Microwave-assisted synthesis, structure, and tunable liquid-crystal properties of 2, 5-diaryl-1, 3, 4-thiadiazole derivatives through peripheral n-alkoxy chains

Article abstract of DOI:10.1002/asia.200800440

A series of substituted 2, 5-diaryl-1, 3, 4-thiadiazole derivatives are prepared by microwave-assisted synthesis in the absence of an organic solvent. All derivatives are well characterized by ¹H and ¹³C NMR, MS, and elemental analys

Full text of DOI:10.1002/asia.200800440

DOI: 10.1002/asia.200800440
Microwave-assisted Synthesis, Structure, and Tunable Liquid-Crystal
Properties of 2,5-Diaryl-1,3,4-Thiadiazole Derivatives through Peripheral
n-Alkoxy Chains
Jie Han,*[a] Xiao-Yong Chang,[a] Li-Rong Zhu,[a] Mei-Li Pang,[a] Ji-Ben Meng,[a]
Stephen Sin-Yin Chui,*[b] Siu-Wai Lai,[b] and V. A. L. Roy[c]
Abstract: A series of substituted 2,5-
diaryl-1,3,4-thiadiazole derivatives are
prepared by microwave-assisted syn-
thesis in the absence of an organic sol-
vent. All derivatives are well character-
by polarized-light optical microscopy
(POM), differential scanning calorime-
try (DSC), and in situ variable temper-
ature X-ray diffraction (VTXRD). By
variations in the peripheral n-alkoxy
chains, the calamitic mesogens exhibit
enantiotropic smectic (SmC and/or
SmA) mesophases with wide mesomor-
phic temperature ranges, whilst the
disc-like mesogens form hexagonal col-
umnar mesophase (Colh) at room tem-
perature. The bulk electrical conductiv-
ity values of the smectic mesophases of
1–3 are in the range of 10ꢀ3–10ꢀ4
Scmꢀ1, which are slightly higher than
that of their solid films. In contrast, the
solid film made from 2,5-di-(3,4,5-tri-
1
ized by H and 13C NMR, MS, and ele-
mental analyses. The X-ray crystal
structure of 2,5-di-(4-decyloxyphenyl)-
1,3,4-thiadiazole reveals the tilt lamel-
lar arrangement of rod-shaped mole-
cules, which are stabilized by a variety
of weak non-covalent interactions. The
liquid crystalline properties are studied
AHCTUNGTRENNUNG
Keywords: conducting materials
·
diarylthiadiazole · liquid crystals ·
mesophases · microwave chemistry
Introduction
molecular structures for application in electronic and opto-
AHCTUNGTRENNUNG
electronic devices, and liquid-crystal displays (LCD).[1] Ex-
Rational design and synthesis of new multi-functional meso-
genic materials derived from small molecules have attracted
considerable attention because of the self-assembly forma-
tion of a variety of highly anisotropic and ordered supra-
ploitation of new LC materials that exhibit mesophase(s) at
ambient temperature is one of the important challenges in
this field and will eventually impart practical advantages be-
cause such kind of mesogens readily generate robust meso-
phases that require minimal external energy input to drive
fabricated electronic devices such as light-emitting diodes,
field-effect transistors, photoconductors, and photovoltaic
cells.[2] Over the past decade, low molecular weight mole-
cules based on substituted 2,5-diaryl-1,3,4-oxadiazole deriva-
tives had been reported because of their good thermal/
chemical stability, high photoluminescence quantum yields,
and excellent electron-transporting properties.[3–6] Notably,
this diverse class of substituted 1,3,4-oxadiazole-containing
mesogens of different molecular geometry such as rod,[3]
banana,[4] disc,[5] and star,[6] had been extensively investigat-
ed and the heterocyclic moiety had also been utilized as a
functional side group in the preparation of electroactive
grafted homo- and co-polymers.[7] However, the thermotrop-
ic mesophases of these oxadiazole derivatives are generally
formed in narrow mesomorphic temperature ranges, which
inevitably limits the practical uses. Compared with the 1,3,4-
[a] Dr. J. Han, X.-Y. Chang, L.-R. Zhu, Dr. M.-L. Pang, Prof. J.-B. Meng
Department of Chemistry
Nankai University
94 Weijin Road, Tianjin, 300071 (P.R. China)
Fax : (+86)22-2350-8470)
E-mail: hanjie@nankai.edu.cn
[b] Dr. S. S.-Y. Chui, Dr. S.-W. Lai
Department of Chemistry
The University of Hong Kong
Pokfulam Road, Hong Kong (P.R. China)
E-mail: chuissy@hkucc.hku.hk
[c] Dr. V. A. L. Roy
Department of Physics and Materials Science
The City University of Hong Kong
Tat Chee Avenue, Kowloon, Hong Kong (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.200800440.
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FULL PAPERS
oxadiazole, the heterocyclic core that contains the sulfur
atom imparts unique physical and chemical properties, such
as higher melting and clearing points, higher viscosity, and
better packing efficiency with larger molecular dipole mo-
ments.[8] Up to now, a large number of studies have focused
on mesogenic materials based on thiazole,[9] 2,2’-bis-1,3,4-
thiadiazole,[10] and 1,3,4-thiadiazole derivatives,[11] in which
the latter class were related to the unsymmetric calamitic
mesogens with short amido, imino, azo, and vinylene/phenyl-
ene linkers. In contrast, only few studies have been carried
out on 1,3,4-thiadiazole-based disc-like mesogens, and the
effect of the number and position of the peripheral n-alkoxy
chains on the mesomorphic behavior of such compounds is
yet to be investigated. Herein, we describe a facile micro-
wave-assisted synthesis of a series of substituted 2,5-diaryl-
1,3,4-thiadiazole derivatives 1–11 (Scheme 1), in which a
Results and Discussion
Synthesis
The 1,3,4-thiadiazole derivatives were prepared by the ring-
closure reaction through sulfuration of 1,4-dicarbonyl pre-
cursors using Lawessonꢂs reagent[12a] and phosphorus(V)
pentasulfide (P2S5).[12b] The reactions were carried out in an-
hydrous conditions at elevated temperature. However, this
synthetic method suffered from certain drawbacks, such as
long reaction times and high cost. Recently, the use of mi-
crowave irradiation as a non-conventional energy source has
attracted considerable attention because of its operational
simplicity, high product yield, low cost, and short reaction
time.[13] Seed et al. have reported the microwave-assisted
synthesis of a class of 2-alkoxy-substituted thiophenes, 1,3-
thiazoles, and thiadiazoles.[14a] Thereafter, we[14b] and Lebrini
et al.[14c] focused on non-meso-
genic substituted 2,5-diaryl-
1,3,4-thiadiazoles using a simi-
lar approach. In this work, the
use of microwave irradiation is
crucial for the preparation of
the n-alkoxy-substituted 2,5-
diaryl-1,3,4-thiadiazole deriva-
tives. The key step for high
product yield was found to be
the irradiation time. The micro-
wave irradiation should be
stopped once the reaction mix-
ture turns into a liquid because
prolonged
leads to decomposition of the
reaction products after a few
irradiation
time
Scheme 1. Synthetic route of compounds 1–11.
seconds. The irradiation time
smectic or columnar mesophase could be readily obtained
by a proper choice of the peripheral n-alkoxy chain. By
changing the number, position, and the length of these n-
alkoxy chains, the ultimate liquid-crystal properties of this
class could be tuned. To the best of our knowledge, this
work represents a simple approach to switch the mesomor-
phic properties of a class of 1,3,4-thiadiazole mesogens be-
tween smectic and columnar behaviors. The room and high
temperature electrical conductivity of their as-cast solid
films made from some of the selected derivatives will be ex-
amined.
usually varied from 120 to 240 seconds and the product
yields were 50–65%. This method could be conveniently
carried out on a gram scale as long as the reactions were
carried out under solvent-free conditions. The work-up pro-
cess for the reaction was simple and clean.
X-ray Crystal Structure of 1
Single crystals of 1 suitable for X-ray diffraction determina-
tion were obtained by slow evaporation of its solution in
CH2Cl2 at room temperature. The crystallographic data are
summarized in the reference section.[15] Figure 1 depicts the
crystal structure of 1 and the packing of the molecules. It
¯
crystallized in the triclinic space group P-1 and there are
Abstract in Chinese:
two symmetry inequivalent molecules (labeled as A and B)
per asymmetric unit. Both molecules adopt a similar rod-
ꢀ ꢀ
shaped conformation with an average exocyclic angle C S
C of 1658, which leads to a roughly linear conformation. The
average molecular length is estimated as the head-to-tail dis-
tance of ca 40 ꢃ. There are weak p···p stacking (C5-
ꢀ
ꢀ
N
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
1100
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Microwave Synthesis and Properties of Thiadiazole Derivatives
shaped molecules are packed in
a lamellar arrangement with a
characteristic d-spacing value of
27.6 ꢃ. The average tilt angle f
of the molecules is found to be
approximately 41.18 with re-
spect to the lamellar normal, as
measured by the angle(s) be-
tween the mean plane(s) of the
molecules (A and B) and the
[001] Miller plane of the crystal
structure.
Liquid Crystal Properties
The liquid crystal properties of
1–11 were investigated by po-
larized-light optical microscopy
(POM), differential scanning
calorimetry (DSC), and in situ
Figure 1. Perspective diagram showing the tilt lamellar packing in 1. Note that two symmetry-inequivalent
molecules (A and B) are similarly packed with various types of non-covalent weak interactions in the crystal-
line solid.
the molecules can be alternatively viewed as a superposition
of two similar crystal lattices exclusively formed by the mol-
ecules A and B, in which the molecules of each type (A or
B) are aligned parallel to each other with extensive weak
variable temperature X-ray diffraction (VTXRD). The pho-
tomicrographs of the mesophases of 1–3 and 8–10 recorded
upon slow cooling of their isotropic liquids are shown in Fig-
ures 2 and 3, respectively. The transition temperatures and
enthalpy changes of 1–11 observed in the DSC study are
listed in Table 1. The nature of the mesophase of each com-
pound is identified according to the classification system de-
scribed by Kumar and Dierking.[16] As depicted in Fig-
ure 2a–b, both 1 and 2 displayed an enantiotropic smectic C
mesophase, as confirmed by the characteristic broken-fan
texture observed in the POM image. Whilst the compound 3
displayed enantiotropic smectic A and C mesophases, the
smectic A mesophase was assigned by the typical fan-
shaped texture upon cooling the isotropic liquid (Figure 2c);
further cooling of the birefringent liquid, the smectic A mes-
ophase gradually transformed to a smectic C mesophase, as
p···p stacking [C1
ACHTUNGTRENNUNG
G
ꢀ
weak
hydrogen
G
A
zole and phenylene moieties of the molecules, whereas the
ꢀ
molecules (type B) are packed together with weak C H···p
ꢀ
(C51 H51B
G
ꢀ
ꢀ
covalent C H···O weak hydrogen bonding (C41 H41-
(x,y,z)···O3(ꢀx,1ꢀy,1ꢀz) 2.612 ꢃ) interactions. It is notewor-
thy that the sulfur atoms of the molecules do not interact, as
evidenced by the long S···S contacts (>8.4 ꢃ). These rod-
Figure 2. Optical photomicrographs (magnification 200ꢀ) showing a) the
broken fan-shaped and Schlieren texture of the smectic C mesophase of
1 at 1758C on cooling; b) the broken fan-shaped texture of the smectic C
mesophase of 2 at 1608C on cooling; c) the fan-shaped texture of the
smectic A mesophase of 3 at 1548C on cooling, d) the Schlieren texture
of the smectic C mesophase of 3 at 1108C on cooling.
Figure 3. Optical photomicrographs showing the pseudo focal-conic tex-
ture with linear birefringent defects of the hexagonal columnar meso-
phases observed a) upon cooling the isotropic liquid of 8 at 248C (mag-
nification 200ꢀ); b) upon cooling the isotropic liquid of 9 at 30.58C
(magnification 200ꢀ); c) upon cooling the isotropic liquid of 10 at 178C
(magnification 500ꢀ).
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FULL PAPERS
Table 1. Phase transitions for compounds 1–11 derived from DSC meas-
urements.
Compound
Phase transitions T [8C] (DH [kJmolꢀ1])
1
Cr1 103.2 (51.0) SmC 191.4 (12.4) Iso
Iso 188.8 (ꢀ12.4) SmC 94.7 (ꢀ36.5) Cr2
Cr1 83.9 (38.3) SmC 190.9 (9.4) Iso
Iso 187.5 (ꢀ8.6) SmC 66.7 (ꢀ15.3) Cr2 42.9 (ꢀ15.4) Cr3
Cr 106.2 (39.0) SmC 154.6 (0.3) SmA 175.9 (0.6) Iso
Iso 175.0 (ꢀ1.4) SmA 149.8 (ꢀ0.9) SmC 83.2 (ꢀ36.5) Cr
Cr 44.5 (43.1) Iso
2
3
4
Iso 36.9 (ꢀ10.6) Cr
5
Cr 49.8 (60.3) Iso
Iso 37.0 (ꢀ51.8) Cr
6
Cr 45.0 (71.8) Iso
Iso ꢀ3.5 (ꢀ47.0) Cr
7
Cr1 ꢀ17.8 (ꢀ7.3) G 4.3 (ꢀ25.7) Cr2 43.4 (55.0) Iso
Iso ꢀ28.8 (ꢀ23.1) Cr3 ꢀ67.9 (ꢀ5.5) Cr4
Cr 33.4 (41.0) Colh 46.5 (3.9) Iso
Iso 40.4 (ꢀ4.7) Colh ꢀ0.8 (ꢀ8.9) Cr
Cr1 22.3 (ꢀ70.8) Cr2 41.4 (71.3) Colh 46.9 (6.3) Iso
Iso 42.7 (ꢀ5.0) Colh
8
9
10
11
Colh 21.3 (5.2) Iso
Iso 13.1 (ꢀ5.0) Colh
Cr1 9.5 (15.3) Cr2 66.9 (27.4) Iso
Iso 41.0 (ꢀ23.6) Cr2 4.7 (ꢀ15.6) Cr1
Key: Cr or Crn =crystal phase (nth); G=glassy state, SmC=smectic C;
SmA=smectic A; Colh =hexagonal columnar mesophase; Iso=isotropic
liquid.
evidenced by the appearance of Schlieren texture (Fig-
ure 2d). Unlike the cases in 1–3, the compounds 4–7 showed
no liquid-crystalline behavior, as confirmed by the POM ob-
servations and DSC data. Compounds 8–10 possess six pe-
ripheral n-alkoxy chains, which show different mesomorphic
behavior from that of 1–3. Based on the linear birefringent
defects[16b] as shown in Figure 3a–3c, the liquid-crystal be-
haviors of 8–10 might belong to the typical hexagonal col-
umnar mesophase. It is noteworthy that compound 10
formed a transparent viscous liquid at room temperature.
According to its POM image, it is indeed a room tempera-
ture liquid-crystal. Unlike 8–10, compound 11 was found to
be non-mesogenic because of the shorter n-butyloxy chains.
Figure 4. In situ X-ray diffractographs of 1 recorded upon heating the
solid sample from 308C to 1908C and cooling the isotropic liquid from
2008C to 308C.
Despite the short-range orders, similar tilt lamellar ar-
rangements of molecules in this mesophase likely exist with
a structural resemblance to that in the crystalline state.
Upon cooling the isotropic liquid to 1408C, the single peak
reappeared and its peak position remained almost un-
changed. At 908C, this smectic C mesophase co-existed with
a new crystal polymorph (Cr2), clearly shown by the new
peaks that appeared in the high-angle region (17–258 2q).
The VTXRD data of 2 and 3 are depicted in Figures S1 and
S2 of the Supporting Information. The results are consistent
with the DSC and POM study, and the observed single dif-
fraction peaks support the formation of smectic C meso-
phases with characteristic lamellar distances of 29 ꢃ and
26 ꢃ, respectively.
The in situ variable temperature X-ray diffractographs of
9 are shown in Figure 5. At around 438C in the heating
cycle, apart from its crystalline phase, a new diffraction peak
at 4.048 (2q) developed and the solid sample became a
cloudy liquid. Later, this peak became very intense and the
crystalline phase quickly vanished around 468C. This sharp
peak corresponds to a characteristic d-spacing value of
21.87 ꢃ of the columnar mesophase. Upon slow cooling of
its isotropic liquid from 508C to 308C, there was only a
Variable Temperature X-ray Diffraction (VTXRD)
The phase transitions of the selected compounds 1–3, 9, and
10 were investigated by in situ variable temperature X-ray
diffraction. Figure 4 depicts the X-ray diffractographs of 1
recorded upon heating the solid sample from 30–1908C and
cooling the isotropic liquid from 200–308C. At 1008C, a
Cr!SmC transition occurred, as revealed by the appear-
ance of a new diffraction peak with a 2q value of 2.898. As
the temperature increased, this new diffraction peak became
more intense when the temperature reached 1808C. This
single peak corresponds to a lamellar distance of 30.5 ꢃ of
the smectic C mesophase. According to the X-ray crystal
structure of 1, although this lamellar distance is larger than
the calculated d-spacing value of 27.6 ꢃ of the [001] Miller
plane of the X-ray crystal structure, it is still less than the
molecular length (40 ꢃ).
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Microwave Synthesis and Properties of Thiadiazole Derivatives
Electrical Conductivity Measurement
From the X-ray structure of 1, the tilt lamellar arrangement
of molecules prompts us to examine the bulk electrical con-
ductivity of the selected compounds 1–3 and 9, both in the
solid and liquid-crystalline phases. The current–voltage char-
acteristic curves of the solid films of 1–3 at 308C and 1308C
and the temperature dependence of the electrical conduc-
tance of the solid film of 9 are collectively shown in
Figure 6. At room temperature, the bulk conductivity values
Figure 6. Room and high temperature current–voltage characteristic
curves of the drop-cast solid film samples of 1–3 and 9 deposited on the
substrate with pre-patterned gold electrodes. Temperature dependence of
the bulk electrical conductivity value of 9 is shown in the bottom-right
corner.
Figure 5. In situ X-ray diffractographs of 9 recorded upon heating the
solid sample from 308C to 608C and cooling the isotropic liquid from
508C to 308C. Note that the X-ray diffractographs of the synthesized
solid sample and the annealed residue are very similar. X means an in-
strumental artifact from the tantalum sample holder.
(s) of the solid films of 1–3 were found to be 3.0ꢀ10ꢀ5, 1.8ꢀ
10ꢀ4, and 1.5ꢀ10ꢀ3 Scmꢀ1, respectively. All these room tem-
perature conductivity values were reproducible several
times and were comparable with that of some well-known
highly-conducting ionic liquids such as ethylmethylimidazo-
lium iodide (5.0ꢀ10ꢀ4 Scmꢀ1)[19a] and N-methyl-N-propylpyr-
rolidinium hydroxide (7.0ꢀ10ꢀ3 Scmꢀ1).[19b] However, the
solid film of 9 showed different electrical properties from
those of 1–3. At room temperature, the solid film of 9
showed a small value of 2.0ꢀ10ꢀ7 Scmꢀ1. The reason is un-
clear, but may be because of its non-lamellar or herring-
bone-like crystal packing, in which cofacial p···p stacking in-
teractions were prohibited as a result of steric hindrance
among the six n-octyloxy chains and thiadiazole cores. Inter-
estingly, when the solid films were heated to 1308C, the re-
spective smectic C mesophases of 1 and 2 showed different
extents of increase in their conductivity values (s=2.0ꢀ10ꢀ4
and 7.0ꢀ10ꢀ4 Scmꢀ1 in 1 and 2, respectively) whereas a
slight decrease in s (1.0ꢀ10ꢀ3 Scmꢀ1) was observed in the
case of 3. The increase in s could reasonably be attributed
to better charge conduction caused by the ordered align-
ments of molecules through p···p interactions. The shorter
n-butyloxy groups of 3 might give rise to a more efficient
sharp diffraction peak in the low-angle region of 3.88–3.908
(2q) and a diffuse halo, characteristic of the liquid-like order
between the n-octyloxy chains at 4.42 ꢃ. This type of dif-
fraction pattern corresponded to a lamellar phase (Coll) or a
hexagonal columnar phase (Colh).[17] In this work, the meso-
phase of 8–10 was characterized as Colh based on the tex-
tures observed through the polarized optical microscope. In
the literature, this has also been found in other structures
previously described as hexagonal columnar phase with sim-
ilar diffraction pattern.[18] Notably, the molecules in the solid
residue of 9 reversibly reverts to its original crystal packing
after two days, as revealed by the similar appearances of
their diffractographs. In the case of 10, the room tempera-
ture X-ray diffractograph displayed one peak at 4.568 (2q)
and a broad shoulder at around 20.358 (2q), which corre-
sponds to the long and short range orders of its columnar
mesophase (see Supporting Information, Figure S3).
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FULL PAPERS
packing of molecules in the crystalline solid, which leads to
higher conductivity among the three calamitic mesogens. On
the contrary, the bulk conductivity value of the solid film of
9 dramatically decreased from 10ꢀ7 to 10ꢀ14 Scmꢀ1 when
heated to 448C. The drop in s value is likely to be because
of the hexagonal columnar structure with insignificant p-
stacked interactions, which leads to poor charge conduction.
vealed that the long-range positional and orientational
orders were the least among the three mesogens as a result
of molecular non-symmetry. Apart from the symmetry
aspect, a change in the chain length of the n-alkoxy groups
monotonically alters the lamellar thickness of the smectic C
mesophase (d/ꢃ=30.5 in 1, 29.0 in 2, and 26.0 in 3). Howev-
er, such a change in chain length did not clearly correlate
with their mesomorphic temperature ranges.
Besides the rod-shaped mesogens, the effect of molecular
shape for this class was further examined and other arche-
types (Y-shaped (4), fork-like (5), branch-like, or polycate-
nar (6 and 7)) were prepared. All these non-mesogenic com-
pounds possess only mirror symmetry and an additional C2
axis exists in the molecule of 6. According to POM, DSC,
and VTXRD data, compounds 4–7 did not form any meso-
phases and therefore the packing of molecules at elevated
temperature was nevertheless
Discussion
The molecular peculiarity of mesogenic materials is the fun-
damental factor that affects the ultimate liquid-crystal prop-
erties. In this work, the effect of the number, position, and
chain length of the peripheral n-alkoxy chains on their mes-
omorphic properties have been demonstrated. Figure 7 out-
proven to be unstable. Interest-
ingly, on changing the positions
of the four n-decyloxy substitu-
ents as in the cases of 5 and 6,
the crystallization temperature
significantly decreased from
378C to ꢀ3.58C, which could
be explained by the effect of
molecular shape, as a conse-
quence of a large difference in
their dipole moments.[20] Addi-
tion of five n-decyloxy chains to
the two phenyl moieties of 7
generated a polycatenar mole-
cule and led to the occurrence
of a glass transition. This sug-
gests that the packing of mole-
cules might concurrently allow
a small proportion of short-
range orders to form a thermo-
dynamically feasible amorphous
phase. Remarkably, when six n-
alkoxy chains are simultaneous-
ly introduced on the two phenyl
Figure 7. A schematic diagram showing the switching of mesomorphic properties by varying the number, posi-
tion, and chain length of n-alkoxy chains of the 1,3,4-thiadiazole derivatives. The molecular lengths of 2 and 3
are estimated by their head-to-tail distances. The reported d-values (ꢃ) in 2, 3, and 10 were obtained by X-ray
diffraction data (See Supporting Information).
lines the switching of mesomorphic behaviors in between
smectic and columnar mesophases observed by changing the
peripheral chains of the 1,3,4-thiadiazole derivatives.
moieties of the compounds 8–11, the liquid-crystal proper-
ties significantly switched and led to the formation of hexag-
onal columnar mesophase for all these compounds (except
11). This observation suggests that the formation of the col-
umnar mesophase derived from the symmetric disc-shaped
molecules was driven by the peripheral n-alkoxy chains (n=
6–10). This finding is consistent with that observed for some
extended thiadiazole and oxadiazole derivatives with addi-
tional phenylene–vinylene spacers.[11f] The n-butyloxy chains
of 11 completely suppressed the formation of the respective
columnar mesophase. In the literature, extensive studies on
the effect of chain length of the n-alkoxy chains on other
discotic mesogens has been briefly discussed.[5b,c]
In our previous study, the 1,3,4-oxadiazole analogue of 1
was non-mesogenic, regardless of the symmetry of the mole-
cule,[3e] whilst the molecular symmetry of the calamitic
mesogens 1–3 changes as the two terminal n-alkoxy chains
are different. There are two-fold rotation and mirror sym-
metry elements present in 1, but only mirror symmetry
exists in the cases of 2 and 3. Thus, the symmetric mesogen
1 indeed has no energy preference among the head-to-head,
tail-to-tail, or head-to-tail configurations. Consequently, as
supported by X-ray diffraction data, this circumstance facili-
tates the formation of a more ordered smectic C mesophase.
On the contrary, the smallest enthalpy change for the
SmC!Iso or Iso!SmC transition(s) in the case of 3 re-
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Chem. Asian J. 2009, 4, 1099 – 1107

Microwave Synthesis and Properties of Thiadiazole Derivatives
mixture was stirred at room temperature for 2 h and then stirred at 708C
for a further 1 h. The reaction mixture was poured into distilled water
(100 mL) to precipitate the crude solid. The crude solid was washed with
distilled water and recrystallised from hot ethanol. Yield: 70–80%.
Conclusions
A series of calamitic and discotic mesogenic materials de-
rived from substituted 2,5-diaryl-1,3,4-thiadiazole derivatives
were prepared using a microwave-assisted solventless ap-
proach. Depending on the number, position, and the chain
length of the peripheral n-alkoxy groups of the molecules,
rich mesomorphic properties ranging from smectic to colum-
nar mesophases were observed. Variation in the chain
length of the six peripheral n-alkoxy chains may tune the
stability of the columnar mesophase that forms at around
room temperature. These mesogenic materials could be pre-
pared in good yields and they exhibited conducting proper-
ties. Therefore, these materials might be valuable for low
cost production of room temperature liquid crystals for ap-
plications in electronic and optoelectronic devices.
4-decyloxybenzoic acid N-4-(heptyloxy)benzoyl hydrazide ii: 1H NMR
(CDCl3): d=9.41 (s, 2H), 7.82 (d, J=7.2 Hz, 4H), 6.92 (d, J=9.0 Hz,
4H), 4.10–3.88 (m, 4H), 1.89–1.71 (m, 4H), 1.55–1.11 (m, 22H), 0.94–
0.84 ppm (m, 6H); ESI-MSACHTNUTGRNEUNG
(-ve): m/z (I%): 509.44 (100) [M]ꢀ.
4-decyloxybenzoic acid N-4-(butyloxy)benzoyl hydrazide iii: 1H NMR
(CDCl3): d=9.44 (s, 2H), 7.82 (d, J=8.7 Hz, 4H), 6.90 (d, J=8.4 Hz,
4H), 4.02–3.97 (m, 4H), 1.83–1.74 (m, 4H), 1.59–1.11 (m, 16H), 0.99 (t,
J=7.2 Hz, 3H), 0.88 ppm (t, J=6.6 Hz, 3H); ESI-MS
ACHTUNGTREN(NGNU -ve): m/z (I%):
467.43 (100) [M]ꢀ.
4-decyloxybenzoic acid N-3,5-di-(decyloxy)benzoyl hydrazide iv:
1H NMR (CDCl3): d=9.79 (s, 2H), 7.83 (d, J=8.4 Hz, 2H), 6.98 (s, 2H),
6.85 (d, J=8.4 Hz, 2H), 6.56 (s, 1H), 4.15–3.83 (m, 6H), 1.93–1.64 (m,
6H), 1.62–1.12 (m, 42H), 0.88 ppm (t, J=6.6 Hz, 9H); ESI-MS (-ve): m/z
(I%): 743.35 (100) [M+Cl]ꢀ.
4-decyloxybenzoic acid N-3,4,5-tri-(decyloxy)benzoyl hydrazide v:
1H NMR (CDCl3): d=9.78 (s, 1H), 9.49 (s, 1H), 7.84 (d, J=7.5 Hz, 2H),
7.07 (s, 2H), 6.90 (d, J=7.5 Hz, 2H), 4.01–3.95 (m, 8H), 1.89–1.65 (m,
8H), 1.54–1.14 (m, 56H), 0.88 ppm (t, J=6.6 Hz, 12H); ESI-MS (+ve):
m/z (I%): 865.80 (100) [M]+.
Experimental Section
General
3,5-di-(decyloxy)benzoic acid N-3,5-di-(decyloxy)benzoyl hydrazide vi:
1H NMR (CDCl3): d=9.36 (s, 2H), 6.96 (s, 4H), 6.61 (s, 2H), 4.06–3.87
(m, 8H), 1.87–1.70 (m, 8H), 1.49–1.18 (m, 56H), 0.88 ppm (t, J=6.6 Hz,
12H); ESI-MS (-ve): m/z (I%): 899.53 (100) [M+Cl]ꢀ.
1H NMR spectra were recorded on a Bruker AVANCE 300 (300 MHz)
or a Varian Mercury Plus 400 (400 MHz) spectrometer. The chemical
shifts (in ppm) are relative to the protons of tetramethylsilane (d=
0 ppm). Proton decoupled 13C NMR spectra were recorded at 101 MHz
on the same spectrometer. Elemental analyses were performed on a
YANACO CHN CORDER MT-3 apparatus. Electrospray-ionisation
(ESI) mass spectra were recorded on a Finnigan LCQ Advantage spec-
trometer and high-resolution mass spectra (HRMS) were obtained with a
Finnigan MAT 95 mass spectrometer.
3,5-di-(decyloxy)benzoic acid N-3,4,5-tri-(decyloxy)benzoyl hydrazide vii:
1H NMR (CDCl3): d=9.67 (s, 1H), 9.45 (s, 1H), 7.07 (s, 2H), 6.96 (s,
2H), 6.60 (s, 1H), 4.01–3.79 (m, 10H), 1.87–1.55 (m, 10H), 1.54–1.09 (m,
70H), 0.88 ppm (t, J=6.6 Hz, 15H); ESI-MS (-ve): m/z (I%): 1055.75
(100) [M+Cl]ꢀ.
General synthetic procedure for 1–11. Lawessonꢂs reagent [2,4-di-(4-me-
thoxyphenyl)-3-dithia-2,4-diphosphetane 2,4-disulfide] (1.1 mmol) and
the corresponding intermediate compound (i–xi, 1 mmol) were mixed
thoroughly in a test tube (10 mL). The test tube was irradiated by micro-
Single-crystal X-ray diffraction data of 1 was collected on a Bruker
SMART 1000 diffractometer using MoKa X-ray radiation (l=0.71073 ꢃ)
at 298 K. Structure solution and refinement were carried out by SHELX-
97 suite program.[21] The in situ variable temperature diffractographs
were recorded on a Bruker D8 ADVANCE diffractometer with CuKa X-
ray radiation (l=1.54146 ꢃ, rated at 1.6 kW) equipped with a modular
temperature chamber attachment (Material Research Instruments) oper-
ated at 30–2008C. Scan range=1.5–308 (2q), step size=0.048, scan
speed=1 s per step were used. The temperature and enthalpy changes of
phase transitions were determined by a NETZSCH DSC 204 differential
scanning calorimeter at the heating rate of 58Cminꢀ1 and pre-calibrated
with a pure indium sample. The optical textures of mesophases were ob-
wave for
2 to 4 min in a household microwave oven (Glanz
WP800L23K1) that operates 800 W. When the reaction mixture turned
into a liquid, the reaction was completed and the microwave irradiation
was stopped immediately. The test tube was removed from the oven after
the reaction mixture had cooled down for several minutes. The crude
product was dissolved in chloroform and purified by silica-gel column
chromatography using ethyl acetate/dichloromethane (v/v=1:15) as an
eluent. Evaporation of the solvent to dryness afforded off-white or pale
yellow solid samples of 1–11.
2,5-di-(4-decyloxyphenyl)-1,3,4-thiadiazole 1: Yield: 65%; 1H NMR
(CDCl3): d=7.93 (d, J=9.0 Hz, 4H), 6.98 (d, J=9.0 Hz, 4H), 4.02 (d, J=
6.6 Hz, 4H), 1.86–1.77 (m, 4H), 1.53–1.21 (m, 28H), 0.89 ppm (t, J=
6.6 Hz, 6H); 13C-{1H}-NMR (CDCl3): d=167.28, 161.55, 129.49, 122.97,
115.15, 68.43, 32.06, 29.71, 29.54, 29.48, 29.32, 26.16, 22.84, 14.27 ppm;
MS (20 eV EI): m/z (I%): 451 (30.71) [M]+; HRMS: calcd for
C34H50N2O2S: 550.3593; found: 550.3593; elemental analysis: calcd (%)
for C34H50N2O2S: C 74.14, H 9.15, N 5.09; found: C 74.05, H 9.23, N 5.09.
served on
a polarized-light optical microscope (OLYMPUS BX51)
equipped with a temperature-controlled hot stage.
For conductivity measurement, the solid samples of 1–3 and 9 were first
ultrasonicated in CH3CN for more than two hours, and then the suspen-
sion solution was drop-casted on the substrate with gold electrodes that
had been photo-lithographically pre-patterned to give the solid film
sample. The current–voltage characteristics were measured with a four-
probe station using a Keithley K4200 semiconductor parameter analyzer.
The set-up was kept inside the MBraun nitrogen glove box where oxygen
and moisture level were kept below 0.1 ppm.
2-(4-heptyloxyphenyl)-5-(4-decyloxyphenyl)-1,3,4-thiadiazole 2: Yield:
63%; 1H NMR (CDCl3): d=7.92 (d, J=8.7 Hz, 4H), 6.98 (d, J=8.7 Hz,
4H), 4.02 (t, J=6.6 Hz, 4H), 1.92–1.74 (m, 4H), 1.53–1.19 (m, 22H),
0.89 ppm (t, J=6.6 Hz, 6H); 13C-{1H}-NMR (CDCl3): d=167.23, 161.52,
129.46, 122.94, 115.11, 68.39, 32.07, 31.94, 29.74, 29.56, 29.49, 29.33, 29.22,
26.17, 26.13, 22.85, 22.78, 14.28, 14.25 ppm. MS (+cESI): 509.69 (M+,
100); elemental analysis: calcd (%) for C31H44N2O2S: C 73.18, H 8.72,
N 5.51; found: C 73.30, H 8.77, N 5.73.
Synthesis and Characterization
All chemicals were commercially available and used as received. The in-
termediate hydrazide i, and viii–xi were prepared by published meth-
ACHTUNGTRENNUNG
ods.[3e,5a]
General synthetic procedure for intermediates ii–vii. Substituted benzoic
acid (10 mmol) was added to thionyl chloride SOCl2 (10 mL) and re-
fluxed for 5 h to give the corresponding substituted benzoyl chloride. Ex-
cessive SOCl2 was removed by vacuum distillation and the reaction mix-
ture was cooled to room temperature. The corresponding substituted n-
decyloxybenzoic acid hydrazide (10 mmol) dissolved in pyridine (50 mL)
was added dropwise to the substituted benzoyl chloride. The reaction
2-(4-butyloxyphenyl)-5-(4-decyloxyphenyl)-1,3,4-thiadiazole 3: Yield:
57%; 1H NMR (CDCl3): d=7.92 (d, J=8.7 Hz, 4H), 6.98 (d, J=8.7 Hz,
4H), 4.03 (t, J=6.6 Hz, 4H), 1.89 1.75 (m, 4H), 1.51–1.19 (m, 16H), 1.01
(t, J=6.6 Hz, 3H), 0.89 ppm (t, J=6.6 Hz, 3H); 13C-{1H}-NMR (CDCl3):
d=167.29, 161.55, 129.493, 122.97, 115.15, 68.43, 68.10, 32.04, 31.35,
29.70, 29.52, 29.46, 29.30, 26.15, 22.82, 19.36, 14.25, 13.97 ppm; MS-
Chem. Asian J. 2009, 4, 1099 – 1107
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1105

J. Han, S. S.-Y. Chui et al.
FULL PAPERS
A
(100) [M]+; elemental analysis: calcd (%) for C38H58N2O6S: C 68.02,
C28H38N2O2S: C 72.06, H 8.21, N 6.00; found: C 72.19, H 8.35, N 5.86.
H 8.71, N 4.18; found: C 67.96, H 8.58, N 4.41.
2-(4-decyloxyphenyl)-5-(3,5-didecyloxyphenyl)-1,3,4-thiadiazole 4: Yield:
50%; 1H NMR (CDCl3): d=7.86 (d, J=8.4 Hz, 2H), 7.09 (s, 2H), 6.91
(d, J=8.4 Hz, 2H), 6.52 (s, 1H), 4.05–3.85 (m, 6H), 1.89–1.65 (m, 6H),
1.55–1.14 (m, 42H), 0.88 (t, J=6.6 Hz, 9H); 13C-{1H}-NMR (CDCl3):
168.15, 167.56, 161.78, 160.86, 140.82, 131.92, 131.09, 129.64, 129.04,
122.77, 115.22, 106.38, 104.31, 71.98, 68.58, 68.48, 32.13, 29.80, 29.61,
29.55, 29.43, 29.37, 26.25, 22.91, 19.37, 14.33; ESI-MS (+ve): m/z (I%):
707.61 (100) [M+]; elemental analysis: calcd (%) for C44H70N2O3S:
C 74.74, H 9.98, N 3.96; found: C 74.79, H 9.84, N 4.02.
Acknowledgements
This work was supported by a grant from the National Natural Science
Foundation of China (No. 20772064).
[1] a) P. J. Collings, M. Hird, Introduction to Liquid Crystals: Chemistry
2-(4-decyloxyphenyl)-5-(3,4,5-tri-decyloxyphenyl)-1,3,4-thiadiazole
5:
Yield: 53%; 1H NMR (CDCl3): d=7.93 (d, J=8.7 Hz, 2H), 7.12 (s, 2H),
6.99 (d, J=9.0 Hz, 2H), 4.08–4.00 (m, 8H), 1.88–1.72 (m, 8H), 1.57–1.13
(m, 56H), 0.88 (t, J=6.6 Hz, 12H); 13C-{1H}-NMR (CDCl3): 167.76,
167.57, 161.70, 153.71, 140.97, 140.83, 129.55, 125.32, 122.86, 115.20,
106.60, 73.81, 69.57, 68.47, 32.15, 30.58, 29.97, 29.88, 29.82, 29.64, 29.58,
29.37, 26.32, 26.23, 22.91, 14.33; ESI-MS (+ve): m/z (I%): 863.94 (100)
[M+]; elemental analysis: calcd (%) for C54H90N2O4S: C 75.12, H 10.51,
N 3.24; found: C 74.91, H 10.49, N 3.29.
and Physics, Taylor
& Francis, London, 1997; b) Handbook of
Liquid Crystals (Eds.: D. Demus, J. W. Goodby, G. W. Gray, H. W.
Spiess, V. Vill), Wiley-VCH, Weinheim, 1998; c) S. Laschat, A.
Baro, N. Steinke, F. Giesselmann, C. Hꢄgele, G. Scalia, R. Judele, E.
Kapatsina, S. Sauer, A. Schreivogel, M. Tosoni, Angew. Chem. 2007,
119, 4916–4973; Angew. Chem. Int. Ed. 2007, 46, 4832–4887.
[2] a) Z. S. An, J. S. Yu, S. C. Jones, S. Barlow, S. Yoo, B. Domercq, P.
Prins, L. D. A. Siebbeles, B. Kippelen, S. R. Marder, Adv. Mater.
2005, 17, 2580–2583; b) C. V. Yelamaggad, A. S. Achalkumar, Tetra-
hedron Lett. 2006, 47, 7071–7075; c) S. Kohmoto, E. Mori, K. Kishi-
kawa, J. Am. Chem. Soc. 2007, 129, 13364–13365.
[3] a) D. Acierno, S. Concilio, A. Diodati, P. Iannelli, S. P. Piotto, P.
Scarfato, Liq. Cryst. 2002, 29, 1383–1392; b) H. H. Sung, H. C. Lin,
Liq. Cryst. 2004, 31, 831–841; c) R. Cristiano, F. Ely, H. Gallardo,
Liq. Cryst. 2005, 32, 15–25; d) R. Cristiano, D. M. P. de O. Santos,
H. Gallardo, Liq. Cryst. 2005, 32, 7–14; e) J. Han, S. S. Y. Chui,
C. M. Che, Chem. Asian J. 2006, 1, 814–825.
[4] a) S. Kang, Y. Saito, N. Watanabe, M. Tokita, Y. Takanishi, H. Take-
zoe, J. Watanabe, J. Phys. Chem. B 2006, 110, 5205–5214; b) S. W.
Choi, S. M. Kang, Y. Takanishi, K. Ishikawa, J. Watanabe, H. Take-
zoe, Angew. Chem. 2006, 118, 6653–6656; Angew. Chem. Int. Ed.
2006, 45, 6503–6506; c) S. W. Choi, S. M. Kang, Y. Takanishi, K. Ish-
ikawa, J. Watanabe, H. Takezoe, Chirality 2007, 19, 250–254.
[5] a) C. K. Lai, Y.-C. Ke, J.-C. Su, C.-S. Lu, W.-R. Li, Liq. Cryst. 2002,
29, 915–920; b) C. R. Wen, Y. J. Wang, H. C. Wang, H. S. Sheu,
G. H. Lee, C. K. Lai, Chem. Mater. 2005, 17, 1646–1654; c) S. N. Qu,
M. Li, Tetrahedron 2007, 63, 12429–12436.
[6] a) J. Bettenhausen, P. Strohriegl, Macromol. Rapid Commun. 1996,
17, 623–631; b) J. Bettenhausen, M. Greczmiel, M. Jandke, P. Stroh-
riegl, Synth. Met. 1997, 91, 223–228; c) B. G. Kim, S. Kim, S. Y.
Park, Tetrahedron Lett. 2001, 42, 2697–2699.
[7] a) P. E. Cassidy, N. C. Fawcett, J. Macromol. Sci. Rev. Macromol.
Chem. Phys. 1979, C17, 209–266; b) X. C. Li, A. Kraft, R. Cervini,
G. C. W. Spencer, F. Cacialli, R. H. Friend, J. Gruener, A. B.
Holmes, J. C. DeMello, S. C. Moratti, Mater. Res. Soc. Symp. Proc.
1996, 413, 13–22; c) H. H. Sung, H. C. Lin, Macromolecules 2004,
37, 7945–7954; d) M. Sato, Y. Tada, S. Nakashima, K. I. Ishikura, M.
Handa, K. Kasuga, J. Polym. Sci. Part A Polym. Chem. 2005, 43,
1511–1525; e) M. Sato, Y. Matsuoka, I. Yamaguchi, J. Polym. Sci.
Part A Polym. Chem. 2007, 45, 2998–3008.
2,5-di-(3,5-didecyloxyphenyl)-1,3,4-thiadiazole 6: Yield: 53%; 1H NMR
(CDCl3): d=7.25 (s, 4H), 6.62 (s, 2H), 4.08–3.96 (m, 8H), 1.92–1.69 (m,
8H), 1.57–1.13 (m, 56H), 0.88 ppm (t, J=6.6 Hz, 12H); 13C-{1H}-NMR
(CDCl3): d=168.46, 160.89, 131.76, 106.47, 105.44, 104.48, 68.60, 32.13,
29.80, 29.61, 29.56, 29.43, 29.22, 26.26, 22.91, 14.34 ppm; ESI-MS (+ve):
m/z (I%): 885.34 (100) [M+Na]+; elemental analysis: calcd (%) for
C54H90N2O4S: C 75.12, H 10.51, N 3.24; found: C 75.09, H 10.43, N 3.26.
2-(3,5-di-decyloxyphenyl)-5-(3,4,5-tridecyloxyphenyl)-1,3,4-thiadiazole 7:
Yield: 58%; 1H NMR (CDCl3): d=7.02 (s, 2H), 7.13 (s, 2H), 6.57 (s,
1H), 4.16–3.99 (m, 10H), 1.91–1.70 (m, 10H), 1.57–1.16 (m, 70H),
0.88 ppm (t, J=6.6 Hz, 15H); 13C-{1H}-NMR (CDCl3): d=168.42, 168.05,
160.89, 153.74, 141.14, 131.79, 125.11, 106.62, 106.39, 104.37, 73.81, 69.56,
68.55, 32.14, 30.58, 29.97, 29.88, 29.82, 29.63, 29.58, 29.43, 26.33, 22.91,
14.32 ppm; ESI-MS (+ve): m/z (I%): 1020.07 (100) [M+]; elemental
analysis: calcd (%) for C64H110N2O5S·H2O: C 74.08, H 10.88, N 2.70;
found: C 74.31, H 11.28, N 2.87.
2,5-di-(3,4,5-tridecyloxyphenyl)-1,3,4-thiadiazole 8: Yield: 60%; 1H NMR
(CDCl3, 300MHz): d=7.20 (s, 4H), 4.10–4.01 (m, 12H), 1.91–1.70 (m,
12H), 1.56–1.22ACHTUNGTRENNUNG
(m, 84H), 0.88 ppm (t, J=6.6 Hz, 18H); 13C-{1H}-NMR
(CDCl3): d=168.06, 153.79, 153.75, 141.09, 125.22, 106.62, 105.97, 73.83,
69.75, 69.57, 32.14, 30.57, 29.96, 29.87, 29.82, 29.63, 29.58, 26.32, 22.91,
14.32 ppm; ESI-MS (+ve): m/z (I%): 1175.67 (100) [M+]; elemental
analysis: calcd (%) for C74H130N2O6S: C 75.58, H 11.14, N 2.38; found:
C 75.73, H 10.95, N 2.35.
2,5-di-(3,4,5-trioctyloxyphenyl)-1,3,4-thiadiazole 9: Yield: 58%; 1H NMR
(CDCl3, 400m): d=7.19 (s, 4H), 4.08 (t, J=6.4 Hz, 8H), 4.04 (t, J=
6.4 Hz, 4H) 1.89–1.74 (m, 12H), 1.56–1.43 (m, 12H), 1.43–1.17 (m, 48H),
0.89 ppm (t, J=6.4 Hz, 18H); 13C-{1H}-NMR (CDCl3): d=167.86, 153.53,
140.83, 125.06, 106.39, 73.63, 69.35, 31.94, 31.87, 30.37, 29.56, 29.38, 29.33,
26.12, 22.71, 14.13 ppm; ESI-MS (+ve): m/z (I%): 1007.9 (100) [M]+; el-
emental analysis: calcd (%) for C62H106N2O6S: C 73.91, H 10.60, N 2.78;
found: C 73.90, H 10.56, N 2.83.
[8] A. Seed, Chem. Soc. Rev. 2007, 36, 2046–2069.
[9] J. Shikuma, A. Mori, K. Masui, R. Matsuura, A. Sekiguchi, H. Ike-
gami, M. Kawamoto, T. Ikeda, Chem. Asian J. 2007, 2, 301–305.
[10] a) M. Parra, S. Villouta, V. Vera, J. Belmar, C. Zuniga, H. Zunza, Z.
Naturforsch. B 1997, 52, 1533–1538; b) M. Sato, R. Ishii, S. Nakashi-
ma, K. Yonetake, J. Kido, Liq. Cryst. 2001, 28, 1211–1214.
[11] a) M. W. Schrçder, S. Diele, G. Pelzl, N. Pancenko, W. Weissflog,
Liq. Cryst. 2002, 29, 1039–1046; b) M. Parra, J. Alderete, C. ZfflÇiga,
Liq. Cryst. 2004, 31, 1531–1537; c) T. Hegmann, B. Neumann, R.
Wolf, C. Tschierske, J. Mater. Chem. 2005, 15, 1025–1034; d) M.
Parra, J. Vergara, P. Hidalgo, J. Barbera, T. Sierra, Liq. Cryst. 2006,
33, 739–745; e) B. Sybo, P. Bradley, A. Grubb, S. Miller, K. J. W.
Proctor, L. Clowes, M. R. Lawrie, P. Sampson, A. J. Seed, J. Mater.
Chem. 2007, 17, 3406–3411; f) C. F. He, G. J. Richards, S. M. Kelly,
A. E. A. Contoret, M. OꢂNeill, Liq. Cryst. 2007, 34, 1249–1267.
[12] a) I. Thomsen, U. Pedersen, P. B. Rasmussen, B. Yde, T. P. Ander-
sen, S. O. Lawesson, Chem. Lett. 1983, 809–810; b) C. T. Liao, Y. J.
2,5-di-(3,4,5-trihexyloxyphenyl)-1,3,4-thiadiazole
10:
Yield:
52%;
1H NMR (CDCl3, 300m): d=7.24 (s, 4H), 4.08 (t, J=6.6 Hz, 8H), 4.03 (t,
J=6.6 Hz, 4H) 1.93–1.72 (m, 12H), 1.55–1.42 (m, 12H), 1.42–1.21 (m,
24H), 0.92 ppm (t, J=6.9 Hz, 18H); 13C-{1H}-NMR (CDCl3): d=169.26,
153.60, 140.93, 124.94, 106.42, 73.61 69.39, 31.74, 31.66, 31.56 25.74, 22.62,
14.01 ppm; ESI-MS (+ve): m/z (I%) 839.51 (100) [M]+; elemental analy-
sis: calcd (%) for C50H82N2O6S: C 71.56, H 9.85, N 3.34; found: C 71.32,
H 9.98, N 3.12.
2,5-di-(3,4,5-tributyloxyphenyl)-1,3,4-thiadiazole
11:
Yield:
61%;
1H NMR (CDCl3, 400m): d=7.20 (s, 4H), 4.08 (t, J=6.4 Hz, 8H), 4.04 (t,
J=6.4 Hz, 4H) 1.87–1.80 (m, 8H), 1.78–1.72 (m, 4H), 1.58–1.49 (m,
12H), 1.00 (t, J=7.2 Hz, 12H), 0.97 ppm (t, J=7.2 Hz, 6H); 13C-{1H}-
NMR (CDCl3): d=167.89, 153.57, 140.95, 125.08, 106.51, 73.26, 69.10,
32.35, 31.40 19.28, 19.18, 13.83 ppm; ESI-MS (+ve): m/z (I%): 671.2
1106
www.chemasianj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Asian J. 2009, 4, 1099 – 1107

Microwave Synthesis and Properties of Thiadiazole Derivatives
Wang, C. S. Huang, H. S. Sheu, G. H. Lee, C. K. Lai, Tetrahedron
2007, 63, 12437–12445.
[16] a) S. Kumar, Liquid Crystals: Experimental Study of Physical Prop-
erties and Phase Transition, Cambridge University Press, 2001; b) I.
Dierking, Textures of Liquid Crystals, Wiley-VCH, Weinheim, 2003.
[17] Y. J. Wang, H. S. Sheu, C. K. Lai, Tetrahedron 2007, 63, 1695–1705.
[18] a) H. X. Zheng, P. J. Carroll, T. M. Swager, Liq. Cryst. 1993, 14,
1421–1429; b) J. Barberµ, R. GimØnez, J. L. Serrano, Chem. Mater.
2000, 12, 481–489; c) J. Barberµ, L. Puig, J. L. Serrano, T. Sierra,
Chem. Mater. 2004, 16, 3308–3317; d) J. Barberµ, M. Bardaji, J. Ji-
menez, A. Laguna, M. P. Martinez, L. Oriol, J. L. Serrano, I. Zarago-
zano, J. Am. Chem. Soc. 2005, 127, 8994–9002; e) E. Cavero, S.
Uriel, P. Romero, J. Serrano, R. GimØnez, J. Am. Chem. Soc. 2007,
129, 11608–11618.
[19] a) D. R. MacFarlane, M. Forsyth, Adv. Mater. 2001, 13, 957–966;
b) J. Z. Sun, D. R. MacFarlane, M. Forsyth, J. Mater. Chem. 2001, 11,
2940–2942.
[20] Y. Queneau, J. Gagnaire, J. J. West, G. Mackenzie, J. W. Goodby, J.
Mater. Chem. 2001, 11, 2839–2844.
[13] a) M. Nüchter, B. Ondruschka, W. Bonrath, A. Gum, Green Chem.
2004, 6, 128–141; b) C. O. Kappe, Angew. Chem. 2004, 116, 6408–
6443; Angew. Chem. Int. Ed. 2004, 43, 6250–6284; c) F. Wiesbrock,
R. Hoogenboom, U. S. Schubert, Macromol. Rapid Commun. 2004,
25, 1739–1764.
[14] a) A. A. Kiryanov, P. Sampson, A. J. Seed, J. Org. Chem. 2001, 66,
7925–7929; b) H.-M. Huang, H.-T. Yu, P.-L. Chen, J. Han, J.-B.
Meng, Chin. J. Org. Chem. 2004, 24, 502–505; c) M. Lebrini, F. Ben-
tiss, M. Lagrenee, J. Heterocycl. Chem. 2005, 42, 991–994.
[15] Crystal data of 1: C34H50N2O2S, Mr =550.82, triclinic, P-1, a=
8.0416(2) ꢃ, b=14.428(3) ꢃ, c=27.726(6) ꢃ, a=83.94(1)8, b=
86.43(1)8, g=75.69(1)8, V=3097.6(1) ꢃ3, Z=4, T=113 K, 1calcd
1.181 gcmꢀ3, mCu=0.137 mmꢀ1, F
(000)=1200, total number of ob-
=
AHCTUNGTRENNUNG
served data [F2 >2s(I)]=13781 and independent reflections 9894
(Rint =0.040). Numbers of parameters=703, Goodness of fit=1.096,
R1 =0.065 and wR2 =0.1426. CCDC 660495 contains the supplemen-
tary crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre at
www.ccdc.cam.ac.uk/data_request/cif.
[21] G. M. Sheldrick, SHELX97 Programs for Crystal Structure Analysis
(Release 97-2). University of Gçettingen, Germany, 1997.
Received: November 24, 2008
Revised: February 6, 2009
Published online: June 2, 2009
Chem. Asian J. 2009, 4, 1099 – 1107
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
1107