Columnar mesophases and phase behaviors of novel polycatenar mesogens containing bi-1,3,4-oxadiazole

Article abstract of DOI:10.1016/j.tet.2007.09.028

A new series of liquid-crystalline bi-1,3,4-oxadiazole derivatives (2,2′-bis(3,4,5-trialkoxyphenyl)-bi-1,3,4-oxadiazole, BOXD-Tn, n=3, 4, 5, 6, 7, 8, 10, 14) were designed and synthesized. They have been confirmed to give rise to columnar mesophases. The

Full text of DOI:10.1016/j.tet.2007.09.028

Tetrahedron 63 (2007) 12429–12436
Columnar mesophases and phase behaviors of novel
polycatenar mesogens containing bi-1,3,4-oxadiazole
*
Songnan Qu and Min Li
Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, Institute of Materials Science and Engineering,
10 Qianwei road, Jilin University, Changchun 130012, PR China
Received 22 July 2007; revised 12 September 2007; accepted 14 September 2007
Available online 22 September 2007
Abstract—A new series of liquid-crystalline bi-1,3,4-oxadiazole derivatives (2,20-bis(3,4,5-trialkoxyphenyl)-bi-1,3,4-oxadiazole,
BOXD-Tn, n¼3, 4, 5, 6, 7, 8, 10, 14) were designed and synthesized. They have been confirmed to give rise to columnar mesophases.
The columnar mesophases for BOXD-Tn (n¼5, 6, 7, 8, 10) could be supercooled to ꢀ20 ꢁC on the cooling runs. A room temperature Colho
phase was obtained for BOXD-T14. All BOXD-Tn exhibit good fluorescence properties either in cyclohexane or in solid state.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
columnar structures have attracted increasing attention
because the overlapping of p-orbitals results in one-
dimensional semiconductors with a better performance
than conjugated polymers.5 Most of the reported meso-
morphic 1,3,4-oxadiazole derivatives were generally rod-
like molecules6 exhibiting nematic/smectic phase. For
example, 2,5-hexyloxybiphenyl-hexyloxyphenyl-oxadiazole
(HOBP-OXD) exhibited smectic phases and high electron
mobility (over 10ꢀ3 cm2/V/s) was found in its high-ordered
smectic phase.6d In contrast, columnar 1,3,4-oxadiazole
derivatives were relatively limited. A star-shaped discotic
molecule containing 1,3,5-triethynylbenzene and oxadia-
zole-based rigid arms was reported to exhibit a discotic ne-
matic phase (NCol).7 Marder et al. reported that discotic
molecules with benzene or triazine cores and three (trialkox-
yaryl) oxadiazole arms exhibited columnar mesophases and
demonstrated that these materials may find applications in
organic electronics.8 Lai et al. reported that 2,5-bis(3,4,5-
trialkoxy phenyl)-1,3,4-oxadiazoles exhibited hexagonal
columnar phases (Colh), while their complexes with metals,
Colr and Colh.9
Organic semiconducting materials with high carrier mobili-
ties are desirable for various electronic applications in-
cluding light-emitting diodes, solar cells, and field-effect
transistors. However, most of the organic compounds known
for optoelectronic applications still present some major
limitations such as low electron conductivity and/or low lu-
minescence efficiency. 1,3,4-Oxadiazoles derivatives have
enjoyed widespread use as electron-transporting/hole block-
ing (ETHB) materials, emitting layers in electroluminescent
diodes or for non-linear optical process, due to the electron-
deficient nature of the heterocycle, high photoluminescence
quantum yield, and good thermal, and chemical stabilities.1
Non-mesomorphic 2,5-bis(4-naphthyl)-1,3,4-oxadiazole2
has been demonstrated as one of the best organic electron
conductors, and several oxadiazole-based compounds have
been recently used as electron transport materials in organic
light-emitting diodes (OLEDs).3
Liquid-crystalline materials, which present self-organizing
ability, fluidity, and the ease of defect-free orientation with
special treatment, have been recently recognized to have
great advantages in manipulation of optimized high-
efficiency organic electro-optic devices.4 Materials with
columnar mesophases in which molecules self-assemble to
Our present work aimed at developing new liquid-crystalline
1,3,4-oxadiazole derivatives, e.g., 2,20-bis(3,4,5-trialkoxy-
phenyl)-bi-1,3,4-oxadiazole, BOXD-Tn, n¼3, 4, 5, 6, 7, 8,
10, 14. They have been confirmed to give rise to columnar
mesophases. The columnar mesophases of BOXD-Tn
(n¼5, 6, 7, 8, 10) could be supercooled to low temperature
(ꢀ20 ꢁC) due to their slow crystallization. A room tempera-
ture ordered columnar phase was identified for BOXD-T14.
All the compounds exhibit good fluorescence properties
either in cyclohexane or in bulk.
Keywords: 1,3,4-Oxadiazole; Liquid crystals; Columnar mesophases; Fluo-
rescence.
* Corresponding author. Tel.: +86 431 85168254; e-mail: minli@mail.jlu.
edu.cn
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.09.028

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S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
2. Results and discussion
2.2. Mesomorphic properties
2.1. Synthesis
The phase transition temperatures and transition enthalpies
for BOXD-Tn (n¼3, 4, 5, 6, 7, 8, 10, 14) are summarized
in Table 1. It can be seen that the mesophase behaviors are
greatly affected by the length of the terminal chains.
BOXD-T3 and BOXD-T4 are non-mesomorphic perhaps
due to the shorter terminal alkoxy groups, which cause the
higher melting point and thus suppress the LC phase. On
the other hand, BOXD-Tn (n¼5, 6, 7, 8, 10, 14) with
longer alkoxyl terminal groups exhibited columnar phases
as confirmed by polarizing microscopy, calorimetry, and
X-ray diffraction investigations.
Ethyl 3,4,5-trihydroxy benzoate, oxalyl chloride, and 1-bro-
mide alkane were used as received. 3,4,5-Trialkoxy-benzoyl
hydrazines 2 were prepared according to the literature.8
Tetrahydrofuran (THF) was refluxed over sodium under
argon and distilled before use. Scheme 1 shows the synthetic
route for BOXD-Tn. Anhydrous K2CO3 (30 g) and ethyl
3,4,5-trihydroxy benzoate (5.4 mmol) were added to a de-
oxygenated mixture of DMF (100 mL) and of 1-bromide
alkane (18.1 mmol) under nitrogen. The mixture was heated
at 80 ꢁC for 6 h. The reaction mixture was cooled to room
temperature, water (500 mL) was added, and the product
was extracted with diethyl ether. The extractive solution
was washed with water and dried over MgSO4. After filtra-
tion, the solvent was evaporated under reduced pressure, and
the crude product was purified through a column of silica gel
using 2% ethyl acetate in hexane as eluent to afford 1. A
solution of 1 (19.2 mmol) and excess hydrazine mono-
hydrate in ethanol (180 mL) was refluxed for 40 h. Water
(100 mL) was added and the resulting precipitate was
collected, dried under vacuum, and recrystallized from
ethanol/water to give pure 2. Oxalyl chloride (11.2 mmol)
was regularly injected into the THF solution of 3,4,5-tri-
alkoxy-benzoyl hydrazine 2 (23.1 mmol) under vigorous
stirring at room temperature for 8 h. The resulted products
of oxalyl acid N0,N0-di(3,4,5-trialkoxylbenzoyl)-hydrazide
3 were purified by recrystallizing from alcohol. The purified
3 was dissolved in phosphorous oxychloride (POCl3) and
refluxed for about 40 h. Excess POCl3 was removed through
distillation and the residue was slowly added into icewater.
After the removal of solvent under reduced pressure, the
crude products were further purified through a column of
silica gel using 2% ethyl acetate in chloroform as eluent to
afford BOXD-Tn.
Figures 1 and 2 show the DSC thermograms of BOXD-Tn
(n¼5, 6, 7, 8, 10, 14) on the first heating and cooling runs
at a scanning rate of 10 ꢁC/min. BOXD-T5 exhibited mono-
tropic mesophases, while others with longer terminal chains
exhibited enantiotropic mesophases. It should be mentioned
that no crystallization was observed for BOXD-Tn (n¼5, 6,
7, 8, 10, 14) even when they were cooled to ꢀ20 ꢁC at cool-
ing rate of 10 ꢁC/min. On subsequent heating (10 ꢁC/min),
the phase transition sequences of BOXD-Tn (n¼6, 7, 8,
10, 14) were reversible, while complex thermal behaviors
were observed for BOXD-T5 (Fig. 3). Upon heating
BOXD-T5 at 10 ꢁC/min, an exothermic process between
56 ꢁC and 74 ꢁC, which was partially overlapped with
the endothermic peak centered at 67.8 ꢁC, followed by an
endothermic peak centered at 77.1 ꢁC (13.8 kJ/mol) was
observed (Fig. 3f). In contrast, this exothermic process
shifted to lower temperature, e.g., between 47 ꢁC and
63 ꢁC with the heat of 26.19 kJ/mol at 2 ꢁC/min and the
high-temperature endothermic peak centered at 74.7 ꢁC
(36.36 kJ/mol), which was assigned to the crystalline–iso-
tropic transition similar to that in its first heating run
(Fig. 3g), indicating that crystallization of BOXD-T5 took
place during heating the mesophase. The lower the heating
rates, the lower the crystallization temperature and the
higher the enthalpic changes, suggesting its kinetic-con-
trolled feature of the crystallization. The endothermic peak
at 67 ꢁC corresponding to mesophase to isotropic transition
HO
O
C
HO
HO
OCH2CH3
+
RBr
RO
RO
O
C
K2CO3, DMF
80 °C, 6 hrs
OCH2CH3
Table 1. Phase transition temperatures (T/ꢁC) and enthalpies (DH/kJ/mol in
brackets) of BOXD-Tn (n¼3, 4, 5, 6, 7, 8, 10, 14) on the first heating and
cooling runsa
RO
1
RO
RO
O
hydrazide hydrate, EtOH
reflux 40 hrs
C
NHNH2
Compound
Heating
182.3 (38.9) I–Cr
Cooling
175.9 (37.8)
RO
2
BOXD-T3
BOXD-T4
BOXD-T5
Cr–I
Cr–I
O O
C C Cl
THF
139.8 (43.9) I–Cr
Colr–ColL
76.7 (39.4) I–ColL
122.8 (42.9)
23.2 (0.74)
63.8 (4.23)
9.0 (0.3)
RO
RO
Cl
,
OR
OR
OR
H
O
C
O
C
H
N
N
Cr–I
C
O
C
O
N
H
N
H
r.t., 8 hrs
BOXD-T6
BOXD-T7
BOXD-T8
Cr–ColL
ColL–I
Cr–ColL
ColL–I
Cr–ColL
ColL–I
69.0 (50.8) ColL–Colr
RO
RO
73.2 (3.8)
67.3 (54.2)
77.7 (4.9)
67.3 (57.1)
83.5 (4.4)
36.4 (5.8)
60.6 (64.9)
83.5 (4.9)
I–ColL
I–ColL
I–ColL
70.8 (3.8)
3
OR
OR
OR
76.1 (4.5)
81.1 (4.2)
N
N
POCl3
O
RO
RO
reflux 40 hrs
O
N
N
BOXD-T10 Cr1–Cr2
Cr2–ColL
ColL–I
BOXD-Tn
BOXD-T3:R= -(CH2)2CH3
BOXD-T5: R= -(CH2)4CH3
BOXD-T7: R= -(CH2)6CH3
I–ColL
ColII–Colho
ColI–ColII
79.8 (4.8)
17.3 (15.2)
23.1 (5.6)
26.2 (28.9)
77.7 (5.3)
BOXD-T4: R= -(CH2)3CH3
BOXD-T6: R= -(CH2)5CH3
BOXD-T8: R= -(CH2)7CH3
BOXD-T14: R= -(CH2)13CH3
BOXD-T14
Cr–ColL
ColL–I
68.6 (97.3) ColL–ColI
80.9 (5.4) I–ColL
BOXD-T10: R= -(CH2)9CH3
a
Scheme 1. Synthesis of BOXD-Tn.
Scanning rate of 10 ꢁC/min.

S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
12431
Figure 3. DSC curves of (a) BOXD-T14, (b) BOXD-T10, (c) BOXD-T8, (d)
BOXD-T7, (e) BOXD-T6, and (f) BOXD-T5 on the subsequent heating run
(heating rate: 10 ꢁC/min), and (g) BOXD-T5 on the subsequent heating
run (heating rate: 2 ꢁC/min).
Figure 1. DSC curves of (a) BOXD-T14, (b) BOXD-T10, (c) BOXD-T8, (d)
BOXD-T7, (e) BOXD-T6, (f) BOXD-T5 on the first heating run, and (g)
BOXD-T5 measured after cooling from its isotropic state and holding at
room temperature for 48 h (heating rate: 10 ꢁC/min).
was not detected for 2 ꢁC/min due to the complete crystalli-
zation, thus only melting of the crystals was observed. The
heating curve of BOXD-T5 annealed at room temperature
for three days, is almost the same as its first heating curve
(Fig. 1g). Similar behavior was also observed in BOXD-
Tn (n¼6, 7, 8, 10), indicating their slow and kinetic-con-
trolled feature of crystallization.
slowly cooling from the isotropic liquid and the black areas
were homeotropic domains. The XRD pattern in this colum-
nar phase of BOXD-T5 (Fig. 5a) consisted of one strong
˚
˚
(100) (d¼21.4 A) peak, two weak (200) (d¼10.6 A) and
˚
(300) (d¼7.0 A) peaks in the small angle regions as well
˚
as a diffuse halo centered at 4.5 A, suggesting a lamellar
structure. Thus this phase was identified as ColL. Similar
mesophases were observed in other BOXD-Tn (n¼6, 7, 8,
10, 14) during cooling from their isotropic states. Upon
further cooling the ColL phase of BXOD-T5, a new phase
developed without obvious morphology changes. The
XRD pattern in this phase of BOXD-T5 consists of two
Figure 4a shows the optical textures of BOXD-T5 in its
mesophase on the cooling run (10 ꢁC/min). The focal-conic
texture typical of columnar phases (Col) was observed on
˚
˚
strong peaks at 22.4 A (200), 20.4 A (110) and five weak
˚
peaks at 11.0 A (400), 9.9 A (220), 6.6 A (330), 5.5 A
˚
(800), 4.9 A (440), which correspond to a rectangular
˚
˚
˚
columnar packing (Colr) (Fig. 5b). Similar sequence was ob-
served in BOXD-T6. The XRD results of BOXD-Tn (n¼5, 6,
7, 8, 10, 14) in their columnar phases are listed in Table 2.
On the subsequent heating of BOXD-T5, crystallization
process was observed under POM. Figure 4b showed the
pin-like textures, which developed from the pseudo focal-
conic textures at 60 ꢁC at a heating rate of 10 ꢁC/min. Fig-
ure 6c showed the morphology of BOXD-T5 at 60 ꢁC at
heating rate of 2 ꢁC/min, suggesting that the percentage of
crystallization was bigger at lower heating rate, which was
consistent with that of the DSC results. Crystallization of
BOXD-T5 during heating was also further confirmed by
XRD. The XRD pattern (Fig. 5c) for BOXD-T5 at 65 ꢁC
on subsequent heating (2 ꢁC/min) consisted of two strong
peaks in low-angle region and several weak peaks in both
low- and high-angle regions, indicating the formation of
a crystalline phase. Crystallization was observed for the
annealed BOXD-T5 at room temperature for more than
3 days under POM (Fig. 5d). Similar phenomena was also
observed in other BOXD-Tn (n¼6, 7, 8, 10).
Figure 2. DSC curves of (a) BOXD-T5, (b) BOXD-T6, (c) BOXD-T7, (d)
BOXD-T8, (e) BOXD-T10, and (f) BOXD-T14 on the cooling runs (cooling
rate: 10 ꢁC/min).

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S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
Figure 4. Optical textures observed for BOXD-T5 at (a) 40 ꢁC (ꢂ200) on the cooling run, (b) 60 ꢁC (ꢂ200) on the subsequent heating (10 ꢁC/min), (c) 60 ꢁC
(ꢂ200) on the subsequent heating (2 ꢁC/min), and (d) holding for 3 days at room temperature (ꢂ200).
On the cooling run (10 ꢁC/min), BOXD-T14 exhibited poly-
mesomorphic phase sequence (Fig. 2f). An exothermic peak
centered at 26.2 ꢁC (28.9 kJ/mol) was followed by two
exothermic peaks centered at 23.1 ꢁC (5.6 kJ/mol) and
17.3 ꢁC (15.2 kJ/mol), respectively. As the three exothermic
peaks are so close and partially overlapped, we have not got
Figure 5. X-ray diffraction patterns of BOXD-T5 (a) at 40 ꢁC and (b) at 20 ꢁC on the first cooling run (10 ꢁC/min), (c) at 60 ꢁC on subsequent heating run
(2 ꢁC/min), and (d) holding for more than 2 days at room temperature.

S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
Table 2. Powder WAXD results of BOXD-Tn in their mesophases
12433
˚
d, obsd (A)
˚
d, calcd (A)
˚
Lattice parameter (A)
Compound
BOXD-T5
Mesophase
hkl
Colr (20 ꢁC)
200
110
400
220
330
800
440
350
22.4
20.4
11.0
9.9
6.6
5.5
22.2
20.2
11.1
10.1
6.7
5.6
5.0
4.3
a¼44.4
b¼22.7
4.9
4.4
4.4 (halo)
21.4
10.6
4.4 (halo)
ColL (40 ꢁC)
Colr (5 ꢁC)
100
200
21.4
10.7
BXOD-T6
200
110
400
220
330
800
440
23.9
21.6
11.8
10.6
7.0
5.8
5.2
23.9
21.4
12.0
10.7
7.1
a¼47.8
b¼24.0
5.8
5.3
4.4 (halo)
22.5
11.1
7.4
4.4 (halo)
ColL (60 ꢁC)
ColL (35 ꢁC)
100
200
300
22.5
11.3
7.5
BOXD-T7
BOXD-T8
100
200
300
400
23.8
11.8
7.8
5.8
23.8
11.9
7.9
5.8
4.4 (halo)
ColL (35 ꢁC)
ColL (35 ꢁC)
100
200
400
24.3
12.2
6.1
4.4 (halo)
24.4
12.2
6.1
BOXD-T10
BOXD-T14
100
200
26.8
13.4
4.5 (halo)
26.8
13.4
ColL (35 ꢁC)
Colho (10 ꢁC)
100
200
30.4
15.0
4.5 (halo)
30.8
17.8
15.0
11.5
10.0
6.5
30.4
15.2
100
110
200
210
300
30.8
17.8
15.4
11.6
10.2
a¼35.6
001
4.2
4.4 (halo)
4.2
further experimental evidence to identify their structures. At
this stage, we named the two as ColI and ColII, respectively.
On further cooling, another stable high-ordered columnar
mesophase developed. Figure 6 shows the optical textures
of BOXD-T14 at 10 ꢁC. The XRD pattern of this columnar
phase of BOXD-T14 is shown in Figure 7b. In the low-angle
2.3. Optical properties
The UV–vis absorption and photoluminescence spectra for
BOXD-T4 in cyclohexane are presented in Figure 8. The
photophysical properties of BOXD-Tn in cyclohexane
(10ꢀ5 mol/L) are summarized in S-Table 1. The absorption
spectra of BOXD-Tn, in which an intense broad absorption
at 329 nm was observed, were similar in shape because of
their structural similarities. The PL spectra of BOXD-Tn
were recorded in cyclohexane at lexc.¼340 nm. All the com-
pounds exhibit strong fluorescence with two maxima at 378
and 395 nm. Fluorescence quantum yields were determined
relative to quinine sulfate in sulfuric acid aqueous solution
(FF¼0.546) and calculated according to literature.10 All
the compounds exhibited high quantum yield (FF>90%)
in cyclohexane (10ꢀ5 mol/L).
˚
region, a diffraction pattern of one strong peak at 30.8 A
˚
(100) and five weak peaks at 17.8 A (110), 15.0 A (200),
˚
˚
˚
11.5 A (210), 10.0 A (300) corresponded to a hexagonal
arrangement. In the high-angle region, a diffuse halo cen-
˚
tered at 4.4 A confirmed its LC nature, and a relatively
˚
strong peak at 4.2 A, which is assigned to (001) reflection,
indicated a certain degree of order along the columns.
Thus, it was identified as Colho phase, which was stable at
room temperature, and no crystallization was observed
even after more than three weeks.

12434
S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
Figure 8. UV–vis (B) and PL spectra (,) of BOXD-T4 in cyclohexane
(1ꢂ10ꢀ5 mol/L) at room temperature.
Figure 6. Optical textures observed for BOXD-T14 at (a) 10 ꢁC (ꢂ200) on
the cooling run.
In addition, all BOXD-Tn exhibited strong fluorescence in
bulk. Figure 9 shows the PL spectra of BOXD-Tn (n¼5, 6,
7, 8, 10, 14) in their mesophases (cooling rate 10 ꢁC/min)
at room temperature. The maximum emissions centered at
426 nm for BOXD-T5, 438 nm for BOXD-T6, 448 nm for
BOXD-T7, 433 nm for BOXD-T8, 434 nm for BOXD-
T10, and 426 nm for BOXD-T14.
Figure 9. Corrected PL spectra of BOXD-Tn (n¼5, 6, 7, 8, 10, 14) in their
mesophases (cooling rate 10 ꢁC/min) at room temperature. Spectra are
normalized to the same height at the maximum.
3. Conclusions
A new series of liquid-crystalline bi-1,3,4-oxadiazole deriv-
atives (2,20-bis(3,4,5-trialkoxyphenyl)-bi-1,3,4-oxadiazole,
BOXD-Tn, n¼3, 4, 5, 6, 7, 8, 10, 14) were designed and syn-
thesized. The columnar mesophases for BOXD-Tn (n¼5, 6,
7, 8, 10) were observed even at low temperature (ꢀ20 ꢁC)
during cooling. A room temperature Colho phase was
obtained for BOXD-T14. All the compounds have been
demonstrated to exhibit good fluorescence properties either
in cyclohexane solution or in bulk. Potential applications for
these compounds, such as optoelectronic applications, are of
interest and will be examined.
4. Experimental
4.1. Characterization
1H NMR spectra were recorded with a Bruker Avance
500 MHz or a Varian-300 EX spectrometer, using CDCl3
Figure 7. X-ray diffraction patterns of BOXD-T14 (a) at 65 ꢁC and (b) at
10 ꢁC on the first cooling run (10 ꢁC/min).

S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
12435
as solvent and tetramethylsilane (TMS) as an internal stan-
dard (d¼0.00 ppm). 13C NMR spectra were recorded with a
Varian-300 EX spectrometer, using CDCl3 as solvent and
CDCl3 as an internal standard (d¼77.00 ppm). Mass spectra
were obtained by MALDI-TOF mass spectrometry. FTIR
spectra were recorded with a Perkin–Elmer spectrometer
(Spectrum One B). The samples were pressed tablets
with KBr. Phase transitional properties were investigated
by differential scanning calorimeter (DSC, Mettler Star
DSC 821e). Optical textures were observed under polarized
optical microscope (POM, Leica DMLP) equipped with
a Leitz 350 heating stage. X-ray diffraction (XRD) was
carried out with a Bruker Avance D8 X-ray diffractometer.
14.06. FTIR: n¼3214, 3016, 2956, 2928, 2871, 2857,
1693, 1629, 1580, 1468, 1428, 1384, 1336, 1234 , 1212,
1114, 1004, 857, 750, 720 cmꢀ1. Anal. Calcd (%) for
C58H98N4O10: C, 68.88; H, 9.77; N, 5.54. Found: C, 69.16;
H, 10.05; N, 5.47.
4.1.6. Oxalyl acid N0,N0-di(3,4,5-trioctyloxybenzoyl)-
hydrazide. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): d¼10.35 (s, 2H), 9.15 (s, 2H), 7.04 (s, 4H), 4.00–
3.88 (m, 12H), 1.76–1.67 (m, 12H), 1.42–1.28 (m, 60H),
0.89 (t, 18H, J¼6.5Hz). FTIR: n¼3213, 2957, 2926, 2856,
1692, 1629, 1582, 1468, 1427, 1386, 1336, 1231, 1218,
1115, 1007, 957, 858, 782, 750, 722, 601 cmꢀ1. Anal. Calcd
(%) for C64H110 N4O10: C, 70.16; H, 10.12; N, 5.11. Found:
C, 70.35; H, 10.09; N, 4.85.
4.1.1. Oxalyl acid N0,N0-di(3,4,5-tripropyloxybenzoyl)-
hydrazide. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): d¼10.29 (s, 2H), 9.14 (s, 2H), 7.06 (s, 4H), 3.96 (s,
4H), 3.88 (s, 8H), 1.76 (s,12H), 1.03–1.00 (m, 18H).
FTIR: n¼3255, 3152, 3074, 2965, 2938, 2878, 1719, 1686,
1631, 1584, 1547, 1468, 1428, 1386, 1338, 1300, 1219,
1261, 1219, 1113, 1060, 1000, 960, 856, 837, 790, 751,
602 cmꢀ1. Anal. Calcd (%) for C34H50N4O10: C, 60.52; H,
7.47; N, 8.30. Found C, 60.59; H, 7.54; N, 8.31.
4.1.7. Oxalyl acid N0,N0-di(3,4,5-tridecyloxybenzoyl)-
hydrazide. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): d¼10.31 (s, 2H), 9.08 (s, 2H), 7.04 (s, 4H), 4.02–
3.91 (m, 12H), 1.77–1.68 (m, 12H), 1.43–1.26 (m, 84H),
0.86 (t, 18H, J¼6.6 Hz). FTIR: n¼3233, 3013, 2955, 2924,
2854, 1693, 1630, 1583, 1487, 1468, 1428, 1385, 1338,
1234, 1211, 1116, 1001, 987, 932, 857, 782, 751, 721,
601 cmꢀ1. Anal. Calcd (%) for C76H134 N4O10: C, 72.22;
H, 10.69; N, 4.43. Found: C, 72.23; H, 10.92; N, 4.50.
4.1.2. Oxalyl acid N0,N0-di(3,4,5-tributyloxybenzoyl)-
hydrazide. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): d¼10.29 (s, 2H), 9.14 (s, 2H), 7.06 (s, 4H), 3.96 (s,
4H), 3.88 (s, 8H), 1.76 (s, 12H), 1.03–1.00 (m, 18H).
FTIR: n¼3255, 3152, 3074, 2965, 2938, 2878, 1719, 1686,
1631, 1584, 1547, 1468, 1428, 1386, 1338, 1300, 1219,
1261, 1219, 1113, 1060, 1000, 960, 856, 837, 790, 751,
602 cmꢀ1. Anal. Calcd (%) for C40H62N4O10: C, 63.30; H,
8.23; N, 7.38. Found: C, 63.48; H, 8.24; N, 7.56.
4.1.8. 2,20-Bis(3,4,5-tripropyloxyphenyl)-bi-1,3,4-oxadi-
azole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
7.42 (s, 4H), 4.09–4.04 (m, 12H), 1.92–1.79 (m, 12H),
1.12–1.04 (m, 18H). FTIR: n¼2966, 2937, 2876, 1591,
1550, 1494, 1474, 1434, 1389, 1355, 1344, 1315, 1306,
1276, 1231, 1154, 1128, 1099, 1061, 1023, 997, 954, 934,
915, 877, 845, 831, 813, 766, 728, 671, 614, 594 cmꢀ1
.
Anal. Calcd for C34H46N4O8: C, 63.93; H, 7.26; N, 8.77.
Found: C, 63.71; H, 7.19; N, 8.71.
4.1.3. Oxalyl acid N0,N0-di(3,4,5-tripentyloxyphenyl)-
hydrazide. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): d¼10.61 (s, 2H), 9.61 (s, 2H), 7.07 (s, 4H), 3.93–
3.83 (m, 12H), 1.72–1.69 (m, 12H), 1.49–1.33 (m, 24H),
0.93–0.87 (m, 18H). FTIR: n¼3255, 3152, 3074, 2965,
2938, 2878, 1719, 1686, 1631, 1584, 1547, 1468, 1428,
1386, 1338, 1300, 1219, 1261, 1219, 1113, 1060, 1000,
960, 856, 837, 790, 751, 602 cmꢀ1. Anal. Calcd (%) for
C46H74N4O10: C, 65.53; H, 8.85; N, 6.65. Found: C, 65.48;
H, 8.75; N, 6.85.
4.1.9. 2,20-Bis(3,4,5-tributyloxyphenyl)-bi-1,3,4-oxadi-
azole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
7.41 (s, 4H), 4.12–4.06 (m, 12H), 1.90–1.74 (m, 12H),
1.57–1.50 (m, 12H), 1.03–0.96 (m, 18H). FTIR: n¼3435,
2956, 2933, 2872, 1593, 1545, 1492, 1465, 1437, 1382,
1349, 1306, 1272, 1238, 1133, 1116, 1066, 1025, 996,
955, 937, 887, 848, 837, 793, 728, 671, 598 cmꢀ1. Anal.
Calcd for C40H58 N4O8: C, 66.46; H, 8.09; N, 7.75. Found:
C, 66.58; H, 8.10; N, 7.96.
4.1.4. Oxalyl acid N0,N0-di(3,4,5-trihexyloxybenzoyl)-
hydrazide. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): d¼10.53 (s, 2H), 9.42 (s, 2H), 7.06 (s, 4H), 3.97–
3.84 (m, 12H), 1.71–1.66 (m, 12H), 1.45–1.28 (m, 36H),
0.91–0.85 (m, 18H). FTIR: n¼3338, 3211, 3013, 2957,
2932, 2872, 2860, 1719, 1695, 1624, 1582, 1467, 1427,
1386, 1337, 1234, 1216, 1001, 1043, 926, 859, 750, 777,
726 cmꢀ1. Anal. Calcd (%) for C52H86N4O10: C, 67.36; H,
9.35; N, 6.04. Found: C, 67.58; H, 9.45; N, 5.79.
4.1.10. 2,20-Bis(3,4,5-tripentyloxyphenyl)-bi-1,3,4-oxa-
diazole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
7.41 (s, 4H), 4.12–4.05 (m, 12H), 1.90–1.76 (m, 12H),
1.55–1.38 (m, 24H), 0.98–0.92 (m, 18H). FTIR: n¼2953,
2863, 1590, 1551, 1495, 1473, 1433, 1382, 1351, 1316,
1276, 1243, 1232, 1151, 1133, 1118, 1071, 1050, 1021,
991, 955, 929, 913, 893, 867, 841, 806, 779, 728, 671,
599 cmꢀ1. Anal. Calcd for C46H70 N4O8: C, 68.46; H,
8.74; N, 6.94. Found: C, 68.61; H, 8.83; N, 7.06. MALDI-
TOF MS: m/z: calcd for : 806.5, found: 806.2.
4.1.5. Oxalyl acid N0,N0-di(3,4,5-triheptyloxybenzoyl)-
hydrazide. 1H NMR: (500 MHz, CDCl3), (ppm, from
TMS): d¼10.15 (s, 2H), 8.90 (s, 2H), 7.03 (s, 4H), 4.03–
3.94 (m, 12H), 1.81–1.71 (m, 12H), 1.50–1.42 (m, 12H),
1.35–1.30 (m, 36H), 0.89 (t, 18H, J¼6.5 Hz). 13C NMR
(300 MHz, CDCl3): d¼165.08, 155.21, 153.18, 142.05,
125.31, 105.89, 73.44, 69.17, 31.90, 31.87, 31.81, 30.36,
29.37, 29.24, 29.12, 26.05, 26.01, 25.95, 22.65, 22.62,
4.1.11. 2,20-Bis(3,4,5-trihexyloxyphenyl)-bi-1,3,4-oxadi-
azole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
7.41 (s, 4H), 4.12–4.05 (m, 12H), 1.91–1.75 (m, 12H),
1.60–1.42 (m, 12H), 1.39–1.32 (m, 24H), 0.95–0.90 (m,
18H). FTIR: n¼2934.12, 2871, 1591, 1549, 1494, 1487,
1441, 1432, 1380, 1352, 1272, 1242, 1133, 1021, 980,

12436
S. Qu, M. Li / Tetrahedron 63 (2007) 12429–12436
840, 797, 727, 672, 601 cmꢀ1. Anal. Calcd for C52H82 N4O8:
C, 70.08; H, 9.27; N, 6.29. Found: C, 70.31; H, 9.39; N, 6.14.
Supplementary data
XRD patterns, DSC chart, and photophysical properties of
BOXD-Tn. Supplementary data associated with this article
can be found in the online version, at doi:10.1016/
j.tet.2007.09.028.
4.1.12. 2,20-Bis(3,4,5-triheptyloxyphenyl)-bi-1,3,4-oxa-
diazole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
7.41 (s, 4H), 4.11–4.05 (m, 12H), 1.91–1.75 (m, 12H),
1.54–1.49 (m, 12H), 1.40–1.32 (m, 36H), 0.92–0.88 (m,
18H). FTIR: n¼2953, 2923, 2870, 2852, 1589, 1549, 1493,
1466, 1430, 1389, 1351, 1305, 1276, 1240, 1193, 1148,
1131, 1117, 1070, 1024, 1006, 964, 954, 954, 936, 881,
842, 812, 773, 727, 672, 597 cmꢀ1. Anal. Calcd for
C58H94 N4O8: C, 71.42; H, 9.71; N, 5.74. Found: C, 71.18;
H, 9.91; N, 5.40.
References and notes
1. (a) Reviews Schultz, B.; Bruma, M.; Brehmer, L. Adv. Mater.
1997, 9, 601; (b) Thelakkat, M.; Schmidt, H.-W. Polym. Adv.
Technol. 1998, 9, 429.
2. Tokuhisa, H.; Era, M.; Tsutsui, T.; Saito, S. Appl. Phys. Lett.
1995, 66, 3433.
4.1.13. 2,20-Bis(3,4,5-trioctanoxyphenyl)-bi-1,3,4-oxadi-
azole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
3. (a) Zheng, Y.; Lin, J.; Liang, Y.; Lin, Q.; Yu, Y.; Meng, Q.;
Zhou, Y.; Wang, S.; Wang, H.; Zhang, H. J. Mater. Chem.
2001, 11, 2615; (b) Sano, T.; Nishio, Y.; Hamada, Y.;
Takahashi, H.; Usuki, T.; Shibata, K. J. Mater. Chem. 2000,
10, 157; (c) Noda, T.; Ogawa, H.; Noma, N.; Shirota, Y.
J. Mater. Chem. 1999, 9, 2177; (d) Jiang, X.; Liu, Y.; Tian,
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Sirigu, A.; Tuzi, A. J. Chem. Soc., Perkin Trans. 2 2002,
1791; (f) Wang, J.; Wang, R.; Yang, J.; Zheng, Z.; Carducci,
M. D.; Cayou, T. J. Am. Chem. Soc. 2001, 123, 6179.
4. (a) O’Neill, M.; Kelly, S. M. Adv. Mater. 2003, 15, 1135; (b)
van Breemen, A. J. J. M.; Herwig, P. T.; Chlon, C. H. T.;
Sweelssen, J.; Schoo, H. F. M.; Setayesh, S.; Hardeman,
W. M.; Martin, C. A.; de Leeuw, D. M.; Valeton, J. J. P.;
Bastiaansen, C. W. M.; Broer, D. J.; Popa-Merticaru, A. R.;
Meskers, S. C. J. J. Am. Chem. Soc. 2006, 128, 2336.
5. (a) Struijk, C. W.; Sieval, A. B.; Dakhorst, J. E. J.; Kimkes, P.;
Koehorst, R. B. M.; Donker, H.; Schaafsma, T. J.; Picken,
S. J.; van de Craats, A. M.; Warman, J. M.; Zuilhof, H.;
7.41 (s, 4H), 4.11–4.05 (m, 12H), 1.88–1.76 (m, 12H),
1.52–1.49 (m, 12H), 1.40–1.30 (m, 48H), 0.90–0.88 (m,
18H). FTIR: n¼2923, 2851, 1591, 1549, 1493, 1466, 1432,
1390, 1351, 1277, 1243, 1149, 1130, 1118, 1026, 954,
870, 842, 295, 727, 672, 598 cmꢀ1. Anal. Calcd for
C64H106 N4O8: C, 72.55; H, 10.08; N, 5.25. Found: C,
72.73; H,10.14; N, 4.92. MALDI-TOF MS: m/z: calcd for :
1058.8, found: 1058.6.
4.1.14. 2,20-Bis(3,4,5-tridecyloxyphenyl)-bi-1,3,4-oxadi-
azole. H NMR: (300 MHz, CDCl3), (ppm, from TMS):
1
7.41 (s, 4H), 4.11–4.05 (m, 12H), 1.89–1.76 (m, 12H),
1.52–1.49 (m, 12H), 1.40–1.28 (m, 72H), 0.91–0.86 (m,
18H). FTIR: n¼2952, 2849, 1589, 1550, 1494, 1468, 1442,
1430, 1387, 1352, 1308, 1276, 1242, 1149, 1131, 1121,
1067, 1047, 1022, 973, 954, 926, 880, 860, 843, 827, 795,
764, 764, 727, 672, 599 cmꢀ1. Anal. Calcd for C76H130
N4O8: C, 74.34; H, 10.67; N, 4.56. Found: C, 74.36; H,
10.57; N, 4.54.
€
Sudholter, E. J. R. J. Am. Chem. Soc. 2000, 122, 11057; (b)
4.1.15. 2,20-Bis(3,4,5-tritetradecyloxyphenyl)-bi-1,3,4-
oxadiazole. 1H NMR: (300 MHz, CDCl3), (ppm, from
TMS): 7.41 (s, 4H), 4.11–4.04 (m, 12H), 1.89–1.75 (m,
12H), 1.53–1.50 (m, 12H), 1.40–1.26 (m, 120H), 0.90–
0.86 (m, 18H). FTIR: n¼2920, 2850, 1590, 1547, 1490,
1469, 1434, 1386, 1356, 1315, 1274, 1237, 1147, 1124,
1027, 991, 968, 953, 873, 844, 780, 727, 721, 671,
599 cmꢀ1. Anal. Calcd for C100H178 N4O8: C, 76.77; H,
11.47; N, 3.58. Found: C, 77.13; H, 11.50; N, 3.46.
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Acknowledgements
The authors are grateful to the National Science Foundation
Committee of China (project no. 50373016), Program for
New Century Excellent Talents in Universities of China
Ministry of Education, Special Foundation for PhD Program
in Universities of China Ministry of Education (project no.
20050183057), and Project 985-Automotive Engineering
of Jilin University for their financial support of this work.
9. (a) Lai, C. K.; Ke, Y. C.; Su, J. C.; Lu, C. S.; Li, W. R. Liq.
Cryst. 2002, 29, 915; (b) Wen, C. R.; Wang, Y. J.; Wang,
H. C.; Sheu, H. S.; Lee, G. H.; Lai, C. K. Chem. Mater. 2005,
17, 1646.
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S. M.; Zhang, J. Y.; Zhang, H. X.; Wang, Y.; Che, C. M. J. Phys.
Chem. B 2005, 109, 8008.