Photo- and electroluminescent properties of cyano-substituted styryl derivatives and synthesis of CN-PPV model compounds containing an alkoxy spacer for OLEDs

Article abstract of DOI:10.1016/j.tet.2006.04.051

The series of cyano-substituted model compounds 18-20 for organic light emitting diodes (OLEDs) was prepared through Knoevenagel condensation reactions between the dialdehydes 3,6,9 and the differently substituted acetonitrile derivatives 11,16,17. The in

Full text of DOI:10.1016/j.tet.2006.04.051

Tetrahedron 62 (2006) 6236–6247
Photo- and electroluminescent properties of cyano-substituted
styryl derivatives and synthesis of CN–PPV model compounds
containing an alkoxy spacer for OLEDs
*
Hosuk Ryu, L. R. Subramanian and Michael Hanack
Eberhard-Karls-Universita€t Tu€bingen, Institut fu€r Organische Chemie, Auf der Morgenstelle 18, 72076 Tu€bingen, Germany
Received 20 December 2005; revised 7 April 2006; accepted 20 April 2006
Available online 18 May 2006
Abstract—The series of cyano-substituted model compounds 18–20 for organic light emitting diodes (OLEDs) was prepared through
Knoevenagel condensation reactions between the dialdehydes 3,6,9 and the differently substituted acetonitrile derivatives 11,16,17. The
influence of the different substituents on the optical properties of the resulting a-cyanostyryl compounds 18–20 was investigated. Another
series of dimeric cyano-substituted styryl compounds 26–28 were prepared, in which a flexible, nonconjugated spacer is present between
the two cyanostyryl moieties. The spacer isolates the p-conjugated portions of dimeric compounds 26–28, improves their solubility in com-
mon organic solvents, and decreases their tendency to crystallize. These features are favorable for producing efficient luminescent films in
OLEDs devices.
Ó 2006 Elsevier Ltd. All rights reserved.
1. Introduction
ill-defined structure, and generally scarce processability. For
these reasons much interest arose for developing new mate-
rials in electronic applications with low molecular mass. In
addition, short chain model compounds, which have elec-
tronic properties similar to those of their polymeric ana-
logues were synthesized and studied in order to understand
the mechanism of light emission in OLEDs.7 Recently,
a white-light-emitting electroluminescent device based on
a single-emitting-component with a carbazyl moiety has
been reported.8
During the last decade the application of organic materials in
the area of optoelectronic technology has received great
interest in academia and industry due to the easier fabrica-
tion in comparison to inorganic semiconductors and their
easily tunable optical properties. The discovery of light
emitting properties in electroluminescent (EL) devices
based on poly(p-phenylenevinylene) (PPV) became a mile-
stone in the development of organic light emitting mate-
rials,1 and numerous efforts have been directed to the
development of PPV derivatives in order to produce highly
efficient organic EL devices as commercial products.2,3 In
particular, the introduction of electron-withdrawing groups
on the polymer backbone (e.g., CN–PPV) results in a high
electron affinity polymer, which can be used to manufacture
organic light emitting diodes (OLEDs) with air-stable elec-
trodes and produces a strong red-shift in the photo- and elec-
troluminescent spectra.4 The tuning of color emission in
OLEDs can be accomplished by including functional groups
in the polymer backbone or by changing the polymer repeat
units.5,6 Polymers in electronic applications show some dis-
advantages such as lack of efficient purification procedures,
Furthermore, a number of PPV derivatives containing non-
conjugated blocks as spacer have been also studied.9 The
interruption of p-conjugation by spacers in the luminescent
materials results in a blue-shift of their PL and EL spectra
compared to fully conjugated materials and the nonconju-
gated spacer increases the solubility of the materials.
In this work, we present the synthesis and the characteriza-
tion of CN–PPV model compounds 18–20 containing
phenyl-, naphthyl-, and carbazyl units (Fig. 1). Upon varia-
tion of the substituents R, the influence on the photolumines-
cent and electroluminescent characteristics is investigated.
Moreover, the synthesis and optical properties of CN–PPV
model compounds 26–28 (Fig. 1) containing the alkoxy
spacer, –O(CH2)6O–, was also accomplished in order to
study their optical properties. The synthesis of 26–28 had
the purpose of increasing the solubility and the processabil-
ity of these compounds in the process of film preparation.
Keywords: Organic light emitting diodes; Photoluminescence; Electrolumi-
nescence; CN–PPV; Knoevenagel condensation; Spacer.
* Corresponding author. Tel.: +49 7071 2972432; fax: +49 7071 295268;
e-mail: hanack@uni-tuebingen.de
0040–4020/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.04.051

H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
6237
R
R
R
R
OC7H15
OC7H15
OC7H15
CN
CN
CN
CN
CN
CN
N
C7H15
OC7H15
19 (a-c)
R
R
18 (a-c)
20 (a-c)
C9H19
O
N
CN
OCH3
R =
N
a
b
c
R'
R'
O(CH2)6O
NC
CN
OC7H15
OC7H15
CN
R' =
N
OC7H15
C7H15
H3CO
OC7H15
26
27
28
Figure 1. General structures of model compounds 18–20 and 26–28.
2. Results and discussion
with DMF employing an excess of n-butyllithium/N,N,N0,N0-
tetramethylethylenediamine (TMEDA) complex in diethyl
ether to give the dialdehydes 3 and 6.11
The synthetic pathways for the precursors of the central units
of the model compounds 18–20 are shown in Scheme 1.
Dialdehydes 3 and 6 were prepared via dilithiation of aro-
matic ethers 2 and 5, which were obtained by alkylation
of commercially available hydroquinone and 1,5-dihydroxy-
naphthalene with n-bromoheptane in the presence of potas-
sium carbonate in dimethyl formamide (DMF).10 The
dilithiated intermediate of 2 and 5 was allowed to react
Compound 9 was obtained from 8 by Vilsmeier reaction with
an excess of phosphorus oxychloride and DMF.12 Alkylation
of commercially available carbazole 7 was accomplished
with n-bromoheptane in the presence of benzyltriethyl-
ammonium chloride (BTEAC) and aqueous sodium hydrox-
ide in benzene to obtain 8.13
OH
OC7H15
OC7H15
1) n-BuLi / TMEDA, Et
2) DMF
2O
CHO
C17H15Br
DMF
3) H3O+
OHC
OH
OC7H15
OC7H15
2
3
1
OC7H
OH
OC7H15
CHO
15 1) n-BuLi / TMEDA, Et2O
2) DMF
C17H15Br
DMF
3) H3O+
OHC
OH
OC7H15
OC7H15
4
5
6
OHC
CHO
C17H15Br / BTEAC
Benzene-NaOHaq.
DMF / POCl3
1,2-Dichloroethane
N
H
N
N
C7H15
C7H15
7
8
9
Scheme 1. Syntheses of dialdehyde precursors 3, 6, and 9.

6238
H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
Et4NCN
CH2Cl2
NC
NC
CH2Br
NC
CH2CN
11
10
N
C10H19COCl
Pyridine
O
NaN3 / NH4Cl
DMF
HN
N
C9
H19
CH3
CH3
CH3
N
N
N
12
13
14
Et4NCN
CH2Cl2
O
O
NBS
CCl4
H19C9
CH2CN
H19C9
CH2Br
N
N
N
N
16
15
Scheme 2. Syntheses of acetonitrile precursors 11 and 16.
The acetonitriles 11 and 16, which contain various substitu-
ents were prepared as shown in Scheme 2. p-Bromomethyl-
benzonitrile readily reacted with tetraethylammonium
cyanide (Et4NCN) in dichloromethane to give acetonitrile
11 under mild conditions.14
4-tolunitrile 12 with sodium azide in DMF.17 Compound 13
reacted with decanecarboxylic acid chloride in pyridine un-
der reflux to afford oxadiazole 14, which was then converted
to bromide 15 with N-bromosuccinimide (NBS) in CCl4.
Treatment of 15 with Et4NCN in dichloromethane gave
oxadiazole 16 using the same method as mentioned above.
Two synthetic routes to oxadiazoles are ring closure of bis-
hydrazides with dehydrating agents15 and intramolecular ring
transformation of tetrazoles with acid chlorides.16 In this
work the oxadiazole 14 was obtained via tetrazole 13 as an
intermediate. This synthetic route has some advantages,
such as short reaction time and facile work-up procedure,
in comparison to ring closure of bishydrazides with de-
hydrating agent. The tetrazole 13 was prepared by reacting
The syntheses of model compounds 18–20 were accom-
plished using Knoevenagel condensation18 between alkoxy-
or alkyl-substituted dialdehydes 3, 6, 9 and acetonitriles 11,
16, the commercially available 4-methoxyphenylacetonitrile
17, respectively, in tert-butyl alcohol and tetrahydrofuran
(THF) at 50 ꢀC (see Scheme 3). Potassium tert-butoxide
and tetra-n-butylammonium hydroxide were used as bases.
R
OC7H15
CHO
OC7H15
t-BuOK / (n-Bu)4N(OH)
CN
R
+
2NC
CN
OHC
t-BuOH / THF
OC7H15
OC7H15
R
3
18a (32%), 18b (40%), 18c (63%)
R
OC7H15
CHO
OC7H15
t-BuOK / (n-Bu)4N(OH)
t-BuOH / THF
CN
R
+
2NC
CN
OHC
OC7H15
OC7H15
R
19a (28%), 19b (26%), 19c (72%)
6
R
R
OHC
CHO
t-BuOK / (n-Bu)4N(OH)
R
+
2NC
CN
CN
t-BuOH / THF
N
N
C7H15
C7H15
20a (32%), 20b (14%), 20c (26%)
9
R =
CN
18a - 20a
11
16
17
C9H19
O
N
18b - 20b
18c - 20c
N
OCH3
Scheme 3. Synthesis of model compounds 18–20.

H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
6239
The Knoevenagel reaction is stereoselective, resulting in the
E,E-product. All compounds were characterized by 1H
NMR, 13C NMR, MS, IR, and UV–vis spectroscopy (see
Section 4).
Compounds 26–28 were synthesized by Knoevenagel
condensation between the monoaldehydes 21–23 and
1,6-bis(4-cyanomethylphenoxy)hexane 25, respectively, in
tert-butyl alcohol and THF at 50 ꢀC with potassium tert-
butoxide and tetra-n-butylammonium hydroxide as bases
to result in the E,E-products. All compounds were character-
ized by 1H NMR, 13C NMR, MS, IR, and UV–vis-spectros-
copy (see Section 4).
The monoformylation19 of 2 was accomplished by Friedel–
Crafts reaction with titanium tetrachloride as a Lewis acid
catalyst and dichloromethyl methyl ether to result in the for-
mation of 21. Compound 22 was prepared by Knoevenagel
condensation between excess of 3 and 4-methoxyphenyl-
acetonitrile 17 using potassium tert-butoxide as base in
tert-butyl alcohol and THF. The monoformylation of 8 was
carried out by using Vilsmeier reagent to afford compound
23 (Scheme 4).
2.1. Optical properties
Figures 2 and 3 show the UV–vis absorption and photolumi-
nescence (PL) spectra of 18–20 and 26–28, respectively. The
PL spectra were measured as thin films.
The reaction between 4-hydroxyphenylacetonitrile 24 and
1,6-dibromohexane was carried out in DMF with potassium
carbonate as base leading to 25, in which the two phenyl-
acetonitriles are separated by the alkoxy spacer –O(CH2)6O–.
Optical and electrical properties of conjugated materials are
dependent on the length of the conjugated p-system, inter-
chain distance of the conjugated segment, and the influence
of substituents (electron-donating or electron-withdrawing)
OH
OC7H15
OC7H15
CHO
CH3OCHCl2 / TiCl4
CH2Cl2, Reflux
C17H15Br
DMF
OH
1
OC7H15
2
OC7H15
21
OC7H15
OC7H15
CHO
H3CO
1) n-BuLi / TMEDA, Et2O
2) DMF
3) H3O+
CN
CHO
17
CN
t-BuOK / t-BuOH / THF
OHC
OC7H15
OC7H15
H3CO
3
22
CHO
C
17H15Br / BTEAC
DMF / POCl3
Benzene-NaOHaq.
1,2-Dichloroethane
N
N
N
H
7
C7H15
C7H15
8
23
K2CO3
DMF
OH
Br (CH2)6 Br
O(CH2)6O
+
2
NC
CN
NC
25
24
R'
R'
t-BuOK / (n-Bu)4N(OH)
t-BuOH / THF
21, 22 or 23 + 25
O(CH2)6O
NC
CN
OC H
15
7
OC H
7
15
CN
R' =
N
OC H
15
7
C H
15
7
H CO
OC H
7
3
15
26
27
28
Scheme 4. Synthetic pathways for model compounds 26–28.

6240
H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
Figure 2. UV–vis absorption (CH2Cl2) and PL spectra (thin film) of 18–20.
of the conjugated system. The influence of donor and accep-
tor substituents on the electronic structure of PPV deriva-
tives has been studied.20 Electron-donating substituents
lead to an overall destabilization of the HOMO and
LUMO levels. In contrast, electron-withdrawing substitu-
ents give a stabilization of the frontier levels. These substitu-
ents influence the location of HOMO and LUMO levels,
respectively, to result in a decrease of the band gap.
Figure 3. UV–vis and PL spectra of 26–28.

H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
6241
Table 1. UV–vis absorption maxima, the calculated band gap energy, and
PL maxima of 18–20 and 26–28
emission maxima of compounds 19 show a significant
blue-shift due to the loss of conjugation. The substituents
at the para-position of end phenyl ring (electron-donating
or -withdrawing) in compounds 19 do not affect the optical
properties in PL emission spectra. It is assumed that the in-
fluence of substituents is compensated by an opposite effect
due to predominant steric effects, therefore, compounds 19
exhibit similar PL maxima.
Compound
UV–vis (nm)a
Eg (eV)b
PL (nm)c
18a
18b
18c
19a
19b
19c
20a
20b
20c
26
353, 442
360, 446
366, 432
361, 412
370, 416
386, 404
332, 412
339, 417
336, 399
330, 374
364, 433
291, 381
2.36
2.35
2.45
2.65
2.63
2.71
2.65
2.65
2.79
2.85
2.45
2.85
618
636
615
511
508
515
528
522
495
493
632
468
The carbazole unit is very well known as a hole transporting,
electroluminescent material, and a wide band gap compo-
nent.24 Due to its wide band gap property conjugated sys-
tems based on carbazole units in compounds 20 exhibit
a blue-shift in comparison to the system based on phenyl
rings (compounds 18). Compounds 20 exhibit PL emission
maxima in the green or greenish yellow region (495–
528 nm). The optical properties of these compounds show
the same tendency as a result of their calculated band gap.
The electron-withdrawing (cyano or alkyl oxadiazolyl)
substituted 20a and 20b exhibit a red-shift compared to elec-
tron-donating (methoxy) substituted 20c. The results show
that the electron-withdrawing group affects more to reduce
the band gap in conjugated system unit than the donating
group on account of the effect of p-electron delocalization
along the entire conjugated system as described above.
27
28
a
UV–vis absorption in dichloromethane.
b
c
Band gaps were calculated from the absorption spectra of the given model
compound solutions.
PL emission in solid state (thin film on glass).
In this work the band gap energy of compounds 18–20 were
estimated from their UV–vis absorption spectra in solution
as shown in Table 1.
Compounds 18a and 18b containing electron-withdrawing
groups have smaller band gaps (p–p* transition energy)
than 18c possessing electron-donating substituent (Table
1). This result can be explained by the effect of p-electron
delocalization along the entire conjugated system. The in-
troduction of the electron-withdrawing groups at the end
phenyl rings in 18a and 18b increases the electron density
of the chromophoric block due to the induction of strong per-
manent dipoles affecting the donor/acceptor strengths of the
donating and withdrawing groups to result in a decrease of
the energy in the excited state. This increasing electron den-
sity causes an enhanced delocalization of conjugated sys-
tem. Although compound 18a has smaller band gap than
18c, both of them exhibit almost identical PL maximum in
the solid state. It is assumed that the interchain distance of
conjugated segment of 18a and 18c is similar in the solid
state. Compound 18b shows a red-shift in its PL spectrum
compared to 18a and 18c due to the interchain interaction
of oxadiazole moieties in the solid state.21
In general, OLEDs based on short chain PPV derivatives
exhibit no detectable electroluminescence (EL) due to their
electron conductive qualities. Therefore, an additional hole
transporting layer, thermally stable copper phthalocyanine
(PcCu) was used. The vacuum deposition of PcCu and model
compounds 18–20 onto ITO covered glass substrates was
accomplished, and the patterning of the devices were struc-
tured as described earlier.25 The configuration of bilayer
device is ITO/PcCu/model compound/Al as shown in
Figure 4a.
EL spectra of 18a, 18c, and 20c are almost identical to their
PL spectra, indicating that the same excited state is involved
in both EL and PL emission processes.26 However, EL spec-
tra of 19a and 20a exhibit a red-shift compared to their PL
spectra (Fig. 4). It is assumed that interchain interactions
are maximum in vapor deposited thin film of model com-
pounds and interchain excitation is accelerated to result in
the red-shift.27
Earlier studies have shown that partial replacement of the
phenylene unit in PPV by a naphthalene system linked
through 1,4-position shows a significant effect in photolumi-
nescence and electroluminescence emission maxima.22
However, in the case of conjugated materials based on naph-
thalene unit linked through 2,6-positions, their optical prop-
erties are more dependent on the steric effects than their
band structure.23 The geometry optimization has been car-
ried out by the Austin model 1 (AM 1) semiempirical tech-
nique to study the torsion and its effect on their structural and
electronic properties. The bulky 1,5-dialkoxynaphthalene
ring induces torsion of the main chain and, consequently, re-
duces the planarity of the backbone. The lack of planarity in
conjugated materials based on 1,5-dialkoxynaphthalene unit
linked through the 2,6-positions leads to a loss of conjuga-
tion and results in a blue-shift in their UV–vis spectra.23
The band gaps were increased by replacing the central phenyl
ring in cyano-substituted PPV derivatives with a bulky
1,5-diheptyloxynaphthalene ring (compounds 19) compared
to compounds 18 as shown in Table 1. Therefore, the PL
In the case of 19c, the EL spectrum shows a blue-shift com-
pared to its PL spectrum due to the re-absorption effect of
PcCu. Figure 4 shows the PL and EL spectra of 18–20.
In compounds 26–28 the photoluminescent cyano-
substituted PPV derivatives are separated by the nonconju-
gated segment, –O(CH2)6O–, as spacer group (Fig. 1). The
UV–vis absorption and PL emission spectra were measured
in dichloromethane and in solid state, respectively. The
results are shown in Table 1.
The p-conjugated systems in 26–28 are isolated from each
other through a flexible nonconjugated spacer. The introduc-
tion of the spacer improves the solubility in common organic
solvents and decreases crystallinity, enhancing the proper-
ties of the film formation in OLED application. Furthermore,
it is a convenient way to obtain a blue-shifted emission due

6242
H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
Figure 4. (a) Schematic setup of OLED, (b) PL and EL spectra of 18–20.
to an increase in the band gap by interrupting conjugation in
comparison with its fully conjugated system.
27 due to the influence of wide band gap component, carba-
zole.
Concerning the end-groups of 26–28, the band gap of 27 was
decreased significantly compared to 26 to result in a red-shift
in the UV–vis and PL spectra due to the extension of p-con-
jugated system. Compound 28 in which the carbazole ring is
combined to cyano-substituted stilbene moiety exhibits
a small blue-shift in its PL spectrum compared to 26 and
3. Conclusions
The influence of different substituents on the a-cyanostyryl
compounds 18–20 (phenyl, naphthalene or carbazole) was
investigated by studying their UV–vis, PL, and EL spectra.

H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
6243
The introduction of electron-donating or electron-withdraw-
ing groups into the conjugated system results in a red-shift in
their PL spectra on account of the decrease in the band gap,
and the effect is stronger in compounds containing electron-
withdrawing substituent due to the effect of p-electron delo-
calization along the entire conjugated system. In the case of
conjugated systems based on bulky 1,5-dialkoxynaphtha-
lene ring linked through 2,6-positions, a similar PL maxima
were observed. This is explained by predominant steric ef-
fect on their optical properties. The steric hindrance of the
bulky 1,5-diheptyloxynaphthalene ring reduces the planarity
of the backbone and results in a loss of conjugation, thus the
influence of substituents are similar between electron-donat-
ing and electron-withdrawing substituents. The replacement
of the central phenyl ring with a wide band gap carbazole re-
sults in a blue-shift in their UV–vis and PL spectra compared
to a-cyanostyryl compound based on phenyl ring. The elec-
tron-withdrawing substituents affect more to reduce the
band gap in the conjugated system based on carbazole unit
than the electron-donating substituents due to the effect of
p-electron delocalization along the entire conjugated sys-
tem.
configuration with a waveguide diode array setup in air at
room temperature. NMR spectra were recorded on a
Bruker AC 250 spectrometer at 250 MHz (1H) and
62.9 MHz (13C) in CDCl3 and internally referenced to
CHCl3 (1H: d¼7.24 ppm, 13C: d¼77.00 ppm). Mass spectra
were recorded on a Finnigan ISQ 70 and a Varian MAT 711
A. Elemental analysis of the products was carried out with
a Carlo Erba Elemental Analyzer 1106.
4.2. Synthesis
The following compounds were prepared according to
literature procedures: 1,4-di-n-heptyloxybenzene (2),10
1,5-di-n-heptyloxynaphthalene (5),10 9-n-heptylcarbazole
(8),13 3,6-diformyl-9-n-heptylcarbazole (9),12 p-cyano-
methylbenzonitrile (11),14 5-(p-tolyl)tetrazole (13),17 and
2,5-di-n-heptyloxybenzaldehyde (21).19 p-Bromomethyl-
benzonitrile (10), 4-methoxyphenylacetonitrile (17), and 4-
hydroxyphenylacetonitrile (24) are commercially available.
4.2.1. 2,5-Di-n-heptyloxyterephthaldialdehyde (3). A
2.5 M hexane solution of n-BuLi (24.6 ml, 61.5 mmol)
was added dropwise to a solution of 1,4-di-n-heptyloxybenz-
ene (2) (3.78 g, 12.3 mmol) and N,N,N0,N0-tetramethylethyl-
enediamine (TMEDA) (7.38 g, 63.5 mmol) in diethyl ether
(190 ml) at ꢁ78 ꢀC. The mixture was stirred at 0 ꢀC for
1 h and DMF (7.3 g, 100 mmol) was added, which caused
a yellow color to darken progressively. After refluxing for
16 h, the resulting pale brown suspension was placed in an
ice bath. The mixture was stirred for 90 min at 0 ꢀC and
then 4 N HCl solution (37 ml) was added slowly under vig-
orous stirring. The resulting two-phase system was stirred
for 30 min at room temperature. The organic layer was sep-
arated, washed with 0.5 N HCl solution (62 ml), saturated
NaHCO3 solution (62 ml), and brine (62 ml), and then dried
with anhydrous Na2SO4 and concentrated under reduced
pressure to give a yellow solid. The crude product was puri-
fied on a silica gel column (dichloromethane/n-hexane).
The electroluminescent properties of the model compounds
18–20 were studied in bilayer OLEDs with additional hole
transporting layer (PcCu). In general, the PL and EL spectra
are expected to be identical. However, the observed red- and
blue-shift in the EL spectra compared to PL spectra are due
to the film morphology of compounds and re-absorption
effect of PcCu as hole transporting material, respectively.
The optical properties of model compounds 26–28 contain-
ing spacer group were studied by extending the cyano-
substituted styryl moiety and replacing the phenyl ring
with a carbazole ring (i.e., wide band gap component) result-
ing in a red- and blue-shift, respectively. The introduction of
spacer moiety, –O(CH2)6O–, improves the solubility in com-
mon organic solvents and decreases crystallinity, enhancing
the properties of the film formation with physical vapor de-
position technique in OLED application. Furthermore, it is
a convenient way to obtain a blue-shifted emission due to
an increase in the band gap by interrupting conjugation,
i.e., shortening of chromophore unit.
1
Yield: 1.1 g (25%). Yellow solid. Mp 72–74 ꢀC. H NMR
(CDCl3): 10.49 (s, 2H), 7.40 (s, 2H), 4.05 (t, J¼6.4 Hz,
4H), 1.81 (m, 4H), 1.47 (m, 4H), 1.29 (m, 12H), 0.87 (t,
J¼7.0 Hz, 6H). 13C NMR (CDCl3): 189.34, 155.21,
129.28, 111.60, 69.24, 31.71, 29.21, 29.02, 25.95, 22.55,
14.01. IR (KBr): 2918, 2879, 1682, 1491, 1470, 1427,
1388, 1283, 1215, 1130, 1007, 696. MS: 362 (M+), 264,
166, 57. Anal. Calcd: C, 72.89; H, 9.45. Found: C, 73.21;
H, 9.52.
4. Experimental
4.1. General
4.2.2. 1,5-Di-n-heptyloxynaphthalene-2,6-dicarbalde-
hyde (6). Compound 6 was prepared by the same method
as 3 except for the starting material and the amount
of reagents: 1,5-di-n-heptyloxynaphthalene (5) (5.3 g,
15 mmol), 2.5 M n-BuLi (75 mmol), TMEDA (75 mmol),
DMF (8.8 g, 121 mmol), and diethyl ether (200 ml). The pu-
rification of the product was accomplished by chromato-
graphy on a silica gel column (dichloromethane/n-hexane).
Yield: 1.0 g (16%). Yellowish white solid. Mp 88–90 ꢀC.
1H NMR (CDCl3): 10.57 (s, 2H), 7.99 (d, J¼8.8 Hz, 2H),
7.93 (J¼8.8 Hz, 2H), 4.15 (t, J¼6.4 Hz, 4H), 1.95 (m,
4H), 1.33 (m, 16H), 0.89 (t, J¼6.7 Hz, 6H). 13C NMR
(CDCl3): 189.48, 161.53, 133.13, 127.45, 123.63, 119.50,
79.47, 31.72, 30.24, 29.07, 25.90, 22.56, 14.03. IR (KBr):
2949, 2948, 2854, 1682, 1499, 1466, 1377, 1366, 1227,
Chemicals received from commercial sources (Aldrich,
Merck, and Fluka) were used without further purification.
All reactions were performed under a dry argon atmosphere.
Solvents were dried according to standard procedures. The
melting points are uncorrected.
Infrared spectra were taken as KBr pellets or with NaCl plate
using a Bruker IFS 48 spectrometer. UV–vis spectra were re-
corded in CH2Cl2 solution with a Shimadzu UV-2102 PC.
PL of evaporated films was measured with a SPEX fluorolog
112 in the 45ꢀ configuration. For EL measurements an HP
6030A voltage source was used together with a Keithley
171 DMM. The EL spectra were taken from devices with
ITO/copper phthalocyanine (PcCu)/trimer 18–20/Al

6244
H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
1015, 822, 762. MS: 412 (M+), 314, 216, 131, 57. Anal.
Calcd: C, 75.69; H, 8.80, Found: C, 75.71; H, 8.55.
41. Anal. Calcd: C, 73.28; H, 8.09; N, 13.49. Found: C,
72.40; H, 7.80; N, 13.06.
4.2.3. 5-(p-Tolyl)-2-n-nonyl-1,3,4-oxadiazole (14). To a so-
lution of 5-(p-tolyl)tetrazole (13) (9.6 g, 60 mmol) in pyri-
dine (95 ml) was added decanecarboxylic acid chloride
(11.5 g, 60 mmol). After refluxing for 2 h under argon, the
reaction mixture was cooled and poured into water contain-
ing crushed ice. The precipitate was collected in a sintered
glass filter and then washed with water several times. The
crude product was dried under vacuum for overnight. The
purification was accomplished by chromatography on a
silica gel column using chloroform as eluent. Yield: 14.1 g
(82%). White solid. Mp 55–57 ꢀC. 1H NMR (CDCl3):
7.88 (d, J¼7.9 Hz, 2H), 7.29 (d, J¼7.9 Hz, 2H), 2.88 (t,
J¼7.3 Hz, 2H), 2.40 (s, 3H), 1.81 (m, 2H), 1.24 (m, 12H),
0.85 (t, J¼6.7 Hz, 3H). 13C NMR (CDCl3): 166.75,
164.78, 141.91, 129.66, 126.69, 121.37, 31.81, 29.34,
29.21, 29.10, 29.01, 26.60, 25.43, 23.63, 21.58, 14.06. IR
(KBr): 2920, 2851, 1616, 1569, 1556, 1501, 1475, 1180,
1088, 1011, 959, 824, 727. MS: 286 (M+), 257, 243, 229,
216, 201, 187, 174, 119, 117, 91, 55, 43, 41. Anal. Calcd:
C, 75.48; H, 9.15; N, 9.78. Found: C, 75.15; H, 8.83; N,
9.11.
4.3. General procedure for the preparation of a-cyano-
styryl compounds (18–20)
To a tert-butyl alcohol/THF solution of an aldehydes (3, 6 or
9) and acetonitrile derivatives (11, 16 or 17), respectively, at
50 ꢀC under inert gas, a stoichiometric amount of potassium
tert-butoxide and a methanolic solution of tetra-n-butylam-
monium hydroxide (catalytic amount) were added quickly
(Scheme 3). The mixture was stirred vigorously for 20 min
at 50 ꢀC. After cooling, the mixture was poured into metha-
nol. The precipitate (18–20) was collected using a sintered
glass filter, washed with methanol, and dried under vacuum.
The purification of 18–20 was accomplished by chromato-
graphy on a silica gel column using dichloromethane or
chloroform as eluent.
4.3.1. 1,4-Bis(4-cyano-a-cyanostyryl)-2,5-di-n-heptyl-
oxybenzene (18a). Yield: 32%. Orange solid. Mp 244–
1
246 ꢀC. H NMR (CDCl3): 8.12 (s, 2H), 7.89 (s, 2H), 7.77
(d, J¼8.9 Hz, 4H), 7.75 (d, J¼8.9 Hz, 4H), 4.11 (t,
J¼6.4 Hz, 4H), 1.84 (m, 4H), 1.29 (m, 16H), 0.86 (t,
J¼6.7 Hz, 6H). 13C NMR (CDCl3): 151.84, 138.83,
126.60, 125.85, 118.18, 117.47, 112.81, 111.37, 110.48,
69.56, 31.77, 29.09, 28.96, 26.10, 22.54, 14.06. IR (KBr):
2951, 2930, 2856, 2226, 2212, 1585, 1510, 1499, 1431,
1366, 1294, 1252, 1219, 1024, 835. MS: 610 (M+). UV–
vis (CH2Cl2): 353, 442. PL: 618. EL: 632. Anal. Calcd: C,
78.66; H, 6.93; N, 9.17. Found: C, 78.11; H, 6.89; N, 9.23.
4.2.4. 5-(p-Bromomethylphenyl)-2-n-nonyl-1,3,4-oxadia-
zole (15). A mixture of 5-(p-tolyl)-2-n-nonyl-1,3,4-oxadia-
zole (14) (13.0 g, 45.4 mmol), N-bromosuccinimide (8.3 g,
46.6 mmol), dry carbon tetrachloride (250 ml), and catalytic
amount of azobisisobutyronitrile was stirred at reflux under
nitrogen for 10 h. The warm solution was filtered, and the fil-
trate was concentrated to give a light yellow solid. The crude
product was purified by recrystallization from carbon tetra-
chloride. Yield: 8.4 g (51%). White solid. Mp 87–89 ꢀC. 1H
NMR (CDCl3): 8.00 (d, J¼8.2 Hz, 2H), 7.51 (d, J¼8.5 Hz,
2H), 4.49 (s, 2H), 2.90 (t, J¼7.3 Hz, 2H), 1.82 (m, 2H),
1.24 (m, 12H), 0.85 (t, J¼7.0 Hz, 3H). 13C NMR (CDCl3):
167.17, 141.15, 129.63, 127.14, 124.02, 32.25, 31.80,
29.33, 29.18, 29.09, 28.99, 26.55, 25.43, 22.61, 14.06. IR
(KBr): 2918, 2851, 1587, 1566, 1501, 1472, 1418, 1229,
1204, 1086, 1015, 854, 704. MS: 364 (M+), 335, 321, 308,
294, 285, 265, 252, 228, 197, 186, 173, 131, 118, 116, 90,
43. Anal. Calcd: C, 59.18; H, 6.90; Br, 21.87; N, 7.67.
Found: C, 58.98; H, 6.11; Br, 21.86; N, 7.60.
4.3.2. 1,4-Bis[4-(2-n-nonyl-1,3,4-oxadiazolyl)-a-cyano-
styryl]-2,5-di-n-heptyloxybenzene (18b). Yield: 40%.
Pale red solid. Mp 165–167 ꢀC. 1H NMR (CDCl3): 8.13 (s,
2H), 8.09 (d, J¼8.9 Hz, 4H), 7.91 (s, 2H), 7.83 (d,
J¼8.6 Hz, 4H), 4.13 (t, J¼6.4 Hz, 4H), 2.93 (t, J¼7.3 Hz,
4H), 1.85 (m, 8H), 1.26 (m, 40H), 0.86 (t, J¼6.7 Hz,
12H). 13C NMR (CDCl3): 167.37, 163.99, 151.77, 137.45,
137.19, 127.42, 126.58, 125.92, 124.66, 117.86, 111.42,
110.95, 69.54, 31.83, 31.78, 29.36, 29.21, 29.16, 29.12,
29.04, 29.01, 26.60, 26.14, 25.49, 22.64, 22.55, 14.06. IR
(KBr): 2955, 2922, 2851, 2214, 1583, 1497, 1466, 1416,
1366, 1294, 1217, 1007, 847. MS: 949 (M+). UV–vis
(CH2Cl2): 360, 446. PL: 636. EL: 655. Anal. Calcd: C,
75.91; H, 8.49; N, 8.85. Found: C, 75.63; H, 8.15; N, 8.89.
4.2.5. 5-(p-Cyanomethylphenyl)-2-n-nonyl-1,3,4-oxadia-
zole (16). A portion of tetraethylammonium cyanide
(2.0 g, 12.8 mmol) was added to a stirred solution of
5-(p-bromomethylphenyl)-2-n-nonyl-1,3,4-oxadiazole (15)
(3.0 g, 8.2 mmol) and dichloromethane (150 ml). The reac-
tion mixture was stirred for 5 h at room temperature and
then washed with water. After evaporation of the solvent,
the product was purified by chromatography on a silica gel
column using dichloromethane/ethyl acetate as eluent.
4.3.3. 1,4-Bis(4-methoxy-a-cyanostyryl)-2,5-di-n-heptyl-
oxybenzene (18c). Yield: 63%. Orange solid. Mp 158–
1
160 ꢀC. H NMR (CDCl3): 7.89 (s, 2H), 7.85 (s, 2H), 7.60
(d, J¼8.9 Hz, 4H), 6.97 (d, J¼8.9 Hz, 4H), 4.10 (t,
J¼6.4 Hz, 4H), 3.85 (s, 6H), 1.83 (m, 4H), 1.31 (m, 16H),
0.87 (t, J¼6.7 Hz, 6H). 13C NMR (CDCl3): 160.50,
151.42, 134.03, 127.42, 125.76, 118.52, 114.48, 111.19,
69.46, 55.42, 31.80, 29.24, 29.02, 26.16, 22.53, 14.04. IR
(KBr): 2955, 2930, 2854, 2208, 1607, 1514, 1466, 1431,
1367, 1300, 1250, 1217, 1180, 1036, 822. MS: 620 (M+).
UV–vis (CH2Cl2): 366, 432. PL: 615. EL: 633. Anal.
Calcd: C, 77.39; H, 7.79; N, 4.51. Found: C, 77.36; H,
8.03; N, 4.47.
1
Yield: 2.1 g (82%). White solid. Mp 93–95 ꢀC. H NMR
(CDCl3): 8.02 (d, J¼8.2 Hz, 2H), 7.48 (d, J¼8.5 Hz, 2H),
3.82 (s, 2H), 2.90 (t, J¼7.3 Hz, 2H), 1.82 (m, 2H), 1.24
(m, 12H), 0.85 (t, J¼6.7 Hz, 3H). 13C NMR (CDCl3):
167.28, 163.99, 133.33, 128.60, 127.49, 124.13, 117.01,
31.81, 29.34, 29.19, 29.09, 29.01, 26.57, 25.45, 23.64,
22.61, 14.06. IR (KBr): 2953, 2916, 2849, 2245, 1697,
1589, 1570, 1504, 1472, 1421, 1090, 918, 825, 723. MS:
311 (M+), 282, 268, 241, 212, 199, 157, 144, 116, 89, 55,
4.3.4. 2,6-Bis(4-cyano-a-cyanostyryl)-1,5-di-n-heptyl-
oxynaphthalene (19a). Yield: 28%. Yellow solid. Mp

H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
6245
1
221–223 ꢀC. H NMR (CDCl3): 8.37 (d, J¼8.9 Hz, 2H),
4.30 (t, J¼6.7 Hz, 2H), 2.92 (t, J¼7.3 Hz, 4H), 1.85 (m,
6H), 1.26 (m, 32H), 0.87 (m, 9H). 13C NMR (CDCl3):
167.25, 164.06, 144.00, 142.37, 137.80, 127.89, 127.31,
126.11, 125.45, 123.94, 123.14, 118.47, 109.77, 107.02,
43.66, 31.36, 29.36, 29.21, 29.12, 29.04, 28.96, 27.18,
26.58, 25.48, 22.62, 22.52, 14.06. IR (KBr): 2955, 2926,
2854, 2210, 1585, 1566, 1499, 1420, 1308, 1236, 1204,
1138, 843. MS: 908 (M+). UV–vis (CH2Cl2): 339, 417.
PL: 522. Anal. Calcd: C, 78.02; H, 7.66; N, 10.80. Found:
C, 77.14; H, 7.86; N, 10.56.
8.20 (s, 2H), 8.02 (d, J¼8.9 Hz, 2H), 7.83 (d, J¼8.9 Hz,
4H), 7.78 (d, J¼8.9 Hz, 4H), 4.02 (t, J¼6.4 Hz, 4H), 1.91
(m, 4H), 1.32 (m, 16H), 0.88 (t, J¼6.7 Hz, 6H). 13C NMR
(CDCl3): 157.01, 139.02, 138.74, 132.94, 130.77, 126.51,
124.76, 119.15, 118.11, 117.15, 112.94, 111.10, 77.80,
31.78, 30.42, 29.13, 26.28, 22.57, 14.06. IR (KBr): 2961,
2928, 2854, 2228, 2214, 1591, 1506, 1467, 1412, 1371,
1250, 1186, 1063, 991, 841, 824. MS: 660 (M+). UV–vis
(CH2Cl2): 361, 412. PL: 511. EL: 563. Anal. Calcd: C,
79.97; H, 6.71; N, 8.48. Found: C, 79.54; H, 6.76; N, 8.44.
4.3.9. 3,6-Bis(4-methoxy-a-cyanostyryl)-9-n-heptylcar-
bazole (20c). Yield: 26%. Greenish yellow solid. Mp 119–
121 ꢀC. 1H NMR (CDCl3): 8.54 (s, 2H), 8.12 (d,
J¼8.5 Hz, 2H), 7.60 (d, J¼8.9 Hz, 4H), 7.57 (s, 2H), 7.43
(d, J¼8.9 Hz, 2H), 6.97 (d, J¼8.9 Hz, 4H), 4.27 (t,
J¼7.0 Hz, 2H), 3.84 (s, 6H), 1.86 (m, 2H), 1.25 (m, 8H),
0.85 (t, J¼6.7 Hz, 3H). 13C NMR (CDCl3): 160.05,
141.79, 141.02, 127.58, 127.04, 125.88, 123.06, 122.50,
119.06, 114.39, 109.46, 107.87, 55.41, 43.52, 31.65,
28.98, 27.18, 22.52, 14.00. IR (KBr): 2953, 2930, 2208,
1605, 1585, 1512, 1485, 1389, 1356, 1286, 1250, 1182,
1036, 829. MS: 579 (M+). UV–vis (CH2Cl2): 336, 399.
PL: 495. EL: 495. Anal. Calcd: C, 80.80; H, 6.43; N, 7.25.
Found: C, 80.36; H, 5.76; N, 7.29.
4.3.5. 2,6-Bis[4-(2-n-nonyl-1,3,4-oxadiazolyl)-a-cyano-
styryl]-1,5-di-n-heptyloxynaphthalene (19b). Yield:
26%. Greenish yellow solid. Mp 165–167 ꢀC. 1H NMR
(CDCl3): 8.38 (d, J¼9.2 Hz, 2H), 8.21 (s, 2H), 8.12 (d,
J¼8.9 Hz, 4H), 8.02 (d, J¼9.2 Hz, 2H), 7.89 (d, J¼8.9 Hz,
4H), 4.03 (t, J¼6.7 Hz, 4H), 2.94 (t, J¼7.6 Hz, 4H), 1.89
(m, 4H), 1.26 (m, 40H), 0.86 (t, J¼7.0 Hz, 12H). 13C
NMR (CDCl3): 167.40, 163.96, 156.71, 137.80, 137.32,
130.63, 127.48, 126.49, 124.88, 119.52, 117.56, 111.66,
31.83, 30.45, 29.36, 29.22, 29.18, 29.12, 29.04, 26.60,
26.31, 25.49, 22.64, 22.58, 14.06. IR (KBr): 2920, 2851,
2218, 1601, 1585, 1568, 1499, 1470, 1416, 1371, 1242,
1180, 1034, 1011, 851, 841. MS: 999 (M+). UV–vis
(CH2Cl2): 370, 416. PL: 508. EL: 500. Anal. Calcd: C,
76.92; H, 8.27; N, 8.41. Found: C, 76.61; H, 8.23; N, 8.32.
4.3.10. 4-(4-Methoxy-a-cyanostyryl)-2,5-di-n-heptyl-
oxybenzaldehyde (22). To a solution of 2,5-di-n-heptyl-
oxyterephthaldialdehyde (3) (0.69 g, 1.90 mmol) and
4-methoxyphenylacetonitrile (17) (0.16 g, 1.09 mmol) in a
mixture of tert-butyl alcohol (4 ml) and THF (7 ml) under
inert gas was added potassium tert-butoxide (0.02 g,
0.18 mmol) in one portion at 40 ꢀC. The mixture was stirred
for 15 min at 40 ꢀC, cooled, and poured into methanol. The
precipitate was filtered off and dichloromethane (100 ml)
was added to the filtrate. The solution was washed with
water several times, dried with anhydrous Na2SO4, and con-
centrated under reduced pressure to give a crude product.
The purification was accomplished by column chromato-
graphy on silica gel using dichloromethane/n-hexane as elu-
4.3.6. 2,6-Bis(4-methoxy-a-cyanostyryl)-1,5-di-n-heptyl-
oxynaphthalene (19c). Yield: 72%. Greenish yellow solid.
Mp 162–164 ꢀC. 1H NMR (CDCl3): 8.31 (d, J¼9.2 Hz,
2H), 7.98 (d, J¼8.9 Hz, 2H), 7.97 (s, 2H), 7.65 (d,
J¼8.9 Hz, 4H), 7.00 (d, J¼8.9 Hz, 4H), 4.00 (t, J¼6.4 Hz,
4H), 3.86 (s, 6H), 1.90 (m, 4H), 1.31 (m, 16H), 0.88 (t,
J¼6.7 Hz, 6H). 13C NMR (CDCl3): 160.64, 155.88,
134.45, 130.25, 127.34, 125.02, 124.91, 119.15, 118.20,
114.57, 112.19, 77.08, 55.45, 31.81, 30.45, 29.19, 26.31,
22.58, 14.04. IR (KBr): 2955, 2928, 2854, 2218, 1609,
1510, 1458, 1408, 1369, 1288, 1261, 1182, 1072, 1034,
835. MS: 670 (M+). UV–vis (CH2Cl2): 386, 404. PL: 515.
EL: 473. Anal. Calcd: C, 78.77; H, 7.51; N, 4.18. Found:
C, 78.72; H, 7.55; N, 4.25.
1
ent. Yield: 0.14 g (26%). Yellow solid. Mp 60–62 ꢀC. H
NMR (CDCl3): 10.47 (s, 1H), 7.84–7.83 (ss, 2H), 7.63 (d,
J¼8.9 Hz, 2H), 7.32 (s, 1H), 6.97 (d, J¼8.9 Hz, 2H), 4.13
(t, J¼6.1 Hz, 2H), 4.01 (t, J¼6.4 Hz, 2H), 3.84 (s, 3H),
1.81 (m, 4H), 1.29 (m, 16H), 0.87 (m, 6H). 13C NMR
(CDCl3): 188.98, 160.78, 155.60, 151.31, 133.71, 130.13,
127.57, 126.84, 125.98, 118.05, 114.39, 113.42, 112.77,
109.69, 69.37, 69.21, 55.44, 31.75, 29.16, 29.09, 28.99,
28.96, 26.04, 22.57, 22.54, 14.04. IR (KBr): 2957, 2935,
2856, 2212, 1684, 1607, 1516, 1487, 1427, 1393, 1285,
1244, 1207, 1186, 1132, 1036, 831. MS: 491 (M+). UV–
vis (CH2Cl2): 355, 408. Anal. Calcd: C, 75.73; H, 8.41; N,
2.85. Found: C, 75.68; H, 8.52; N, 2.85.
4.3.7. 2,6-Bis(4-cyano-a-cyanostyryl)-9-n-heptylcarba-
1
zole (20a). Yield: 32%. Yellow solid. Mp 225–227 ꢀC. H
NMR (CDCl3): 8.67 (d, J1¼1.5 Hz, 2H), 8.16 (dd,
J1¼1.8 Hz, J2¼8.9 Hz, 2H), 7.79 (s, 2H), 7.77 (d,
J¼8.5 Hz, 4H), 7.72 (d, J¼8.5 Hz, 4H), 7.51 (d, J¼8.6 Hz,
2H), 4.32 (t, J¼7.0 Hz, 2H), 1.89 (m, 2H), 1.24 (m, 8H),
0.85 (t, J¼6.7 Hz, 3H). 13C NMR (CDCl3): 145.25,
142.66, 139.29, 132.75, 128.28, 126.13, 125.22, 123.31,
123.19, 118.33, 118.09, 112.00, 109.95, 106.40, 43.73,
31.65, 28.95, 27.18, 22.50, 13.98. IR (KBr): 2953, 2928,
2226, 2212, 1580, 1487, 1391, 1259, 1238, 1196, 1138,
839. MS: 569 (M+). UV–vis (CH2Cl2): 332, 412. PL: 528.
EL: 580. Anal. Calcd: C, 82.22; H, 5.48; N, 12.29. Found:
C, 82.53; H, 4.43; N, 12.29.
4.3.11. 3-Formyl-9-n-heptylcarbazole (23). Phosphorus
oxychloride (3.7 g, 24 mmol) was added dropwise to DMF
(1.7 g, 23 mmol) at 0 ꢀC. 9-n-Heptylcarbazole (8) (6.0 g,
22.6 mmol) in 1,2-dichloroethane (30 ml) was added to the
reaction mixture at room temperature. The mixture was re-
fluxed for 6 h. After cooling, the mixture was poured into
water and extracted with dichloromethane. The solution
was washed with water, dried with anhydrous Na2SO4, and
concentrated under reduced pressure to give a crude product.
4.3.8. 3,6-Bis[4-(2-n-nonyl-1,3,4-oxadiazolyl)-a-cyano-
styryl]-9-n-heptylcarbazole (20b). Yield: 14%. Dark yel-
low solid. Mp 154–156 ꢀC. 1H NMR (CDCl3): 8.64 (s,
2H), 8.16 (d, J¼8.5 Hz, 2H), 8.06 (d, J¼8.6 Hz, 4H), 7.79
(d, J¼8.5 Hz, 4H), 7.78 (s, 2H), 7.48 (d, J¼8.6 Hz, 2H),

6246
H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
The purification was accomplished by chromatography on
a silica gel column using ethyl acetate/n-hexane as eluent.
The viscous pale yellow liquid was solidified on standing
at room temperature. Yield: 2.7 g (41%). Pale yellow solid.
127.33, 127.16, 125.75, 125.69, 118.56, 114.97, 114.45,
111.19, 111.12, 69.42, 68.01, 31.80, 29.24, 29.13, 29.04,
26.16, 25.83, 22.57, 14.09. IR (KBr): 2932, 2854, 2208,
1607, 1514, 1431, 1300, 1248, 1217, 1182, 1034, 824.
MS: 1295 (M+). UV–vis: 364, 433. PL: 632. EL: 545, 641.
Anal. Calcd: C, 77.86; H, 7.93; N, 4.32. Found: C, 77.64;
H, 7.80; N, 4.21.
1
Mp 60–62 ꢀC. H NMR (CDCl3): 10.07 (s, 1H), 8.58 (d,
J1¼1.2 Hz, 1H), 8.12 (d, J¼7.6 Hz, 1H), 7.96 (dd,
J1¼1.8 Hz, J2¼8.5 Hz, 1H), 7.46–7.30 (m, 4H), 4.30 (t,
J¼7.3 Hz, 2H), 1.86 (m, 2H), 1.22 (m, 8H), 0.84 (t,
J¼6.7 Hz, 3H). 13C NMR (CDCl3): 191.69, 144.03,
141.14, 128.48, 127.10, 126.66, 123.93, 123.03, 122.97,
120.69, 120.24, 109.36, 108.89, 43.40, 31.63, 28.98,
28.90, 27.19, 22.52, 13.98. IR (KBr): 2951, 2916, 2852,
1690, 1626, 1591, 1497, 1470, 1381, 1339, 1234, 1180,
1134, 810, 752. MS: 293 (M+), 208, 180, 152, 84, 49.
Anal. Calcd: C, 81.87; H, 7.90; N, 4.77. Found: C, 81.53;
H, 7.80; N, 4.76.
4.4.3. 1,6-Bis[(3-(9-n-heptylcarbazyl))-4-b-cyanostyryl-
oxy]hexane (28). Yield: 39%. Pale yellow solid. Mp 126–
1
128 ꢀC. H NMR (CDCl3): 8.57 (d, J¼1.2 Hz, 2H), 8.11
(d, J¼7.9 Hz, 2H), 8.06 (dd, J1¼1.5 Hz, J2¼8.9 Hz, 2H),
7.60 (d, J¼8.9 Hz, 4H), 7.58 (s, 2H), 7.42–7.26 (m, 8H),
6.97 (d, J¼8.9 Hz, 4H), 4.27 (t, J¼7.3 Hz, 4H), 4.02 (t,
J¼6.4 Hz, 4H), 1.85 (m, 8H), 1.56 (m, 4H), 1.25 (m,
16H), 0.85 (t, J¼7.0 Hz, 6H). 13C NMR (CDCl3): 159.44,
141.47, 141.35, 140.96, 127.67, 126.98, 126.83, 126.26,
125.02, 123.16, 122.79, 122.14, 120.67, 119.62, 119.26,
114.91, 109.07, 108.98, 107.14, 67.96, 43.26, 31.66,
29.13, 29.01, 28.96, 27.22, 25.80, 22.54, 14.00. IR (KBr):
2928, 2860, 2208, 1605, 1589, 1512, 1493, 1475, 1389,
1348, 1288, 1248, 1182, 1028, 833, 748. MS: 898 (M+).
UV–vis: 291, 381. PL: 468. Anal. Calcd: C, 82.81; H,
7.40; N, 6.23. Found: C, 81.69; H, 6.99; N, 6.08.
4.3.12. 1,6-Bis(4-cyanomethylphenoxy)hexane (25). A
solution of 4-hydroxyphenylacetonitrile (24) (1.9 g,
14.3 mmol), 1,6-dibromohexane (1.6 g, 6.6 mmol), and po-
tassium carbonate (4.0 g, 29.0 mmol) in DMF (50 ml) was
stirred at 70 ꢀC overnight. The resulting mixture was poured
into cold water. The precipitate was collected and dried un-
der vacuum. The crude product was purified by chromato-
graphy on a silica gel column using dichloromethane as
eluent. Yield: 1.8 g (79%). White solid. Mp 119–121 ꢀC.
1H NMR (CDCl3): 7.18 (d, J¼8.9 Hz, 4H), 6.88 (d,
J¼8.9 Hz, 4H), 3.94 (t, J¼6.4 Hz, 4H), 3.66 (s, 4H), 1.80
(m, 4H), 1.52 (m, 4H). 13C NMR (CDCl3): 158.80, 129.01,
121.59, 118.18, 115.03, 67.89, 29.07, 25.76, 22.76. IR
(KBr): 2937, 2872, 2245, 1614, 1585, 1514, 1475, 1408,
1254, 1180, 1111, 1028, 820, 804. MS: 348 (M+), 216,
172, 146, 133, 116, 83, 67, 55. Anal. Calcd: C, 75.83; H,
6.94; N, 8.04. Found: C, 75.53; H, 6.20; N, 7.98.
References and notes
1. Burroughes, J. H.; Bradley, D. D. C.; Brown, A. R.; Marks,
R. N.; Mackay, K.; Friend, R. H.; Burns, P. L.; Holmes, A. B.
Nature 1990, 347, 539.
˚
2. Salaneck, W. P.; Lundstrom, I.; Ranby, B. Conjugated Polymers
¨
and Related Materials; Oxford University Press: Oxford, 1993;
pp 65–169.
4.4. General procedure for the preparation of a-cyano-
styryl compounds with spacer group (26–28)
3. Friend, R. H.; Gymer, R. W.; Holmes, A. B.; Burroughes, J. H.;
Marks, R. N.; Taliani, C.; Bradley, D. D. C.; Dos Santos, D. A.;
´
Bredas, J. L.; Logdlund, M.; Salaneck, W. R. Nature 1999, 397,
121.
The model compounds 26–28 were prepared by reacting the
aldehydes (21, 22 or 23) with acetonitrile 25, respectively, by
the same method as model compounds 18–20.
4. Greenham, N. C.; Moratti, S. C.; Bradley, D. D. C.; Friend,
R. H.; Holmes, A. B. Nature 1993, 365, 628.
5. Anderson, S.; Taylor, P. N.; Verschoor, G. L. B. Chem.—Eur. J.
2004, 10, 518.
6. Cho, N. S.; Hwang, D.-H.; Jung, B.-J.; Oh, J.; Chu, H. Y.; Shim,
H.-K. Synth. Met. 2004, 143, 277.
4.4.1. 1,6-Bis[(1,4-di-n-heptyloxyphenyl)-4-b-cyano-
styryloxy]hexane (26). Yield: 76%. Greenish yellow solid.
1
Mp 88–90 ꢀC. H NMR (CDCl3): 7.84 (s, 2H), 7.72 (d,
J¼2.8 Hz, 2H), 7.57 (d, J¼8.9 Hz, 4H), 6.95 (d, J¼9.2 Hz,
4H), 6.90 (d, J¼2.8 Hz, 2H), 6.84 (d, J¼9.15 Hz, 2H),
3.97 (m, 12H), 1.77 (m, 12H), 1.29 (m, 36H), 0.87 (m,
12H). 13C NMR (CDCl3): 159.74, 152.92, 151.72, 135.16,
127.28, 123.81, 118.71, 118.42, 114.86, 113.42, 112.95,
110.69, 69.37, 68.77, 67.98, 31.77, 29.30, 29.13, 29.07,
28.99, 26.10, 26.01, 25.86, 22.60, 22.53, 14.06. IR (KBr):
2930, 2856, 2208, 1607, 1512, 1497, 1470, 1433, 1394,
1296, 1244, 1225, 1186, 1038, 824, 814. MS: 981 (M+).
UV–vis: 330, 374. PL: 493. Anal. Calcd: C, 79.36; H,
9.13; N, 2.99. Found: C, 78.25; H, 9.88; N, 2.81.
7. (a) Oelkrug, D.; Tompert, A.; Gierschner, J.; Egelhaaf, H.-J.;
Hanack, M.; Hohloch, M.; Steinhuber, E. J. Phys. Chem. B
1998, 102, 1902; (b) Lange, F.; Hohnholz, D.; Leuze, M.;
Ryu, H.; Hohloch, M.; Freudenmann, R.; Hanack, M. Synth.
Met. 1999, 101, 652; (c) Behnisch, B.; Martinez-Ruiz, P.;
Schweikart, K.-H.; Hanack, M. Eur. J. Org. Chem. 2000, 2541.
8. Li, J. Y.; Liu, D.; Ma, C. W.; Lengyel, O.; Lee, C.-S.; Tung,
C.-H.; Lee, S. T. Adv. Mater. 2004, 16, 1538.
9. (a) Zheng, M.; Sarker, A. M.; Gurel, E. E.; Lahti, P. M.; Karasz,
¨
F. E. Macromolecules 2000, 33, 7426; (b) Wu, S.-H.; Chen,
J.-H.; Shen, C.-H.; Tsiang, R. C.-C. J. Polym. Sci., Part A:
Polym. Chem. 2004, 42, 6061.
4.4.2. Oligomer (27). Yield: 21%. Orange solid. Mp 175–
10. Haisch, P. A. Ph.D. Dissertation, Universitat Tubingen, 1995.
¨
¨
1
177 ꢀC. H NMR (CDCl3): 7.89 (s, 4H), 7.83 (s, 4H), 7.59
11. Stock, H. T.; Kellogg, R. M. J. Org. Chem. 1996, 61, 3093.
12. Zhang, Y.; Wang, L.; Wada, T.; Sasabe, H. J. Polym. Sci., Part
A: Polym. Chem. 1996, 34, 1359.
13. Lowen, S. V.; Buschek, J.; Mastantuono, R.; Holden, D. A.;
Kovacs, G. J.; Loutfy, R. O. Macromolecules 1990, 23, 3242.
(dd, J1¼2.4 Hz, J2¼8.9 Hz, 8H), 6.96 (dd, J1¼2.1 Hz,
J2¼8.9 Hz, 8H), 4.09 (m, 12H), 3.85 (s, 6H), 1.79 (m,
12H), 1.30 (m, 36H), 0.86 (t, J¼7 Hz, 12H). 13C NMR
(CDCl3): 160.46, 159.99, 151.37, 134.01, 133.91, 127.40,

H. Ryu et al. / Tetrahedron 62 (2006) 6236–6247
6247
14. Kobler, H.; Schuster, K.-H.; Simchen, G. Liebigs Ann. Chem.
1978, 1946.
15. Klingsberg, E. J. Am. Chem. Soc. 1958, 80, 5786.
16. Huisgen, R.; Sauer, J.; Sturm, H. J.; Markgraf, J. H. Chem. Ber.
1960, 93, 2106.
17. Finnegan, W. G.; Henry, R. A.; Lofquist, R. J. Am. Chem. Soc.
1958, 80, 3908.
18. Moratti, S. C.; Cervini, R.; Holmes, A. B.; Baigent, D. R.;
D.; Steinhuber, E.; Spreitzer, H.; Hanack, M. Synth. Met. 1997,
84, 319; (c) Segura, J. L.; Martin, N.; Hanack, M. Eur. J. Org.
Chem. 1999, 643.
`
24. (a) Romero, D. B.; Schaer, M.; Leclere, M.; Ades, D.; Siove,
A.; Zuppiroli, L. Synth. Met. 1996, 80, 271; (b) Zang, C.; von
Seggern, H.; Pakbaz, K.; Kraabel, B.; Schmidt, H.-W.;
Heeger, A. J. Synth. Met. 1994, 62, 35; (c) Gebler, D. D.;
Wang, Y. Z.; Blatchford, J. W.; Jessen, S. W.; Fu, D.-K.;
Swager, T. M.; MacDiarmid, A. G.; Epstein, A. J. Appl.
Phys. Lett. 1997, 7, 1644.
Friend, R. H.; Greenham, N. C.; Gruner, J.; Hamer, P. J.
¨
Synth. Met. 1995, 71, 2117.
19. Rieche, A.; Gross, H.; Hoft, E. Org. Synth., Coll. Vol. 5 1967,
25. Hohnholz, D.; Schweikart, K.-H.; Hanack, M. Adv. Mater.
1999, 11, 646.
26. Onoda, M.; Ohmori, Y.; Kawai, T.; Yoshino, K. Synth. Met.
1995, 71, 2181.
¨
49.
20. Cornil, J.; dos Santos, D. A.; Beljonne, D.; Bredas, J. L. J. Phys.
Chem. 1995, 99, 5604.
´
21. Peng, Z.; Bao, Z.; Galvin, M. E. CHEMTECH 1999, 41.
22. Faraggi, E. Z.; Chayet, H.; Cohen, G.; Neuman, R.; Avny, Y.;
Davidov, D. Adv. Mater. 1995, 7, 742.
27. (a) Samuel, I. D. W.; Rumbles, G.; Collison, C. J.; Friend,
R. H.; Moratti, S. C.; Holmes, A. B. Synth. Met. 1997, 84,
497; (b) Klarner, G.; Lee, J.-I.; Lee, V. Y.; Chan, E.; Chen,
¨
J.-P.; Nelson, A.; Markievicz, D.; Siemens, R.; Scott, J. C.;
Miller, R. D. Chem. Mater. 1999, 11, 1800.
23. (a) Hanack, M.; Segura, J. L.; Spreitzer, H. Adv. Mater. 1996, 8,
663; (b) Hohloch, M.; Segura, J. L.; Dottinger, S. E.; Hohnholz,
¨