Synthesis, optical properties, and characterization of new soluble conjugated poly(p-phenylenevinylene) derivatives constituted of alternating pyrazole and 1,3,4-oxadiazole moieties

Article abstract of DOI:10.1071/CH07381

Two new soluble poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole and pyrazole rings along the main core were successfully synthesized by 1,3-dipolar addition, dehydration, and Heck coupling reaction. The new conjugated polymers are soluble in c

Full text of DOI:10.1071/CH07381

Full Paper
CSIRO PUBLISHING
Aust. J. Chem. 2008, 61, 342–349
www.publish.csiro.au/journals/ajc
Synthesis, Optical Properties, and Characterization of
New Soluble Conjugated Poly(p-phenylenevinylene)
Derivatives Constituted of Alternating Pyrazole
and 1,3,4-Oxadiazole Moieties
En-Ming Chang,A Cheng-Tien Lee,A Chun-Yen Chen,A Fung Fuh Wong,B,D
and Mou-Yung YehA,C,D
ADepartment of Chemistry, National Cheng Kung University, Tainan 70101, Taiwan, Republic of China.
BGraduate Institute of Pharmaceutical Chemistry, China Medical University,
Taichung 40402, Taiwan, Republic of China.
CSustainable Environment Research Center, National Cheng Kung University,
Tainan City 709, Taiwan, Republic of China.
DCorresponding author. Email: wongfungfuh@yahoo.com.tw
Two new soluble poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole and pyrazole rings along the main core
were successfully synthesized by 1,3-dipolar addition, dehydration, and Heck coupling reaction. The new conjugated
polymers are soluble in common organic solvents afforded by the fully conjugated backbone with soluble dedecyloxy
side groups. The polymers showed relatively high glass-transition temperatures (∼150◦C) and good satisfactory thermal
stability. Solutions of the polymers emitted bluish-green light with photoluminescence (PL) emission maxima around
530–540 nm. The PL spectrum for polymers of thin films, with a maximum at 570 nm, shows a red-shift (∼35 nm) with
respect to the solution spectrum. Cyclic voltammetry displayed that both conjugated polymers had reversible reduction
and irreversible oxidation, making them n-type electroluminescent materials. The electron affinity of new polymers was
estimated as 2.76–2.81 eV. The weight-average molecular weights (Mw) of the new soluble polymers were in the range
3400–3500.
Manuscript received: 31 October 2007.
Final version: 20 March 2008.
Introduction
were revealed as efficient blue-greenish electroluminescent
materials.[30] As a result, we introduced pyrazole units into the
main chain of 1,3,4-oxadiazole-based conjugated polymers as
the chromophore to improve the electron-transporting proper-
ties, as pyrazole is an electron-rich heterocycle.[30] Sydnones
are an important and frequent structural feature in organic chem-
istry. In this work, sydnones underwent 1,3-dipolar addition[30]
with acetylenedicaboxylate to provide functional pyrazole com-
pounds.These new soluble PPV-based conjugated polymers with
1,3,4-oxadiazole and pyrazole rings in the backbone were suc-
cessfully synthesized by dehydration[31] and Heck coupling[29]
from the functional pyrazole intermediates.
Since the first poly(p-phenylenevinylene) (PPV) was devel-
oped as a polymer light-emitting diode (PLED),[1–12] the π-
conjugated polymeric derivatives have been studied extensively
because of their multifunctional application.[11–17] Typically,
conjugated polymers such as PPV, poly(thiophene) (PT), and
their derivatives tend to p-type, that is, they favour hole-
transport.[18,19] Because of the scarcity of known polymers
with good soluble activity and electron-injection capability,
soluble π-conjugated electroluminescent polymers that con-
tain electron-withdrawing units in the main chain or at side
groups have been targeted in the development of polymers with
improved electron-transport capability.
Result and Discussion
Aromatic 1,3,4-oxadiazole-based conjugated polymers have
beenshowntobepromisingcandidatesforlight-emittingdevices
because of their thermal, hydrolytic, and photo stability,[20–25]
electron affinity, and hole-blocking ability.[19,26,27] 1,3,4-
Oxadiazole-based heterocyclic conjugated polymers were also
enthusiastically investigated to improve the electron injection,
transport properties, and to confer rigidity, for example, 1,3,4-
oxadiazole–carbazole[28] and 1,3,4-oxadiazole–pyridine.[29]
In our previous work, the chromophore of pyrazole played
an assistant role in controlling the fundamental electrolumines-
cent process and 1,3,4-oxadiazole-based pyrazole derivatives
Synthesis
The synthetic route is shown in Scheme 1 for the generation
of two 1,3,4-oxadiazole-based pyrazole monomer derivatives 5a
and 5b. Considering the large-scale preparation of sydnone sub-
strates, the commercial available raw materials hydrazine with
various para-H, and -OMe substituent groups were selected
as the starting materials to synthesize sydnone compounds
1a and 1b. Sydnone 1a and 1b were prepared by following
the procedure developed by our laboratory.[32] Sydnone com-
pounds 1a and 1b with various substituents on the N1-phenyl
© CSIRO 2008
10.1071/CH07381
0004-9425/08/050342

New Soluble Conjugated Poly(p-phenylenevinylene) Derivatives
343
MeOOC
MeOOC
N
MeOOC
COOMe
ϩ
N
O
R
R
N
Ϫ
Toluene
N
O
1a R ϭ H, 1b R ϭ OMe
2a R ϭ H, 93%, 2b R ϭ OMe, 91%
O
p-BrPh
Cl
H2NHNOC
H2NHNOC
4
NH2NH2·H2O
EtOH
N
N
R
Pyridine, CH2Cl2
3a R ϭ H, 74%, 3b R ϭ OMe, 76%
R
R
N
POCl3
N
N
N
Br
Br
HN
HN
O
NH
NH
O
O
O
O
O
N
N
N
N
Br
Br
6a R ϭ H, 89%, 6b R ϭ OMe, 92%
5a R ϭ H, 75%, 5b R ϭ OMe, 73%
Scheme 1.
OC12H25
OC12H25
OH
Br
C12H25Br
Br2, AlCl3
t-Bu4NBr, KOH
CH2Cl2
Br
OC12H25
OH
OC12H25
7
8
9
OC12H25
SnBu3
PPh3, toluene
OC12H25
10
Scheme 2.
group, including para-H, and -OMe groups were applied to
dimethyl acetylenedicaboxylate (DMAD) to give the corre-
spondingdimethyl1-aryl-1H-pyrazole-3,4-dicarboxylate2a and
2b as a white solid in almost quantitative yields (91–93%).[33]
This 1,3-dipolar cyclization has proved to be an efficient and
economical way to provide the pyrazole derivatives. Treating 1-
aryl-1H-pyrazole-3,4-dicarboxylate 2a and 2b with hydrazine
hydrate at reflux afforded the corresponding dihydrazide prod-
uct 3a and 3b in good yield (74–76%) according to published
reports.[34]
3-(4-Bromophenyl)acrylic acid was efficiently transformed
into the corresponding 3-(4-bromophenyl)acryloyl chloride 5 in
72% yield by using pyridine and thionyl chloride in CH2Cl2 at
0◦C to room temperature for 3 h. Dihydrazide compounds 3a
and 3b were treated with 3-(4-bromophenyl)acryloyl chloride 4
in CH2Cl2 at room temperature for 2–3 h to give the correspond-
ing bis(trihydrazide) products 5a and 5b in 73–75% yields.[35]
Compounds 5a and 5b underwent dehydration–cyclization to
form the 1,3,4-oxadiazole-based pyrazole derivatives 6a and 6b
in 89–92% excellent yields[31] in the presence of POCl3.
The synthetic route of 1,4-didodecyloxy-2,5-divinylbezene
10 is outlined in Scheme 2. 1,4-Dibromo-2,5-didodecyloxy-
bezene 9 was easily synthesized in two steps with a total yield
of 64% using 1,4-hydroxybezene 7 as starting material fol-
lowing the reported procedure.[36] Eventually, Stille coupling
of 1,4-dibromo-2,5-didodecyloxybezene 9 with 2.2 equiv. of
vinyltin reagent was performed to give the coupled product
1,4-didodecyloxy-2,5-divinylbezene 10 in good yield (73%).[37]
Soluble 1,3,4-oxadiazole–pyrazole conjugated polymers 11a
and 11b were synthesized by the Pd-catalyzed Heck cou-
pling reaction of 1,3,4-oxadiazole-based pyrazole derivatives
6a and 6b with divinyl compound 10 in 63–71% crude yields
(Scheme 3).[38] After hot filtration and further recrystallization,
the pure yellow wool-like solid products 11a and 11b were
provided in 48–53% yields. The two polymers were soluble in
common organic solvents such as chloroform, dichloromethane,
dimethylformamide (DMF), toluene, tetrahydrofuran (THF),
and xylene, etc. Structural characterization of the polymers was
accomplished by gel permeation chromatography (GPC), FT-
IR, 13C and 1H NMR spectroscopy, and elemental analysis.

344
E.-M. Chang et al.
R
N
OC12H25
ϩ
N
N
OC12H25
O
O
N
N
N
Br
Br
6a R ϭ H, 6b R ϭ OMe
10
R
OC12H25
N
N
Pd(OAC)2, P(o-tolyl)3
NEt3, DMAc
n
O
N
C12H25O
O
N
N
N
11a R ϭ H, 48%, 11b R ϭ OMe, 53%
Scheme 3.
Table 1. Characterization of the soluble 1,3,4-oxadiazole-based conjugated polymers 11a and 11b
Conjugated
polymer
GPC
Mw
Absorbance λmax [nm]
Emission λmax (PL) [nm]
CH2Cl2
Toluene
Film
CH2Cl2
Toluene
Film
11a
11b
3589
3421
340, 416
335, 404
338, 410
330, 397
344, 417
336, 416
541
541
532
529
569
573
1.2
1.0
0.8
0.6
0.4
0.2
0.0
The weight-average molecular weights (Mw) of the new syn-
thetic polymers, as determined by GPC using polystyrene
standards, were in the range of 3400–3500 (Table 1). The pres-
ence of the dodecyloxy side chain[39] and the Heck coupling
polymerization,[40] gave rise to the relatively low molecular
weights of the copolymer. The results are consistent with the
reported literature data.[40,41]
PL, 11a
PL, 11b
UV, 11a
UV, 11b
Optical Properties
The new soluble 1,3,4-oxadiazole–pyrazole conjugated poly-
mers 11a and 11b exhibited very similar absorption spectra as
shown in Table 1 and Figs 1 and 2. They all show two main
strong absorption peaks: one in the visible range at ∼415 nm
and the other in the UV region at ∼340 nm. Compared with that
of PPV that contained 1,3,4-oxadiazole (OX1-PPV, the λmax val-
ues are 328 and 393 nm in THF solution or in a thin film),[29]
the UV absorption peak of the new polymers 11a and 11b is
blue-shifted by 12 nm, whereas the visible absorption peak is
red-shifted by 22 nm as a result of the introduction of the pyra-
zole chromophore. The absorption at 340 nm can be assigned to
the π–π∗ transition of the cross-conjugated oxadiazole segment,
which are the same absorption maximums of the monomers 6a
and 6b.[30] Theidenticalabsorptionmaximumsoftheoxadiazole
units before and after the polymerization imply that, in dilute
solutions, the electronic interactions between the oxadiazole
units and the PPV backbone are rather limited.[38] Apparently,
200
300
400
500
600
700
800
Wavelength [nm]
Fig. 1. The UV-vis and PL spectra of 11a and 11b in CH2Cl2 solution.
the oxadiazole rings are twisted away from the plane of the conju-
gated backbone. The absorption at 403 nm was initially assigned
to the π–π∗ transition of the conjugated polymer backbone.
Figures 1 and 2 show the photoluminescence (PL) spectra
of the new soluble 1,3,4-oxadiazole–pyrazole conjugated poly-
mers 11a and 11b. The polymer exhibited a maximum emission
at ∼540 nm in organic solvent and at ∼570 nm in the thin
film, and this emission maximum is clearly independent of
the excitation wavelengths. Emissions of the 1,3,4-oxadiazole–
pyrazolehybrids[30] at365–375 nmandthe1,3,4-oxadiazoleunit

New Soluble Conjugated Poly(p-phenylenevinylene) Derivatives
345
1.2
Ϫ5eϪ6
Ϫ4eϪ6
Ϫ3eϪ6
Ϫ2eϪ6
Ϫ1eϪ6
0
PL, 11a
PL, 11b
UV, 11a
UV, 11b
1.0
0.8
0.6
0.4
0.2
0.0
1eϪ6
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
200
300
400
500
600
700
800
Potential [V]
Wavelength [nm]
Fig. 4. Cyclic voltammetry of soluble 1,3,4-oxadiazole–pyrazole conju-
gated polymers 11b.
Fig. 2. The UV-vis and PL spectra of 11a and 11b in thin film.
point that was recorded during the second heating (Table 3 and
Fig. 5). Compounds 11a and 11b showed the sameTg (∼150◦C).
We found that the para-methoxy withdrawing group on the N1-
phenyl moiety did not affect the system. The TGA thermograms
of the polymers are summarized in Table 3 and Fig. 6. The sol-
uble 1,3,4-oxadiazole–pyrazole conjugated polymers 11a and
11b were stable up to around ∼275–300◦C in N2. They afforded
a relatively low anaerobic char yield (∼35%) at 800◦C because
of the thermally sensitive alkoxy side groups. Compound 11a
was slightly more thermally stable than 11b, and all its thermal
properties were superior to PPV.
Ϫ3eϪ6
Ϫ2eϪ6
Ϫ1eϪ6
0
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
Electroluminescent Properties
Potential [V]
A double-layer organic light-emitting diode (OLED) device
with a structure of indium tin oxide (ITO)/polythiophene
(PEDOT)/11b/LiF were constructed by successive vapour depo-
sition of the materials under vacuum onto the ITO-coated glass
substrate. The device was tested in air under ordinary labora-
tory conditions and was found to emit blue-greenish emission at
an onset voltage of 9.2V (Fig. 7). An EL maximum at 544 nm
(Fig. 8) was observed for the device and a red shift with a PL
maximum at 573 nm in the film.
Fig. 3. Cyclic voltammetry of soluble 1,3,4-oxadiazole–pyrazole conju-
gated polymers 11a.
at 395 nm were not observed.[29] In summary, the excitation
spectra of the new polymers show almost identical maximums
to their absorption spectra, which indicates an efficient energy
transfer from the oxadiazole moiety to the PPV backbone.
Cyclic Voltammetry Measurements
Conclusions
The electrochemical properties of the new soluble 1,3,4-
oxadiazole–pyrazole conjugated polymers 11a and 11b were
investigated by cyclic voltammetry, as shown in Figs 3 and 4,
and the resulting data are summarized in Table 2. Upon the
anodic sweep, 11a and 11b show reversible oxidation processes.
The bandgap energies of soluble 1,3,4-oxadiazole–pyrazole con-
jugated polymers 11a and 1b are estimated from the onset
wavelength (λonset) of the UV-vis absorption.[12] Compounds
11a and 11b have high lowest unoccupied molecular orbital
(LUMO) values of ∼2.76–2.81 eV and high electron affinities
of 2.76–2.81 eV (Table 2).
Two new soluble polymers that contain 1,3,4-oxadiazole and
pyrazole rings along the main core were synthesized by a Heck
coupling reaction.The polymers were readily soluble in common
organic solvents and had a moderate Tg (∼150◦C) and a good
thermal stability. The electron affinity of new polymers was esti-
mated as 2.76–2.81 eV.The new conjugated polymers are soluble
in common organic solvents for their fully conjugated back-
bone with soluble dedecyloxy side groups. The polymers were
luminescent with PL emission maxima around 530–540 nm in
solution and ∼570 nm in a thin film. Cyclic voltammetry dis-
played that both conjugated polymers had reversible oxidation
and irreversible reduction, making them n-type electrolumines-
cent materials. The weight-average molecular weights of the
new soluble polymers containing pyrazole and 1,3,4-oxadiazole
moieties were in the range of 3400–3500.
Thermal Properties
Thermal and thermomechanical characterization of the polymers
was investigated by differential scanning calorimetry (DSC) and
thermal gravimetric analysis (TGA). The glass-transition tem-
peratures (Tgs) of the polymers were determined by the DSC
method. No phase transitions were recorded during the first and
secondheatingintheDSCexperiments.Theabsenceofamelting
endothermconfirmedtheamorphousnatureofthepolymers.The
Tg was obtained from the onset temperature of the first inflection
Experimental
General Procedure
Sydnones were synthesized according to literature
procedures.[32] All chemicals were reagent grade and used

346
E.-M. Chang et al.
Table 2. Electrochemical properties of soluble 1,3,4-oxadiazole–pyrazole conjugated
polymers 11a and 11b
LUMO, lowest unoccupied molecular orbital; HOMO, highest occupied molecular orbital
A
B
C
E
F
Conjugated
polymers
Eonset
[V]
Eꢀonset
[V]
Ip (EHOMO
)
Eg (bandgap energy)
Ea (ELUMO
)
[eV]D
[eV]D
[eV]D
11a
11b
0.38
0.35
0.57
0.54
5.18
5.15
2.37
2.39
2.81
2.76
AMeasured v. ferrocene/ferrocenium.
BEꢀonset = Eonset + 0.19 eV (measured v. Ag/AgCl).
CIp = −(Eꢀonset + 4.8).
D1 eV = 96.5 kJ mol−1
.
EEg: the bandgap energy estimated from the onset wavelength of the UV-vis absorption and the
equation y = −0.033 × x + 11.141 (x = λonset).
FEa = Ip + Eg.
100
80
60
40
20
Table 3. Tg values and thermal stability of soluble 1,3,4-oxadiazole–
pyrazole conjugated polymers 11a–11b (heating and cooling rate:
15◦C)
11a
11b
A
B
B
Conjugated
polymers
Tg
T1
T10
Char yeildC
[%]
[◦C]
[◦C]
[◦C]
11a
11b
149
150
316
309
409
386
31
39
ATg: glass-temperature determined by the DSC method.
BT1, T10: temperature at which weight losses of 1 and 10%, respectively,
were observed by TGA in N2.
CChar yield at 800◦C by TGA in N2.
0
200
400
600
800
Temperature [°C]
1.0
Fig. 6. TGA thermograms of soluble 1,3,4-oxadiazole–pyrazole conju-
gated polymers 11a and 11b.
11a
11b
0.5
1200
1000
800
600
400
200
0
0.0
Ϫ0.5
Ϫ1.0
Ϫ1.5
Ϫ2.0
0
50
100
150
200
250
300
Temperature [°C]
2
4
6
8
10
12
14
16
18
Fig. 5. DSC thermograms of soluble 1,3,4-oxadiazole–pyrazole conju-
gated polymers 11a and 11b.
Voltage [V]
Fig. 7. I–V curves of ITO/PEDOT/11b/LiF.
as purchased. All reactions were carried out under nitrogen
atmosphere and monitored byTLC analysis. Flash column chro-
matography was carried out on silica gel (230–400 mesh).
Commercially available reagents were used without further
purification unless otherwise noted. Ethyl acetate, dimethyl
sulfoxide (DMSO), diisopropyl ether, hexanes, glacial acetic
acid, methanol, and p-xylene were purchased from Mallinck-
rodt Chemical Co. Dry THF (reagent grade) and palladium
10 wt.-% on carbon were purchased from Aldrich. Ben-
zoyl chloride, 1,4-hydroxybezene, DMAD, hydrazine hydrate,
phosphorus oxychloride, and tetrabutylammonium bromide
were purchased from Acros Chemical Co.
Analytical TLC was performed on pre-coated plates (silica
gel 60 F-254) that were purchased from Merck Inc. Mixtures
of ethyl acetate and hexanes were used as eluants. Purification
by gravity column chromatography was carried out by use of
Merck Reagents Silica Gel 60 (particle size 0.063–0.200 mm,
70–230 mesh ASTM). Infrared (IR) spectra were measured on a

New Soluble Conjugated Poly(p-phenylenevinylene) Derivatives
347
1.8eϪ4
1.6eϪ4
1.4eϪ4
1.2eϪ4
1.0eϪ4
8.0eϪ5
6.0eϪ5
4.0eϪ5
2.0eϪ5
0.0
2H, J 9.0, ArH), 8.28 (s, 1H, pyrazole H). δC (CDCl3, 75 MHz)
52.9, 53.5, 56.5, 115.5, 116.9, 122.7, 132.7, 133.2, 145.0, 160.4,
162.8, 163.0.
Standard Procedure of 1-Phenyl-1H-Pyrazole-3,4-
dicarbohydrazide Derivatives 3a and 3b[44]
A solution of 1-phenyl-1H-pyrazole derivatives (2a and
2b, 1.0 mol equiv.) and hydrazine hydrate (excess amount,
4.0 mol equiv.) was heated in EtOH at reflux overnight.After the
reaction was completed, the reaction mixture was concentrated
under reduced pressure and precipitated by EtOAc (15 mL). The
resulting solution was cooled at −5◦C for 4 h. The wet cake was
filtered off and washed with cold EtOH (10 mL). The wet cake
was dried in a vacuum oven overnight to give the desired product
(3a and 3b) in 74–76% yield.
300
400
500
600
700
800
Wavelength [nm]
Fig. 8. EL spectrum of ITO/PEDOT/11b/LiF.
1-Phenyl-1H-pyrazole-3,4-dicarbohydrazide 3a: δH ([D6]
DMSO, 300 MHz) 4.56 (s, 2H, NH2), 4.57 (s, 2H, NH2), 4.72 (s,
2H, NH2), 7.42 (d, 1H, J 7.12, ArH), 7.54 (t, 2H, J 7.32, ArH),
8.07 (d, 2H, J 7.90, ArH), 9.07 (s, 1H, pyrazole H), 10.35 (s,
1H, NH), 11.15 (s, 1H, NH). δC ([D6]DMSO, 75 MHz) 119.27,
119.60, 128.14, 129.99, 133.17, 138.89, 141.94, 160.51, 161.43.
νmax/cm−1 (KBr) 3395 (br, NH), 1643 (m, C=O).
Bomem Michelson Series FT-IR spectrometer. The wavenum-
bers reported are referenced to the polystyrene (1601 cm−1
)
absorption. Absorption intensities are recorded by the follow-
ing abbreviations: s, strong; m, medium; w, weak. UV-Visible
spectra were measured with a HP 8452A diode-array spec-
trophotometer. PL spectra were obtained on a Perkin–Elmer
fluorescence spectrophotometer (LS 55). 1H NMR spectra
were obtained on a Bruker (300 MHz) spectrometer by use of
[D6]DMSO as solvent. 13C NMR spectra were obtained on a
Bruker (100 MHz) spectrometer with (D)chloroform as solvent.
13C NMR chemical shifts are referenced to the centre of the
CDCl3 triplet (δ 77.0). Multiplicities are recorded by the follow-
ing abbreviations: s, singlet; d, doublet; t, triplet; q, quartet; m,
multiplet; J, coupling constant (Hertz). Elemental analyses were
carried out on a Heraeus CHN-O RAPID element analyzer.
Cyclic voltammetry (CV) and differential pulse voltammetry
(DPV) measurements were performed on a PGSTAT 20 electro-
chemical analyzer. The oxidation and reduction measurements
were carried out in anhydrous CH2Cl2 and THF that contained
0.1 M tetrabutylammonium hexafluorophosphate (TBAPF6) as
the supporting electrolyte at a scan rate of 50 mV s−1.The poten-
tials were measured against anAg/Ag+ (0.01 MAgCl) reference
electrode using ferrocene as the internal standard. The onset
potentials were determined from the intersection of two tangents
drawn at the rising current and background current of the cyclic
voltammogram.[42]
1-(4-Methoxyphenyl)-1H-pyrazole-3,4-dicarbohydrazide3b:
δH ([D6]DMSO, 300 MHz) 3.82 (s, 3H, OCH3), 4.65 (s, 4H,
NH2), 4.71 (s, 2H, NH2), 7.08 (d, 2H, J 9.0, ArH), 7.98 (d, 2H, J
9.0, ArH), 8.96 (s, 1H, pyrazole H), 10.32 (s, 1H, NH), 11.22 (s,
1H, NH). δC ([D6]DMSO, 75 MHz) 55.9, 114.9, 118.9, 121.1,
132.4, 132.8, 141.4, 159.0, 160.6, 161.5.
Standard Procedure of 1H-Pyrazole–Carbohydrazide
Derivatives 5a and 5b[45]
A solution of 1-phenyl-1H-pyrazole-3,4-dicarbohydrazide (3a
and 3b, 0.80 g, 3.08 mmol equiv.) and pyridine (0.1 mol equiv.)
in CH2Cl2 was stirred at room temperature for 10 min. 3-(4-
Bromophenyl)acryloyl chloride 5 (1.58 g, 6.47 mmol equiv.) was
added to the reaction mixture and stirred at room temperature for
8 h. After the reaction was complete, the reaction mixture was
filtered and the solid washed with cool water (10 mL). The wet
cake was dried in a vacuum oven overnight to give the desired
product 5a and 5b in 73–78% yield.
N3ꢀ,N4ꢀ-Bis((E)-3-(4-bromophenyl)acryloyl)-1-phenyl-1H-
pyrazole-3,4-dicarbohydrzide 5a: White crystals, mp 297–
299◦C. δH ([D6]DMSO, 300 MHz) 6.85 (d, 2H, J 9.0), 7.18–7.63
(m, 13H,ArH), 8.17(d, 2H, J9.0), 9.28(s, 1H, pyrazoleH), 10.79
(br, 4H, CONH). δC ([D6]DMSO, 75 MHz) 110.7, 115.0, 118.7,
119.9, 120.2, 123.1, 123.4, 125.8, 130.1, 130.2, 132.4, 134.2,
134.7, 139.0, 139.4, 157.2, 158.3, 163.2, 165.0. νmax/cm−1 (thin
film, NaCl) 3212 (br, NH), 2921, 1620 (m, C=O), 1530, 1458,
1205, 1068, 1032, 969, 830, 811, 687. m/z (FAB) 681 (M + 4,
18), 679 (M + 2, 31), 677 (M, 16), 209 (100). (Found: C 51.2,
H 3.3, N 12.2. Calc. for C29H22Br2N6O4: C 51.4, H 3.3,
N 12.4%.)
Standard Procedure of 1-Phenyl-1H-Pyrazole Derivatives
2a and 2b[43]
A solution of sydnone (1a and 1b, 0.031 mol, 1.0 mol equiv.)
and DMAD (5.2 g, 0.037 mol, 1.2 mol equiv.) was dissolved and
heated in p-xylene solution at reflux overnight. After the reac-
tion was complete, the reaction mixture was concentrated under
reduced pressure and precipitated by EtOH (15 mL). The result-
ingsolutionwascooledat−5◦Cfor4 h.Thewetcakewasfiltered
off and washed with cold EtOH (10 mL). The wet cake was then
dried in a vacuum oven overnight to give the desired product 2a
and 2b in 91–93% yield.
Dimethyl 1-phenyl-1H-pyrazole-3,4-dicarboxylate 2a: δH
([D6]DMSO, 300 MHz)3.77(s, 3H, OCH3), 3.87(s, 3H, OCH3),
7.40–7.51 (m, 3H, ArH), 7.88–7.95 (m, 2H, ArH), 9.16 (s, 1H,
pyrazole H).
N3ꢀ,N4ꢀ-Bis((E)-3-(4-bromophenyl)acryloyl)-1-(4-methoxy-
phenyl)-1H-pyrazole-3,4-dicarbohydrazide 5b: White crystals,
mp 298–300◦C. δH ([D6]DMSO, 300 MHz) 3.79 (s, 3H, OCH3),
6.78 (d, 2H, J 9.0), 7.07 (d, 2H, J 9.0, ArH), 7.44–7.59 (m,
13H, ArH), 8.00 (d, 2H, J 9.0), 9.08 (s, 1H, pyrazole H), 10.69
(br, 4H, CONH). δC ([D6]DMSO, 75 MHz) 55.9, 115.0, 118.8,
121.5, 122.0, 126.1, 130.0, 131.9, 132.0, 134.3, 159.3, 160.0,
162.0, 164.7, 164.9. νmax/cm−1 (thin film, NaCl) 3205 (br, NH),
2921, 1631 (m, C=O), 1535, 1487, 1257, 1205, 1070, 1030,
975, 835, 813, 729. m/z (FAB) 711 (M + 4, 26), 709 (M + 2, 42),
Dimethyl 1-(4-methoxyphenyl)-1H-pyrazole-3,4-dicarboxy-
late 2b: δH (CDCl3, 300 MHz) 3.84 (s, 3H, OCH3), 3.87 (s, 3H,
OCH3), 3.98 (s, 3H, OCH3), 6.98 (d, 2H, J 9.0, ArH), 7.61 (d,

348
E.-M. Chang et al.
707 (M, 37), 209 (100). (Found: C 51.0, H 3.4, N 11.6. Calc. for
C30H24Br2N6O5: C 50.9, H 3.4, N 11.9%.)
2,6-di-tert-butyl-4-methylphenol in DMAc (6 mL) and triethy-
lamine (3 mL) was added (E)-5,5ꢀ-(1-phenyl-1H-pyrazole-3,4-
diyl)bis(2-((E)-4-bromostyryl)-1,3,4-oxadiazole)6a (0.23 mmol,
1.1 equiv.) or (E)-5,5ꢀ-(1-(4-methoxyphenyl)-1H-pyrazole-3,4-
diyl)bis(2-((E)-4-bromostyryl)-1,3,4-oxadiazole)6b(0.23 mmol,
1.1 equiv.). The resulting solution was heated at 130◦C for 50 h
in N2. After the reaction was complete, the reaction mixture was
filtered and added to MeOH (150 mL) to precipitate the crude
product in 63–71% yield. For further purification, the crude
product was dissolved in hot DMF. The resulting hot solution
was quickly filtered through Celite to remove Pd catalyst and
washed with hot DMF (3 mL). The filtrates were added to cold
MeOH (5 mL). The resulting precipitate was filtered off, crys-
tallized from DMF, and dried in a vacuum oven overnight to give
the desired product 11a and 11b as a yellow solid in 48–53%
yield.
Poly(2-(3-(5-(4-(2,5-bis(dodecyloxy)-4-((E)-prop-1-enyl)
styryl)styryl)-1,3,4-oxadiazol-2-yl)-1-phenyl-1H-pyrazol-4-yl)-
5-styryl-1,3,4-oxadiazole) 11a. δH (CDCl3, 300 MHz) 0.79–
1.78 (m, 46H), 3.86–3.94 (m, 4H, OCH2), 6.78–7.82 (m, 8H,
HC=CH and 15H, ArH), 8.72 (s, 1H, pyrazole H). νmax/cm−1
(thin film, NaCl) 2923, 2853, 1636, 1597 (m, C=N), 1497, 1460,
1379, 1250, 1204, 1066, 964, 905, 862, 832. (Found: C 76.2,
H 7.9, N 8.4. Calc. for C65H80N6O4: C 77.3, H 8.0, N 8.3%.)
Poly(2-(3-(5-(4-(2,5-bis(dodecyloxy)-4-((E)-prop-1-enyl)
styryl)styryl)-1,3,4-oxadiazol-2-yl)-1-(4-methoxyphenyl)-1H-
pyrazol-4-yl)-5-styryl-1,3,4-oxadiazole) 11b. δH (CDCl3,
300 MHz) 0.80–1.88 (m, 46H), 3.82–4.03 (m, 4H, OCH2), 6.74–
7.79 (m, 8H, HC=CH and 14H, ArH), 8.61 (s, 1H, pyrazole
H). νmax/cm−1 (thin film, NaCl) 2970, 2921, 1738, 1610, 1595
(m, C=N), 1518, 1420, 1365, 1205, 1066, 964, 897, 831, 809.
(Found: C 75.5, H 7.8, N 8.2. Calc. for C66H82N6O5: C 76.3,
H 8.0, N 8.1%.)
Standard Procedure of Preparation of 1H-Pyrazol-
1,3,4-Oxadiazole Derivatives 6a and 6b[31]
A solution of 1H-pyrazole–carbohydrazide derivatives (5a and
5b, 4.2 mmol, 1.0 mol equiv.) in POCl3 (10 mL) was stirred
at 90◦C overnight. After the reaction was complete, the reac-
tion mixture was added to cold water (10 mL) and neutralized
with NaHCO3 aqueous solution (10 mL) to precipitate the cor-
responding products. The crude product was filtered off and
washed with cold water (5 mL). The wet cake was crystallized
from EtOH and dried in a vacuum oven overnight to give the
desired product 6a and 6b in 89–92% yield.
(E)-5,5ꢀ-(1-Phenyl-1H-pyrazole-3,4-diyl)bis(2-((E)-4-brom-
ostyryl)-1,3,4-oxadiazole) 6a: Yellow crystals, mp 229–231◦C.
δH ([D6]DMSO, 300 MHz) 7.44–8.08 (m, 17H, HC=CH and
ArH), 9.28 (s, 1H, pyrazole H). δC ([D6]DMSO, 75 MHz) 108.3,
110.9, 111.0, 120.0, 123.7, 123.8, 128.9, 130.1, 130.2, 131.4,
131.9, 132.2, 132.5, 134.1, 136.1, 136.5, 138.2, 138.6, 138.8,
157.5, 157.7, 164.3, 164.8. νmax/cm−1 (thin film, NaCl) 2922,
1636, 1602 (m, C=N), 1550, 1521, 1201, 1072, 1008, 962, 859,
808, 687. m/z (FAB) 645 (M + 4, 19), 643 (M + 2, 28), 641
(M, 19), 211 (100). (Found: C 54.1, H 2.9, N 12.8. Calc. for
C28H18Br2N6O2: C 54.2, H 2.8, N 13.1%.)
(E)-5,5ꢀ-(1-(4-Methoxyphenyl)-1H-pyrazole-3,4-diyl)bis(2-
((E)-4-bromostyryl)-1,3,4-oxadiazole) 6b: Yellow crystals, mp
262–264◦C. δH ([D6]DMSO, 300 MHz) 3.84 (s, 3H, OCH3),
7.15–8.97 (m, 16H, HC=CH and Ar H), 9.60 (s, 1H, pyrazole
H). δC ([D6]DMSO, 75 MHz) 56.0, 108.7, 111.0, 115.2, 115.8,
119.2, 121.5, 121.7, 126.0, 129.9, 130.1, 130.3, 132.2, 134.1,
136.0, 136.4, 138.0, 138.2, 138.6, 157.6, 158.5, 159.6, 164.8,
165.3. νmax/cm−1 (thin film, NaCl) 2925, 1643, 1605 (m, C=N),
1516, 1248, 1203, 1068, 1005, 960, 835, 809. m/z (FAB) 675
(M + 4, 25), 673 (M + 2, 42), 671 (M, 29), 391 (100). (Found:
C 53.4, H 3.0, N 12.5. Calc. for C30H20Br2N6O3: C 53.6, H 3.0,
N 12.5%.)
Acknowledgements
We are grateful to the National Science Council of the Republic of China
for financial support.
1,4-Bis(dodecyloxy)benzene 8[36]
Mp 70–71◦C. δH (CDCl3, 300 MHz) 0.86–2.01 (t, 6H, J 6.0),
1.27–1.44 (m, 36H), 1.70–1.79 (m, 4H), 3.87–3.92 (t, 4H, J
7.5), 6.82 (s, 4H).
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