Synthesis and properties of novel liquid crystalline materials with super high birefringence: styrene monomers bearing diacetylenes, naphthyl, and nitrogen-containing groups

Article abstract of DOI:10.1016/j.tet.2009.02.080

Three new liquid crystal asymmetrical styrene monomers bearing diacetylenes, naphthyl, and nitrogen-containing groups were successfully synthesized from 2-(bromoethynyl)-6-(hexyloxy)naphthalene, 4-(4-bromo-2-vinylphenyl)-2-methylbut-3-yn-2-ol, and derivat

Full text of DOI:10.1016/j.tet.2009.02.080

Tetrahedron 65 (2009) 3728–3732
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and properties of novel liquid crystalline materials
with super high birefringence: styrene monomers bearing diacetylenes,
naphthyl, and nitrogen-containing groups
*
Xiao-Lin Guan, Lan-Ying Zhang, Zhen-Lin Zhang, Zhihao Shen , Xiao-Fang Chen,
*
*
Xing-He Fan , Qi-Feng Zhou
Department of Polymer Science and Engineering and Key Laboratory of Polymer Chemistry and Physics of Ministry of Education, College of Chemistry
and Molecular Engineering, Peking University, Beijing 100871, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new liquid crystal asymmetrical styrene monomers bearing diacetylenes, naphthyl, and nitrogen-
containing groups were successfully synthesized from 2-(bromoethynyl)-6-(hexyloxy)naphthalene, 4-(4-
bromo-2-vinylphenyl)-2-methylbut-3-yn-2-ol, and derivatives of 4-ethynylaniline. The molecular
structures of these compounds were confirmed by FTIR, 1H NMR spectroscopy, elemental analysis, and
mass spectrometry. The liquid crystalline properties of monomers were characterized by differential
scanning calorimetry and polarized light microscopy. Results indicated that all the compounds exhibited
the nematic phase in liquid crystal state and super high optical birefringence of 0.5–0.8. The change of
terminal nitrogen-containing group affected the birefringence values in the order of –N(CH3)2<–NH2<–
NCS. Moreover, measurements using UV–vis and fluorescence spectroscopy showed their good photo-
luminescence properties and high quantum efficiency of 0.4–1.0.
Received 14 November 2008
Received in revised form 13 February 2009
Accepted 20 February 2009
Available online 6 March 2009
Keywords:
High birefringence
Liquid crystals
Styrene monomer
Photoluminescence
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
exhibit a larger optical anisotropy. So for, many high
Dn materials
have been obtained by increasing the molecular -electron con-
p
The design and synthesis of novel highly birefringent liquid
crystal (LC) material for use in optical devices are greatly desirable
in recent years with a rapid expansion of information technology
(IT). Nowadays liquid crystals which exhibit high values of
jugation length and introducing highly polarizable end groups,
such as difluoroisothiocyanate, benzene rings, and acetylene link-
ing groups, to give high dielectric anisotropy.4 Recently, an
increasing number of investigations and reports have showed that
naphthalene, diacetylene, and nitrogen-containing groups are
birefringence (
devices such as super twisted nematic (STN) and in high response
STN-LCDs with a narrow cell gap as n moderators, but also in
Dn) are employed not only in conventional display
superior polarizable parts to induce high
Dn in a liquid crystal
D
molecule.5 Therefore, it is reasonable that coupling of these types of
groups could lead to high optical and large dielectric anisotropies.
However, as we know, there has been no report on high
birefringence liquid crystal materials based entirely on the three
kinds of groups.
scattering-type PDLCDs as a reflective LCD, and in spatial light
modulators.1 And they are also widely used as compensation films
for improving the viewing angle, reflectors, and polarizers.2
Besides, more and more new applications of highly birefringent
liquid crystals are reported, for example, a new class of liquid
crystals with birefringence values greater than 0.5 in the visible
region has recently been developed to provide light emission for
organic light-emitting diodes (OLEDs).3
Polymer liquid crystals (PLCs) have attracted much attention
during the past decade due to their potential application as high
performance photoelectric materials due to their large optical
anisotropy and excellent stability.6 Reactive monomers can be
employed for the production of these polymer materials by ther-
mal polymerization or photopolymerization. As a result, the
design and synthesis of the relevant liquid crystal monomers with
polymerizable group as starting materials for the production of
anisotropic polymers are very important.7 In previous work, we
have synthesized two kinds of liquid crystalline monomers with
A large number of researches indicate that the
Dn of LCs is
mainly determined by -electron conjugation, molecular shape,
p
and order parameter. Thus, a more linearly conjugated LC would
* Corresponding authors.
E-mail addresses: zshen@pku.edu.cn (Z. Shen), fanxh@pku.edu.cn (X.-H. Fan),
qfzhou@pku.edu.cn (Q.-F. Zhou).
the
synthesize three new liquid crystal styrene monomers containing
D
n of 0.2–0.3 (Table 1).8 In the present work, we attempted to
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.02.080

X.-L. Guan et al. / Tetrahedron 65 (2009) 3728–3732
3729
Table 1
Phase transition temperatures (T/ꢀC), changes in enthalpies (
DH/kJ/mol in brackets)
Br
I
on the first heating and cooling runs, the thermal polymerization onset tempera-
tures and the thermal polymerization temperatures (T/ꢀC) of three styrene mono-
mers. Cr, crystalline phases; N, nematic
NBS,
AIBN,
CCl4
Reflux
50 h
a
heating scan
cooling scan
c
d
Compd
T0
Ts
PPh3,
O
Reflux
6 h
157:4ð45:8Þ
7
Cr
Cr
Cr
N
175
150
160
220
210
205
81:9ð16:9Þ
20 °C
24 h
40% HCHO,
5 M NaOH
128:4ð15:1Þ
8
Nb
N
—
R
Br
137:4ð45:9Þ
117:6ð15:0Þ
Br
I
9
HC C(CH3)2OH
CuI, PPh3,
80 ~ 85 °C
24 h
OHC
a
Pd(Ph3)2Cl2,
The transition peaks from the nematic phase to isotropic liquid were not ob-
served in DSC because three styrene monomers easily undergoes thermal poly-
merization during heating.
OH
HC C(CH3)2OH
CuI, PPh3,
Pd(Ph3)2Cl2,
Et3N
Et3N
80 ~ 85 °C
21 h
C6H13Br,
K2CO3,
Acetonitrile
90 °C
6 h
KOH,
Reflux
12 h
b
– indicates value not determined.
Thermal polymerization onset temperature.
Thermal polymerization temperature.
Toluene
c
d
R
Br
OH
OHC
OC6H13
CBr4 / PPh3,
2 (3)
1
naphthalene, diacetylene, and nitrogen-containing groups
(Scheme 1). Our aim is threefold: (i) to prove the molecular design
20 °C
CuI, PPh3, Et3N
Pd(PPh3)2Cl
65 ~ 70 °C
28 h
48 h Zn, CH2Cl2
based on the structure of large linear
logical and the synthetic route is viable; (ii) to realize the super
high n liquid crystal styrene monomers, which could be used for
the preparation of mesogen-jacketed liquid crystalline polymers
with high n; (iii) to learn the liquid crystalline behavior and
p-electron conjugation is
Br2
OC6H13
D
R
OH
Reflux
22 h
t-BuOK,
t-BuOH
KOH,
D
Reflux
8 h
Isopropanol
photophysical property of the newly formed compounds. The
polymerization of three monomers and the birefringence prop-
erties of the prepared polymers will be described in forthcoming
publications.
Br
R
OC6H13
4 (5)
6
CuI, PPh3, Et3N
Pd(PPh3)2Cl
70 °C
24 h
C6H13
O
R
R
OC6H13
Scheme 1. The molecular structures of styrene monomers: (1) R¼–N(CH3)2; (2)
R¼–NH2; (3) R¼–NCS.
7 (8)
2, 4, 7: R = -N(CH3)2
3, 5, 8: R = -NH2
2. Results and discussion
C6H13O
NH2
The synthesis of the asymmetrical monomers 7, 8, and 9 is
outlined in Scheme 2. These target compounds were mainly syn-
thesized through the coupling of intermediate molecules 1, 2 (or 3),
and 6, respectively. The experimental details are described below
using 9 as an example. At first, 4-bromo-1-iodo-2-vinylbenzene
was synthesized using the similar method previously reported by
us9 and a transparent, viscous liquid, which was very unstable, was
obtained through purification by chromatography. Introduction
of the protected triple-bonded chain was straightforward by
8
20 °C
N N
12 h
CS2, Toluene
S
C6H13O
.
N
N
HNHCSH
Reflux
3 h
BTC
a
coupling between the 4-bromo-1-iodo-2-vinylbenzene and
CHCl3
2-methylbut-3-yn-2-ol (the optimal molar ratio was 1:1.1) using
Sonogashira conditions to give the 4-bromo-1-(2-methylbut-3-yn-
2-ol)-2-vinylbenzene 1. Similarly, another intermediate molecule
4-ethynylaniline 2 was also synthesized through the introduction
of a protected triple-bonded chain and the removal of the pro-
tecting group from acetylenes using the same method as reported
earlier.10 The naphthyl-containing compound, 2-(bromoethynyl)-6-
(hexyloxy)naphthalene 6, was obtained from 6-hydroxy-2-naph-
thaldehyde. Introduction of alkyl chain was accomplished by
reacting with bromoalkane in the presence of potassium carbonate
(K2CO3) in acetonitrile and the yield was very high, compared with
the method used in the previous synthesis of monomers.11 A variety
of methods have been used to prepare the bromoacetylene com-
pound. Our approach converted the aldehyde to the dibromoolefin
which then dehydrobrominated to the bromoacetylene and the
C6H13
O
NCS
9
Scheme 2. Synthesis of styrene liquid crystalline monomers.
yellow solid product 6 was successfully obtained.12 It should be
noted that the acetylene intermediates in this work seemed to be
sensitive to light and heat and every effort need to be made to
protect these materials from light and heat. As shown in Scheme 2,
the coupling of styrene fragment 1 with the aniline fragment 2 was
carried out in the presence of copper acetate to afford the com-
pound 4 and the method was also used to prepare compound 8.13

3730
X.-L. Guan et al. / Tetrahedron 65 (2009) 3728–3732
However, under the same conditions, each fragment can also self-
couple to form the respective dimers. The low yields of 4, 5, 7, and 8
were attributed to these accompanying self-coupling reactions.
Then, the conversion from the amino-group to the isothiocyanic
ester was accomplished through two-step reactions using triethyl-
enediamine hexahydrate and carbon disulfide in toluene, and
bis(trichloromethyl)carbonate (BTC) in chloroform to give the
compound 9, respectively. The resulting crude product was purified
by recrystallization from acetone to obtain the target monomer 9.14
Compared with a step method of using poisonous thiophosgene to
synthesize the isothiocyanic ester in many papers, the two-step
method by use of BTC is safer and more environmentally friendly.
The liquid crystalline properties of these three target mono-
mers were investigated primarily by polarized light microscopy
(PLM) and differential scanning calorimetry (DSC). The phases
were identified through the comparison of the observed textures
with reference textures from PLM.15 Figure 1 shows PLM photo-
graphs of monomers 7, 8, and 9 observed in their LC phases in the
course of heating. It was obvious that all three compounds were
mesogenic compounds and exhibited a schlieren texture with
two brushes and four brushes in their LC phase, which is the
typical texture of the nematic liquid crystalline phase. Further-
more, we found that the three monomers all entered the liquid
crystal state at the first phase transition temperature at
(a)
6
4
2
0
-2
-4
-6
-8
-10
50
100
150
200
250
300
0
20
40
60
80 100 120 140 160
Temperature (°C)
(b)
5
4
3
2
60 80 100120140160180200220240
1
0
-1
-2
0
20
40
60
80
Temperature (°C)
100
120
(c)
5
0
-5
-10
-15
50
100
150
200
250
40
60
80
Temperature (°C)
100
120
140
160
Figure 2. DSC traces for monomers on second heating and subsequent cooling. (a)
Monomer 7: from ꢁ20 to 170 ꢀC (scan rate 10 ꢀC minꢁ1). Inset: DSC traces on third
heating from 50 to 300 ꢀC. (b) Monomer 8: from ꢁ20 to 138 ꢀC (scan rate 10 ꢀC minꢁ1).
Figure 1. Polarized light microscopy images of monomers. (a) Monomer 7: schlieren
texture of nematic phase at 165 ꢀC. (b) Monomer 8: schlieren texture of nematic phase
at 136 ꢀC. (c) Monomer 9: schlieren texture of nematic phase at 140 ꢀC.
Inset: DSC traces on ꢁth1ird heating from 50 to 250 ꢀC. (c) Monomer 9: from 20 to 165 ꢀ
C
(scan rate 10 ꢀC min ). Inset: DSC traces on third heating from 25 to 300 ꢀC.

X.-L. Guan et al. / Tetrahedron 65 (2009) 3728–3732
3731
approximately 150 ꢀC, when a bright, colorful birefringent texture
was observed. However, because of the ready thermal polymer-
ization of the monomers, the mesophase was not stable upon
further heating and the field of view turned black at 235, 190, and
228 ꢀC, respectively.
monomers 10 and 11 synthesized in our previous studies are
collected in Table 2. It is well known that high n value can be
D
achieved by increasing the molecular conjugation length. Mole-
cules that contain highly polarizable groups with high electron
density, such as acetylene linking groups, will therefore have large
optical anisotropies. Moreover, high birefringence materials can be
obtained by introducing high polar end groups.10 Firstly, the
presence of 1,3,4-oxadiazole and ester groups in molecular 10 and
11 destroyed the linear conjugation degree. Secondly, there were
The DSC curves of three compounds are shown in Figure 2
and the phase transitions are summarized in Table 1. Compound
7 exhibited a narrow endothermic peak centered at about 157 ꢀC
in the second heating run, corresponding to the transition from
the crystal phase (Cr) to the nematic liquid crystalline phase (N),
and a transition from the mesophase to the crystal phase at
about 82 ꢀC on cooling curve of the DSC, respectively. Further-
more, as shown in the inset of Figure 2a, a broad exothermic
process started at about 175 ꢀC and centered at 220 ꢀC indicated
that the monomer easily undergoes thermal polymerization once
it passed the transition from crystal to liquid crystalline phase.
The isotropization process was not observed since the tempera-
ture was kept low to avoid polymerization of the monomer
during the heating process. For compound 8, an endothermic
peak is at 128 ꢀC in DSC curves and a thermal polymerization
peak started at about 150 ꢀC and centered at 210 ꢀC could be
observed, similar to the result of compound 7. But, the DSC curve
did not display any transition in the cooling run probably due to
higher polymerization activity compared with the activities of
compounds 7 and 9. For compound 9, the transition from Cr to N
was at 137 ꢀC and the mesophase to the crystal phase was at
about 118 ꢀC while the thermal polymerization onset tempera-
ture was at 160 ꢀC.
no high polar end groups in molecular 10 and 11. So, the Dn values
of both 10 and 11 were lower than those of 7, 8, and 9. Otherwise,
symmetry lowering has also played an important role in increasing
the anisotropy of liquid crystals.17 Compared with 10, the sym-
metry of 11 was lower. Therefore, the
Dn value of 11 was higher
than that of 10. As expected, three monomers 7, 8, and 9 con-
taining high conjugation along the molecular long axis exhibited
high
D
n values of over 0.4. Moreover, the change of terminal ni-
n values in the order of
trogen-containing group affected the
D
–N(CH3)2<–NH2<–NCS, which was consistent with the order of
the electron-withdrawing strength. It was worth noting that
compound 9 had an extremely high
Dn value of 0.75, which was
much higher than most liquid crystal molecules reported before.
So, it is expected to be a good candidate for preparation of poly-
mers with high
Dn.
It is well known that molecules with large
p-electron conju-
gation length would possess better luminescence ability. So, we
also studied the fluorescence property of three monomers. The
maximum absorption wavelength in UV–vis spectrum, the maxi-
mum excitation and transmitting wavelength in CHCl3 in fluo-
rescence spectrum, and the fluorescence quantum yield in
solution are listed in Table 3. The results showed that all com-
pounds emitted blue light and their fluorescence quantum yields
Having demonstrated the liquid crystal properties of three
monomers, we focused our attention on their
Dn properties. Dn
was evaluated as extrapolated values from mixtures containing
10 wt % of each test compound in SLC069015 (supplied by Shi-
jiazhuang Yongsheng Huatsing Liquid Crystal Co. Ltd, China).16
Refractive indices data of compound 7, 8, 9, and some other
(F
) in solution were high. Noticeably, the
F of compound 7
(97.5%) was very high and was expected to be useful for
Table 2
no, ne, and Dn values of the synthesized styrene monomers
D
na
a
a
Compd
Molecular structure
no
ne
C6H13
O
7
1.54
1.59
1.57
1.51
2.01
2.20
2.32
1.71
0.47
0.61
0.75
0.20
N
8
C6H13
O
NH2
9
C6H13
O
NCS
10b
O
O
OC6H13
C6H13
O
N
N
N
N
O
O
O
O
11b
1.51
1.79
0.28
C6H13
O
OC6H13
a
no, ne, and
D
n values (at 25 ꢀC and
n)gþ(1ꢁx) ( n)h, where the subscripts g, h and gh denote guest, host, and guest–host cells, respectively; x is the concentration (in wt %) of the guest
l
¼589 nm) were extrapolated values from the mixture of the liquid crystal monomer (10 wt %) and SLC069015 (90 wt %)] from an
equation: (
D
n)gh¼x(
D
D
compound.
b
Two styrene monomers synthesized in our previous studies were reported in Ref. 8a and b.

3732
X.-L. Guan et al. / Tetrahedron 65 (2009) 3728–3732
7. (a) Broer, D. J.; Boven, J.; Mol, G. N. Makromol. Chem. 1989, 190, 2225; (b)
Table 3
Chain, S. H.; Hwai, L. C. J. Polym. Sci., Part A: Polym. Chem. 1999, 37, 3929; (c)
Cassano, R.; Dbrowski, R.; Dziaduszek, J. Tetrahedron Lett. 2007, 48, 1447; (d)
Raymond, J. T.; Kenichi, T.; Peter, T. J. Am. Chem. Soc. 2006, 128, 12084; (e)
Williams, B. S.; Leatherman, M. D.; Peter, S. W. J. Am. Chem. Soc. 2005, 127,
5132.
The UV–vis and fluorescence spectral data of three styrene monomers (wavelengths
in nm)
Monomers
labs (UV–vis) (nm)
lex (nm)
lem (nm)
Fluorescence quantum
yielda
F (%)
8. (a) Chen, S.; Gao, L. C.; Zhao, X. D.; Zhou, Q. F. Macromolecules 2007, 40, 5718;
(b) Chai, C. P.; Zhu, X. Q.; Zhou, Q. F. Macromolecules 2007, 40, 9361.
9. Zhang, D.; Liu, Y. X.; Zhou, Q. F. Macromolecules 1999, 32, 5183.
10. Catanescu, O.; Chien, L. C. Liq. Cryst. 2006, 33, 115.
11. Zhang, H.; Yu, Z.; Wan, X.; Zhou, Q.-F.; Woo, E.-M. Polymer 2002, 43, 2357.
12. Rajesh, A. S.; Marye, N.; David, G. A. Liq. Cryst. 2000, 27, 801.
7
8
9
381
360
338
387
363
359
471
445
410
97.5
51.2
38.9
a
Estimated by using quinine sulfate (dissolved in 0.05% H2SO4 with a concentra-
tion of 10ꢁ6 M, assuming FPL of 0.55ꢂ0.05) as a standard.
13. Synthesis of 7: Solution of compound 4 (2.4 g, 8.85 mmol) dissolved in dry
triethylamine (30 ml) was added dropwise to a suspension of compound 6
(2.44 g, 7.38 mmol), Pd(PPh3)2Cl2 (0.33 g, 0.47 mmol), triphenylphosphine
(0.24 g, 0.93 mmol), and copper(I) iodide (0.12 g, 0.69 mmol) in dry triethyl-
amine (180 ml) at room temperature under nitrogen. The mixture was stirred
at near 70 ꢀC for 24 h. After cooled to room temperature, the mixture was
filtered and filtrate concentrated in vacuo to remove triethylamine. The crude
product was dissolved in dichloromethane and extracted with aqueous am-
monium chloride solution. The organic phase was then washed with saturated
aqueous sodium chloride and dried over MgSO4. The crude product was iso-
lated by evaporating the solvent and purified by column chromatography
using dichloromethane/pet. ether 1:1 as eluant. Pure product as a light yellow
needle-like crystal was obtained after being recrystallized in acetone; yield: 1.
photoluminescence, electroluminescence, and organic light-emit-
ting diodes (OLEDs) applications.
3. Conclusion
In conclusion, we had designed and synthesized three new
styrene monomers with large
ing diacetylenes, naphthyl, and nitrogen-containing groups, which
were very important monomers for the preparation of high
polymers. PLM and DSC results indicated their nematic liquid
crystalline phases and the good polymerization ability. Measure-
p-electron conjugation length bear-
65 g (42%). 1H NMR (400 MHz, CDCl3)
d (ppm): 0.90–0.94 (m, 3H, –CH3), 3.01
D
n
(s, 6H, –N(CH3)2), 4.06–4.10 (m, 2H, Ar-OCH2–), 5.44 (d, 1H, J¼10.7 Hz, ]CH2),
5.89 (d, 1H, J¼17.5 Hz, ]CH2), 7.10–7.15 (m, 1H, ]CH–), 6.67 (d, 2H, J¼7.2 Hz,
Ar), 7.18–7.71 (11H, Ar), 8.00 (s, 1H, Ar). 13C NMR (CDCl3):
d 14.45, 23.02, 26.17,
29.55, 31.99, 40.59, 68.54, 74.01, 80.17, 84.46, 87.64, 93.81, 107.00, 112.20, 116.
71, 117.20, 119.83, 120.38, 125.50, 127.33, 127.87, 128.60, 129.41, 129.78, 130.49,
ments of
compounds were very high and compound 9 had an extremely high
n value, much higher than most of those reported before. More-
Dn showed that the extrapolated Dn values of these
133.27, 133.71, 134.54, 135.12, 140.87, 150.68, 158.74. IR (KBr)
n
¼3088, 3057,
2951, 2926, 2868, 2802, 2194, 1918, 1622, 1591, 1524, 1365, 1225, 1185, 1017,
916, 895, 818 cmꢁ1. Anal. Calcd: C, 87.49; H, 6.76; N, 2.68. Found: C, 87.09; H,
6.64; N, 2.75. MS m/z (Mþ): 521.
D
over, all the compounds exhibited blue fluorescence and better
fluorescence quantum yields, making them good candidates for
many luminescence applications.
Synthesis of 8: The synthesis method and purification was similar to that of 7,
and a light yellow needle-like crystal was obtained; yield: w35%. 1H NMR
(400 MHz, CDCl3)
d (ppm): 0.88–0.95 (m, 3H, –CH3), 3.90 (s, 2H, –NH2), 4.03–
4.09 (m, 2H, Ar-OCH2–), 5.44 (d, 1H, J¼11.6 Hz, ]CH2), 5.89 (d, 1H, J¼17.0
Hz, ]CH2), 7.09–7.15 (m, 1H, ]CH–), 6.64 (d, 2H, J¼8.4 Hz, Ar), 7.19–7.71
Acknowledgements
(11H, Ar), 7.99 (s, 1H, Ar). 13C NMR (CDCl3):
d 13.96, 22.52, 25.66, 29.04, 31.50,
68.08, 73.52, 79.62, 79.80, 84.10, 87.09, 92.76, 106.54, 112.08, 114.75, 116.24,
116.89, 119.67, 119.99, 124.83, 126.97, 127.57, 128.20, 129.02, 129.42, 130.18, 132.
The work described in this paper was supported by the National
Science Foundation of China (Grant Nos.: 20634010, 20574002,
20874002, and 50743042) and the Science Research Fund of the
Chinese Ministry of Education (No.: 20070420253).
90, 133.14, 133.36, 134.08, 134.75, 140.50, 147.01, 158.39. IR (KBr)
n
¼3383, 3081,
3035, 2949, 2924, 2871, 2859, 2199, 1917, 1617, 1592, 1517, 1390, 1296, 1224,
1181, 1026, 909, 889, 832 cmꢁ1. MS m/z (Mþ): 493.
14. Synthesis of 9: Carbon bisulfide (10.0 ml) was added dropwise to a suspension
of compound
8 (1.75 g, 3.69 mmol) and triethylenediamine hexahydrate
(2.45 g, 21.88 mmol) in toluene (50 ml) at room temperature. The mixture was
stirred at room temperature for 12 h and abundant precipitation was produced.
A yellow power (2.40 g) was obtained by filtration and drying under vacuum.
Then, solution of BTC (0.37 g, 1.26 mmol) dissolved in chloroform (5 ml) was
added dropwise to a suspension of the powder in chloroform (20 ml) at room
temperature. After stirred at room temperature for 4 h, the mixture was heated
under reflux with constant stirring for 2 h. After cooled to room temperature,
the mixture was filtered and filtrate concentrated in vacuo to remove chloro-
form. The crude product was isolated by evaporating the solvent and purified
by column chromatography using EtOAc/pet. ether 1:1 as eluant. Pure product
as a pale yellow needle-like crystal was obtained after being recrystallized in
References and notes
1. (a) Meng, H. H. B.; Dalton, L. R.; Wu, S. T. Mol. Cryst. Liq. Cryst. 1994, 259, 303; (b)
Hsu, C. S.; Tsay, K. T.; Chang, A. C.; Wang, S. R. Liq. Cryst. 1995, 19, 409; (c)
Khoshsima, H.; Ghanadzadeh, A.; Tajalli, H.; Dabrowski, R. J. Mol. Liq. 2006, 129,
169; (d) Yang, D. K.; Lu, Z. J.; Chien, L. C.; Doane, J. W. SID Tech. Dig. 2003, 34,
959; (e) Yang, D. K.; Doane, J. W. Appl. Phys. Lett. 1994, 64, 1905; (f) Fergason, J. L.
SID Tech. Dig. 1985, 16, 68; (g) Wu, S. T. Phys. Rev. A 1992, 30, 1270.
2. Markus, K. T.; Karen, H.; Kim, T. Thin Solid Films 2007, 516, 107; (b) Klasen, M.;
Bremer, M.; Tarumi, K. Jpn. J. Appl. Phys. 2000, 39, L1180.
3. (a) O’Neill, M.; Kelly, S. M. Adv. Mater. 2003, 15, 1135; (b) Kunihiko, O.; Atsushi,
S.; Tomiki, I. Adv. Mater. 2006, 18, 523.
acetone; yield: 1.30 g (67%). 1H NMR (400 MHz, CDCl3)
d (ppm): 0.90–0.94 (m,
3H, –CH3), 1.35–1.87 (8H, –CH2–), 4.06–4.10 (m, 2H, Ar-OCH2–), 5.47 (d, 1H,
J¼11.2 Hz, ]CH2), 5.90 (d, 1H, J¼17.3 Hz, ]CH2), 7.09–7.10 (m, 1H, ]CH–), 7.
4. (a) Takatsu, H.; Takeuchi, K.; Tanaka, Y.; Sasaki, M. Mol. Cryst. Liq. Cryst. 1986,
141, 279; (b) Wu, S. T.; Margerum, J. D.; Ho, M. S.; Hsu, C. S. Mol. Cryst. Liq. Cryst.
1995, 261, 79; (c) Wu, S. T.; Hsu, C. S.; Shyu, K. E. Appl. Phys. Lett. 1999, 74, 344;
(d) Wu, S. T.; Hsu, C. S.; Shyu, K. E. Appl. Phys. Lett. 2000, 77, 957; (e) Gauza, S.;
Wen, C. H.; Wu, S. T.; Hsu, C. S. Jpn. J. Appl. Phys., Part 1 2004, 43, 7634.
5. (a) Sekine, C.; Naoto, K. Liq. Cryst. 2001, 28, 1361; (b) Michael, H.; Toyne, K. J.;
Goodby, J. W. J. Mater. Chem. 2004, 14, 1731; (c) Gauza, S.; Li, J.; Wu, S. T. Liq.
Cryst. 2005, 32, 1077; (d) Seed, A. J. J. Mater. Chem. 2000, 10, 2069.
20–7.73 (12H, Ar), 8.00 (s, 1H, Ar). 13C NMR (CDCl3):
d 14.03, 22.59, 25.74, 29.12,
31.57, 68.11, 73.46, 79.28, 80.40, 84.47, 90.50, 90.90, 106.55, 116.09, 117.11, 119.97,
120.77, 121.89, 123.46, 125.80, 126.93, 127.89, 128.14, 128.92, 129.35, 130.32, 131.
20, 132.80, 132.89, 133.39, 133.87, 134.74, 136.81, 140.56, 158.36. IR (KBr)
n
¼3089, 3061, 2940, 2922, 2858, 2178, 2037, 1847, 1621, 1597, 1503, 1395, 1223,
1180, 1005, 933, 893, 831 cmꢁ1. Anal. Calcd: C, 82.96; H, 5.46; N, 2.61. Found: C,
82.87; H, 5.51; N, 2.69. MS m/z (Mþ): 535.
15. Hu, J. S.; Zhang, B. Y.; Jia, Y. G.; Chen, S. Macromolecules 2003, 36, 9060.
16. Sekine, C.; Iwakura, K.; Konya, N.; Minami, M.; Fujisawa, K. Liq. Cryst. 2001, 28,
1375.
6. (a) Menc, X.; Natansohn, A.; Rochon, P. J. Polym. Sci., Part B: Polym. Phys. 1996,
34, 1461; (b) Nobuhiro, K.; Tetsuro, K.; Tohei, Y. Adv. Mater. 2001, 13, 1337; (c)
Kunihiko, O.; Atsushi, S.; Osamu, T. J. Mater. Chem. 2005, 15, 3395; (d) Yan, X.;
Rafael, V.; Robert, H. G. J. Am. Chem. Soc. 2008, 130, 1735.
17. Hsu, H. F.; Lin, W. C.; Lai, Y. H.; Lin, A. Y. Liq. Cryst. 2003, 30, 939.