Self-assembled liquid crystals formed by hydrogen bonding between non-mesogenic 1,3,4-oxadiazole-based pyridines and substituted benzoic acids

Article abstract of DOI:10.1080/10610278.2011.638378

A series of new supramolecular liquid crystalline complexes have been prepared readily through intermolecular hydrogen bonding between non-mesogenic 1,3,4-oxadiazole-based pyridines and substituted benzoic acids. The liquid crystalline properties of the H

Full text of DOI:10.1080/10610278.2011.638378

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Self-assembled liquid crystals formed by hydrogen
bonding between non-mesogenic 1,3,4-oxadiazole-
based pyridines and substituted benzoic acids
Jie Han a , Qiang Geng a , Wei Chen a , Lirong Zhu b , Qiang Wu b & Qiuchang Wang a
a Department of Chemistry, Nankai Universty, Tianjin, 300071, P.R. China
b Key Laboratory of Functional Polymer Materials of Ministry of Education, Nankai University,
Tianjin, 300071, P.R. China
Version of record first published: 03 Apr 2012.
To cite this article: Jie Han, Qiang Geng, Wei Chen, Lirong Zhu, Qiang Wu & Qiuchang Wang (2012): Self-assembled liquid
crystals formed by hydrogen bonding between non-mesogenic 1,3,4-oxadiazole-based pyridines and substituted benzoic acids,
Supramolecular Chemistry, 24:3, 157-164
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Supramolecular Chemistry
Vol. 24, No. 3, March 2012, 157–164
Self-assembled liquid crystals formed by hydrogen bonding between non-mesogenic
1,3,4-oxadiazole-based pyridines and substituted benzoic acids
Jie Hana*, Qiang Genga, Wei Chena, Lirong Zhub, Qiang Wub* and Qiuchang Wanga
aDepartment of Chemistry, Nankai Universty, Tianjin 300071, P.R. China; bKey Laboratory of Functional Polymer Materials of Ministry
of Education, Nankai University, Tianjin 300071, P.R. China
(Received 4 June 2011; final version received 26 October 2011)
A series of new supramolecular liquid crystalline complexes have been prepared readily through intermolecular hydrogen
bonding between non-mesogenic 1,3,4-oxadiazole-based pyridines and substituted benzoic acids. The liquid crystalline
properties of the H-bonded complexes were studied by infrared spectrometry, polarising optical microscopy, differential
scanning calorimetry and small-angle X-ray scattering. All the H-bonded complexes exhibited liquid crystalline behaviours
with various mesophases such as nematic (N), smectic A and hexagonal columnar mesophases, which are determined by the
electronic nature of terminal groups and the number of alkoxy chains of the H-acceptors and H-donors. The rod-like
H-bonded complexes 2a/3a, 2a/3b and 2a/3c with an electron-withdrawing end group (NO2, F or CN) fascinate to form an
enantiotropic smectic A phase, whereas complex 2a/3d bearing an electron-donating methoxy end group tends to display a
monotropic N phase. In contrast, the disc-shaped complexes 2b/3e and 2c/3e with six peripheral decyloxy chains are room
temperature liquid crystals exhibiting columnar mesophase. All the complexes 2a/3a, 2a/3b, 2a/3c and 2a/3d in CH2Cl2
solutions exhibited an intense broad absorption peak at ca. 303 nm, and emitted a strong blue emission with lmax at ca.
390 nm and good photoluminescence quantum yields (FFL ¼ 0.56–0.81).
Keywords: molecular self-assembly; liquid crystal; 1,3,4-oxadiazole
1. Introduction
behaviours with various mesophases (4), but also may be
used as emissive materials and electron-transporting
materials in organic light-emitting devices due to their
electron deficiency, high photoluminescence quantum
yield and good thermal/chemical stabilities (5). With the
research being developed intensively, the molecular
structures of new 1,3,4-oxadiazole-based liquid crystalline
compounds become more and more complicated, and the
synthetic route becomes more and more longer. As a result,
it would be difficult to devise and synthesise new liquid
crystalline 1,3,4-oxadiazoles. On the other hand, the self-
assembly through hydrogen bonding had provided a simple
and efficient approach to form such kinds of liquid
crystalline materials (6). Martin and Bruce (6a) first
reported two series of H-bonded complexes consisted of
1,3,4-oxadiazole-based pyridines and benzoic acids, and
found that all the materials displayed nematic (N) and
smectic A (SmA) phases. Very recently, Vieira and co-
workers (6b) have prepared five asymmetric V-shaped
acids derived from 1,3,4-oxadiazole, which were used to
form H-bonded liquid crystallines exhibiting rectangular
and hexagonal columnar (Colh) mesophases at room
temperature. In this work, a series of new 1,3,4-oxadiazole-
based H-acceptors 2a–2c were synthesised and used to
´
Ever since the pioneering reports of Kato and Frechet (1),
the hydrogen bonding between appropriate carboxyl and
pyridyl groups has become one of the most common non-
covalent interactions to generate supramolecular liquid
crystals (2). The most important advantage of this
approach is that the complex structures can be obtained
simply and spontaneously through a molecular self-
assembly process driven by hydrogen bonding, and the
nature of mesophases as well as the molecular shapes of
the H-bonded liquid crystals may be modulated by
selection of appropriate H-donor and H-acceptor. Another
particularly attractive possibility is that both the H-donor
and H-acceptor themselves may not have liquid crystal
properties, whereas the as-formed complexes through non-
covalent hydrogen bonding exhibit stable mesophases (3).
Moreover, the H-donors and H-acceptors used in the
formation of hydrogen-bonded liquid crystals are often
commercially available or can be prepared readily through
a very short synthetic route compared with the covalent
liquid crystalline compounds.
In recent years, the 1,3,4-oxadiazole-based liquid
crystals have been paid much attention, because such kinds
of compounds can not only exhibit liquid crystalline
*Corresponding authors. Email: hanjie@nankai.edu.cn; sorp@nankai.edu.cn
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2011.638378
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158
J. Han et al.
O
C10H21
O
N
2a
2b
HOOC
R
N N
C10H21
O
3a: R = NO2; 3b: R = F;
3c: R = CN; 3d: CH3O.
O
C10H21
O
N
N N
OC10H21
C10H21
O
OC10H21
OC10H21
HOOC
C10H21
O
O
C10H21
O
N
2c
N N
3e
C10H21
O
Cl
Figure 1. Structures of the H-acceptors and H-donors.
form supramolecular complexes with substituted benzoic
acids 3a–3e (Figure 1). Although all the H-acceptors and
H-donors are non-mesogenic compounds, all the H-bonded
complexes exhibit liquid crystalline behaviours with
various mesophases such as N, SmA and Colh mesophases,
which can be tuned by the electronic factor of the
substitutions and the number of alkoxy chains on the
H-donors and H-acceptors.
2. Results and discussion
2.1 Synthesis
The synthetic route for the H-bonded liquid crystalline
complexes is shown in Scheme 1. The H-acceptor 2a was
prepared through two-step reactions. Isonicotinic acid was
refluxed with excessive thionyl chloride to give the
corresponding isonicotinic acid chloride, and then
treated with p-decyloxybenzoyl hydrazine to afford
O
O
SOCl2
i) SOCl2
H H
C10H21
O
C N N C
N
N
COOH
O
C
ii) H2NHN
OC10H21
1a
O
C
N N
N N
3a–3d
R
C10H21O
N
C10H21
O
H O
N
O
THF
O
2a
2a/3a; 2a/3b; 2a/3c; 2a/3d
C
10H21
O
i) SOCl2
O
O
H H
N
COOH
C10H21
O
C N N C
N
OC10H21
OC10H21
O
C10H21
O
1b
ii) H2NHN C
OC10H21
OC10H21
C10H21
O
C
10H21
O
O
C
N N
POCl3
N N
O
3e
OC10H21
C10H21
O
N
C10H21
O
N
H O
THF
O
OC10H21
OC10H21
C10H21
O
C10H21
O
2b
2b/3e
C10H21
O
C10H21
O
O
C
N N
O
SOCl2
N N
O
3e
OC10H21
OC10H21
C10H21
O
N
C10H21
O
N
H O
THF
C10H21
O
Cl
C10H21
O
Cl
2c
2c/3e
Scheme 1. Synthetic route for the hydrogen-bonded liquid crystalline complexes.

Supramolecular Chemistry
159
intermediate 1a, which underwent a cyclisation reaction
with thionyl chloride to provide 2a with a total yield of
65% for the two-step reactions. However, no compound 2b
as expected was obtained in the cyclisation reaction of 1b
with thionyl chloride under the same reaction conditions,
which afforded a new compound 2c with a chloro
substitution as the only product. The reaction mechanism
in which thionyl chloride acts as a chlorinating agent (7) to
yield 2c is not well understood. One possible explanation
is that thionyl chloride undergoes oxidation in the presence
of atmospheric oxygen to sulphuryl chloride (8) which
may work as an electrophilic agent for aromatic
compounds, especially for those with electron-donating
groups. When thionyl chloride was replaced by POCl3 in
the cyclisation reaction, the desired H-acceptor 2b was
smoothly obtained in good yield. The supramolecular
liquid crystalline complexes were prepared according to a
standard method (1), which was carried out by dissolving
equimolecular proportions of the H-acceptor and the
appropriate H-donor in tetrahydrofuran (THF), and then
removing the solvent to afford the H-bonded complexes.
which is attributed to the stretching band of the hydroxyl
group involving the H-bonded dimer and the Fermi
resonances. As for complex 2a/3a, the OZH stretching
band and its Fermi resonance appear at 2444 and
1947 cm21, respectively, and the broad band around
930 cm21, which are attributed to the out-plane defor-
mation vibration dOH of the dimer of 4-nitrobenzoic acid
3a involving the H-bond of carboxylic acid, disappeared
simultaneously. Moreover, the bands at 1429 and
1323 cm21 of the group CZOZH in-plane bending
vibration in 4-nitrobenzoic acid 3a were removed to
lower frequencies in the H-bonded complex 2a/3a, which
implied that the CZOZH in-plane bending vibration of
complex 2a/3a was slightly restricted. These changes
confirmed the formation of the H-bond complex 2a/3a
instead of mixture 2a/3a in this work. In addition, the
carbonyl band at 1692 cm21 in 4-nitrobenzoic acid 3a was
shifted to 1702 cm21 in the H-bonded complex 2a/3a,
and the nitro group bands at 1542 and 1351 cm21 in
4-nitrobenzoic acid 3a were shifted to 1523 and
1344 cm21, respectively. These suggested that the
carbonyl stretching vibration in the H-bonded complex
2a/3a was more relaxed than that in 4-nitrobenzoic acid
3a. But the nitro group in the H-bonded complex was just
reversed. For the 1,3,4-oxadiazole-based pyridine 2a part,
there were less obvious changes to be observed in the
H-bonded complex.
2.2 FT-IR spectroscopic analysis
The formation of H-bonded interactions in all the
complexes was investigated by FT-IR spectroscopy at
room temperature in the solid state at first. Complex 2a/3a
was taken as an example to describe the formation of the
H-bonded complexes. As seen in Figure 2, 4-nitrobenzoic
Then, the variable temperature IR spectra of the
H-bonded complexes were also recorded in different phase
states. Several spectra of the H-bonded complex 2a/3a at
acid 3a showed a broad band from 2300 to 2750 cm21
,
3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400 1200 1000 800
Wavenumber (cm–1
)
Figure 2. FT-IR spectra of the 4-nitrobenzoic acid 3a (top), 1,3,4-oxadiazole-based pyridine 2a (middle) and H-bonded complex 2a/3a
(bottom).

160
J. Han et al.
of the complex could be gradually weakened when
temperature was increased, thus the carbonyl group
vibration could be more free and the nitro group more
crowded in 4-nitrobenzoic acid 3a part.
Table 1. Phase transition temperatures and enthalpy changes for
the H-bonded complexes (data obtained by DSC in the first
heating and cooling runs).
Complex
Phase transitions T (8C) [DH (kJ mol21)]
2a/3a
Cr 136.2 (17.0) SmA 145.4 (7.2) Iso
Iso 143.5 (27.9) SmA 122.4
SmX 118.4 (218.7)a Cr
2.3 Liquid crystalline properties
2a/3b
2a/3c
Cr 110.8 (19.0) SmA 118.7 (9.2) Iso
Iso 116.7 (29.6) SmA 106.7 (218.7) Cr
Cr1 117.9 (15.7) SmA 132.2 (4.6) Iso
Iso 129.8 (24.5) SmA 115.0 (29.7)
Cr2 98.0 (25.5) Cr2
The thermal and liquid crystalline behaviours of all
H-bonded complexes were investigated by polarising
optical microscopy (POM) and differential scanning
calorimetry (DSC). Although all the H-bonding donors
and acceptors used in this study are themselves non-
mesogenic, all of the H-bonded complexes exhibit
thermotropic liquid crystalline behaviours. The results of
the POM observations are in good agreement with the
corresponding DSC thermograms. Selected optical micro-
graphs are shown in Figure 4, and the phase transition
temperatures as well as the associated enthalpy changes
are listed in Table 1.
2a/3d
2b/3e
2c/3e
Cr 104.0 (32.2) Iso
Iso 102.4 (20.9) N 97.7 (224.0) Cr
Cr 41.9 (62.4) Colh 46.1 (4.3) Iso
Iso 43.6 (24.4) Colh 21.8 (272.5) Cr
Cr 39.2 (65.0)
Iso 33.4 (24.6) Colx 20.8 (270.0)
Note: Cr, crystal; N, nematic; SmA, smectic A; SmX, unidentified smectic
mesophase; Colh, hexagonal columnar; Colx, unidentified columnar mesophase; Iso,
isotropic.
a
The total enthalpies of SmA to SmX and SmX to Cr.
Complexes 2a/3a, 2a/3b and 2a/3c all gave rise to an
enantiotropic smectic A phase, which was identified by
the typical fan-shaped texture observed under POM
(Figure 4(a),(b)). In addition, complex 2a/3a exhibited an
unidentified smectic X mesophase with a very narrow
temperature range only in the cooling run. In contrast, the
solid sample of complex 2a/3d melts directly into isotropic
liquid upon heating cycle, which changed gradually into
birefringent drops and then a schlieren texture (Figure 4(c))
in the cooling cycle, indicating that complex 2a/3d
displayed a monotropic N phase. The only difference in
structures of these rod-like complexes is that they have
different terminal groups, so the different liquid crystalline
properties are determined solely by the terminal groups.
specific temperature according to Table 1 are illustrated in
Figure 3. Generally, it was able to confirm that the structure
of the H-bonded complexes would not be destroyed in the
temperature region performed in this work, because the
specific absorbance bands of the H-bonded complex 2a/3a
were retained, whereas only the positions were shifted.
The most remarkable shift was the carbonyl stretching
vibration of the H-bonded complex 2a/3a which was
shifted from 1702 cm21 at 1008C to 1723 cm21 at 1558C.
Considering the opposite shift direction of the nitro group
band at 1522 cm21 and the changes of other bands in the
same temperature region, it was concluded that the H-bond
155°C
138°C
120°C
100°C
3400
3200
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
Wavenumber (cm–1
)
Figure 3. FT-IR spectra of H-bonded complex 2a/3a at specific temperature.

Supramolecular Chemistry
161
Figure 4. Optical micrographs (magnification: £ 200) on cooling cycle of (a) the smectic A mesophase of fan-shaped and focal texture
for 2a/3a at 141.78C; (b) the smectic A mesophase of fan-shaped texture for 2a/3b at 111.38C; (c) the N schlieren texture for 2a/3d at
101.58C; (d) the Colh mesophase of 2c/3e at 468C.
The strong electron-withdrawing nitro (for 2a/3a), fluoro
(for 2a/3b) or cyano group (for 2a/3c) may create dipoles
across the molecular axis and fascinate to form
enantiotropic smectic A phase in the corresponding
complexes. In contrast, complex 2a/3d, with an electron-
donating CH3O group, is tended to exhibit N mesophase,
which is likely attributed to the freely rotating methoxy
group. The effect of the terminal groups on liquid
crystalline properties has been ever reported in the
covalent-bonded 1,3,4-oxadiazole derivatives (9).
of small-angle X-ray scattering (SAXS). As shown in
Figure 6, the SAXS pattern of 2b/3e consists of a sharp
strong peak and a weak diffraction peak in the low-angle
region, which may be assigned to the (100) and (110)
reflections of a 2D hexagonal lattice with a reciprocal
spacing ratio of ca. 1:1/31/2, suggesting the presence of a
Colh arrangement (11). On the basis of the results of POM,
DSC and SAXS, the mesophase of complex 2b/3e may be
assigned to a Colh phase. Compared to the enantiotropic
Complexes 2b/3e and 2c/3e have six peripheral
n-decyloxy chains and adopt a disc-like shape, which
make them show different mesomorphic behaviours from
those of the rod-like complexes mentioned above.
According to the POM observations as shown in Figure
4(d), complex 2b/3e exhibits a mosaic-like texture with
dark area, which is characteristic to a Colh mesophase (10).
The POM observations are well consistent with the DSC
thermograms. As seen in Figure 5, the DSC curves of 2b/3e
showed two clear-cut transitions on both heating and
cooling runs. In the heating thermogram, the larger peak
area at 41.98C is due to the crystal–Colh phase transition,
and the relatively small peak area at 46.18C is attributed to
the Colh–isotropic transition. The correponding peaks in
the cooling run may also be reasonably assigned as the
isotropic–Colh (43.68C) and Colh–crystal (21.88C) tran-
sitions, respectively. The liquid crystal behaviours of a non-
aligned sample of 2b/3e were further investigated by means
2
41.9°C
Second heating
First cooling
46.1°C
0
43.6°C
–2
21.8°C
20
40
T/°C
60
Figure 5. DSC curves of 2b/3e in the second heating and the
first cooling run.

162
J. Han et al.
at ca. 390 nm and good photoluminescence quantum yields
8
6
4
2
0
(FFL ¼ 0.56–0.81). It is noted that all the photolumines-
cence spectra peak shapes were quite similar to each other,
indicating that the intermolecular H-bonded interaction
between pyridine 2a and benzoic acids 3a–3d has little
effect on the electronic structure of the 1,3,4-oxadiazole
chromophore. Similar observations in H-bonded liquid
crystals were also found by Vieira et al. (6b).
(100)
I
(110)
3. Conclusion
2
4
6
8
10
In summary, a series of new supramolecular liquid
crystals have been prepared simply by the association of
non-mesogenic benzoic acid derivatives and 1,3,4-
oxadiazole-based pyridines through intermolecular hydro-
gen bonding. The liquid crystalline properties of the H-
bonded complexes can be tuned by the electronic property
of the substitutions and the number of alkoxy chains on
the H-donors and H-acceptors. The rod-like H-bonded
complexes 2a/3a, 2a/3b and 2a/3c with a terminal
electron-drawing group tend to form an enantiotropic
smectic A phase, whereas 2a/3d exhibits a monotropic N
phase due to the terminal methoxy group. In contrast, the
disc-shaped H-bonded complexes 2b/3e and 2c/3e both
exhibit columnar mesophases at room temperature
regime.
2q/ 0
Figure 6. SAXS pattern of 2b/3e at 258C during the first cooling
run from the isotropic liquid.
liquid crystalline behaviour of 2b/3e, the analogous
complex 2c/3e displays a monotropic columnar mesophase
with relatively narrow temperature range due to the lateral
chloro atom on the benzene ring, which is consistent with
the common rule that a lateral substitutent may lower both
the melting and clearing temperatures by broadening
and/or twisting the core of the mesogen, and the
mesophases can show a decrease in temperature range or
even disappear (12).
4. Experimental section
2.4 Electronic absorption and emission spectroscopy
4.1 General
The UV–vis absorption and emission spectra for the
complexes 2a/3a, 2a/3b, 2a/3c and 2a/3d in CH2Cl2
solutions are presented in Figure 7. All these complexes
exhibited a similar absorption pattern with an intense broad
absorption peak at ca. 303 nm, which is assigned to the p–
Melting points were determined on an X-4 digital melting
point apparatus with thermometer and are uncorrected.
1
Solution H and 13C NMR spectra were recorded on a
Bruker AV400 spectrometer and the chemical shifts were
quoted in parts per million (ppm) relative to tetramethyl-
silane as an internal standard. Electrospray ionisation
(ESI) mass spectra were recorded on a Finnigan LCQ
Advantage spectrometer. The liquid crystalline behaviours
p
transition typical for the heterocyclic 1,3,4-oxadiazole
*
moiety due to the high molar absorption coefficients
measured (1 ¼ 3.9–5.4 £ 103 mol21 cm21). Similarly, all
the complexes displayed a strong blue emission with lmax
(a)
(b)
250
200
150
100
50
2a/3c
0.4
2a/3b
2a/3a
2a/3c
2a/3b
2a/3a
2a/3d
2a/3d
0.2
0
0.0
300
400
350 400 450 500 550 600
Wavelength (nm)
Wavelength (nm)
Figure 7. Normalised absorption and emission spectra of complexes 2a/3a, 2a/3b, 2a/3c and 2a/3d in CH2Cl2 at room temperature.

Supramolecular Chemistry
163
were investigated by polarised-light optical microscopy
(OLYMPUS BX51) equipped with a temperature-con-
trolled hot stage. Samples were sandwiched between
untreated glass slides and viewed through crossed
polariser. Thermal analyses of the final products were
studied by a NETZSCH DSC 204 DSC with a heating rate
of 108C/min and pre-calibrated with indium standard.
UV–vis absorption spectra of the H-bonded complexes in
dichloromethane (c ¼ 1 £ 1025 M) were recorded with a
Cary 300 Conc UV–vis spectrophotometer. Steady-state
emission spectra were recorded with a Cary Eclipse
fluorescence spectrophotometer. The emission quantum
yields were determined using 2-(4-methoxyphenyl)-5-(4-
decyloxyphenyl)-1,3,4-oxadiazole in degassed CH2Cl2 as
a standard reference solution (F ¼ 0.83) (4f). Infrared
spectrometry was performed using a Bio-Rad FTS-6000
spectrometer, which equipped a UMA-500 microscope
with a Linkam FTIR600 heating and cooling stage. Each
sample was pressed in two KBr windows after melting
over the clearing point on the heating stage and was cooled
down to room temperature before infrared spectra were
recorded. The variable-temperature infrared spectrum was
recorded on the microscope with an MCT detector at a
resolution of 8 cm21 with 16 scans. The spectrometer was
operated with 5 KHz electrical filter at 10 KHz scan speed.
SAXS experiments were carried out using SAXS
equipment with a 2D detector (Bruker AXS GmbH,
Karlsruhe, Germany) and were operated at 40 kV and
35 mA. The wavelength of the incident X-ray beam from
Cu Ka radiation was l ¼ 0.154 nm. The distance between
the sample and the detector was 27.15 cm, which was
calibrated by Silver behenate. The sample was held in a
glass capillary (ca. 1 mm diameter) and heated with a
variable-temperature attachment.
round-bottomed flask were added 1a (4 g, 10 mmol) and
SOCl2 (25 ml), and the reaction mixture was refluxed for
8 h, then the excessive thionyl chloride was removed under
reduced pressure. The residual was dissolved in chloro-
form and washed with dilute solution of sodium hydroxide
and brine, and then dried over MgSO4. The crude product
was purified by column chromatography (silica gel, eluent
EtOAc–CH2Cl2 ¼ 1:2) to afford parent pyridine 2a as
white solids, 2.5 g yield 65%. (Cr· · ·94.5 [47.8]· · ·Iso 74.8
[227.0]· · ·Cr: transition enthalpies (kJ mol21) in square
1
brackets); H NMR (400 M, CDCl3): 8.84 (d, J ¼ 4.2 Hz,
2H, Ar-H), 8.08 (d, J ¼ 8.7 Hz, 2H, Ar-H), 7.99 (d,
J ¼ 4.8 Hz, 2H, Ar-H), 7.03 (d, J ¼ 8.7 Hz, 2H, Ar-H),
4.05 (t, J ¼ 6.6 Hz, 2H, OCH2), 1.85 (m, 2H, OCH2CH2),
1.56–1.29 (m, 14H, OCH2CH2(CH2)6CH3), 0.89 (t,
J ¼ 6.6 Hz, 3H, CH3). 13C NMR (100 MHz, CDCl3): d
in ppm 165.55, 162.45, 162.27, 150.86, 131.22, 128.96,
120.23, 115.49, 115.14, 68.38, 31.89, 29.55, 29.36, 29.32,
29.11, 25.99, 22.68, 14.112. MS-ESI: 380.8 ([M þ 1]þ).
HR-MS (þcESI), calcd for C23H29N3O2 379.2259, found
380.2328 ([M þ H]þ).
4.1.2 Synthesis of 2-(4-pyridyl)-5-(3,4,5-
tridecyloxy)phenyl-1,3,4-oxadiazole 2b
This compound was prepared according to the same
procedure as that for 2a by replacement of SOCl2 with
POCl3. Yellow solid, 590 mg; yield, 61%. m.p.: 24–258C.
1H NMR (400 MHz, CDCl3): 8.86 (d, J ¼ 4.8 Hz, 2H, Ar-
H), 8.02 (d, J ¼ 4.8 Hz, 2H, Ar-H), 7.44 (s, 2H, Ar-H),
4.10 (m, 6H, OCH2), 1.90–1.75 (m, 6H, OCH2CH2),
1.55–1.45 (m, 6H, OCH2CH2CH2), 1.42–1.25 (m, 36H,
OCH2CH2CH2(CH2)6CH3), 0.90 (t, J ¼ 6.2 Hz, 9H, CH3).
13C-{1H}-NMR (CDCl3): 165.7, 162.6, 153.7, 150.9,
141.9, 131.1, 120.3, 117.8, 105.7, 73.7, 69.5, 31.9, 30.4,
29.7, 29.6, 29.1, 26.1, 22.7, 14.1. MS-ESI: ([M þ 1]þ):
692.6. HR-MS (þcESI), calcd for C43H69N3O4: 692.5361;
found: 692.5364 ([M þ 1]þ).
p-Decyloxybenzoyl hydrazine and 3,4,5-tridecyloxy-
benzoyl hydrazine were prepared according to the
literature procedure (13). All other chemicals were
commercially available and used as received.
4.1.1 Synthesis of 2-(4-pyridyl)-5-(4-decyloxy) phenyl-1,
3,4-oxadiazole 2a
4.1.3 Synthesis of 2-(4-pyridyl)-5-(2-chloro-3,4,5-
tridecyloxy)phenyl-1,3,4-oxadiazole 2c
The mixture of isonicotinic acid (3 g, 24 mmol) and
thionyl chloride (10 ml) dissolved in 10 ml of dry benzene
was refluxed for 2 h, then the excessive thionyl chloride
and benzene were removed under reduced pressure to
give the isonicotinic acid chloride, which was added
to a solution of p-decyloxybenzoyl hydrazine (6.4 g,
22.0 mmol) in pyridine (40 ml). The resultant mixture was
stirred at room temperature for 12 h and then at 708C for
another 2 h. After the excessive SOCl2 was distilled off,
the reaction mixture was poured into 100 ml of cold water.
The precipitate was collected by filtration and washed with
ethanol to afford hydrozide 1a, which was used directly to
the next step reaction without further purification. To a
This compound was prepared according to the same
procedure as that for 2a. Yellow solids, 661 mg, yield:
1
65%. m.p.: 20–228C. H NMR (400 MHz, CDCl3): 8.85
(d, J ¼ 6.0 Hz, 2H, Ar-H), 8.00 (d, J ¼ 6.0 Hz, 2H, Ar-H),
7.42 (s, 2H, Ar-H), 4.08 (m, 6H, OCH2), 1.89–1.75 (m,
6H, OCH2CH2), 1.55–1.42 (m, 6H, OCH2CH2CH2),
1.40–1.20 (m, 36H, OCH2CH2CH2(CH2)6CH3), 0.88 (t,
J ¼ 6.4 Hz, 9H, CH3). 13C-{1H}-NMR (CDCl3): 164.5,
163.2, 152.2, 150.9, 150.7, 146.3, 131.0, 120.4, 117.4,
110.0, 69.4, 31.9, 30.3, 29.6, 29.5, 29.3, 29.2, 26.0, 22.7,
14.1. MS-ESI: ([M þ 1]þ): 726.6. HR-MS (þcESI): calcd
for C43H68ClN3O4: 726.4970; found: 726.4996
([M þ 1]þ).

164
J. Han et al.
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Zhang, F.-Y.; Zhu, L.-R. Liq. Cryst. 2010, 37, 1521–1527.
(d) Han, J.; Zhang, M.; Wang, F.-L.; Geng, Q. Liq. Cryst.
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4.1.4 Preparation of hydrogen-bonded complexes
Hydrogen-bonded complexes were prepared by dissolving
the stoichiometric amount of H-bonded donor and
acceptor moieties in freshly distilled THF. The solution
was stirred for 3 h at room temperature, and the solvent
was evaporated under reduced pressure. The resulting
solid was dried in vacuo for 24 h.
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Acknowledgement
This work was financially supported by grants from Open Project
of State Key Laboratory of Supramolecular Structure and
Materials (SKLSSM201113).
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