-
bis(cyanomethyl)thiophene could afford compound 3 in
83% yield. Knoevenagel condensation of 2,5-thiophenedi-
carboxaldehyde with 2,5-dihexyloxybenzacetonitrile 1122
could give mono-aldehyde 12 in 47% yield. Another
Knoevenagel condensation of 2 equiv. of compound 12
with 2,5-bis(cyanomethyl)thiophene could afford com-
pound 4 in 82% isolated yield.
Figure 2 shows the UV and PL spectra of oligomers 1–4 and
the lmax of their UV and PL spectral data are shown in
Table 1. Molecules with these definable conjugation
skeletons show that the PL peaks of their emission spectra
of these compounds may reach to pure red emission in
solutions. The lmax of UV spectra for 1–4 are 469, 510, 514,
514 nm, respectively. While the lmax of PL spectra for 1–4
are 567, 602, 644, 615 nm, respectively. The fluorescence
quantum yields for 1–4 in chloroform solution are 0.11,
0.26, 0.05, 0.15, respectively. Interestingly, compound 1
with no cyano groups on the vinylene moiety gave lowest
lmax in both UV and PL spectra. The addition of cyano
groups on the OPVT skeletons results in red shifts in both
UV and PL spectra. The red shifts range from 41 to 45 nm in
UV absorption while 35–77 nm in PL emission. It is
interesting to know that the position of the cyano groups on
the vinylene moieties gave only small differences (0–4 nm)
in UV absorption spectra of 2–4. However, it could cause a
Figure 1. Alkoxylated phenylene–vinylene–thienylene oligomers 1–4.
compound 6 could give compound 1 in 84% isolated yield.
The stereochemistry of the vinylene linkages were con-
firmed by 1H NMR spectral analysis. Similarly, the
Knoevenagel condensation of thiophene-2-acetonitrile19
and dialdehyde 5 could give mono-aldehyde 7 in 36%
yield. The following another Knoevenagel reaction of 2,5-
bis(cyanomethyl)thiophene20 with 2 equiv. of compound 7
could give compound 2 in 80% isolated yield. The E-form
Scheme 1. Synthetic procedures for oligomers 1–4.

C. Xue, F.-T. Luo / Tetrahedron 59 (2003) 5193–5198
5195
compared to the phenylene analogues and need to have
further studied.
4. Experimental
4.1. General procedure
THF was dried by appropriate methods wherever needed.
All organic extracts were dried over anhydrous magnesium
sulfate. TLC was done on aluminum sheets with precoated
silica gel 60 F254 (40£80 mm) from Merck. Purification by
column chromatography was carried out with neutral silica
gel 60 (70–230 mesh ASTM). The purity of each compound
was judged to be .95% by 1H NMR or 13C NMR spectral
analyses. Mps were taken on a MEL-TEMP capillary tube
apparatus and were uncorrected. IR spectra were recorded
as either Nujol mulls or in the solution form as denoted. 1H
NMR and 13C NMR spectra were recorded in CDCl3
solution on either a 300 or 400 MHz instrument using TMS
(0 ppm) and CDCl3 (77.0 ppm) as internal standards.
HRMS spectra were collected on an Autospec orthogonal
acceleration-time of flight mass spectrometer with a
resolution of 6000 (5% valley definition), and fitted with a
magnet bypass flight tube. MALDI-MS spectra were
collected on spectrometer equipped with a nitrogen laser
(337 nm) and operated in the delayed extraction reflector
mode. MS spectra were determined on a Shimadzu QP-1000
spectrometer or Fisons MD800 GC/MS or VG 70-250S
spectrometer. UV and fluorescent spectra were recorded in
CH2Cl2 solution.
Figure 2. The UV and PL spectra (in CH2Cl2) of oligomers 1–4.
Table 1. The lmax of UV and PL in CH2Cl2 and FF in CHCl3 for oligomers
1–4
a
Compound
UV lmax (nm)
PL lmax (nm)
FF
1
2
3
4
469
510
514
514
567
602
644
615
0.11
0.26
0.05
0.15
a
Use Nile Red (FFh 0.33) to compare with in CHCl3.23
big difference (13–42 nm) in PL emission in 2–4.
Compound 2 with only one vinylene-thienylene-vinylene
moiety in the middle skeleton and with four cyano groups
attached at a-position of the vinylene moieties gave a small
blue shift in both UV and PL spectra (4 and 13 nm,
respectively) than that of compound 4, but, gave a big blue
shift in PL spectra (42 nm) than that of compound 3.
Compound 3 with three thienylene-vinylene linkages in the
middle of the skeleton and with four cyano groups attached
at a-position of the vinylene moieties for the 2-thienyl units
gave the highest lmax in both UV and PL spectra.
Compound 4 with only two cyano groups attached at
a-position of the vinylene moieties for the 2-thienyl units
gave significant blue shift (,29 nm) than that of compound
3. Thus, the more thienylene-vinylene linkages and the more
cyano groups attached at a-position of the vinylene moieties
for the 2-thienyl units gave significant red shifts in PL
spectra. The preparation of devices and their electro-optical
properties are still under active investigation in our
collaborator’s lab, and their results will be reported
elsewhere when they are available.
4.1.1. Preparation of 4-[(1E)-2-(2-thienyl)vinyl]-2,5-
dihexyloxybenzaldehyde 6. To a solution of compound
516 (0.33 g, 1.0 mmol) and NaH (0.024 g, 1.0 mmol) in
dry THF (5 mL) was added dropwise the solution of 2-
(diethoxyphosphorylmethyl)thiophene17 (0.23 g, 1.0 mmol)
in dry THF (5 mL), the mixture was stirred at 08C for 4 h. then
poured into water (20 mL), extracted with EtOAc (10 mL£3).
Organic layer was washed with brine (3£50 mL), dried over
MgSO4. The solvent was evaporated, the residue was purified
by column chromatography (silica gel, hexane/EtOAc¼25:1)
to give compound 6 as a yellow solid (0.16 g, 39%). Mp 52–
538C. IR (CH2Cl2) 3050, 2933, 2930, 2872, 2859, 1675, 1598,
1487, 1468, 1423, 1387 cm21. 1H NMR (300 MHz, CDCl3) d
0.92 (t, J¼7 Hz, 6H), 1.35–1.38 (m, 8H), 1.50–1.53 (m, 4H),
1.82–1.87 (m, 4H), 4.03 (t, J¼6.4 Hz, 2H), 4.11 (t, J¼6.4 Hz,
2H), 7.03 (dd, J¼3.0, 5.0 Hz, 1H), 7.10 (s, 1H), 7.13 (d,
J¼3.0 Hz, 1H), 7.25 (d, J¼16.0 Hz, 1H), 7.26 (d, J¼5.0 Hz,
1H), 7.31 (s, 1H), 7.43 (d, J¼16.0 Hz, 1H), 10.44 (s, 1H) ppm.
13C NMR (75 MHz, CDCl3) d 14.03, 22.61, 25.76, 25.84,
29.18, 31.54, 69.10, 69.18, 110.09, 110.57, 122.66, 124.04,
125.38, 125.50, 127.00, 127.74, 133.85, 143.01, 150.67,
156.17, 189.13 ppm. MS m/z 414 (Mþ), HRMS calcd for
C25H34O3S 414.2229, found 414.2237.
3. Conclusion
Four alkoxylated phenylene–vinylene–thienylene
oligomers have been synthesized efficiently. The emission
wavelength of oligomers 3 and 4 have reached to the range
of red light-emitting. Our results show that the more
thienylene-vinylene linkages and the more cyano groups
attached at a-position of the vinylene moieties for the
2-thienyl units gave significant red shifts in both absorption
and emission spectra. The relationship between the position
of thiophene and cycno group and their absorption and
emission spectra of these oligomers is very interesting as
4.1.2. Preparation of 1-[(1E)-2-(5-{(1E)-2-[4-((1E)-2-(2-
thienyl)vinyl)-2,5-di- hexyloxphenyl]vinyl}(2-thienyl))-
vinyl]-4-((1E)-2-(2-thienyl)vinyl)-2,5-dihexyloxy-
benzene 1. Compound 6 (0.21 g, 0.5 mmol) and 2,5-
bis(diethoxyphosphorylmethyl)-thiophene18 (0.1 g, 0.25
mmol) were dissolved in dry THF (5 mL), and NaH
(0.012 g, 0.5 mmol) was added. The reaction mixture was

5196
C. Xue, F.-T. Luo / Tetrahedron 59 (2003) 5193–5198
stirred at 08C for 16 h, and then poured into water (20 mL),
extracted with EtOAc (10 mL£3), washed with brine
(3£50 mL), dried over MgSO4. The solvent was evaporated,
the residue was purified by column chromatography (silica
gel, hexane/CH2Cl2/EtOAc¼5:1:0.01) to give oligomer 1 as
a red solid (0.19 g, 84%). Mp 99–1008C. IR (CH2Cl2) 3056,
2957, 2931, 2858, 1605, 1522, 1494, 1468, 1430, 1419,
1389 cm21. 1H NMR (300 MHz, CDCl3) d 0.93 (t, J¼7 Hz,
12H), 1.38–1.42 (m, 16H), 1.54–1.58 (m, 8H), 1.82–1.89
(m, 8H), 3.98–4.04 (m, 8H), 6.93 (s, 2H), 7.01 (d,
J¼16.0 Hz, 4H), 7.02 (s, 4H), 7.04 (d, J¼3.0 Hz, 2H),
7.16 (d, J¼5.0 Hz, 2H), 7.23 (dd, J¼3.0, 5.0 Hz, 2H), 7.25
(d, J¼16.0 Hz, 4H) ppm. 13C NMR (75 MHz, CDCl3) d
14.06, 22.65, 25.93, 29.43, 31.64, 69.31, 69.47, 110.60,
110.68, 122.07, 122.37, 123.40, 123.45, 124.10, 125.61,
126.35, 126.40, 126.81, 127.53, 142.80, 143.85, 151.04,
151.09 ppm. MS m/z 904 (Mþ), HRMS calcd for
C56H72O4S3 904.4593, found 904.4606.
J¼5.0 Hz, 2H), 7.36 (s, 2H), 7.40 (d, J¼3.4 Hz, 2H), 7.84
(s, 2H), 7.85 (s, 2H), 7.88 (s, 4H) ppm. 13C NMR (75 MHz,
CDCl3) d 14.00, 22.62, 25.79, 25.85, 29.07, 29.14, 31.54,
69.45, 69.48, 105.39, 106.38, 110.87, 110.98, 116.67,
117.15, 125.08, 126.05, 126.60, 127.33, 127.88, 128.16,
133.11, 134.05, 139.82, 140.64, 151.50, 151.69 ppm. MS
m/z 1027 (MþþNa), 1004 (Mþ), HRMS calcd for
C60H68N4O4S3 1004.4403, found 1004.4416.
4.1.5. Preparation of (2E)-3-(2,5-dihexyloxyphenyl)-2-(2-
thienyl)prop-2-enenitrile 9. K2CO3 (1.38 g, 10 mmol) was
added to the solution of 2,5-dihexyloxybenzaldehyde 821
(3.0 g, 10 mmol) and thiophene-2-acetonitrile (1.23 g,
10 mmol) in CH3OH (10 mL). The mixture was stirred at
room temperature for 10 h, and then poured into water
(30 mL), extracted with EtOAc (10 mL£3). The organic
layer was washed with brine (3£20 mL), dried over MgSO4.
The solvent was removed, the residue was purified by
column chromatography (silica gel, hexane/EtOAc¼5:0.2)
to give compound 9 as a yellow solid (4.0 g, 97%). Mp 42–
438C. IR (CH2Cl2) 3036, 2951, 2934, 2866, 2859, 2218,
4.1.3. Preparation of (2E)-3-(4-formyl-2,5-dihexyloxy-
phenyl)-2-(2-thienyl)prop-2- enenitrile 7. K2CO3 (0.69 g,
5.0 mmol) was added to the solution of compound 5 (1.7 g,
1
1607, 1575, 1519, 1492, 1467, 1433, 1379, 1340 cm21. H
5.0 mmol)
and
thiophene-2-acetonitrile19
(0.62 g,
NMR (300 MHz, CDCl3) d 0.92 (t, J¼7 Hz, 6H), 1.30–1.60
(m, 12H), 1.70–1.90 (m, 4H), 3.90–4.01 (m, 4H), 6.85 (d,
J¼8.9 Hz, 1H), 6.94 (dd, J¼8.9, 2.9 Hz, 1H), 7.05 (dd,
J¼5.2, 3.8 Hz, 1H), 7.27 (d, J¼5.2 Hz, 1H), 7.36 (d,
J¼3.8 Hz, 1H), 7.73 (d, J¼2.9 Hz, 1H), 7.85 (s, 1H) ppm.
13C NMR (75 MHz, CDCl3) d 13.99, 22.58, 25.71, 25.81,
29.25, 31.53, 31.58, 68.76, 69.41, 105.35, 112.58, 113.53,
117.11, 119.28, 123.11, 125.83, 126.64, 127.94, 134.75,
139.97, 151.88, 152.96 ppm. MS m/z 411 (Mþ), HRMS
calcd for C25H33NO2S 411.2232, found 411.2224.
5.0 mmol) in CH3OH (10 mL). The mixture was stirred at
room temperature. After 8 h, the reaction mixture was
poured into water (30 mL), extracted with EtOAc
(10 mL£3). The organic layer was washed with brine
(3£20 mL), dried over MgSO4. The solvent was removed,
the residue was purified by column chromatography (silica
gel, hexane/EtOAc¼5:0.2) to give title compound 7 as a
yellow solid (0.8 g, 36%). Mp 41–428C. IR (CH2Cl2) 3054,
2956, 2933, 2872, 2860, 2217, 1680, 1611, 1487, 1467,
1
1424, 1387 cm21. H NMR (300 MHz, CDCl3) d 0.92 (t,
J¼7 Hz, 6H), 1.35–1.37 (m, 8H), 1.57–1.60 (m, 4H),
1.85–1.89 (m, 4H), 4.04 (t, J¼6.3 Hz, 2H), 4.15 (t,
J¼6.3 Hz, 2H), 7.08 (dd, J¼3.0, 5.0 Hz, 1H), 7.34 (s, 1H),
7.35 (d, J¼5.0 Hz, 1H), 7.42 (d, J¼3.0 Hz, 1H), 7.84 (s,
2H), 10.48 (s, 1H) ppm. 13C NMR (75 MHz, CDCl3) d
13.97, 22.56, 25.74, 29.07, 31.49, 69.25, 69.36, 108.06,
109.85, 112.44, 116.78, 126.25, 126.95, 127.77, 128.19,
129.37, 133.17, 139.39, 151.39, 155.54, 189.07 ppm. MS
m/z 439 (Mþ), HRMS calcd for C26H33NO3S 439.2181,
found 439.2185.
4.1.6. Preparation of (2E)-3-(2,5-dihexyloxyphenyl)-2-(5-
formyl(2-thienyl))prop-2-enenitrile 10. The mixture of
POCl3 (1.61 g, 10.5 mmol) and DMF (0.77 g, 10.5 mmol)
was stirred at room temperature for 1 h, and then compound
9 (1.0 g, 2.4 mmol) was added. The reaction mixture was
continually stirred at room temperature for 1 h and 608C for
4 h. After cooling, the mixture was poured into 15%
NaHCO3 (20 mL), extracted with EtOAc (10 mL£3). The
organic layer was washed with brine (3£20 mL), dried over
MgSO4. The solvent was removed, the residue was purified
by column chromatography (silica gel, hexane/
EtOAc¼5:0.2) to give compound 10 as a yellow solid
(0.47 g, 45%). Mp 35–368C. IR (CH2Cl2) 2952, 2932, 2873,
2859, 2218, 1673, 1607, 1586, 1494, 1468, 1431,
4.1.4. Preparation of (2E)-3-{4-[(1E)-2-(5-{(1E)-2-[4-
((1E)-2-cyano-2-(2-thienyl)-vinyl)-2,5-dihexyloxy-
phenyl]-1-cyanovinyl}(2-thienyl))-2-cyanovinyl]-2,5-
dihexyloxyphenyl}-2-(2-thienyl)prop-2-enenitrile
2.
1387 cm21 1H NMR (300 MHz, CDCl3) d 0.91 (t,
.
Compound 7 (0.34 g, 0.78 mmol) and 2,5-bis-(cyano-
methyl)thiophene20 (0.06 g, 0.39 mmol) were dissolved in
CH3OH (5 mL), and K2CO3 (0.11 g, 0.8 mmol) was added.
The reaction mixture was stirred at room temperature for
16 h, the then poured into water (15 mL), extracted with
CH2Cl2 (10 mL£3). The organic layer was washed with
brine (3£20 mL), dried over MgSO4. The solvent was
evaporated, the residue was purified by column chromato-
graphy (silica gel, hexane/CH2Cl2/EtOAc¼5:1:0.01) to give
oligomer 2 as a brown solid (0.31 g, 80%). Mp 177–1788C.
IR (CH2Cl2) 3054, 2984, 2932, 2859, 2218, 1606, 1493,
1468, 1429, 1378 cm21. 1H NMR (300 MHz, CDCl3) d 0.88
(t, J¼7.0 Hz, 6H), 0.92 (t, J¼7.0 Hz, 6H), 1.35–1.56 (m,
24H), 1.84–1.91 (m, 8H), 4.11 (t, J¼7.0 Hz, 4H), 4.13 (t,
J¼7.0 Hz, 4H), 7.08 (dd, J¼5.0, 3.4 Hz, 2H), 7.33 (d,
J¼7 Hz, 6H), 1.36–1.39 (m, 8H), 1.47–1.51 (m, 4H),
1.82–1.87 (m, 4H), 3.99 (m, 4H), 6.86 (d, J¼9.0 Hz, 1H),
7.01 (dd, J¼2.7, 9.0 Hz, 1H), 7.44 (d, J¼4.0 Hz, 1H), 7.72
(d, J¼4.0 Hz, 1H), 7.78 (d, J¼2.7 Hz, 1H), 8.09 (s, 1H),
9.89 (s, 1H) ppm. 13C NMR (75 MHz, CDCl3) d 13.98,
22.55, 25.67, 25.74, 29.12, 29.15, 31.46, 31.53, 68.70,
69.33, 104.08, 112.25, 113.45, 120.27, 120.84, 127.00,
135.37, 136.86, 138.08, 142.73, 148.99, 152.43, 152.84,
182.49 ppm. MS m/z 439 (Mþ), HRMS calcd for
C26H33NO3S 439.2181, found 439.2182.
4.1.7. Preparation of (2E)-2-[5-((1E)-2-{5-[(1E)-2-(2,5-
dihexyloxyphenyl)-1-cyano-vinyl](2-thienyl)}-1-cyano-
vinyl)(2-thienyl)]-3-{5-[(1E)-2-(2,5-dihexyloxyphenyl)-1-
cyanovinyl](2-thienyl)}prop-2-enenitrile
3.
K2CO3

C. Xue, F.-T. Luo / Tetrahedron 59 (2003) 5193–5198
5197
(0.05 g, 0.36 mmol) was added to the solution of compound
10 (0.16 g, 0.36 mmol) and 2,5-bis(cyanomethyl)thiophene
(0.03 g, 0.18 mmol) in CH3OH (5 mL). The mixture was
stirred at room temperature for 12 h, and then poured into
water (10 mL), extracted with CH2Cl2 (10 mL£3). The
organic layer was washed with brine (3£15 mL), dried over
MgSO4. The solvent was removed, the residue was purified
by column chromatography (silica gel, hexane/CH2Cl2/
EtOAc¼5:1:0.02) to give oligomer 3 as a brown solid
(0.15 g, 83%). Mp 116–1178C. IR (CH2Cl2) 3059, 2953,
2932, 2859, 2215, 1606, 1492, 1467, 1428, 1377 cm21. 1H
NMR (300 MHz, CDCl3) d 0.92 (t, J¼7 Hz, 12H), 1.34–
1.37 (m, 16H), 1.48–1.52 (m, 8H), 1.71–1.87 (m, 8H),
3.96–4.02 (m, 8H), 6.86 (d, J¼9.0 Hz, 2H), 6.97 (dd,
J¼9.0, 2.7 Hz, 2H), 7.30 (s, 2H), 7.36 (s, 2H), 7.38 (d,
J¼4.0 Hz, 2H), 7.53 (d, J¼4.0 Hz, 2H), 7.74 (d, J¼2.7 Hz,
2H), 7.97 (s, 2H) ppm. 13C NMR (75 MHz, CDCl3) d 14.02,
14.18, 22.60, 25.77, 29.26, 31.48, 31.60, 68.81, 69.45,
102.99, 104.43, 112.45, 113.56, 116.05, 116.51, 120.46,
122.63, 127.24, 128.10, 131.54, 133.83, 136.87, 137.36,
139.39, 144.97, 152.38, 152.97 ppm. MS m/z 1005 (Mþþ1),
HRMS calcd for C60H68N4O4S3 1005.4481 (Mþþ1), found
1005.4477.
2932, 2859, 2213, 1606, 1582, 1499, 1468, 1387 cm21. 1H
NMR (300 MHz, CDCl3) d 0.91 (t, J¼7 Hz, 12H), 1.34–
1.36 (m, 16H), 1.42–1.49 (m, 8H), 1.72–1.89 (m, 8H), 3.94
(t, J¼6.0 Hz, 4H), 4.02 (t, J¼6.0 Hz, 4H), 6.88 (s, 4H), 7.05
(s, 2H), 7.34 (s, 2H), 7.42 (s, 2H), 7.77 (s, 4H), 7.84 (s,
2H) ppm. 13C NMR (75 MHz, CDCl3) d 14.01, 22.59,
25.71, 25.93, 29.24, 29.30, 31.58, 68.82, 69.64, 104.04,
108.63, 114.00, 115.74, 116.10, 116.62, 118.15, 123.63,
128.47, 131.24, 131.75, 132.35, 136.32, 139.59, 139.96,
142.43, 150.85, 153.25 ppm. MS m/z 1004 (Mþ), HRMS
calcd for C60H68N4O4S3 1004.4403, found 1004.4417.
Acknowledgements
We thank the National Science Council and Academia
Sinica of the Republic of China for financial support.
References
1. (a) Tour, J. M. Acc. Chem. Res. 2000, 33, 791. (b) Bunz, U. F.
W. Chem. Rev. 2000, 100, 1605. (c) In Electronic Materials:
The Oligomer Approach; Mullen, K., Wegner, G., Eds.;
Wiley-VCH: Weinheim, Germany, 1998. (d) Oelkrug, D.;
Tompert, A.; Gierschner, J.; Egelhaaf, H.-J.; Hanack, M.;
Hohloch, M.; Steinhuber, E. J. Phys. Chem. B 1998, 102, 1902.
2. (a) Sheats, J. R.; Antoniadis, H.; Mueschen, M.; Leonard, W.;
Miller, J.; Moon, R.; Roitman, D.; Stocking, A. Science 1996,
273, 884. (b) Tang, C. W.; Van Slyke, S. A.; Chen, C. H.
J. Appl. Phys. 1989, 65, 3610. (c) Service, R. F. Science 1996,
273, 878. (d) Tang, C. W.; Van Slyke, S. A. Appl. Phys. Lett.
1987, 51, 913.
4.1.8. Preparation of (2Z)-2-(2,5-dihexyloxyphenyl)-3-(5-
formyl(2-thienyl))prop-2-enenitrile 12. To a solution of
2,5-thiophenedicarboxaldehyde (0.09 g, 0.63 mmol) and
K2CO3 (0.09 g, 0.63 mmol) in CH3OH (5 mL) was added
dropwise the solution of 2,5-bis(hexyloxyphenyl)aceto-
nitrile 1122 (0.20 g, 0.63 mmol) in CH3OH (2 mL). The
mixture was stirred at room temperature for 16 h, and then
poured into water (20 mL), extracted with EtOAc
(10 mL£3). Organic layer was washed with brine
(3£50 mL), dried over MgSO4. The solvent was evaporated,
the residue was purified by column chromatography (silica
gel, hexane/EtOAc¼25:1) to give compound 12 as a yellow
solid (0.13 g, 47%). Mp 96–978C. IR (CH2Cl2) 3050, 2953,
2932, 2870, 2857, 2214, 1673, 1605, 1498, 1468, 1438,
1386 cm21. 1H NMR (300 MHz, CDCl3) d 0.91 (t, J¼7 Hz,
6H), 1.35–1.38 (m, 8H), 1.46–1.49 (m, 4H), 1.84–1.89 (m,
4H), 3.94 (t, J¼6.4 Hz, 2H), 4.01 (t, J¼6.4 Hz, 2H), 6.89 (s,
2H), 7.06 (s, 1H), 7.77 (d, J¼4.0 Hz, 1H), 7.79 (d,
J¼4.0 Hz, 1H), 7.87 (s, 1H), 9.96 (s, 1H) ppm. 13C NMR
(75 MHz, CDCl3) d 13.95, 22.53, 25.65, 25.86, 29.16,
29.23, 31.50, 68.75, 69.52, 110.53, 113.89, 115.90, 116.75,
117.57, 123.18, 130.98, 135.72, 136.35, 144.81, 146.16,
150.84, 153.17, 182.70 ppm. MS m/z 439 (Mþ), HRMS
calcd for C26H33NO3S 439.2181, found 439.2180.
3. (a) Irie, M. Chem. Rev. 2000, 100, 1685. (b) Repinec, S. T.;
Sension, R. J.; Szarka, A. Z.; Hochstrasser, R. M. J. Phys.
Chem. 1991, 95, 10380.
4. (a) Bosshard, C.; Sutter, K.; Pretre, P.; Hulliger, J.;
Florsheimer, M.; Kaatz, P.; Gunter, P. Organic Nonlinear
Optical Materials; Gordon & Breach: Amsterdam, 1995; Vol.
1. (b) Nalwa, H. S.; Myata, S. Nonlinear Optics of Organic
Molecules and Polymers; CRC: Boca Raton, FL, 1997.
5. (a) Wienk, M. M.; Janssen, R. A. J. J. Am. Chem. Soc. 1996,
118, 10625. (b) Wienk, M. M.; Janssen, R. A. J. J. Am. Chem.
Soc. 1997, 119, 4492.
6. (a) Tang, C. W. Proceedings, Society for Information Display;
Society for Information Display: Los Angeles, CA, 1996;
p 181. (b) Sheat, J. R.; Antoniadis, H.; Hueschen, M.; Leonard,
W.; Miller, J.; Moon, R.; Roitman, D.; Stocking, A. Science
1996, 273, 884.
4.1.9. Preparation of 3-(5-{(1E)-2-[5-((1E)-2-{5-[(1Z)-2-
(2,5-dihexyloxyphenyl)-2-cyanovinyl](2-thienyl)}-1-
cyanovinyl)(2-thienyl)]-2-cyanovinyl}(2-thienyl))(2Z)-2-
7. (a) Wakimoto, T.; Murayama, R.; Nagayama, K.; Okuda, Y.;
Nakada, H.; Tohma, T. SID96 Dig. 1996, 849. (b) Nakamura,
H.; Hosokawa, C.; Kusumoto, T. In Inorganic and Organic
Electroluminescence/EL 96, Berlin; Mauch, R. H., Gumlich,
H. E., Eds.; Wissenschaft und Technik: Berlin, 1996; p 65.
8. (a) Chen, C. H.; Shi, J.; Tang, C. W. Macromol. Symp. 1997,
125, 1. (b) Shoustikov, A. A.; You, Y.; Thompson, M. E. IEEE
J. Sel. Top. Quantum Electron. 1998, 4, 3. (c) Tang, C. W.;
Van Slyke, S. A.; Chen, C. H. J. Appl. Phys. 1989, 65, 3610.
(d) Bulovic, V.; Shoustikov, A.; Baldo, M. A.; Bose, E.;
Kozlov, V. G.; Thompson, M. E.; Forrest, S. R. Chem. Phys.
Lett. 1998, 287, 455. (e) Tang, C. W. Dig. Soc. Inf. Display
1996, 27, 181. (f) Burrows, P. E.; Forrest, S. R.; Sibley, S. P.;
(2,5-dihexyloxyphenyl)prop-2-enenitrile
4.
K2CO3
(0.05 g, 0.36 mmol) was added to the solution of compound
12 (0.15 g, 0.34 mmol) and 2,5-bis(cyanomethyl)thiophene
(0.03 g, 0.17 mmol) in CH3OH (5 mL). The mixture was
stirred at room temperature for 15 h, and then poured into
water (10 mL), extracted with CH2Cl2 (10 mL£3). The
organic layer was washed with brine (3£15 mL), dried over
MgSO4. The solvent was removed, the residue was purified
by column chromatography (silica gel, hexane/CH2Cl2/
EtOAc¼5:1:0.02) to give oligomer 4 as a brown solid
(0.14 g, 82%). Mp 115–1168C. IR (CH2Cl2) 3050, 2959,

5198
C. Xue, F.-T. Luo / Tetrahedron 59 (2003) 5193–5198
Thompson, M. E. Appl. Phys. Lett. 1996, 69, 2959.
14. (a) Wynberg, H.; Sinnige, H. J. M.; Creemers, H. M. J. C.
J. Org. Chem. 1971, 36, 1011. (b) Chen, L. H.; Wang, C. Y.;
Luo, T. M. H. Heterocycles 1994, 38, 1393. (c) Kagan, J.;
Arora, S. K. Heterocycles 1983, 10, 1941. (d) Parakka, J. P.;
Cava, M. P. Synth. Met. 1995, 68, 275. (e) Carpta, A.; Rossi,
R.; Veracini, C. A. Tetrahedron 1985, 41, 1919. (f) Hucke, A.;
Cava, M. P. J. Org. Chem. 1998, 63, 7413. (g) Luo, F. T.;
Bajji, A. C.; Jeevanandam, A. J. Org. Chem. 1999, 64, 1738.
15. (a) Reinhardt, B. A.; Brott, L. L.; Clarson, S. J.; Dillard, A. G.;
Bhatt, J. C.; Kannan, R.; Yuan, L.; He, G. S.; Prasad, P. N.
Chem. Mater. 1998, 10, 1863. (b) Albota, M.; Beljonne, D.;
Bredas, J. L.; Ehrlich, J. E.; Fu, J. Y.; Heikal, A. A.; Hess, S. E.;
Kogej, T.; Levin, M. D.; Marder, S. R.; McCordMaughon, D.;
Perry, J. W.; Rockel, H.; Rumi, M.; Subramaniam, G.; Webb,
W. W.; Wu, X. L.; Xu, C. Science 1998, 281, 1653.
16. Sarker, A. M.; Ding, L.; Lahti, P. M.; Karasz, F. E.
Macromolecules 2002, 1, 223.
(g) Thompson, M. E.; Shoustikov, A.; You, Y.; Sibley, S.;
Baldo, M.; Koslov, V.; Burrows, E. P.; Forrest, S. R. Presented
at the Mater. Res. Soc. Abstr. G2.4, Spring Meeting, 1998.
(h) Baldo, M. A.; O’Brien, D. F.; You, Y.; Shoustikov, A.;
Sibley, S.; Thompson, M. E.; Forrest, S. R. Nature 1998, 395,
151. (i) O’Brien, D. F.; Baldo, M. A.; Thompson, M. E.;
Forrest, S. R. Appl. Phys. Lett. 1999, 74, 442. (j) Kido, J.;
Nagai, K.; Okamato, Y.; Skotheim, T. Chem. Lett. 1991, 1267.
(k) Kido, J.; Nagai, K.; Okamato, Y.; Skotheim, T. Chem. Lett.
1991, 1267. (l) Kido, J.; Nagai, K.; Okamato, Y.; Skotheim, T.
Chem. Lett. 1991, 1267. (m) Kwong, R. C.; Sibley, S.;
Dubovoy, T.; Baldo, M.; Forrest, S. R.; Thompson, M. E.
Chem. Mater. 1999, 11, 3709. (n) Chen, C. H.; Tang, C. W.;
Shi, J.; Klubek, P. Macromol. Symp. 1997, 125, 49. (o) Yu, J.;
Shitota, Y. Chem. Lett. 2002, 984.
9. Wang, B. C.; Chang, J. C.; Tso, H. C.; Cheng, C. Y. Chemistry
2001, 59, 545, and references cited therein.
17. Juzo, N.; Toru, F. Heterocycles 1991, 32, 991.
18. Anna, B.; Silvia, B.; Raffaella, F.; Giorgio, A. P.; France, S.
J. Chem. Soc., Perkin Trans. 1 1987, 2631.
10. Luo, F. T.; Tao, Y. T.; Ko, S. L.; Chuen, C. H.; Chen, H.
J. Mater. Chem. 2002, 12, 47.
11. In general, heteroaromatic PPV derivatives have a lower
HOMO–LUMO gap in comparison to the analogues
phenylene based structures: Eckhardt, H.; Shacklette, L. W.;
Jen, K. Y.; Elsenbaumer, R. L. J. Chem. Phys. 1989, 91, 1303.
12. Bredas, J. L. Adv. Mater. 1995, 7, 263.
19. Blicke, F. F.; Leonard, F. J. Am. Chem. Soc. 1946, 68, 1934.
20. Rafael, G.; Jose, L. S.; Nazario, M. J. Org. Chem. 2000, 65,
7501.
21. (a) Martinez-Ruiz, P.; Behnisch, B.; Schweikart, K. H.;
Hanack, M.; Lu¨er, L.; Oelkrug, D. Chem. Eur. J. 2000, 6,
1294. (b) Maddux, T.; Li, W.; Yu, L. J. Am. Chem. Soc. 1997,
119, 844.
13. (a) Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend,
R. H.; Holmes, A. B. Nature 1993, 365, 628. (b) Moratti, S. C.;
Cervini, R.; Holmes, A. B.; Baigent, D. R.; Friend, R. H.;
Greenham, N. C.; Gru¨ner, J.; Hamer, P. J. Synth. Met. 1995,
71, 2117. (c) Holmes, A. B.; Friend, R. H.; Moratti, S. C.;
Baigent, D. R.; Bradley, D. D. C.; Cervini, R.; Greenham,
N. C.; Hamer, J. P. C. Int. Appl. WO94/29,883; Chem. Abstr.
1995, 123, 973318d.
22. Behnisch, B.; Martinez-Ruiz, P.; Schweikart, K. H.; Hanack,
M. Eur. J. Org. Chem. 2000, 14, 2541.
23. Dutta, A. K.; Kamada, K.; Ohta, K. J. Photochem. Photobiol.
A: Chem. 1996, 93, 57.