A Convenient Method For Preparing Rigid Core Ionic Liquid Crystals
A convenient method for preparing rigid-core ionic
liquid crystals
Julien Fouchet1, Laurent Douce*1, Benoît Heinrich1, Richard Welter2
and Alain Louati3
Full Research Paper
Open Access
Address:
Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
1Institut de Physique et Chimie des Matériaux de Strasbourg, UMR
doi:10.3762/bjoc.5.51
7504, DMO, CNRS-Université de Strasbourg, BP 43, 23 rue du
Loess, F-67034 Strasbourg Cedex 2, France, 2Laboratoire
Received: 22 July 2009
DECOMET, UMR CNRS 7177-LC003, Université Louis Pasteur, 4 rue
Accepted: 29 September 2009
Blaise Pascal, 67000 Strasbourg, France and 3Laboratoire
Published: 07 October 2009
d’Electrochimie Analytique, Ecole Nationale Superieure de Chimie de
Mulhouse, 3 rue Alfred Werner, 68093 Mulhouse Cedex, France
Guest Editor: S. Laschat
Email:
© 2009 Fouchet et al; licensee Beilstein-Institut.
Laurent Douce* - Laurent.Douce@ipcms.u-strasbg.fr
License and terms: see end of document.
* Corresponding author
Keywords:
imidazolium; ionic liquid crystals; Ullman reaction
Abstract
An efficient, solvent free method for the N-arylation of imidazole by 1-(dodecyloxy)-4-iodobenzene using Cu(II)-NaY as catalyst
and K2CO3 as base is reported. By this synthetic approach, mesomorphic 3-[4-(dodecyloxy)phenyl]-1-methyl-1H-imidazol-3-ium
iodide was synthesized in a two-step procedure, and its mesomorphism has been fully investigated by polarised optical microscopy,
differential scanning calorimetry and X-ray diffraction. In addition its lamellar crystal structure, electrochemical behaviour and UV
(absorption and emission) properties are reported.
Introduction
Over the past decade extensive studies of ionic liquids (ILs)
tions include those in separation and extraction processes, and
have revealed their many useful properties such as extremely
in various electrochemical devices, such as lithium ion batteries,
low volatility, high thermal stability, non-flammability, high
fuel cells, and capacitors, as well as in synthesis and catalysis
chemical and radiochemical stability, high ionic conductivity
[1-5].
and wide electrochemical window [1-3]. In addition, the ILs
have been used as reaction media increasing the yields of many
Liquid crystals are characterised by both mobility and self-
syntheses and eliminating the hazards associated conventional
organisation at the macroscopic level [6]. Almost all such meso-
solvents [4]. Thus are extremely versatile in that changes in
morphic materials are based on molecules combining two
both the cation and its counter anion can be used to finely tune
antagonistic units consisting of rigid (aromatic) and flexible
their properties (for example: viscosity, melting point, polarity,
(alkyl) or hydrophilic (polar heads) and hydrophobic (alkyl
hydrophilicity/hydrophobicity…). Important emerging applica-
chains) parts. The subtle balance of their effects governs the
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
formation of a multitude of supramolecular architectures
(<80%) and reproducible yield (Scheme 2). Swager has already
depending on the temperature (thermotropic liquid crystals)
published the synthesis of compound A under standard Ullman
and/or of the solvent (lyotropic liquid crystals) [7,8]. In the case
conditions (K2CO3, CuI, L-proline in DMSO, 16 h at 110 °C)
of the thermotropic liquid crystals the arrangements give rise to
[22].
nematic phases (molecules are aligned along an orientational
axis), smectic phases (orientational/positional order in the
layers) and columnar phases (orientational/positional order in
the columns). The lyotropic compounds display not only
lamellar and columnar organization but also hierarchical self-
assembly in spheres (micelles), ribbons and fibres. These
unique properties lead to their applications ranging from display
Scheme 2: Synthesis of the imidazole A. Reaction conditions: (i) aryl
technology through templating media for synthesis to biolo-
iodide (1.37 mmol), imidazole (1.69 mmol), K2CO3 (1.51 mmol),
Cu(II)NaY (148 mg), 72 h at 180 °C in a sealed tube.
gical activity (targeting and transporting of drugs and gene
materials) [9].
The aryl-imidazole A was purified by column chromatography
Full convergence of the ionic liquid and liquid crystal fields
(ethyl acetate as eluent) on silica and characterized spectroscop-
could provide a vast range of materials (Ionic liquid crystals,
ically. The second step involved alkylation of A by iodo-
ILCs) with novel and tunable characteristics such as those of
methane to give salt 1a in 89% yield after purification
ordered and oriented hybrid compound semiconductors exhib-
(Scheme 3). Distinctive signals for the CH (1H-imidazolium)
iting both electronic and ionic conductivity [10]. For this, the
group appear in the 1H and 13C NMR spectra at 10.45 ppm and
imidazolium unit is an excellent platform that can be designed
134.97 ppm respectively.
to promote liquid crystalline phases and easily be doped by a
large diversity of anions [11-21]. Variation of the
N-substituents by Ullman coupling to extend the aromatic part
is a facile means of creating this range [22,23].
Herein, we wish to report a solvent-free, N-arylation of
imidazole as a means of expanding the aromatic core and
Scheme 3: Synthesis of methyl imidazolium 1a. Reaction conditions:
(i) MeI in sealed tube, 54 h at RT.
obtaining unsymmetrical imidazolium liquid crystals
(Scheme 1). We also describe the influence of the counter anion
on the mesomorphism, electrochemistry and the UV properties
Single crystals of 1a suitable for X-ray diffraction were
of these imidazolium salts.
obtained by slow diffusion of ether into a CH2Cl2 solution. The
compound 1a crystallizes in the triclinic space group P1.
A partly labelled ORTEP view showing non-classical hydrogen
bonds and C-H..π interactions is given in Figure 1 (the interac-
tions also being listed in Table 1). The alkyloxy chains are quite
parallel, as is clear from the crystal packing given in Figure 2,
with segregation between the rigid part (including iodine atoms)
and the alkyloxy chains (≈20 Å, see Figure 2). The length of the
molecule in the crystalline state is about 24 Å.
Scheme 1: 1-[4-(dodecyloxy)phenyl]-3-methyl-1H-imidazol-3-ium
mesogenic salts.
It should be emphasised that the lattice area (A = a·b·sin(γ) =
2V/d001 = 57.1 Å2) is about three times the transverse area of an
Results and Discussion
all-trans crystallised chain and that even so the alkyl tails
Synthesis and characterization
organise in segregated double layers, without interdigitation but
Compound 1a was obtained in a two-step procedure. The first
with a tilt angle of 71° with respect to the layer normal. This
step was a coupling reaction between 1-(dodecyloxy)-4-
large tilt angle just compensates the discrepancy between areas,
iodobenzene and imidazole using Cu(II)-NaY as catalyst in the
maintaining the compactness of the packing and the flatness of
presence of potassium carbonate as base [23]. The reaction took
the segregated ionic and aliphatic double layers. Apart from the
place without solvent at 180 °C in a sealed tube over 72 h to
crystallised state of the tails, this structure is very close to a
afford 1-[4-(dodecyloxy)phenyl]-1H-imidazole (A) in a good
smectic type of organisation. The segregation between the alkyl
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
Figure 1: ORTEP view of compound 1a with partial labelling. The closest molecules are represented (with lower opacity) when connected by CH-π
and/or non classical H-bonds (black thin lines). The ellipsoids enclose 50% of the electronic density. Symmetry operators for equivalent positions:
d = ±1+x, y, z; e = 1+x, 1+y, z.
Table 1: Non-classical hydrogen bonds and CH..π interactionsa occurring in 1a. Cg is the phenyl ring (C5 to C10). Symmetry operators for equivalent
positions: d = ±1+x, y, z; e = 1+x, 1+y, z.
C-H..I
dC-H (Å)
dH-I (Å)
dC-I (Å)
C-H-I (°)
C1-H1..Id
0.95
2.8270
3.746(5)
163.1
C2-H2..Ie
0.95
2.9123
3.822(5)
160.6
C11-H11B..I
0.95
3.0026
3.992(5)
179.2
C-H..Cg
dC-H (Å)
dH-Cg (Å)
dC-I (Å)
C-H-Cg (°)
C4-H4A..Cgd
0.95
3.109
3.502
105.6
C4-H4B..Cgd
0.95
3.309
3.502
93.1
C17-H17B..Cge
0.95
3.310
4.207
151.5
aPlaton software [24].
tails and the charged rigid parts indicates that by melting the
dependent upon the anion, with δ 10.45 (1a) 9.37 (1b), 9.10
chains they could show liquid crystal behaviour at a higher
(1c), 9.41 (1d) and 8.98 ppm (1e). This dependency is certainly
temperature. In order to understand the influence of the anion
due to the interactions though H-bonding and the charge local-
on the electrochemical, UV properties and mesomorphism, we
isation on the anion. The UV spectra displays typical charge
prepared compounds with BF4− (1b), PF6− (1c), CF3SO3− (1d)
transfer (π–π* or n–n*) transitions in CH2Cl2 at 240 nm (1a ε =
and (CF3SO2)2N− (1e) anions in excellent yield by anion meta-
24000 M−1 cm−1), 255 nm (1b ε = 10500 M−1 cm−1), 249 nm
thesis in water/CH2Cl2 as solvent (Scheme 4).
(1c ε = 11700 M−1 cm−1), 256 nm (1d ε = 10100 M−1 cm−1)
and 255 nm (1e ε = 11100 M−1 cm−1). A blue emission was
All these compounds were fully characterized by 1H NMR,
also observed at 384 nm (Figure 3).
13C NMR {1H}, FT-IR and UV spectroscopy, as well as
elemental analysis. The IR spectra showed typical anion vibra-
Investigation of the Liquid Crystalline Beha-
tions at 1024 cm−1 (1b BF4−), 826 cm−1 (1c PF6−), 1269 and
viour
1028 cm−1 (1d CF3SO3−), 1358 and 1183 cm−1 (1e
The thermogravimetric analysis of compounds 1a–e showed the
(CF3SO2)2N−). 1H NMR spectra were recorded in CDCl3, in
general stability order to be I−< BF4− ≈ PF6−< CF3SO3−<
which the chemical shift for the CH (1H-imidazolium) is very
(CF3SO2)2N− (Figure 4).
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
Figure 2: Packing diagram of compound 1a in projection in the (b,c) lattice plane. Large spheres represent the iodine atoms.
Scheme 4: Anion metathesis in water/CH2Cl2 as solvent.
Figure 3: Spectra of absorption (red line) and emission (blue line)
Figure 4: TGA measurements of the compounds 1a–e (rate
of 1a.
10 °C·min−1, in air).
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Table 2: Phase transition temperatures and corresponding enthalpies determined from the 2nd heating and cooling.
Temperature
Temperature
Anions
Phase
Phase
Phase
Cr
LC
LC
I
113 °C (15.83 kJ/mol)
I−
Crystal
Smectic A
250 °C
Decomposition
81 °C (12.76 kJ/mol)
91 °C (30.08 kJ/mol)
BF4−
Crystal
Smectic A
230 °C
Decomposition
60 °C (10.62 kJ/mol)
97 °C (36.21 kJ/mol)
163 °C (1.12 kJ/mol)
PF6−
Crystal
Smectic A
Liquid
68 °C (43.34 kJ/mol)
163 °C (1.76 kJ/mol)
77 °C (43.28 kJ/mol)
95 °C (0.79 kJ/mol)
F3CO3−
Crystal
Smectic A
Liquid
49 °C (44.00 kJ/mol)
95 °C (1.04 kJ/mol)
59 °C (61.17 kJ/mol)
(F3CSO2)2N−
Crystal
Liquid
39 °C (61.12 kJ/mol)
Legend: Cr: Crystal, LC: Liquid Crystal, I: Isotropic Liquid.
For all the compounds, the mesomorphic behaviour and phase
The optical textures observed during slow cooling from
transition temperatures were investigated by polarized optical
isotropic melt showed the emergence of a smectic A phase
microscopy (POM), differential scanning calorimetry (DSC),
(appearance of Batônnet rods, turning into a wide, fan-like,
and powder X-ray diffractometry (XRD). To avoid possible
focal-conic texture). The smectic structure of the liquid crystal
effects of hydration of the materials, all were dried in vacuo
phase was confirmed by XRD. The X-ray pattern (Figure 6) of
before X-ray and DSC analyses. The phase transition tempera-
the Smectic A form recorded at 120 °C contains a diffuse band
tures and the corresponding enthalpy changes derived for
at 4.6 Å (wide angle), which shows clearly that the alkyl chains
compounds 1a–e are compiled in Table 2, while typical results
have a liquid-like structure and are segregated from the
are displayed in Figure 5.
aromatic cores.
The high stability of the compounds was also demonstrated by
The layer thickness in the Smectic A phase was determined
the absence of significant perturbation of the DSC patterns
from the position of the sharp reflection in the small angle
following several heating–cooling cycles. Compounds 1e, not
region (d = 39.8 Å at 120 °C) and corresponds to the alterna-
unexpectedly, do not show thermotropic behaviour, while the
tion between the sublayer formed by the molten chains and the
data for 1a–d give an order of anion stabilisation of liquid
sublayer formed by the ionic double layer and the mesogenic
crystal behaviour of Br− > BF4− > PF6− > CF3SO3− (see
Figure 5).
Figure 6: Powder X-ray diffraction pattern of compound 1a in the liquid
Figure 5: Phase transition temperatures of compounds 1a–e.
crystal state (T = 120 °C).
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
parts. The thickness of the corresponding sublayers’ alternation
o f r u f f l i n g ( t h e s m a l l d i s c r e p a n c i e s f o r c o m p o u n d
in the crystalline phase is given by the location of the
1d (CF3SO3−) being explained by the presence of the CF3
d001 reflection (d001 = 20.21 Å from single crystal pattern at
lateral group, which contributes to dc and perturbates slightly
room temperature). Despite the enormous difference in layer
the interface with the aliphatic sublayer). It should be empha-
thicknesses between both phases (the extrapolation of the vari-
sised that the stability of the smectic A phase is not determined
ation versus temperature gives d = 46.5 Å at 20 °C i.e. more
by the degree of ruffling of the ionic sublayer but by the folding
than twice d001), the difference in molecular volume (smectic
degree of the tails and therefore the thickness of the aliphatic
phase: Vmol = 622 Å3 at 20 °C; crystalline phase: Vmol = V/2 =
sublayers. Thus, depending upon the anion size, the isotropisa-
577 Å3) just coincides with the contribution of the chain
tion occurs at various temperatures, but for approximately the
melting [25,26], indicating that the partial volume of the ionic
same maximum molecular area (Smax ≈ 41 Å2) and therefore
sublayer does not change significantly between both phases.
similar minimum aliphatic sublayer thicknesses (dchmin ≈ 19 Å).
The observed layer thickness change is therefore the
consequence of the different “molecular areas” S, i.e. the
projection area of a mesogen counter-ion assembly within the
mean smectic plane (S = 2Vmol/d), which is identical to the
lattice area in the crystalline phase (S = V/d001). Thus, since no
significant volume change is involved in the shrinking of S
from 57.1 Å2 in the crystalline phase to 27 Å2 in the smectic A
phase (value at 20 °C obtained from the extrapolation of the
variation of S versus temperature), the ionic sublayer thickness
dc (determined as dc = 2[Vmol/−Vch]/S, Vch being the chain
volume) simultaneously expands in proportion (from 9.5 Å in
the crystalline phase to 20 Å in the smectic phase at 20 °C).
These lateral shrinkage and longitudinal extension events are
the result of a ruffling process of the ionic sublayers, starting
from the completely flat state in the crystalline phase shown by
the single crystal structure (see Figure 7).
The maximum degree of ruffling in the smectic A phase is
reached just before crystallisation, since the experimental
temperature dependence of S and dc indicates that the sublayers
continuously spread with increasing temperature (see Figure 8).
The counter-ion substitution within the series 1 involves large
changes of S, but the temperature dependence and dc values are
roughly the same for all terms (see Figure 9).
Figure 8: Comparison of the molecular area S and of the ionic
The influence of the substitution can therefore be considered as
sublayer thickness dc (including mesogenic segments) in the crystal-
an anion size effect, since the lattice area expands with
line phase (circle) and in the smectic A phase (squares) for
compound 1a (I−).
increasing counter-ion bulkiness without change of the degree
Figure 7: The melting process involves the ruffling of the ionic sublayer. In the smectic phase, the ruffling degree decreases with
increasing temperature.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
packing is reached. In the smectic phase, tail tilting is not
favourable upon the amphipathic expelling at the interface with
the ionic sublayer and the system adopts a compromise
molecular area associating ruffled ionic sublayers and folded
aliphatic tails. With increasing temperature, the aliphatic chains
spread more easily and the organisation shifts toward flat
sublayers. A more detailed investigation of the molecular area
variation in series involving both, counter-ion substitution and
tail-length variation, has been presented elsewhere for a very
similar cationic structure [20,25,26].
Electrochemical behaviour
Cyclic voltammetry was used to determine the electrochemical
behaviour of the compounds 1a, 1b and 1c, the voltammo-
grams being recorded in CH3CN solutions containing 0.1 M
NBu4PF6 as supporting electrolyte at a platinum working elec-
trode. The peak potentials are given vs. a SCE. Representative
cyclic voltammograms of 1a are shown in Figure 10. The
anodic portion of the voltage scan displays two oxidation steps
having peak potentials of 0.42 V and 0.68 V, and likely involve
the formation of I2 and possibly then a higher-oxidation-state
iodine (I3−) species. As seen for 1a (Figure 9), for 1b and 1c the
cathodic portion of the voltage scan displays only an irrevers-
ible reduction step at ca 1.58 V, which corresponds to the
Figure 9: Variation with the counter-ion of the molecular area S and of
the ionic sublayer thickness d
reduction of the cationic imidazolium species. Note that the
c (including mesogenic segments) in the
smectic A phase for series 1: squares: 1a (I−); circles: 1b (BF4−); up
peak at −0.8 V is probably due to the reduction of O2 which is
triangles: 1c (PF6−); down triangles: 1d (CF3SO3−).
difficult to eliminate from the solution.
To summarise, the large discrepancy between the lattice area
Conclusion
and the cross section of the aliphatic chains are taken into
In conclusion, we report synthetic methodology based on
account differently in the crystalline and in the smectic
Ullman coupling to extend the imidazolium aromatic core.
molecular organisations. In the crystalline phase, the ionic
From this coupling product we have synthesized and fully char-
sublayers just impose their area and the tails tilt until dense
acterized new mesomorphic compounds with different anions.
Figure 10: Cyclic voltammogram of 1a in CH3CN (0.1 M NBu4PF6): (i), (ii) cathodic and anodic range of the voltage scan. Scan rate 100 mV·s−1. The
black star denotes the initial and final potential.
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
We have also determined a structure by X-ray diffraction on a
measured by differential scanning calorimetry with a DSC
single crystal. The crystallisation shows the completely lamellar
Q1000 from TA Instruments at different temperature rates
segregation between the flexible chains and the rigid part. The
(5 °C·min−1, 2 °C·min−1) on heating and cooling.
layers are linked to each other by the semi-interdigitation of
alkyl tails. Despite an enormous difference between the cross-
1-[4-(Dodecyloxy)phenyl]-1H-imidazole (A)
section of crystallised chains and the lattice area imposed by the
1-Dodecyloxy-4-iodobenzene (0.533 g, 1.37 mmol), imidazole
organisation within the ionic sublayers, the latter just remain
(0.115 g, 1.69 mmol), K2CO3 (0.288 g, 1.51 mmol) and
flat and the tails undergo a double layer dense packing with 71°
Cu(II)-NaY (0.148 g) were heated in sealed tube to 180 °C for
tilting with respect to the layer normal. In the smectic phase,
72 h. The reaction mixture was filtered to remove the catalyst
area matching is achieved by ruffling of the sublayers and
and the filtrate was purified by column chromatography (silica
folding of the molten aliphatic tails, the degree of ruffling
gel, ethyl acetate) to afford pure A (0.378 g, 84%).
decreasing with increasing temperature. The electrochemical
windows have been measured and we are attempting to measure
1H NMR (300 MHz, CDCl3): δ = 0.88 (t, 3H, J = 6.5 Hz, CH3
the carrier mobility in order to fully assess the prospects for
aliphatic chain), 1.27 (broad s, 16H, CH2 aliphatic chain),
using these molecules in molecular electronics. We intend also
1.42–1.49 (m, 2H, O-CH2-CH2-CH2), 1.75–1.84 (m, 2H,
to introduce different length tails in order to obtain room
O-CH2-CH2), 3.98 (t, 2H, J = 6.6 Hz, O-CH2), 6.96 and 7.27
temperature ionic liquid crystals, aswell as to explore use of the
(AA′ and BB′, 2 × 2H, J = 9.0 Hz, CH phenyl), 7.17–7.19 (m,
coupling reaction between imidazole and other aromatics and
2H, N-CH-CH-N), 7.75 (broad s, 1H, N-CH-N). 13C NMR (75
heterocycles to tune the electronic properties.
MHz, CDCl3): δ = 14.03 (CH3 aliphatic), 22.61, 25.94, 29.13,
29.27, 29.30, 29.50, 29.52, 29.57, 29.59, 31.84 (CH2 aliphatic),
Experimental
6 8 . 4 0 ( O - C H 2 ) , 1 1 5 . 3 9 ( C H p h e n y l ) , 1 1 8 . 6 7 ( C H
X-ray diffraction pattern of powder samples in Lindeman capil-
imidazolium), 123.09 (CH phenyl), 129.97 (CH imidazolium),
laries or sealed cells were measured in transmission by using a
130.47 (N-C phenyl), 135.79 (CH imidazolium), 158.48 (C-O-
focused CuKα1 linear beam, temperature control being within
CH2 phenyl). νmax/cm−1 3118 (C-H aromatic), 2921 and 2851
0.03 °C and acquisition being conducted with an Inel CS120
(C-H aliphatic), 1520 (C=C aromatic), 1243 (C-O aromatic).
curved counter. The molecular volumes of all compounds were
UV/Vis (CH2Cl2): λmax (ε, L·mol−1·cm−1) = 241 nm (15000).
calculated with an accuracy of 0.5% from the measurements
Elemental analysis for C21H32N2O, Cacld: C, 76.78; H, 9.82;
performed for an analogous compound [26] and from the
N, 8.53%. Found: C, 76.96; H, 10.58; N, 8.57%.
methylene and counter ion partial volumes.
1-[4-(Dodecyloxy)phenyl]-3-methyl-1H-
All reagents were purchased from commercial suppliers and
imidazol-3-ium iodide (1a)
used without further purification. Chromatography was carried
A mixture of A (1.069 g, 3.25 mmol) and iodomethane (2 mL,
out with Merck silica gel 60 (40–63 mm). Analytical TLC was
31.80 mmol) was stirred in a sealed tube for 54 h and was
performed with Merck silica gel 60 F254 aluminium sheets. 1H
heated to 40 °C for 10 minutes. Diethyl ether was added and the
NMR and 13C NMR (300 MHz and 75 MHz respectively)
reaction mixture was filtered and the solid was washed with
spectra were recorded with a Bruker Avance 300 spectrometer
diethyl ether. Crystallization with dichloromethane and diethyl
at 25 °C. Chemical shifts, δ, are reported in ppm using TMS as
ether gave de 1a (1.318 g, 89%).
internal standard, spin-spin coupling constants, J, are given in
Hz and the abbreviations s, br, s, t, q, m were used to denote
1H NMR (300 MHz, CDCl3): δ = 0.89 (t, 3H, J = 6.9 Hz, CH3
respectively the multiplicity of signals: singlet, broad singlet,
aliphatic chain), 1.28 (broad s, 16H, CH2 aliphatic chain),
triplet, quadruplet, multiplet. Infrared spectra were recorded
1.41–1.48 (m, 2H, O-CH2-CH2-CH2), 1.76–1.85 (m, 2H,
(KBr pastille) with a spectrophotometer IR Digital FTS 3000.
O-CH2-CH2), 3.99 (t, 2H, J = 6.6 Hz, O-CH2), 4.27 (s, 3H,
UV/Vis spectra were recorded with a spectrophotometer
N-CH3), 7.04 and 7.66 (AA′ and BB′, 2 × 2H, J = 9.1 Hz, CH
U-3000. Elemental analyses were performed by the analytical
phenyl), 7.46–7.48 (m, 2H, N-CH-CH-N), 10.45 (broad s, 1H,
service at the Institut Charles Sadron and by the analytical
N-CH-N). 13C NMR (75 MHz, CDCl3): δ = 14.01 (CH3
service at the Université de Strasbourg (Strasbourg, France).
aliphatic), 22.58, 25.89, 29.00, 29.25, 29.29, 29.48, 29.51,
The optical structures of mesophases were studied with a Leitz
29.54, 29.57, 31.82 (CH2 aliphatic), 37.57 (N-CH3), 68.65
polarizing microscope equipped with a Mettler FP80 hot stage
(O-CH2), 115. 99 (CH phenyl), 121.03 (CH imidazolium),
and an FP80 central processor. The TGA measurements were
123.65 (CH phenyl), 124.42 (CH imidazolium), 127.05 (N-C
carried out on a SDTQ 600 apparatus at scanning rate of
phenyl), 135.49 (CH imidazolium), 160.47 (C-O-CH2 phenyl).
10 °C·min−1. The transition temperatures and enthalpies were
νmax/cm−1 3131 (C-H aromatic), 2921 and 2851 (C-H
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
aliphatic), 1514 (C=C aromatic), 1251 (C-O aromatic). UV–vis
aliphatic), 22.65, 25.95, 29.08, 29.32, 29.37, 29.55, 29.59,
(CH2Cl2): λmax (ε, L·mol−1·cm−1) = 240 nm (24000). Elemental
29.61, 29.64, 31.89 (CH2 aliphatic), 36.81 (N-CH3), 68.65
analysis for C22H35IN2O·1/4H2O, Calcd: C, 55.64; H, 7.53; N,
(O-CH2), 115. 91 (CH phenyl), 121.60 (CH imidazolium),
5.90%. Found: C, 55.78; H, 7.48; N, 5.34%.
123.70 (CH phenyl), 124.33 (CH imidazolium), 127.21 (N-C
phenyl), 134.42 (CH imidazolium), 160.51 (C-O-CH2 phenyl).
General procedure for metathesis in
νmax/cm−1 2921 and 2850 (C-H aliphatic), 1516 (C=C
water–anion exchange
aromatic), 1255 (C-O aromatic), 826 cm−1 (PF6−). UV–vis
A mixture of 1a dissolved in dichloromethane (4 mL) and a
(CH2Cl2): λmax (ε, L·mol−1·cm−1) = 249 nm (11700). Elemental
mixture of the corresponding salts dissolved in water (3 mL)
analysis for C22H35F6N2OP·1/7H2O, Calcd: C 53.81, H 7.24, N
were stirred together for 140 h. The organic layer was separ-
5.70%. Found: C 53.77, H 7.31, N 5.51%.
ated off, washed with water and dried over calcium chloride.
Crystallization with dichloromethane and diethyl ether gave the
1-[4-(Dodecyloxy)phenyl]-3-methyl-1H-
corresponding imidazolium salt.
imidazol-3-ium trifluoromethanesulfonate (1d)
Following the general procedure using 1a (0.730 g, 1.55 mmol)
1-[4-(Dodecyloxy)phenyl]-3-methyl-1H-
and sodium trifluoromethanesulfonate (0.616 g, 3.51 mmol)
imidazol-3-ium tetrafluoroborate (1b)
provided 1d with a yield of 46% (0.349 g, 0.71 mmol).
Following the general procedure using 1a (0.797 g, 1.69 mmol)
and sodium tetrafluoroborate (0.511 g, 4.56 mmol) provided 1b
1H NMR (300 MHz, CDCl3): δ = 0.89 (t, 3H, J = 6.8Hz, CH3
with a yield of 72% (0.525 g, 1.22 mmol).
aliphatic chain), 1.28 (broad s, 16H, CH2 aliphatic chain),
1.41–1.46 (m, 2H, O-CH2-CH2-CH2), 1.76–1.83 (m, 2H,
1H NMR (300 MHz, CDCl3): δ = 0.86 (t, 3H, J = 6.3 Hz, CH3
O-CH2-CH2), 3.99 (t, 2H, J = 6.6 Hz, O-CH2), 4.10 (s, 3H,
aliphatic chain), 1.28 (broad s, 16H, CH2 aliphatic chain),
N-CH3), 7.02 and 7.51 (AA′ and BB′, 2 × 2H, J = 8.8 Hz, CH
1.41–1.46 (m, 2H, O-CH2-CH2-CH2), 1.75–1.84 (m, 2H,
phenyl), 7.49 (broad s, 2H, N-CH-CH-N), 9.41 (broad s, 1H,
O-CH2-CH2), 3.98 (t, 2H, J = 6.3 Hz, O-CH2), 4.11 (s, 3H,
N-CH-N). 13C NMR (75 MHz, CDCl3): δ = 13.96 (CH3
N-CH3), 7.02 and 7.53 (AA′ and BB′, 2 × 2H, J = 9.0 Hz, CH
aliphatic), 22.54, 25.85, 28.97, 29.21, 29.26, 29.44, 29.48,
phenyl), 7.48 (broad s, 2H, N-CH-CH-N), 9.37 (broad s, 1H,
29.51, 29.53, 31.78 (CH2 aliphatique), 36.52 (N-CH3), 68.54
N-CH-N). 13C NMR (75 MHz, CDCl3): δ = 14.07 (CH3
(O-CH2), 115. 84 (CH phenyl), 120.49 (q, J = 318.18 Hz,
aliphatic), 22.65, 25.95, 29.08, 29.32, 29.37, 29.55, 29.59,
CF3SO3−), 121.36 (CH imidazolium), 123.33 (CH phenyl),
29.61, 29.64, 31.89 (CH2 aliphatic), 36.81 (N-CH3), 68.65
124.44 (CH imidazolium), 127.15 (N-C phenyl), 134.95 (CH
(O-CH2), 115. 96 (CH phenyl), 121.34 (CH imidazolium),
imidazolium), 160.36 (C-O-CH2 phenyl). νmax/cm−1 3119 (C-H
123.59 (CH phenyl), 124.50 (CH imidazolium), 127.24 (N-C
aromatic), 2915 and 2849 (C-H aliphatic), 1520 (C=C
phenyl), 134.97 (CH imidazolium), 160.47 (C-O-CH2 phenyl).
aromatic), 1269 and 1028 (CF3SO3−). UV–vis (CH2Cl2): λmax
νmax/cm−1 2917 and 2849 (C-H aliphatic), 1514 (C=C
(ε, L·mol−1·cm−1) = 256 nm (10100). Elemental analysis for
aromatic), 1249 (C-O aromatic), 1024 (BF4−). UV–vis
C22H35F3N2O4S, Cacld: C 56.08, H 7.16, N 6.59%. Found: C
(CH2Cl2): λmax (ε, L·mol−1·cm−1) = 255 nm (10500). Elemental
55.84, H 6.86, N 5.40%.
analysis for C22H35BF4N2O·3/4H2O, Calcd: C 59.53, H 8.29, N
1-[4-(Dodecyloxy)phenyl]-3-methyl-1H-
6.31%. Found: C 59.74, H 8.02, N 6.20%.
imidazol-3-ium bis(trifluoromethane) sulfon-
1-[4-(Dodecyloxy)phenyl]-3-methyl-1H-
amide (1e)
imidazol-3-ium hexafluorophosphate (1c)
1a (0.101 g, 0.21 mmol) and lithium bis(trifluoromethane)-
Following the general procedure using 1a (0.695 g, 1.48 mmol)
sulfonamide (0.145 g, 0.51 mmol) were dissolved in water (3
and potassium hexafluoroborate (0.518 g, 2.18 mmol) provided
mL) and stirred for 140 h. The precipitate was filtred and
1c with a yield of 84% (0.607 g, 1.24 mmol).
washed. Crystallization (chloroform/cyclohexane) provided 1e
with a yield of 90% (0.121 g, 0.19 mmol).
1H NMR (300 MHz, CDCl3): δ = 0.89 (t, 3H, J = 6.8 Hz, CH 3
aliphatic chain), 1.28 (broad s, 16H, CH2 aliphatic chain),
1H NMR (300 MHz, CDCl3): δ = 0.89 (t, 3H, J = 6.8 Hz, CH3
1.41–1.46 (m, 2H, O-CH2-CH2-CH2), 1.76–1.85 (m, 2H,
aliphatic chain), 1.28 (broad s, 16H, CH2 aliphatic chain),
O-CH2-CH2), 3.98 (t, 2H, J = 6.6 Hz, O-CH2), 4.07 (s, 3H,
1.42–1.52 (m, 2H, O-CH2-CH2-CH2), 1.77–1.86 (m, 2H,
N-CH3), 7.02 and 7.48 (AA′ and BB′, 2 × 2H, J = 8.8 Hz, CH
O-CH2-CH2), 4.01 (t, 2H, J = 6.6 Hz, O-CH2), 4.07 (s, 3H,
phenyl), 7.45 (broad s, 2H, N-CH-CH-N), 9.10 (broad s, 1H,
N-CH3), 7.05 and 7.46 (AA′ and BB′, 2 × 2H, J = 8.8 Hz, CH
N-CH-N). 13C NMR (75 MHz, CDCl3): δ = 14.06 (CH3
phenyl), 7.43–7.49 (m, 2H, N-CH-CH-N), 8.98 (broad s, 1H,
Page 9 of 10
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Beilstein Journal of Organic Chemistry 2009, 5, No. 51.
N-CH-N). 13C NMR (75 MHz, CDCl3): δ = 14.06 (CH3
15. Suisse, J.-M.; Bellemin-Laponnaz, S.; Douce, L.; Maisse-François, A.;
aliphatic), 22.65, 25.94, 29.05, 29.31, 29.34, 29.53, 29.57,
Welter, R. Tetrahedron Lett. 2005, 46, 4303–4305.
doi:10.1016/j.tetlet.2005.04.114
29.60, 29.63, 31.89 (CH2 aliphatic), 36.69 (N-CH3), 68.70
16. Dobbs, W.; Suisse, J.-M.; Douce, L.; Welter, R. Angew. Chem., Int. Ed.
(O-CH2), 116.04 (CH phenyl), 119.77 (q, J = 319.29 Hz,
2006, 45, 4179–4182. doi:10.1002/anie.200600929
CF3SO3−), 121.89 (CH imidazolium), 123.77 (CH phenyl),
17. Dobbs, W.; Douce, L.; Allouche, L.; Louati, A.; Malbosc, F.; Welter, R.
124.31 (CH imidazolium), 126.99 (N-C phenyl), 134.67 (CH
New J. Chem. 2006, 30, 528–532. doi:10.1039/b600279j
imidazolium), 160.78 (C-O-CH2 phenyl). νmax/cm−1 2918 and
18. Suisse, J.-M.; Douce, L.; Bellemin-Laponnaz, S.; Maisse-François, A.;
Welter, R.; Miyake, Y.; Shimizu, Y. Eur. J. Inorg. Chem. 2007,
2850 (C-H aliphatic), 1517 (C=C aromatic), 1358 cm−1 and
3899–3905. doi:10.1002/ejic.200700251
1 1 8 3 ( ( C F 3 S O 2 ) 2 N − ) . U V – v i s ( C H 2 C l 2 ) : λ m a x ( ε ,
19. Yazaki, S.; Kamikawa, Y.; Yoshio, M.; Hamasaki, A.; Mukai, T.;
L·mol−1·cm−1) = 255 nm (11100). Elemental analysis for
Ohno, H.; Kato, T. Chem. Lett. 2008, 37, 538–539.
C24H35F6N3O5S2.1/2H2O, Cacld: C 45.56, H 5.74, N 6.64%.
doi:10.1246/cl.2008.538
Found: C 45.52, H 5.66, N 6.58%.
20. Yoshio, M.; Ichikawa, T.; Shimura, H.; Kagata, T.; Hamasaki, A.;
Mukai, T.; Ohno, H.; Kato, T. Bull. Chem. Soc. Jpn. 2007, 80,
Acknowledgements
1836–1841. doi:10.1246/bcsj.80.1836
21. Fanta, P. E. Synthesis 1974, 9–21. doi:10.1055/s-1974-23219
We are especially grateful to Dr. J. Harrowfield for the critical
22. Kouwer, P. H. J.; Swager, T. M. J. Am. Chem. Soc. 2007, 129,
evaluation of the manuscript. This work was supported by the
14042–14052. doi:10.1021/ja075651a
Institut for Physics and Chemistry of Materials Strasbourg and
23. Kantam, M. L.; Rao, B. P. C.; Choudary, B. M.; Reddy, R. S. Synlett
University of Strasbourg.
2006, 14, 2195–2198. doi:10.1055/s-2006-949615
24. Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
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