The Volumetric and Transport Properties of 1-Ethyl-3-Methylimidazolium Trifluoromethanesulfonate Ionic Liquid and Propylene Carbonate Binary System

Article abstract of DOI:10.1007/s10953-019-00842-w

In the present work, a new binary mixture system composed of the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][CF₃SO₃]) and propylene carbonate (PC) was prepared. The densities, dynamic viscosities, and electrical conductivities of ([Emim][CF₃SO₃] + PC) were measured over the whole concentration range (mole fractions of IL from 0 to 1) for temperatures from 288.15 to 353.15?K. The excess molar volumes (V^E) and viscosity deviations (Δη) of the binary systems were calculated to characterize the volume contraction and intermolecular interactions in the mixture system, and both were correlated with the Redlich–Kister polynomial equation. The Vogel–Fulcher–Tamman equation was used to describe the temperature dependences of the dynamic viscosities and the electrical conductivities of the binary system. Further, density functional theory calculations were employed to obtain the structure, energy, and COSMO charge distributions of the cation and anion of the IL and the PC molecule, and the intermolecular interactions in the binary mixture system were evaluated.

Full text of DOI:10.1007/s10953-019-00842-w

Journal of Solution Chemistry
https://doi.org/10.1007/s10953-019-00842-w
The Volumetric and Transport Properties
of 1‑Ethyl‑3‑Methylimidazolium Triꢀuoromethanesulfonate
Ionic Liquid and Propylene Carbonate Binary System
1
1
2
1
2
Ying Wei · Wenbo Zhang · Xinyuan Zhang · Huige Yang · Qingguo Zhang
Received: 18 June 2018 / Accepted: 6 October 2018
©
Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract
In the present work, a new binary mixture system composed of the ionic liquid 1-ethyl-
-methylimidazolium triꢀuoromethanesulfonate ([Emim][CF SO ]) and propylene carbon-
3
3
3
ate (PC) was prepared. The densities, dynamic viscosities, and electrical conductivities of
(
[Emim][CF SO ]+PC) were measured over the whole concentration range (mole frac-
3 3
tions of IL from 0 to 1) for temperatures from 288.15 to 353.15 K. The excess molar vol-
E
umes (V ) and viscosity deviations (Δη) of the binary systems were calculated to character-
ize the volume contraction and intermolecular interactions in the mixture system, and both
were correlated with the Redlich–Kister polynomial equation. The Vogel–Fulcher–Tam-
man equation was used to describe the temperature dependences of the dynamic viscosities
and the electrical conductivities of the binary system. Further, density functional theory
calculations were employed to obtain the structure, energy, and COSMO charge distribu-
tions of the cation and anion of the IL and the PC molecule, and the intermolecular interac-
tions in the binary mixture system were evaluated.
Keywords Ionic liquid · Binary system · Triꢀuoromethanesulfonate · Physico-chemical
properties · Intermolecular interaction
1
Introduction
Ionic liquids (ILs), which are composed solely of organic cations and organic or inorganic
anions [1–4], have several distinguished properties such as a large liquid range, minuscule
vapor pressure, miscibility, high thermally stability, broad electrochemical windows, recy-
clability, etc. [5, 6]. Due to their superior properties, ILs are generally considered safer
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1095
3
-019-00842-w) contains supplementary material, which is available to authorized users.
*
Qingguo Zhang
zhangqingguo@bhu.edu.cn
1
2
College of Chemistry and Chemical Engineering, Bohai University, Jinzhou 121013, Liaoning,
China
College of New Energy, Bohai University, Jinzhou 121013, Liaoning, China
Vol.:(0123
1
456789)
3

Journal of Solution Chemistry
and better than traditional organic solvents, and many diꢁerent families of ILs have been
used in chemistry, biology, materials science, chemical engineering, and other industrial
processes [7–10]. For example, Yang, et al. investigated kinetic eꢁects on pressure-induced
phase transitions of [Emim][CF SO ] with diꢁerent compression rates [11]. Molecular
3
3
structures and interactions in [Emim][CF SO ] were reported by Materny et al. [12]. Mar-
3
3
tínez-Andreu et al. reported the acoustical and volumetric properties of [Emim][CF SO ]
3
3
and two polar solvent (a protic one, 2-propanol, and an aprotic one, tetrahydrofuran) binary
mixtures over the whole range of compositions [13].
However, there is a usual limit in the ILs applications due to their relatively high viscos-
ity. Combining the ILs with other low viscosity components can be considered as a method
to decrease the viscosity and yield a liquid mixture system with low viscosity, low cost,
and low toxicity [14, 15]. Then, in order to clarify the nature of the IL-based mixture sys-
tems, a detailed knowledge of the physical, thermodynamic, and transport properties of the
ILs (density, viscosity, and conductivity, etc.) is very essential for further applications [16,
1
7]. Among many kinds of ILs, the ILs with the triꢀuoromethanesulfonate anion show the
characteristics of strong solubility, good catalytic property, and eꢁective corrosion inhibi-
tion in both academic applications and industry [12, 18].
In the present work, the IL 1-ethyl-3-methylimidazolium triꢀuoromethanesulfonate
−
(
[Emim][CF SO ]) was selected due to the good thermal stability of the [CF SO ] anion,
3
3
3
3
and it was synthesized by a two-step method and characterized by infrared spectroscopy
1
(
IR), elemental analysis (EA), and proton nuclear magnetic resonance ( HNMR). To
decrease the viscosity of the IL, propylene carbonate (PC), one of the most commonly
used solvents for many industrial processes, was used as the cosolvent to prepare a new
binary system over the whole mole fraction range [19, 20]. To our knowledge, experi-
mental density, viscosity, and conductivity measurements for the binary system [Emim]
[
CF SO ]+PC have not been well studied in the literature, especially the volumetric and
3 3
transport properties in which we are most interested. Herein, the physico-chemical proper-
ties of density, viscosity, and conductivity of the binary system are reported over the whole
composition range from temperatures 288.15 to 353.15 K. The excess molar volumes of
E
the mixtures, V , and the parameters of viscosity deviation, Δη, from 293.15 to 353.15 K
were calculated and ꢂtted with the Redlich–Kister equation. The observed changes of these
excess/deviation parameters can help us to understand the interactions among the compo-
nent molecules of the binary mixture [21]. The temperature dependences of viscosity and
conductivity are graphically described by the Vogel–Fulcher–Tamman (VFT) equation.
Further, the DFT calculation combined with COSMO–RS methodology are employed to
obtain the optimized structures, charge distributions, energies, and hydrogen bonds of par-
ticles in the mixtures, which can characterize the intermolecular interactions between the
IL and the PC molecules in the binary systems.
2
Experimental
2
.1 Materials
Bromoethane (98%) was purchased from Sinopharm Co. (China), while the N-methylimi-
dazole (99%) was purchased from Zhejiang Doubleport Co. Ltd. (China). Before use, the
materials were puriꢂed by distillation. Also, sodium triꢀuoromethanesulfonic (98%) was
purchased from Aladdin Reagent Co. (China) and puriꢂed by re-crystallization from water.
1
3

Journal of Solution Chemistry
C2H5
H3C
H3C
C2H5
H3C
N
N
N
N
NaCF SO3
CH3COCH3
N
N
3
C2H5Br
CF3SO3
NaBr
Br
Scheme 1 Synthesis route for [Emim][CF SO ] IL
3
3
Fig. 1 The structures of [Emim]
CF SO ] (a) and PC (b)
[
3
3
The PC was purchased from Aladdin Reagent Co. (China) with mass fraction purity of 99
wt% and dried by 4 Å molecular sieves.
2
.2 Preparation
The [Emim][CF SO ] was prepared according to the procedure described in previous work
3
3
[
22, 23]; the synthesis route of this IL is shown in Scheme 1. All synthetic processes were
conducted under a dry nitrogen atmosphere. Before the measurements, the IL was addi-
tionally puriꢂed by vacuum treatment at T=318.15 K to remove moisture and volatile
components.
1
The [Emim][CF SO ] was characterized by IR, HNMR and elemental analysis. The
3
3
purity of the [Emim][CF SO ] was approximately 99% [24, 25]. (See the Supplementary
3
3
Material.) The water content was determined by Karl–Fischer titration (ET08, Mettler
EasyPlus), showing that the mass fraction of water was less than 0.02 wt%. Measurement
−
of the residual Br was carried out by titration with AgNO /HNO solution and the ꢂnal
3
3
content was approximately 0.005 wt%. All experiments were performed under a dry nitro-
gen atmosphere. The structures of [Emim][CF SO ] and PC are shown in Fig. 1.
3
3
All anhydrous solutions of [Emim][CF SO ]+PC were prepared gravimetrically over
3
3
the whole concentration range in molar fraction. The mole fractions of IL(x ) in the mix-
IL
ture ranged from 0 to 1 (0.0999, 0.1999, 0.3005, 0.3998, 0.5001, 0.6010, 0.6987, 0.8004
and 0.8998). An analytical balance (type FA2004 N, Shanghai Bilon Co.) with a precision
−
4
of 1×10 g was used in the solution preparation process. The uncertainty in mole frac-
tions is estimated to be less than 0.0001.
2
.3 Measurements
The densities of [Emim][CF SO ] were measured using a Mettler Toledo DM 45 density
3
3
−
5
−3
meter with a precision of 10 g·cm . The samples of ionic liquid were injected into the
measurement cell using a gas tight syringe to avoid water absorption. The density meter
was calibrated with water and ultrapure dry air before performing the measurements, and
−
3
the uncertainty is 0.0002 g·cm for the density and 0.01 K for the temperature.
Viscosities of the samples were measured by an Anton Paar SVM3000 automated vis-
cometer which uses the rolling-ball principle. The uncertainty of the viscosity measure-
ment is within 0.03 mPa·s. Calibration was carried out using ultrapure water and viscosity
standard oils (No. H117, Anton Paar Co.).
1
3

Journal of Solution Chemistry
The conductivities of the samples were carried out by a Mettler Toledo SG3 conductiv-
®
−1
ity meter operating with an InLab 738 conductivity probe (nominal 0.57 cm ± 20% cell
constant); the measurement frequency and voltage of the conduction were 50 Hz and 6 V,
respectively. It was calibrated with an aqueous KCl solution under atmosphere pressure in
the temperature range 288.15–343.15 K. The uncertainty in the conductivity measurements
−
1
was estimated to be 0.05 mS·cm . The temperature was controlled by a thermostat with an
uncertainty of 0.05 K. All experimental results are listed in Table 1.
2
.4 Calculations
COSMO-RS is one of the best examples of a simulation-based model. It is a relatively new
prediction method for activity coeꢃcients and other thermodynamic properties [26]. TUR-
BOMOLE is a quantum chemical program package of COSMO-RS. Presently, TURBO-
MOLE is one of the fastest and most stable codes available for standard quantum chemical
applications [27].
In this work, each 3D-structure and energy of the investigated ionic liquid complexes
was calculated by Turbomole through the COSMO–RS methodology [28] based on the
DFT calculations. The software TURBOMOLE 6.6 program package at the TZVP level
was used for the quantum-chemical calculations to predict the electronic density and
molecular geometry for each studied compound [29]. The structural characteristics and the
H–bond interactions were optimized and evaluated.
3
Results and Discussion
3
.1 Volumetric Properties
The densities of pure [Emim][CF SO ], pure PC, and the binary system [Emim]
3
3
[
CF SO ]+PC were determined, and the values of the pure IL were compared to liter-
3 3
ature data. For example, the measured value of pure [Emim][CF SO ] in this work was
3
3
−
3
−3
1
1
.38292 g·cm at 298.15 K, which is similar to the reported values (1.38358 g·cm [13],
−
3
.38228 g·cm [30]). The results in Table 1 show that the densities of pure IL and [Emim]
[
CF SO ]+PC mixtures are temperature dependent (see Fig. 2). Densities from this work
3 3
and literature values are displayed in Table 1. The small deviations shown in Table 1 indi-
cate that the experimental results are consistent with the literature data and hence the meth-
ods used in this work are valid.
From Fig. 2, the densities of pure [Emim][CF SO ] are larger than those of the binary
3
3
mixtures, and the densities of the mixtures decrease as the amount of the organic solvent
increases. That means the densities of the binary mixtures follow a decreasing trend with
increased temperature and addition of PC. That shows a similar trend to other reported
binary systems [13, 18, 31].
The excess functions express the deviation of binary system from ideal mixing behavior.
E
The excess molar volumes (V ) can be calculated from experimental data [32] as:
ꢀ
ꢁ
x M + x M
1
x1M
x2M
2
E
V =
1
2
2
1
−
+
(1)
ꢀ
ꢀ
ꢀ
1
2
where x and x are mole fractions of the components IL and PC, ρ and ρ are the densities
1
2
1
2
of pure IL and PC, and ρ is the density of the mixtures. The M and M are molar masses
1
2
1
3

Journal of Solution Chemistry
1
3

Journal of Solution Chemistry
1
3

Journal of Solution Chemistry
Fig. 2 Plot of density (ρ) against
temperature in the [Emim]
[
CF SO ]+PC binary system in
3 3
the temperature range (288.15–
53.15) K
3
E
of pure IL and PC. The V values of the [Emim][CF SO ]+PC binary system are listed in
3
3
E
Table 2. Furthermore, the composition dependences of V of the [Emim][CF SO ]+PC
3
3
binary system at several temperatures were represented with a Redlich–Kister type
equation:
3
ꢀ
ꢁ
ꢂ
i
E
V = x x
A x − x
i
(2)
1
2
1
2
i=0
where A (i=0, 1, 2, 3) are adjustable parameters of the R–K equation from 293.15 to
i
3
53.15 K, which can be obtained by least-squares analysis. In the present investigation the
“
i” values range from 0 to 3, which is a common range for most IL binary systems [31, 32].
The correlated results are given in Table 3, along with standard deviations (SD). The devi-
ations between the experimental and calculated values are deꢂned by following equation:
1
ꢀ
ꢁ
2
2
⎡
⎢
⎢
E
cal
E
exp
⎤
⎥
⎥
n
V
− V
�
SD =
(3)
(
n − p)
⎢
⎣
i=1
⎥
⎦
where n is the number of experimental points and p is the number of parameters. It
becomes apparent that the R–K equation provides a good characterization of the change in
E
V with composition for a binary system [32].
Figure 3 shows the inꢀuences of the molar fraction on the excess molar volumes at
E
diꢁerent temperatures. At all proportions, the values of V are negative over the entire
composition range, present the same trend at all temperatures, and reach a minimum
E
at x ≈ 0.5. The V values are inꢀuenced by intermolecular interactions occurring in
IL
the binary system involving diꢁerences of composition, molecular structure, and shape
E
of molecules [5]. It is believed that the negative V values arise from interactions like
dipole–dipole interaction, dispersion forces or hydrogen bonding [5], as well as a more
eꢃcient packing and/or attractive interactions that occurred when the [Emim][CF SO ]
3
3
and PC were mixed [33].
1
3

Journal of Solution Chemistry
1
3

Journal of Solution Chemistry
Table 3 Adjustable parameters
T (K)
A0
A1
A2
A3
SD
of the Redlich–Kister equation
E
for excess molar volumes (V )
V (cm ·mol−1)
E
3
and viscosity deviations (∆η) for
2
88.15
– 4.240
– 4.235
– 4.258
– 4.270
– 4.350
– 4.339
– 4.442
– 4.470
– 4.508
– 4.662
– 4.713
– 4.777
– 4.909
– 4.915
– 0.406
– 0.407
– 0.367
– 0.352
– 0.238
– 0.299
– 0.162
– 0.187
– 0.124
0.175
0.267
0.253
0.105
0.353
– 0.059
– 0.313
– 0.485
– 0.470
– 0.481
– 0.565
– 0.661
– 0.763
– 0.792
– 0.593
– 0.696
– 0.687
– 0.548
– 0.849
– 0.911
– 0.589
– 0.619
– 0.875
– 0.974
– 0.933
– 1.060
– 0.937
– 1.173
– 1.702
– 1.970
– 2.070
– 1.224
– 1.920
0.029
0.032
0.038
0.038
0.037
0.040
0.041
0.044
0.045
0.048
0.051
0.055
0.047
0.053
the [Emim][CF SO ]+PC binary
3
3
system, along with the standard
deviations (SD)
293.15
298.15
303.15
308.15
313.15
318.15
323.15
328.15
333.15
338.15
343.15
348.15
353.15
∆
2
η (mPa·s)
88.15
93.15
98.15
03.15
08.15
13.15
18.15
23.15
28.15
33.15
38.15
43.15
48.15
53.15
– 49.947
– 39.758
– 31.809
– 26.192
– 21.832
– 18.334
– 15.551
– 13.166
– 11.567
– 10.161
– 8.961
– 9.643
– 7.063
– 3.629
– 2.225
– 0.239
0.937
1.422
1.973
1.925
2.517
2.614
2.992
2.593
2.410
1.051
2.568
1.553
2.032
2.180
4.449
1.225
1.588
0.096
0.640
-0.636
0.439
1.507
2.768
– 23.781
– 18.596
– 18.538
– 15.091
– 13.793
– 12.257
– 11.617
– 9.768
– 9.193
– 8.651
– 9.086
– 7.973
– 4.143
– 2.401
0.439
0.320
0.218
0.185
0.156
0.180
0.112
0.068
0.074
0.083
0.073
0.049
0.041
0.054
2
2
3
3
3
3
3
3
3
3
3
3
3
– 7.656
– 6.557
– 5.984
Fig. 3 Plot of excess molar
volume against molar fraction of
the [Emim][CF SO ]+PC binary
3
3
mixtures in the temperature range
(
293.15–353.15) K: black square,
2
93.15 K; red circle, 303.15 K;
blue triangle, 313.15 K; pink
inverted triangle, 323.15 K;
green diamond, 333.15 K; black
left pointing triangle, 343.15 K;
blue right pointing triangle,
3
53.15 K
1
3

Journal of Solution Chemistry
3
.2 Transport Properties
ILs are usually more viscous than traditional organic solvents, which can limit their utility.
Among all of the transport properties, viscosity and conductivity are the most critical for
applications involving the use of ILs as solvents and electrolytes [1, 4].
Figure 4a and b present the temperature dependence and mole fraction dependence of
conductivity of the binary system. When the temperature increases, the conductivity of
each component increases as well. The addition of PC leads to the growth of the conductiv-
ity of the system and reaches its maximum at x ≈0.4 in the whole temperature range. This
IL
may be caused by an appropriate amount of ions and proper ion mobility in the mixing
process [34].
The relationship between the conductivity and temperature of a binary system can be
expressed by the VFT equation that is commonly used to represent the conductivities of
ILs:
ꢀ
ꢀ
ꢁꢁ
ꢀ
= ꢀ exp −B∕ T−T
0
(4)
0
where σ is conductivity at the temperature limit, B is the quantity related to the activation
0
barrier and T is the absolute or “ideal glass transition” temperature [35, 36]. The best ꢂt-
0
2
ted parameters of σ , B, T , and the correlation coeꢃcients R are listed in Table 4. The
0
0
Fig. 4 Plots of the conductivity (a, b) and viscosity (c) against temperature and mole fraction of the binary
system. x : black square, 1; red circle, 0.8998; blue triangle, 0.8004; pink inverted triangle, 0.6987; green
IL
diamond, 0.6010; left pointing triangle, 0.5001; blue right pointing triangle, 0.3998; red star, 0.3005; open
square, 0.1999; open circle, 0.0999; open triangle, 0
1
3

Journal of Solution Chemistry
Table 4 Fitted parameter
R2
x1
σ0
B (K)
T0 (K)
values of the VFT equation
of electrical conductivity and
dynamic viscosity for the [Emim]
σ (mS·cm−1
)
1
0
0
0
0
0
0
0
0
0
0
.0000
.8998
.8004
.6987
.601
.5001
.3998
.3005
.1999
.0999
.0000
216.8
314.3
360.8
182.03
261.2
1088
9681
3119
68.55
270.5
–
708.4
916.0
1056
696.9
1006
2563
6916
2765
698.6
3599
–
78.72
33.81
– 5.550
37.18
– 47.04
– 305.7
– 04.9
– 573.0
– 192.4
867.0
–
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
–
[
CF SO ]+PC binary system
3 3
x1
η0
B (K)
T0 (K)
R2
η (mPa·s)
1
0
0
0
0
0
0
0
0
0
0
.0000
.8998
.8004
.6987
.601
.5001
.3998
.3005
.1999
.0999
.0000
0.1377
0.1540
0.1576
0.1446
0.1000
0.1650
0.0821
0.0679
0.1053
0.1760
0.5378
– 906.5
– 834.1
– 786.2
– 769.7
– 847.5
– 611.0
– 723.1
– 715.5
– 516.9
– 348.3
– 83.91
138.7
142.3
145.6
144.5
134.0
159.0
148.6
147.1
171.2
190.7
243.6
0.9999
0.9999
0.9999
0.9999
0.9999
0.9999
0.9997
0.9997
0.9996
0.9996
0.9999
ꢂtted correlation coeꢃcients of the VFT equation are all>0.9999, indicating that the VFT
equation can describe well the eꢁect of temperature on conductivity of the system.
The experimental values of the viscosity η for the [Emim][CF SO ]+PC binary system at
3
3
diꢁerent temperatures are also presented in Table 1. It is found that the η values for the [Emim]
[
CF SO ]+PC system decrease with the rise of temperature, and increase when the mole frac-
3 3
tion of [Emim][CF SO ] increases (see Fig. 4c). The Vogel–Fulcher–Tamman (VFT) method
3
3
given in Eq. 5 can be used to represent the temperature dependence of viscosity:
= ꢀ exp(−B∕(T − T ))
ꢀ
(5)
0
0
where η , B, and T are adjustable constants. The ꢂtted VFT parameters of ILs are listed in
0
0
Table 4. The ꢂtting correlation coeꢃcients are all>0.9996, indicating that the VFT equa-
tion is also suitable for describing the eꢁect of temperature on the viscosities of the ILs and
its binary system [37].
Based on the experimental values of the viscosity, the viscosity deviations of binary
mixtures were calculated by the following equation [38]:
ꢀ
ꢁ
Δꢀ = ꢀ− x ꢀ + x ꢀ
1
(6)
1
2
2
1
3

Journal of Solution Chemistry
where η and η are the viscosities of pure components 1 and 2, respectively. Thus, the ∆η
1
2
values of the [Emim][CF SO ]+PC system were obtained and also included in Table 3;
3
3
in Fig. 4 the viscosity deviations are plotted at intervals of 10 K from 293.15 to 353.15 K.
The values of Δη were correlated with a R–K type equation (Eq. 2), and the standard
deviations (SD) were calculated from Eq. 3. The values of adjustable constants and SD are
listed in Table 3.
Figure 5 shows the dependence of the viscosity deviations as a function of molar frac-
tion of [Emim][CF SO ], x , at diꢁerent temperatures. It can be seen that Δη is negative
3
3
IL
over the entire composition range and the absolute value of Δη decreases with rise of tem-
perature for the binary system as seen in Fig. 5. This decrease is due to the experimental
viscosity coming closer to the viscosity predicted by Eq. 6 when the temperature increases.
At 353.15 K, Δη approaches zero, and the experimental viscosity thus approximately
equals that of the linear mixing model. In fact, the temperature strongly inꢀuences the vis-
cosity deviations, but the observed compositions at the maximum in viscosity deviations
are found to be almost constant and independent of temperature. Furthermore, the negative
Δη values can be explained by the fact that strong dipole interactions are dominant in these
mixtures [39].
3
.3 Intermolecular Interactions in the [Emim][CF SO ] + PC Binary System
3 3
To gain more insight into the intermolecular interactions in the binary system, the DFT cal-
culations were performed following the COSMO–RS methodology [26, 27].
First, for the pure IL, the structures of the cation, anion, and ion pair were optimized
and the stable conformers were obtained. Then, a set of possible conformations of the
investigated complexes in the binary system were examined by DFT calculations. It is also
+
worth noting that there may be many more possible interaction structures for the [Emim] ,
−
[
CF SO ] , PC molecule and ion pairs. The selected structure is the most stable optimized
3
3
geometry from the number of possible mutual orientations of the interacting complexes
examined (Fig. 6 and Table 5). From the charge distribution (Table 5), it appears that the
highly localized negative charge (red surface) in oxygen atoms of the anion can form rela-
tively strong interactions.
Fig. 5 Plots of viscosity devia-
tions (Δη) against molar fraction
of the binary system at diꢁerent
temperature: black square,
2
93.15 K; red circle, 303 K;
blue upright triangle, 313.15 K;
pink inverted triangle, 323.15 K;
green diamond, 333.15 K;
left pointing black triangle,
3
43.15 K; right pointing purple
triangle, 353.15 K
1
3

Journal of Solution Chemistry
Fig. 6 Optimized structures and hydrogen bonds of the ionic liquid and its mixtures; hydrogen bonds are
shown by the dotted lines: a [Emim][CF SO ], b PC, c [Emim][CF SO ]+PC, d 2[Emim][CF SO ]+PC,
3
3
3
3
3
3
and e [Emim][CF SO ]+2PC
3
3
In the stable geometries of [Emim][CF SO ] (Fig. 6a), it was found that H-bonds can
3
3
exist between C2–H on the imidazolium ring and the O/F atom of [CF SO ] anion [40]. As
3
3
can be seen in Fig. 6c, for the [Emim] cation both the aromatic and alkyl hydrogen atoms
can work as proton donors to interact with the oxygen atoms of the [CF SO ] anion and the
3
3
oxygen atom of PC. For 2[Emim][CF SO ]+PC (Fig. 6d), H–bonding interactions exist
3
3
between the H/O atoms of PC and cation and the anion of the IL, respectively. For [Emim]
CF SO ]+2PC (Fig. 6e), there are strong H–bonding interactions between the cation/
[
3
3
anion and PC molecules. This phenomenon implied that the addition of PC may weaken
1
3

Journal of Solution Chemistry
Table 5 The COSMO-RS electronic charge distribution of [Emim][CF SO ], PC and their mixtures
3
3
[
Emim][CF SO
3 3
]
PC
3 3
[Emim][CF SO ] + PC
[
Emim][CF
3
SO
3
] + 2PC
3 3
2[Emim][CF SO ] + PC
the interactions between the cation and anion and lead to a decrease of the viscosity of ILs
41].
[
+
−
By comparison of the interaction energies, the interaction energy of [Emim] –[CF SO ]
3
3
is lower than the energies of the mixture conꢂguration, which implies that the mixing pro-
cess of the [Emim][CF SO ] and PC is entropically favorable (Fig. 6) [42].
3
3
4
Conclusion
In this paper, a new IL-based binary system [Emim][CF SO ]+PC was prepared. The den-
3
3
sities, viscosities and conductivities of the mixture system were measured from 288.15
E
to 353.15 K. The excess molar volumes (V ) were calculated and correlated with the
E
Redlich–Kister equation. The negative V values indicate that more eꢃcient packing and/or
attractive interactions occur in this system. The viscosity deviations (Δη) were also calculated
and correlated with the R–K equation. The changes with temperature for the viscosity and
the conductivity were described by the Vogel–Fulcher–Tamman equation, and it gave a very
good correlation. Density functional theory (DFT) calculations and COSMO–RS methodol-
ogy were performed to study the intermolecular interactions in the binary system.
1
3

Journal of Solution Chemistry
Acknowledgements This work was ꢂnancially supported by the National Nature Science Founda-
tion of China (Nos. 21503020 and 21373002), the Nature Science Foundation of Liaoning Province (No.
2
01602016), the Doctoral Fund of Liaoning Province of China (No. 201601347), and Program for Liaoning
Excellent Talents in University, China (LJQ2015099).
References
1
2
3
4
.
.
.
.
Welton, T.: Room-temperature ionic liquids: solvents for synthesis and catalysis. Chem. Rev. 99,
2
071–2084 (1999)
Ye, C., Liu, W., Chen, Y., Yu, L.: Room-temperature ionic liquids: a novel versatile lubricant.
Chem. Commun. 21, 2244–2245 (2001)
Plechkova, N.V., Seddon, K.R.: Applications of ionic liquids in the chemical industry. Chem. Soc.
Rev. 37, 123–150 (2008)
MacFarlane, D.R., Forsyth, M., Howlett, P.C., Pringle, J.M., Sun, J.Z., Annat, G., Neil, W., Izgoro-
dina, E.I.: Ionic liquids in electrochemical devices and processes: managing interfacial electro-
chemistry. Acc. Chem. Res. 40, 1165–1173 (2007)
5
6
.
.
Requejo, P., González, E., Macedo, E., Domínguez, Á.: Eꢁect of the temperature on the physical
properties of the pure ionic liquid 1-ethyl-3-methylimidazolium methylsulfate and characterization
of its binary mixtures with alcohols. J. Chem. Thermodyn. 74, 193–200 (2014)
Zhong, Y., Wang, H., Diao, K.: Densities and excess volumes of binary mixtures of the ionic liq-
uid 1-butyl-3-methylimidazolium hexaꢀuorophosphate with aromatic compound at T= (298.15 to
3
13.15) K. J. Chem. Thermodyn. 39, 291–296 (2007)
7
8
.
.
Zhao, H., Song, Z.Y., Olubajo, O.: High transesteriꢂcation activities of immobilized proteases in
new ether-functionalized ionic liquids. Biotechnol. Lett. 32, 1109–1116 (2010)
Buriol, L., Frizzo, C.P., Prola, L.D., Moreira, D.N., Marzari, M.R., Scapin, E., Zanatta, N., Bona-
corso, H.G., Martins, M.A.: Synergic eꢁects of ionic liquid and microwave irradiation in promoting
triꢀuoromethylpyrazole synthesis. Catal. Lett. 141, 1130–1135 (2011)
9
.
Munoz, M., Domínguez, C.M., de Pedro, Z.M., Quintanilla, A., Casas, J.A., Rodriguez, J.J.: Ionic
liquids break down by Fenton oxidation. Catal. Today 240, 16–21 (2015)
1
1
0. Liang, X.: Synthesis of a cross linked polymer with a benzyl(triphenyl)phosphonium ionic liquid
moiety and its catalytic activity. RSC Adv. 120, 99448–99453 (2015)
1. Li, H.N., Wang, Z., Chen, L.C., Wu, J., Huang, H.J., Yang, K., Wang, Y.Q., Su, L., Yang, G.:
Kinetic eꢁect on pressure-induced phase transitions of room temperature ionic liquid, 1-ethyl-
3
-methylimidazolium triꢀuoromethanesulfonate. J. Phys. Chem. B 119, 14245–14251 (2015)
1
1
2. Singh, D.K., Rathke, B., Kiefer, J., Materny, A.: Materny, molecular structure and interactions in
the ionic liquid 1-ethyl-3-methylimidazolium triꢀuoromethanesulfonate. J. Phys. Chem. A 120,
6
274–6286 (2016)
3. Vercher, E., Orchillés, A.V., Llopis, F.J., González-Alfaro, V., Martínez-Andreu, A.: Ultrasonic and
volumetric properties of 1-ethyl-3-methylimidazolium triꢀuoromethanesulfonate ionic liquid with
2
-propanol or tetrahydrofuran at several temperatures. J. Chem. Eng. Data 56, 4633–4642 (2011)
1
1
4. Podgoršek, A., Jacquemin, J., Pádua, A.A.H., Gomes, M.F.C.: Mixing enthalpy for binary mixtures
containing ionic liquids. Chem. Rev. 116, 6075–6106 (2016)
5. Reddy, M.S., Raju, K.T.S., Rao, A.S., Sharmila, N., Babu, B.H.: Study of thermophysical prop-
erties of the binary mixtures of ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate and 2-pro-
poxyethanol from T = (298.15 to 328.15) K at atmospheric pressure. J. Chem. Thermodyn. 101,
1
39–149 (2016)
1
1
1
1
6. Sanchez, L.G., Espel, J.R., Onink, F., Meindersma, G.W., Haan, A.B.D.: Density, viscosity, and
surface tension of synthesis grade imidazolium, pyridinium, and pyrrolidinium based room tem-
perature ionic liquids. J. Chem. Eng. Data 54, 2803–2812 (2009)
7. Anouti, M., Vigeant, A., Jacquemin, J., Brigouleix, C., Lemordant, D.: Volumetric properties, vis-
cosity and refractive index of the protic ionic liquid, pyrrolidiniumoctanoate, in molecular solvents.
J. Chem. Thermodyn. 42, 834–845 (2010)
8. Vercher, E., Miguel, P.J., Llopis, F.J., Orchillés, A.V., Martínez-Andreu, A.: Volumetric and acous-
tic properties of aqueous solutions of triꢀuoromethanesulfonate-based ionic liquids at several tem-
peratures. J. Chem. Eng. Data 57, 1953–1963 (2012)
9. Wolꢁ, C., Jeong, S., Paillard, E., Balducci, A., Passerini, S.: High power, solvent-free electrochem-
ical double layer capacitors based on pyrrolidinium dicyanamide ionic liquids. J. Power Sources
2
93, 65–70 (2015)
1
3

Journal of Solution Chemistry
2
2
2
2
2
2
0. Zhang, T., Fuchs, B., Secchiaroli, M., Wohlfahrt-Mehrens, M., Dsoke, S.: Electrochemical behavior
and stability of a commercial activated carbon in various organic electrolyte combinations contain-
ing Li-salts. Electrochim. Acta 218, 163–173 (2016)
1. Sekiguchi, K., Atobe, M., Fuchigami, T.: Electrooxidative polymerization of aromatic compounds
in 1-ethyl-3-methylimidazolium triꢀuoromethanesulfonate room-temperature ionic liquid. J. Elec-
troanal. Chem. 557, 1–7 (2003)
2. Zhang, Q.G., Wang, N.N., Wang, S.L., Yu, Z.W.: Hydrogen bonding behaviors of binary systems
containing the ionic liquid 1-butyl-3-methylimidazolium triꢀuoroacetate and water/methanol. J.
Phys. Chem. B 115, 11127–11136 (2011)
3. Zhang, Q.G., Wang, N.N., Wang, S.L., Yu, Z.W.: The thermodynamic estimation and viscosity,
electrical conductivity characteristics of 1-alkyl-3-methylimidazolium thiocyanate ionic liquids. Z.
Phys. Chem. 228, 851–867 (2014)
4. Zhang, Q.G., Xu, T.T., Zhang, X.Y., Yang, H.G., Zhang, W.B.: The thermodynamic and excess
properties of trialkyl-substituted imidazolium-based ionic liquids with thiocyanate and its binary
systems with acetonitrile. J. Chem. Eng. Data 63, 1408–1418 (2018)
5. Vieira, N.S.M., Luis, A., Reis, P.M., Carvalho, P.J., Lopes-da-Silva, J.A., Esperanca, J.M.S.S.,
Araújo, J.M.M., Rebelo, L.P.N., Freire, M.G., Pereiro, A.B.: Fluorination eꢁects on the thermody-
namic, thermophysical and surface properties of ionic liquids. J. Chem. Thermodyn. 97, 354–361
(
2016)
2
2
6. Putnam, R., Taylor, R., Klamt, A., Eckert, F., Schiller, M.: Prediction of inꢂnite dilution activity
coeꢃcients using COSMO-RS. Ind. Eng. Chem. Res. 42, 3635–3641 (2003)
7. Turbomole, a development of university of Karlsruhe and Forschungszentrum Karlsruhe GmbH
v6.6 2014; TURBOMOLE GmbH: 2007; available from http://www.turbomole.com. Order date:
1
0-11-2014 (permanent license)
2
8. Jacquemin, J., Feder-Kubis, J., Zorębski, M., Grzybowska, K., Chorążewski, M., Hensel-Bielówka,
S., Zorebski, E., Paluch, M., Dzida, M.: Structure and thermal properties of salicylate-based-protic
ionic liquids as new heat storage media COSMO-RS structure characterization and modeling of
heat capacities. Phys. Chem. Chem. Phys. 16, 3549–3557 (2014)
2
3
3
3
3
9. Nockemann, P., Thijs, B., Pittois, S., Thoen, J., Glorieux, C., Van Hecke, K., Van Meervelt, L.,
Kirchner, B., Binnemans, K.: Task-speciꢂc ionic liquid for solubilizing metal oxides. J. Phys.
Chem. B 110, 20978–20992 (2006)
0. Reddy, M.S., Khan, I., Raju, K.T.S., Suresh, P., Babu, B.H.: The study of molecular interactions in
1
-ethyl-3-methylimidazolium triꢀuoromethanesulfonate + 1-pentanol from density, speed of sound
and refractive index measurements. J. Chem. Thermodyn. 98, 298–308 (2016)
1. Zhang, Z.B., Zhou, Q., Lu, X.M., Qiao, C.Z., Zhang, S.J.: Densities and viscosities of binary mix-
tures containing 1,3-dimethylimidazolium dimethylphosphate and alcohols. J. Chem. Eng. Data 59,
2
377–2388 (2014)
2. Zhang, Q.G., Cai, S.Y., Zhang, W.B., Lan, Y.Y., Zhang, X.Y.: Density, viscosity, conductivity,
refractive index and interaction study of binary mixtures of the ionic liquid 1-ethyl-3-methylimida-
zolium acetate with methyldiethanolamine. J. Mol. Liq. 233, 471–478 (2017)
3. Castro, M.C., Arce, A., Soto, A., Rodríguez, H.: Thermophysical characterization of the mixtures
of the ionic liquid 1-ethyl-3-methylimidazolium acetate with 1-propanol or 2-propanol. J. Chem.
Eng. Data 61, 2299–2310 (2016)
3
3
4. Jänes, A., Eskusson, J., Thomberg, T., Romann, T., Lust, E.: Ionic liquid-1,2-dimethoxyethane mix-
ture as electrolyte for high power density supercapacitors. J. Energy Chem. 25, 609–614 (2016)
5. Xu, L., Cui, X.B., Zhang, Y., Feng, T.Y., Lin, R.R., Li, X.B., Jie, H.M.: Measurement and cor-
relation of electrical conductivity of ionic liquid [EMIM][DCA] in propylene carbonate and
γ-butyrolactone. Electrochim. Acta 174, 900–907 (2015)
3
3
3
3
6. Liu, Q.S., Li, P.P., Welz-Biermann, U., Chen, J., Liu, X.X.: Density, dynamic viscosity, and electri-
cal conductivity of pyridinium-based hydrophobic ionic liquids. J. Chem. Thermodyn. 66, 88–94
(
2013)
7. Domańska, U., Królikowska, M.: Density and viscosity of binary mixtures of {1-butyl-3-methylim-
idazolium thiocyanate + 1-heptanol, 1-octanol, 1-nonanol, or 1-decanol}. J. Chem. Eng. Data 55,
2
994–3004 (2010)
8. Zhang, L.F., Lu, X.X., Ye, D.F., Guo, Y.S., Fang, W.J.: Density and viscosity for binary mixtures
of the ionic liquid 2,2-diethyl-1,1,3,3-tetramethylguanidinium ethyl sulfate with water, methanol, or
ethanol. J. Chem. Eng. Data 61, 1023–1031 (2016)
9. Qian, W., Xu, Y.J., Zhu, H.Y., Yu, C.H.: Properties of pure 1-methylimidazoliumacetate ionic liq-
uid and its binary mixtures with alcohols. J. Chem. Thermodyn. 49, 87–94 (2012)
1
3

Journal of Solution Chemistry
4
4
4
0. Zheng, Y.Z., Zhou, Y., Deng, G., Yu, Z.W.: Hydrogen-bonding interactions between a nitrile-based
functional ionic liquid and DMSO. J. Mol. Struct. 1124, 207–215 (2016)
1. Zhang, X.C., Huo, F., Liu, X.M., Dong, K., He, H.Y., Yao, X.Q., Zhang, S.J.: Inꢀuence of micro-
structure and interaction on viscosity of ionic liquids. Ind. Eng. Chem. Res. 54, 3505–3514 (2015)
2. He, H.Y., Chen, H., Zheng, Y.Z., Zhang, S.J., Yu, Z.W.: Hydrogen-bonding interactions between a
pyridinium-based ionic liquid [C Py][SCN] and dimethyl sulfoxide. Chem. Eng. Sci. 121, 169–179
4
(
2015)
4
4
3. Fox, E.T., Paillard, E., Borodin, O., Henderson, W.A.: Physicochemical properties of binary ionic
liquid–aprotic solvent electrolyte mixtures. J. Phys. Chem. C 117, 78–84 (2012)
4. Aranowski, R., Cichowska-Kopczyńska, I., Dębski, B., Jasiński, P.: Conductivity and viscosity changes
of imidazolium ionic liquids induced by H O and CO . J. Mol. Liq. 221, 541–546 (2016)
2
2
Publisher’s Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and
institutional aꢃliations.
1
3