Heterogeneous microwave-assisted Ullmann type methodology for synthesis of rigid-core ionic liquid crystals

Article abstract of DOI:10.1039/c8nj01609g

We present an efficient Ullmann-type synthesis methodology enabling the preparation of imidazolium compounds with an extended aromatic core in three steps. This procedure begins with a microwave-assisted, heterogeneously catalysed cross-coupling reaction

Full text of DOI:10.1039/c8nj01609g

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Heinrich, M. L'Her, E. Voirin, L. Karmazin, C. Bailly, R. Welter, A. Mirjafari and L. Douce, New J. Chem.,
2018, DOI: 10.1039/C8NJ01609G.
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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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ARTICLE
Heterogeneous Microwave-assisted Ullmann type Methodology
for Synthesis of Rigid-core Ionic Liquid Crystals.
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
a
b
Julien Fouchet, Benoît Heinrich, Matthieu L’Her, Emilie Voirin, Lydia Karmazin, Corinne
Bailly, b Richard Welter, c Arsalan Mirjafari d and Laurent Douce*a
DOI: 10.1039/x0xx00000x
We present an efficient Ullmann-type synthesis methodology enabling the preparation of imidazolium compounds with an
www.rsc.org/
extended aromatic core in three steps. This procedure begins with
a microwave-assisted, heterogeneously
catalysed cross-coupling reaction in the presence of Cu(II)-doped NaY zeolite to obtain imidazole-aromatic derivatives
directly in good yield. The innovation is that this reaction does not require solvent, ligand or an inert
atmosphere. Subsequently, these derivatives have been alkylated with bromoalkanes and the bromide of the imidazolium
products exchanged for [BF4]- or [PF6]- anions. We have studied the influence of the methyl group (inductive effect) on the
aromatic unit during the coupling reaction as well as its impact on different arrangements in the crystalline state. We have
been able to extend this synthesis to ionic liquid crystal compounds which display lamellar self-organization (Smectic A).
The mesomorphic behavior and phase transition temperatures were investigated by polarizing optical microscopy (POM),
differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS).
copper(II) supported on zeolites or fluorapatite heated in N,N-
dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) have
been found to provide useful alternatives, although still with
reactions periods ranging from a few hours to one day. In a
few, isolated cases, it has been found possible to accelerate
the homogeneous catalysis using microwave heating.16
Introduction
Ionic liquids based on imidazolium units are compounds with
novel properties, most being liquid at room temperature.1, 2
Those of an amphiphilic nature undergo self-organization in
the liquid crystal state and such properties have led to
applications ranging from templating media for synthesis to
biological activity in the targeting and transporting of drugs
and genetic materials.3-7
Results and Discussion
In this article, we present a method of heterogeneous catalysis
which does not require any solvent, nor any chiral ligands or
inert atmosphere. In addition, the imidazole derivatives are
In order to obtain imidazolium liquid crystal salts with large,
rigid cores, considerable efforts have been devoted to the
synthesis of aromatic units with imidazolium substituents.8-12
Ullmann coupling, which involves the reaction of a bromo-
aromatic with imidazole, is a useful direct pathway to such
species.13, 14 Conventional conditions for this reaction involve
(i)
(ii)
N
X
Aromatic
+
Aromatic
N
Aromatic
HN
N
N
N
R
Br
Scheme 1: Synthesis of bromide imidazolium extended aromatic core. Reactions: (i)
the presence of
a chelating ligand (L-proline), copper
Cu(II)-NaY, K2CO3, 180°C, 140 min; (ii) BrC12H25, Microwave oven 110°C, 140min.
iodide(CuI) and a base (K2CO3) dissolved in a solvent such as
dimethyl sulfoxide (DMSO) under an inert atmosphere.15 The
reaction is sometimes capricious and heterogeneous
procedures involving solid catalysts such as CuO nanoparticles,
obtained within a short reaction time (140 min) by using
microwave heating and the Cu(II)-zeolite catalyst can easily be
recycled. Through this approach, it is now possible to carry out
a two-step, efficient synthesis of imidazolium-based ionic
materials with N-substituted aromatic cores in good yield and
on the gram scale.
To optimize this procedure, we have explored the effects of
heating in the range 125 - 180 °C on reaction mixtures
consisting of 1H-imidazole (0.277 g, 2.78 mmol), potassium
carbonate (0.250 g, 1.81 mmol), Cu(II)-NaY (0.183 g) and
various halogeno-benzene derivatives (1.28 mmol) without
solvent. The results obtained are summarized in Table 1.
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Table 1: Ajouter un titre ici
* : homocoupling biphenyl product in trace.
Starting
aromatics
Temperature
(°C)
125
130
135
145
150
155
160
180
*
37 %
44 %
46 %
5 %
5 %
39 %
45 %
54%
37 %
48 %
Traces
8 %
3 %
10 %
84 %
11 %
54 %
49 %
84 %
As expected, chlorobenzene shows poor reactivity but
reactions of both bromo- and iodo-benzene proceed in good
yield, although with detectable amounts of homo-coupling
product for the last. Yields generally increase with increasing
temperature but for some functionalised halo-aromatics,
product instability at 180 ° appears to be the cause of lower
yields than at 155 °. The optimal conditions eventually defined
for the synthesis of a range of new N-aryl imidazoles are given
Table 2
Starting
material
Temperature
°C
Imidazole
product
Yield
%
180
160
180
180
155
84
54
56
69
54
in Table 2.
These N-aryl-imidazoles react readily with 1-bromododecane
to give amphiphilic imidazolium species in good yields. The
bromide salts formed directly are easily converted to
tetrafluoroborate (BF4) or hexafluorophosphate (PF6) salts by
anion metathesis reactions in CH2Cl2/H2O.
All these imidazolium salts are air stable and can be purified by
column chromatography on silica. Overall reaction yields and
some selected spectroscopic data for the derivatives of
imidazoles 1 - 5 are given in Table 3.
Self-assembly in the crystalline state
Single crystals of 1Br (CCDC 1830446), 2PF6(CCDC 1830444), 3Br
(CCDC 1830443) and 4Br (CCDC 1830445) suitable for single
crystal X-Ray diffraction were obtained by slow diffusion of
diethyl ether (Et2O) into dichloromethane (CH2Cl2) solutions.
ORTEP views of the ionic aggregates and packing within the
unit cells are given in Table
4 and Figure 1. The four samples
crystallize into similar lamellar structures, formed by the
alternation of layers of cores and of aliphatic chains. All three-
dimensional cells, of either monoclinic (4Br
2PF6) geometry, involve a single lamella and 4 molecules in the
unit cell (Table 4 and Fig. 1).
, 3Br, 1Br) or triclinic
Scheme 2: (i) Microwave oven, 110°C, 140 min; (ii) Anion metathesis in H2O/CH2Cl2 as
solvent
(
In the monoclinic bromide salt structures, the cores arrange
head-to-tail into a ribbon structure made by the alternation of
single rows of phenyl segments and of double-rows of
imidazolium bromide. The head-to-tail arrangement removes
steric constrains from the unequal bulkiness of both core
moieties, and the molecular area S = bc/Z therefore represents
the average cross-sectional area of the cores c
3Br: S = 27.7; 1Br: S = 29.2 Å2). These areas are above the cross-
sectional area of the pendent all-trans dodecyl chains (ch
18.5 Å2) and the chains consequently tilt from the appropriate
angle to compensate for the discrepancy (4Br  = 51°; 3Br
= 48°; 1Br = 50°).
(4Br: S = 28.9;


:
: 
:

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The presence of the long chain on the imidazolium ring turned
out to be determinant for the ionic liquid properties, as is
obvious from comparison of 3BF4 and its isomer with inverted
Table 3:
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DOI: 10.1039/C8NJ01609G
a 1H: Chemical shift for the CH (imidazolium) is very dependent upon the anion.
b IR: typical BF4- and PF6- anion vibration.
c UV absorption bands: max ( L.mol-1.cm-1)
Yield
(%)
85
1H NMRa
(ppm)
11.12
9.10
IRb
Electronic
Compound
(cm-1)
Absorptionc
254 nm (11500)
257 nm (10800)
255 nm (9900)
229 nm (10500)
230 nm (8800)
231 nm (8200)
240 nm (10300)
237 nm (10000)
237 nm (9400)
231 nm (7900)
231 nm (8600)
231 nm (8400)
268 nm (14100)
264 nm (14700)
262 nm (14100)
1Br
1BF4
1PF6
2Br
60
1068
823
95
8.96
chain positions 0BF4 (see Scheme 3 and Table 5). In fact, 3BF4
,
85
10.95
9.21
with the long chain on imidazolium, is a room-temperature
ionic liquid, with melting and glass transitions at respectively
20°C and -40°C, while 0BF4, with the long chain on phenyl, is
crystalline up to 91°C, melts to a mesophase and reaches the
transition to isotropic liquid at only 230°C.22
2BF4
2PF6
3Br
57
1027
830
81
8.86
94
10.58
9.17
3BF4
3PF6
4Br
80
1049
809
91
8.90
Underlying such a remarkable difference in thermal behavior,
there must be a major difference in self-assembly which
should be apparent in the solid-state structures. Fortunately,
single-crystal structures are available for two salts analogous
to 3BF4 and 0BF4, though with Br- or I- counter-ion instead of
90
10.54
9.19
4BF4
4PF6
5Br
77
1050
846
92
8.93
60
11.41
9.33
5BF4
5PF6
50
1021
829
-
BF4 . In the 0I structure, ions arrange in double-layers
95
8.99
conferring a strong lateral cohesion to lamellae and leading to
For
3 and 4, the optimal compactness of the molecular self-
a
high melting temperature and the induction of
assembly is finally reached by the interdigitation of the
dodecyl chains and their facing with the methyl groups from
the next lamella, while for 1Br, the chains of equal length just
superpose into bilayers. The absence of the chain on the
phenyl segment for 2PF6 enables the disentanglement of the
head-to-tail arranged cores and arrangement in two ionic
strata separated by central strata of interdigitated phenyl
groups. Compared to the entangled structures, the removal of
the phenyl results in the rearrangement of the ionic moieties
mesomorphism. The spatial requirements of the cations
impose a high molecular area (S = 57.1 Å2) to the whole layer
sequence and thus a high tilting of the crystallized chains (
 =
71°). In 3Br, ionic double-layering is excluded due to the
necessary intercalation of the long dodecyl chains connected
to imidazolium, and cores consequently arrange in monolayers
separated by aliphatic layers. The head-to-tail arrangement
adopted, with superposition of methyl and dodecyl chains and
intercalation of chains from neighboring lamellae, enables a
more compact lateral packing and ultimately more efficient
nanosegregation of chains and cores. Remarkably, the lateral
shrinking of lamellae goes even beyond the minimum
into an oblique lattice with an area per ionic unit

ion = 44.8 Å2.
ion/2
The lateral extension of lamellae is hence reduced to S =

= 22.4 Å2, which is still above the cross-sectional area of alkyl
chains and thus effectively allows their interdigitated
arrangement, but the tilt is only 34°, due to the smaller gap
requirement of ions (S = 27.7 < ion

37 Å2) due to the ribbon
structure reducing this requirement to the average cross-
section of mesogens. As a result, the alternation of segments
of different nature (i.e. phenyl and imidazolium) between
staggered rows is detrimental for strong ionic interactions and
for the lateral cohesion of lamellae. As a consequence, the
self-assembled structure dissociates at low temperature and
promotes the ionic liquid properties.
between ch and S.
Ionic liquid properties
All samples form crystalline solids near room temperature but
with melting points which vary from just below room
temperature to near 100 °C. As liquids, the bromide salts are
stable up to 210-220°C while the BF4 and PF6 salts are stable
up to 250 °C, above which temperature weight loss from
degradation was detected in TGA curves (Figure
can all be considered as ionic liquids. Those of series
(with the methyl group on phenyl) exhibit however the best
ionic liquid properties, as they melt at low temperature, stay
supercooled for hours or days at room temperature and show
-
-
Apart from the presence of a long chain on imidazolium, that
of a small methyl group on phenyl is also beneficial to ionic
2
). Thus, they
and
3
4
liquid properties. Lacking this feature, compounds of series
2
melt at relatively high temperatures and crystallize on cooling.
The origin of this effect is revealed by the crystal structure of
2PF6, for which the head-to-tail arrangement gives way to
disentanglement into strata of flat ionic monolayers. These
ionic monolayers improve the cohesion of lamellae and thus
delay the melting of the crystalline structure. This unfavorable
disentanglement can be avoided by the presence of a short
alkyl chain on phenyl, explaining the better ionic liquid
subambient glass transitions (see Table 5). Three of them (3BF4,
4BF4 and 4PF6) are even stable room temperature ionic liquids
that slowly crystallize at negative temperatures and melt again
on returning to room temperature. These results are in
contrast with those on similar compounds bearing longer alkyl
tail on the aromatic part which are glassy or crystalline phase
at room temperature; we have succeeded to stabilise the ionic
liquid state until -40°C thanks to the contribution of the
terminal methyl groups.15, 17-21
properties of series
however again
3
and
4. The long alkyl chain in series 1 has
a
negative effect, due to induction of
mesomorphism. Finally, the compounds with the largest
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anions 3BF4
,
3PF6
,
4BF4, and 4PF6 show the best ionic liquid lateral expansion in presence of ionic double-layers,
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DOI: 10.1039/C8NJ01609G
properties, presumably because of larger differences of cross- confirming their higher cohesivity as compared to monolayers
section that hamper the self-assembly in the solid state.
Mesomorphic properties
and clarifying the origin of the detrimental effect on
mesomorphic properties of the chain connected to
imidazolium.
Only series
50-100°C smectic A (SmA) range, between melting and
transition to the isotropic ionic liquid (Table and Figure
1 salts display mesomorphic properties, namely a
5
4
left). The identification of the mesophase from the
characteristic focal-conic POM texture was confirmed by the
composition of SAXS patterns, associating several sharp small-
angle reflections from the lamellar periodicity ((00l)) and a
broad wide-angle scattering signal from lateral distances
between molten chains (hch) and mesogenic cores (hmes
(Figure left).
The appearance of a smectic phase for series
)
5
1
was expected,
due the presence of the two long dodecyl chains that naturally
nanosegregate from mesogen cores into layers. Accordingly,
the mesomorphic properties vanish for series 3, i.e. with the
replacement of the dodecyl chain on the phenyl by methyl.
The same replacement for the chain on imidazolium
counterintuitively extends the SmA range, the isotropization
temperature rising even by 90°C from 1BF4 to 0BF4 (Table
The reason is obviously an underlying self-assembly change,
reflecting that observed in the solid state (see above). Series
was indeed reported to self-organize with ruffled ionic double-
layers and series necessarily arrange into ionic monolayers
(Fig. ). A direct sign of the structural change is the drop of
layer spacing following the transition from smectic
5).
0
1
6
a
periodicity of two-molecular-layers’ to only one-molecular-
layer (d = 38.6 Å for 0BF4 and d = 28.4 Å for 1BF4, at 120°C).
Another consequence is the lower cohesivity of the ionic
monolayers as compared to ionic bilayers, which largely
explains the differential of isotropization temperature.
More profound investigation of the self-assemby necessitates
combining SAXS measurements with volumetric data. The
molecular volume Vmol of 1Br was measured by dilatometry and
displayed classical 5% volume jump at melting and 7.10-4 °C-1
volumetric expansion in the mesomorphic range (Figure
4
right), and Vmol of 1BF4 and 1PF6 were deduced from 1Br by
considering anion volume differences. The molecular area in
the smectic plane was then calculated from the formula S =
NLVmol/d, in which NL represents the number of molecular
layers per lamella, i.e. NL = 2 for 0BF4 and NL = 1 for 1BF4. These
areas (S = 34.6 Å2 and 32.0 Å2, respectively, at 120°C) are
intermediate between the cross-sectional area of a molten
chain (ch = 22.8 Å2 at 120°C) and that estimated for the ionic
lattice (ion

41 Å2), allowing for complications such as ruffling
of the ionic layers and folding of the molten aliphatic chains
[xx1, xx2]. It should be mentioned that the rather comparable
S values indicate little impact of the layer assembly on the
subtle balance between these competing mechanisms. The
value reached by S just before isotropization is on the contrary
greatly affected, as it drops from 41.8 Å2 to 33.2 Å2 with the
change from double-layer to single-layer configuration (these
values were obtained by the extrapolation of the variations of
S with temperature). The lamellae thus accept much higher
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Table 4: Crystal data and refinement details for 2PF6, 4Br, 3Br, 1Br
View Article Online
DOI: 10.1039/C8NJ01609G
Crystal Data
2PF6
C21H33N2, PF6
458.46
Triclinic
P-1
4Br
3Br
C22H35N2, Br
407.43
1Br
Formula
C22H35N2, Br
407.43
C33H57N2O, Br
Formula weight (g.mol-1)
Crystal system
577.72
Monoclinic
P 21/c
Monoclinic
P 21/c
Monoclinic
P 21/c
Space group
a [Å]
b [Å]
c [Å]

8.3458(8)
10.7404(11)
26.252(3)
79.541(2)
19.1863(15)
14.2196(12)
8.1410(6)
90
20.4743(10)
14.5386(6)
7.5277(4)
90
28.2048(7)
14.7269(4)
7.9430(2)
90


87.329(2)
89.045(2)
2311.5(4)
4
98.485(2)
90
2196.7(3)
4
100.385(3)
90
2204.05(18)
4
91.506(2)
90
3298.14(15)
4
V [Å3]
Z
F(000)
968
864
864
1248
Density (calc) [g.cm-3]
(MoK) [mm-1]
Form and colour
Crystal Size [mm]
Data Collection
 Min-Max [°]
Dataset [h,k,l]
Tot., Uniq. Data, R(int)
Observed data [I > 2(I)]
Refinement
1.317
0.177
Plate, colourless
0.400.200.03
1.232
1.88
Plate, colourless
0.450.200.05
1.228
1.87
Plate, colourless
0.400.200.05
1.272
1.163
Plate, colourless
0.150.150.10
1.93 – 29.02
2.15 - 28.00
1.00 - 27.50
1.56 – 27.50
-11/11,-14/14,-35/34
34173, 12278, 0.077
6904
-25/24,-18/18,-10/10
15505, 5300, 0.0443
3661
-26/23,-18/18,-9/7
16002, 5009, 0.072
3628
-29/36,-19/17,-10/8
20789, 7485, 0.057
5334
Nreflections, Nparameters
R1,wR2, Goof
Max. and Av. Shift/Error
Min,Max.Resd.Dens.[e/Å3]
12278, 543
5300, 228
5009, 228
7485, 330
0.044, 0.1033, 1.023
0.001, 0.000
0.072, 0.206
0.000, 0.000
-0.604, 1.145
0.042, 0.1064, 1.005
0.000, 0.000
-0.38, 0.48
0.061, 0.165, 1.16
0.000, 0.000
-0.47, 0.35
-0.413, 0.318
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Figure 1: Views of the molecular self-assembly in different crystallographic planes of the four single-crystal structures: (1st line) cross-sectional images of the lamellar plane
showing intercalation and ribbons; (2nd line) cross-sectional images of the lamellar plane in the perpendicular direction; (3nd line) arrangement in the plane of the top half-core-
layer; (4th line) arrangement in the ionic bottom half-core-layer.
2PF6
4Br
3Br
1Br
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Table 5: Initial state, phase sequence, transition temperatures (T) and enthalpies (H)
from DSC (1st heating), and final state on returning to room temperature, for the series
of mesomorphic salts 1, and for the series of ionic liquids 2-5; Liq or Iso: stable ionic
liquid state, same as isotropic liquid phase; Liq (sup.): supercooled ionic liquid
(crystallizes in hours’/days’/weeks’ time); G: glass; Cr, Cr1, Cr2: crystal; SmA: smectic A
phase; *data from literature reference [xx1]
Ref.
Pristine
State
Cr
Cr
Cr
Transition
on Heating
Cr  Liq
Cr  Liq
Cr  Liq
Cr  Liq
G  Liq
Liq  Cr
Cr  Liq
Cr  Liq
Cr  Liq
G  Liq
T
(°C)
53
51
80
60
-40
-6
20
41
H
(kj.mol-1)
10
Final RT
State
Liq (sup.)
Liq (sup.)
Cr
Figure 2: Right - TGA curves of the dry salts of series 1-4 (ramps of 10°C/min),
after first heating to 100 °C for drying. Whatever the mesogen substitution, the
bromide salts show weight losses due to decomposition above 210-220 °C and
5% weight loss temperatures around 245 °C. Incomplete drying at 100°C and
2Br
2BF4
2PF6
3Br
evaporation of the residual water presumably explains the slight drift of the TGA
-
curves of BF4- and PF6 salts at lower temperatures, whilst the downward curving
35
39
36
0
22
22
24
40
0
23
24
0
20
18
17
32
from decomposition start is delayed to about 250 °C and demonstrates an
improved thermal stability. Left - TGA curves of the dry salts of series
1 (ramps of
10°C/min), after first heating to 100 °C for drying. Weight losses related to
decomposition starts from 200 to 240 °C and the 5% weight loss temperatures,
for the 10 °C/min ramps, are of 244 °C ( Br), 292 °C ( BF4), and 260 °C ( PF6).
Cr
Liq (sup.)
1
1
1
3BF4
Liq
Liq
3PF6
4Br
Cr
Cr
Liq (sup.)
Liq (sup.)
66
-47
-16
22
-48
-17
9
96
54
72
4BF4
Liq
Liq
Liq  Cr
Cr  Liq
G  Liq
Liq
4PF6
Liq  Cr
Cr  Liq
Cr  Liq
Cr  Liq
Cr  Liq
Cr1  Cr2
Cr2  SmA
SmA  Iso
Cr  SmA
SmA  Iso
Cr  SmA
SmA  Iso
Cr2 SmA
SmA  Iso
Cr  SmA
SmA Iso
Cr  SmA
SmA  Iso
Liq
Liq (sup.)
Liq (sup.)
Cr
5Br
5BF4
5PF6
Cr
Cr
Cr
18
80
43
15
3.8
55
3.5
52
1Br
Cr
103
188
58
140
65
110
113
250
91
230
97
1BF4
1PF6
0I*
Cr
Cr
Cr
Cr
Cr
CR
Cr
Cr
Cr
Cr
2.6
15.8
30.1
0BF4
0PF6
36.2
1.12
163
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ARTICLE
Journal Name
coupling chromophores to promote luminescence properties
View Article Online
DOI: 10.1039/C8NJ01609G
in liquid and mesomorphic states.
General Synthetic Methods
Reagents and solvents were purchased from commercial
sources (Aldrich, Acros, Fluka) and used without further
purification unless otherwise specified. Thin layer
chromatography (TLC) was performed Merck silica gel 60 F254
aluminium sheets with visualization by UV light or staining.
Flash column chromatography was performed using silica gel
60 (40-63 mm) standardized from Merck. 1H NMR (300.13
MHz) and 13C NMR (75.48 MHz) spectra were recorded on a
Brucker Avance 300 spectrometer. Chemical shifts (δ) are
given in parts per million (ppm) referenced to residual
protonated solvent (CDCl3: δH 7.27 ppm, δC 77.00 ppm).
Abbreviations used are s (singlet), broad s (broad singlet), d
(doublet), dd (doublet of doublets), t (triplet), broad t (broad
triplet), qua (quadruplet), quin (quintet), m (multiplet) and
broad m (broad multiplet). FT-IR spectra were recorded (KBr)
on IR Digilab FTS 3000 spectrophotometer. UV/Vis spectra
were recorded with
Wavelengths, max, are given in nm and the molar absorption
coefficient, , in L.mol-1.cm-1. Luminescence spectra were
recorded with Photon Technology International
a
spectrophotometer U-3000.

a
spectrophotometer (Motor Driver 5020, Lamp Power Supply
220B, Photomultiplier Detection System 814, Felix software).
Elemental Analyses were performed by the Institute Charles
Sadron (ICS). The optical structures of mesophases were
studied with a Leitz polarizing microscope equipped with a
Mettler FP80 hot stage and an FP80 central processor. The
TGA measurements were carried out on a SDTQ 600 apparatus
at scanning rate of 10 °C.min-1. The transition temperatures
and enthalpies were measured by differential scanning
calorimetry with a DSC Q1000 from TA Instruments at different
temperature rates (5 °C.min-1, 2 °C.min-1) on heating and
cooling. The device was calibrated with indium (156.6 °C, 28.4
J.g-1) and gallium (29.8 °C) as the standards. SAXS patterns
were recorded by curve counter (CPS120 model from INEL).
Samples were directly filled in Lindemann capillaries of 0.5 mm
diameter. SAXS of powder samples in Lindeman capillaries or
sealed cells were measured in transmission by using a focused
CuKα1 linear beam, temperature control being within 0.03°C
and acquisition being conducted with an Inel CS120 curved
counter. All microwave experiments were carried out in a
dedicated Anton Paar Monowave-300 reactor, operating at a
frequency of 2.455 GHz with continuous irradiation power of
0–850 W. The reactions were performed in a G-30 Borosilicate
glass vial sealed with Teflon septum and placed in a microwave
cavity. Initially, a microwave intensity of the required power
was used and temperature was ramped from room
temperature to a desired temperature. Once this temperature
was attained, the process vial was held at this temperature for
the required time. The reaction mixtures were continuously
stirred. Temperature was measured by an IR or thermometer
sensors. After the experiments a cooling jet cooled the
reaction vessel to ambient temperature.
Conclusions
An Ullmann-type microwave-assisted synthesis methodology,
solvent-free and without an inert atmosphere and chelating
ligand, makes it possible to prepare imidazolium derivatives
with an aromatic core extension in a minimum of steps.
Several aryl-core imidazolium salts with anions (Br, BF4 and
PF6) have been characterized and their ionic liquid and
mesomorphic properties considered in relation to their solid-
state structure. The crystalline structures are in all cases
lamellar and based on the alternation of ionic and aliphatic
layers. When a short methyl group was present on the
aromatic core side and a long alkyl chain on the imidazolium
core side, ions arranged in monolayers with a staggered row
structure. This arrangement implies a weak cohesion in the
lamellar plane that lowers the melting temperatures, so that
stable room temperature ionic liquids were obtained when
voluminous BF4 and PF6 anions were used. Interchanging of
the positions of long and short chains or connection of two
long chains resulted in the appearance of Smectic
mesophases, of either the monolayer or the double-layer type.
These results confirmed that the self-assembly is adjustable
over a broad range by following simple design rules. Combined
with the versatility of the Ullmann-type microwave-assisted
synthesis, this methodology paves the way for the molecular
engineering of specific liquid or mesomorphic materials. Along
this line, we will in the near future study the possibility of
-
-
A
8 | J. Name., 2012, 00, 1-3
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Page 9 of 13
New Journal of Chemistry
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ARTICLE
General procedure for Ullmann type-coupling (C-N bond
formation).

max/cm-1 3116 (C-H aromatic), 1522 (C=C aromatic). UV/Vis
View Article Online
DOI: 10.1039/C8NJ01609G
-1
-1
(CH2Cl2): max ( L.mol .cm ) = 240 nm (11100). Elemental
.
analysis for C10H10N2 0.08H2O, Calculed: C, 75.24; H, 6.41; N,
17.55 %. Found: C, 75.18; H, 6.50; N, 17.40 %.
1-m-tolyl-2H-imidazole (4).
A mixture of aryl halide, imidazole, potassium carbonate and
Cu(II)-NaY was heated with a microwave oven for 140 minutes
in sealed vessel. The reaction mixture was extracted with
dichloromethane, filtered to remove the catalyst and the
filtrate was purified by flash chromatography (silica gel, ethyl
acetate/cyclohexane: 30/70) or by column chromatography
(silica gel, ethyl acetate) to afford the product.
Following the general procedure using 1-bromo-3-
methylbenzene (0.509 g, 2.98 mmol), imidazole (0.324 g, 4.76
mmol), potassium carbonate (0.569 g, 4.12 mmol) and Cu(II)-
NaY (0.335 g) at 180 °C provided
g, 2.07 mmol). 1H NMR (300 MHz, CDCl3):
CH3 phenyl), 6.90-7.12 (broad m, 6H, CH phenyl and N-CH-CH-
N), 7.62 (s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
= 20.59
(C-CH3 phenyl), 117.42, 117.61, 121.18, 127.40, 128.90,
129.50, 134.76 (CH phenyl and imidazole), 136.52 (C-CH3
phenyl), 139.23 (N-C phenyl).
1503 (C=C aromatic). UV/Vis (CH2Cl2): max
4
with a yield of 69 % (0.327

= 2.16 (s, 3H, C-
1-(4-(dodecyloxy)phenyl)-2H-imidazole (1).
Following the general procedure using 1-dodecyloxy-4-
iodobenzene (0.499 g, 1.28 mmol), imidazole (0.189 g, 2.78
mmol), potassium carbonate (0.250 g, 1.81 mmol) and Cu(II)-

NaY (0.183 g) at 180 °C provided
g, 1.09 mmol). H NMR (300 MHz, CDCl3): = 0.88 (t, 3H, J =
1
with a yield of 84 % (0.359

max/cm-1 3055 (C-H aromatic),
1

(
L.mol-1.cm-1) =
6.48 Hz, CH3 aliphatic chain), 1.27 (broad s, 16H, CH2 aliphatic
chain), 1.42-1.49 (m, 2H, O-CH2-CH2-CH2), 1.80 (q, 2H, J = 6.57
Hz, O-CH2-CH2), 3.98 (t, 2H, J = 6.57 Hz, O- CH2), 6.96 and 7.27
(AA’ and BB’, 2*2H, J = 8.97 Hz, CH phenyl), 7.17-7.19 (m, 2H,
N-CH-CH-N), 7.75 (broad s, 1H, N-CH-N). 13C NMR (75 MHz,
.
240 nm (8800). Elemental analysis for C10H10N2 0.45H2O,
Calculed: C, 72.22; H, 6.61; N, 16.84 %. Found: C, 71.94; H,
6.52; N, 17.21 %.
1-(4-nitrophenyl)-2H-imidazole (5).
Following the general procedure using 1-iodo-4-nitrobenzene
(0.493 g, 1.98 mmol), imidazole (0.197 g, 2.89 mmol),
potassium carbonate (0.384 g, 2.78 mmol) and Cu(II)-NaY
(0.298 g) at 155 °C provided
1.08 mmol). H NMR (300 MHz, CDCl3): = 7.30 (broad s, 1H,
CDCl3):
 = 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), 68.40
(O-CH2), 115.39 (CH phenyl), 118.67 (CH imidazolium), 123.09
(CH phenyl), 129.97 (CH imidazolium), 130.47 (N-C phenyl),
5
with a yield of 54 % (0.204 g,
1

max/cm-1

135.79 (CH imidazolium), 158.48 (C-O-CH2 phenyl).
3118 (C-H aromatic), 2921 and 2851 (C-H aliphatic), 1520 (C=C
aromatic), 1243 (C-O aromatic). UV/Vis (CH2Cl2): max (
L.mol-1.cm-1)
241 nm (15000). Elemental analysis for
N-CH- CH-N), 7.39 (t, 1H, J = 1.32 Hz, N-CH-CH-N), 7.60 and
8.40 (AA’ and BB’, 2*2H, J = 9.06 Hz, CH phenyl), 8.03 (broad s,


1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
 = 117.61 (CH
=
imidazole), 121.02 (CH phenyl), 125.71 (CH phenyl), 131.63 (CH
imidazole), 135.37 (CH imidazole), 141.93 (N-C phenyl), 146.27
(C- NO2).
C21H32N2O, Calculed: C, 76.78; H, 9.82; N, 8.53%. Found: C,
76.96; H, 10.58; N, 8.57%.
1-phenyl-2H-imidazole (2).

max/cm-1 3103 (C-H aromatic), 1599 (C=C aromatic),
1510 and 1339 (NO2). UV/Vis (CH2Cl2): max
(
L.mol-1.cm-1) =
Following the general procedure using bromobenzene (0.494
g, 3.15 mmol), imidazole (0.277 g, 4.07 mmol), potassium
carbonate (0.538 g, 3.89 mmol) and Cu(II)-NaY (0.326 g) at 160
301 nm (11800), 227 nm (8900). Elemental analysis for
C9H7N3O2, Calculed: C, 57.14; H, 3.73; N, 22.21 %. Found: C,
57.53; H, 3.72; N, 21.98 %.
1
°C provided
2
with a yield of 54 % (0.245 g, 1.70 mmol). H
General procedure for the formation of imidazolium.
NMR (300 MHz, CDCl3):

= 7.22 (t, 1H, J = 1.11 Hz, N-CH-CH-
N), 7.29 (t, 1H, J = 1.35 Hz, N-CH-CH-N), 7.35-7.41 (m, 3H, CH A mixture of imidazole compound and 1-bromododecane was
phenyl), 7.46-7.53 (m, 2H, CH phenyl), 7.89 (s, 1H, N-CH-N). 13
heated with a microwave oven for 140 minutes at 110 °C in
NMR (75 MHz, CDCl3): = 118.23 (CH imidazole), 121.49 (CH sealed vessel. The corresponding imidazolium salt was purified
phenyl), 127.50 (CH imidazole), 129.86 (CH phenyl), 130.22 (CH by flash chromatography (silica gel, dichloromethane to
imidazole), 135.52 (CH imidazole), 137.32 (N-C phenyl). dichloromethane/methanol: 95/5) or by column
C


max/cm-1 3054 (C-H aromatic), 1509 (C=C aromatic). UV/Vis chromatography (silica gel, dichloromethane/methanol: 95/5)
(CH2Cl2): max
(
L.mol-1.cm-1) = 237 nm (9200). Elemental and by crystallization (dichloromethane/diethyl ether) to
.
analysis for C9H8N2 0.25H2O, Calculed: C, 72.71; H, 5.76; N, afford product.
3-dodecyl-1-(4-(dodecyloxy)phenyl)-2H-imidazol-3-ium
18.84 %. Found: C, 72.77; H, 5.72; N, 18.84 %.
1-p-tolyl-2H-imidazole (3).
bromide (1Br).
Following the general procedure using 1-bromo-4-
methylbenzene (2.489 g, 14.55 mmol), imidazole (1.392 g,
20.45 mmol), potassium carbonate (3.132 g, 22.66 mmol) and
Following the general procedure using
1 (0.706 g, 2.15 mmol)
and 1-bromododecane (1.865 g, 7.48 mmol) provided 1Br with
a yield of 85 % (1.057 g, 1.83 mmol). 1H NMR (300 MHz, CDCl3):
Cu(II)-NaY (1.766 g) at 180 °C provided
3
with a yield of 56 %
(1.320 g, 8.34 mmol). H NMR (300 MHz, CDCl3): = 2.17 (s,
3H, C- CH3 phenyl), 6.97-7.10 (broad m, 6H, CH phenyl and N-
CH-CH-N), 7.26 (s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):

= 0.89 (t, 6H, J = 6.06 Hz, CH3 aliphatic chain), 1.26-1.38
1

(broad m, 36H, CH2 aliphatic chain and O-CH2-CH2-CH2 and N-
CH2-CH2-CH2), 1.81 (q, 2H, J = 6.60 Hz, O-CH2-CH2), 2.00 (qui,
2H, J = 7.14 Hz, N-CH2-CH2), 4.00 (t, 2H, J = 6.60 Hz, O-CH2),
4.59 (t, 2H, J = 7.14 Hz, N-CH2), 7.06 and 7.69 (AA’ and BB’,
2*2H, J = 9.06 Hz, CH phenyl), 7.33 (s, 1H, N-CH-CH-N), 7.46 (s,
1H, N-CH-CH-N), 11.12 (s, 1H, N-CH-N). 13C NMR (75 MHz,

=
20.23 (C-CH3 phenyl), 117.59 (CH imidazole), 120.57 (CH
phenyl), 129.53 (CH imidazole), 129.68 (CH phenyl), 134.29 (C-
CH3 phenyl), 134.86 (CH aromatic), 136.65 (N-C phenyl).
This journal is © The Royal Society of Chemistry 20xx
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New Journal of Chemistry
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ARTICLE
CDCl3):
Journal Name

= 14.04 (C-CH3 aliphatic), 22.61, 25.91, 26.24, 29.01, phenyl), 7.02 (t, 1H, J = 7.68 Hz, CH phenyl), 7.30 (d, 1H, J =
View Article Online
DOI: 10.1039/C8NJ01609G
29.25 ,29.27, 29.31, 29.33, 29.46, 29.50, 29.54, 29.56, 29.59, 7.68 Hz, CH phenyl), 7.36 (s, 1H, CH phenyl), 7.69 (s, 1H, N-CH-
30.37, 31.84 (CH2 aliphatic), 50.41 (N-CH2), 68.60 (O-CH2), CH-N), 7.76 (s, 1H, N-CH-CH-N), 10.54 (s, 1H, N- CH-N). 13C
115.98 (CH phenyl), 120.63 (CH imidazolium), 122.46 (CH NMR (75 MHz, CDCl3):
imidazolium), 123.23 (CH phenyl), 127.18 (N-C phenyl), 135.87 phenyl), 21.67, 35.31, 28.12, 28.32, 28.45, 28.55, 28.61, 29.55,
(CH imidazolium), 160.34 (C-O phenyl).
max/cm-1 3050 (C-H 30.89 (CH2 aliphatic), 49.39 (N-CH2), 117.71, 120.21, 121.21,
aromatic), 2920 and 2849 (C-H aliphatic), 1514 (C=C aromatic), 122.81, 129.20, 129.76 (CH phenyl and imidazium), 133.49 (C-
1242 (C-O). UV/Vis (CH2Cl2): max (
L.mol-1.cm-1) = 254 nm CH3 phenyl), 134.27 (CH phenyl or imidazium), 139.95 (N-C
(11500). Elemental analysis for C33H57BrN2O, Cacld: C, 68.61; H, phenyl). IR
max/cm-1 3075 (C-H aromatic), 2851 (C-H aliphatic),
1557 (C=C aromatic). UV/Vis (CH2Cl2): max
L.mol-1.cm-1) =
 = 13.15 (CH3 aliphatic), 20.31 (C-CH3




9.94; N, 4.85 %. Found: C, 68.60; H, 9.98; N, 4.87 %.
(
3-dodecyl-1-phenyl-2H-imidazol-3-ium bromide (2Br).
231 nm (7900). Elemental analysis for, Caculed C22H35BrN2: C,
64.85; H, 8.66; N, 6.88%. Found: C, 64.85; H, 8.91; N, 6.70 %.
3-dodecyl-1-(4-nitrophenyl)-2H-imidazol-3-ium bromide (5Br).
Following the general procedure using
2 (0.496 g, 3.44 mmol)
and 1-bromododecane (1.538 g, 6.17 mmol) provided 2Br with
a yield of 85 % (1.151 g, 2.93 mmol). 1H NMR (300 MHz, CDCl3): Following the general procedure using
5
(0.556 g, 2.94 mmol)
= 0.84 (t, 3H, J = 7.14 Hz, CH3 aliphatic chain), 1.14-1.31 and 1-bromododecane (1.110 g, 4.46 mmol) provided 5Br with
(broad m, 18H, CH2 aliphatic chain and N-CH2-CH2-CH2), 1.96 a yield of 60 % (0.773 g, 1.76 mmol). 1H NMR (300 MHz, CDCl3):
(q, 2H, J = 7.41 Hz, N-CH2-CH2), 4.54 (t, 2H, J = 7.41 Hz, N-CH2), =0.87 (t, 3H, J = 7.14 Hz, CH3 aliphatic chain), 1.24-1.37


7.43-7.55 (m, 3H, CH phenyl), 7.71 (s, 1H, N-CH-CH-N), 7.77- (broad m, 18H, CH2 aliphatic chain and N-CH2-CH2-CH2), 2.03
7.81 (m, 2H, CH phenyl), 7.87 (s, 1H, N-CH-CH-N), 10.95 (s, 1H, (q, 2H, J = 7.41 Hz, N-CH2-CH2), 4.56 (t, 2H, J = 7.41 Hz, N-CH2),
N-CH-N). 13C NMR (75 MHz, CDCl3):

= 13.97 (CH3 aliphatic), 7.66 (s, 1H, N-CH-CH-N), 8.20 (broad s, 1H, N-CH-CH-N), 8.30
22.53, 26.18, 28.95, 29.19, 29.28, 29.40, 29.46, 30.31, 31.76 and 8.42 (AA’ and BB’, 2*2H, J = 9.60 Hz, CH phenyl), 11.41
(CH2 aliphatic), 50.42 (N-CH2), 120.73 (CH imidazolium), (broad s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
= 14.03 (CH3

121.69 (CH phenyl), 123.05 (CH phenyl), 130.06 (CH phenyl), aliphatic), 22.59, 26.27, 28.97, 29.25, 29.33, 29.44, 29.52,
130.45 (CH imidazolium), 134.38 (N-C phenyl), 135.77 (C-H 30.18, 31.82 (CH2 aliphatic), 50.88 (N-CH2), 121.07 (CH
imidazolium). IR:

max/cm-1 3054 (C-H aromatic), 2930 and imidazolium), 122.99 (CH phenyl), 123.38 (CH imidazolium),
2856 (C-H aliphatic), 1550 (C=C aromatic). UV/Vis (CH2Cl2): max 125.88 (CH phenyl), 136.59 (CH imidazolium), 138.70 (N-C
(

L.mol-1.cm-1) = 229 nm (10500). Elemental analysis for phenyl), 148.09 (C-NO2). IR

max/cm-1 3050 (C-H aromatic),
.
C21H33BrN2 0.12H2O, Calculed: C, 63.76; H, 8.47; N, 7.08 %. 2921 and 2851 (C-H aliphatic), 1599 (C=C aromatic), 1525 and
Found: C, 63.55; H, 8.29; N, 7.14 %.
1342 (NO2). UV/Vis (CH2Cl2): max (
L.mol-1.cm-1) = 268 nm
3-dodecyl-1-p-tolyl-2H-imidazol-3-ium bromide (3Br).
(14100). Elemental analysis for C21H32BrN3O2, Calculed: C,
57.53; H, 7.36; N, 9.58 %. Found: C, 57.29; H, 7.32; N, 9.65 %.
General procedure for metathesis in water – anion exchange.
Following the general procedure using
3 (0.620 g, 3.92 mmol)
and 1-bromododecane (1.486 g, 5.96 mmol) provided 3Br with
a yield of 94 % (1.505 g, 3.69 mmol). 1H NMR (300 MHz,
A
mixture of imidazolium bromide dissolved in
CDCl3):
 = 0.53 (t, 3H, J = 6.84 Hz, CH3 aliphatic chain), 0.90-
dichloromethane and a mixture of the corresponding salt
dissolved in water were stirred together for 48 hours. The
organic layer was separated off, the aqueous layer was washed
with dichloromethane. The organic layers were collected and
dried over calcium chloride. The corresponding imidazolium
salt was purified by flash chromatography (silica gel,
dichloromethane to dichloromethane/methanol: 95/5) and by
crystallization (dichloromethane/diethyl ether) to afford
product.
1.02 (broad m, 18H, CH2 aliphatic chain and N-CH2-CH2-CH2),
1.67-1.69 (m, 2H, N-CH2-CH2), 2.05 (s, 3H, C-CH3 phenyl), 4.27
(t, 2H, J = 7.14 Hz, N-CH2), 6.97 and 7.43 (AA’ and BB’, 2*2H, J =
8.52 Hz, CH phenyl), 7.70 (t, 1H, J = 1.65 Hz, N-CH-CH-N), 7.78
(t, 1H, J = 1.92 Hz, N-CH-CH-N), 10.58 (s, 1H, N-CH-N). 13C NMR
(75 MHz, CDCl3):
 = 13.19 (CH3 aliphatic), 20.21 (C-CH3
phenyl), 21.72, 25.38, 28.18, 28.37, 28.51, 28.61, 28.65, 28.67,
29.60, 30.94 (CH2 aliphatic), 49.41 (N-CH2), 120.27 (CH
imidazolium), 120.58 (CH phenyl), 122.79 (CH imidazolium),
129.98 (CH phenyl), 131.31 (C-CH3 phenyl), 134.25 (CH
3-dodecyl-1-(4-(dodecyloxy)phenyl)-2H-imidazol-3-ium
tetrafluoroborate (1BF4).
imidazolium), 139.31 (N-C phenyl).
aromatic), 2919 and 2852 (C-H aliphatic), 1566 (C=C aromatic).
UV/Vis (CH2Cl2): max
L.mol-1.cm-1) = 240 nm (10300).

max/cm-1 3049 (C-H
Following the general procedure using 1Br (0.303 g, 0.52 mmol)
and potassium tetrafluoroborate (0.279 g, 2.22 mmol)
provided 1BF4 with a yield of 60 % (0.183 g, 0.31 mmol). 1H
(

Elemental analysis for C22H35BrN2, Calculed: C, 64.85; H, 8.66;
N, 6.88 %. Found: C, 64.95; H, 8.95; N, 6.79 %.
3-dodecyl-1-m-tolyl-2H-imidazol-3-ium bromide (4Br).
NMR (300 MHz, CDCl3):
 = 0.85-0.90 (m, 6H, CH3 aliphatic
chain), 1.23-1.45 (broad m, 36H, CH2 aliphatic chain and O-
CH2-CH2-CH2 and N-CH2-CH2-CH2), 1.78 (q, 2H, J = 6.57 Hz, O-
CH2-CH2), 1.88-1.90 (m, 2H, N-CH2-CH2), 3.96 (t, 2H, J = 6.57 Hz,
O-CH2), 4.31 (t, 2H, J = 7.41 Hz, N-CH2), 6.99 (d, 2H, J = 9.06 Hz,
CH phenyl), 7.51 (d, 3H, J = 8,76 Hz, CH phenyl and N-CH-CH-
N), 7.59 (s, 1H, N-CH-CH-N), 9.10 (s, 1H, N- CH-N). 13C NMR (75
Following the general procedure using
4 (0.631 g, 3.99 mmol)
and 1-bromododecane (1.476 g, 5.92 mmol) provided 4Br with
a yield of 90 % (1.469 g, 3.61 mmol). 1H NMR (300 MHz, CDCl3):

= 0.50 (broad t, 3H, J = 6.87 Hz, CH3 aliphatic chain), 0.87-
0.99 (broad m, 18H, CH2 aliphatic chain and N-CH2-CH2-CH2),
1.66 (broad s, 2H, N-CH2-CH2), 2.06 (s, 3H, C-CH3 phenyl), 4.24
(broad t, 2H, J = 6.60 Hz ,N- CH2), 6.90 (d, 1H, J = 7.11 Hz, CH
MHz, CDCl3):
 = 14.05 (CH3 aliphatic), 22.63, 25.94, 26.21,
28.97, 29.06, 29.30, 29.36, 29.49, 29.54, 29.57, 29.59, 29.62,
10 | J. Name., 2012, 00, 1-3
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ARTICLE
30.15, 31.86 (CH2 aliphatic), 50.44 (N-CH2), 68.60 (O-CH2), aliphatic chain), 1.24-1.32 (broad m, 18H, CH2 aliphatic chain
View Article Online
DOI: 10.1039/C8NJ01609G
115.95 (CH phenyl), 121.51 (CH imidazolium), 122.99 (CH and N-CH2-CH2-CH2), 1.91 (broad s, 2H, N-CH2-CH2), 4.27 (t, 2H,
imidazolium), 123.39 (CH phenyl), 127.22 (N-C phenyl), 134.10 J = 7.41 Hz, N-CH2), 7.50-7.54 (m, 6H, CH phenyl and N-CH-CH-
(CH imidazolium), 160.46 (C-O phenyl). IR
aromatic), 2921 and 2852 (C-H aliphatic), 1516 (C=C aromatic), NMR (75 MHz, CDCl3):
1259 (C-O), 1068 (BF4 ). UV/Vis (CH2Cl2): max (

max/cm-1 3082 (C-H N), 7.61 (broad s, 1H, N-CH-CH-N), 8.86 (s, 1H, N-CH-N). 13C

= 14.04 (CH3 aliphatic), 22.62, 26.17,
L.mol-1.cm-1) = 28.90, 29.27, 29.31, 29.46, 29.55, 29.99, 31.84 (CH2 aliphatic),
-
257 nm (10800). Elemental analysis for C33H57BF4N2O, 50.61 (N-CH2), 121.54 (CH phenyl or imidazolium), 122.04 (CH
Calculed: C, 67.80; H, 9.83; N, 4.79 %. Found: C, 68.02; H, phenyl), 123.26 (CH phenyl or imidazolium), 130.46 (CH phenyl
10.59; N, 4.67 %.
3-dodecyl-1-(4-(dodecyloxy)phenyl)-2H-imidazol-3-ium
hexafluorophosphate (1PF6).
or imidazolium), 130.54 (CH phenyl), 133.66 (CH phenyl or
imidazolium), 134.38 (N-C phenyl). IR
max/cm-1 3169 (CH
aromatic), 2920 and 2852 (CH aliphatic), 1553 (C=C aromatic),

830 (PF6 ). UV/Vis (CH2Cl2): max (
L.mol-1.cm-1) = 231 nm
-
Following the general procedure using 1Br (0.300 g, 0.52 mmol)
and potassium hexafluorophosphate (0.257 g, 1.39 mmol)
provided 1PF6 with a yield of 95 % (0.316 g, 0.49 mmol). 1H
(8200). Elemental analysis for C21H33F6N2P, Calculed: C, 55.02;
H, 7.26; N, 6.11 %. Found: C, 54.99; H, 7.10; N, 5.92 %.
3-dodecyl-1-p-tolyl-2H-imidazol-3-ium tetrafluoroborate (3BF4).
NMR (300 MHz, CDCl3):
 = 0.85-0.89 (m, 6H, CH3 aliphatic
Following the general procedure using 3Br (0.336 g, 0.82 mmol)
and potassium tetrafluoroborate (0.740 g, 5.87 mmol)
provided 3BF4 with a yield of 80 % (0.274 g, 0.66 mmol). 1H
chain), 1.24-1.44 (broad m, 38H, CH2 aliphatic chain and O-
CH2-CH2-CH2 and N-CH2-CH2-CH2), 1.76-1.81 (m, 2H, O-CH2-
CH2), 1.90 (broad s, 2H, N-CH2-CH2), 3.96 (t, 2H, J = 6.3 Hz, O-
CH2), 4.26 (broad s, 2H, N-CH2), 7.00 (d, 2H, J = 8.79 Hz, CH
phenyl), 7.45-7.56 (m, 4H, CH phenyl and N-CH-CH-N), 8.96
NMR (300 MHz, CDCl3):
 = 0.86 (t, 3H, J = 6.84 Hz, CH3
aliphatic chain), 1.22-1.30 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.91 (q, 2H, J = 6.84 Hz, N-CH2-CH2), 2.37
(s, 3H, C-CH3 phenyl), 4.32 (t, 2H, J = 7.41 Hz, N-CH2), 7.30 and
7.49 (AA’ and BB’, 2*2H, J = 8.52 Hz, CH phenyl), 7.59 (t, 1H, J =
1.65 Hz, N- CH-CH-N), 7.69 (t, 1H, J = 1.65 Hz, N-CH-CH-N), 9.17
(broad s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
 = 14.03 (CH3
aliphatic), 22.62, 25.93, 26.14, 28.90, 29.05, 29.28, 29.30,
29.34, 29.46, 29.56, 29.59, 29.62, 30.02, 31.85 (CH2 aliphatic),
50.47 (N-CH2), 68.60 (O-CH2), 115.97 (CH phenyl), 121.75 (CH
imidazolium), 122.99 (CH imidazolium), 123.46 (CH phenyl),
127.13 (N-C phenyl), 133.77 (CH imidazolium), 160.55 (C-O
(s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
 = 14.00 (CH3
aliphatic), 20.96 (C-CH3 phenyl), 22.57, 26.15, 28.93, 29.23,
29.32, 29.44, 29.51, 29.52, 30.13, 31.80 (CH2 aliphatic), 50.42
(N-CH2), 121.35 (CH imidazolium), 121.56 (CH phenyl), 123.26
(CH imidazolium), 130.91 (CH phenyl), 132.06 (C-CH3 phenyl),

max/cm-1 3118 (C-H aromatic), 2919 and 2852 (C-H
aliphatic), 1516 (C=C aromatic), 1259 (C-O), 823 (PF6-). UV/Vis
(CH2Cl2): max
(
L.mol-1.cm-1) = 255 nm (9900). Elemental
133.90 (CH imidazolium), 140.58 (N-C phenyl). IR
3055 (C-H aromatic), 2930 and 2857 (CH aliphatic), 1551 (C=C

max/cm-1
analysis for C33H57F6N2OP, Calculed: C, 61.06; H, 8.96; N, 4.32
%. Found: C, 61.04; H, 9.11; N, 4.35 %.
3-dodecyl-1-phenyl-2H-imidazol-3-ium tetrafluoroborate (2BF4).
-
aromatic), 1049 (BF4 ). UV/Vis (CH2Cl2): max (
L.mol-1.cm-1) =
237 nm (10000). Elemental analysis for C22H35BF4N2, Calculed:
C, 63.77; H, 8.51; N, 6.76 %. Found: C, 63.60; H, 8.73; N, 6.84
%.
Following the general procedure using 2Br (0.306 g, 0.78 mmol)
and potassium tetrafluoroborate (0.340 g, 2.70 mmol)
provided 2BF4 with a yield of 57 % (0.177 g, 0.44 mmol). 1H
3-dodecyl-1-p-tolyl-2H-imidazol-3-ium hexafluorophosphate (3PF6).
NMR (300 MHz, CDCl3):
 = 0.87 (t, 3H, J = 6.42 Hz, CH3
Following the general procedure using 3Br (0.321 g, 0.79 mmol)
aliphatic chain), 1.23-1.31 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.89-1.94 (broad m, 2H, N-CH2-CH2), 4.33
(t, 2H, J = 7.41 Hz, N-CH2), 7.48-7.64 (m, 6H, CH phenyl and N-
CH-CH-N), 7.70 (t, 1H, J = 1.62 Hz, N-CH-CH-N), 9.21 (s, 1H, N-
and potassium hexafluorophosphate (0.933 g, 5.07 mmol)
1
provided 3PF6 with a yield of 91 % (0.337 g, 0.71 mmol). H
NMR (300 MHz, CDCl3):
 = 0.86 (t, 3H, J = 6.84 Hz, CH3
CH-N). 13C NMR (75 MHz, CDCl3):
 = 14.04 (CH3 aliphatic),
aliphatic chain), 1.23-1.32 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.91 (broad s, 2H, N-CH2-CH2), 2.38 (C-CH3
phenyl), 4.27 (t, 2H, J = 7.41 Hz, N- CH2), 7.32 and 7.44 (AA’
and BB’, 2*2H, J = 8.22 Hz, CH phenyl), 7.52 (s, 1H, N-CH-CH-
N), 7.61 (s, 1H, N-CH-CH-N), 8.90 (s, 1H, N-CH-N). 13C NMR (75
22.61, 26.19, 28.95, 29.27, 29.35, 29.48, 29.54, 29.55, 30.13,
31.84 (CH2 aliphatic), 50.55 (N-CH2), 121.36 (CH phenyl or
imidazolium), 121.88 (CH phenyl), 123.32 (CH phenyl or
imidazolium), 130.28 (CH phenyl or imidazolium), 130.51 (CH
phenyl), 134.20 (CH phenyl or imidazolium), 134.45 (N-C
MHz, CDCl3):
 = 14.00 (CH3 aliphatic), 20.96 (C-CH3 phenyl),
phenyl). IR

max/cm-1 3110 (CH aromatic), 2919 and 2852 (CH
22.58, 26.13, 28.87, 29.24, 29.29, 29.43, 29.51, 29.99, 31.81
(CH2 aliphatic), 50.50 (N-CH2), 121.53 (CH imidazolium), 121.72
(CH phenyl), 123.18 (CH imidazolium), 130.97 (CH phenyl),
131.98 (C-CH3 phenyl), 133.55 (CH imidazolium), 140.81 (N-C
-
aliphatic), 1553 (C=C aromatic), 1027 (BF4 ). UV/Vis (CH2Cl2):
max (
L.mol-1.cm-1) = 230 nm (8800). Elemental analysis for
C21H33BF4N2, Calculed: C, 63.01; H, 8.31; N, 7.00 %. Found: C,
63.08; H, 8.68; N, 6.73 %.
3-dodecyl-1-phenyl-2H-imidazol-3-ium hexafluorophosphate
(2PF6).
phenyl). IR

max/cm-1 3166 (C-H aromatic), 2920 and 2852 (C-H
-
aliphatic), 1559 (C=C aromatic), 809 (PF6 ). UV/Vis (CH2Cl2):
max (
L.mol-1.cm-1) = 237 nm (9400). Elemental analysis for
C22H35F6N2P, Calculed: C, 55.92; H, 7.47; N, 5.93 %. Found: C,
56.06; H, 7.91; N, 5.83 %.
3-dodecyl-1-m-tolyl-2H-imidazol-3-ium tetrafluoroborate (4BF4).
Following the general procedure using 2Br (0.307 g, 0.78 mmol)
and potassium hexafluorophosphate (0.349 g, 1.90 mmol)
provided 2PF6 with a yield of 81 % (0.291 g, 0.63 mmol). 1H
NMR (300 MHz, CDCl3):
 = 0.87 (t, 3H, J = 6.33 Hz, CH3
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J. Name., 2013, 00, 1-3 | 11
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New Journal of Chemistry
Page 12 of 13
ARTICLE
Journal Name
Following the general procedure using 4Br (0.336 g, 0.82 mmol) analysis for C21H32BF4N3O2, Calculed: C, 56.64; H, V7ie.3w4A;rtiNcle, O9n.l4in4e
DOI: 10.1039/C8NJ01609G
and potassium tetrafluoroborate (0.711 g, 5.64 mmol) %. Found: C, 56.71; H, 7.38; N, 9.40 %.
provided 4BF4 with a yield of 77 % (0.262 g, 0.63 mmol). 1H
3-dodecyl-1-(4-nitrophenyl)-2H-imidazol-3-ium
hexafluorophosphate (5PF6).
NMR (300 MHz, CDCl3):
 = 0.86 (t, 3H, J = 7.11 Hz, CH3
aliphatic chain), 1.22-1.30 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.89-1.93 (m, 2H, N-CH2-CH2), 2.40 (s, 3H,
C-CH3 phenyl), 4.32 (t, 2H, J = 7.41 Hz, N-CH2), 7.29-7.44 (m,
4H, CH phenyl), 7.60 (t, 2H, J = 1.92 Hz, N-CH-CH-N), 7.71 (t,
1H, J = 1.92 Hz, N- CH-CH-N), 9.19 (s, 1H, N-CH-N). 13C NMR (75
Following the general procedure using 5Br (0.303 g, 0.69 mmol)
and potassium hexafluorophosphate (0.335 g, 1.82 mmol)
provided 5PF6 with a yield of 95 % (0.332 g, 0.66 mmol). 1H
NMR (300 MHz, CDCl3):
 = 0.84 (t, 3H, J = 6.57 Hz, CH3
aliphatic chain), 1.22-1.33 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.93-1.95 (broad m, 2H, N-CH2-CH2), 4.29
(t, 2H, J = 7.41 Hz, N-CH2), 7.57 (s, 1H, N-CH-CH-N), 7.82 (d, 3H,
J = 9.03 Hz, CH phenyl and N-CH-CH-N), 8.29 (d, 2H, J = 9.06 Hz,
MHz, CDCl3):
 = 14.01 (CH3 aliphatic), 21.09 (C-CH3 phenyl),
22.58, 26.13, 28.92, 29.23, 29.31, 29.44, 29.51, 30.12, 31.80
(CH2 aliphatic), 50.45 (N-CH2), 118.68, 121.32, 122.30, 123.31,
130.17, 130.94, 133.97 (CH phenyl and imidazolium), 134.33
CH phenyl), 8.99 (s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
 =
(C-CH3 phenyl), 141.08 (N-C phenyl). IR
aromatic), 2929 and 2856 (C-H aliphatic), 1554 (C=C aromatic),

max/cm-1 3055 (C-H
13.91 (CH3 aliphatic), 22.50, 26.09, 28.80, 29.17, 29.23, 29.38,
29.46, 29.63, 31.73 (CH2 aliphatic), 50.80 (N-CH2), 121.39 (CH
imidazolium), 123.13 (CH phenyl), 123.65 (CH imidazolium),
125.64 (CH phenyl), 134.11 (CH imidazolium), 138.81 (N-C
-
1266 (C-N), 1050 (BF4 ). UV/Vis (CH2Cl2): max (
L.mol-1.cm-1) =
231 nm (8600). Elemental analysis for C22H35BF4N2, Calculed: C,
63.77; H, 8.51; N, 6.76 %. Found: C, 63.73; H, 8.75; N, 6.83 %.
3-dodecyl-1-m-tolyl-2H-imidazol-3-ium hexafluorophosphate
phenyl), 148.10 (C-NO2 phenyl). IR
aromatic), 2920 and 2852 (C-H aliphatic), 1557 (C=C aromatic),

max/cm-1 3123 (C-H
-
1526 and 1354 (NO2), 829 (PF6 ). UV/Vis (CH2Cl2): max
262 nm (14100). Elemental analysis for
(
L.mol-
(4PF6).
Following the general procedure using 4Br (0.355 g, 0.87 mmol) 1.cm-1)
=
and potassium hexafluorophosphate (0.989 g, 5.37 mmol) C21H32F6N3O2P, Calculed: C, 50.10; H, 6.41; N, 8.35 %.
provided 4BF4 with a yield of 92 % (0.378 g, 0.80 mmol). 1H Found: C, 50.26; H, 6.56; N, 8.29 %.
NMR (300 MHz, CDCl3):
 = 0.86 (t, 3H, J = 6.60 Hz, CH3
aliphatic chain), 1.23-1.29 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.91 (broad s, 2H, N-CH2-CH2), 2.40 (s, 3H,
C-CH3 phenyl), 4.28 (t, 2H, J = 7.38 Hz, N-CH2), 7.29-7.42 (m,
4H, CH phenyl), 7.52 (s, 1H, N-CH-CH-N), 7.64 (s, 1H, N-CH-CH-
Conflicts of interest
There are no conflicts to declare.
N), 8.93 (s, 1H, N-CH-N). 13C NMR (75 MHz, CDCl3):
 = 13.99
(CH3 aliphatic), 21.02 (C-CH3 phenyl), 22.57, 26.11, 28.85,
29.23, 29.27, 29.42, 29.51, 29.97, 31.80 (CH2 aliphatic), 50.51
(N-CH2), 118.75, 121.45, 122.44, 123.20, 130.18, 131.08,
133.60 (CH phenyl and imidazolium), 134.25 (C-CH3 phenyl),
Acknowledgements
We are especially grateful to Dr. J. Harrowfield for the critical
evaluation of this manuscript. This work was supported by
OUTSMART A.N.R-15-CE39-0004 (Matthieu L’HER PhD Grant)
and ANR-11-LABX-0058_NIE within the Investissement
d’Avenir program ANR-10-IDEX-0002-02.
141.16 (N-C phenyl). IR
and 2857 (C-H aliphatic), 1552 (C=C aromatic), 846 (PF6 ).

max/cm-1 3055 (C-H aromatic), 2929
-
UV/Vis (CH2Cl2): max
(
L.mol-1.cm-1) = 231 nm (8400).
Elemental analysis for C22H35F6N2P, Calculed: C, 55.92; H, 7.47;
N, 5.93 %. Found: C, 55.75; H, 7.65; N, 6.02 %.
3-dodecyl-1-(4-nitrophenyl)-2H-imidazol-3-ium tetrafluoroborate
(5BF4).
Notes and references
1.
P. Wasserscheid and T. Welton, Ionic liquids in synthesis,
Wiley-VCH, Weinheim, 2nd, completely rev. and enl. edn.,
2008.
Following the general procedure using 5Br (0.303 g, 0.69 mmol)
and potassium tetrafluoroborate (0.384 g, 3.05 mmol)
provided 5BF4 with a yield of 50 % (0.153 g, 0.34 mmol). 1H
2.
3.
4.
5.
6.
7.
H. Ohno, Electrochemical aspects of ionic liquids, John
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NMR (300 MHz, CDCl3):
 = 0.86 (t, 3H, J = 6.87 Hz, CH3
aliphatic chain), 1.23-1.34 (broad m, 18H, CH2 aliphatic chain
and N-CH2-CH2-CH2), 1.93-1.98 (broad m, 2H, N-CH2-CH2), 4.35
(t, 2H, J = 7.41 Hz, N-CH2), 7.61 (t, 1H, J = 1.92 Hz, CH phenyl or
N-CH-CH-N), 7.90-7.95 (m, 3H, CH phenyl and N-CH-CH-N),
8.32 (d, 2H, J = 9.03 Hz, CH phenyl), 9.33 (s, 1H, N-CH-N). 13C
NMR (75 MHz, CDCl3):
 = 14.04 (CH3 aliphatic), 22.62, 26.24,
28.95, 29.27, 29.36, 29.49, 29.56, 29.93, 31.85 (CH2 aliphatic),
50.92 (N-CH2), 121.43 (CH imidazolium), 123.11 (CH phenyl),
123.74 (CH imidazolium), 125.82 (CH phenyl), 134.81 (CH
imidazolium), 138.87 (N-C phenyl), 148.20 (C-NO2 phenyl). IR

max/cm-1 3120 (C-H aromatic), 2916 and 2851 (C-H aliphatic),
8.
M. Taillefer and D. Ma, Amination and formation of sp2 C-
N bonds, Springer, Berlin ; London, 2013.
-
1555 (C=C aromatic), 1523 and 1341 (NO2), 1021 (BF4 ). UV/Vis
(CH2Cl2): max (
L.mol-1.cm-1) = 264 nm (14700). Elemental
12 | J. Name., 2012, 00, 1-3
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New Journal of Chemistry
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