New synthesis of highly potential efficient bluish-green electroluminescent materials based on 1,3,4-oxadiazole-triazolopyridinone-carbazole derivatives for single-layer devices

Article abstract of DOI:10.1002/hc.20201

New potential bluish-green electroluminescent materials of 1,3,4-oxadiazole-triazolopyridin-one-carbazole derivatives were synthesized and characterized for single-layer devices. Carbazole, pyridine, and triazolopyridinone were completely introduced into 1,3,4-oxadiazole skeletal to play assistant roles in controlling fundamental photolytic process due to the electron-donating nature, excellent photoconductivity, and flexible structure properties. Following the spectroscopic studies and the measurements of cyclic voltammogram, 1,3,4-oxadiazole-triazolopyridinone-carbazole derivatives were highly efficient bluish-green electroluminescent materials.

Full text of DOI:10.1002/hc.20201

Heteroatom Chemistry
Volume 17, Number 2, 2006
New Synthesis of Highly Potential Efficient
Bluish-Green Electroluminescent Materials
Based on 1,3,4-Oxadiazole–
Triazolopyridinone–Carbazole Derivatives
for Single-Layer Devices
Ming-Hsiang Shin,1 Fung Fuh Wong,2 Chun-Min Lin,1
Wen-Yi Chen,1 and Mou-Yung Yeh1,3
1Department of Chemistry, National Cheng Kung University, No. 1, Ta Hsueh Road,
Tainan 70101, Taiwan, R. O. C.
2Environmental Resource Management Research Center, National Cheng Kung University,
No. 500, Sec. 3, An-ming Road, Tainan City 709, Taiwan, R. O. C.
3Nan Jeon Institute of Technology, No. 178, Chaocin Road, Yanshuei Township,
Tainan County 737, Taiwan, R. O. C.
Received 11 April 2005; revised 4 September 2005
ABSTRACT: New potential bluish-green electrolumi-
nescent materials of 1,3,4-oxadiazole–triazolopyridin-
one–carbazole derivatives were synthesized and char-
acterized for single-layer devices. Carbazole, pyridine,
and triazolopyridinone were completely introduced
into 1,3,4-oxadiazole skeletal to play assistant roles
INTRODUCTION
in controlling fundamental photolytic process due to
the electron-donating nature, excellent photoconduc-
tivity, and flexible structure properties. Following the
spectroscopic studies and the measurements of cyclic
voltammogram, 1,3,4-oxadiazole–triazolopyridinone–
carbazole derivatives were highly efficient bluish-green
Thin-film organic light-emitting diodes (LEDs)
based on small molecules are of great interest due to
their potential application in the large-screen emis-
sive flat-panel color displays or as white backlights
for liquid crystal displays [1]. To accomplish op-
timal efficiency and device lifetime, the injection
and transport of holes and electrons must be bal-
anced, such that similar densities of the two carri-
ers are achieved. Two approaches can be employed
to balance carrier injection and transport, both in-
corporating hole- and electron-transporting mate-
rials into a LED [2]. One approach is to fabricate
a multilayer device with discrete hole-transporting
and/or electron-transporting layers [1,3]. A second
approach is to mix hole- and electron-transporting
materials into a blend [4,5], or to copolymerize
ꢀ
C
electroluminescent materials. 2006 Wiley Periodicals,
Inc. Heteroatom Chem 17:160–165, 2006; Published online
in Wiley InterScience (www.interscience.wiley.com). DOI
10.1002/hc.20201
Correspondence to: Fung Fuh Wong; e-mail: wongfungfuh@
yahoo.com.tw.
Contract grant sponsor: National Science Council of Republic
of China.
Contract grant number: NSC-850-6368.
2006 Wiley Periodicals, Inc.
c
ꢀ
160

New Synthesis of Highly Potential Efficient Bluish-Green Electroluminescent Materials 161
hole- and electron-transporting groups together [6,7]
RESULTS AND DISCUSSION
and prepare simple single-layer devices where the
active layer performs hole transport, electron trans-
port, and light emission. To fulfill such requirement,
easily synthesized materials of 1,3,4-oxadiazole–
triazolopyridinone–carbazole derivatives with good
film-forming properties and temporal stability are
desirable in this work.
Scheme 1 shows the synthetic route for the gen-
eration of 1,3,4-oxadiazole–pyridine–carbazole
compound (3). Nicotinohydrazide was prepared
by the reaction of ethyl nicotinate on hydrazine
monohydrhydrate at reflux in the EtOH solu-
tion for overnight [17]. After the reaction was
completed, the corresponding compound nicoti-
nohydrazide was provided as a white solid in 80%
yield. Nicotinohydrazide was applied to 9-hexyl-9H-
carbazole-3-carbaldehyde to give the corresponding
nicotinic acid[(9-hexyl-9H-carbazol-3-yl)methylene]
hydrazide 2 as yellow solid in 78% yields. Nicotinic
acid[(9-hexyl-9H-carbazol-3-yl)methylene] hydra-
zide 2 was performed the dehydration–cyclization
reaction at reflux with the strong oxidant reagent
KMnO4 in acetone solution to provide 1,3,4-
oxadiazole–pyridine–carbazole compound (3) in
70% isolated yield.
Carbazole [8], triazolopyridinone [9,10], and
their derivatives can be easily functionalized;
these moieties are beneficial for raising the glass
transition temperature and thermal stability. Car-
bazole and its derivatives have applied extensive in
functional materials as flexible building blocks for
construction due to their inherent electron-donating
nature, excellent photoconductivity, and unique
nonlinear optical property, such as photorefractive
materials [11], photoconductors [12], nonlinear
optical materials [13], light-emitting materials [14],
and hole-transporting materials [15]. Some of the
molecules related to triazolopyridinone have been
studied in the medical chemistry [9]. Triazolopy-
ridinone analogues are characterized by the same
fragment A, with two distinct basic nitrogen atoms:
one aromatic and the other aliphatic position. Tria-
zolopyridinones own the electron-donating proper-
ties and are investigated to improve the photolytic
properties [10]. Pyridine [16] is an electron-deficient
heterocycle, and it has been established that the
introduction of pyridine units into the main chain
of conjugated system to improve the electron-
transporting properties. In this paper, we first report
the 1,3,4-oxadiazole–triazolopyridinone–carbazole
hybrids as new potential blue and bluish-green elec-
troluminescent materials for single-layer devices.
From the structural point of view, carbazole,
pyridine, and triazolopyridinone moieties were
introduced to 1,3,4-oxadiazole molecule structure
as the chromophores to emphasize the conjugation
and expect to tune electroluminescent efficiencies
and hole- or electron-transport property.
ꢀ-Chloroformylarylhydrazine
hydrochloride
was synthesized according to our previous publish
procedure [18]. We treated 1,3,4-oxadiazole–
pyridine–carbazole compound (3) with ꢀ-chloro-
formylarylhydrazine hydrochloride with various
substituents, including H, CH3, and OEt groups
at 80◦C in i-PrOH solution for 2 h [17]. The solid
product was formed and the hot-filtration was
performed to isolate the crude 1,3,4-oxadiazole–
triazolopyridinone–carbazole derivatives 4a–4c.
The residues (4a–4c) were purified by recystalliza-
tion from CH2Cl2 to give the pure corresponding
products (4a–4c) as light yellow solid in 60–68%
yields (see Scheme 2).
The UV–Vis spectra of 1,3,4-oxadiazole–
pyridine–carbazole derivatives 3 and 1,3,4-oxadia-
zole–triazolopyridinone–carbazole derivatives 4a–
4c were measured in CH2Cl2 and CHCl3 solutions.
Absorption spectra of 3 and 4a–4c are almost
identical, which show four peaks at 242, 274, 304,
and 330 nm in CH2Cl2. The main peak absorption
SCHEME 1

162 Shin et al.
SCHEME 2
peak at 242 nm is contributed from carbazole
and 1,3,4-oxadiazole moieties [20]. The λmax val-
ues of pyridine is in the range 296–300 nm in
CH2Cl2. When the pyridine was modified with
ꢀ-chloroformylarylhydrazine hydrochloride to form
the triazolopyridinone heterocycles, the absorption
have a slightly red-shift to 306 nm (see Fig. 1).
The chromophore effect of pyridine and triazolopy-
ridinone are resemblance. Figure 2 shows the
photoluminescence (PL) spectra of 3 and 4a–4c.
The excitation wavelengths for 3 are between 380
and 450 nm in CH2Cl2 solution, respectively, and
the λmaxs of PL is ∼409 nm and has the intense blue
fluorescence in CH2Cl2 or CHCl3. When the struc-
tures (4a–4c) own the triazolopyridinone moieties,
the compounds have obviously redshift and exhibit
the intense bluish-green fluorescence in CH2Cl2 or
CHCl3 solution (λmax of PL is 385–545 nm). The solu-
tion fluorescence quantum yields (ꢀf) of 4a–4c, all of
which fall in the range 0.69–0.76, were determined
relative to that of 2-phenyl-5-(4-biphenyl)-1,3,4-
oxzdiazole in benzene (ꢀf = 0.80, see Table 1) [21].
The PL spectrum 4a of the vacuum-evaporated
films on quartz substrates, with a maximum at
498 nm, shows a red-shift (∼25 nm) with re-
spect to the solution spectrum as shown in Fig. 3.
Most of the published 1,3,4-oxadiazole–pyridine–
carbazole analogues were estimated as a poten-
tial bluish electroluminescent material. Whatever,
we successfully treated 1,3,4-oxadiazole–pyridine–
FIGURE 2 The fluorescence spectra of 3 and 4a–4c in
dichloromethane solution.
carbazole 3 with ꢀ-chloroformylarylhydrazine hy-
drochloride by means of the dehydration–cyclization
reaction to form the triazolopyridinone core. The
triazolopyridinone moiety efficiently conjugates and
connects two chromophores (oxadiazole and pyri-
dine) to provide the bluish-green electroluminescent
materials.
The electrochemical behavior of 4a–4c was
investigated by cyclic voltammetry in solution.
The measurements were carried out at a platinum
electrode using millimolar solution in using CH2Cl2
containing 0.1 M of the supporting electrolyte, tetra-
butylammonium hexafluorophosphate (TBAPF6), in
a three-electrode cell in potentiostat assembly. The
FIGURE 3 Normalized photoluminescence spectra of 4a
(vacuum-evaporated film).
FIGURE 1 The UV–Vis absorption of 3 and 4a–4c in
dichloromethane solution.

New Synthesis of Highly Potential Efficient Bluish-Green Electroluminescent Materials 163
TABLE 1 Electrochemical Properties of 4a–4c
c
d,e
f
I p = EH OMO
Eg = Bandgap
Ea = ELU MO
a
b
g
Compound
Eonset (V)
Eoꢁnset (V)
(eV)
energy (eV)
(eV)
ꢀ
f
4a
4b
4c
1.35
1.44
1.24
1.16
1.25
1.05
−5.96
−6.05
−5.85
3.21
3.21
3.21
−2.75
−2.84
−2.64
0.74
0.76
0.69
aMeasured vs. ferrocene/ferrocenium.
b Eoꢁnset = Eonset − 0.19 eV (measured vs. Ag/AgCl).
c Ip = −(Eoꢁnset + 4.8).
d Eg: the bandgap energy estimated from the onset wavelength of UV–Vis absorption.
eThe bandgap energy estimated based on the value 386 nm.
f Ea = Ip + Eg.
gꢀf: fluorescence quantum efficiency, relative to 2-phenyl-5-(4-biphenyl)-1,3,4-oxadiazole in benzene.
potential was measured against Ag/AgCl as reference
electrode, and each measurement was calibrated
with an internal standard, ferrocene/ferrocenium
(Fc) redox system [19]. The data were tabulated
in Table 1. Upon the anodic sweep, 4a–4c showed
irreversible reduction processes. The bandgap
energies of 1,3,4-oxadiazole–triazolopyridinone–
carbazole derivatives 4a–4c were estimated from
the onset wavelength (λonset) of the UV–Vis absorp-
tion [22]. From the high electron affinities, 4a–4c
owned the potential of electron-transporting and
highly efficient bluish-green electroluminescent
materials.
(150 × 2 mL). The combined EtOAc solutions were
washed with water and saturated aqueous NaCl. The
combined organic extracts were dried over MgSO4,
filtered, and concentrated under reduced pressure.
Ethanol (100 mL) was added to the residue and
precipitated the desired product. The wet cake was
dried in vacuum oven for overnight to give the 9-
hexyl-9H-carbazole as white powder in 80% yield
1
(20.0 g, 80.0 mmol): mp 56–57◦C; H NMR (DMSO-
d6, 200 MHz): δ 0.78 (t, J = 7.2 Hz, 3H, CH3),
1.05–1.30 (m, 6H, CH2), 1.73 (m, 2H, CH2), 4.36
(t, J = 6.9 Hz, 2H, CH2), 7.17 (dd, J = 6.8, 8.2 Hz,
2H, Ar-H), 7.56 (d, J = 8.2 Hz, 2H, Ar-H), 8.09 (dd,
J = 6.8, 8.2 Hz, 2H, Ar-H), 8.14 (d, J = 8.2 Hz, 2H,
Ar-H).
CONCLUSION
We are successful to prepare a sires of new potential
bluish-green electroluminescent materials based
on 1,3,4-oxadiazole–triazolopyridinone–carbazole
derivatives by using 1,3,4-oxadiazole–pyridine
compound with ꢀ-chloroformylarylhydrazine hy-
drochloride. Triazolopyridinone moiety obviously
plays an excellent assistant role in controlling
fundamental photolytic process.
9-Hexyl-9H-carbazole-3-carbaldehyde
A solution of cold POCl3 (130 mL) was added drop-
wise into DMF solution (60 mL) in ice-bath and
warmed up to room temperature for 1 h. The re-
action mixture was stirred at room temperature
for 2 h. 9-Hexyl-9H-carbazole (25.1 g, 0.10 mol,
0.10 equiv.) was added into the reaction mixture
in ice-bath for overnight. After the reaction was
completed, the reaction mixture was quenched with
NaHCO3 aqueous solution (100 mL) and stirred for
1 h. The precipitation was filtered and washed with
cold EtOH (50 mL). The wet cake was dried in
vacuum oven for overnight to give the 9-hexyl-9H-
carbazole-3-carbaldehyde as white powder in 72%
yield (20.1 g, 72.1 mmol): mp 58–59◦C; 1H NMR
(DMSO-d6, 200 MHz): δ 0.78 (t, J = 7.2 Hz, 3H, CH3),
1.10–1.25 (m, 6H, CH2), 1.71–1.74 (m, 2H, CH2),
4.41 (t, J = 6.9 Hz, 2H, CH2), 7.28 (dd, J = 6.7, 7.8
Hz, 1H, Ar-H), 7.51 (dd, J = 6.7, 8.0 Hz, 1H, Ar-H),
7.65 (d, J = 9.0 Hz, 1H, Ar-H), 7.72 (d, J = 8.0 Hz,
1H, Ar-H), 7.95 (d, J = 7.8 Hz, 1H, Ar-H), 8.26 (d,
J = 9.1 Hz, 1H, Ar-H), 8.73 (s, 1H, Ar-H), 10.06 (s, 1H,
CHO).
EXPERIMENTAL [17–19]
9-Hexyl-9H-carbazole
A solution of 9H-carbazole (16.7 g, 0.10 mole,
1.0 equiv.) and potassium hydroxide (8.40 g,
0.15 mole, 1.5 equiv.) was mixed and stirred in H2O
(40.0 mL) solution at room temperature for 15 min.
Tetrabutylammonium bromide (1.0 g, 10.3 mmol,
0.11 equiv.) was added dropwise into the reac-
tion mixture as catalyst. And then 1-bromohexane
(24.8 g, 0.15 mol, 1.5 equiv.) was added drop-
wise into the reaction mixture and heated up to
60◦C for 3 h. After the reaction was completed,
the reaction mixture was extracted with EtOAc

164 Shin et al.
42.90, 110.30, 110.60, 113.86, 120.19, 120.59, 122.10,
122.28, 122.81, 124.69, 126.27, 127.12, 134.47,
141.05, 142.26, 147.69, 152.69, 162.67, 162.91.
Nicotinic Acid[(9-hexyl-9H-carbazol-3-yl)methy-
lene] Hydrazide 2
A solution of nicotinohydrazide (5.00 g, 3.64 mmol,
1.1 equiv.) and 9-hexyl-9H-carbazole-3-carbalde-
hyde (0.90 g, 3.58 mmol, 1.0 equiv.) in EtOH (50 mL)
was stirred at 40◦C for 6 h. After the reaction
was completed, the reaction mixture was concen-
trated under reduced pressure to remove EtOH. The
residue was added with cold EtOH (20 mL), filtrated
and washed with cold EtOH (10 mL). The wet cake
was dried in vacuum oven for overnight to give the
nicotinic acid[(9-hexyl-9H-carbazol-3-yl)methylene]
hydrazide as yellow powder in 78% yield (1.11 g,
Standard Procedure for 6-(5-(9-Hextyl-9H-
carbazol-3-yl)-1,3,4-oxadiazol-2-yl)-2-phenyl-
[1,2,4]triazolo[4,3-a]pyridin-3(2H)-one
Derivatives 4a–4c
A solution of 9-hexyl-2-[5-(pyridin-3-yl)-1,3,4-oxa-
diazol-2-yl]-9H-carbazole 3 was stirred in i-PrOH
(15.0 mL) and n-tributylamine (1.0 mL) solution.
The reaction mixture was heated up to 80◦C.
ꢀ-Chloroformylarylhydrazine hydrochloride was
added into the reaction mixture. After the reaction
was completed, the hot-filtration was performed
and washed with cold ethanol (10 mL) to isolate the
solid crude product. The crude product was dried
and crystallized from CH2Cl2 to give a pure 4a–4c
as light yellow solid in 60–68% yields.
1
2.79 mmol): H NMR (DMSO-d6, 200 MHz): δ 0.78
(t, J = 7.2 Hz, 3H, CH3), 1.10–1.23 (m, 6H, CH2), 1.75
(m, 2H, CH2), 4.42 (t, J = 6.9 Hz, 2H, CH2), 7.22 (t,
J = 3.4 Hz, 1H, Ar-H), 7.47 (t, J = 3.4 Hz, 1H, Ar-H),
7.75–7.88 (m, 3H, Ar-H), 7.96 (t, J = 4.7 Hz, 1H, Ar-
H), 8.30 (d, J = 4.7 Hz, 1H, Ar-H), 8.47–8.61 (m, 3H,
Ar-H), 8.85 (s, 1H, Ar-H), 9.16 (s, 1H), 12.10 (b, 1H,
NH).
6-(5-(9-Hexyl-9H-carbazol-2-yl)-1,3,4-oxadiazol-
2-yl)-2-phenyl-[1,2,4]triazolo[4,3-a]pyridin-
3(2H)-one 4a
9-Hexyl-2-(5-(pyridin-3-yl)-1,3,4-oxadiazol-2-yl)-
9H-carbazole 3
A solution of nicotinic acid [(9-hexyl-9H-carbazol-
3-yl)methylene]hydrazide (5.00 g, 12.60 mmol,
1.0 equiv.) and KMnO4 (5.00 g) in acetone (50 mL)
was stirred at 50◦C for 4 h. After the reaction was
completed, the reaction mixture was concentrated
under reduced pressure to remove acetone. The
residue was added with a saturated NaSO3 aque-
ous solution (30 mL) and extracted with CH2Cl2
(30 mL). The reaction mixture was extracted with
EtOAc (150 × 2 mL). The combined EtOAc solu-
tions were washed with water and saturated aque-
ous NaCl. The combined organic extracts were dried
over MgSO4, filtered, and concentrated under re-
duced pressure. The wet cake was dried in vac-
uum oven for overnight to give the 9-hexyl-9H-
carbazole as white powder in 80% yield (20.0 g,
80.0 mmol). The wet cake was dried in vacuum oven
for overnight to give the 9-hexyl-2-(5-(pyridin-3-yl)-
1,3,4-oxadiazol-2-yl)-9H-carbazole as yellow powder
in 70% yield (3.49 g, 8.82 mmol): mp 223–225◦C; 1H
NMR (DMSO-d6, 200 MHz): δ 0.78 (t, J = 7.2 Hz, 3H,
CH3), 1.10–1.23 (m, 6H, CH2), 1.75 (m, 2H, CH2),
4.44 (t, J = 6.9 Hz, 2H, CH2), 7.32 (t, J = 4.8 Hz, 1H,
Ar-H), 7.60 (t, J = 4.8 Hz, 1H, Ar-H), 7.65–7.79 (m,
2H, Ar-H), 7.86 (d, J = 4.2 Hz, 1H, Ar-H), 8.24 (d,
J = 4.5 Hz, 1H, Ar-H), 8.36 (d, J = 4.5 Hz, 1H, Ar-H),
8.54 (d, J = 4.2 Hz, 1H, Ar-H), 8.80 (d, J = 3.5 Hz, 1H,
Ar-H), 8.98 (s, 1H), 9.32 (s, 1H); 13C NMR (DMSO-
d6, 50 MHz): δ 14.21, 22.38, 26.46, 28.85, 31.31,
A solution of 9-hexyl-2-[5-(pyridin-3-yl)-1,3,4-oxa-
diazol-2-yl]-9H-carbazole 3 (0.53 g, 1.34 mmol,
1.0 equiv.) was stirred in i-PrOH (15 mL) and tri-
ethylamine (1.0 mL) solution. The reaction mixture
was heated up to 80◦C. ꢀ-Chloroformylarylhydrazine
hydrochloride (0.29 g, 1.47 mmol, 1.1 equiv.) was
added into the reaction mixture. After the reaction
was completed, the hot-filtration was performed and
washed with cold ethanol (10 mL) to isolate the solid
crude product. The crude product was dried and
crystallized from CH2Cl2 to give a pure 4a as light
yellow solid in 60% yield (425 mg, 0.804 mmol): mp
1
278–280◦C; H NMR (DMSO-d6, 200 MHz): δ 0.78
(t, J = 7.2 Hz, 3H, CH3), 1.20–1.30 (m, 6H, CH2),
1.79 (m, 2H, CH2), 4.46 (t, J = 6.9 Hz, 2H, CH2),
7.28–7.36 (m, 3H), 7.57–7.67 (m, 4H), 7.84 (t, J =
4.5 Hz, 2H), 8.08 (d, J = 4.0 Hz, 2H), 8.25 (d,
J = 3.1 Hz, 1H), 8.25 (d, J = 3.1 Hz, 1H), 8.35 (d,
J = 3.5 Hz, 1H), 8.77 (s, 1H), 9.04 (s, 1H); 13C NMR
(DMSO-d6, 50 MHz): δ 14.21, 22.38, 26.46, 28.85,
31.31, 42.90, 110.30, 110.60, 113.86, 120.19, 120.59,
121.22, 122.10, 122.28, 122.81, 123.55, 124.69,
125.65, 126.27, 127.12, 134.47, 141.05, 142.26,
149.52, 152.69, 158.69, 162.21, 168.67, 169.91; IR
(KBr) 1602 (m, C N), 1725 (m, C O) cm−1; FABMS
m/z (relative intensity) 528 (M, 25), 529 (M + 1, 30),
250 (100), 77 (36). Anal. Calcd for C32H28ClN6O2: C,
72.71; H, 5.34; N, 15.90. Found: C, 72.76; H, 5.36; N,
15.90.

New Synthesis of Highly Potential Efficient Bluish-Green Electroluminescent Materials 165
δ 14.21, 14.30, 22.38, 26.46, 28.85, 31.31, 42.90,
64.26, 110.10, 110.40, 113.88, 120.29, 120.99, 121.52,
122.08, 122.18, 122.41, 123.15, 124.89, 125.55,
126.77, 1274.18, 134.27, 141.26, 146.69, 149.62,
152.99, 158.49, 162.61, 168.27, 168.91; IR (KBr) 1602
(m, C N), 1720 (m, C O) cm−1; FABMS m/z (relative
intensity) 572 (M, 40), 573 (M + 1, 30), 541 (100), 121
(60). Anal. Calcd for C34H32ClN6O3: C, 71.31; H, 5.63;
N, 14.48. Found: C, 71.35; H, 5.60; N, 14.68.
6-(5-(9-Hexyl-9H-carbazol-2-yl)-1,3,4-oxadiazol-
2-yl)-2-p-tolyl-[1,2,4]triazolo[4,3-a]pyridin-
3(2H)-one 4b
A solution of 9-hexyl-2-[5-(pyridin-3-yl)-1,3,4-oxa-
diazol-2-yl]-9H-carbazole 3 (0.51 g, 1.32 mmol,
1.0 equiv.) was stirred in i-PrOH (15 mL) and tri-
ethylamine (1.0 mL) solution. The reaction mixture
was heated up to 80◦C. ꢀ-Chloroformylarylhydrazine
hydrochloride (0.29 g, 1.46 mmol, 1.1 equiv.) was
added into the reaction mixture. After the reaction
was completed, the hot-filtration was performed and
washed with cold ethanol (10 mL) to isolate the solid
crude product. The crude product was dried and
crystallized from CH2Cl2 to give a pure 4b as light
yellow solid in 65% yield (473 mg, 0.872 mmol):
mp 265–267◦C; 1H NMR (DMSO-d6, 200 MHz): δ
0.78 (t, J = 7.2 Hz, 3H, CH3), 1.20–1.30 (m, 6H,
CH2), 1.79 (m, 2H, CH2), 2.35 (s, 3H, CH3), 4.46
(t, J = 6.9 Hz, 2H, CH2), 7.29–7.34 (m, 2H), 7.52 (t,
J = 5.0 Hz, 1H), 7.76 (d, J = 4.5 Hz, 2H), 7.84–7.96
(m, 4H), 8.28 (d, J = 3.1 Hz, 1H), 8.42 (d, J = 3.2 Hz,
1H), 8.74 (s, 1H), 9.03 (s, 1H); 13C NMR (DMSO-d6,
50 MHz): δ 14.21, 21.38, 22.89, 26.45, 28.88, 31.21,
42.89, 110.30, 113.86, 120.39, 121.62, 122.30, 122.58,
122.71, 123.25, 124.29, 125.55, 126.77, 127.22,
134.27, 141.15, 142.56, 147.69, 149.42, 152.59,
158.39, 162.91, 168.57, 169.71; IR (KBr) 1602 (m,
C N), 1722 (m, C O) cm−1; FABMS m/z (relative in-
tensity) 542 (M, 15), 543 (M + 1, 14), 318 (100), 91
(50). Anal. Calcd for C33H30ClN6O2: C, 73.04; H, 5.57;
N, 15.49. Found: C, 73.04; H, 5.57; N, 15.55.
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2-(4-Ethoxyphenyl)-6-(5-(9-hexyl-9H-carbazol-
2-yl)-1,3,4-oxadiazol-2-yl)-[1,2,4]triazolo[4,3-a]-
pyridin-3(2H)-one 4c
A solution of 9-hexyl-2-[5-(pyridin-3-yl)-1,3,4-oxa-
diazol-2-yl]-9H-carbazole 3 (0.55 g, 1.36 mmol,
1.0 equiv.) was stirred in i-PrOH (15 mL) and tri-
ethylamine (1.0 mL) solution. The reaction mixture
was heated up to 80◦C. ꢀ-Chloroformylarylhydrazine
hydrochloride (0.34 g, 1.49 mmol, 1.1 equiv.) was
added into the reaction mixture. After the reaction
was completed, the hot-filtration was performed and
washed with cold ethanol (10 mL) to isolate the solid
crude product. The crude product was dried and
crystallized from CH2Cl2 to give a pure 4c as light
yellow solid in 68% yield (530 mg, 0.925 mmol):
mp 294–296◦C; 1H NMR (DMSO-d6, 200 MHz): δ
0.78 (t, J = 7.2 Hz, 3H, CH3), 1.22–1.34 (m, 9H),
4.02 (q, J = 5.0 Hz, 2H, CH2), 1.79 (m, 2H, CH2),
4.46 (t, J = 6.9 Hz, 2H, CH2), 4.46 (t, J = 6.9 Hz,
2H, CH2), 7.28–7.33 (m, 2H), 7.67–7.55 (m, 4H), 7.89
(d, J = 3.7 Hz, 2H), 8.1 (d, J = 3.5 Hz, 2H), 8.20 (d,
J = 3.6 Hz, 1H), 8.35 (d, J = 4.0 Hz, 1H), 8.78 (s,
1H), 9.05 (s, 1H); 13C NMR (DMSO-d6, 50 MHz):
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Howard, J. A. Chem Mater 2001, 13, 1167.