Mesomorphic and ion conducting properties of dialkyl(1,4-phenylene) diimidazolium salts

Article abstract of DOI:10.1039/c2sm26213d

A new family of dialkyl(1,4-phenylene)diimidazolium salts has been synthesized. Salts containing triflate and bis(trifluoromethanesulfonyl)imide anions and different alkyl chains have been prepared. The molecular structures of didodecyl(1,4-phenylene)diim

Full text of DOI:10.1039/c2sm26213d

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PAPER
Mesomorphic and ion conducting properties of dialkyl(1,4-phenylene)
diimidazolium salts†
Nadim Noujeim, Salim Samsam, Ludovic Eberlin, Samantha H. Sanon, Dominic Rochefort
and Andreea R. Schmitzer*
Received 25th May 2012, Accepted 15th August 2012
DOI: 10.1039/c2sm26213d
A new family of dialkyl(1,4-phenylene)diimidazolium salts has been synthesized. Salts containing
triflate and bis(trifluoromethanesulfonyl)imide anions and different alkyl chains have been prepared.
The molecular structures of didodecyl(1,4-phenylene)diimidazolium triflate and
bis(trifluoromethylsulfonyl)imide salts were determined by single crystal X-ray diffraction, and the
mesomorphic and ionic conducting properties of all these compounds were investigated and are
reported here.
Introduction
Recently, imidazolium-based thermotropic and lyotropic ionic
10
liquid crystals (ILCs) were reported. These imidazolium-based
ILCs were obtained by combining the self-organization proper-
ties of liquid crystals (LCs) with the unique solvent properties
and ion-conducting properties of imidazolium ILs. The proper-
ties of ILCs can be significantly different from those of conven-
One of the major goals of materials science is the development of
anisotropic ion-conductive materials. Ionic liquids (ILs) have
shown many useful properties such as high thermal and chemical
stability, low volatility, non-flammability and a wide electro-
1
chemical window. Imidazolium-based ionic liquids are well
11
tional liquid crystals, and more specifically, the properties of
known and have already found wide applications in electro-
chemical devices, ion transport systems and dye-sensitized solar
2
cells. Some imidazolium-based ILs have also recently been
imidazolium-based ILCs can also drastically change depending
on the molecular architecture and the counterion used. More
importantly, development of ILCs led to the achievement of
anisotropic ionic conductivity through macroscopically aligning
the ionic channels.
shown to be useful in catalysis, either as solvents for bioorganic
3
4
catalysis or as emulsion regulators in biphasic processes. In an
attempt to translate the benefits of ILs to the ion-conductive
materials, polymer electrolytes, ionogels and ionic liquid crystals
have been recently developed.
Imidazolium-based ILCs can currently be classified into three
main categories that overlap to some extent: firstly, ILCs
comprised of an imidazolium moiety with one or two alkyl
Different polymer electrolytes obtained by polymerization of
12
chains incorporating in some cases an aromatic ring generally
5
ILs, inclusion of different polymers in ionic liquids, ionic liquid–
6
exhibit smectic mesophases. The imidazolium moiety can also
directly be part of the rigid core unit and smectic phases are
13
7
polyelectrolyte systems, and polymer gel electrolytes containing
8
hydrophilic and hydrophobic ionic liquids, have been reported to
generally obtained when an alkyl chain is attached. The second
possess high conductivity suitable for different applications.
Ion gels, which have the main properties of ILs except outflow,
represent a promising family of solid electrolyte membranes,
which gives access to a large panel of devices and potential
applications as lithium batteries, fuel cells and dye sensitized
category is comprised of taper shaped imidazolium salts with
14
multiple alkyl chains, with properties related to their strong
amphiphilic character and space filling of the lipophilic chains.
The third category is comprised of rod like and disc like meso-
gens containing one or several imidazolium units that are con-
9
solar cells. However, polymer electrolytes and ionogels do not
15
nected to each other by long flexible spacers, where smectic and
present any conductive anisotropy. There is still a challenging
need for obtaining stable materials over time and allowing their
use at temperatures much higher than ambient, while presenting
anisotropic conductive properties.
columnar phases are usually obtained.
We report here the synthesis and study of a symmetrical type
of imidazolium-based ILC in which the rigid core is composed of
a diimidazolium 1,4-disubstituted phenyl ring with two long
alkyl chains attached to this central core, one on each imidazo-
lium moiety. The length of the alkyl chains and the nature of the
counterion were varied in order to investigate their influence on
the mesomorphic properties and ion conducting properties of
these salts (Scheme 1).
D eꢀ partement de Chimie, Universit eꢀ de Montr eꢀ al, 2900 Edouard Montpetit
CP 6128 Succursale centre ville, Montr eꢀ al H3C3J7, Qc, Canada. E-mail:
ar.schmitzer@umontreal.ca; Fax: +1 514-343-7586; Tel: +1 514-343-6744
†
Electronic supplementary information (ESI) available: CCDC 884299
and 884300. For ESI and crystallographic data in CIF or other
electronic format see DOI: 10.1039/c2sm26213d
1
0914 | Soft Matter, 2012, 8, 10914–10920
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very common for this type of diimidazolium salts, as previously
17
described by our research group. For compound 2a, the alkyl
ꢁ
chains are separated from each other by 4.4 A in the (bc) plane,
ꢁ
and by 8.5 A along the (a) axis, which shows a lamellar structure.
The symmetry within the crystal and the angles between the
imidazolium moieties and the alkyl chains give a unique S-like
shape to the molecule. This class of diimidazolium salts cannot
be described as a rod or cylinder-shaped molecule, but as one
Scheme 1 Dialkyl(1,4-phenylene)diimidazolium salts.
ꢁ
containing two 16 A long cylinders linked to a smaller 10 A
ꢁ
ꢀ
cylinder with angles of 45 between them. The interpenetration of
Results and discussion
the alkyl sidechains is not complete, and a four-carbon gap can
be observed. For example, the C4 of a side-chain is closer to the
C8 of the next sidechain (Fig. 1).
Synthesis
We previously reported the synthesis and supramolecular
assemblies of dialkyl(1,4-phenylene)diimidazolium bromide salts
The interaction between the imidazolium rings and the TfO
anions are weak but can still be observed: an H-bond is observed
between the H2 of the imidazolium ring and an oxygen atom of
16
with short alkyl chains. These compounds did not exhibit any
mesomorphic properties. Furthermore, by increasing the length
of the alkyl chains while keeping bromide counterions, it was still
not possible to obtain mesomorphic materials. It was only when
simultaneously changing both the counterions and increasing the
alkyl sidechains (to at least twelve carbons) that compounds
displaying LC properties were obtained. The mesophases were
stable in a very large temperature range depending on the
counterion used.
ꢁ
the triflate counterion. The calculated distance was 2.14 A, which
classifies this interaction as a moderate CH/O hydrogen bond
(
Fig. 2).
The 3D organization of the bis(trifluoromethylsulfonyl)imide
(
2
NTf ) salt 3a is more complex: hydrophobic interactions govern
the packing in one direction while the H-bonds and the electro-
static forces are the main interactions in another direction
(
Fig. 3). Furthermore, no p-stacking or T-stacking was observed
These compounds were synthesized in a three-step procedure.
The first step is a copper(I) catalyzed Ullman-type coupling
carried out in anhydrous acetonitrile. The second step is a double
nucleophilic substitution of either 1-bromododecane or 1-bro-
mohexadecane on the diimidazole intermediate. This step yielded
dialkyl(1,4-phenylene)diimidazolium bromide salts 1a and 1b
which were engaged in anion metathesis to afford compounds 2a
and 2b, and 3a and 3b (Scheme 2). All the salts were air stable and
ꢁ
either. The alkyl chains are separated from each other by 4.6 A in
the (bc) plane and only a two-carbon gap can be observed in the
interpenetration of the sidechains. The two imidazolium cations
of the dicationic core are still in a trans conformation relative to
one another, and all the hydrogens (H2, H4 and H5) are involved
in relatively weak H-bonds with the counterion (Fig. 4).
Four moderate to weak different hydrogen bonds can be
observed in the crystal structure: the H2 and H4 of the imida-
zolium moieties are hydrogen bonded to an oxygen atom of the
1
13
were characterized by H, C NMR and high resolution mass
spectrometry.
ꢁ
counterion (2.49 A and 2.31 A) while H5 is hydrogen bonded to a
ꢁ
ꢁ
fluorine atom of the counterion (2.48 A). There is also a
Solid state organization of 2a and 3a
The single crystal X-ray structures of compounds 2a and 3a were
obtained and investigated to understand the supramolecular
organization of these salts in the solid state. For compound 2a,
the predominant supramolecular interactions observed in the
crystal are the hydrophobic interactions between the alkyl chains
and the H-bonds between the acidic H2 imidazolium proton and
the oxygen atom of the triflate (TfO) anion. No p-stacking or T-
stacking was observed in this crystal structure, which is usually
Scheme 2 Synthesis of the dialkyl(1,4-phenylene)diimidazolium salts. (i)
Cs
1%; (ii) alkyl bromide, acetonitrile, reflux, 12 h, 95–99%; (iii)
NH CF SO or LiN(SO CF , water–methanol, r.t. 30 min 67–88%.
2
CO
3
, imidazole, Cu
2
O, salycilaldoxime, acetonitrine, reflux, 48 h,
Fig. 1 Top: partial crystal packing of the compound 2a projected on the
(bc) plane showing the hydrophobic interactions in the crystal. Bottom:
partial crystal packing of 2a showing the lamellar structure.
8
4
3
3
2
3 2
)
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Liquid crystal properties
While compounds 1a and 1b decompose before their fusion
points, no other transition to a mesophase was observed before
their decomposition. Thermogravimetric analyses of compounds
2
a and 2b, and 3a and 3b showed that they were stable in a wide
temperature range (ESI†). More precisely, compounds 2a and 2b
ꢀ
started to degrade around 250 C with the main degradation
ꢀ
peak observable around 320 C by TGA. However, if heated at
ꢀ
or slightly above 250 C and then cooled down, the mesomorphic
properties were lost. Compounds 3a and 3b, on the other hand,
ꢀ
were completely stable up to 350 C.
The TfO salts 2a and 2b exhibited two phase transitions below
Fig. 2 Crystal structure of compound 2a showing the supramolecular
2
the isotropic phase, while the NTf salts 3a and 3b exhibited only
interactions between the imidazolium cations and the triflate anions.
one transition, but at a lower temperature. For all the
compounds, their mesomorphic properties and phase transition
temperatures were investigated by differential scanning calo-
rimetry (DSC), polarizing optical microscopy (POM), and
powder X-ray diffractometry (PXRD). To avoid hydration of
the imidazolium salts, all the compounds were dried under
vacuum before PXRD and DSC analyses (ESI†). The phase
transition temperatures and the corresponding enthalpy changes
derived for compounds 2a and 2b, and 3a and 3b in both heating
and cooling cycles are shown in Table 1.
Results are summarized in Chart 1 for a visual comparison of
the phase transition temperatures. For 2a and 2b, phase transi-
tions were investigated by PXRD and POM (Fig. 5). Compound
2
a exhibited a fan-shaped texture often seen in SmC phases. This
texture was observed on cooling from the isotropic melt between
ꢀ
1
81 and 153 C.
Compound 2b predominantly exhibited a focal conic fan
texture upon cooling from the isotropic melt, but other types of
D organization (e.g. a different orientation of the director of the
Fig. 3 Top: crystal packing of the compound 3a projected on the (bc)
2
plane showing the hydrophobic interactions. Bottom: crystal packing of
focal conic aggregates) were also present simultaneously in the
sample (Fig. 6). One sharp reflection in the small angle region
related to the smectic layering, as well as a broad band in the wide
angle region, related to the disordered alkyl chains and possibly
3a showing the 2D organization.
Table 1 Phase transition temperatures and corresponding enthalpies
DH determined from 2 heating and 1 cooling DSC thermograms
nd
st
ꢀ
ꢀ
ꢀ
Compound T/ C (Cr1 / Cr2) T/ C (Cr2 / LC) T/ C (LC / I)
a
ꢁ1
ꢁ1
ꢁ1
)
on heating
(DH/J g
)
(DH/J g
)
(DH/J g
2a
2b
3a
3b
148 (26.9)
141
—
—
169 (42.9)
149
55 (54.0)
184 (3.4)
b
dec. at 250
136 (7.8)
172 (6.8)
c
75 (48.8)
Fig. 4 Crystal structure of compound 3a showing the supramolecular
interactions between the imidazolium cations and the NTf anions.
ꢀ
ꢀ
ꢀ
Compound T/ C (Cr1 / Cr2) T/ C (Cr2 / LC) T/ C (LC / I)
ꢁ
1
ꢁ1
ꢁ1
2
on cooling (DH/J g
)
(DH/J g
)
(DH/J g
)
2
2
3a
3b
a
b
110 (ꢁ27.2)
151 (ꢁ43.6)
130 (ꢁ56.3)
46 (ꢁ28)
183 (ꢁ3.3)
dec. at 250
133 (ꢁ7.2)
169 (ꢁ4.9)
104 (ꢁ30.9)
hydrogen bond between a proton of the central phenyl ring and
ꢁ
an oxygen atom of the counterion (2.47 A). This implies that
—
—
56 (ꢁ46.2)
every imidazolium moiety of the cationic core is surrounded by
two anions and each anion is surrounded by 2 imidazolium rings.
Furthermore, the distance between 2 anions surrounding the
a
Abbreviations: Cr1 and Cr2 ¼ crystalline phases, LC ¼ liquid crystal
b
ꢁ1
phase, and I¼ isotropic phase. DH ¼ 83.9 J g was determined on
heating for Cr1 / Cr2 / LC. The DH could not be determined for
Cr1 / Cr2 as well as for Cr2 / LC due to the proximity of the
ꢁ
same imidazolium moiety is measured to be 11.4 A. The higher
c
transition temperatures. For compound 3a, a minor phase transition
ꢀ
ꢁ1
2
D organization of 3a compared to 2a is also reflected in the
was observed (DH ¼ 2.5 J g ) at 105 C, between two smectic phases.
mesogenic properties of these compounds.
1
0916 | Soft Matter, 2012, 8, 10914–10920
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can estimate that these TfO salts are organized in a monolayered
SmC phase as shown in Fig. 7, with partial intercalation of the
alkyl chains. The trans conformation of the diimidazolium salt
also gives the liquid crystalline structure an inherent tilt angle.
No secondary reflection is observed by PXRD, which implies
that the counterions do not contribute to an organization in a
second dimension, which is consistent with what was observed in
the crystal structure of compound 2a.
Compounds 3a and 3b present different mesomorphic prop-
erties compared to 2a and 2b. The structure of the mesophases
was investigated by XRD and POM (Fig. 8). The mesophase had
a wider temperature range, with smectic transitions starting as
ꢀ
low as 46 C for 3a. These two NTf salts can thus be described as
2
ionic liquid crystals. A first sharp reflection with high intensity is
observed followed by three more equidistant reflections of low
intensity in the small angle region for 3a. For compound 3b, the
first high intensity sharp reflection is followed by two equidistant
reflections of low intensity. As previously seen for compounds 2a
and 2b, the supramolecular forces involved in the formation of
the smectic layers are predominantly hydrophobic interactions,
but in this case there is at least another important interaction.
This interaction can be either aromatic interactions or interac-
tions between the acidic H2 proton of the imidazolium group and
the anions. Since no aromatic interaction was observed in the
crystal structure of 3a, but significant H-bonds and electrostatic
interactions were occurring between the imidazolium moieties
Chart 1 Phase transition temperatures of compounds 2a and 2b and
upon cooling from the isotropic melt. Cr1 and Cr2: crystalline phases;
SmC: smectic C mesophase; SmT: smectic T mesophase; I: isotropic
phase; Dec: decomposition.
ꢀ
Fig. 5 (a) Left: XRD pattern of 2a at 175 C; right: ꢂ200 POM view of
ꢀ
2
a at 175 C exhibiting a fan-shaped texture of a SmC phase. (b) Left:
ꢀ
ꢀ
XRD pattern of 2b at 170 C; right: ꢂ200 POM view of 2b at 170
C
Fig. 7 Schematic representation of the organization of 2a in the SmC
exhibiting a focal conic fan texture of a SmC phase.
mesophase.
Fig. 6 Different textures observed by POM for compound 2b in the
ꢀ
same sample at 170 C. Left: ꢂ200 view of a closely packed SmC phase.
Right: ꢂ100 view showing the 2D organization at long range.
to liquid-like lateral correlations of the aromatic cores within the
ꢁ
layers is seen. The d-spacing values obtained were d ¼ 26.8 A for
ꢁ
2
a and d ¼ 31.3 A for 2b. In both cases, the d-spacing is shorter
than the length of a single molecule (d/L ¼ 0.72 for 2a and d/L ¼
.67 for 2b), resulting in tilting which confirms the character-
0
ꢀ
Fig. 8 (a) Left: XRD pattern of 3a at 120 C; right: ꢂ100 POM view of
ization of this mesophase as a SmC and an interdigitation of the
alkyl chains within the mesophase. With these d-spacing values
and the crystal structure of compound 2a described above, we
ꢀ
3
a at 175 C exhibiting a lancet-like texture of a SmT phase. (b) Left:
XRD pattern of 3b at 120 ꢀC; right: ꢂ100 POM view of 3b at 120 ꢀ
C
exhibiting a lancet-like texture of a SmT phase.
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and the counterions, it is probable that interactions of the same
nature occur in the mesophase. The anions can serve as bridges
between the diimidazolium units and allow more cohesion in the
structure, as shown in Fig. 9.
present a higher conductivity than the NTf salts, although very
2
little difference in conductivity is observed compared to typical
19
imidazolium-based ionic liquids made with these anions. For a
given anion, a 1.5 to 1.7-fold increase in conductivity is obtained
between the C12 and C16 sidechains which could indicate a less
compact structure of the alkyl chain phase, allowing a faster ion
transport across the phase. The highest ionic conductivity ach-
ieved was obtained in the SmC phase for 2b. This conductivity is
probably due to the diffusion of the anions inside the alkyl layers.
2
When the temperature of the NTf salts was raised above the
smectic–isotropic transition, a strong increase in conductivity
was observed as the ions gain freedom of movement in all
directions. As reported for other imidazolium-based ILC, the
ionic conductivities depend on the nature of the anion, but they
present higher ionic conductivities than other imidazolium-based
1
9
Fig. 9 Schematic representation of the organization of 3a in the SmT
ILCs previously reported. The ionic conductivity in the Sm
mesophase.
phase is 10 times lower than that in the best imidazolium-based
9
c
ionogels recently described. However their anisotropy and
temperature controllable conductivities may open the door to the
development of their application for photovoltaic fuel cells when
doped with a lithium salt, or as matrix in the electrosynthesis of
diverse materials.
For both compounds 3a and 3b, a slow growing lancet-like
texture was observed upon cooling from the isotropic melt. This
texture closely resembles that of growing crystals but both
compounds can be described as viscous liquids after the first
ꢀ
phase transition around 50 C, which is a very common property
of imidazolium ionic liquids in this temperature range. The same
Conclusions
lancet-like texture has been reported also for Smectic T (SmT)
1
8
ꢀ
mesophases. The peaks at around 2q ¼ 17 are slightly sharper
than those of more commonly seen smectic A and C phases,
which indicates that the alkyl sidechains are less amorphous and
give to this SmT mesophase a soft crystalline nature. Further-
more, for compound 3a, a transition between two different SmT
We have investigated the mesomorphic properties of a new
family of diimidazolium salts by varying the counterions and the
length of the alkyl chains. The counterion has a great impact on
the mesomorphism and the temperature of the phase transitions.
Only SmC phases could be identified with the TfO counterion
with a much larger range of liquid crystal phase for the longer
ꢀ
phases was observed by DSC at 105 C, with a DH of about 2.5 J
g
ꢁ1
. No change in the PXRD was observed, as the d-spacings
C16 alkyl sidechains. When symmetrical NTf counterions were
2
remain the same, as well as the shape of the diffraction pattern.
Only a slight difference is observed by POM between these two
phases when cooling from the isotropic melt. As a result, we
believe that we can correlate this to a minor reorganization of the
used, the first phase transition into a liquid crystalline phase
ꢀ
ꢀ
occurs at around 50 C, 120 C lower than that of the TfO
compounds. The ionic liquid crystalline phases obtained have
been classified into SmT phases. The thermotropic meso-
morphism of these ionic liquid crystals opens the possibility of
using them as ordered solvents or organized reaction media. In
these anisotropic solvents other chemo- and regioselectivities
besides those in conventional solvents can be obtained for several
types of reactions. The use of this type of ILCs for charge
transport may find application in the fabrication of new elec-
ꢀ
SmT mesophase at 105 C, but no further evidence of this
reorganization was obtained. This phase transition was not
observed for compound 3b which has longer side-chains.
Ionic conductivity
As the liquid crystalline network formed by these salts can be
trochemical
materials
with
temperature-controlled
19
seen as an anisotropically functional organization, the rela-
tionship between the mesomorphic behaviour and ionic
conductivity was studied for compounds 2a, 2b, 3a and 3b
conductivities.
Experimental section
(
Table 2). For the same alkyl chain, a small conductivity decrease
is noted with the increase of the anion size, as the TfO salts
All commercially available chemicals were used without further
purification. Nuclear Magnetic Resonance (NMR) experiments
were done either on a Br u€ ker Avance AV400 operating at 400
Table 2 Ionic conductivities in the smectic and isotropic phases
1
13
MHz for H NMR experiments and at 100 MHz for C NMR
Conductivity in
ꢀ
Conductivity in
ꢀ
experiments or on a Br u€ ker Avance AV300 operating at 75 MHz
13
for C NMR experiments. Electrospray Ionisation (ESI) mass
Sm phase ( C)
I phase ( C)
(ꢂ 10 S cm
ꢁ3
ꢁ1
ꢁ3
ꢁ1
Compounds
(ꢂ 10 S cm
)
)
spectra were recorded with a TSQ Quantum Ultra (Thermo
Scientific) Mass Spectrometer with accurate mass options
instrument (Universit ꢀe de Montr ꢀe al Mass Spectrometry
Facility). Differential scanning calorimetry (DSC) analyses were
carried out on a Q2000 TA instruments. X-ray diffraction
ꢀ
a
2
2
3
3
a
b
a
b
0.38 (175 C)
0.67 (175 C)
n.d.
n.d.
ꢀ
a
ꢀ
ꢀ
ꢀ
0.28 (130 C)
0.43 (130 C)
6.2 (175 C)
8.2 (175 C)
ꢀ
a
ꢀ
The temperature limit of our system was 175 C.
(
XRD) studies were carried out on a Br u€ ker D8 Discover,
1
0918 | Soft Matter, 2012, 8, 10914–10920
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equipped with a Hi-Star detector. XRD data were collected using
GADDS 4.1.1.4 software and EVA 8.0.0.2 was used for data
analysis. A custom made XYZ stage with a temperature control
(ppm) 133.8, 124.8, 124.3, 122.3, 118.5, 51.0, 32.5, 30.4, 30.2
(multiple peaks), 30.1, 30.0, 29.9, 29.8, 29.5, 26.7, 23.1, 13.8. HR-
2
+
MS m/z found: 330.3043 ([M ꢁ 2NTf ] ), calc.: 330.3029. Elem.
2
chamber and a Cu source (K
a
energy of 8.04 keV and l ¼
analysis: found: 6.71% N, 46.38% C, 6.28% H, 10.06% S; calc.:
6.88% N, 47.15% C, 6.22% H, 10.47% S, yield 67%.
ꢁ
.541838 A) were used. Polarizing optical microscopy (POM)
1
was carried out with a Zeiss Axioskop 40Pol microscope coupled
with a Linkam Scientific Instrument THMS600 hot stage and a
TMS94 temperature controller.
Ionic conductivity
1
-[4-(1H-Imidazol-1-yl)phenyl]-1H-imidazole was synthesized
13
Ionic conductivities were measured with a two-probe setup using
a cell made in house. This cell consisted of two 0.25 mm Pt wires
(Alfa Aesar 99.9%) protruding from a glass tube and separated
from each other by ca. 2 mm. Electrochemical impedance spectra
2
0
1
following a previously reported procedure. The H and
C
NMR spectra of this compound were found to be in accordance
with the literature.
(
PARSTAT 2273) were recorded for the samples heated at
ꢁ3
5
various temperatures (oil bath) from 10 to 10 Hz at open
circuit potential. The cell resistance was determined from the
intercept of the curve on the real impedance axis of the Nyquist
plots at high frequencies. The cell was thereby calibrated with a
General procedure for the synthesis of dialkyl(1,4-phenylene)
diimidazolium salts
To a solution of 1-[4-(1H-imidazol-1-yl)phenyl]-1H-imidazole
ꢁ
1
(
1 mmol, 210 mg, 1 eq.) in acetonitrile (10 mL) was added the
KCl conductivity standard solution (Alfa Aesar, 15 000 mS cm )
to obtain the conductivity of the ILCs.
appropriate alkyl bromide (10 mmol, 10 eq.). The solution was
refluxed and stirred for 24 h and then filtered. The diimidazolium
bromide salts were dried under high vacuum for 24 h then
solubilised in 10 mL of methanol. Either lithium bis(tri-
fluoromethylsulfonyl)imidate or ammonium triflate (2.1 mmol,
Acknowledgements
We thank the Natural Sciences and Engineering Research
Council of Canada (NSERC), the Fonds Qu ꢀe b ꢀe cois pour la
Recherche, la Nature et les Technologies (FQRNT), the Canada
Foundation for Innovation (CFI) and Universit ꢀe de Montreal
for financial support. We thank S. Essiembre for the help in the
use of the powder X-ray diffractometer, P. M ꢀe nard-Tremblay for
his help on POM and M. Simard for XRD diffraction. We would
also like to thank Professor G. Bazuin for her help with identi-
fication of the liquid crystalline phases.
2
.1 eq.) was added and the solution was refluxed for 2 h. After
evaporation of the solvent, water was added and the subsequent
salts were filtered and dried under high vacuum.
0 0
,1 -Didodecyl-3,3 -(1,4-phenylene)diimidazolium bis(triflate)
1
1
2a): H NMR (CD
(
3
OD, 400 MHz): d (ppm) 8.21 (s, 2H), 8.07
(
s, 4H), 7.95 (s, 2H), 4.37 (t, J ¼ 7.4 Hz, 4H), 2.08 (sext, J ¼ 6.1
1
3
Hz, 4H), 1.27–1.53 (m, 36H), 0.91 (t, J ¼ 6.06 Hz, 6H). C NMR
CD OD, 100 MHz): d (ppm) 135.6, 123.5, 123.0, 121.1, 49.8,
(
3
3
1.3, 29.2, 29.0, 28.9, 28.7, 28.6, 28.3, 25.6, 21.9, 12.6. HR-MS m/
2
+
z found: 274.2412 ([Mꢁ2TfO] ), calc.: 274.2403. Elem. analysis:
Notes and references
found: 6.52% N, 54.20% C, 7.40% H, 7.32% S; calc.: 6.61% N,
1
(a) P. Wasserscheid and T. Welton, Ionic Liquids in Synthesis, Wiley-
VCH, Weinheim, 2003; (b) J. Dupont, R. F. de Soula and
P. A. Suarez, Chem. Rev., 2002, 102, 3667.
5
3.83% C, 7.08% H, 7.56% S, yield 88%.
0
0
1
,1 -Dihexadecyl-3,3 -(1,4-phenylene)diimidazolium
bis(tri-
1
flate) (2b): H NMR (CD
3
OD, 400 MHz): d (ppm) 8.21 (s, 2H),
2 H. Ohno, Electrochemical Aspect of Ionic Liquids, Wiley-Interscience,
2005.
3 V. Gauchot, W. Kroutil and A. R. Schmitzer, Chem.–Eur. J., 2010,
8
1
1
2
.07 (s, 4H), 7.95 (s, 2H), 4.37 (t, J ¼ 7.4 Hz, 4H), 2.03 (m, 4H),
13
.25–1.51 (m, 52H) 0.92 (t, J ¼ 6.6 Hz, 6H). C NMR (CD
3
OD,
1
6, 6748.
00 MHz): d (ppm) 135.6, 123.5, 123.0, 121.1, 49.8, 31.3, 29.2,
4
L. Leclercq, M. Lacour, S. H. Sanon and A. R. Schmitzer, Chem.–
Eur. J., 2009, 15, 6327.
9.0, 28.9, 28.7 (multiple peaks), 28.6, 28.3, 25.6, 21.9, 12.6. HR-
2
+
5 (a) H. Ohno, M. Yoshizawa and W. Ogihara, Electrochim. Acta, 2004,
0, 255; (b) H. Ohno, Electrochim. Acta, 2001, 46, 1407; (c) A. Noda
and M. Watanabe, Electrochim. Acta, 2000, 45, 1265; (d)
M. Watanabe and T. Mizumura, Solid State Ionics, 1996, 86ꢁ88, 353.
6 (a) A. Lewandowski and A. Swiderska, Solid State Ionics, 2004, 169,
21; (b) J. Fuller, A. C. Breda and R. T. Carlin, J. Electroanal. Chem.,
MS m/z found: 330.3045 ([M ꢁ 2TfO] ), calc.: 330.3029. Elem.
5
analysis: found: 5.85% N, 57.40% C, 7.99% H, 5.95% S; calc.:
5
.84% N, 57.54% C, 7.92% H, 6.67% S, yield 71%.
0 0
1
,1 -Didodecyl-3,3 -(1,4-phenylene)diimidazolium bis[bis(tri-
1
3
fluoromethane-sulfonyl)imide] (3a): H NMR (CD OD, 400
1
998, 459, 29.
MHz): d (ppm) 8.18 (d, J ¼ 1.4 Hz, 2H), 8.05 (s, 4H), 7.93 (d, J ¼
7
8
9
J. Sun, D. R. MacFarlane and M. Forsyth, Solid State Ionics, 2002,
147, 333.
J. Fuller, A. C. Breda and R. T. Carlin, J. Electrochem. Soc., 1997,
1
3
.4 Hz, 2H), 4.36 (t, J ¼ 7.4 Hz, 4H), 2.03 (m, 4H), 1.27–1.50 (m,
13
6H), 0.91 (t, J ¼ 6.79 Hz, 6H). C NMR (CD
3
OD, 100 MHz): d
1
44, L67.
(a) J. Le Bideau, L. Viau and A. Vioux, Chem. Soc. Rev., 2012, 2, 907;
b) J. Casamada Ribot, C. Guerrero-Sanchez, T. L. Greaves,
D. F. Kennedy, R. Hoogenboom and U. S. Schubert, Soft Matter,
012, 8, 1025; (c) J. Casamada Ribot, C. Guerrero-Sanchez,
R. Hoogenboom and U. S. Schubert, J. Mater. Chem., 2010, 20, 8279.
(
ppm) 135.6, 123.6, 123.1, 121.1, 49.8, 31.3, 29.2, 29.0, 28.8, 28.7,
2
2
4
8.6, 28.3, 25.5, 21.9, 12.6. HR-MS m/z found: 274.2411 ([M ꢁ
(
2+
NTf
2
] ), calc.: 274.2403. Elem. analysis: found: 7.52% N,
2
3.49% C, 5.62% H, 11.67% S; calc.: 7.57% N, 43.27% C, 5.41%
H, 11.53% S, yield 83%.
0 0
1
0 (a) K. M. Lee, Y. T. Lee and J. B. Lin, J. Mater. Chem., 2003, 13,
1079; (b) J. De Roche, C. M. Gordon, C. T. Imrie, M. D. Ingram,
A. R. Ingram, A. R. Kenedy, F. LoCelso and A. Triolo, Chem.
Mater., 2003, 15, 2003; (c) S. Kumar and S. Kumar Pal,
Tetrahedron Lett., 2005, 46, 2607; (d) J. Motoyagani, T. Fukushima
and T. Aida, Chem. Commun., 2005, 101; (e) J. M. Suisse,
S. Bellemin-Laponnaz, L. Douce, A. Maisse-Fran c¸ ois and
1
,1 -Dihexadecyl-3,3 -(1,4-phenylene)diimidazolium bis[bis-
1
(
trifluoromethane-sulfonyl)imide] (3b): H NMR (CD OD, 400
3
MHz): d (ppm) 8.19 (d, J ¼ 1.4 Hz, 2H), 8.06 (s, 4H), 7.94 (d, J ¼
1
5
.4 Hz, 2H), 4.36 (t, J ¼ 7.3 Hz, 4H), 2.03 (m, 4H), 1.25–1.51 (m,
13
2H) 0.92 (t, J ¼ 6.6 Hz, 6H). C NMR (CD
3
OD, 75 MHz): d
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View Article Online
R. Welter, Tetrahedron Lett., 2005, 46, 4303; (f) K. Binnemans, Chem.
Rev., 2005, 105, 4148.
16 N. Noujeim, B. Jouvelet and A. R. Schmitzer, J. Phys. Chem. B, 2009,
113, 16159.
11 W. Dobbs, L. Douce, L. Allouche, A. Louati, F. Malbosc and
R. Welter, New J. Chem., 2006, 30, 528.
12 (a) C. K. Lee, H. W. Huang and I. J. B. Lin, Chem. Commun., 2000,
17 (a) L. Leclercq, N. Noujeim and A. R. Schmitzer, Cryst. Growth Des.,
2009, 9, 4784; (b) L. Leclercq, M. Simard and A. R. Schmitzer, J. Mol.
Struct., 2009, 918, 101.
1
8
2
911; (b) M. Tosoni, S. Laschat and A. Baro, Helv. Chim. Acta, 2004,
7, 2742; (c) Y. R. Zhao, X. Chen and X. D. Wang, J. Phys. Chem. B,
009, 113, 2024; (d) M. Yoshio, T. Mukai, K. Kanie, M. Yoshizawa,
18 (a) E. Alami, H. Levy, R. Zana, P. Weber and A. Scoulios, Liq. Cryst.,
1993, 201–212; (b) K. Goossens, K. Lava, P. Nockemann, K. Van
Hecke, L. Van Meervelt, K. Driesen, C. Garller-Walrand,
K. Binnemans and T. Cardinaels, Chem.–Eur. J., 2009, 15,
656.
19 (a) J. Pitawala, A. Matic, A. Martinelli, P. Jacobsson, V. Koch and
F. Croce, J. Phys. Chem. B, 2009, 113, 10607; (b) H. Tokuda,
K. Ishii, A. B. H. Susan, S. Tsuzuki, K. Hayamizu and
M. Watanabe, J. Phys. Chem. B, 2006, 110, 2833; (c) M. Yoshio,
T. Ichikawa, H. Shimura, T. Kagata, A. Hamasaki, T. Mukai and
T. Kato, Bull. Chem. Soc. Jpn., 2007, 9, 1836.
H. Ohno and T. Kato, Chem. Lett., 2002, 320.
3 X. Cheng, X. Bai, S. Jing, H. Ebert, M. Prehm and C. Tschierske,
Chem.–Eur. J., 2010, 16, 4588.
4 (a) S. Yazaki, Y. Kamikawa, M. Yoshio, A. Hamasaki, T. Mukai,
H. Ohno and T. Kato, Chem. Lett., 2008, 38, 538; (b) K. Hoshino,
M. Yoshio, T. Mukai, K. Kishimoto, H. Ohno and T. Kato, J.
Polym. Sci., Part A: Polym. Chem., 2003, 41, 3486; (c) M. Yoshio,
T. Mukai, H. Ohno and T. Kato, J. Am. Chem. Soc., 2004, 126, 994.
5 (a) Y. Sanami, M. Funahashi and T. Kato, J. Am. Chem. Soc., 2008,
1
1
1
20 H.-J. Cristau, P. P. Cellier, J.-F. Spindle and M. Taillefer, Chem. Eur.
J., 2004, 10, 5607–5622.
130, 13206; (b) L. Chui and L. Zhu, Liq. Cryst., 2005, 32, 143.
1
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