Symmetrical 1, 3-Dialkylimidazolium Based Ionic Liquid Crystals

Article abstract of DOI:10.1002/jccs.201200598

The synthesis and characterization for a series of symmetrical 1, 3-dialkylimidazolium salts with different chain lengths and counter anions together with their 1-alkylimidazole precursors are described. Liquid crystal (LC) properties of these salts are studied. Images under polarizing optical microscopy show focal conic texture together with homeotropic domains. A smectic A mesophase, typical for rod-like imida-zolium salts, is assigned. Studies from powder X-ray diffraction suggest a lamellar structure with non-interdigitated monolayer arrangement for the LC salts in the mesophase. In addition, a short note on the structure and property relationship for rod-like, discor fan-like, and dendritic shaped imidazolium ionic liquid crystals (ImILCs) forming smectic, columnar, and cubic phase is briefly summarized. Acomparison of minimum alkyl chain length needed for 1-alkyl-3-methyl and symmetrical 1, 3-dialkyl ImILCs to exhibit LC behavior is addressed.

Full text of DOI:10.1002/jccs.201200598

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
Symmetrical 1,3-Dialkylimidazolium Based Ionic Liquid Crystals
Rondla Rohini, Ching-Kuan Lee, Jung-Tang Lu and Ivan J. B. Lin*
Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
(Received: Nov. 15, 2012; Accepted: Jan. 28, 2013; Published Online: Mar. 11, 2013; DOI: 10.1002/jccs.201200598)
The synthesis and characterization for a series of symmetrical 1,3-dialkylimidazolium salts with different
chain lengths and counter anions together with their 1-alkylimidazole precursors are described. Liquid
crystal (LC) properties of these salts are studied. Images under polarizing optical microscopy show focal
conic texture together with homeotropic domains. A smectic A mesophase, typical for rod-like imida-
zolium salts, is assigned. Studies from powder X-ray diffraction suggest a lamellar structure with non-
interdigitated monolayer arrangement for the LC salts in the mesophase. In addition, a short note on the
structure and property relationship for rod-like, disc- or fan-like, and dendritic shaped imidazolium ionic
liquid crystals (ImILCs) forming smectic, columnar, and cubic phase is briefly summarized. Acomparison
of minimum alkyl chain length needed for 1-alkyl-3-methyl and symmetrical 1,3-dialkyl ImILCs to ex-
hibit LC behavior is addressed.
Keywords: 1-Alkylimidazoles; 1,3-Dialkylimidazolium salts; Synthesis; Liquid crystal property.
INTRODUCTION
Ionic liquids (ILs) have received considerable atten-
with two long alkyl chains are a better choice to obtain
2
8
mesomorphic self-assembled structures. In addition, the
symmetrical imidazolium cation having a flat ionic ring
head, may offer a better opportunity for self-assembly, and
also may be helpful to develop new anisotropic ion conduc-
tive materials and as protecting agents for the preparation
of nanoparticles.
tion because they possess some unique properties such as
negligible vapour pressure, wide liquid range, good elec-
1
-4
tric conductivity and large electrochemical window. Up-
to-date, numerous 1-alkyl-3-methylimidazolium based ILs
and functionalized imidazolium ILs have been reported.
They have been employed as electrolytes for fuel cells,
photochemical cells, and lithium batteries, as stabilizer for
nanoparticles, and as precursors for carbenes; they also
found applications in liquid-liquid extraction, biocatalysis,
In this report, the synthetic procedure for a regular se-
ries of symmetrical 1,3-dialkylimidazolium salts with dif-
-
-
-
-
6
ferent counter anions (Cl , Br , PF , I ) together with their
1-alkylimidazole precursors are presented. The LC behav-
ior of these salts has been determined by differential scan-
ning calorimetry (DSC), polarized optical microscopy
(POM) and powder X-ray diffraction (PXRD) studies.
Overviews on commonly used synthetic methods for 1,3-
dialkylimidazolium salts, the minimum chain lengths re-
quired to exhibit LC behavior and the structure property re-
lationship in rod like imidazolium salts are also provided.
2
,4-12
etc.
When the alkyl chains are suitably extended, ILs
may exhibit liquid crystal properties, and are called ionic
liquid crystals (ILCs). Well-known applications of these
ILCs are in designing anisotropic ion-conductive materi-
1
3-18
19-24
als,
self-assembled nanomaterials,
and as ordered
2
5-27
solvents,
etc. Literature survey reveals that, much of
the attention has been paid on the investigation of the influ-
ence of systematic variation of chain lengths and counter
ions on the LC behavior of 1-alkyl-3-methyl, and function-
RESULTS AND DISCUSSION
Synthesis
2
8,29
alized 1,3-dialkylimidazolium salts.
However, other
than two short communications on LC properties of sym-
In the present study, we synthesized different 1-al-
3
0,31
metrically di-substituted imidazolium salts,
and an arti-
kylimidazoles ([C
salts ([(C -Im] X) with Cl , Br , I and PF
shown in Scheme I. At first, we followed the reported
n
H2n+1-Im]) and 1,3-dialkylimidazolium
-
-
-
-
cle on symmetrical 1,3-dialkylimidazolium ILCs with an-
n
)
2
6
anions as
3
2
ions of metal salts reported by us and others, no further
systematic detailed studies on this subject has been noticed
in the literature. It is well known that, cationic surfactants
3
3
method to synthesize 1-alkylimidazoles. However, mixed
neutral 1-alkylimidazole and ionic 1,3-dialkylimidazoium
th
Special Issue Dedicated to Prof. Yu Wang in Honor of Her 70 Birthday
Corresponding author. Tel: +886-3-863-3599; Fax: +886-3-863-3570; E-mail: ijblin@mail.ndhu.edu.tw
*
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745

Article
Rohini et al.
Scheme I Schematic representation of synthesis of
-alkylimidazoles ([C -Im]) and 1,3-dial-
-Im] X) salts stud-
Scheme II Schematic illustration of reported methods
for the preparation of the symmetrical and
unsymmetrical 1,3-dialkylimidazolium
salts
1
n
kylimidazolium ([(C
ied in this work
n 2
)
salts were obtained due to excess amount of alkyl halide
used. Probably, the alkyl halide reacts first at imidazole ni-
trogen to form a neutral 1-alkylimidazole molecule; the
alkyl group on the imidazole ring would enhance the nu-
cleophilicity of the remaining nitrogen and promote further
reaction of 1-alkylimidazole with alkyl halide to produce
the salt. The preparation method given below produces
1
-alkylimidazole in high yield. A mixture of imidazole
(
10% excess) and alkyl halides in 50 mL THF was stirred at
room temperature. After 48 h, NaOH pellets were added to
the mixture and the mixture was stirred for additional 12 h.
It was then filtered, and the filtrate was extracted twice with
method 2, direct quaternisation of 1-trimethyl silylimida-
zole could be employed to react with two equivalents of
alkyl halide to give the desired symmetrical 1,3-dialkylimi-
5
1,52
CH
2
Cl
2
/H
2
O. The 1-alkylimidazole compounds are misci-
Cl , and any unreacted imidazole will be dis-
dazolium salts in high yield.
In method 3, deprotonation
ble with CH
2
2
of imidazole by NaH, followed by addition of two equiva-
lents of the alkyl bromide precursor usually gives high
solve in water and separated out. In the second step, 1-al-
kylimidazoles were treated with different alkyl halides
without using additional solvent to yield the desired sym-
metrical 1,3-dialkylimidazolium salts. Ion exchange reac-
5
3-55
yield of symmetrical 1,3-dialkylimidazolium salt.
In
the less common method 4, modified Radziszewski reac-
tion involving cyclisation of primary amines, organic acids
with glyoxal and formaldehyde affords 1-3-dialkylimida-
tion of 1,3-dialkylimidazoliumbromide salts with NH
affords corresponding hexafluorophosphate salts. Neutral
-Im] compounds with n = 1 to 14 are liquid, and that of n
16 and 18 are solid. Salts of [(C -Im] X with n = 12, 14
6 and 18 are obtained as solid and the rest of the salts (See
4 6
PF
5
6
zolium salts. The direct quternisation method and modi-
fied Radziszewski reactions could provide more varieties
of salts but is time consuming. Also, the reactions are more
sophisticated, which cannot afford unsymmetrical 1,3-dial-
kylimidazolium salts. Synthetic procedure presented in our
work is little time consuming, but it is easy to purify and
provides good products yields.
[C
n
=
n 2
)
1
scheme I for n values) are sticky liquid. The preparation
methods and characterization details are given in the exper-
imental section. The different 1-alkylimidazoles synthe-
sized here could be used to develop a wide variety of imi-
dazolim based salts.
Thermal properties
The phase transition temperatures of the [(C
n
)
2
-Im] X
-
-
-
-
Scheme II illustrated below provides an overview of
the reported synthetic methods to obtain 1,3-dialkylimida-
zolium salts. In the first method, the popular 1-alkyl-3-
methylimidazolium salts were synthesized by the reaction
of commercially available 1-methyl imidazole with alkyl
halides followed by ion exchange reactions (Method
( X = Cl , Br , I and PF ) salts were determined by DSC at a
6
o
-1
scanning rate of 10 C min and the data is shown in Table
1. The chloride salts with n = 8 and 10 are found to be room
temperature ionic liquid crystals (RTILCs) with clearing
o
points at 78.2 and 126.6 C, respectively; salts of n = 12, 14,
16 and 18 show melting points at 47.1, 64.2, 69.4, and 77.3
3
4-45
o
1
a).
Microwave-assisted techniques under solvent-free
C, and the clearing points at 147.6, 157.8, 165.6, and
4
6-50
o
condition are also known (Method 1b).
As shown in
166.4 C, respectively. In the bromide series, n = 8, 10 and
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JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Symmetrical 1,3-Dialkylimidazolium Salts
Table 1. Phase transition temperatures of [(C ) -Im] X salts
clearing temperatures increase with increasing carbon
chain length. A comparison of different anions in each se-
ries, show that for the shorter chains of n = 8, 10 and 12 are
room temperature or near to room temperature ILCs in the
n 2
o
o
-1
Transition temperature [ C] determined by DSC at a rate of 10 C min
-
1
nd
(
H in kJ mol in parentheses). [2 cycle]
1
-
7.9 (16.2)
43.3(7.4)
78.2(3.5)
76.4(3.6)
(
C ) -Im]Cl· xH O
n=8
Cr
SmA
I
n
2
2
-
-
-
1
26.6(2.6)
23.1(2.6)
6
Cl and Br series but those in the PF series are only room
< 0 o
C
SmA
SmA
SmA
Sm A
SmA
I
n=10
n=12
Cr
Cr
1
temperature or near to room temperature ILs without LC
property. Possibly, when the anion is bulky and the chain
length is short, cation-anion and hydrophobic interactions
4
7.1(25.3)
147 .6 (3 .4 )
143 .8 (3 .4 )
157.8(4.1)
154.3(4.0)
165.6(2.9)
I
5
.3(20.7)
4.2(39.9)
7.3(39.6)
6
2
6
n=14
Cr
Cr
I
9.4(43.3)
are not strong enough to hold the ions to undergo ordered
n=16
n=18
I
4
4.6(43.5)
7.3(57.7)
5.5(58.8)
162.3(2.8)
-
thermal motion. Salts of n = 14, 16 and 18 in the PF
6
series
7
166.4(2.9)
163.0(2.8)
Cr
I
5
have a slightly higher melting temperatures but much lower
4
4
5.4(1.8)
3.1(1.8)
-
-
-
(
Cn)2-Im]B r. H2O
n=8
Cr
< 0 oC
SmA
I
,
clearing temperatures than the Cl Br and I series of salts,
and thus show narrower mesophase ranges. The substantial
decrease in the clearing temperatures again could be attrib-
1
9
00.0(2.5)
6.8(2.6)
< 0 o
C
SmA
SmA
SmA
n=10
n=12
Cr
Cr
I
3
2.0(26.1)
0o
136.9(3.7)
133.2(3.8)
154.1(3.8)
150.9(3.8)
161.4(3.8)
I
57
<
C
uted to the weaker electrostatic interactions. Also noticed
4
2
0.3(48.9)
9.1(49.5)
n=14
n=16
Cr
Cr
Cr
Cr
I
that in each series, there is a sudden drop in the melting
temperature from n = 8 to 10 salts and then rapid increase at
n = 12 salt but the clearing temperatures gradually increase
from n = 8 to 18 salts. Although the details are not certain, a
competition between packing efficiency and van der Waals
5
3.0(60.9)
SmA
SmA
I
4
3.0(61.1)
158.0(3.7)
6
3.4(62.2)
162.4(3.1)
159.5(3.0)
n=18
I
5
5.3(62.3)
19.0 (5.2)
(C ) -Im]PF
n 2 6
n=8a
I
g
-
80.0 (0.2)
27.0(0.4), 16 (6.7)
5
8
-
a
interaction of the chains may answer part of the clues. A
n=10
n=12
n=14
Cr
Cr
I
4
5.1(38.7)
30o
similar trend has been observed for 1-alkyl-3-methyl imi-
I
<
C
2,28,57
dazolium salts.
5
4
6
9.1(45.2)
8.6(43.6)
7.8(47.2)
81.3(2.2)
77.1(2.1)
104.9(2.0)
103.3(2.0)
Cr
Cr
SmA
I
Under polarized optical microscopy (POM), focal
conic fan-shaped textures with homeotropic domains typi-
cal for smectic A are observed and assigned for the ILCs
studied in this work. Fig. 1 shows selected areas of fan-tex-
tures for 1,3-dialkyl imidazolium salts. Results of powder
X-ray diffraction (PXRD) studies are also consistent with
the assignment of smectic A phase. The d-spacing for se-
lected samples are given in Table 2. For example, at room
n=16
n=18
SmA
SmA
SmA
SmA
I
6
1.3(46.1)
6.4(64.6)
7.9(65.1)
7
109.9(2.5)
Cr
I
5
1
03.9(2.7)
5
5
5.4(1.2)
2.0(1.2)
(
Cn)2-Im] I
n=10
n=16
Cr
Cr
0 o
I
<
C
6
3
7.1(45.2)
7.4(47.9)
147.1(2.6)
143.3(2.3)
I
Cr = crystal phase; SmA = smectic A mesophase; I = isotropic phase;
a
g
=
reference 53; = glass transition temperature
2
temperature the diffractogram of solid [(C18) -Im] Cl
1
1
2 salts are RTILCs with clearing points of 45.4, 100.0, and
shows a lamellar structure exhibiting (001), (002) and
(003) reflections, which gives a layer distance of 27.8 Å. At
o
36.9 C, respectively; salts of n = 14, 16 and 18 show the
o
o
corresponding melting points at 40.3, 53.0, and 63.4 C,
110 C in the mesophase, there is an intense (001) and weak
o
and the clearing points at 154.1, 161.4, and 162.4 C, re-
(002) reflections with a corresponding layer distance of
spectively. In the hexafluorophosphate series, salts of n = 8
5
3
and 10 have been reported as RTILs without LC behavior.
The n = 12 salt is a near to RTIL with a melting point of 45.1
o
C; salts of 14, 16 and 18 are ILCs with melting points of
o
5
1
1
9.1, 67.8, 76.4 C, and clearing points at 81.3, 104.9, and
o
09.9 C, respectively. In the iodide series, only salts of n =
0 and 16 are available. The salt of n = 10 is a RTILC with
o
o
melting point below 0 C and a clearing point of 55.4 C.
The salt of n = 16 is an ILC and shows melting and clearing
Fig. 1. Selected area to show the fan-shaped texture
observed for a) [(C -Im]Cl×H O and and b)
(C -Im]Br×H O salts at room temperature by
POM.
8
)
2
2
o
o
points at 67.1 C and 147.1 C respectively. Results de-
scribed above show that in each series, the melting and
[
8
)
2
2
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Article
Rohini et al.
Table 2. PXRD results for the d-spacing (Å) in the mesophases
core is usually required. As a result, many LC compounds
of some [(C ) -Im] X salts
n 2
are based on rod-like, disk-like, ring, bent-core, and cone
o
59-68
RT (25 C)
SmA (Å)
shaped mesogenic aromatic rings.
In contrast, to dis-
o
[
[
(C ) -Im]Cl
-
18.49 (25 C)
play LC behavior for ionic compounds, the structure of
rigid part or mesogen is not crucial. An ionic head group to-
gether with flexible long alkyl chains could induce LC
properties. ILCs of rod-like imidazolium salts have been
extensively studied. Formation of lamellar type structure
consisting alternating hydrophobic and hydrophilic layers
in these materials is commonly recognized. The most com-
mon mesophase observed in these ImILCs is smectic A.
For example, having simple symmetrical 1,3-dialkyl or
8
2
~
4.5
o
(C ) -Im]Cl
27.89
34.01 (110 C)
17.06
18 2
1
3.96
.36
9
11.41
~
4.5
o
[
[
[
(C ) -Im]Br
-
-
19.36 (25 C)
4.5
8
2
~
o
(C ) -Im]Br
23.36 (25 C)
4.5
10 2
~
o
(C ) -Im]Br
27.99
4.12
.339
33.89 (110 C)
16.87
18 2
1
9
1
-alkyl-3-methyl substitutions, and those with one long
11.27
alkyl chain and another with functional groups such as car-
boxyl, vinyl, amide, hydroxyl and ethylene oxide groups
~
4.5
o
[
[
(C ) -Im]PF
6
22.75
1.30
26.87 (75 C)
13.96
14 2
1
are well known rod-like ILCs with smectic A meso-
~
4.5
27-29,69-92
phase.
Imidazolium ring with extended aromatic
o
(C ) -Im] PF
6
24.62
2.37
28.14 (95 C)
14.25
16 2
core based ILC materials are also rod-like and exhibiting
1
9
3
9
~
.53
4.5
smectic A mesophase. To the best of our knowledge, the
only smectic C reported for ImILC is a gemini compound
comprising two imidazolium ions symmetrically bridged
9
4
by an azobenzene. There are also limited examples of
disc- and fan-like imidazolium salts, in which the ionic
head core is tethered with hexaalkoxytriphenylene, hexa-
alkyl triphenylene, trialkyloxybenzyl, trialkyloxybenzo-
3
2
4.0 Å at lower angle region and a broad halo observed at
o
q » 20 , an indication of thermal motion for alkyl chains.
Based on the Chem3D molecular dynamics calculations,
+
2
the single molecular length calculated for (C18) -Im is 41.9
ate, and tetraalkylhexa-peri-benzocoronene types of sub-
Å (Figure 2), which is ~14 Å longer than that at crystal
18,21-23,90,95-107
stituents, show columnar mesophase,
bicon-
o
phase and ~ 8 Å longer than that at 110 C in mesophase.
101
21
tinuous cubic mesophase, and micellar cubic phase.
A
We thus suggest that the molecules are packed in an inter-
report on dendritic benzyl substituted imidazolium salts is
o
digitated monolayer fashion at crystal phase. At 110 C,
1
08
also known, which show cubic mesophase. It is thus, the
geometrical factor of the imidazolium cation significantly
influences the type of mesophase formation.
thermal motion of the alkyl chains could shorten the layer
spacing, therefore noninterdigitated or partial interdigita-
tion of the alkyl chains is likely in the mesophase.
Structure and property relationship
Minimum alkyl chain length addressed
It is well known that, ILC behavior depends on the
type of cation, anion and alkyl chain length. In the case of
To exhibit LC behavior for neutral molecules, other
than flexible alkyl chains, an extended, structurally rigid
1
-alkyl-3-methyl ImILCs, different anions show different
minimum alkyl chain lengths to exhibit LC proper-
1
09,110
ties.
Literature search indicates that the minimum
-
-
-
alkyl chain length required for Cl , Br , BF
4
anion of 1-
alkyl-3-methyl imidazolium salts is C12. For iodide series
no report was found. The minimum chain length required
-
-
for PF
6
and TfO (trifluoromethanesulfonate) based
ImILCs is C14 and C16 respectively. Presumably, a longer
alkyl chain could provide more hydrophobic interaction to
compensate the smaller electrostatic interaction due to the
larger anions. Here, it is also noteworthy to compare the
Fig. 2. The single molecular length calculated for
+
(
C
18
)
2
-Im is 41.9 Å based on Chem3D molecu-
lar dynamics calculations.
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JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Symmetrical 1,3-Dialkylimidazolium Salts
Table 3. The minimum alkyl chain length required for 1-alkyl-3-
NaOH pellets (0.73 g, 18.25 mmol) were added to the mixture and
stirred for additional 12 h. The reaction mixture was then filtered
methyl ImILCs([C MeIm] X) and symmetrical 1,3-
n
dialkyl ImILCs ([(C ) Im]X) to show LC behavior
n 2
and the filtrate was extracted twice with CH
mL), and dried over anhydrous MgSO . The solvent was removed
by a rotary evaporator and the pure 1-octadecyl imidazole (C18
2 2 2
Cl (50 mL)/ H O (15
Counter
anion (X )
[C MeIm]X
[(C ) Im]X
n
n 2
4
-
salts
salts
-
-
Cl
C12
C8
Im) was obtained as white solid. The similar procedure was fol-
-
Br
C12
-
C12
C14
C16
C8
C
10
C12
C14
-
1
lowed for the other compounds. The physical properties, H-
-
I
-
NMR characterization and elemental analysis data of these com-
BF4
PF6
TfO
-
pounds are summarized below. C18-Im. White solid; mp: 45~47
-
1
3
°C; H-NMR (400 MHz, CDCl
3
): d = 0.87 (t, J = 7 Hz, 3H, CH
3
),
Tf
2
N
No LC
behavior
-
3
1
.28-1.29 (m, 30H, CH
2
), 1.74-1.79 (m, 2H, CH
2
), 3.91 (t, J = 7
Hz, 2H, CH
2
), 6.89 (s, 1H, CH), 7.04 (s, 1H, CH), 7.45 (s, 1H,
: C 78.68; H 12.58; N 8.74. Found:
C 78.31; H 12.81; N 8.33. C16-Im. White solid, mp: 38~40 °C;
40 2
CH); Anal. calcd. for C21H N
minimum alkyl chain length needed for LC behavior of
-alkyl-3-methyl ImILCs and symmetrical 1,3-dialkyl
ImILCs (Table 3). In the series of symmetrical 1-3-dialkyl
1
3
H-NMR (400 MHz, CDCl
3
): d = 0.88 (t, J = 7 Hz, 3H, CH
3
),
1
3
1
.24-1.29 (m, 26H, CH
2
), 1.74-1.77 (m, 2H, CH
2
), 3.91 (t, J = 7
Hz, 2H, CH
2
), 6.90 (s, 1H, CH), 7.04 (s, 1H, CH), 7.45 (s, 1H,
-
-
-
ImILCs with Cl , Br and I counter anions, shorter alkyl
chain length is required to induce mesomorphism than in
the 1-alkyl-3-methyl ImILCs, which can be attributed to
the effect of increased hydrophobic interactions by sym-
metrical alkyl chains. In contrary, the minimum require-
ment for the alkyl chain length to sustain LC behavior is the
same in 1-alkyl-3-methyl and symmetrical 1,3-dialkyl
1
CH). C14-Im. Yellow liquid; H-NMR (400 MHz, CDCl
3
): d =
3
0
.88 (t, J = 7 Hz, 3H, CH
3
), 1.22-1.29 (m, 22H, CH
2
), 1.76-1.80
3
(
(
(
m, 2H, CH
2
), 3.91 (t, J = 7 Hz, 2H, CH
2
), 6.90 (s, 1H, CH), 7.05
1
s, 1H, CH), 7.46 (s, 1H, CH). C12-Im. Yellow liquid; H-NMR
3
400 MHz, CDCl
3
): d = 0.87 (t, J = 7 Hz, 3H, CH
3
), 1.20-1.29 (m,
),
3
1
6
8H, CH
2
), 1.74-1.90 (m, 2H, CH
2
), 3.91 (t, J = 7 Hz, 2H, CH
2
.90 (s, 1H, CH), 7.05 (s, 1H, CH), 7.45 (s, 1H, CH). C10-Im. Yel-
-
-
ImILCs of BF
4
and PF
6
series. The keen balance between
1
3
low liquid; H-NMR (400 MHz, CDCl
3
): d = 0.88 (t, J = 7 Hz,
the electrostatic and hydrophobic interactions to maintain
ordered motion in this case is not understood. Further study
is needed to analyze these results.
3
H, CH
3
3
), 1.21-1.29 (m, 14H, CH
2
), 1.75-1.78 (m, 2H, CH ), 3.91
2
(
t, J = 7 Hz, 2H, CH
2
), 6.90 (s, 1H, CH), 7.05 (s, 1H, CH), 7.45 (s,
1
1
0
H, CH). C
8
-Im. Yellow liquid; H-NMR (400 MHz, CDCl
3
): d =
3
.87 (t, J = 7 Hz, 3H, CH
3
), 1.26-1.29 (m, 10H, CH
2
), 1.75-1.77
EXPERIMENTAL
3
(
(
(
m, 2H, CH
2
), 3.91 (t, J = 7 Hz, 2H, CH
2
), 6.90 (s, 1H, CH), 7.05
Chemicals. All chemicals and solvents were purchased
from Aldrich and used as received. NMR spectra were recorded
with a Bruker ACF300 (300 MHz) spectrometer. Chemical shifts
are reported in parts per million (ppm) downfield of tetrameth-
ylsilane (TMS). Elemental analysis was carried out in Perkin-
Elmer 2400, elemental analyzer. DSC analysis was performed us-
ing a Perkin-Elmer DSC 7 differential scanning calorimeter. Opti-
cal studies were carried out using an Olympus BH-2 optical polar-
izing microscope equipped with a Mettler FP82 HT hot stage and
a Mettler FP90 central processor. Powder X-ray diffraction data
were collected on an Inel MPD X-ray diffractometer. The struc-
ture was solved and refined using the Bruker SHELXTL (version
1
s, 1H, CH), 7.45 (s, 1H, CH). C
7
-Im. Yellow liquid; H-NMR
3
400 MHz, CDCl
3
): d = 0.86 (t, J = 7 Hz, 3H, CH
3
), 1.26-1.27 (m,
),
-Im. Yel-
3
8
6
H, CH
2
), 1.72-1.79 (m, 2H, CH
2
), 3.91 (t, J = 7 Hz, 2H, CH
2
.89 (s, 1H, CH), 7.04 (s, 1H, CH), 7.44 (s, 1H, CH). C
6
1
3
low liquid; H-NMR (400 MHz, CDCl
3
): d = 0.87 (t, J = 7 Hz,
3
H, CH
3
), 1.26-1.28 (m, 6H, CH
2
), 1.74-1.80 (m, 2H, CH ), 3.91
2
3
(t, J = 7 Hz, 2H, CH ), 6.70 (s, 1H, CH), 7.04 (s, 1H, CH), 7.45 (s,
2
1
1H, CH). C -Im. Yellow liquid; H-NMR (400 MHz, CDCl ): d =
4
3
3
0.93 (t, J = 7 Hz, 3H, CH ), 1.27-1.37 (m, 2H, CH ), 1.71-1.79
3
2
3
(m, 2H, CH ), 3.92 (t, J = 7 Hz, 2H, CH ), 6.89 (s, 1H, CH), 7.04
2
2
1
(s, 1H, CH), 7.45 (s, 1H, CH). C -Im. Yellow liquid; H-NMR
3
3
(400 MHz, CDCl
(m, 2H, CH
3
): d = 0.92 (t, J = 7 Hz, 3H, CH
3
), 1.77-1.83
3
5
.10) software package.
2
), 3.89 (t, J = 7 Hz, 2H, CH
2
), 6.89 (s, 1H, CH), 7.05
1
Synthesis of 1-alkylimidazoles [C
n
-Im] (n = 2, 3, 4, 6, 7,
(s, 1H, CH), 7.45 (s, 1H, CH). C
2
-Im. Yellow liquid; H-NMR
3
3
8
, 10, 12, 14, 16 and 18). Procedure: The mixture of imidazole
37Br (4.77 g, 14.31 mmol) mixed in
0 mL THF and was stirred at room temperature. After 48 h,
(400 MHz, CDCl
3
): d = 1.45 (t, J = 7 Hz, 3H, CH
3
), 3.99 (q, J =
(
1.08 g, 15.86 mmol) and C18
H
7 Hz, 2H, CH
CH).
2
), 6.92 (s, 1H, CH), 7.05 (s, 1H, CH), 7.48 (s, 1H,
5
J. Chin. Chem. Soc. 2013, 60, 745-754
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.jccs.wiley-vch.de
749

Article
Rohini et al.
3
Synthesis of 1,3-dialkyl imidazolium salts [(C
-
n
)
2
-Im] X
2
CH ), 7.30 (d, J = 1 Hz, 2H, CH), 10.75 (s, 1H, CH); Anal. calcd.
-
X = Cl , Br , PF
-
-
-
, I ). [(C
(
6
n
)
2
-Im]Cl (n = 3, 4, 6, 7, 8, 10, 12, 14,
for C15
H
33
N
2
ClO
2
: C 58.33; H 10.77; N 9.07. Found: C 58.03; H
1
1
6, and 18): The mixture of C16-Im (3.01 g, 10.29 mmol) and
10.75; N 9.05. [(C
4
)
2
-Im]Cl·2H
3
2
O. Sticky liquid; H-NMR (400
o
C
16
H
33Cl (2.96 g, 11.35 mmol) was treated with stirring at 120 C
MHz, CDCl
CH
3
): d = 0.94 (t, J = 8 Hz, 6H, CH
3
), 1.31-1.41 (m, 4H,
), 7.37
ClO : C
3
for 36 h without adding any solvent. After cooling, the mixture
was purified by CH Cl and ether. The white solid product,
(C -Im]Cl was selected and removed the solvent. The similar
2
), 1.84-1.92 (m, 4H, CH
2
), 4.34 (t, J = 8 Hz, 4H, CH
2
2
2
(s, 2H, CH), 10.77 (s, 1H, CH). Anal. calcd. for C11
H
25
N
2
2
[
8
)
2
52.27; H 9.97; N 11.08. Found: C 52.28; H 10.32; N 11.23.
1
procedure was followed for the other salts. The physical proper-
[(C
3
)
2
-Im]Cl·2H
3
2
O. Sticky liquid; H-NMR (400 MHz, CDCl
3
):
3
1
ties, H-NMR characterization and elemental analysis data of
d = 0.99 (t, J = 7 Hz, 6H, CH
3
), 1.92-2.00 (m, 4H, CH
2
), 4.34 (t, J
3
these salts are summarized below. [(C18
)
2
-Im]Cl× H
3
2
O. White
= 7 Hz, 4H, CH
Anal. calcd. for C
C 48.39; H 9.63; N 12.68. [(C
2
), 7.25 (d, J = 1 Hz, 2H, CH), 10.85 (s, 1H, CH);
1
solid; H NMR (ppm, CDCl
3
): d = 0.87 (t, J = 7 Hz, 6H, CH
3
),
9
H
21
N
2
ClO
2
: C 48.10; H 9.42; N 12.47. Found:
-Im]Br (n = 8, 10, 12, 14, 16, and
3
3
1
.23-1.33 (m, 60H, CH
7 Hz, 4 H, CH
Anal. calcd. for C39
2
), 1.91 (m, J = 7 Hz, 4 H, CH
2
), 4.36 (t, J
n
)
2
3
=
2
), 7.18 (d, J = 1Hz, 2 H, CH), 11.14 (s, 1 H, CH);
18): The mixture of C16-Im (2.00 g, 6.84 mmol) and C16H33Br (1.8
o
H
79
N
2
ClO: C 74.65, H 12.69 , N 4.46. Found:
g, 5.9 mmol) was treated with stirring at 120 C for 36 h without
adding any solvent. After cooling, the mixture was purified by
1
C 74.42, H 12.74, N 4.54. [(C16
)
2
-Im]Cl× H
2
O. White solid; H
NMR (ppm, CDCl
3
): d = 0.87 (t, 3J = 7 Hz, 6H, CH
3
), 1.23-1.33
2 2 2
CH Cl and ether. The white solid product, [(C16) -Im] Br was se-
3
3
(
m, 52H, CH
H, CH
calcd. for C35
2
), 1.91 (m, J = 7 Hz, 4 H, CH2), 4.36 (t, J = 7 Hz, 4
lected and removed the solvent. The similar procedure was fol-
3
1
2
), 7.18 (d, J = 1Hz, 2 H, CH), 11.14 (s, 1 H, CH); Anal.
lowed for the other salts. The physical properties, H-NMR char-
H
71
N
2
ClO: C 73.57, H 12.52 , N 4.90. Found: C
acterization and elemental analysis data of these salts are summa-
1
1
7
3.40, H 12.34, N 5.02. [(C14
)
2
-Im]Cl× H
2
O. White solid; H
rized below. [(C18
)
2
-Im]Br× H
2
O. White solid; H NMR (ppm,
3
3
NMR (ppm, CDCl
3
): d = 0.87 (t, J = 7 Hz, 6H, CH
3
), 1.23-1.33
3
CDCl
1.90 (m, J = 7 Hz, 4 H, CH
2H, CH), 10.63 (s, 1 H, CH); Anal. calcd. for C39
3
): d = 0.86 (t, J = 7 Hz, 6H, CH
3
), 1.24-1.32 (m, 60H, CH
2
),
3
3
3
(
m, 44H, CH
H, CH
calcd. for C31
2
), 1.91 (m, J = 7 Hz, 4 H, CH
2
), 4.36 (t, J = 7 Hz, 4
2
), 4.35 (t, J = 7 Hz, 4 H, CH
2
), 7.26 (s,
3
2
), 7.18 (d, J = 1 Hz, 2 H, CH), 11.14 (s, 1 H, CH); Anal.
H
79
N
2
BrO: C
H
63
N
2
ClO: C 72.26, H 12.32 , N 5.44; Found: C
69.71, H 11.85, N 4.17. Found: C 69.50, H 11.87, N 4.23.
1
1
7
2.01, H 12.24, N 5.59. [(C12
)
2
-Im]Cl× H
2
O. White solid; H
[(C16
)
2
-Im]Br× H
2
O. White solid; H NMR (ppm, CDCl
3
): d =
3
3
3
NMR (ppm, CDCl
3
): d = 0.88 (t, J = 7 Hz, 6H, CH
3
), 1.23-1.33
0.86 (t, J = 7 Hz, 6H, CH
3
), 1.24-1.32 (m, 52H, CH
2
), 1.90 (m, J
3
3
3
(
m, 36H, CH
H, CH
calcd. for C27
0.64, H 12.00, N 6.20. [(C10
2
), 1.91 (m, J = 7 Hz, 4 H, CH
2
), 4.36 (t, J = 7 Hz, 4
= 7 Hz, 4 H, CH
2
), 4.35 (t, J = 7 Hz, 4 H, CH
2
), 7.25 (s, 2 H, CH),
3
2
), 7.18 (d, J = 1 Hz, 2 H, CH), 11.05 (s, 1 H, CH); Anal.
10.70 (s, 1 H, CH); Anal. calcd. for C35
H
71
N
2
BrO: 68.26, H 11.62,
H
55
N
2
ClO: C 70.62, H 12.07, N 6.10; Found: C
N 4.55. Found: C 68.30, H 11.10, N 4.66. [(C14
)
2
-Im]Br× H
2
O.
1
3
7
)
2
-Im]Cl× H
2
O. Colorless viscous
White solid; H NMR (ppm, CDCl
3
): d = 0.86 (t, J = 7 Hz, 6H,
1
3
3
liquid; H NMR (ppm, CDCl
3
): d = 0.87 (t, J = 7 Hz, 6H, CH
3
),
CH
3
), 1.24-1.32 (m, 44H, CH
2
), 1.90 (m, J = 7 Hz, 4 H, CH
2
),
3
3
3
1
.23-1.33 (m, 28H, CH
7 Hz, 4 H, CH
Anal. calcd. for C23
2
), 1.91 (m, J = 7 Hz, 4 H, CH
2
), 4.36 (t, J
4.35 (t, J = 7 Hz, 4 H, CH
2
), 7.24 (s, 2 H, CH), 10.74 ( s, 1 H, CH);
3
=
2
), 7.18 (d, J = 1 Hz, 2 H, CH), 11.14 (s, 1 H, CH).
Anal. calcd. for C31
H
63
N
2
BrO: C 66.52, H 11.34, N 5.00. Found:
1
H
47
N
2
ClO: C 68.53, H 11.75 , N 6.95; Found:
C 66.58, H 11.59, N 5.10. [(C12
)
2
-Im]Br× H
2
O. White solid; H
3
C 68.39, H 11.83, N 7.00. [(C
8
)
2
-Im]Cl·H
3
2
O. Sticky liquid;
NMR (ppm, CDCl
(m, 36H, CH
H, CH
3
): d = 0.86 (t, J = 7 Hz, 6H, CH
3
), 1.24-1.32
3
1
3
H-NMR (400 MHz, CDCl
.14-1.33 (m, 20H, CH
7 Hz, 4H, CH
calcd. for C19
3
): d = 0.87 (t, J = 6 Hz, 6H, CH
3
),
2
), 1.90 (m, J = 7 Hz, 4 H, CH
2
), 4.35 (t, J = 7 Hz, 4
3
3
1
2
), 1.91 (m, J = 7 Hz, 4H, CH
2
), 4.36 (t, J
2
), 7.30 (s, 2 H, CH), 10.55 (s, 1 H, CH); Anal. calcd. for
=
2
), 7.17 (s, 2H, CH), 11.03 (s, 1H, CH); Anal.
ClO: C 65.77; H 11.33; N 8.07. Found: C
C
27
H
55
N
2
BrO: C 64.39, H 11.01, N 5.56. Found: C 64.27, H
1
H
37
N
2
11.04, N 5.62. [(C10
)
2
-Im]Br×H
2
O. White solid; H NMR (ppm,
3
6
5.77; H 11.31; N 7.96. [(C
7
)
2
-Im]Cl·H
3
2
O. Sticky liquid;
CDCl
1.99 (m, J = 7 Hz, 4 H, CH
2 H, CH), 10.49 (s, 1 H, CH); Anal. calcd. for C23
3
): d = 0.86 (t, J = 7 Hz, 6H, CH
3
), 1.24-1.32 (m, 28H, CH
2
),
1
3
3
H-NMR (400 MHz, CDCl
3
): d = 0.85 (t, J = 7 Hz, 6H, CH
3
),
2
), 4.33 (t, J = 7 Hz, 4 H, CH
2
), 7.41 (s,
3
1
.24-1.31 (m, 16H, CH
2
), 1.87-1.91 (m, 4H, CH
2
), 4.34 (t, J = 7
H
47
N
2
BrO: C
Hz, 4H, CH
2
), 7.28 (s, 2H, CH), 10.70 (s, 1H, CH); Anal. calcd.
61.73, H 10.59, N 6.26. Found: C 60.97, H 10.71, N 6.16.
1
for C17
H
35
N
2
ClO: C 64.02; H 11.06; N 8.78. Found: C 63.55; H
[(C
8
)
2
-Im]Br×H
(t, J = 7 Hz, 6H, CH
Hz, 4 H, CH
2
O. White solid; H NMR (ppm, CDCl
3
): d = 0.86
1
3
3
11.17; N 8.69. [(C
6
)
2
-Im]Cl·2H
3
2
O. Sticky liquid; H-NMR (400
3
), 1.24-1.32 (m, 20H, CH
2
), 1.99 (m, J = 7
3
MHz, CDCl
CH
3
): d = 0.85 (t, J = 7 Hz, 6H, CH
3
), 1.27-1.99 (m, 12H,
2
), 4.33 (t, J = 7 Hz, 4 H, CH
2
), 7.41 (s, 2 H, CH),
BrO: C 58.30, H
3
3
2
), 1.86-1.91 (m, J = 7 Hz, 4H, CH
2
), 4.34 (t, J = 7 Hz, 4H,
10.49 (s, 1 H, CH); Anal. calcd. for C19
H
39
N
2
750
www.jccs.wiley-vch.de
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J. Chin. Chem. Soc. 2013, 60, 745-754

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Symmetrical 1,3-Dialkylimidazolium Salts
1
0.44, N 7.16. Found: C58.44, H 10.19, N 7.18. [(C
n
)
2
-Im]I (n =
for C23
H
45
N
2
PF
6
: C 55.86, H 9.17, N 5.66. Found: C 55.70, H
1
1
0 and 16): The mixture of C16-Im (2.00 g, 6.84 mmol) and
9.19, N 5.71. [(C
8
)
2
-Im]PF
6
. H NMR (ppm, CDCl
3
): d = 0.88 (t,
o
3
3
C
16
H
33I (2.66 g, 7.55 mmol) was treated with stirring at 120 C for
J = 7 Hz, 6H, CH
3
), 1.19-1.32 (m, 20 H, CH
2
), 1.86 (m, J = 7 Hz,
3
4
3
6 h without adding any solvent. After cooling, the mixture was
4 H, CH
2
), 4.18 (t, J = 7 Hz, 4 H, CH
2
), 7.25 (d, J = 1 Hz, 2 H,
purified by CH Cl and ether. The white solid product, [(C16
2
2
)
2
-
37 2 6
CH), 8.64 (s, 1 H, CH); Anal. calcd. for C19H N PF : C 52.02, H
Im]I was selected and removed the solvent. The similar procedure
8.51, N 6.39. Found: C 51.61, H 8.51, N 6.29.
1
was followed for the other salt. The physical properties, H-NMR
characterization and elemental analysis data of these salts are
CONCLUSIONS
1
summarized below. [(C16
)
2
-Im]I. White solid; H NMR (ppm,
Synthesis and characterization for series of symmet-
rical 1,3-dialkylimidazolium salts and their 1-alkylimida-
zole precursors are presented. The synthetic method pre-
sented in this work affords high yield of the 1-alkylimida-
zole products than the reported methods. The LC properties
of symmetrical 1,3-dialkyl ImILCs with different counter
3
CDCl
3
): d = 0.86 (t, J = 7 Hz, 6H, CH
3
), 1.24-1.32 (m, 52H, CH
2
),
), 7.30 (s,
69 2
H N I: C 65.19,
3
3
1
2
.90 (m, J = 7 Hz, 4 H, CH
2 2
), 4.35 (t, J = 7 Hz, 4 H, CH
H, CH), 10.55 (s, 1 H, CH); Anal. calcd. for C35
H 10.79, N 4.34. Found: C 65.16, H 10.80, N 4.36. [(C10
)
2
-Im]I.
3
1
Pale yellow viscous liquid; H NMR (ppm, CDCl
3
): d = 0.86 (t, J
3
-
-
-
-
-
=
7 Hz, 6H, CH
3
), 1.24-1.32 (m, 28H, CH
2
), 1.90 (m, J = 7 Hz, 4
anions (Cl , Br , I , PF
6 6
) are described. Salts in the PF se-
3
-
-
-
H, CH
2
), 4.35 (t, J = 7 Hz, 4 H, CH
2
), 7.30 (s, 2 H, CH), 10.55 (s,
I: C 57.95, H 9.52, N 5.88.
-Im]PF (n = 10, 12, 14,
and 18): A mixture of 1.00 g, 1.67 mmol of [(C16 -Im] Br and
.40 g, 2.45 mmol of NH PF was dissolved in 3mL of alcohol
95%) / acetone (1:1) and the reaction mixture was stirred and
then allowed to stand 2 to 3 days to give a white precipitate.
ries have narrower mesophase ranges than the Cl Br and I
,
1
H, CH); Anal. calcd. for C23
H
45
N
2
series of salts. Based on POM and PXRD results, smectic A
mesophase with none or partially interdigitated monolayer
structure is suggested for these salts. Structure and prop-
erty relationship account reveals that the lamellar organiza-
tion and smectic A mesophase formation is the characteris-
tic for rod like ImILCs. The comparison of requirement of
minimum alkyl chain length for 1-alkyl-3-methyl ImILCs
and symmetrical 1-3-dialkyl ImILCs to exhibit LC behav-
ior tells that shorter symmetrical alkyl chains could induce
the LC behavior in the halide series of salts. In contrary, the
Found: C 57.52, H 9.56, N 5.89. [(C
n
)
2
6
)
2
0
4
6
(
[
(C16
)
2
-Im]PF
6
.The similar procedure was followed for the other
1
salts. The physical properties, H-NMR characterization and ele-
mental analysis data of these salts are summarized below.
1
3
[
(C18
)
2
-Im]PF
6
. H NMR (ppm, CDCl
3
): d = 0.88 (t, J = 7 Hz,
3
-
-
6
H, CH ), 1.19 - 1.32 (m, 60 H, CH
3
2
), 1.86 (m, J = 7 Hz, 4 H,
4 6
minimum chain length is identical in case of BF and PF
3
4
CH
2
), 4.18 (t, J = 7 Hz, 4 H, CH
2
), 7.24 (d, J = 1 Hz, 2 H, CH),
series of salts. We hope that, the type of symmetrical 1,3-
dialkyl ImILCs may offer better opportunity for self-as-
sembly, and also may be helpful to develop new materials.
We are currently studying the use of these ImILCs to pre-
pare nanoparticles.
8
61 2 6
.69 (s, 1 H, CH); Anal. calcd. for C31H N PF : C 65.15, H 10.79,
1
N 3.90. Found: C 65.65, H 10.96, N 3.91. [(C16
)
2
-Im]PF
6
. H
3
NMR (ppm, CDCl
3
): d = 0.88 (t, J = 7 Hz, 6H, CH
3
), 1.19-1.32
3
3
(
m, 52 H, CH
H, CH
calcd. for C35
2
2
), 1.86 (m, J = 7 Hz, 4 H, CH ), 4.18 (t, J = 7 Hz, 4
4
2
), 7.23 (d, J = 1 Hz, 2 H, CH), 8.69 (s, 1 H, CH); Anal.
H
69
N
2
PF
6
: C 63.42, H 10.49, N 4.23. Found: C
REFERENCES
1
6
3.04, H 10.43, N 4.17. [(C14
)
2
-Im]PF
6
. H NMR (ppm, CDCl
3
):
1. Michel, A.; Frank, E.; Douglas, R. M.; Hiroyuki, O.;
Bruno, S. Nature Mater. 2009, 8, 621-629.
3
d = 0.88 (t, J = 7 Hz, 6H, CH
3
), 1.19-1.32 (m, 44 H, CH
2
), 1.86
3
3
4
2
. Gettanjali, S.; Anil, K. Ind. J. chem. 2008, 47(A),
95-503.
. Lee, S. Chem. Commun. 2006, 1049-1063.
(
m, J = 7 Hz, 4 H, CH
2
), 4.18 (t, J = 7 Hz, 4 H, CH
2
), 7.23 ( d, J =
4
1
5
Hz, 2 H, CH), 8.71 (s, 1 H, CH); Anal. calcd. for C31
61 2 6
H N PF : C
3
9.59, H 10.16, N 4.48. Found: C 59.65, H 10.13, N 4.51.
1
3
4. Seda, K.; Defne, K. T.; Ugur, A.; Oner, H. J. Supercrit.
Fluids 2007, 43, 150-180.
[
(C12
)
2
-Im]PF
H, CH ), 1.19-1.32 (m, 36 H, CH
), 4.18 (t, J = 7 Hz, 4 H, CH
.64 (s, 1 H, CH); Anal. calcd. for C27
6
. H NMR (ppm, CDCl
3
): d = 0.88 (t, J = 7 Hz,
3
6
3
2
), 1.86 (m, J = 7 Hz, 4 H,
5
6
7
. Hajipour, A. R.; Rafiee, F. J. Iran. Chem. Soc. 2009,
(4), 647-678.
3
4
CH
2
2
), 7.25 (d, J = 1 Hz, 2 H, CH),
6
8
H
53
N
2
PF
6
: C 58.89, H 9.70,
. Subbiah, S.; Venkatesan, S.; Ming, C. T.; Yen Ho, C.
Molecules 2009, 14(9), 3780-3813.
1
N 5.09. Found: C 58.77, H 9.83, N 5.11. [(C10
)
2
-Im]PF
6
. H NMR
3
(
ppm, CDCl
3
): d = 0.88 (t, J = 7 Hz, 6H, CH
3
), 1.19-1.32 (m, 28
. Cinzia, C.; Daniela, P. J. Phys. Org. Chem. 2005, 18,
275-297.
3
3
H, CH
CH
2
), 1.86 (m, J = 7 Hz, 4 H, CH
2
), 4.18 (t, J = 7 Hz, 4 H,
4
2
), 7.23 (d, J = 1 Hz, 2 H, CH), 8.64 (s, 1 H, CH); Anal. calcd.
8. Jeong, Y.; Kim, D. Y.; Choi, Y.; Ryu, J. S. Org. Biomol.
J. Chin. Chem. Soc. 2013, 60, 745-754
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.jccs.wiley-vch.de
751

Article
Rohini et al.
Chem. 2011, 9, 374-378.
Chem. Commun. 2009, 7405-7407.
9
. Bara, J. E.; Gabriel, C. J.; Hatakeyama, E. S.; Carlisle,
T. K.; Lessmann, S.; Noble, R. D.; Gin, D. L. J. Membr.
Sci. 2008, 321, 3-7.
32. Lee, C. K.; Peng, H. H.; Lin, I. J. B. Chem. Mater. 2004,
16, 530-536.
33. Wilkinson, C. F.; Krystyna, H.; Cantwell, G. P.; Freder-
ick, J. D. C. Biochem. Pharmacol. 1974, 23, 2377-2386.
34. Zhao, D.; Fei, Z.; Ohlin, C. A.; Laurenczy, G.; Dyson, P.
J. Chem. Commun. 2004, 2500-2501.
1
0. Amanda, C. C.; Jessica, L. J.; Ioanna, N.; Kim Loan, T.
T.; Kristin, J. W.; David, C. F.; James, H. D. J. Am.
Chem. Soc. 2002, 124, 5962-5963.
1
1. Jadhav, V. H.; Jeong, H. J.; Lim, S. T.; Sohn, M. H.;
35. Kubisa, P. Prog. Polm. Sci. 2004, 29, 3-12.
36. Dzyuba, S. V.; Bartsch, R. A. J. Heter. Chem. 2001, 38,
265-268.
Kim, D. W. Org. Lett. 2011, 13, 2502-2505.
1
2. Bellina, F.; Bertoli, A.; Melai, B.; Scalesse, F.; Signori,
F.; Chiappe, C. Green Chem. 2009, 11, 622-629.
3. Kato, T. Science 2002, 295, 2414-2418.
37. Wilkes, J. S.; Levinsky, J. A.; Wilson, R. A.; Hussey, C.
L. Inorg. Chem. 1982, 21, 1263-1264.
1
1
4. Ohtake, T.; Ogasawara, M.; Ito Akita, K.; Nishina, N.;
Ujiie, S.; Ohno, H.; Kato, T. Chem. Mater. 2000, 12,
38. Welton, T. Chem. Rev. 1999, 99, 2071-2083.
39. Wasserscheid, P.; Keim, W. Angew. Chem. Int. Ed. Engl.
2000, 39, 3772-3789.
7
82-789.
1
5. Yoshizawa, M.; Mukai, T.; Ohtake, T.; Kiyoshi, K.;
40. Jain, N.; Kumar, A.; Chauhan, S.; Chauhan, S. M. S. Tet-
rahedron 2005, 61,1015-1060.
Kato, T.; Ohno, H. Solid State Ionics 2002, 779,
1
54-155.
41. Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev.
2002, 102, 3667-3692.
1
1
6. Yoshio, M.; Mukai, T.; Kanie, K.; Yoshizawa, M.;
Ohno, H.; Kato, T. Adv. Mater. 2002, 14, 351-354.
42. Zhang, D.; Chen, J.; Liang Y.; Zhou, H. Synth. Commun.
2005, 35, 521-526.
7. Kishimoto, K.; Yoshio, M.; Mukai, T.; Yoshizawa, M.;
Ohno, H.; Kato, T. J. Am. Chem. Soc. 2003, 125,
43. Min, G. H.; Yim, T.; Lee, H. Y.; Huh, D. H.; Lee, E.;
Mun, J.; Oh, S. M.; Kim, Y. G. Bull. Korean Chem. Soc.
2006, 27(6), 847-852.
3
196-3197.
1
1
2
2
8. Yoshio, M.; Mukai, T.; Ohno, H.; Kato, T. J. Am. Chem.
Soc. 2004, 126, 994-995.
44. Burrell, A. K.; Sesto, R. E. D.; Baker, S. N.; McCleskey
T. M.; Baker G. A. Green Chem. 2007, 9, 449-454.
45. Zoller, U. Tetrahedron 1988, 44, 7413-7426.
46. Deetlefs, M.; Seddon, K. R. Green Chem. 2003, 5,
181-186.
9. Ujiie, S.; Iimura, K. Macromolecules 1992, 25,
3
174-3178.
0. Faul, C. F. J.; Antonietti, M. Adv. Mater. 2003, 15,
73-683.
6
1. Yazaki, S.; Kamikawa, Y.; Yoshio, M.; Hamasaki, A.;
47. Varma, R. S.; Namboodiri, V. V. Chem. Commun. 2001,
643-645.
Mukai, T.; Ohno, H.; Kato, T. Chem. Lett. 2008, 37,
5
38-539.
48. Cravotto, G.; Gaudino, E. C.; Boffa, L.; Leveque, J. M.;
Estager, J.; Bonrath, W. Molecules 2008, 13, 149-156.
49. Rajender, S. V.; Vasudevan, V. N. Pure Appl. Chem.
2001, 73(8), 1309-1313.
2
2
2. Yoshio, M.; Kagata, T.; Hoshino, K.; Mukai, T.; Ohno,
H.; Kato, T. J. Am. Chem. Soc. 2006, 128, 5570-5577.
3. Yoshio, M.; Ichikawa, T.; Shimura, H.; Kagata, T.;
Hamasaki, A.; Mukai, T.; Ohno, H.; Kato, T. Bull.
Chem. Soc. Jpn. 2007, 80, 1836-1841.
50. Aupoix, A.; Pegotb, B.; Thanh, G. V. Tetrahedron 2010,
66, 1352-1356.
2
2
4. Camerel, F.; Faul, C. F. J. Chem. Commun. 2003, 1515,
51. Harlow, K. J.; Hill, A. F.; Welton, T. Synthesis 1996,
697-698.
1
958-1959.
5. Reichardt, C. Solvent and Solvent Effects in Organic
52. Wang, X.; Heinemann, F. W.; Mudring, A. V.; Yang, M.;
Wasserscheid, P.; Melcher, B. U.; Meyer, K.; Fekete, M.
Chem. Commun. 2009, 7405-7407.
rd
Chemistry, 3 ed.; Wiley-VCH: Weinheim, 2003; pp
2
98-303.
2
2
6. Weiss, R. G. Tetrahedron 1988, 44, 3413-3475.
53. Dzyuba, S. V.; Bartsch, R. A. Chem. Commun. 2001,
1466-1467.
7. Lee, C. K.; Huang, H. W.; Lin, I. J. B. Chem. Commun.
2
000, 1911-1912.
54. Chan, B. K. M.; Chang, H. H.; Grimmett, M. R. Aust. J.
Chem. 1977, 30, 2005-2013.
2
2
3
8. Binnemans, K. Chem. Rev. 2005, 105, 4148-4204.
9. Axenov, K. V.; Laschat, S. Materials 2011, 4, 206-259.
0. Lee, K. M.; Lee, C. K.; Lin, I. J. B. Chem. Commun.
55. Lee, H. M.; Lu, C. Y.; Chen, C. Y.; Chen, W. L.; Lin, H.
C.; Chiu, P. L.; Cheng, P. Y. Tetrahedron 2004, 60,
5807-5825.
1
997, 899-900.
3
1. Wang, X.; Heinemann, F. W.; Mudring, A. V.; Yang, M.;
Wasserscheid, P.; Melcher, B. U.; Meyer, K.; Fekete, M.
56. Zimmermann, J.; Ondruschka, B.; Stark, A. Org. Pro-
cess Res. Dev. 2010, 14, 1102-1109.
752
www.jccs.wiley-vch.de
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
J. Chin. Chem. Soc. 2013, 60, 745-754

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Symmetrical 1,3-Dialkylimidazolium Salts
5
5
7. Knight, G. A.; Shaw, B. D. J. Chem. Soc. 1938, 682-683.
8. Lava, K.; Evrard, Y.; Hecke, K. V.; Meervelt, L. V.;
Binnemans, K. RSC Adv. 2012, 2, 8061-8070.
80. Luo, S. C.; Sun, S.; Deorukhkar, A. R.; Lu, J. T.;
Bhattacharyya, A.; Lin, I. J. B. J. Mater. Chem. 2011,
21, 1866-1873.
5
6
6
6
9. Tang , J.; Huang, R.; Gao, H.; Cheng, X.; Prehm, M.;
Tschierske, C. RSC Adv., 2012, 2, 2842-2847.
81. Lin, J. C. Y.; Huang, C. J.; Lee, Y. T.; Lee, K. M.; Lin, I.
J. B. J. Mater. Chem. 2011, 21, 8110-8121.
82. Seo, S. H.; Tew, G. N.; Chang, J. Y. Soft Matter 2006, 2,
886-891.
0. Beltran, E.; Serrano, J. L.; Sierra, T.; Gimenez, R. J.
Mater. Chem. 2012, 22, 7797-7805.
1. Zou, S.; Luo, J.; He, L.; Wang, Y.; Zhang, J.; He, W. F.
Y.; Yuan, L.; Wu, L. Org. lett. 2012, 14, 3584-3587.
2. Cammidge, A. N.; Bushby, R. J. In Handbook of Liquid
Crystals; Demus, D.; Goodby, J.; Gray, G. W.; Spiess, H.
W.; Vill, V., Eds.; Wiley-VCH: Weinheim, 1998; Vol.
83. Seo, S. H.; Park, J. H.; Chang, J. Y. Langmuir 2009, 25,
8439-8441.
84. Yoshio, M.; Mukai, T.; Kanie, K.; Yoshizawa, M.;
Ohno, H.; Kato, T. Chem. Lett. 2002, 31, 320-321.
85. Zhao, Y. R.; Chen, X.; Wang, X. D. J. Phys. Chem. B
2009, 113, 2024- 2030.
2
B, pp 715-749.
3. Sato, K.; Itoh, Y.; Aida, T. J. Am. Chem. Soc. 2011, 133,
3767-13769.
6
6
6
6
6
6
86. Sanami, Y.; Funahashi, M.; Kato, T. J. Am. Chem. Soc.
2008, 130, 13206 -13207.
1
4. Stepien, M.; Donnio, B.; Sessler, J. L. Angew. Chem. Int.
Ed. 2007, 46, 1431-1435.
87. Hoshino, K.; Yoshio, M.; Mukai, T.; Kishimoto, K.;
Ohno, H.; Kato, T. J. Polym. Sci. Part A 2003, 41,
3486-3492.
5. Reddy, R. A.; Tschierske, C. J. Mater. Chem. 2006, 16,
9
07-961.
88. Goossens, K.; Nockemann, P.; Driesen, K.; Driesen, K.;
Goderis, B.; Walrand, C. G.; Hecke, K. V.; Meervelt, L.
V.; Pouzet, E.; Binnemans, K.; Cardinaels, T. Chem.
Mater. 2008, 20, 157-168.
6. Seltmann, J.; Marini, A.; Mennucci, B.; Dey, S.; Kumar,
S.; Lehmann, M. Chem. Mater. 2011, 23, 2630-2636.
7. Kato, T.; Mizoshita, N.; Kishimoto, K. Angew. Chem.
Int. Ed. 2006, 45, 38-68.
89. Zhang, Q. X.; Shan, C. S.; Wang, X. D.; Chen, L. L.;
Niu, L.; Chen, B. Liq. Cryst. 2008, 35, 1299-1305.
90. Yoshizawa, H.; Mihara, T.; Koide, N. Liq. Cryst. 2005,
32, 143-149.
8. Percec, V.; Cho, W. D.; Moller, M.; Prokhorova, S. A.;
Ungar, G.; Yeardley, D. J. P. J. Am. Chem. Soc. 2000,
1
22, 4249-4250.
9. Li, X.; Bruce, D. W.; Shreeve, J. N. M. J. Mater. Chem.
009, 19, 8232-8238.
6
7
91. Fouchet, J.; Douce, L.; Heinrich, B.; Welter, R.; Louati,
A. Beilstein J. Org. Chem. 2009, 5, 51.
2
0. Dobbs, W.; Douce, L.; Allouche, L.; Louati, A.;
92. Osuji, C. O.; Chao, C. Y.; Ober, C. K.; Thomas, E. L.
Macromolecules 2006, 39, 3114-3117.
Malbosc, F.; Welter, R. New J. Chem. 2006, 30,
5
28-532.
1. Tosoni, M.; Laschat, S.; Baro, A. Helv. Chim. Acta
004, 87, 2742 -2749.
93. Kouwer, P. H. J.; Swager, T. M. J. Am. Chem. Soc. 2007,
129, 14042-14052.
7
7
7
2
94. Zhang, Q.; Shan, C.; Wang, X.; Chen, L.; Niu, L.; Chen,
B. Liq. Cryst. 2008, 35, 1299-305.
2. Suisse, J. M.; Laponnaz, S. B.; Douce, L.; Francois, A.
M.; Welter, R.Tetrahedron Lett. 2005, 46, 4303-4305.
3. Suisse, J. M.; Douce, L.; Laponnaz, S. B.; FranAois, A.
M.; Welter, R.; Miyake, Y.; Shimizu, Y. Eur. J. Inorg.
Chem. 2007, 3899-3905.
95. Kumar, S.; Pal, S. K. Tetrahedron Lett. 2005, 46,
2607-2610.
96. Yoshio, M.; Mukai, T.; Ohno, H.; Kato, T. J. Am. Chem.
Soc. 2004, 126, 994-995.
7
7
7
4. Seo, S. H.; Park, J. H.; Tew, G. N.; Chang, J. Y. Tetrahe-
dron Lett. 2007, 48, 6839-6844.
97. Yoshio, M.; Kagata, T.; Hoshino, K.; Mukai, T.;
Ohno, H.; Kato, T. J. Am. Chem. Soc. 2006, 128,
5570-5577.
5. Zhang, Q.; Jiao, L.; Shan, C.; Hou, P.; Chen, B.; Xu, X.;
Niu, L. Liq. Cryst. 2008, 35, 765-772.
98. Cui, L.; Zhu, L. Liq. Cryst. 2006, 33, 811-818.
99. Hamaoui, B. E.; Zhi, L. J.; Pisula, W.; Kolb, U.; Wu, J.;
Mllen, K. Chem. Commun. 2007, 2384-2386.
100. Pal, K. S.; Kumar, S. Tetrahedron Lett. 2006, 47,
8993-8997.
6. Wang, X.; Heinemann, F. W.; Yang, M.; Melcher, B. U.;
Fekete, M.; Mudring, A. V.; Wasserscheid, P.; Meyer, K.
Chem. Commun. 2009, 7405-7407.
7
7
7
7. Gordon, C. M.; Holbrey, J. D.; Kennedy, A. R.; Seddon,
K. R. J. Mater. Chem. 1998, 8, 2627-2636.
101. Alam, M. A.; Motoyanagi, J.; Yamamoto, Y.;
Fukushima, T.; Kim, J.; Kato, K.; Takata, M.; Saeki, A.;
Seki, S.; Tagawa, S.; Aida, T. J. Am. Chem. Soc. 2009,
131, 17722-17723.
8. Lee, K. M.; Lee, Y. T.; Lin, I. J. B. J. Mater. Chem. 2003,
1
3, 1079-1084.
9. Chiou, J. Y. Z.; Chen, J. N.; Lei, J. S.; Lin, I. J. B. J. Ma-
ter. Chem. 2006, 16, 2972-2977.
102. Olivier, J. H.; Camerel, F.; Barbera, J.; Retailleau, P.;
J. Chin. Chem. Soc. 2013, 60, 745-754
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.jccs.wiley-vch.de
753

Article
Rohini et al.
Ziessel, R. Chem. Eur. J. 2009, 15, 8163-8174.
03. Shimura, H.; Yoshio, M.; Hoshino, K.; Mukai, T.; Ohno,
R. Chem. Eur. J. 2010, 16, 7134-7142.
1
1
1
108. Imam, M. R.; Peterca, M.; Edlund, U.; Balagurusamy, V.
S. K.; Percec, V. J. Polym Sci. Part A 2009, 47,
4165-4193.
H.; Kato, T. J. Am. Chem. Soc. 2008, 130, 1759-1765.
04. Santanu, K. P.; Sandeep, K. Liq. Cryst. 2008, 35,
3
81-384.
05. Sandeep, K.; Satyam, K.G. Tetrahedron Lett. 2010, 51,
459-5462.
109. Bradley, A. E.; Hardacre, C.; McMath, S. E. J.; Holbrey,
J. D.; Johnston, M. N. S. Chem. Mater. 2002, 14,
629-635.
5
1
1
06. Li, C.; Lei, Z. Liq. Cryst. 2006, 33, 811-818.
110. Holbrey, J. D.; Seddon, K. R. J. Chem. Soc., Dalton
Trans. 1999, 2133-2139.
07. Olivier, J. H.; Camerel, F.; Ulrich, G.; Barber J.; Ziessel,
754
www.jccs.wiley-vch.de
© 2013 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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