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

Article abstract of DOI:10.1071/CH08344

New soluble poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole and pyrazole rings along the main chain were synthesized by Heck coupling. The new conjugated polymers are soluble in common organic solvents as a result of the fully conjugated backb

Full text of DOI:10.1071/CH08344

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CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2009, 62, 1355–1362
Synthesis and Characterization of Soluble Conjugated
Poly(p-phenylenevinylene) Derivatives Constituted of
Alternating Pyrazole and 1,3,4-Oxadiazole Moieties
En-Ming Chang,B Shin-Lin Huang,C Cheng-Tien Lee,B Hui-Chang Lin,A
Chun-Yen Chen,B Yu-Ying Huang,A Shao-Kai Lin,C and Fung Fuh WongA,D
AGraduate Institute of Pharmaceutical Chemistry, China Medical University, Taichung,
Taiwan 40402, Republic of China.
BDepartment of Chemistry, National Cheng Kung University, Tainan, Taiwan 70101,
Republic of China.
CSustainable Environment Research Center, National Cheng Kung University,
Tainan City, Taiwan 709, Republic of China.
DCorresponding author. Email: wongfungfuh@yahoo.com.tw
New soluble poly(p-phenylenevinylene) derivatives with 1,3,4-oxadiazole and pyrazole rings along the main chain were
synthesized by Heck coupling.The new conjugated polymers are soluble in common organic solvents as a result of the fully
conjugated backbone with dodecyloxy side groups. The polymers show relatively high glass-transition temperatures (up to
160◦C) and good satisfactory thermal stability. Solutions of the polymers emit blue-greenish light with photoluminescence
(PL) emission maxima around 490–500 nm. The PL spectrum of the polymer’s thin films, with a maximum at 515 nm,
shows a red-shift (∼20 nm), with respect to the solution spectrum. Cyclic voltammetry reveals that both conjugated
polymers have reversible oxidation and irreversible reduction, making them n-type electroluminescent materials. The
electron affinity of the new polymers was estimated as 2.73–2.74 eV. The weight-average molecular weights (Mw) of the
new soluble polymers were in the range of 4790–4950.
Manuscript received: 12 August 2008.
Manuscript accepted: 10 February 2009.
R
Introduction
Soluble π-conjugated electroluminescent polymers have
attracted much attention as the active component in light-
emitting diodes,[1–4] solid-state lasers,[5,6] and transistors after
the discovery of light emission from poly(p-phenylenevinylene)
(PPV).[7–10] Typically, conjugated polymers such as PPV,
poly(thiophene) (PT), and their derivatives tend to p-type, that
is, they favour hole transport.[11,12] The recent interest in soluble
π-conjugated polymers with good electron-injection capability
was enthusiastically investigated, particularly in the conju-
gated polymers that contain electron-withdrawing units in the
main chain or at side groups to improve electron-transport
capability.[13–15]
OC12H25
N
N
O
N
n
O
N
C12H25
O
N
N
R ϭ H, OMe
Fig. 1. The new soluble poly(p-phenylenevinylene) derivatives with
In a previous study, we demonstrated that multiple 1,3,4-
oxadiazole units can promote thermal stability and electrolumi-
nescent properties when they are introduced into the conjugated
main core of pyrazole derivatives.[16] As a result, aromatic mul-
tiple 1,3,4-oxadiazole-based conjugated polymers have been
developed as promising candidates for light-emitting devices
because of their thermal, hydrolytic, and photo-stability,[17–20]
electron affinity, and hole blocking ability in this work.[12,21,22]
1,3,4-Oxadiazole-based heterocyclic conjugated polymers have
also been enthusiastically investigated to improve electron injec-
tion, transport properties, and confer rigidity, for example, 1,3,4-
oxadiazole–carbazole,[23] and 1,3,4-oxadiazole–pyridine.[24]
1,3,4-oxadiazole and pyrazole rings along the main chain.
Because the chromophore pyrazole can play an assistant
role in controlling the fundamental electroluminescent pro-
cess, 1,3,4-oxadiazole-based pyrazole derivatives are revealed
as efficient blue-greenish electroluminescent materials.[16] As
a result, we established the introduction of pyrazole and multi-
ple 1,3,4-oxadiazole units into the conjugated polymer’s main
chain to improve the electron-transporting properties. This new
soluble PPV-based conjugated polymer with 1,3,4-oxadiazole
and pyrazole rings in the backbone (Fig. 1) was successfully
© CSIRO 2009
10.1071/CH08344
0004-9425/09/101355

1356
E.-M. Chang et al.
MeOOC
MeOOC
N
ϩ
N
MeOOC
COOMe
O
N
R
R
Ϫ
O
Toluene
N
1a R ϭ H, 1b R ϭ OMe
2a R ϭ H, 93%, 2b R ϭ OMe, 91%
H2NHNOC
H2NHNOC
NH2NH2, H2O
EtOH
p-BrPhCOCl
N
N
R
Pyridine, CH2Cl2
3a R ϭ H, 74%, 3b R ϭ OMe, 76%
p-BrPh
O
N
N
p-BrPhOCHNHNOC
p-BrPhOCHNHNOC
POCl3
R
N
R
N
N
N
N
N
O
p-BrPh
5a R ϭ H, 90%
4a R ϭ H, 83%
4b R ϭ OMe, 78%
5b R ϭ OMe, 92%
Scheme 1.
OC12H25
OC12H25
Br
OH
C12H25Br
Br2, AlCl3
CH2Cl2
t-Bu4NBr, KOH
Br
OC12H25
OC12H25
OH
6
7
8
OC12H25
SnBu3
PPh3, toluene
OC12H25
9
Scheme 2.
synthesized by 1,3-dipolar addition,[16] dehydration,[25] and
Heck coupling.[16]
This 1,3-dipolar cyclization has proved to be an efficient
and economical way to generate pyrazole derivatives. Treating
1-aryl-1H-pyrazole-3,4-dicarboxylate (2a,2b) with hydrazine
hydrate at reflux afforded the corresponding dihydrazide prod-
uct (3a,3b) in good yield (74–76%) according to published
reports.[27] Dihydrazide compounds (3a,3b) reacted with ben-
zoyl chloride in CH2Cl2 at room temperature for 2 to 3 h to give
the corresponding bis(trihydrazide) products (4a,4b) in 78–83%
yields. These compounds (4a,4b) were dehydration cyclized to
form the 1,3,4-oxadiazole-based pyrazole derivatives (5a,5b) in
90–92% yield in the presence of POCl3.[25]
Result and Discussion
Synthesis
The synthetic route is shown in Scheme 1 for the generation
of two 1,3,4-oxadiazole-based pyrazole monomer derivatives
(5a,5b). Sydnone compounds (1a,1b) were prepared by fol-
lowing the literature procedure developed in our laboratory.[26]
Sydnone compounds (1a,1b) with various substituents in the N1-
phenyl ring, including para-H, and -OMe groups were applied
to dimethyl acetylenedicaboxylate (DMAD) to give the
corresponding dimethyl 1-aryl-1H-pyrazole-3,4-dicarboxylate
(2a,2b) as a white solid in almost quantitative yield (91–93%).
The synthetic route of 1,4-didodecyloxy-2,5-divinylbezene 9
is outlined in Scheme 2. 1,4-Dibromo-2,5-didodecyloxybezene
8 was easily synthesized in two steps with a total yield of 64%
using 1,4-hydroxybezene 6 as starting material following the

Synthesis of Conjugated Poly(p-phenylenevinylene) Derivatives
p-BrPh
1357
OC12H25
O
N
Pd(OAC)2, P(o-tolyl)3
N
ϩ
R
N
NEt3, DMAc
N
N
N
OC12H25
O
p-BrPh
5a R ϭ H, 5b R ϭ OMe
9
R
OC12H25
N
N
O
N
n
O
N
C12H25
O
N
N
10a R ϭ H, 48%, 10b R ϭ OMe, 53%
Scheme 3.
Table 1. Characterization of the soluble 1,3,4-oxadiazole-based conjugated polymers 10a and 10b
GPC Absorbance λmax (UV-vis) [nm] Emission λmax (PL) [nm]
Conjugated
polymer
Mn [kDa]
Pd
CH2Cl2
Toluene
Film
CH2Cl2
Toluene
Film
10a
10b
4949
4790
2.04
2.94
306, 404
308, 415
300, 393
300, 400
302, 408
303, 410
498
499
493
492
515
513
previously reported procedure.[28] Eventually, the Stille cou-
pling of 1,4-dibromo-2,5-didodecyloxybezene 8 with 2.2 equiv.
of vinyltin reagent was performed to give the coupled product
1,4-didodecyloxy-2,5-divinylbezene 9 in good yield (73%).[29]
Soluble 1,3,4-oxadiazole–pyrazole conjugated polymers
(10a,10b) were synthesized by the Pd-catalyzed Heck coupling
reaction of 1,3,4-oxadiazole-based pyrazole derivatives 5a,5b
with divinyl compound 9 in 48–53% yield (see Scheme 3).[30]
The two polymers are soluble in common organic solvents
such as chloroform, dichloromethane, N,N-dimethylformamide
(DMF), toluene, tetrahydrofuran (THF), and xylene, etc. They
are all yellow-coloured wool-like solids. Structural charac-
terization of the polymers was accomplished by FT-IR, 13C
NMR, and 1H NMR spectroscopy, and elemental analysis. The
weight-average molecular weights (Mn) of the new synthetic
polymers, as determined by gel permeation chromatography
using polystyrene as a standard, were in the range of 4790–4950
(see Table 1). According to the presence of the dodecyloxy side
chain[31] and the Heck coupling polymerization,[32] relatively
low molecular weight copolymers were provided. The results
are consistent with the reported literature data.[32,33]
1.2
1.0
0.8
0.6
0.4
0.2
0.0
PL, 10a
PL, 10b
UV, 10a
UV, 10b
200
300
400
500
600
700
800
Wavelength [nm]
Fig. 2. The UV-vis and PL spectra of 10a and 10b in CH2Cl2 solution.
other in the UV region at 305 nm. Compared with that of poly
(p-phenylenevinylene) that contains 1,3,4-oxadiazole (OX1-
PPV, the λmax values are 328 and 393 nm in THF solution or
in a thin film, respectively),[24] the UV absorption peak of the
new polymers (10a,10b) is blue-shifted by 23 nm, whereas the
visible absorption peak is red-shifted by 10 nm. The absorption
at 305 nm can be assigned to the π–π* transition of the cross-
conjugated oxadiazole segment, which is confirmed by the same
Optical Properties
The new soluble 1,3,4-oxadiazole–pyrazole conjugated poly-
mers (10a,10b) exhibit very similar absorption spectra as shown
in Table 1 and Figs 2 and 3. They all show two main strong
absorption peaks: one in the visible range at ∼403 nm and the

1358
E.-M. Chang et al.
Ϫ1e-6
Ϫ8e-7
Ϫ6e-7
Ϫ4e-7
Ϫ2e-7
0
1.2
PL, 10a
PL, 10b
UV, 10a
UV, 10b
1.0
0.8
0.6
0.4
0.2
2e-7
0.0
0.4
0.8
0.6
Potential [V]
1.0
1.2
1.4
0.2
Ϫ0.2
200
300
400
500
600
700
800
Fig. 4. Cyclic voltammetry of soluble 1,3,4-oxadiazole–pyrazole conju-
gated polymers of 10a.
Wavelength [nm]
Fig. 3. The UV-vis and PL spectra of 10a and 10b in a thin film.
Ϫ4e-6
Ϫ3e-6
Ϫ2e-6
Ϫ1e-6
0
absorption maximums of the monomer (5a,5b).[16] The identi-
cal absorption maximums of the oxadiazole units before and
after the polymerization imply that, in dilute solution, the elec-
tronic interactions between the oxadiazole units and the PPV
backbone are rather limited.[23] Apparently, the oxadiazole rings
are twisted away from the plane of the conjugated backbone.
The absorption at 403 nm was initially assigned to the π–π*
transition of the conjugated polymer backbone.
Figs 2 and 3 show the photoluminescence (PL) spectra of
the new soluble 1,3,4-oxadiazole–pyrazole conjugated polymers
(10a,10b).The polymer exhibits a maximum emission at 500 nm
in organic solvent or the thin film, and this emission maximum
is clearly independent of the excitation wavelengths. Emissions
of the 1,3,4-oxadiazole–pyrazole hybrids[16] at 365–375 nm and
the 1,3,4-oxadiazole unit at 395 nm are not observed.[24] How-
ever, the absorption spectra of the new polymers show almost
identical maximums to their absorption spectra, which indicates
the existence of efficient energy transfer from the oxadiazole
moiety to the PPV backbone.
1e-6
0.2
0.4
0.6
Potential [V]
0.8
1.0
1.2
1.4
Fig. 5. Cyclic voltammetry of soluble 1,3,4-oxadiazole–pyrazole conju-
gated polymers of 10b.
than 10b (167◦C), which was attributed to the presence of the
para-methoxy withdrawing group in the N1-phenyl ring. The
TGA thermograms of the polymers are summarized in Table 3
and Fig. 7. The soluble 1,3,4-oxadiazole–pyrazole conjugated
polymers (10a,10b) were stable up to ∼250–260◦C in N2. They
afforded a relatively low anaerobic char yield (∼35%) at 800◦C
because of the thermally sensitive alkoxy side groups. Com-
pound 10b was slightly more thermally stable than 10a, and all
its thermal properties were superior to PPV.
Cyclic Voltammetry Measurements
The electrochemical properties of the new soluble 1,3,4-
oxadiazole–pyrazole conjugated polymers (10a,10b) were
investigated by cyclic voltammetry, as shown in Figs 4 and 5, and
the resulting data are summarized in Table 2. Upon the anodic
sweep, 10a and 10b show reversible oxidation processes and
irreversible reduction. Compounds 10a and 10b were used as
examples and are shown in Figs 4 and 5. The bandgap ener-
gies of soluble 1,3,4-oxadiazole–pyrazole conjugated polymers
(10a,10b) are estimated from the onset wavelength (λonset) of
the UV-vis absorption.[12] Compounds 10a,10b have high low-
est unoccupied molecular orbital values of ∼2.73 eV and high
electron affinities of ∼2.43 eV.
Electroluminescent Properties
A double-layer organic light-emitting diode device with a struc-
ture of indium tin-oxide (ITO)/polythiophene/1,3,4-oxadiazole–
pyrazole conjugated polymers (10a)/LiF was constructed by
successive vapour deposition of the materials under vacuum
onto the ITO-coated glass substrate. The device was tested in
air under ordinary laboratory conditions and was found to emit
a blue-greenish emission at 5.9V onset voltage (see Fig. 8).
The red-shifted electroluminescence maximum of the device at
503 nm (see Fig. 9) was observed with a PL maximum at 515 nm
in the film.
Thermal Properties
Thermal and thermomechanical characterization of the polymers
was carried out by differential scanning calorimetry (DSC) and
thermogravimetric 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
point that was recorded during the second heating (see Table 3
and Fig. 6). Compound 10a showed a slightly lower Tg (164◦C)
Conclusions
Two new soluble polymers that contain 1,3,4-oxadiazole and
pyrazole rings along the main chain have been synthesized by
Heck coupling. The polymers are readily soluble in common
organic solvents and had moderateTg (164 and 167◦C) and have
a good satisfactory thermal stability. Compound 10a has a lower
Tg and a higher electron affinity than 10b. The electron affinity
of the new polymers was estimated as 2.73–2.74 eV. The new

Synthesis of Conjugated Poly(p-phenylenevinylene) Derivatives
1359
Table 2. Electrochemical properties of soluble 1,3,4-oxadiazole–pyrazole conjugated polymers 10a and 10b
HOMO, highest occupied molecular orbitals; LUMO, lowest unoccupied molecular orbital
A
B
C,D
D,E
F
Conjugated polymers
Eonset [V]
Eꢀonset [V]
Ip
EHOMO [eV]
Eg
bandgap energy [eV]
Ea ELUMO [eV]
10a
10b
0.41
0.36
0.60
0.55
5.21
5.16
2.47
2.43
2.74
2.73
AMeasured versus ferrocene/ferrocenium.
BEꢀonset = Eonset + 0.19 eV (measured versus Ag/AgCl).
CIp = −(Eꢀonset + 4.8).
D1 eV = 96.5 kJ mol−1
.
EEg, the bandgap energy estimated from the onset wavelength of UV-vis absorption and the equation Y = −0.033 × X + 11.141 (X = λonset).
FEa = Ip + Eg.
1200
1000
800
600
400
200
0
Table 3. Tg values and thermal stability of soluble 1,3,4-oxadiazole–
pyrazole conjugated polymers 10a and 10b (heating and cooling rate:
15◦C min−1
)
A
Conjugated polymers
Tg [◦C]
In N2
B
B
C
T1 [◦C]
T10 [◦C]
Yc [%]
10a
10b
164
168
264
257
389
346
34
36
ATg, glass-temperature determined by the differential scanning calorimetry
method.
BT1, T10, temperature at which weight losses of 1 and 10%, respectively,
were observed by thermogravimetric analysis.
CYc, char yield at 800◦C by TGA.
2
4
6
8
10
12
14
16
Voltage [V]
Fig. 8. I–V curves of ITO/PEDOT/10a/LiF.
10a
10b
4e-4
3e-4
2e-4
1e-4
0
0
50
100
150
200
250
300
Temperature [ЊC]
Fig. 6. Differential scanning calorimetry thermograms of soluble
1,3,4-oxadiazole–pyrazole conjugated polymers 10a and 10b.
300
400
500
600
700
800
Wavelength [nm]
Fig. 9. EL spectrum of ITO/PEDOT/10a/LiF.
100
10a
10b
conjugated polymers are soluble in common organic solvents
according to the fully conjugated backbone with solubilizing
dedecyloxy side groups. The polymers were luminescent with
PL emission maxima around 490–515 nm in solution or in a thin
film. Cyclic voltammetry displayed that both conjugated poly-
mers had reversible reduction and irreversible oxidation, making
them n-type electroluminescent materials. The weight-average
molecular weights (Mw) of the new soluble polymers were in
the range of 4790–4950.
80
60
40
0
200
400
600
800
Experimental
Temperature [ЊC]
General Procedure
Sydnones were synthesized according to literature
procedures.[26] All chemicals were reagent grade and used
Fig. 7. Thermogravimetric analysis thermograms of soluble 1,3,4-
oxadiazole–pyrazole conjugated polymers 10a and 10b.

1360
E.-M. Chang et al.
as purchased. All reactions were carried out under a nitro-
gen atmosphere and monitored by TLC analysis. Flash column
chromatography was carried out on silica gel (230–400 mesh).
Commercially available reagents were used without further
purification unless otherwise noted. Ethyl acetate, dimethyl sul-
foxide, diisopropyl ether, hexanes, glacid acetic acid, methanol,
and p-xylene were purchased from Mallinckrodt Chemical
Co. Dry THF (reagent grade) and 10 wt.-% palladium on
carbon were purchased from Aldrich. Benzoyl chloride, 1,4-
dihydroxybenzene, dimethyl acetylenedicaboxylate, hydrazine
hydrate, phosphorus oxychloride, and tetrabutylammonium bro-
mide were purchased from Acros Chemical Co.
Dimethyl 1-Phenyl-1H-pyrazole-3,4-dicarboxylate (2a)
δH 3.77 (s, 3H, OCH3), 3.87 (s, 3H, OCH3), 7.40–7.51 (m,
3H, Ar-H), 7.88–7.95 (m, 2H, Ar-H), 9.16 (s, 1H, pyrazole-H).
Dimethyl 1-(4-Methoxyphenyl)-1H-pyrazole-3,4-
dicarboxylate (2b)
δH 3.84 (s, 3H, OCH3), 3.87 (s, 3H, OCH3), 3.98 (s, 3H,
OCH3), 6.98 (d, 2H, J 9.0, Ar-H), 7.61 (d, 2H, J 9.0, Ar-H),
8.28 (s, 1H, pyrazole-H). δC 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 Synthesis Procedure of 1-Phenyl-1H-pyrazole-
3,4-dicarbohydrazide Derivatives 3a and 3b[27]
Analytical TLC was performed on precoated plates (silica
gel 60 F-254) 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 Bomem Michelson Series FT-IR spectrometer. The wavenum-
bers reported are referenced to the polystyrene absorption at
1601 cm−1. Absorption intensities are recorded by the follow-
ing abbreviations: s, strong; m, medium; w, weak. UV-Vis
spectra were measured with a HP 8452A diode-array spec-
trophotometer. PL spectra were obtained on a Perkin–Elmer
fluorescence spectrophotometer (LS 55). Proton NMR spectra
were obtained on a Bruker (300 MHz) spectrometer by use of
(D6)DMSO as solvent. Carbon-13 NMR spectra were obtained
on a Bruker (100 MHz) spectrometer by use of D-chloroform as
solvent. Carbon-13 chemical shifts are referenced to the cen-
tre of the CDCl3 triplet (δ 77.0). Multiplicities are recorded
by the following 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.
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 solution at reflux overnight.
After the reaction was complete, the reaction mixture was con-
centrated 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 then dried in a vacuum oven overnight to give
the desired product (3a and 3b) in 74–76% yield.
1-Phenyl-1H-pyrazole-3,4-dicarbohydrazide (3a)
δH 4.56 (s, 2H, NH2), 4.57 (s, 2H, NH2), 4.72 (s, 2H, NH2),
7.42 (d, 1H, J 7.12,Ar-H), 7.54 (t, 2H, J 7.32,Ar-H), 8.07 (d, 2H,
J 7.90,Ar-H), 9.07 (s, 1H, pyrazole-H), 10.35 (s, 1H, NH), 11.15
(s, 1H, NH). δC ((D6)DMSO) 119.27, 119.60, 128.14, 129.99,
133.17, 138.89, 141.94, 160.51, 161.43. νmax (KBr)/cm−1 3395
(br, NH), 1643 (m, C=O).
1-(4-Methoxyphenyl)-1H-pyrazole-3,4-
dicarbohydrazide (3b)
δH 3.82 (s, 3H, OCH3), 4.65 (s, 4H, NH2), 4.71 (s, 2H, NH2),
7.08 (d, 2H, J 9.0, Ar-H), 7.98 (d, 2H, J 9.0, Ar-H), 8.96 (s,
1H, pyrazole-H), 10.32 (s, 1H, NH), 11.22 (s, 1H, NH). δC
((D6)DMSO) 55.9, 114.9, 118.9, 121.1, 132.4, 132.8, 141.4,
159.0, 160.6, 161.5.
Cyclic Voltammetry Measurements
Cyclic voltammetry and differential pulse voltammetry mea-
surements were performed on a PGSTAT 20 electrochemical
analyzer. The oxidation and reduction measurements were car-
ried 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 a Ag/Ag+ (0.01 M AgCl) 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.[34]
Standard Synthesis Procedure of 1H-Pyrazole-
carbohydrazide Derivatives 4a and 4b
A
solution of 1-phenyl-1H-pyrazole-3,4-dicarbohydrazide
(3a,3b, 2.0 g, 1.0 mol equiv.) and pyridine (0.1 mol equiv.) was
stirred in CH2Cl2 at room temperature for 10 min. Benzoyl chlo-
ride (2.7 g, 2.5 mol equiv.) was added to the reaction mixture and
stirred at room temperature for 8 h. After the reaction was com-
plete, the reaction mixture was filtered and the solid obtained
washed with cool water (10 mL). The wet cake was dried in a
vacuum oven overnight to give the desired product (4a,4b) in
78–83% yield.
Standard Synthesis Procedure of 1-Phenyl-1H-pyrazole
Derivatives 2a and 2b
N3ꢀ,N4ꢀ-Bis(4-bromophenyl)-1-phenyl-1H-pyrazole-
3,4-dicarbohydrazide (4a)
A solution of sydnone (1a and 1b, 0.031 mol, 1.0 mol equiv.) and
dimethylacetylenedicaboxylate(5.2 g, 0.037 mol, 1.2 molequiv.)
was dissolved and heated in a p-xylene solution at reflux
overnight. After the reaction was completed, the reaction mix-
ture was concentrated under reduced pressure and precipated
by EtOH (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 then dried in a vacuum oven
overnight to give the desired product (2a and 2b) in 91–93%
yield.
Mp 311–313◦C. δH 7.12 (d, 2H, Ar-H), 7.45–8.21 (m,
11H, Ar-H), 9.15 (s, 1H, pyrazole-H), 10.72 (br, 4H, NH),
10.79 (s, 1H, NH), 11.32 (s, 1H, NH), 11.92 (s, 1H, NH). δC
((D6)DMSO) 115.8, 118.3, 120.6, 120.7, 123.4, 127.4, 127.5,
130.8, 131.1, 132.4, 135.8, 159.1, 159.7, 165.0, 165.3. νmax (thin
film, NaCl)/cm−1 3208 (b, NH), 1631 (m, C=O), 1520, 1473,
1261, 1111, 1010, 839, 763, 738, 691. m/z (FABMS) 629 (24%)
[M + 2], 627 (49) [M + 1], 626 (25) [M], 191 (100). (Found:
C 47.98, H 2.94, N 13.39. Calc. for C25H18Br2N6O4: C 47.95,
H 2.90, N 13.42%.)

Synthesis of Conjugated Poly(p-phenylenevinylene) Derivatives
1361
N3ꢀ,N4ꢀ-Bis(4-bromobenzoyl)-1-(4-methoxyphenyl)-
1H-pyrazole-3,4-dicarbohydrazide (4b)
(m, 4H), 5.24–5.27 (dd, 2H, J 5.9 and 0.8), 5.71–5.75 (dd, 2H, J
9.8 and 0.8), 6.99 (s, 2H), 7.02–7.07 (dd, 2H, J 6.7 and 4.0).
(Found: C 81.90, H 11.83. Calc. for C34H58O2: C 81.85, H
11.77%.)
Mp 316–318◦C. δH 3.80 (s, 3H, OCH3), 7.08 (d, 2H, J 9.0,
Ar-H), 7.58–8.02 (m, 8H, Ar-H), 8.10 (d, 2H, J 9.0, Ar-H), 9.09
(s, 1H, pyrazole-H), 10.84 (br, 4H, NH), 10.72 (s, 1H, NH), 11.14
(s, 1H, NH), 11.90 (s, 1H, NH). δC ((D6)DMSO) 55.9, 115.0,
118.8, 121.5, 126.0, 126.1, 130.0, 131.9, 132.0, 132.3, 134.4,
159.3, 160.0, 162.0, 164.7, 164.9. νmax (thin film, NaCl)/cm−1
3208 (b, NH), 1620 (m, C=O), 1448, 1258, 1174, 1066, 1009,
965, 831, 743, 708. m/z (FABMS) 659 (19%) [M + 2], 657 (35)
[M + 1], 656 (20) [M], 183 (100). (Found: C 47.54, H 3.06, N
12.82. Calc. for C26H20Br2N6O5: C 47.58, H 3.07, N 12.81%.)
Standard Synthetic Procedure for the Preparation of
1H-Pyrazol-1,3,4-oxadiazole Derivatives 10a and 10b[29]
A solution of 1,4-bis(dodecyloxy)-2,5-divinylbenzene (9, 0.1 g,
0.2 mmol, 1.0 equiv.), Pd(PPh3)4, and a few crystals 2,6,-di-
tert-butyl-4-methylphenol in 6 mL of DMAc and 3 mL of tri-
ethylamine was added 5,5ꢀ-(1-phenyl-1H-pyrazole-3,4-diyl)bis
(2-(4-bromophenyl)-1,3,4-oxadiazole)
(5a,
0.21 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
filtrated and MeOH (150 mL) added to precipitate the crude
product in 63–72% yield. For further purification, the crude
product was dissolved in hot DMF. The hot resulting solution
was quickly filtered through Celite to remove the Pd catalyst
and washed with hot DMF (3 mL). The filtrates were added to
cold MeOH (5 mL). The resulting precipitate was filtered, crys-
tallized from DMF, and dried in a vacuum oven overnight to give
the desired product 10a and 10b as a yellow solid in 48–53%
yield.
Standard Synthetic Procedure of the Preparation of
1H-Pyrazol-1,3,4-oxadiazole Derivatives 5a and 5b[25]
A solution of 1H-pyrazole-carbohydrazide derivatives (4a,4b,
4.2 mmol, 1.0 mol equiv.) in POCl3 (10 mL) was stirred at 90◦C
for overnight. After the reaction was complete, the reaction mix-
ture was added to cold water (10 mL) and neutralized with
a 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 (5a,5b) in 90–92% yield.
Poly(2-(3-(5-(4-(2,5-bis(dodecyloxy)-4-((E)-prop-1-
enyl)styryl)phenyl)-1,3,4-oxadiazol-2-yl)-1-phenyl-1H-
pyrazol-4-yl)-5-phenyl-1,3,4-oxadiazole) (10a)
5,5ꢀ-(1-Phenyl-1H-pyrazole-3,4-diyl)bis(2-(4-
bromophenyl)-1,3,4-oxadiazole) (5a)
Mp 238–240◦C. δH 7.49–8.09 (m, 13H, Ar-H), 9.66 (s, 1H,
pyrazole-H). δC ((D6)DMSO) 118.5, 118.7, 120.1, 124.5, 124.8,
127.6, 130.5, 131.3, 131.4, 133.9, 134.2, 135.0, 138.5, 138.7,
157.3, 157.7, 163.9, 164.3. νmax (thin film, NaCl)/cm−1 3208
(b, NH), 1610, 1597, 1530, 1496, 1479, 1226, 1069, 1010, 964,
832, 757, 688. m/z (FABMS) 593 (39%) [M + 2], 592 (60)
[M + 1], 591 (38) [M], 289 (100). (Found: C 50.85, H 2.40, N
14.21. Calc. for C25H14Br2N6O2: C 50.87, H 2.39, N 14.24%.)
δH (CDCl3) 0.90–1.74 (m, 46H), 3.78–3.95 (m, 4H, OCH2),
6.73–8.23 (m, 19H, Ar-H and HC=CH), 8.75 (s, 1H, pyrazole-
H). νmax (thin film, NaCl)/cm−1 2920, 2851, 1656, 1598, 1492,
1258, 1202, 1049, 965, 892, 833. (Found: C 75.98, H 7.87, N
8.57. Calc. for C61H76N6O4: C 76.53, H 8.00, N 8.78%.)
Poly(2-(3-(5-(4-(2,5-bis(dodecyloxy)-4-((E)-prop-
1-enyl)styryl)phenyl)-1,3,4-oxadiazol-2-yl)-1-(4-
methoxyphenyl)-1H-pyrazol-4-yl)-5-phenyl-
1,3,4-oxadiazole) (10b)
2-Phenyl-5-(4-(5-phenyl-1,3,4-oxadiazol-2-yl)-1-p-tolyl-
1H-pyrazol-3-yl)-1,3,4-oxadiazole (5b)
δH (CDCl3) 0.79–1.77 (m, 46H), 3.80–3.97 (m, 4H, OCH2),
3.89 (s, 3H, OCH3), 6.88–8.12 (m, 18H, Ar-H and HC=CH),
8.65 (s, 1H, pyrazole-H). νmax (thin film, NaCl)/cm−1 2923,
1670, 1596, 1510, 1496, 1394, 1250, 1205, 1067, 965, 892, 831.
(Found:C73.87, H7.52, N8.40. Calc. forC62H78N6O5:C76.42,
H 7.96, N 8.51%.)
Mp 238–400◦C. δH 7.49–8.09 (m, 13H, Ar-H), 9.66 (s, 1H,
pyrazole-H). δC ((D6)DMSO) 109.4, 118.5, 118.7, 120.1, 124.5,
124.8, 127.6, 130.5, 161.3, 131.4, 133.9, 134.2, 135.0, 138.5,
138.7, 157.3, 157.7, 163.9, 164.3. νmax (thin film, NaCl)/cm−1
1610, 1597, 1530, 1496, 1479, 1233, 1069, 1010, 964, 832, 757,
688. m/z (FABMS) 593 (38) [M + 2], 592 (59) [M + 1], 590
(38) [M], 289 (100). (Found: C 50.85, H 2.40, N 14.20. Calc. for
C25H14Br2N6O2: C 50.87, H 2.39, N 14.24%.)
Acknowledgements
We are grateful the National Science Council of Republic of China for finan-
cial support.We also appreciate Professor Mou-YungYeh for his illuminating
discussion and helpful assistance in preparing this manuscript.
1,4-Bis(dodecyloxy)benzene (7)[28]
Mp 70–71◦C. δH (CDCl3) 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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