Synthesis of guanidinium-sulfonimide ion pairs: Towards novel ionic liquid crystals

Article abstract of DOI:10.3762/bjoc.9.121

The recently introduced concept of ionic liquid crystals (ILCs) with complementary ion pairs, consisting of both, mesogenic cation and anion, was extended from guanidinium sulfonates to guanidinium sulfonimides. In this preliminary study, the synthesis and mesomorphic properties of selected derivatives were described, which provide the first example of an ILC with the sulfonimide anion directly attached to the mesogenic unit.

Full text of DOI:10.3762/bjoc.9.121

Synthesis of guanidinium–sulfonimide ion pairs:
towards novel ionic liquid crystals
Martin Butschies, Manuel M. Neidhardt, Markus Mansueto, Sabine Laschat*
and Stefan Tussetschläger
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2013, 9, 1093–1101.
Institut für Organische Chemie, Universität Stuttgart, Pfaffenwalring
55, 70569 Stuttgart, Germany
doi:10.3762/bjoc.9.121
Received: 01 March 2013
Accepted: 21 May 2013
Published: 05 June 2013
Email:
Sabine Laschat* - sabine.laschat@oc.uni-stuttgart.de
* Corresponding author
This article is part of the Thematic Series "Progress in liquid crystal
chemistry II". Dedicated to Professor Baldur Föhlisch on the occasion of
his 80th birthday.
Keywords:
anion exchange; ionic liquid crystals; ion pairs; mesophases;
sulfonimides
Associate Editor: P. J. Skabara
© 2013 Butschies et al; licensee Beilstein-Institut.
License and terms: see end of document.
Abstract
The recently introduced concept of ionic liquid crystals (ILCs) with complementary ion pairs, consisting of both, mesogenic cation
and anion, was extended from guanidinium sulfonates to guanidinium sulfonimides. In this preliminary study, the synthesis and
mesomorphic properties of selected derivatives were described, which provide the first example of an ILC with the sulfonimide
anion directly attached to the mesogenic unit.
Introduction
While ionic liquids, i.e., molten salts composed of either Knight and Shaw [11,12], followed by seminal findings by
organic cation or anion (or both) with melting points far below Seddon and Bruce [13]. Regarding ionic liquids, sulfonimides
100 °C, are extensively used as designer solvents, electrolytes have been used in various ways. Particularly interesting is the
for lithium ion batteries, dye-sensitized solar cells, and the elec- symmetrical bistriflimide anion [14], which leads to desirable
trochemical deposition of metals [1-5], the corresponding ionic properties such as hydrolytic stability, low viscosity or low
liquids with thermotropic liquid-crystalline properties, i.e., melting points in the ionic liquids [1,4,15-19]. By using an
ILCs, are a much younger class of compounds [6-8]. Although elongated perfluoroalkyl chain at the bistriflimide anion in
Heintz was the pioneer, who observed in 1854 melting and combination with short chain-substituted pyrrolidinium cations
clearing transitions upon heating of magnesium myristate MacFarlane was able to induce plastic crystal phases and liquid-
[9,10], he did not recognize this as liquid-crystalline behavior. crystalline phases at room temperature [20]. Ion pairs consisting
The first regular pyridinium ILCs were reported in 1938 by of perfluorosulfonylimide anions and imidazolium cations with
1093

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
short alkyl chains were studied by DesMarteau resulting in
room-temperature ionic liquids [21]. In contrast, ILCs with
bistriflimide anions are much less explored, because the steri-
cally demanding anion often inhibits the formation of a
mesophase [6,22]. Liquid-crystalline phases were found for
viologen salts [23-28], imidazolium ILCs [29-31], pyrroli-
dinium ILCs [32,33] and ionic polymers [34-37]. Sulfonimides,
which are directly bound to a mesogenic group, have not been
described until now. We have recently described the concept of
complementary ion pairs, where guanidinium sulfonate 1 with
both mesogenic cation and anion displayed improved
mesophase stability and increased phase widths as compared to
their counterparts bearing a nonmesogenic spherical halide
counterion [38,39] (Scheme 1).
Scheme 2: Synthesis of the potassium sulfonimides 6a and 6b.
The K+-salts were prepared due to their more convenient isola-
tion as compared to the corresponding protonated compounds.
However, the K+-sulfonimides 6a,b were not used for a direct
methyl transfer towards the synthesis of the desired guani-
dinium–sulfonimide ion pairs in a similar way that the arylsul-
fonic acid methylesters were previously used as methyl transfer
reagents [38], because we wanted to avoid the activation with
dimethyl sulfate reported by DesMarteau [21]. Therefore we
planned an indirect formation of the ion pairs by anion
exchange via salt metathesis. In order to be successful, two
requirements have to be met. First, the solubility of the sulfon-
imide salts 6a,b in the solvent must be sufficient. Second, one
of the products must be insoluble in order to shift the equilib-
rium towards complete conversion. In contrast to the sodium
Scheme 1: Complementary guanidinium sulfonate 1 and
guanidinium–sulfonimide ion pairs 2 and 3.
We were thus interested, whether this concept could be also 4-alkoxyphenylsulfonates both potassium salts 6a,b are soluble
used to generate the corresponding sulfonimide ion pairs 2 and in boiling MeCN, so that both conditions for a successful salt
3 with mesomorphic properties. The results of this preliminary metathesis are fulfilled.
study are discussed below.
The known guanidinium chloride 7∙Cl [42] was treated with
Results and Discussion
MeI in the presence of K2CO3 to afford the N-methylated
The synthesis of guanidinium–sulfonimide ion pairs guanidinium iodide 8∙I (Scheme 3) [38,39].
commenced with the commercially available sulfonyl chloride 4
[38], which was treated with trifluoromethanesulfonamide (5a) However, this intermediate did not allow a salt metathesis,
in the presence of NEt3 following a procedure by Hesemann because the resulting KI is highly soluble in MeCN (and other
and Brunel [40]. Then the fluorinated sulfonimide was organic solvents). Therefore, the intermediate was treated with
converted to the potassium salt 6a after recrystallization from AgNO3 in MeOH. The resulting N-methylated guanidinium
MeOH in 60% yield (Scheme 2).
nitrate was then reacted with 6a or 6b in MeCN to the desired
ion pairs 2a and 2b in 79% and 75% yield, respectively, while
The corresponding nonfluorinated sulfonimide K+-salt 6b was the precipitating KNO3 shifted the salt metathesis to comple-
obtained by deprotonation of methanesulfonamide (5b) with tion (Scheme 3).
NaH followed by treatment with sulfonyl chloride 4 according
to a method by Dick and Townsend [41]. Analogous deprotona- The good solubility of the K+-sulfonimide salts 6a,b in MeCN
tion with KOH yielded 6b in 71%.
was further used for a salt metathesis towards the N-protonated
1094

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
N-Methylated guanidinium sulfonimides 2a,b revealed only
isotropic melting at 61 °C and 93 °C, respectively (Table 1,
entries 1 and 2), while N-methylated guanidinium iodide 8∙I
melted at 117 °C (Table 1, entry 3). In comparison, the
N-methylated guanidinium sulfonate 1 displayed a melting tran-
sition at 99 °C in the SmA phase and isotropic clearing at
148 °C (Table 1, entry 8). Thus, while the presence of the
sulfonimide anions in 2a,b indeed led to a decrease of the
melting point as compared to the corresponding iodide 8∙I, the
formation of a smectic mesophase was completely suppressed.
For protonated guanidinium sulfonimides 3a,b again a signifi-
cant decrease of the melting temperature was found (75 °C and
71 °C, respectively, Table 1, entries 4 and 5) as compared to the
protonated guanidinium iodide 7∙I, which melted at 130 °C into
the isotropic phase (Table 1, entry 6). The protonated chloride
7∙Cl showed a melting transition at 121 °C into the SmA phase,
and a clearing transition at 128 °C (Table 1, entry 7) [42].
However, while the trifluoromethyl-substituted sulfonimide 3a
displayed only three crystal-to-crystal transitions at 8, 19 and
37 °C, respectively, besides isotropization at 75 °C, the corres-
ponding methyl-substituted sulfonimide 3b showed two crystal-
to-crystal transitions at 5 °C and 27 °C, respectively, a melting
transition into the smectic A phase at 71 °C and a clearing point
at 87 °C. Thus, sulfonimide-containing ion pair 3b indeed led to
a mesophase albeit with only 16 K phase width as compared to
Scheme 3: Synthesis of guanidinium sulfonimides 2a,b, 3a,b and
iodides 7∙I, 8∙I.
guanidinium–sulfonimide ion pairs 3a,b by heating 7∙Cl with 6a 49 K phase width of the guanidinium sulfonate 1. The DSC
or 6b under reflux. The resulting ion pairs 3a and 3b were traces of 3b are shown in Figure 1.
isolated in 77% and 96% yield, respectively. In comparison the
guanidinium iodide 7∙I was obtained in 94% yield by heating POM observations of 3b upon cooling from the isotropic liquid
7∙Cl with KI in MeCN under reflux (Scheme 3). The mesomor- revealed fan-shaped textures and homeotropic alignment
phic properties of ion pairs 2,3 and guanidinium halides 7∙I, (Figure 2) typical for SmA phases.
7∙Cl, 8∙I were studied by differential scanning calorimetry
(DSC) and polarizing optical microscopy (POM). The results of The mesophase of compound 3b was investigated by X-ray
the DSC experiments are summarized in Table 1.
scattering (WAXS and SAXS) at different temperatures. The
Table 1: Phase-transition temperatures (°C) and enthalpies (kJ mol−1) of guanidinium–sulfonimide ion pairs 2 and 3 and the corresponding guani-
dinium salts 7∙I, 7∙Cl and 8∙Ia.
Entry
Compound
Phase transitions (onset (°C)) and transition enthalpies (given in parentheses) (kJ mol−1) upon
second heating
1
2
3
4
5
6
7
8
2a
2b
8∙I
3a
3b
7∙I
7∙Cl
1
Cr 61 (31.8) Ib
Cr 93 (59.1) I
Cr1 49 (8.4) Cr2 117 (25.8) Ic
Cr1 8 (18.6) Cr2 19 (0.8) Cr3 37 (−44.9) Cr4 75 (48.6) I
Cr1 5 (8.1) Cr2 27 (−54.4) Cr3 71 (73.1) SmA 87 (1.4) I
Cr1 55 (−44.3) Cr2 130 (37.2) I
Cr 121 (29.9) SmA 128 (0.7) Ib,d
Cr1 51 (−5.1) Cr2 99 (61.6) SmA 148 (1.9) Ic
aThe following phases were observed: Cr Crystalline, SmA Smectic A, I Isotropic. Heating rate 10 K min−1. bUpon 1st heating. cData for compounds
8∙I and 1 were taken from [38]. dData for compound 7∙Cl was taken from [42]; heating rate 5 K min−1.
1095

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
Figure 1: DSC traces of compound 3b (heating/cooling rate 10 K min−1).
Figure 2: Compound 3b under crossed polarizers upon cooling from the isotropic melt (200-fold magnification). (a) Homeotropic texture at 80 °C
(cooling rate 10 K min−1); (b) fan-shaped texture at 88 °C (cooling rate 1 K min−1).
XRD experiments revealed diffraction patterns with a single decreases with rising temperatures. To allow a comparison with
diffraction peak and a diffuse halo at 4.7 Å resulting from the the layer spacings of compounds 1 and 7∙Cl, the layer spacing
alkyl chains (Figure 3). These patterns are typical for smectic of 3b was determined at a reduced temperature (Tred =
mesophases and further confirm the assignment of a SmA phase 0.95∙Tiso) by linear extrapolation of the obtained data (Table 2).
based on POM observations.
The obtained value of dred = 32.6 Å (Table 2) is in good agree-
ment with the values determined for salts 7∙Cl (34.0 Å [42]) and
The exact layer spacing at each temperature was determined by 1 (32.2 Å [38]) bearing the same (7∙Cl) or nearly the same
fitting the first-order peak with a Gaussian distribution (N–Me instead of N–H) cation 1. As the layer spacing is much
(Figure 3 and Supporting Information File 1, Table S1) and larger (32.6 Å) compared to the calculated length of the cation
1096

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
Figure 3: (a) WAXS diffraction pattern of 3b at 59.5 °C (vertical magnetic field director); (b) temperature-dependent layer spacing of compound 3b.
and anion (23–24 Å, Table 2), we propose the formation of Experimental
mixed double layers with the charged heads of cation and anion General Information. All reactions were carried out under a
pointing to each other. This packing behavior is in good agree- nitrogen atmosphere with Schlenk-type glassware and the
ment with those reported for guanidinium sulfonate 1 [38].
solvents were dried and distilled under nitrogen prior to use.
Characterization of the compounds was carried out by using the
following instruments. Elemental analyses: Carlo Erba Stru-
mentazione Elemental Analyzer, Modell 1106. NMR: Bruker
Avance 500 (1H, 500 MHz; 13C, 125 MHz). IR: Bruker Vector
22 FTIR spectrometer with MKII golden gate single reflection
diamond ATR system. 1H and 13C NMR spectra were recorded
at room temperature and referenced to TMS (Me4Si
δH = 0.0 ppm, δC = 0.0 ppm) as an internal standard. The
assignment of the resonances was supported by chemical shift
calculations and 2D experiments (COSY and HMBC). MS (EI):
Varian MAT 711 spectrometer. Polarizing optical microscopy:
Olympus BX50 polarizing microscope combined with a Linkam
TP93 central controller. MS (ESI): Bruker Daltonics
microTOF-Q spectrometer. Differential scanning calorimetry
(DSC): Mettler-Toledo DSC 822e (heating/cooling rates were
Table 2: Layer spacings of compounds 1, 7∙Cl and 3b at a common
reduced temperature in comparison to the calculated molecular
lengths.
Compound Tred/[° C] dred/[Å] Lcalc
Lcalc
(cation)/[Å] (anion)/[Å]
3b
83
32.6
34.0
32.2
23.8a
23.9
23.0
22.7a
1.81c
21.0
7∙Clb
1d
122
141
aCalculated using Chem3D Ultra, Cambridgesoft, 2011. bValues were
taken from [42]. cValue was taken from [43]. dValues were taken from
[38].
Conclusion
We have developed a route towards guanidinium–sulfonimide 10 K min−1). X-ray diffraction (WAXS, SAXS regions): Bruker
ion pairs in which both anion and cation contain mesogenic AXS Nanostar C diffractometer employing Ni-filtered Cu Kα
units. The replacement of a spherical halide counterion by a radiation (λ = 1.5418 Å). Melting points: Büchi SMP-20. Water
calamitic sulfonimide anion indeed led to a decrease of the content: Metrohm 831 Coulometric Karl Fischer Titrator,
melting points, the effect being larger for trifluorosulfonimides (generator electrode with a diaphragm), HYDRANAL-
2a and 3a as compared to methylsulfonimides 2b and 3b. It Coulomat AG and HYDRANAL-Coulomat CG solutions were
should be noted that Strassner has recently introduced a used.
different concept to tune melting points in ionic liquids by elec-
tronic effects of the aryl substituent [44,45]. However, the Compounds 4 and 5a,b are commercially available. Full charac-
mesogenic sulfonimide resulted in the formation of a SmA terization of compounds 1 and 8∙I is given in [38], and for com-
mesophase only in the case of 3b, while ion pairs 2a,b and 3a pound 7∙Cl in [42]. For compounds 2b, 3a and 7∙I the following
did not show any liquid-crystalline properties. Thus, the pres- water content was determined by Karl Fischer titration: 0.38%,
ence of mesogenic counterions could not overcome the known 0.36% and 0.13%, respectively (see Supporting Information
tendency of sulfonimides to inhibit mesomorphism.
File 1, Table S2).
1097

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
4-(Dodecyloxy)-N-((trifluoromethyl)sulfonyl)benzenesulfon- 13C NMR (125 MHz, DMSO-d6) δ 13.9 (CH3), 22.0, 25.4, 28.5,
amide, potassium salt (6a): A mixture of trifluoromethanesul- 28.6, 28.7, 28.90, 28.91, 28.94, 31.2 (CH2), 42.6 (SO2CH3),
fonamide (5a) (207 mg, 1.38 mmol) and 4-(dodecyloxy)- 67.5 (OCH2), 113.2 (C-3), 128.0 (C-2), 138.8 (C-1), 159.6
benzenesulfonylchloride (4) (500 mg, 1.39 mmol) was (C-4) ppm; FTIR (ATR) : 3077 (w), 2914 (s), 2849 (m), 1595
dissolved in abs dichloromethane (20 mL). Abs triethylamine (m), 1498 (m), 1473 (m), 1394 (m), 1274 (s), 1248 (s), 1152 (s),
(1 mL, 701 mg, 6.93 mmol) was added and the resulting mix- 1126 (s), 1089 (vs), 972 (m), 831 (s), 808 (s), 721 (s), 679 (m),
ture was heated under reflux for 12 h. After cooling to room 590 (s), 525 (vs) cm−1; ESIMS (m/z): 418 [M]−, 340 [M− −
temperature the solvent was removed in vacuo, the residue was CH3O2S + H], 249 [M− − C12H25]; HRMS–ESI (m/z): [M]−
taken up in ethyl acetate (100 mL), and the hot suspension was calcd for C19H32NO5S2–, 418.1727; found, 418.1728.
filtered. The filtrate was evaporated to dryness and the residue
General procedure for the preparation of
was purified by flash chromatography with ethyl acetate as
eluent. The resulting solid was taken up in methanol (20 mL), pentamethylguanidinium ion pairs (2a,b)
potassium hydroxide (78 mg, 1.39 mmol) was added, and the Potassium carbonate (144 mg, 971 μmol) and methyl iodide
mixture was heated under reflux for 5 min. After cooling to (207 mg, 1.46 mmol) were added to a solution of guanidinium
0 °C product 6a precipitated as a colorless solid. Yield: 425 mg chloride (7∙Cl, 200 mg, 485 μmol) in acetonitrile (20 mL). The
(60%); colorless solid; mp > 300 °C; 1H NMR (500 MHz, resulting mixture was heated to 50 °C for 12 h and then cooled
DMSO-d6) δ 0.85 (t, J = 7.2 Hz, 3H, CH3), 1.17–1.35 (m, 16H, to room temperature, and the solvent was removed in vacuo.
CH2), 1.36–1.43 (m, 2H, CH2), 1.67–1.74 (m, 2H, CH2), 4.01 The residue was taken up in dichloromethane (20 mL) and
(t, J = 6.5 Hz, 2H, OCH2), 6.94–7.00 (m, 2H, 3-H), 7.62–7.68 filtered, and the filtrate was concentrated to dryness. A solution
(m, 2H, 2-H) ppm; 13C NMR (125 MHz, DMSO-d6) δ 13.9 of the residue in methanol (20 mL) was treated with silver
(CH3), 22.1, 25.4, 28.5, 28.68, 28.71, 28.95, 28.98, 29.0 31.3 nitrate (165 mg, 971 μmol) and stirred for 12 h at room
(CH2), 67.7 (OCH2), 113.8 (C-3), 128.1 (C-2), 137.1 (C-1), temperature under the exclusion of light. The solvent was
160.5 (C-4) ppm; FTIR (ATR) : 2917 (m), 2848 (m), 1597 removed under reduced pressure, the residue was taken up in
(m), 1584 (m), 1497 (m), 1467 (m), 1387 (w), 1329 (s), 1284 dichloromethane (20 mL), and the slurry was filtered by using a
(m), 1254 (m), 1232 (m), 1206 (m), 1160 (vs), 1114 (m), 1093 Rotilabo-syringe filter. After concentration of the filtrate to
(s), 1058 (s), 956 (w), 867 (w), 833 (m), 801 (w), 780 (s), 746 dryness, the residue was taken up in acetonitrile (10 mL), and
(s), 718 (w), 683 (m) cm−1; ESIMS (m/z): 472 [M]−, 303 [M− − sulfonimide salt 6a or 6b (509 μmol) was added. The mixture
C12H25]; HRMS–ESI (m/z): [M]− calcd for C19H29F3NO5S2−, was heated under reflux for 5 min, the solvent was removed in
472.1445; found, 472.1427.
vacuo, and the residue was taken up in dichloromethane
(20 mL). After filtration with a Rotilabo-syringe filter the
4-(Dodecyloxy)-N-((methylsulfonyl)benzenesulfonamide, solvent was removed in vacuo, and the crude product was re-
potassium salt (6b): Methanesulfonamide (5b) (277 mg, crystallized from ethyl acetate.
2.91 mmol) was given to a suspension of sodium hydride
(333 mg, 8.31 mmol) in abs DMF (10 mL) and the mixture was N-(4-(Dodecyloxy)phenyl)-N,N’,N’,N”,N”-pentamethyl-
stirred for 1 h. After cooling to 0 °C a solution of 4-(dodecyl- guanidinium ((4-(dodecyloxy)phenyl)sulfonyl)((trifluo-
oxy)benzenesulfonylchloride (4, 1.00 g, 2.77 mmol) in abs THF romethyl)sulfonyl)amide (2a): Yield: 330 mg (79%); color-
(5 mL) was added dropwise and the reaction mixture was less solid; 1H NMR (500 MHz, CDCl3) δ 0.88 (t, J = 6.8 Hz,
warmed to room temperature. After being stirred for 3 days, the 6H, CH3), 1.20–1.38 (m, 32H, CH2), 1.40–1.48 (m, 4H, CH2),
mixture was brought to pH 1 by the addition of concd 1.73–1.82 (m, 4H, OCH2CH2), 2.82, 3.07 (br s, 12H, N[CH3]2),
hydrochloric acid. The solvents were removed in vacuo and the 3.39 (s, 3H, NCH3), 3.94 (t, J = 6.5 Hz, 2H, OCH2), 3.97 (t, J =
residue was taken up in dichloromethane (50 mL). The resulting 6.5 Hz, 2H, OCH2), 6.87–6.95 (m, 2H, 3-H, 3”-H), 6.97–7.02
solution was dried with magnesium sulfate and filtered, and the (m, 2H, 2-H), 7.88–7.92 (m, 2H, 2”-H) ppm; 13C NMR
filtrate was evaporated to dryness. The residue was taken up in (125 MHz, CDCl3) δ 14.1 (CH3), 22.7, 25.98, 26.01, 29.11,
methanol (30 mL) and treated with potassium hydroxide 29.18, 29.36, 29.39, 29.40, 29.57, 29.61, 29.64, 29.67, 31.9
(156 mg, 2.77 mmol) for 5 min. After cooling the mixture to (CH2), 40.2 (NCH3), 40.2, 41.1 (br s, N(CH3)2), 68.3, 68.5
0 °C the product 6b precipitated as a colorless solid. Yield: (OCH2), 114.1 (C-3”), 115.9 (C-3), 123.4 (C-2), 129.3 (C-2”),
901 mg (71%); colorless solid; mp > 300 °C; 1H NMR 134.65, 134.72 (C-1, C-1”), 157.7 (C-4), 162.0 (C-4”), 162.2
(500 MHz, DMSO-d6) δ 0.86 (t, J = 6.8 Hz, 3H, CH3), (C-1’) ppm; 19F NMR (235 MHz, CDCl3) δ −77.0 (CF3) ppm;
1.18–1.35 (m, 16H, CH2), 1.36–1.43 (m, 2H, CH2), 1.66–1.74 FTIR (ATR) : 2918 (s), 2850 (m), 1611 (m), 1597 (m), 1555
(m, 2H, CH2), 2.72 (s, 3H, SO2CH3), 3.98 (t, J = 6.5 Hz, 2H, (m), 1511 (m), 1473 (m), 1410 (m), 1350 (m), 1323 (s), 1288
OCH2), 6.86–6.92 (m, 2H, 3-H), 7.59–7.64 (m, 2H, 2-H) ppm; (m), 1246 (s), 1221 (m), 1173 (vs), 1132 (s), 1093 (s), 1056 (s),
1098

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
999 (s), 897 (m), 837 (m), 797 (m), 720 (w), 687 (m) cm−1; 6.85–6.91 (m, 4H, 3-H, 3”-H), 6.95–7.00 (m, 2H, 2-H),
ESIMS (m/z): 390 [M]+, 222 [M+ − C12H25 + H]; ESIMS (m/z): 7.85–7.90 (m, 2H, 2”-H) ppm; 13C NMR (125 MHz, CDCl3) δ
472 [M]−, 303 [M– − C12H25]; HRMS–ESI (m/z): [M]+ calcd 14.1 (CH3), 22.7, 25.99, 26.04, 29.13, 29.24, 29.36, 29.39,
for C24H44N3O+, 390.3479; found, 390.3456; HRMS–ESI 29.42, 29.57, 29.59, 29.61, 29.64, 29.67, 31.9 (CH2), 40.3
(m/z): [M]− calcd for C19H29F3NO5S2–, 472.1434; found, (N(CH3)2), 66.3, 66.4 (OCH2), 113.9 (C-3”), 115.7 (C-3), 122.3
472.1438; DSC: Cr 61 °C [31.8 kJ mol–1] I.
(C-2), 128.7 (C-2”), 130.2 (C-1), 135.6 (C-1”), 157.0 (C-4),
159.1 (C-4”), 161.6 (C-1’) ppm; 19F NMR (235 MHz, CDCl3) δ
N-(4-(Dodecyloxy)phenyl)-N,N’,N’,N”,N”-pentamethyl- −78.1 (CF3) ppm; FTIR (ATR) : 2917 (s), 2850 (m), 1620
guanidinium ((4-(dodecyloxy)phenyl)sulfonyl)(methylsul- (m), 1595 (m), 1572 (m), 1512 (m), 1474 (m), 1423 (w), 1403
fonyl)amide (2b): Yield: 94 mg (75%); colorless solid; (m), 1335 (s), 1311 (m), 1296 (m), 1257 (m), 1241 (m), 1223
1H NMR (500 MHz, CDCl3) δ 0.88 (t, J = 6.9 Hz, 6H, CH3), (m), 1195 (s), 1163 (s), 1137 (s), 1111 (w), 1091 (m), 1032 (vs),
1.20–1.39 (m, 32H, CH2), 1.39–1.48 (m, 4H, CH2), 1.73–1.81 915 (w), 828 (s), 782 (m), 752 (m), 723 (m), 685 (m), 640 (m),
(m, 4H, OCH2CH2), 2.82, 3.09 (br s, 12H, N[CH3]2), 3.41 (s, 598 (s), 562 (s) cm−1; ESIMS (m/z): 376 [M]+, 331 [M+ −
3H, NCH3), 2.90 (s, 3H, SO2CH3), 3.90–3.97 (m, 4H, OCH2), C2H6N − H]; ESIMS (m/z): 472 [M]−, 303 [M– − C12H25];
6.82–6.87 (m, 2H, 3”-H), 6.89–6.94 (m, 2H, 3-H), 7.00–7.05 HRMS–ESI (m/z): [M]+ calcd for C23H42N3O+, 376.3322;
(m, 2H, 2-H), 7.87–7.92 (m, 2H, 2”-H) ppm; 13C NMR found: 376.3334; HRMS–ESI (m/z): [M]− calcd for
(125 MHz, CDCl3) δ 14.1 (CH3), 22.7, 26.0, 29.19, 29.20, C19H29F3NO5S2–, 472.1434; found, 472.1425; Anal. calcd for
29.35, 29.40, 29.58, 29.64, 29.67, 31.9 (CH2), 40.3 (NCH3), C42H71F3N4O6S2 (849.2): C, 59.41; H, 8.43; N, 6.60; found: C,
40.3, 41.2 (br s, N(CH3)2), 42.2 (SO2CH3), 68.1, 68.4 (OCH2), 59.53; H, 8.36; N, 6.60; DSC: Cr1 8 °C [18.6 kJ mol−1] Cr2
113.6 (C-3”), 115.8 (C-3), 123.4 (C-2), 128.7 (C-2”), 135.0 19 °C [0.8 kJ mol−1] Cr3 37 °C [−44.9 kJ mol−1] Cr4 75 °C
(C-1), 137.8 (C-1”), 157.4 (C-4), 160.7 (C-4”), 162.2 (C-1’) [48.6 kJ mol−1] I.
ppm; FTIR (ATR) : 2919 (s), 2850 (m), 1612 (m), 1552 (m),
1510 (m), 1469 (m), 1403 (m), 1296 (w), 1268 (s), 1241 (s), N-(4-(Dodecyloxy)phenyl)-N’,N’,N”,N”-tetramethylguani-
1177 (m), 1143 (m), 1122 (s), 1086 (s), 1051 (s), 1001 (w), 948 dinium ((4-(dodecyloxy)phenyl)sulfonyl)(methyl-
(w), 897 (w), 837 (m), 801 (m), 721 (s), 653 (s), 587 (vs) cm−1; sulfonyl)amide (3b): Yield: 93 mg (96%); colorless solid;
ESIMS (m/z): 390 [M]+, 222 [M+ − C12H25 + H]; ESIMS (m/z): 1H NMR (500 MHz, CDCl3) δ 0.88 (t, J = 6.9 Hz, 6H, CH3),
418 [M]−, 249 [M− − C12H25]; HRMS–ESI (m/z): [M]+ calcd 1.20–1.39 (m, 32H, CH2), 1.40–1.48 (m, 4H, CH2), 1.72–1.81
for C24H44N3O+, 390.3479; found, 390.3484; HRMS–ESI (m, 4H, OCH2CH2), 2.86–3.08 (m, 12H, N(CH3)2), 2.90 (s, 3H,
(m/z): [M]− calcd for C19H32NO5S2–, 418.1716; found, SO2CH3), 3.92 (t, J = 6.5 Hz, 2H, OCH2), 3.96 (t, J = 6.6 Hz,
418.1791; Anal. calcd for C43H76N4O6S: C, 63.82; H, 9.47; N, 2H, OCH2), 6.83–6.89 (m, 4H, 3-H, 3”-H), 6.96–7.02 (m, 2H,
6.92; found: C, 63.83; H, 9.38; N, 6.94; DSC: Cr 93 °C 2-H), 7.85–7.90 (m, 2H, 2”-H) ppm; 13C NMR (125 MHz,
[59.1 kJ mol–1] I.
CDCl3) δ 14.1 (CH3), 22.7, 26.0, 26.1, 29.16, 29.25, 29.36,
29.40, 29.42, 29.58, 29.59, 29.61, 29.64, 29.67, 31.9 (CH2),
40.4 (N(CH3)2), 42.4 (SO2CH3), 66.2, 66.3 (OCH2), 113.8
(C-3”), 115.6 (C-3), 122.2 (C-2), 128.7 (C-2”), 130.7 (C-1),
General procedure for the preparation of
tetramethylguanidinium ion pairs (3a,b)
A mixture of guanidinium chloride (7∙Cl, 50 mg, 0.122 mmol) 136.7 (C-1”), 156.8 (C-4), 159.2 (C-4”), 161.1 (C-1’) ppm;
and sulfonimide K+-salt 6a or 6b (0.129 mmol) in acetonitrile FTIR (ATR) : 2915 (s), 2850 (m), 1631 (m), 1597 (m), 1567
(10 mL) was heated under reflux for 5 min. The solvent was (s), 1513 (m), 1467 (m), 1434 (m), 1417 (m), 1401 (m), 1301
removed under reduced pressure, the residue was taken up in (w), 1271 (s), 1239 (s), 1170 (w), 1114 (s), 1079 (vs), 1061 (s),
dichloromethane (20 mL), and the slurry was filtered with a 1004 (m), 972 (m), 913 (w), 835 (s), 800 (m), 714 (s) cm−1;
Rotilabo-syringe filter. After removal of all volatiles in vacuo, ESIMS (m/z): 376 [M]+, 331 [M+ − C2H6N − H]; ESIMS (m/z):
the residue was recrystallized from ethyl acetate to give the pure 418 [M]−, 249 [M− − C12H25]; HRMS–ESI (m/z): [M]+ calcd
salts 3a,b.
for C23H42N3O+, 376.3322; found, 376.3331; HRMS–ESI
(m/z): [M]− calcd for C19H32NO5S2–, 418.1716; found,
N-(4-(Dodecyloxy)phenyl)-N’,N’,N”,N”-tetramethylguani- 418.1724; Anal. calcd for C42H74N4O6S2 (795.2): C, 63.44; H,
dinium ((4-(dodecyloxy)phenyl)sulfonyl)((trifluoro- 9.38; N, 7.05; found: C, 63.55; H, 9.31; N, 7.07; DSC: Cr1 5 °C
methyl)sulfonyl)amide (3a): Yield: 95 mg (77%), colorless [8.1 kJ mol−1] Cr2 27 °C [−54.4 kJ mol−1] Cr3 71 °C
solid; 1H NMR (500 MHz, CDCl3) δ 0.88 (t, J = 7.0 Hz, 6H, [73.1 kJ mol−1] SmA 87 °C [1.4 kJ mol−1] I.
CH3), 1.20–1.39 (m, 32H, CH2), 1.40–1.49 (m, 4H, CH2),
1.73–1.82 (m, 4H, OCH2CH2), 2.98 (br s, 12H, N(CH3)2), 3.92 N-(4-(Dodecyloxy)phenyl)-N’,N’,N”,N”-tetramethylguani-
(t, J = 6.6 Hz, 2H, OCH2), 3.97 (t, J = 6.6 Hz, 2H, OCH2), dinium iodide (7∙I): A mixture of guanidinium chloride (7∙Cl,
1099

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
3. Ionic Liquids IIIB: Fundamentals, Progress, Challenges, and
Opportunities–Transformations and Processes; Seddon, K. R.;
Rogers, R. D., Eds.; ACS Symposium Series, Vol. 902; American
Chemical Society: Washington, 2005. doi:10.1021/bk-2005-0902
4. Wasserscheid, P.; Welton, T., Eds. Ionic Liquids in Synthesis, 2nd ed.;
Wiley-VCH: Weinheim, Germany, 2008. doi:10.1002/9783527621194
5. Dupont, J.; de Souza, R. F.; Suarez, P. A. Z. Chem. Rev. 2002, 102,
3667–3692. doi:10.1021/cr010338r
400 mg, 971 μmol) and potassium iodide (493 mg, 2.97 mmol)
in acetonitrile (15 mL) was heated under reflux for 5 min. After
being cooled to room temperature, the solvent was removed
under reduced pressure. The residue was taken up in
dichloromethane (20 mL), and the resulting slurry was filtered.
After evaporation of the filtrate to dryness the residue was re-
crystallized from ethyl acetate/acetonitrile (20:1). Yield:
446 mg (94%); colorless solid; 1H NMR (500 MHz, CDCl3) δ
0.88 (t, J = 6.9 Hz, 3H, CH3), 1.73–1.80 (m, 2H, OCH2CH2),
2.98 (br s, 12H, N(CH3)2), 3.91 (t, J = 6.6 Hz, 2H, OCH2),
6.84–6.91 (m, 2H, 3-H), 7.11–7.17 (m, 2H, 3-H), 9.93 (s, 1H,
NH) ppm; 13C NMR (125 MHz, CDCl3) δ 14.1 (CH3), 22.7,
26.0, 29.22, 29.36, 29.41, 29.58, 29.61, 29.64, 29.67, 31.9
(CH2), 41.0 (br s, N(CH3)2), 68.4 (OCH2), 115.6 (C-3), 122.6
(C-2), 129.8 (C-1), 157.1, 158.4 (C-4, C-1) ppm; FTIR (ATR)
: 2917 (s), 2847 (m), 1620 (s), 1558 (s), 1510 (s), 1467 (s),
1452 (m), 1417 (s), 1398 (s), 1312 (m), 1261 (m), 1229 (s),
1167 (m), 1115 (m), 1067 (m), 1024 (m), 1000 (m), 907 (w),
837 (s), 798 (w), 782 (w), 719 (m), 683 (s), 635 (m), 603 (m),
537 (m) cm−1; ESIMS (m/z): 376 [M]+, 331 [M+ − C2H6 − H];
ESIMS (m/z): 127 [M]−; HRMS–ESI (m/z): [M]+ calcd for
C23H42N3O+, 376.3323; found, 376.3343; Anal. calcd for
C23H42IN3O (503.5): C, 54.86; H, 8.41; N, 8.35; found: C,
54.91; H, 8.23; N, 7.97; DSC: Cr1 55 °C [−44.3 kJ mol−1] Cr2
130 °C [37.2 kJ mol−1] I.
6. Axenov, K. V.; Laschat, S. Materials 2011, 4, 206–259.
doi:10.3390/ma4010206
7. Kato, T.; Mizoshita, N.; Kishimoto, K. Angew. Chem. 2006, 118, 44–74.
doi:10.1002/ange.200501384
Angew. Chem., Int. Ed. 2006, 45, 38–68. doi:10.1002/anie.200501384
8. Binnemans, K. Chem. Rev. 2005, 105, 4148–4204.
doi:10.1021/cr0400919
9. Heintz, W. Justus Liebigs Ann. Chem. 1854, 92, 291–299.
doi:10.1002/jlac.18540920306
10.Heintz, W. J. Prakt. Chem. 1855, 66, 1–51.
doi:10.1002/prac.18550660101
11.Knight, G. A.; Shaw, B. D. J. Chem. Soc. 1938, 682–683.
doi:10.1039/jr9380000682
12.Somashekar, R. Mol. Cryst. Liq. Cryst. 1987, 146, 225–233.
doi:10.1080/00268948708071815
13.Bowlas, C. J.; Bruce, D. W.; Seddon, K. R. Chem. Commun. 1996,
1625–1626. doi:10.1039/cc9960001625
14.Jákli, A.; Saupe, A. One- and Two-Dimensional Fluids: Properties of
Smectic, Lamellar and Columnar Liquid Crystals; CRC Press: Boca
Raton, 2006. doi:10.1201/9781420012200
15.Welton, T. Chem. Rev. 1999, 99, 2071–2084. doi:10.1021/cr980032t
16.Plechkova, N. V.; Seddon, K. R. Chem. Soc. Rev. 2008, 37, 123–150.
doi:10.1039/b006677j
17.Bonhôte, P.; Dias, A.-P.; Papageorgiou, N.; Kalyanasundaram, K.;
Grätzel, M. Inorg. Chem. 1996, 35, 1168–1175. doi:10.1021/ic951325x
18.Jacquemin, J.; Husson, P.; Padua, A. A. H.; Majer, V. Green Chem.
2006, 8, 172–180. doi:10.1039/b513231b
Supporting Information
Supporting Information File 1
DSC traces of compounds 2a,b, 3a and X-ray data of
compound 3b.
19.Keskin, S.; Kayrak-Talay, D.; Akman, U.; Hortaçsu, Ö.
J. Supercrit. Fluids 2007, 43, 150–180.
doi:10.1016/j.supflu.2007.05.013
[http://www.beilstein-journals.org/bjoc/content/
supplementary/1860-5397-9-121-S1.pdf]
20.Johansson, K. M.; Adebahr, J.; Howlett, P. C.; Forsyth, M.;
MacFarlane, D. R. Aust. J. Chem. 2007, 60, 57–63.
doi:10.1071/CH06299
21.Hickman, T.; DesMarteau, D. D. J. Fluorine Chem. 2012, 133, 11–15.
doi:10.1016/j.jfluchem.2011.11.001
Acknowledgements
Generous financial support by the Studienstiftung des
Deutschen Volkes (Fellowship for M.B.), the Deutsche For-
schungsgemeinschaft, the Ministerium für Wissenschaft,
Forschung und Kunst des Landes Baden-Württemberg, the
Fonds der Chemischen Industrie and the Forschungsfonds der
Universität Stuttgart is gratefully acknowledged.
22.Gao, Y.; Slattery, J. M.; Bruce, D. W. New J. Chem. 2011, 35,
2910–2918. doi:10.1039/c1nj20715f
23.Bhowmik, P. K.; Han, H.; Cebe, J. J.; Nedeltchev, I. K.
Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 2002, 43,
1385–1386.
24.Bhowmik, P. K.; Han, H.; Cebe, J. J.; Burchett, R. A.; Acharya, B.;
Kumar, S. Liq. Cryst. 2003, 30, 1433–1440.
doi:10.1080/02678290310001621895
References
25.Bhowmik, P. K.; Han, H.; Nedeltchev, I. K.; Cebe, J. J.
Mol. Cryst. Liq. Cryst. 2004, 419, 27–46.
1. Endres, F.; MacFarlane, D.; Abbott, A. P., Eds. Electrodeposition from
Ionic Liquids; Wiley-VCH: Weinheim, Germany, 2008.
doi:10.1002/9783527622917
doi:10.1080/15421400490478272
26.Causin, V.; Saielli, G. J. Mater. Chem. 2009, 19, 9153–9162.
doi:10.1039/b915559g
2. Ionic Liquids IIIA: Fundamentals, Progress, Challenges, and
Opportunities; Seddon, K. R.; Rogers, R. D., Eds.; ACS Symposium
Series, Vol. 901; American Chemical Society: Washington, 2005.
doi:10.1021/bk-2005-0901
27.Jo, T. S.; Wray, J. K.; Tanthmanatham, O.; Han, H.; Bhowmik, P. K.
Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 2011, 52,
387–388.
1100

Beilstein J. Org. Chem. 2013, 9, 1093–1101.
28.Bonchio, M.; Carraro, M.; Casella, G.; Causin, V.; Rastrelli, F.;
Saielli, G. Phys. Chem. Chem. Phys. 2012, 14, 2710–2717.
doi:10.1039/c2cp23580c
License and Terms
This is an Open Access article under the terms of the
Creative Commons Attribution License
29.Fernandez, A. A.; de Haan, L. T.; Kouwer, P. H. J. J. Mater. Chem. A
2013, 1, 354–357. doi:10.1039/c2ta00133k
30.Alam, M. A.; Motoyanagi, J.; Yamamoto, Y.; Fukushima, T.; Kim, J.;
Kato, K.; Takata, M.; Saeki, A.; Seki, S.; Tagawa, S.; Aida, T.
J. Am. Chem. Soc. 2009, 131, 17722–17723. doi:10.1021/ja905373d
31.Goossens, K.; Nockemann, P.; Driesen, K.; Goderis, B.;
Görller-Walrand, C.; Van Hecke, K.; Van Meervelt, L.; Pouzet, E.;
Binnemans, K.; Cardinaels, T. Chem. Mater. 2008, 20, 157–168.
doi:10.1021/cm702321c
(http://creativecommons.org/licenses/by/2.0), which
permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
32.Goossens, K.; Lava, K.; Nockemann, P.; Van Hecke, K.;
Van Meervelt, L.; Pattison, P.; Binnemans, K.; Cardinaels, T. Langmuir
2009, 25, 5881–5897. doi:10.1021/la900048h
(http://www.beilstein-journals.org/bjoc)
The definitive version of this article is the electronic one
which can be found at:
33.Goossens, K.; Lava, K.; Nockemann, P.; Van Hecke, K.;
Van Meervelt, L.; Driesen, K.; Görller-Walrand, C.; Binnemans, K.;
Cardinaels, T. Chem.–Eur. J. 2009, 15, 656–674.
doi:10.1002/chem.200801566
doi:10.3762/bjoc.9.121
34.Bhowmik, P. K.; Han, H.; Cebe, J. J.; Burchett, R. A.; Sarker, A. M.
J. Polym. Sci., Part A: Polym. Chem. 2002, 40, 659–674.
doi:10.1002/pola.10134
35.Bhowmik, P. K.; Han, H.; Cebe, J. J.; Nedeltchev, I. K.; Kang, S.-W.;
Kumar, S. Macromolecules 2004, 37, 2688–2694.
doi:10.1021/ma030460n
36.Bhowmik, P. K.; Han, H.; Nedeltchev, A. K.
J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 1028–1041.
doi:10.1002/pola.21181
37.Han, H.; Vantine, P. R.; Nedeltchev, A. K.; Bhowmik, P. K.
J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 1541–1554.
doi:10.1002/pola.21259
38.Butschies, M.; Frey, W.; Laschat, S. Chem.–Eur. J. 2012, 18,
3014–3022. doi:10.1002/chem.201101925
39.Lo Celso, F.; Pibiri, I.; Triolo, A.; Triolo, R.; Pace, A.; Buscemi, S.;
Vivona, N. J. Mater. Chem. 2007, 17, 1201–1208.
doi:10.1039/B615190F
See for example for ILCs with trifluoromethanesulfonate counterion.
40.El Kadib, A.; Hesemann, P.; Molvinger, K.; Brandner, J.; Biolley, C.;
Gaveau, P.; Moreau, J. J. E.; Brunel, D. J. Am. Chem. Soc. 2009, 131,
2882–2892. doi:10.1021/ja807630j
41.Jones, P. B.; Parrish, N. M.; Houston, T. A.; Stapon, A.; Bansal, N. P.;
Dick, J. D.; Townsend, C. A. J. Med. Chem. 2000, 43, 3304–3314.
doi:10.1021/jm000149l
42.Sauer, S.; Saliba, S.; Tussetschläger, S.; Baro, A.; Frey, W.;
Giesselmann, F.; Laschat, S.; Kantlehner, W. Liq. Cryst. 2009, 36,
275–299. doi:10.1080/02678290902850027
43.Marcus, Y. J. Chem. Soc., Faraday Trans. 1993, 89, 713–718.
doi:10.1039/ft9938900713
44.Schulz, T.; Ahrens, S.; Meyer, D.; Allolio, C.; Peritz, A.; Strassner, T.
Chem.–Asian J. 2011, 6, 863–867. doi:10.1002/asia.201000744
45.Ahrens, S.; Peritz, A.; Strassner, T. Angew. Chem. 2009, 121,
8048–8051. doi:10.1002/ange.200903399
Angew. Chem., Int. Ed. 2009, 48, 7908–7910.
doi:10.1002/anie.200903399
1101