Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids

Article abstract of DOI:10.1016/j.molliq.2014.10.014

The synthesis and characterization of a series of new phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids ([Phpz^R][X] R = C_nH_2n+1 n: 1,2,3,4,5,6,7 [X] = CH₃SO₃^-, BF₄^-, PF₆^-) are described. Their melting points, thermal stabilities, electrochemical windows, and solubility properties in common solvents were investigated. They were found to exhibit very good electrochemical and thermal stabilities. The results indicate that these ionic liquids have a high thermal stability up to 374 °C and a large electrochemical window of 4.63 V. The thermophysical properties such as density, viscosity and refractive index were also measured as a function of temperature for the ionic liquids which are in liquid state at room temperature.

Full text of DOI:10.1016/j.molliq.2014.10.014

MOLLIQ-04487; No of Pages 7
Journal of Molecular Liquids xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
1
Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids
1
⁎
2Q1 Melek Canbulat Özdemir , Beytiye Özgün
3Q2 Department of Chemistry, Faculty of Science, Gazi University, Teknikokullar, 06500 Ankara, Turkey
4
a r t i c l e i n f o
a b s t r a c t
5
6
7
8
9
Article history:
Received 14 July 2014
Received in revised form 15 September 2014
Accepted 7 October 2014
Available online xxxx
The synthesis and characterization of a series of new phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic 16
liquids ([PhpzR][X] R = CnH2n + 1 n: 1,2,3,4,5,6,7 [X] = CH3SO3−, BF4−, PF6−) are described. Their melting points, Q173
OOF
thermal stabilities, electrochemical windows, and solubility properties in common solvents were investigated. 18
They were found to exhibit very good electrochemical and thermal stabilities. The results indicate that these 19
ionic liquids have a high thermal stability up to 374 °C and a large electrochemical window of 4.63 V. The 20
thermophysical properties such as density, viscosity and refractive index were also measured as a function of 21
10
11
23
12
13
14
15
Keywords:
Ionic liquids
3,5-Dimethylpyrazole
Methanesulfonate
Tetrafluoroborate
Hexafluorophosphate
temperature for the ionic liquids which are in liquid state at room temperature.
© 2014 Published by Elsevier B.V.
22
27
45
26
2Q8 4 1. Introduction
properties [22]. Recently, ionic liquid crystals based on pyrazolium 51
salts have been described [23]. 52
29
30
31
32
33
34
Ionic liquids (ILs) composed of cations and anions have a unique com-
Currently, attempts have been focused on the design and synthesis 53
of ionic liquids based on aryl/alkyl-substituted ILs which constitute a 54
new generation of ionic liquids termed TAAILs (Tunable Aryl Alkyl 55
Ionic Liquids). This new concept has been applied for the synthesis of 56
imidazole and 1,2,4-triazole-based tunable aryl/alkyl ILs with different 57
bination of properties such as low vapor pressure, non-flammability and
high thermal stability as well as a wide liquid range and wide electro-
chemical window [1–5]. Furthermore, the physical and chemical proper-
ties of ILs can be adjusted or tuned by controlling the nature of cations and
anions [6–9]. Numerous ILs based on imidazolium, pyridinium, and
chain lengths [24,25].
58
35Q5 quarternary ammonium cations with a variety of anions such as PF6−
,
In this context, we decided to extend this new concept to aryl/ 59
alkyl-substituted-3,5-dimethylpyrazolium salts. We kept the aryl 60
part constant (phenyl) and studied the influence of different alkyl 61
chains (C1–C7) and anions (CH3SO−3 , BF4−, and PF6−) on the properties of 62
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
BF−4 , (CF3SO3)2N−, and CF3SO3− have been successively synthesized and
are widely utilized in organic synthesis, catalysis, and the preparation of
nanostructured materials [10–15].
Researches involving pyrazolium-based ILs are quite rare in contrast
with imidazolium-based ILs. This is probably due to the lower nucleo-
philicity of the imine nitrogen atoms of pyrazoles compared to those
of imidazoles. From a structural viewpoint, the presence of two directly
bounded nitrogen atoms could not be neglected being able to modify
charge distribution and probably some of the physicochemical proper-
ties of the resulting salts.
the pyrazolium salts.
63
64
65
2. Results and discussion
2.1. Synthesis and characterization
As shown in Fig. 1, the synthesis of phenyl/alkyl-substituted-3,5- 66
dimethylpyrazolium ILs starts with the preparation of 3,5-dimethyl-1- 67
phenyl-1H-pyrazole (1). Compound 1 was synthesized by an improved 68
procedure from phenylhydrazinium hydrochloride and acetylacetone 69
Some 1,2-dialkylpyrazolium ILs have been investigated as electro-
lytes [16–19], catalysts for organic synthesis [20] and antibacterial
cationic surfactants [21]. These salts, though structurally analogous to
imidazolium-based ILUs, areNgenerCally cOharacteRrizedRby a ErelatiCvely TED PR
under MW irradiation since using conventional heating methods [26] is 70
low viscosity and a high conductivity with relevant electrochemical
time consuming. Subsequent quarternization by alkyl methanesulfonates 7Q16
of different alkyl chain lengths in acetonitrile at 80 °C under MW irradia- 72
tion for a period of 30 to 120 min led to phenyl/alkyl-substituted- 73
3,5-dimethylpyrazolium methanesulfonates (2a–2g). The yields of the 74
methanesulfonate alkylation reactions were typically 75–91%. One advan- 75
tage of the methanesulfonate ionic liquids is that the methanesulfonate 76
anion is base stable, and very easy to exchange for other anions. Thus, 77
the BF−4 and PF−6 salts (compounds 3a–3g and 4a–4g) were simply 78
⁎
Corresponding author.
E-mail addresses: ozmelek@metu.edu.tr (M.C. Özdemir), beytiye@gazi.edu.tr
(B. Özgün).
Present address: Department of Environmental Engineering, Faculty of Engineering,
Middle East Technical University, 06800 Ankara, Turkey.
1
http://dx.doi.org/10.1016/j.molliq.2014.10.014
0167-7322/© 2014 Published by Elsevier B.V.
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014

2
M.C. Özdemir, B. Özgün / Journal of Molecular Liquids xxx (2014) xxx–xxx
CH3
N
H3C
N
O
C
O
C
CH3COOH
NH-NH2.HCl
+
CH3
+
MW, 120 oC
H3C
CH3
N
R
H3C
N
-
(1)
BF4
HBF4(aq)
RT
CH3
+
CH3
(3a-3g)
[PhpzR][BF4
R= CnH2n+1 ; n : 1,2,3,4,5,6,7
O
-
]
N
RO
S
O
CH3
C
O
S
R
H3C
N
N
H3C
N
O
CH3
CH3
MW, 80 o
O
+
N
KPF6(aq)
RT
R
H3C
N
(2a-2g)
-
PF6
-
(1)
[PhpzR][CH3SO3
R= CnH2n+1 ; n : 1,2,3,4,5,6,7
]
(4a-4g)
-
[PhpzR][PF6
]
R= CnH2n+1 ; n : 1,2,3,4,5,6,7
Fig. 1. Synthesis of the ionic liquids described in this work.
79
80
81
82
83
84
85
86
87
88
89
90
91
92
prepared by anion exchange reactions of corresponding methane-
sulfonate salts (2a–2g) with HBF4 and KPF6 in aqueous solution at room
temperature with yields of 75–88% and 80–90%, respectively.
calorimetry (DSC) (Table 1). Some of the pyrazolium salts (2b, 3a, 3b, 96
4a and 4c) have melting points above 100 °C and do not fulfill the IL 97
criteria. Generally, increasing the alkyl chain length causing less efficient 98
packing in the solid resulted in a lower melting point and starting with 99
a chain length of more than three carbon atoms, all pyrazolium salts fulfill 100
the IL criteria. It is also noteworthy that the melting points of phenyl/ 101
alkyl-substituted-3,5-dimethylpyrazolium salts are lower in comparison 102
All of the pyrazolium salts were characterized by IR, 1H NMR, 13
C
NMR, TOF MS and elemental analysis. In addition, 19F NMR spectra
were recorded for the salts 3a–3g and 4a–4g. All the characterization
data were consistent with the expected structures and composi-
tions. The IR spectra of all the pyrazolium salts show the characteristic
bands of the pyrazolium moiety as well as those of the corresponding
counterions, where appropriate. In particular, the ν(C_N) and ν(C_C)
absorption bands from the pyrazolium cation appear at ca.
1595–1560 cm−1. In addition, characteristic bands of the BF4−, PF−6
with dialkylpyrazolium salts having the same counterion [27].
103
Two effects were taken into account to discuss thermal behaviour of 104
the compounds; the effect of the alkyl chain length and the effect of the 105
counterion. When studying the alkyl chain length, some features have 106
been determined. It is noticeable that most of the methanesulfonate 107
salts are in liquid state at room temperature and increasing the substit- 108
uent length initially increases the melting point with a major trend 109
towards glass formation. As seen in Fig. 2, the BF−4 salts show almost a 110
linear dependency of the melting point on the alkyl chain length from 111
one to four carbon atoms. Initial lengthening of the substitution leads 112
to reduction of melting points through destabilization of coulombic 113
and CH3SO−3 salts were observed at ca. 1030, 825 and 1198 cm−1
respectively.
,
93
2.2. Thermal properties
94
95
The thermal behavior of the phenyl/alkyl-substituted-3,5-
dimethylpyrazolium salts was investigated with differential scanning
t1:1
t1:2
Table 1
Thermal properties of the phenyl/alkyl-substituted-3,5-dimethylpyrazolium ILs.
a
b
c
a
b
c
t1:3
Entry Salts Tm
Tg
(°C)
Td
(°C)
Entry Salts Tm
Tg
(°C)
Td
(°C)
(°C)
(°C)
t1:4
1
2
3
4
5
6
7
8
2a
2b
2c
2d
2e
2f
2g
3a
3b
3c
3d
–
−53.3 282.1 12
3e
3f
–
−47.4 344.4
−46.6 342.7
t1:5
122.5
92.5
–
–
274.9 13
274.7 14
–
t1:6
–
3g
4a
4b
4c
4d
4e
4f
56.3
125.1
95.1
102.2
60.8
61.5
38.9
43.0
–
–
–
–
–
–
–
–
343.2
373.9
371.2
320.9
347.3
353.5
356.5
341.1
t1:7
−45.7 291.0 15
−54.7 272.2 16
−56.4 274.9 17
−49.0 260.2 18
t1:8
–
t1:9
–
t1:10
t1:11
t1:12
t1:13
t1:14
–
145.2
113.0
80.0
67.6
–
–
–
–
361.0 19
366.7 20
345.5 21
348.4
9
10
11
4g
a
t1:15
t1:16
t1:17
T
T
T
m — melting point.
g — glass transition temperature.
d — decomposition temperature.
Fig. 2. Dependence of the melting points (closed square) or glass transitions (open square)
b
c
of phenyl/alkyl-substituted-3,5-dimethylpyrazolium salts on the alkyl chain length with
the counterions; BF−4 , PF6− and CH3SO3−
.
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014

M.C. Özdemir, B. Özgün / Journal of Molecular Liquids xxx (2014) xxx–xxx
3
114 packing. Further increase in the chain length leads to glass formation for
1Q157 3e and 3f. This trend was also observed for the series of tetrafluorobo-
116 rate imidazolium salts [28]. No such trends in Tm values are observed
117 for the PF−6 salts 4a–4f. The behavior in the variation of the Tm from
118 4a to 4c and from 4d to 4f values shows similarity to that of aryl/alkyl-
119 substituted imidazolium hexafluorophosphates [24]. Considering the
120 effect of the counterion on the transition temperatures we found that
121 the size seems to modulate the melting temperatures of the salts.
122 Ionic liquids containing the smallest tetrafluoroborate anion displayed
123 high melting transitions. In the case of hexafluorophosphate salts the
124 melting points are lower than those of tetrafluoroborate salts for a
125 given cation. These observations follow the general empirically ob-
126 served trends for alkylimidazolium salts that the melting temperatures
127 are in the order [PF6]− b [BF4]−. Thermal behavior of the ILs does not
128 follow the same pattern with those of alkyloxyphenyl substituted
129 pyrazolium salts whereas the melting temperatures were found to be
130 in the order [BF4]− b [SbF6]− for a given cation [23].
the difficulty in rigorously drying these RTILs, the values may be some- 160
what affected by the residual water content. For the five CH3SO−3 and 161
two BF−4 RTILs studied, the experimental densities are presented in 162
Table 3. As expected, the densities are related to the molar masses of 163
the ions and the ILs containing heavy atoms are in general denser as 164
was observed for those composed of methanesulfonate when compared 165
to those with BF−4 . This is not however valid for cationic counterparts; 166
the density generally decreases with increasing alkyl chain length as 167
was documented for imidazolium based cations [34,35]. Within a series 168
of ionic liquids containing the same anion species, increasing cation 169
mass corresponds to the decreasing ionic liquid density. The densities 170
of the ILs are affected by the identity of the organic cation whereas the 171
density for ILs composed of the same cation is CH3SO−3 ~ BF4−.
172
A second series of measurements, analogous to those for densities, 173
allowed us to obtain dynamic viscosities of the RTILs. Again it should be 174
kept in mind that these RTILs contain traces of water, and as shown for 175
other ILs, the presence of water can affect the viscosity significantly [36, 176
37]. In the temperature range studied, the viscosity decreases with in- 177
creasing temperature. As seen in Table 3, viscosity of the RTILs increases 178
with increasing alkyl chain length. This may be attributed to the increase 179
131
Thermal stability of the pyrazolium salts was measured by
132 thermogravimetry analysis (TGA). The thermal decomposition tem-
133 peratures are presented in Table 1. All the phenyl/alkyl-substituted-
134 3,5-dimethylpyrazolium salts have thermal stability in the range of
135 260–374 °C. The onset of thermal decomposition temperatures
136 was found to be nearly independent of alkyl chain length. With re-
137 gard to the anion effect, Table 1 indicates that the thermal stability
in Van der Waals interactions as the length of alkyl chain increases. No 180
OOF
ing CH3SO−3 anion have higher viscosities compared with those having 183
184
such trend was observed for 1-alkyl-2,3,5-trimethylpyrazolium-based 181
room temperature ionic liquids [17]. It is also seen that the RTILs compris- 182
138
139
140
141
142
of PF−6 containing salts does not significantly differ from that of BF−4 con-
taining salts. The methanesulfonate anion dramatically reduces the ther-
mal stability, with the onset of decomposition occurring at least 50 °C
below the corresponding ILs with BF−4 and PF6− counterions. Relative
anion stabilities have been suggested as PF−6 , BF4− ≫ CH3SO3−.
BF−4 anion.
The refractive indices of these RTILs were found to decrease with in- 185
creasing temperature and to depend on the anion following the trend 186
BF−4 b CH3SO3− (Table 3). For the RTILs with CH3SO3− anion, refractive in- 187
dices decreased with increasing length of the alkyl chain in the cation 188
while for those with BF−4 anion increased.
189
143 2.3. Electrochemical stability
It can be concluded that the density, viscosity and refractive indices 190
of the RTILs were found to depend on temperature and the nature of 191
144
The electrochemical stability of the pyrazolium salts was evaluated
145 by cyclic voltammetry (CV) at 50 mV/s sweep rate, starting from anodic
146 to cathodic potentials and reversing back to the initial value. For the ILs
147 based on the same anion, the difference in electrochemical stability is
148 not so great. Most likely the length of the alkyl chain does not influence
149 the stability of the cation. The pyrazolium salts with PF−6 and BF4− anions
150 possess higher electrochemical stability than those with CH3SO−3 anion
151 and follow the order of stability PF−6 N BF4− N CH3SO3− by comparing
152 them to the salts having the same cation (Table 2). The electrochemical
153 windows (EW) of BF−4 and PF6− salts were higher than 4.0 V, values
154 which were better than some kinds of ILs, such as imidazolium, sulfoni-
155 um and guanidinium ILs [29–33].
Table 3
t3:1
Experimental densities (ρ), dynamic viscosities (η) and refractive indices (nr) of the RTILs t3:2
as a function of temperature at atmospheric pressure.a
t3:3
t3:4
Compound
T
(K)
ρ
η
nr
(g/cm3)
(mPa·s)
b
2a
298
308
313
333
298
308
313
333
298
308
313
333
298
308
313
333
298
1.2466
1.2451
1.2261
1.2111
1.1862
1.1788
1.1708
1.1559
1.1691
1.1512
1.1503
1.1356
1.1416
1.1368
1.1290
1.1148
1.1238
1.1225
1.1170
1.1035
1.1585
1.1536
1.1515
1.1376
1.1366
1.1336
1.1299
1.1164
–
1.5192
1.5167
1.5153
1.5100
1.5164
1.5137
1.5125
1.5065
1.5141
1.5117
1.5104
1.5043
1.5119
1.5092
1.5075
1.5011
1.5104
1.5079
1.5065
1.5008
1.4705
1.4722
1.4708
1.4651
1.4772
1.4740
1.4728
1.4671
t3:5
1440.71
844.84
162.03
t3:6
t3:7
t3:8
b
2d
2e
2f
–
t3:9
b
–
t3:10
t3:11
t3:12
t3:13
t3:14
t3:15
t3:16
t3:17
t3:18
t3:19
t3:20
t3:21
t3:22
t3:23
t3:24
t3:25
t3:26
t3:27
t3:28
t3:29
t3:30
t3:31
t3:32
886.67
212.22
156 2.4. Thermophysical properties
b
–
157
The densities, viscosities, and refractive indices of the seven dried
b
–
158 room temperature ionic liquids (RTILs) 2a, 2d–2g, 3e, and 3f were ob-
159 tained as a function of temperature from 298 K to 333 K. Because of
1548.22
285.67
b
–
b
–
t2:1
t2:2
t2:3
Table 2
1602.09
315.00
Cathodic and anodic potentials vs. Ag/Ag+ for EWs of the pyrazolium salts at a cut-off current
density of 1.0 mA/cm2 using GC macro-electrode as a working electrode at 25 °C.
b
2g
–
UNCORRECTED PR
b
308
–
t2:4
Entry Salts Ecathodic Eanodic EW
Entry Salts Ecathodic Eanodic EW
313
333
298
308
313
333
298
308
313
333
1666.61
346.86
(V)
(V)
(V)
(V)
(V)
(V)
b
t2:5
1
2
3
4
5
6
7
8
2a
2b
2c
2d
2e
2f
2g
3a
3b
3c
3d
−0.71
−0.63
−0.61
−0.60
−0.62
−0.65
−0.61
−1.82
−2.04
−1.92
−1.81
2.08
1.84
2.04
2.03
2.04
2.06
2.06
2.28
2.25
2.39
2.27
2.79 12
2.47 13
2.65 14
2.63 15
2.66 16
2.71 17
2.67 18
4.10 19
4.29 20
4.31 21
4.08
3e
3f
−2.19
−2.03
−1.97
−1.65
−1.71
−1.74
−1.70
−1.73
−1.71
−1.63
2.44
2.45
2.43
2.73
2.81
2.84
2.77
2.87
2.80
2.79
4.63
4.48
4.40
4.38
4.52
4.58
4.47
4.60
4.51
4.42
3e
–
t2:6
1665.73
1044.10
226.11
t2:7
3g
4a
4b
4c
4d
4e
4f
t2:8
b
t2:9
3f
–
t2:10
t2:11
t2:12
t2:13
t2:14
t2:15
2131.24
1284.84
253.82
9
10
11
a
Data were measured on samples which had a water content (wt.%) in the range t3:33
4g
of 0.2–0.32 according to coulometric Karl-Fischer titration.
t3:34
b
Not determined by a viscometer.
t3:35
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014

4
M.C. Özdemir, B. Özgün / Journal of Molecular Liquids xxx (2014) xxx–xxx
192 both the cation and the anion. Such trends were also well documented
193 for imidazolium-based ionic liquids [38–40].
for at least 10 min to minimize the effect of water and oxygen on cyclic 251
voltammograms. The experiments were performed at 25 °C, using 252
glassy carbon macro-electrode (surface area: 7.065 × 10−2 cm2) as a 253
working electrode, Pt as a counter electrode and Ag/AgCl as a reference 254
194 2.5. Solubility
electrode.
255
195
All of the pyrazolium salts synthesized were immiscible with nonpo-
196 lar solvents such as toluene, Et2O, benzene and hexane and were
197 completely miscible with polar solvents such as acetonitrile, acetone,
198 DMSO and chloroform. However, in water and low carbon alcohols
199 such as methanol and ethanol, all CH3SO−3 ionic liquids were miscible
200 while BF−4 and PF6− salts were immiscible.
4.2. The synthesis of 3,5-dimethyl-1-phenyl-1H-pyrazole
256
Phenylhydrazinium hydrochloride (5.0 mmol), acetylacetone 257
(5.0 mmol) and acetic acid (30.0 mL) were added to a round bottom 258
flask fitted with a reflux condenser. The mixture was heated at 120 °C 259
under MW irradiation. The progress of the reaction was monitored by 260
TLC (20% EtOAc–hexane). After completion of the reaction, acetic acid 261
was removed by rotary evaporation. The residue was dissolved in 262
ethyl acetate. The mixture was washed with diluted sodium hydrogen 263
carbonate, water and saturated brine, respectively. The separated or- 264
ganic phase was dried over anhydrous sodium sulfate. After removing 265
of ethyl acetate the remaining liquid product was purified with column 266
chromatography (silica gel: 20% EtOAc–hexane). Yield: 90%, orange 267
liquid. 1H NMR (300 MHz, DMSO-d6, ppm): δ = 2.18 (s, 3H, 5-CH3); 268
2.28 (s, 3H, 3-CH3); 6.05 (s, 1H, CH); 7.35–7.48 (m, 5H, Ph). 13C NMR 269
(75 MHz, DMSO-d6, ppm) δ = 12.57; 13.72; 107.55; 127.47–129.46; 270
201 3. Conclusions
202
We synthesized and characterized a new series of tunable phenyl/
203 alkyl-substituted-3,5-dimethylpyrazolium salts. The decomposition
204 temperatures were found to be dominated by anion effects and to be
205 nearly independent of the alkyl chain length. The electrochemical stabil-
206 ities of BF−4 and PF6− salts up to 4.63 V make these salts attractive for
207 electrochemical applications. It may also be expected that substituents
208 at phenyl ring will have a significant effect on the properties of the
209 resulting pyrazolium salts. We therefore plan to study the effect of sub-
210 stituents on the phenyl ring and current research in our laboratory is
211 ongoing.
139.48; 140.16 and 148.26.
271
4.3. General procedure for the synthesis of alkyl methanesulfonates
272
212 4. Experimental section
213 4.1. General methods
Methanesulfonate esters of alcohols were synthesized (except methyl 273
methanesulfonate and ethyl methanesulfonate) from methanesulfonyl 274
chloride and corresponding n-alkyl alcohols (n-propyl, n-butyl, n- 275
pentyl, n-hexyl or n-heptyl alcohol) using a previously described 276
procedure [41]. Their 1H NMR and 13C NMR spectra were recorded. 277
214
Chemicals were supplied by Acros, Fluka, Merck and Aldrich as well
215 as other common suppliers and used without further purification.
216 Microwave-assisted reactions were performed in a professional multi-
217 mode oven (Microsynth — Milestone). IR spectra were obtained from
218 samples in neat form with an ATR (Attenuated Total Reflectance) acces-
219 sory. 1H, 13C, and 19F NMR spectra were recorded on a Bruker-Avance-
220 300 MHz spectrometer, in CDCl3 or DMSO-d6 at 300, 75 and 282 MHz
221 respectively. Elemental analysis was carried out using a LECO, CHNS-
222 932 elemental analyzer. Mass spectra were recorded on Waters LCT
223 Premier XE (TOF MS). Differential scanning calorimetry experiments
224 were performed using a DSC-60 (Shimadzu), with a ramp temperature
225 of 10 °C min−1 under nitrogen atmosphere. The thermal stability of
226 the ionic liquids was investigated on a TA-60WS Thermal Analyzer
227 (Shimadzu) at a heating rate 10 °C min−1 with nitrogen as the purge
228 gas.
4.3.1. Propyl methanesulfonate: (colorless liquid)
278
1H NMR (300 MHz, DMSO-d6, ppm): δ = 0.92 (t, 3H, –OCH2CH2CH3); 279
1.68 (m, 2H, –OCH2CH2CH3); 4.15 (t, 2H, –OCH2CH2CH3); 3.15 (s, 3H, 280
S-CH3).13C NMR (75 MHz, CDCl3, ppm) δ = 9.53; 22.17; 36.48; 71.91.
281
282
4.3.2. Butyl methanesulfonate: (colorless liquid)
1H NMR (300 MHz, CDCl3, ppm): δ = 0.96 (t, 3H, –OCH2CH2CH2CH3); 283
1.46 (m, 2H, –OCH2CH2CH2CH3); 1.76 (m, 2H, –OCH2CH2CH2CH3); 4.23 284
(t, 2H, –OCH2CH2CH2CH3); δ 3.0 (s, 3H, S-CH3). 13C NMR (75 MHz, 285
CDCl3, ppm) δ = 13.08; 16.34; 30.75; 36.52; 70.12.
286
229
230 titrator, Cou-Lo Aquamax KF moisture meter.
231
Density of the RTILs was measured using a Anton Paar DMA-4500 M
232 digital densimeter based on the “oscillating U-tube principle” and
233 thermostated at different temperatures. Two integrated Pt 100 plati-
234 num thermometers were provided for good precision in temperature
The water content was determined using a coulometric Karl-Fischer
4.3.3. Pentyl methanesulfonate: (colorless liquid)
287
1H NMR (300 MHz, DMSO-d6, ppm): δ = 0.87 (t, 3H, – 288
OCH2CH2CH2CH2CH3); 1.33 (m, 4H, –OCH2CH2CH2CH2CH3); 1.70 289
(m, 2H, –OCH2CH2CH2CH2CH3); 4.19 (t, 2H, –OCH2CH2CH2CH2CH3); 290
2.95 (s, 3H, S-CH3). 13C NMR (75 MHz, CDCl3, ppm) δ = 13.51; 291
235
236
237
238
239
240
241
control internally (T 0.01 K). The densimeter protocol includes an auto-
matic correction for the viscosity of the sample. The apparatus is precise to
within 1.0 × 10−5 g/cm3, and the uncertainty of the measurements was
estimated to be better than 1.0 × 10−4 g/cm3. Calibration of the
densimeter was performed at an atmospheric pressure using doubly dis-
tilled and degassed water.
21.81; 27.23; 28.48; 36.49; 70.37.
292
4.3.4. Hexyl methanesulfonate: (colorless liquid)
293
1H NMR (300 MHz, CDCl3, ppm): δ = 0.83 (t, 3H, −OCH2CH2CH2 294
CH2CH2CH3); 1.25 (m, 6H, −OCH2CH2CH2CH2CH2CH3); 1.67 (m, 2H, 295
−OCH2CH2CH2CH2CH2CH3); 4.14 (t, 2H, −OCH2CH2CH2CH2CH2CH3); 296
2.93 (s, 3H, S-CH3). 13C NMR (75 MHz, CDCl3, ppm) δ = 13.85; 22.44; 297
The dynamic viscosity of the RTILs was measured using an Anton
242 Paar Microviscosimeter based on a falling-ball principle. A laser sensor
243 detects the time, t1, taken by the ball to fall a given distance in a capillary
244 tube of calibrated diameter filled with the mixture.
24.99; 28.99; 31.11; 37.12; 70.34.
298
24Q58
246
247
248
Refractive index measurements were conducted with a refractometry
DR 6300-TF, A. Krüss Optronic GmbH equipped with a temperature con-
trol using a He–Ne light source with a wavelength of 633 nm.
4.3.5. Heptyl methanesulfonate: (colorless liquid)
299
1H NMR (300 MHz, CDCl3, ppm): δ = 0.90 (t, 3H, −OCH2CH2 300
CH2CH2CH2CH2CH3); 1.31 (m, 8H, −OCH2CH2CH2CH2CH2CH2CH3); 301
1.76 (m, 2H, −OCH2CH2CH2CH2CH2CH2CH3); 4.23 (t, 2H, −OCH2CH2 302
CH2CH2CH2CH2CH3); 3.01 (s, 3H, S-CH3). 13C NMR (75 MHz, CDCl3, 303
Cyclic voltammetry was conducted on a Electrochemical Worksta-
249 tion CHI-660B instrument. 0.1 M solution of the salts was prepared in
250 anhydrous acetonitrile and then the solution was purged with nitrogen
ppm) δ = 13.82; 22.36; 25.21; 28.54; 28.96; 31.49; 36.87; 70.33.
304
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014

M.C. Özdemir, B. Özgün / Journal of Molecular Liquids xxx (2014) xxx–xxx
5
305 4.4. General procedure for the synthesis of 1-phenyl-2-alkyl-3,
306 5-dimethylpyrazolium methanesulfonates (2a–2g)
4.4.5. 1-Phenyl-3,5-dimethyl-2-pentylpyrazolium methanesulfonate (2e) 364
Yield: 78%, orange liquid. IR (ATR, cm−1) νmax = 3053, 2927–2857, 365
1593, 1560, 1495, 1198, 1037, 100–750. 1H NMR (300 MHz, CDCl3, 366
ppm): δ = 0.77 (t, 3H, −NCH2CH2CH2CH2CH3); 1.12 (m, 4H, 367
−NCH2CH2CH2CH2CH3); 1.49 (m, 2H, −NCH2CH2CH2CH2CH3); 368
4.25 (t, 2H, –NCH2CH2CH2CH2CH3); 2.23 (s, 3H, 5-CH3); 2.65 369
(s, 3H, 3-CH3); 2.79 (s, 3H, S-CH3); 6.55 (s, 1H, CH); 7.70 (m, 5H, 370
Ph). 13C NMR (75 MHz, CDCl3, ppm): δ = 12.40; 12.45; 13.56; 371
21.68; 28.09; 28.56; 39.33; 47.90; 108.61; 129.02–132.63; 147.22; 372
147.81. Analysis: calcd for C17H26N2O3S: C 60.33, H 7.74, N 8.28, S 373
9.47. Found: C 60.20, H 7.75, N 8.26, S 9.61. TOF MS (ES+) m/z 374
calcd. for C16H23N2: 243.1861. Found: 243.1868. TOF MS (ES−) m/z 375
307
3,5-Dimethyl-1-phenyl-1H-pyrazole (5.0 mmol), appropriate alkyl
308 methanesulfonate (5.0 mmol), and acetonitrile (5.0 mL) were added
309 to a round-bottomed flask equipped with a reflux condenser and heated
310 at 80 °C under MW irradiation. The progress of the reaction was moni-
311 tored by TLC (80% EtOAc–hexane). After completion of the reaction, ace-
312 tonitrile was removed by rotary evaporation. The resulting product was
313 washed two times with 20.0 mL of hexane and then two times with
314 20.0 mL of diethylether. After this, active charcoal and 20.0 mL acetoni-
315 trile were and stirred for 24 h and then filtered. The filtrate was dried
316 over anhydrous sodium sulfate and concentrated. The synthesized
317 salts were set under vacuum for 48 h at 75 °C.
calcd. for CH3O3S: 94.9803. Found: 94.9799.
376
4.4.6. 1-Phenyl-3,5-dimethyl-2-hexylpyrazolium methanesulfonate (2f)
377
Yield: 75%, orange liquid. IR (ATR, cm−1) νmax = 3055, 2930–2859, 378
1593, 1560, 1495, 1197, 1037, 1000–750. 1H NMR (300 MHz, CDCl3, 379
ppm): δ = 0.80 (t, 3H, −NCH2CH2CH2CH2CH2CH3);1.12 (m, 6H, 380
NCH2CH2CH2CH2CH2CH3); 1.48 (m, 2H, NCH2CH2CH2CH2CH2CH3); 381
4.28 (t, 2H, NCH2CH2CH2CH2CH2CH3); 2.23 (s, 3H, 5-CH3); 2.66 (s, 3H, 382
318 4.4.1. 1-Phenyl-2,3,5-trimethylpyrazolium methanesulfonate (2a)
319
Yield: 91%, yellow liquid. IR (ATR, cm−1) νmax = 3055, 2970–2930,
320 1592, 1564, 1496, 1195, 1036, 100–750. 1H NMR (300 MHz, CDCl3,
321 ppm): δ = 2.23 (s, 3H, 5-CH3); 2.63 (s, 3H, 3-CH3); 2.73 (s, 3H, S-
322 CH3); 3.78 (s, 3H, NCH3); 6.51 (s, 1H, CH); 7.68 (m, 5H, Ph). 13C NMR
323 (75 MHz, CDCl3, ppm) δ = 12.34; 12.44; 35.07; 39.34; 108.17;
324 128.92–132.58; 146.65 and 148.11. Analysis: calcd for C13H18N2O3S: C
325 55.30, H 6.43, N 9.92, S 11.36. Found: C 55.16, H 6.44, N 9.90, S 11.49.
326 TOF MS (ES+) m/z calcd. for C12H15N2: 187.1235. Found: 187.1234.
327 TOF MS (ES−) m/z calcd. for CH3O3S: 94.9803. Found: 94.9801.
3-CH3); 2.77 (s, 3H, S-CH3); 6.54 (s, 1H, CH); 7.70 (m, 5H, Ph). 13C 383
OOF
NMR (75 MHz, CDCl3, ppm): δ = 12.43; 12.54; 13.76; 22.15; 25.75; 384
28.88; 30.72; 39.38; 48.02; 108.51; 129.17–132.55; 146.99; 147.88. 385
Analysis: calcd for C18H28N2O3S: C 61.33, H 8.01, N 7.95, S 9.10. Found: 386
C 61.21, H 8.01, N 7.93, S 9.24. TOF MS (ES+) m/z calcd. for C17H25N2: 387
257.2018. Found: 257.2018. TOF MS (ES−) m/z calcd. for CH3O3S: 388
94.9803. Found: 94.9800.
389
328 4.4.2. 1-Phenyl-2-ethyl-3,5-dimethylpyrazolium methanesulfonate (2b)
329
Yield: 89%, yellow solid. IR (ATR, cm−1) νmax = 3048, 2970–2930,
4.4.7. 1-Phenyl-3,5-dimethyl-2-heptylpyrazolium methanesulfonate (2 g) 390
Yield: 75%, orange liquid. IR (ATR, cm−1) νmax = 3053, 2928–2857, 391
1593, 1560, 1495, 1198, 1037, 1000–750. 1H NMR (300 MHz, CDCl3, 392
ppm): δ = 0.80 (t, 3H, –NCH2CH2CH2CH2CH2CH2CH3); 1.11 (m, 8H, 393
–NCH2CH2CH2CH2CH2CH2CH3);1.46 (m, 2H, –NCH2CH2CH2CH2CH2 394
CH2CH3); 4.23 (t, 2H, –NCH2CH2CH2CH2CH2CH2CH3); 2.23 (s, 3H, 395
5-CH3); 2.65 (s, 3H, 3-CH3); 2.79 (s, 3H, S-CH3); 6.54 (s, 1H, CH); 7.71 396
(m, 5H, Ph). 13C NMR (75 MHz, CDCl3, ppm): δ = 12.42; 12.50; 13.92; 397
22.34; 26.02; 28.26; 28.90; 31.25; 39.35; 47.96; 108.57; 129.12– 398
132.58; 147.10; 147.85. Analysis: calcd for C19H31N2O3S: C 62.09, H 399
8.50, N 7.62; S 8.72. Found: C 61.97, H 8.51, N 7.61, S 8.84. TOF MS 400
(ES+) m/z calcd. for C18H27N2: 271.2174. Found: 271.2173. TOF MS 401
330 1591, 1558, 1483, 1190, 1037, 100–750. 1H NMR (300 MHz, CDCl3,
331 ppm): δ = 1.16 (t, 3H, –NCH2CH3); 4.37 (q, 2H, –NCH2CH3); 2.21 (s,
332 3H, 5-CH3); 2.65 (s, 3H, 3-CH3); 2.70 (s, 3H, S-CH3); 6.53 (s, 1H, CH);
333 7.69 (m, 5H, Ph). 13C NMR (75 MHz, CDCl3, ppm): δ = 11.95; 12.16;
334 14.20; 39.19; 43.08; 108.51; 128.65–132.57; 147.19; 147.22. Analysis:
335 calcd for C14H20N2O3S: C 56.73, H 6.80, N 9.45, S 10.82. Found:
336 C 56.60, H 6.81, N 9.43, S 10.95. TOF MS (ES+) m/z calcd. for
337 C13H17N2: 201.1392. Found: 201.1389. TOF MS (ES−) m/z calcd. for
338 CH3O3S: 94.9803. Found: 94.9799.
339 4.4.3. 1-Phenyl-3,5-dimethyl-2-propylpyrazolium methanesulfonate (2c)
340
Yield: 80%, yellow solid. IR (ATR, cm−1) νmax = 3055, 2970–2879,
(ES−) m/z calcd. for CH3O3S: 94.9803. Found: 94.9799.
402
341 1592, 1560, 1495, 1206, 1038, 1000–750. 1H NMR (300 MHz, CDCl3,
342 ppm): δ = 0.78 (t, 3H, –NCH2CH2CH3); 1.52 (m, 2H, –NCH2CH2CH3);
343 4.2 (t, 2H, –NCH2CH2CH3); 2.22 (s, 3H, 5-CH3); 2.66 (s, 3H, 3-CH3);
344 2.72 (s, 3H, S-CH3); 6.55 (s, 1H, CH); 7.69 (m, 5H, Ph). 13C NMR
345 (75 MHz, CDCl3, ppm): δ = 10.66; 12.33; 12.41; 22.32; 39.33;
346 49.21; 108.57; 128.93–132.49; 147.20; 147.93. Analysis: calcd for
347 C15H22N2O3S: C 58.04, H 7.14, N 9.02, S 10.33. Found: C 57.91, H
348 7.15, N 9.0, S 10.47. TOF MS (ES+) m/z calcd. for C14H19N2:
349 215.1548. Found: 215.1549. TOF MS (ES−) m/z calcd. for CH3O3S:
350 94.9803. Found: 94.9802.
4.5. General procedure for the synthesis of 1-phenyl-2-alkyl-3, 403
5-dimethylpyrazolium tetrafluoroborates (3a–3g) 404
Tetrafluoroboric acid (40% solution in water, 5.0 mmol) was added 405
dropwise to a solution of the appropriate methanesulfonate salt 406
(5.0 mmol) in water (10.0 appropriate mL) and the mixture was stirred 407
at room temperature for 2 h. The resulting solid salt was collected and 408
recrystallized from ethanol. The resulting liquid salt, which formed 409
two phases, was purified by the decantation of the aqueous layer and 410
washed two times with 20.0 mL of hexane and diethylether, respective- 411
ly. After this, 20.0 mL of acetonitrile and active charcoal was added and 412
351 4.4.4. 1-Phenyl-2-butyl-3,5-dimethylpyrazolium methanesulfonate (2d)
UNCORRECTED PR
Yield: 89%, yellow liquid. IR (ATR, cm−1) νmax = 3055, 2970–2873,
refluxed over 24 h. The solution was filtered and the filtrate was dried 413
over anhydrous sodium sulfate and concentrated. The synthesized 414
352
353 1592, 1560, 1494, 1198, 1036, 100–750. 1H NMR (300 MHz, CDCl3,
354 ppm): δ = δ 0.76 (t, 3H, −NCH2CH2CH2CH3); 1.19 (m, 2H,
355 −NCH2CH2CH2CH3); 1.48 (m, 2H, −NCH2CH2CH2CH3); 4.26 (t, 2H,
356 −NCH2CH2CH2CH3); 2.23 (s, 3H, 5-CH3); 2.65 (s, 3H, 3-CH3); 2.80
357 (s, 3H, S-CH3); 6.56 (s, 1H, CH); 7.70 (m, 5H, Ph). 13C NMR
358 (75 MHz, CDCl3, ppm): δ = 12.13; 12.18; 12.96; 19.09; 30.60;
359 39.17; 47.35; 108.50; 128.72–132.51; 147.22; 147.53. Analysis:
360 calcd for C16H24N2O3S: C 59.23, H 7.46, N 8.63, S 9.88. Found: C
361 59.10, H 7.46, N 8.62, S 9.98. TOF MS (ES+) m/z calcd. for
362 C15H21N2: 229.1705. Found: 229.1703. TOF MS (ES−) m/z calcd. for
363 CH3O3S: 94.9803. Found: 94.9805.
salts were set under vacuum at 75 °C for 48 h.
415
4.5.1. 1-Phenyl-2,3,5-trimethylpyrazolium tetrafluoroborate (3a)
416
Yield: 88%, white solid. IR (ATR, cm−1) νmax = 3072, 2970–2930, 417
1594, 1571, 1499, 1032, 834. 1H NMR (300 MHz, CDCl3, ppm): δ = 418
2.22 (s, 3H, 5-CH3); 2.56 (s, 3H, 3-CH3); 3.68 (s, 3H, NCH3); 6.50 (s, 419
1H, CH); 7.58 (m, 2H, Ph); 7.70 (m, 3H, Ph). 13C NMR (75 MHz, CDCl3, 420
ppm) δ = 11.93; 12.14; 34.43; 108.07; 128.77–132.62; 146.64 and 421
147.96. 19F NMR (282 MHz, CDCl3, ppm): δ = −153.97, −154.03. Anal- 422
ysis: calcd for C12H15N2BF4: C 52.59, H 5.52, N 10.22. Found: C 53.03, H 423
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014

6
M.C. Özdemir, B. Özgün / Journal of Molecular Liquids xxx (2014) xxx–xxx
424 5.37, N 10.10. TOF MS (ES+) m/z calcd. for C12H15N2: 187.1235. Found:
425 187.1229.
4.5.7. 1-Phenyl-3,5-dimethyl-2-heptylpyrazoliumtetrafluoroborate (3g)
484
Yield: 84%, pinky solid. IR (ATR, cm−1) νmax = 3068, 2951–2865, 485
1595, 1562, 1495, 1034, 824. 1H NMR (300 MHz, CDCl3, ppm): δ = 0.80 486
(t, 3H, −NCH2CH2CH2CH2CH2CH2CH3); 1.09 (m, 8H, –NCH2CH2CH2 487
CH2CH2CH2CH3); 1.49 (m, 2H, –NCH2CH2CH2CH2CH2CH2CH3); 4.09 488
(t, 2H, –NCH2CH2CH2CH2CH2CH2CH3); 2.20 (s, 3H, 5-CH3); 2.55 (s, 3H, 489
3-CH3); 6.54 (s, 1H, CH); 7.57 (m, 2H, Ph); 7.69 (m, 3H, Ph). 13C NMR 490
(75 MHz, CDCl3, ppm): δ = 11.91; 12.12; 13.89; 22.27; 25.87; 28.06; 491
28.66; 31.16; 47.41; 108.53; 128.78–132.67; 147.44; 147.54. 19F NMR 492
(282 MHz, CDCl3, ppm): δ = −153.50, −153.55. Analysis: calcd for 493
C18H27N2BF4: C 60.35, H 7.60, N 7.82. Found: C 60.33, H 7.45, N 7.91. 494
426 4.5.2. 1-Phenyl-2-ethyl-3,5-dimethylpyrazolium tetrafluoroborate (3b)
427
Yield: 78%, white solid. IR (ATR, cm−1) νmax = 3077, 2970–2943,
428 1594, 1562, 1498, 1032, 827. 1H NMR (300 MHz, CDCl3, ppm): δ =
429 1.16 (t, 3H, –NCH2CH3); 4.18 (q, 2H, –NCH2CH3); 2.18 (s, 3H, 5-CH3);
430 2.55 (s, 3H, 3-CH3); 6.51 (s, 1H, CH); 7.56 (m, 2H, Ph); 7.68 (m, 3H,
431 Ph). 13C NMR (75 MHz, CDCl3, ppm): δ = 11.75; 12.14; 14.21; 42.89;
432 108.54; 128.79–132.72; 147.29; 147.42. 19F NMR (282 MHz, CDCl3,
433 ppm): δ = −153.59, −153.64. Analysis: calcd for C13H17N2BF4: C
TOF MS (ES+) m/z calcd. for C18H27N2: 271.2174. Found: 271.2170.
495
434
54.20, H 5.95, N 9.72. Found: C 54.05, H 5.84, N 9.72. TOF MS (ES+) m/z
calcd. for C13H17N2: 201.1392. Found: 201.1391.
435
4.6. General procedure for the synthesis of 1-phenyl-2-alkyl-3, 496
5-dimethylpyrazolium hexafluorophosphates (4a–4g) 497
436 4.5.3. 1-Phenyl-3,5-dimethyl-2-propylpyrazolium tetrafluoroborate (3c)
437
Yield: 75%, white solid. IR (ATR, cm−1) νmax = 3068, 2971–2886,
Potassium hexafluorophosphate (5.0 mmol) solution in 5.0 mL of 498
water was added dropwise to a solution of the appropriate methane- 499
sulfonate salt (5.0 mmol) in water (5.0 mL) and the mixture was stirred 500
at room temperature for 2 h. The resulting solid salt was collected and 501
438 1593, 1557, 1494, 1031, 827. 1H NMR (300 MHz, CDCl3, ppm): δ =
439 0.74 (t, 3H, −NCH2CH2CH3); 1.54 (m, 2H, −NCH2CH2CH3); 4.06 (t,
440 2H, −NCH2CH2CH3); 2.19 (s, 3H, 5-CH3); 2.54 (s, 3H, 3-CH3); 6.53 (s,
441 1H, CH); 7.54 (m, 2H, Ph); 7.67 (m, 3H, Ph).13C NMR (75 MHz, CDCl3,
442 ppm): δ = 10.64; 12.06; 12.22; 22.37; 48.93; 108.55; 128.80–132.72;
443 147.55; 147.79. 19F NMR (282 MHz, CDCl3, ppm): δ = −153.63,
444 −153.68. Analysis: calcd for C14H19N2BF4: C 55.66, H 6.34, N 9.27.
445 Found: C 55.66, H 6.06, N 9.28. TOF MS (ES+) m/z calcd. for C14H19N2:
446 215.1548. Found: 215.1546.
recrystallized from ethanol.
502
4.6.1. 1-Phenyl-2,3,5-trimethylpyrazolium hexafluorophosphate (4a)
503
Yield: 90%, white solid. IR (ATR, cm−1) νmax = 3073, 2960–2833, 504
1594, 1561, 1496, 825, 769. 1H NMR (300 MHz, CDCl3, ppm): δ = 2.19 505
(s, 3H, 5-CH3); 2.50 (s, 3H, 3-CH3); 3.61 (s, 3H, NCH3); 6.46 (s, 1H, 506
CH); 7.50 (m, 2H, Ph); 7.66 (m, 3H, Ph). 13C NMR (75 MHz, CDCl3, 507
ppm) δ = 11.77; 12.07; 34.23; 108.12; 128.62–132.73; 146.75 and 508
147.91. 19F NMR (282 MHz, CDCl3, ppm): δ = −72.39–74.91. Analysis: 509
calcd for C12H15N2PF6: C 43.38, H 4.55, N 8.43. Found: C 43.45, H 4.57, N 510
8.41. TOF MS (ES+) m/z calcd. for C12H15N2: 187.1235. Found: 187.1229. 511
447 4.5.4. 1-Phenyl-2-butyl-3,5-dimethylpyrazolium tetrafluoroborate (3d)
448
Yield 87%, white solid. IR (ATR, cm−1) νmax = 3062, 2970–2857,
449 1592, 1561, 1485, 1032, 847. 1H NMR (300 MHz, CDCl3, ppm): δ =
450 0.75 (t, 3H, −NCH2CH2CH2CH3); 1.18 (m, 2H, −NCH2CH2CH2CH3);
451 1.49 (m, 2H, −NCH2CH2CH2CH3); 4.12 (t, 2H, −NCH2CH2CH2CH3);
452 2.21 (s, 3H, 5-CH3); 2.57 (s, 3H, 3-CH3); 6.53 (s, 1H, CH); 7.58 (m, 2H,
453 Ph); 7.70 (m, 3H, Ph).13C NMR (75 MHz, CDCl3, ppm): δ = 11.97;
454 12.18; 13.07; 19.29; 30.74; 47.28; 108.56; 128.83–132.71; 147.49;
455 147.65. 19F NMR (282 MHz, CDCl3, ppm): δ = −153.55, −153.60. Anal-
456 ysis: calcd for C15H21N2BF4: C 56.99, H 6.70, N 8.86. Found: C 57.23, H
457 6.38, N 8.93. TOF MS (ES+) m/z calcd. for C15H21N2: 229.1705. Found:
458 229.1708.
TOF MS (ES−) m/z calcd. for PF6: 144.9642. Found: 144.9639.
512
4.6.2. 1-Phenyl-2-ethyl-3,5-dimethylpyrazolium hexafluorophosphate 513
(4b) 514
Yield: 87%, white solid. IR (ATR, cm−1) νmax = 3080, 2979–2946, 515
1594, 1560, 1496, 825, 776. 1H NMR (300 MHz, CDCl3, ppm): δ = 1.19 516
(t, 3H, –NCH2CH3); 4.17 (q, 2H, –NCH2CH3); 2.22 (s, 3H, 5-CH3); 2.57 517
(s, 3H, 3-CH3); 6.52 (s, 1H, CH); 7.54 (m, 2H, Ph); 7.71 (m, 3H, Ph). 518
13C NMR (75 MHz, CDCl3, ppm): δ = 11.61; 12.05; 14.15; 42.81; 519
108.60; 128.66–132.81; 147.23; 147.58. 19F NMR (282 MHz, CDCl3, 520
ppm): δ = −72.21; −74.73. Analysis: calcd for C13H17N2PF6: C 45.09, 521
H 4.95, N 8.09. Found: C 44.82, H 4.94, N 8.04. TOF MS (ES+) m/z 522
calcd. for C13H17N2: 201.1392. Found: 201.1388. TOF MS (ES−) m/z 523
459 4.5.5. 1-Phenyl-3,5-dimethyl-2-pentylpyrazolium tetrafluoroborate (3e)
460
461
462
Yield:75%, yellow liquid. IR (ATR, cm−1) νmax = 3065, 2958–2872,
1593, 1561, 1496, 1030, 826. 1H NMR (300 MHz, CDCl3, ppm): δ = 0.75
(t, 3H, −NCH2CH2CH2CH2CH3); 1.11 (m, 4H, −NCH2CH2CH2CH2CH3);
463 1.52 (m, 2H, −NCH2CH2CH2CH2CH3); 4.09 (t, 2H, −NCH2CH2CH2
464 CH2CH3); 2.20 (s, 3H, 5-CH3); 2.55 (s, 3H, 3-CH3); 6.53 (s, 1H, CH);
465 7.58 (m, 2H, Ph); 7.70 (m, 3H, Ph). 13C NMR (75 MHz, CDCl3,
466 ppm): δ = 11.97; 12.17; 13.53; 21.58; 28.02; 28.41; 47.49; 108.56;
467 128.81–132.70; 147.49; 147.63. 19F NMR (282 MHz, CDCl3, ppm):
468 δ = −153.52, −153.57. Analysis: calcd for C16H23N2BF4: C 58.20,
469 H 7.02, N 8.48. Found: C 58.30, H 7.04, N 8.56. TOF MS (ES+) m/z
470 calcd. for C16H23N2: 243.1861. Found: 243.1861.
calcd. for PF6: 144.9642. Found: 144.9644.
524
4.6.3. 1-Phenyl-3,5-dimethyl-2-propylpyrazolium hexafluorophosphate (4c) 525
Yield: 80%, white solid. IR (ATR, cm−1) νmax = 3078, 2967–2882, 526
1593, 1557, 1494, 825, 763. 1H NMR (300 MHz, CDCl3, ppm): δ = 0.77 527
(t, 3H, −NCH2CH2CH3); 1.56 (m, 2H, −NCH2CH2CH3); 4.02 (t, 2H, 528
−NCH2CH2CH3); 2.19 (s, 3H, 5-CH3); 2.54 (s, 3H, 3-CH3); 6.52 (s, 1H, 529
CH); 7.51 (m, 2H, Ph); 7.70 (m, 3H, Ph). 13C NMR (75 MHz, CDCl3, 530
ppm): δ = 10.56; 11.90; 12.11; 22.34; 48.86; 108.60; 128.66–132.82; 531
147.71; 147.73. 19F NMR (282 MHz, CDCl3, ppm): δ = −72.23; 532
−74.75. Analysis: calcd for C14H19N2PF6: C 46.67, H 5.32, N 7.78. 533
Found: C 46.47, H 4.95, N 7.75. TOF MS (ES+) m/z calcd. for C14H19N2: 534
215.1548. Found: 215.1540. TOF MS (ES−) m/z calcd. for PF6: 535
471 4.5.6. 1-Phenyl-3,5-dimethyl-2-hexylpyrazolium tetrafluoroborate (3f)
472
Yield: 86%, yellow liquid. IR (ATR, cm−1
) νmax = 3068,
473 2970–2860, 1593, 1561, 1496, 1031, 837. 1H NMR (300 MHz,
474 CDCl3, ppm): δ = 0.78 (t, 3H, –NCH2CH2CH2CH2CH2CH3); 1.09 (m,
475 6H, –NCH2CH2CH2CH2CH2CH3); 1.52 (m, 2H, –NCH2CH2CH2CH2
476 CH2CH3); 4.12 (t, 2H, –NCH2CH2CH2CH2CH2CH3); 2.21 (s, 3H,
477 5-CH3); 2.56 (s, 3H, 3-CH3); 6.54 (s, 1H, CH); 7.57 (m, 2H, Ph);
478 7.69 (m, 3H, Ph).13C NMR (75 MHz, CDCl3, ppm): δ = 12.01;
479 12.20; 13.74; 22.10; 25.67; 28.72; 30.60; 47.52; 108.56; 128.87–
480 132.69; 147.44; 147.63. 19F NMR (282 MHz, CDCl3, ppm): δ =
481 −153.60, −153.65. Analysis: calcd for C17H25N2BF4: C 59.32,
482 H 7.32, N 8.14. Found: C 59.10, H 7.13, N 8.27. TOF MS (ES+) m/z
483 calcd. for C17H25N2: 257.2018. Found: 257.2007.
144.9642. Found: 144.9646.
536
4.6.4. 1-Phenyl-2-butyl-3,5-dimethylpyrazolium hexafluorophosphate (4d) 537
Yield: 85%, white solid. IR (ATR, cm−1) νmax = 3073, 2971–2865, 538
1591, 1557, 1494, 826, 766. 1H NMR (300 MHz, CDCl3, ppm): δ = 0.75 539
(t, 3H, −NCH2CH2CH2CH3); 1.18 (m, 2H, −NCH2CH2CH2CH3); 1.50 540
(m, 2H, −NCH2CH2CH2CH3); 4.06 (t, 2H, −NCH2CH2CH2CH3); 2.21 541
(s, 3H, 5-CH3); 2.54 (s, 3H, 3-CH3); 6.51 (s, 1H, CH); 7.53 (m, 2H, Ph); 542
7.71 (m, 3H, Ph). 13C NMR (75 MHz, CDCl3, ppm): δ = 11.80; 12.05; 543
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014

M.C. Özdemir, B. Özgün / Journal of Molecular Liquids xxx (2014) xxx–xxx
7
544 12.99; 19.23; 30.66; 47.18; 108.57; 128.67–132.79; 147.55; 147.61. 19
F
545 NMR (282 MHz, CDCl3, ppm): δ = −72.12; −74.64. Analysis: calcd
546 for C15H21N2PF6: C 48.13, H 5.65, N 7.48. Found: C 47.99, H 5.47, N
547 7.30. TOF MS (ES+) m/z calcd. for C15H21N2: 229.1705. Found:
548 229.1700. TOF MS (ES−) m/z calcd. for PF6: 144.9642. Found: 144.9647.
Appendix A. Supplementary data
596
This material includes 1H NMR, 13C NMR, and 19F NMR spectra; 597
TGA curves, DSC thermograms, and cyclic voltammograms of all the 598
pyrazolium salts. Supplementary data to this article can be found online 599
at http://dx.doi.org/10.1016/j.molliq.2014.10.014.
600
549 4.6.5. 1-Phenyl-3,5-dimethyl-2-pentylpyrazolium hexafluorophosphate
550 (4e)
551
Yield: 90%, white solid. IR (ATR, cm−1) νmax = 3078, 2958–2868,
References
601
552 1596, 1564, 1495, 824, 766. 1H NMR (300 MHz, CDCl3, ppm): δ = 0.78
553 (t, 3H, −NCH2CH2CH2CH2CH3); 1.14 (m, 4H, −NCH2CH2CH2CH2CH3);
554 1.52 (m, 2H, −NCH2CH2CH2CH2CH3); 4.06 (t, 2H, –NCH2CH2
555 CH2CH2CH3); 2.21 (s, 3H, 5-CH3); 2.55 (s, 3H, 3-CH3); 6.52 (s, 1H, CH);
556 7.53 (m, 2H, Ph); 7.71 (m, 3H, Ph). 13C NMR (75 MHz, CDCl3, ppm):
557 δ = 11.83; 12.06; 13.49; 21.53; 27.98; 28.37; 47.44; 108.61;
558
559
560
561
562
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563 4.6.6. 1-Phenyl-3,5-dimethyl-2-hexylpyrazolium hexafluorophosphate (4f)
564
Yield: 90%, white solid. IR (ATR, cm−1) νmax = 3076, 2969–2861,
565 1593, 1564, 1495, 824, 764. 1H NMR (300 MHz, CDCl3, ppm): δ =
566 0.81 (t, 3H, –NCH2CH2CH2CH2CH2CH3); 1.13 (m, 6H, –NCH2CH2
567 CH2CH2CH2CH3); 1.52 (m, 2H, –NCH2CH2CH2CH2CH2CH3); 4.08
568 (t, 2H, –NCH2CH2CH2CH2CH2CH3); 2.22 (s, 3H, 5-CH3); 2.56 (s, 3H,
569 3-CH3); 6.51 (s, 1H, CH); 7.55 (m, 2H, Ph); 7.72 (m, 3H, Ph). 13C
570 NMR (75 MHz, CDCl3, ppm): δ = 11.80; 12.00; 13.67; 22.02;
571 25.55; 28.60; 30.47; 47.40; 108.56; 128.67–132.72; 147.46; 147.56.
572 19F NMR (282 MHz, CDCl3, ppm): δ = −72.23; −74.75. Analysis:
573 calcd for C17H25N2PF6: C 50.75, H 6.26, N 6.96. Found: C 50.85, H
574 6.02, N 7.03. TOF MS (ES+) m/z calcd. for C17H25N2: 257.2018.
575 Found: 257.2013. TOF MS (ES−) m/z calcd. for PF6: 144.9642.
576 Found: 144.9642.
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638
639
578
579
580
581
582
583
584
585
586
587
588
589
Yield: 85%, pinky solid. IR (ATR, cm−1) νmax = 3076, 2970–2863,
1595, 1562, 1496, 826, 764. 1H NMR (300 MHz, CDCl3, ppm): δ = 0.84
(t, 3H, −NCH2CH2CH2CH2CH2CH2CH3); 1.12 (m, 8H, –NCH2CH2CH2CH2
CH2CH2CH3); 1.52 (m, 2H, −NCH2CH2CH2CH2CH2CH2CH3); 4.07 (t, 2H,
–NCH2CH2CH2CH2CH2CH2CH3); 2.22 (s, 3H, 5-CH3); 2.56 (s, 3H, 3-CH3);
6.52 (s, 1H, CH); 7.54 (m, 2H, Ph); 7.72 (m, 3H, Ph). 13C NMR (75 MHz,
CDCl3, ppm): δ = 11.92; 12.15; 13.93; 22.34; 25.95; 28.12; 28.77;
31.23; 47.46; 108.61; 128.76–132.80; 147.54; 147.55. 19F NMR
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C18H27N2PF6: C 51.92, H 6.54, N 6.73. Found: C 52.16, H 6.48, N 6.83.
TOF MS (ES+) m/z calcd. for C18H27N2: 271.2174. Found: 271.2168. TOF
MS (ES−) m/z calcd. for PF6: 144.9642. Found: 144.9640.
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592 sity (Project no. 05/2010-93) for supporting this study. Melek Canbulat
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662
Please cite this article as: M.C. Özdemir, B. Özgün, Phenyl/alkyl-substituted-3,5-dimethylpyrazolium ionic liquids, J. Mol. Liq. (2014), http://
dx.doi.org/10.1016/j.molliq.2014.10.014