Influence of Cation Size on the Ionicity, Fluidity, and Physiochemical Properties of 1,2,4-Triazolium Based Ionic Liquids

Article abstract of DOI:10.1021/acs.jpcb.6b03669

Interpreting the physiochemical properties and structure-property correlations of ionic liquids (ILs) is a key to the enlargement of their optimized structures for specific applications. In this work, a series of ILs based on 1-alkyl-1,2,4-triazolium cation with trifluoromethanesulfonate anion were synthesized and the effect of cation and temperature on physiochemical properties such as density, viscosity, speed of sound, conductivity, and rheology was studied. Temperature dependence densities were correlated with the densities estimated by the Gardas and Coutinho model, whereas viscosity and molar conductivity have been found to satisfy the Vogel-Tammann-Fulcher (VTF) equation over the studied temperature range 293.15-343.15 K. Further, to explore the wide range of applications, ionicity has been tested by correlating the fluidity with molar conductivity and it was found that synthesized ILs can be referred to as good ILs . Furthermore, the fluidity behavior describing the interactions between the cation and anion of ILs was investigated through their rheological properties, and the Newtonian behavior of ILs has been examined by varying the effect of shear rate on viscosity. Finally, the impact of structure variants in terms of the N-1 functionalized 1,2,4-triazole ring has been analyzed over the studied properties.

Full text of DOI:10.1021/acs.jpcb.6b03669

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Article
Influence of Cation Size on the Ionicity, Fluidity and
Physiochemical Properties of 1,2,4-Triazolium Based Ionic Liquids
Dharmendra Singh, and Ramesh L Gardas
J. Phys. Chem. B, Just Accepted Manuscript • DOI: 10.1021/acs.jpcb.6b03669 • Publication Date (Web): 09 May 2016
Downloaded from http://pubs.acs.org on May 9, 2016
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Influence of Cation Size on the
Ionicity, Fluidity and Physiochemical Properties
of 1,2,4ꢀTriazolium Based Ionic Liquids
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Dharmendra Singh and Ramesh L. Gardas*
Indian Institute of Technology Madras, Chennai 600036
*Corresponding author. Tel.: +91 44 2257 4248; fax:+91 44 2257 4202
E.mail address: gardas@iitm.ac.in; URL: http://www.iitm.ac.in/info/fac/gardas
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ
ꢀ
ꢀ
Abstract
Interpreting the physiochemical properties and structureꢀproperty correlations of ionic liquids
(
ILs) is a key to the enlargement of their optimized structures for specific applications. In this
work, a series of ILs based on 1ꢀ alkylꢀ 1,2,4ꢀ triazolium cation with trifluromethane sulfonate
anion were synthesized and studied the effect of cation and temperature on physiochemical
properties such as density, viscosity, speed of sound, conductivity and rheology. Temperature
dependence densities were correlated with the densities estimated by Gardas and Coutinho
model whereas viscosity and molar conductivity has been found to satisfy VogelꢀTammannꢀ
Fulcher (VTF) equation over studied temperature range (293.15ꢀ343.15) K. Further, to explore
the wide range of applications, ionicity has been tested by correlating the fluidity with molar
conductivity and found that synthesized ILs can be referred as “good ILs”. Furthermore, the
fluidity behavior describing the interactions between cation and anion of ILs were investigated
through their rheological properties; and the Newtonian behavior of ILs has been examined by
varying the effect of shear rate on viscosity. Finally, the impact of structure variant in terms of
Nꢀ1 functionalized 1,2,4ꢀtriazole ring has been analyzed over studied properties.
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ꢀ
Introduction
Ionic liquids (ILs) are novel solvents of greater interest as an alternative for
conventional organic solvents which have aimed at facilitating sustainable chemistry through
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their tunable properties. Among various class of ILs, the potential utilization and
applications of nitrogenꢀ rich ILs have been rapidly increased over conventional energetic
materials, mainly due to low carbon and hydrogen content and thus resulting in good oxygen
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ꢀ5
balance. Generally, nitrogenꢀ rich ILs exhibits high heat of formation, high density, with
dinitrogen as decomposition product, because of these properties such class of ILs are
considered as highly accomplished energetic materials for industrial and military
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applications. Shreeve and coworkers explored the application of nitrogenꢀ rich ILs
consisting of various families, e.g. imidazolium, picrate, urotropinium, triazolium,
tetrazolium, tetrazine etc. as ‘energetic salts’. A combination of theoretical and empirical
calculations conveyed that 5ꢀaminotetrazolatate based salts have desirable properties to be
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consigned as energetic materials. Energetic behavior of tetrazolium based ILs were
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investigated by Dong and coworker and found that on increasing the alkyl chain length,
density decreases and consequently energetic behavior of ILs was found to be reduced.
Triazolium based ILs have gained increased interest due to their potential use in energyꢀ
rich applications. Salts consisting of the triazolium moiety have been found to exhibit large
heat of formation (
= 58.5 kJ/mol), and they also possess the combination of unique properties, such as
higher densities, enhanced thermal stabilities, and reduced vapor pressure thus making them
ꢀH = 109 kJ/mol), compared to similar salts having imidazolium moiety
f
(ꢀH
f
6
,10ꢀ12
to more advantageous as compared to conventional energetic materials.
1,2,4ꢀ triazolium
salts can be used as energetic materials and efficient CO absorbents with low reaction
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enthalpy.
Strassner et al. explored the mesomeric effect to modify the alkylated or
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arylated 1,2,4ꢀtriazolium ILs for desired properties. 1ꢀalkylꢀ 1,2,4ꢀtriazolium methane
sulfonate based Brønsted acidic ILs can exhibit good catalytic activity for Mannich base
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reaction with appreciable efficiency. Additionally, –SO
3
H functionalized ILs have been
reported offering a new possibility for developing environmentallyꢀfriendly acidic catalysts
because they are flexible, nonvolatile, nonꢀcorrosive and immiscible with many organic
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solvents and could be used as dual solvents and catalysts.
In spite of wide range of applications, very few reports are available
study of structure variants and the effect of temperature on physiochemical properties of
,2,4ꢀ triazolium based ILs. Study on physiochemical properties is essential (i) to understand
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on systematic
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the geometrical configurations and intermolecular interactions of these ILs; (ii) to develop the
structureꢀproperty correlations and predictive models; and (iii) for the design of processes and
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products involving these compounds.
By considering these factors, Narita et al had shown
that how alkyl chain length can improve the performance of zwitterions as ion conductive
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matrices. In the present work, we have synthesized 1,2,4ꢀ triazolium based ILs by the Nꢀ1
alkylation of 1,2,4ꢀ triazole followed by Nꢀ4 quaternization with trifluromethane sulfonic
acid and studied their thermophysical properties, viz. density, viscosity, conductivity and
speed of sound, as a function of temperature. The experimental density data were correlated
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with the estimated density obtained by Gardas and Coutinho model, whereas experimental
viscosity and conductivity data were fitted with Vogelꢀ Tammannꢀ Fulcher (VTF) equation.
Fluidity behavior and ionicity behavior of studied ILs have been investigated through
rheological profiling methods and Walden’s rule, respectively. Furthermore, experimentally
measured and derived properties were analyzed to understand the influence of the
temperature and structure variants in cation molecular architecture of triazoliumꢀbased ILs.
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ꢀ Experimental Section
General Experimental Methods. All commercial reagents were reagent or HPLC grade
and used without further purification. Synthesized ILs was purified by using high vacuum at
60ºC. Water content has been measured by Metrohm 870 KF Titrino plus which is KF titrator
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for volumetric water content determination. H, C and DEPT NMR were recorded by
Bruker avance 500 MHz NMR instrument and chemical shift reported in parts per million
1
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using as standard solvent signal (CDCl : H, 7.26 ppm; C, 77.16 ppm). High resolution
mass spectra (HRMS) have been measured by Qꢀ Tofꢀ Mass spectrometer.
Measurement of Physiochemical Properties. Thermal stability of ILs have been
measured for NETZSH STA449 F3 Jupiter TGA instrument, which can operate in a
temperature range from 25 to 1400 ˚C. The instrument is equipped with a dual furnace made
up of SiC to enhance the sample throughput. The Sensor is made up of PtꢀRh wire and
measurement can be carried out at inert, oxidizing and vacuum conditions with heating rate
ꢀ1
1
0°C. min . Temperature dependent density and speed of sound were measured with an
Anton Paar (DSA 5000 M) instrument which is based on oscillating Uꢀ tube principle. It can
ꢀ3
measure density very precisely in the range of (0ꢀ3000) kg.m and speed of sound from 1000
ꢀ1
to 2000 m.s simultaneously in temperature range of (273.15ꢀ 343.15) K. Dynamic Viscosity
of ILs were measured by Anton Paar micro viscometer (Lovis 2000ME) attached with the
master instrument (DSA 5000M) over studied temperature range (293.15 to 343.15) K at
atmospheric pressure. This instrument is based on rolling ball technique and can measure
viscosity in the range (0.3 to 10,000) mPa.s. The temperature is controlled by a builtꢀ in
precise Peltier thermostat with an accuracy of ±0.01 K. The standard uncertainties over
ꢀ3
ꢀ1
measurements were estimated to be less than 0.05 kg.m for density, 0.05 m.s for speed of
sound and 0.05 mPa.s for viscosity. For better precision the density meter was calibrated with
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dry air and Millipore water at regular interval whereas, lovis was calibrated with the
reference liquid (S3, N26, N100 liquid for 1.59 mm, 1.8 mm and 2.5 mm capillary
respectively) provided by Anton Paar. The samples were filled in density, speed of sound cell
as well as lovis capillary in single cycle and measurements were carried out by slow
equilibration mode instantaneously.
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Measurement of electrical conductivity was accomplished through Eutech (PC 700)
instrument that includes an electrode with a cell constant of K=1 and built in temperature
sensor. The conductance cell was calibrated with an aqueous solution of 0.01 N KCl and the
cell can measure conductivity from 0.0 ꢁS to 200 mS. Nitrogen atmosphere was sustained
throughout the measurement by using an inꢀhouse fabricated double layered glass jacket
setup. The inlet and outlet of the setup were connected to the water bath for temperature
maintenance. As we are dealing with high density and high viscosity samples, the instrument
used in this work were also calibrated with reference ionic liquid namely, 1ꢀhexylꢀ3ꢀ
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methylimidazolium bis(trifluoromethylsulfonyl)imide, [C Mim][Tf N].
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Measurement of Rheological Properties. Rheological studies were performed on an
Anton Paar’s MCR (Modular Compact Rheometer) 102, with a CP 40 Cone and Plate
measuring system. All ILs were kept under high vacuum before starting the experiments. A
small portion of IL was placed on the smooth plate of rheometer and coneꢀ plate geometry
was lowered to its truncation gap, and IL was allowed to equilibrate for 10 minutes for
allowing the experiment. The experimental temperature was controlled by PꢀPTD 200/AIR
Plate– Peltier temperature device. Measurements were performed in frequency sweep (1ꢀ100
ꢀ1
ꢀ1
rad.s ) with 50 % strain and strain sweep (100 ꢀ 1000 s ) modes at a constant frequency of 1
Hz.
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Preparation of 1ꢀAlkylꢀ 1,2,4ꢀtriazoles (1aꢀc).
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ꢀbutyl and 1ꢀhexylꢀ1,2,4ꢀtriazoles have been previously reported. Here, we have
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synthesized 1ꢀisopentylꢀ1,2,4ꢀtriazole by modified Shreeve’s Procedure as briefly described
below.
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Preparation of 1-Isopentyl-1,2,4-triazole (1c)
To the solution of 1,2,4ꢀtriazole (16.4 mmol) in dry methanol (15 ml), dry methanolic
solution of sodium methoxide (16.5 mmol) was added. The mixture was left to stir for 30 min
at room temperature, and then (16.56 mmol) of 1ꢀ bromoꢀ 3ꢀ methyl butane was added
dropwise and left to stir for 4 h followed by refluxed through overnight at 70°C. Reaction
was monitored through TLC. After completion, the methanol was removed by using
rotary evaporator and halide impurity was removed by washing with water and ethyl acetate
mixture. Moreover, using rotavapor removed the ethyl acetate and compound was dried
4
through MgSO . The crude product was purified through column chromatography in neutral
alumina. The resulting solution was then placed into high vacuum, affording a colorless
1
liquid. (89% yield) H NMR (500 MHz, CDCl ) δ 8.04 (s, 1 H), 7.92 (s, 1 H), 4.17 (t, J = 7.5
3
13
Hz, 2H), 1.77 (m, 2H), 1.56 (m, 1 H), 0.94 (d, 6H). C NMR (125 MHz, CDCl
3
) δ 151.9,
+
1
42.7,48.1, 38.6, 25.5, 22.3.HRMS (ESI+) m/z for [M] calcd140.1188, found 140.1184.
1
-butyl-1,2,4-triazole (1a).1ꢀbutylꢀ1,2,4ꢀtriazole (1a) was obtained as colorless liquid
1
following a method described above. H NMR (500 MHz, CDCl ) δ 8.03 (s, 1 H), 7.93 (s, 1
3
13
H), 4.16 (t, J = 7.25 Hz, 2H), 1.86 (m, 2H), 1.34 (m, 2 H), 0.94 (t, 7.5 Hz, 3H). C NMR (125
+
MHz, CDCl
3
) δ 151.9, 142.8,49.5, 31.8, 19.7, 13.5.HRMS (ESI+) m/z for [M]
calcd126.1031, found 126.1026.
1-Hexyl-1,2,4-triazole (1b).1ꢀHexylꢀ1,2,4ꢀtriazole (1b) was obtained as light yellow viscous
1
liquid. H NMR (500 MHz, CDCl ) δ 8.03 (s, 1 H), 7.92 (s, 1 H), 4.12 (t, J = 7.5 Hz, 2H),
3
13
1
.86 (m, 2H), 1.28 (m, 6 H), 0.85(t, 6.5 Hz, 2H). C NMR (125 MHz, CDCl ) δ 151.7, 142.7,
3
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+
49.7, 31.1, 29.7, 26.0, 22.4, 13.9. HRMS (ESI+) m/z for [M] calcd154.1344, found
154.1349.
Preparation of Ionic Liquids (2aꢀc). 1ꢀAlkylꢀ4ꢀmethylꢀ1,2,4ꢀ triazolium based ILs (2aꢀc)
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were synthesized by a modified Shreeve’s procedure. In a double necked round bottom flask
ꢀ4ꢀbutane sultone (14.4 mmol) was added dropwise to the 1ꢀ alkylꢀ 1,2,4ꢀ triazole (14.4
1
mmol) (1aꢀc) at 0˚C. The resulting solution was allowed to stir at room temperature until a
solid was obtained. In order to remove unreacted starting materials reaction mixture was
washed with toluene followed by diethyl ether. The crude product was dried under reduced
pressure to get the zwitterionic compound. This zwitterionic compound was further allowed
to react with trifluromethane sulfonic acid (14.5 mmol) at 0˚C. Resulting solution was stirred
at 60˚C until a thick liquid formed. Obtained thick liquid was washed with diethyl ether to
remove the excess trifluromethane sulfonic acid and placing under high vacuum as light
yellow color liquid obtained as ILs (85% yield) (2aꢀc).
1
1
-isopentyl-4-(4-sulfobutyl)-1H-1,2, 4-triazol- 4 -ium trifluoromethanesulfonate (2c). H
NMR (500 MHz, CDCl
3
) δ 9.76 (s, 1 H), δ 8.55 (s, 1 H), 4.55 (t, J = 5.0 Hz, 2H), 4.43 (t, 7.5
1
3
HZ, 2H), 3.16 (t, 6.25 Hz, 2H), 2.25 (m, 2H), 1.87 (m, 4 H), 1.64 (m, 1 H), 0.98 (d, 6 H). C
NMR (125 MHz, CDCl
3
) δ 142.6, 140.8, 124.0, 121.5, 118.9, 116.4, 74.0, 51.3, 48.4, 37.6,
+
25.6, 23.7, 23.0, 22.0, 19.6. HRMS (ESI+) m/z for [M] calcd 276.1382, found 276.1373.
1
1
-butyl-4-(4-sulfobutyl)-1H-1,2,4-triazol-4-ium trifluoromethanesulfonate (2a). H NMR (500
3
MHz, CDCl ) δ 9.74 (s, 1 H), δ 8.56 (s, 1 H), 4.54 (t, J = 5.0 Hz, 2H), 4.42(t, 7.25 Hz, 2H),
3.15 (t, 6.25 HZ, 2H), 2.24 (m, 2H), 1.96 (m, 2 H), 1.84 (m, 2 H), 1.38 (m, 2 H), 0.97 (t, 7.5
13
HZ, 3H). C NMR (125 MHz, CDCl
3
) δ 142.7, 140.9,124.0, 121.5, 119.0, 116.4, 74.1, 52.5,
+
4
8.4, 30.8, 23.7, 23.0, 19.4, 13.2. HRMS (ESI+) m/z for [M] calcd 262.1225, found
262.1223.
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1-hexyl-4-(4-sulfobutyl)-1H-1,2,4-triazol-4-ium trifluoromethanesulfonate (2b). H NMR (500
MHz, CDCl ) δ 9.69 (s, 1 H), δ 8.56 (s, 1 H), 4.55 (t, J = 5.0 Hz, 2H), 4.40 (t, 7.5 Hz, 2H),
.16 (t, 6.0 Hz, 2H), 2.25 (m, 2H), 1.96 (m, 2 H), 1.84 (m, 2 H), 1.31 (m, 6 H), 0.87 (t, 7.25
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Hz, 2H). C NMR (125 MHz, CDCl ) δ 142.6, 140.9,124.0, 121.5, 118.9, 116.4, 74.1, 52.7,
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+
48.4, 31.0, 28.8, 25.8, 23.7, 23.0, 22.3, 13.8.HRMS (ESI+) m/z for [M] calcd 290.1538,
found 290.1525.
ꢀ
Results and Discussion
Synthesis. A number of methods for the alkylation of 1,2,4ꢀtriazole are documented in the
literature, Among all of them Shreeve’s methods are wellꢀknown. Here, In this work we have
reported alkylation of 1,2,4ꢀ triazole at the Nꢀ1 position followed by modified Shreeve
18,24
procedure.
In brief, commercially available 1,2,4ꢀtriazole were alkylated with appropriate
1
ꢀbromoalkane in the methanolic solution of sodium methoxide. These substituted triazole
(1aꢀc) were quaternized with 1,4ꢀ butane sultone at Nꢀ4 position, which gave zwitter ionic
salts. Moreover these salts have been further reacted with trifluromethane sulfonic acid which
leads to proton transfer, providing the desired triazolium based ionic liquids (2aꢀc) as clear
1
13
and light yellow oils. Synthesized ILs have been characterized through H, C, DEPT NMR
and HRMS spectral techniques (see in supporting information Figure S1 to S6). The proton
1
shifting from CF SO H to RSO H has been studied through H NMR. As illustrates in figure
3
3
3
S10, the chemical shift of triazole ring proton (H and H ) in zwitterion intermediate is
a
b
appeared at 8.2 and 7.9 ppm respectively. When this intermediate is further reacted with
equimolar trifluromethane sulfonic acid the NMR peaks of triazole ring (H ’ and H ’) is
shifted towards downꢀfield as 9.7 and 8.5 ppm respectively. The proton transport mechanism
a
b
2
7
between zwitterion blends and Brønsted acid was studied by Ohno and coworkers through
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their physiochemical properties. The water content is less than 1000 ppm in all studied ILs
which have measured with KarlꢀFischer volumetric titrator.
Scheme1. Synthesis of 1ꢀ Alkylꢀ4ꢀ (4ꢀsulfobutyl) ꢀ 1Hꢀ1,2,4ꢀtriazolꢀ4ꢀ
iumtrifluoromethanesulfonate Ionic Liquids 2aꢀc
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Physiochemical Properties. To minimize the water content, ILs were dried under high
vacuum for 24 h. Thermal stability of synthesised triazolium based ILs were investigated by
Thermogravimetry analysis. As mentioned in Figure S7, TGA curves of ILs has twoꢀ step
degradation. Although the mechanism of degradation was not studied but it might be said that
28
composition of the ions controlled the degradation pathway as reported in the literature. On
varying the linear alkyl substituent the thermal stability decreases in order [BtTzm][CF
> [HxTzm][CF SO ] > [IpTzm][CF SO ] following the usual trend.
3 3
SO ]
3
3
3
3
The experimental densities were measured over temperature range (298.15 to 343.15)
K at atmospheric pressure. It is widely known that density is one of the major indices to
reflect the energy performance of energetic materials because the higher density usually
means the higher mole number of an energetic ILs that can be packed into a limited volume,
9
indicating higher energy contribution to the explosive composition. The ILs developed in
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ꢀ
3
this work exhibited higher density which lies in the range of (1.317ꢀ 1.373) g.cm at 298.15
7
K, which is higher than the density reported for some energetic ILs , thus showing good
agreement for energetic ILs. Moreover, the effect of temperature and variation in alkyl chain
28,29
length has also agreed with the trend reported earlier.
In general, an increase in density
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occurs when a better arrangement of the ions in the liquid takes place thus allowing a greater
30
number of ions to be located in a unit volume. As reported in Table S1 the density of the
studied ILs decreased with increasing in the chain length and increased with the branching
following the trend [HxTzm][CF
3 3 3 3 3 3
SO ] < [BtTzm][CF SO ] < [IpTzm][CF SO ]. With the
increase in linear chain length in ILs from [BtTzm][CF SO ] to [HxTzm][CF SO ] density
3
3
3
3
ꢀ3
decreases (1.371ꢀ1.317) g.cm up to 5 % because longer alkyl chain substituent entail more
stearic hindrance and consequently leading to poor packing arrangement which also results in
31,32
less interionic interactions.
the [IpTzm][CF SO
whereas, branching in alkyl chain decreases steric hindrance in
SO ],
3
3
] than in case of lesser alkyl chain length analogue [BtTzm][CF
3
3
ꢀ3
that might account for its very slightly increased density (1.373 g.cm ) at 298.15 K which
leads to comparatively more interionic interactions. As illustrated in Figure 1, density of ILs
decrease linearly with temperature. This decrease in density can be attributed to difficulty for
the formation of interionic interactions such as Hꢀbonding and packing which arises due to
asymmetry of ions. Moreover, experimental density data have been correlated through
3
3
estimated density obtained from Gardas and Coutinho model using equation (1)
ꢄ
ꢀꢁꢂꢃ
=
(1)
ꢅ ꢇ ꢉꢂꢊꢋꢌꢊꢁꢍꢎ
ꢆ
ꢈ
ꢀ3
ꢀ1
Where,
ρ
cal is the calculated density (kg.m ), M is the molar mass (kg.mol ), N is the
3
Avogadro’s number, V
m
is molecular volume (Å ), T is temperature (K) and P is the pressure
(
MPa). The coefficient a, b, and c were estimated by fitting equation (1) to about 800
34,35
−3
experimental density data points
covering the large density range (987ꢀ1547 kg.m ),
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temperature range (293.15ꢀ393.15) K and pressure range (0.1ꢀ30) MPa and found as 0.8005,
ꢀ4
ꢀ1
ꢀ6
ꢀ1
36
6
.6520×10 (K ) and ꢀ5.919×10 (MPa ) respectively at 95% confidence level. The
–
21,24,37
molecular volume of anion (V
a
*), for [CF
3
SO
3
] has been taken from literature
as 129
3
Å whereas cation molecular volumes (Vc*) are estimated in this work and presented in
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Tableꢀ1 along with maximum absolute deviation (MAD) and absolute relative deviation
33
(
ARD) obtained using Gardas and Coutinho model . As presented in figure 3, the calculated
33
density, ρcal for triazolium based ILs using Gardas and Coutinho model shows very good
agreement with the experimental density, ρexp and were related as ρcal = (1.0003±0.0001) ρ
exp
2
with a confidence level of 95% and R =0.9999.
Information obtained from the temperature dependency and the effect of cation and/or
anion of ILs on speed of sound can be useful to understand the extent of intermolecular
38,39
interactions involved.
For studied 1,2,4ꢀ triazole based ILs, the effect of temperature and
alkyl chain length on speed of sound are tabulated in Table S1. The speed of sound decreases
linearly with the addition of methyl group at Nꢀ1 position as illustrated in Figure 2. This
ꢀ1
decrease in speed of sound from [BtTzm][CF
3
SO
3
] (1387.43 m.s ) to [IpTzm][CF
3
3
SO ]
ꢀ1
ꢀ1
(
1344.92 m.s ) to [HxTzm][CF SO ] (1320.79 m.s ) at 298.15 K could be attributed to the
3 3
increased spatial distance between the molecules. With the addition of one more methyl
group the steric hindrance increases leading to more intermolecular free space thereby,
decreasing the speed of sound.
For the better understanding of the extent of molecular interactions, industrially
relevant thermodynamic parameters have been derived, such as thermal expansion coefficient
(
ꢏꢐ) and isentropic compressibility ( ꢒ
ꢑ
), from experimental density and speed of sound data
using equations (2) and (3).
ꢔꢕ
ꢏ = ꢓ ꢖ
(2)
ꢐ
ꢔꢌ
ꢍ
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ꢗ
ꢕꢘꢙ
ꢑꢒ =
(3)
As shown in table S1, among the studied ILs, [HxTzm][CF
3
SO
3
] shows the higher value of
compressibility which suggests that with increase in asymmetry of ILs, the packing density
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0
4
0
and the extent of degree of hydrogen bonding is decreasing. The effect of temperature on
expansivity (
p s
α ) and compressibility (κ ) of studied ILs were shown in figures S8 and S9,
respectively.
Viscosity is an imperative intensive property which helps to describe the potential
applications of any ILs and is significantly influenced by intermolecular interactions such as
41
Hꢀbonding, dispersive forces and columbic interactions. The viscosity for the developed ILs
has been measured in the temperature range (293.15ꢀ343.15) K. At a particular temperature
the viscosity of the linear ILs increases monotonically with an increase in the cation chain
length for example viscosity increased from 99.14 to 123.83 mPa.s at 298.15 K, when chain
length increased from butyl to hexyl i.e., [BtTzm][CF
3 3 3 3
SO ] to [HxTzm][CF SO ], which
could be mainly due to the augmentation in molecular size, packing and orientation into a
42
43
bulk fluid. M. Watanbe and coworkers also suggested that with increasing number of
carbon atoms in the alkyl chain, the inductive forces in the ILs increase, which causes
enhancement of the viscosity owing to frictional forces among ions, aggregates, and
43
clusters. Furthermore, when linear chain is replaced by branched chain, the viscosity is
observed to be higher than their linear longer chain analogue. The increase in viscosity of
branched isopentyl substituted IL, [IpTzm][CF SO ] is similar to an increase with number of
3
3
3
2
branched isopropyl group in 1,2,3ꢀ triazolium based ILs and is elucidated mechanistically
as branched chain has more stabilized packing causing an increase in the shear resistance to
44
3 3
intermolecular motion, which subsequently results in higher viscosity of [IpTzm][CF SO ].
whereas, the viscosities of synthesized ILs decreases asymptotically over studied temperature
range (293.15ꢀ343.15) K as shown in Figure 4(A). This effect is recognized due to the
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increase in Brownian motion of the constituent ions of ILs. The viscosity values of studied
ILs with respect to temperature is shown in table S1. The experimental temperatureꢀ
dependent viscosity data were correlated with empirical equation proposed by Vogelꢀ
Tammannꢀ Fulcher (VTF) (equation 4) and VTF parameters are presented in Table 2.
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ꢝ
η = η expꢛꢜ
ꢡ
(4)
ꢚ
ꢉꢞꢟꢞꢠꢎ
Where ηꢚ(mPa.s) is the viscosity at the temperature limit, B (K) is the quantity related to the
activation barrier and T is the absolute or “ideal glass transition” temperature.
0
The measured molar conductivity of synthesized 1,2,4ꢀtriazolium based ILs in the
temperature range 293.15K to 343.15K is presented in Figure 4(B) and the values are given
in table S1. In general, the 1,2,4ꢀtriazolium based ILs are shown to have lower conductivity
than imidazolium based ILs having similar anions, because of larger cation size and stronger
1
8
intermolecular interactions. The measured experimental molar conductivity of studied ILs
followed the trend [HxTzm][CF SO ] ˂ [IpTzm][CF SO ] ] ˂ [BtTzm][CF SO ] ] at 298.15
K, which further emphasized the fact that the smaller ions have higher mobility than bigger
3
3
3
3
3
3
46
ions. In general, with increase in substituent chain length the viscosity of IL increases and
47
molar conductivity decreases. The effects that lead to an increase in viscosity and decrease
in conductivity of the ionic liquids were studied by testing two hypotheses: (1) ion
48
association, and (2) differences in the potential energy surface profile. The experimentally
obtained data for studied ILs suggests that when branching in the substituent is increased, the
viscosity of the corresponding IL (isopentyl substituted) is increased to a greater extent that
its value exceeds that of linear long chain analogue (hexyl substituted) and shows the trend as
([BtTzm][CF
3 3 3 3 3 3
SO ] (99.14 mPa.s) ˂ [HxTzm][CF SO ] (123.83 mPa.s) ˂ [IpTzm][CF SO ]
(
136.47 mPa.s), whereas in case of molar conductivity the ILs followed the regular trend of
decrease in conductivity with increase in substituent alkyl chain length i.e.,
ꢀ
1
ꢀ1
[HxTzm][CF
3
SO
3
] (0.564 mS.cm ) ˂ [IpTzm][CF
3
SO
3
] (0.881mS.cm ) ˂ [BtTzm][CF
3
SO
3
]
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6
ꢀ
1
(1.459mS.cm ). The difference in the trend of molar conductivity and viscosity is due to
different factors responsible, for example molar conductivity is mainly governed by the
molecular size of the cation whereas viscosity is influenced by their size as well as their
packing and intermolecular interactions. Although, there is branching in the IL having
intermediate chain length (isopentyl substituted), due to continuous increase in the substituted
chain length (butyl to hexyl) of cation the molar conductivity followed regular decreasing
trend. In case of viscosity, branching in the chain greatly influences the packing arrangements
and increases intermolecular interactions which in turn lead to higher viscosity of isopentyl
substituted IL. With increase in temperature the molar conductivity of studied ILs is observed
to increase due to increase in the rate of mobility of ions. The experimental molar
conductivity data were correlated with VTF equation (equation 5) and results are presented in
0
1
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0
Table 3.
ꢟꢝ
ꢢ = Λ expꢛꢜ
ꢡ
(5)
ꢣ
ꢚ
ꢉꢞꢟꢞꢠꢎ
2
ꢀ1
Where Λ
0
(mS.cm .mol ) is the molar conductivity at the temperature limit and B (K) and T
0
49
(
K) are the variable parameters. Temperature dependent molar conductivity (Λ
m
) data are
presented in Figure 4(B) where symbols represents the experimental data points while solid
lines signifies the VTF fitted curves.
For assessing the ionicity, Walden plot as an approximate and readily accessible
approach. Ionicity does not necessarily describe the chemical availability of individual ions,
5
0
which may depend more strongly on the associated nature of the IL. The Fractional
Walden’s rule (equation 6) describes the relationship between fluidity and molar
conductivity, where ˄
is the molar conductivity, η
is the viscosity, C is the constant that
is an
m
accounts for cation and anion radius and shifts plots vertically in the Walden plot, and
α
exponent allowing for deviations from slopes of unity in the Walden plot, which has been
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verified to explore the completeness of dissociation and the ionicity of synthesized ILs. In
Walden plot, the reference or “ideal line” is commonly symbolized by a 0.01 M dilute KCl
solution, which is an indicator of the ideal interionic interaction between cation and anion of
52
the ILs. ILs lie within 20% of KCl reference line of Walden plot are considered as highly
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dissociated and termed as “good ILs” whereas those are far from this line can be classified as
5
3
“
Poor ILs”.
ꢟꢗ
logΛ = log C + ꢛαꢛlogη
(6)
ꢤ
As shown in figure 5, for the logarithmic plot of Walden rule, the synthesized triazolium
based ILs behave as that of less ionic in nature and fall below the ideal line due to strong ion
3 3 3 3
pairing and the ionicity follows the order [BtTzm][CF SO ] > [IpTzm][CF SO ] >
[HxTzm][CF SO ]. Moreover, plot showed very good linear relation with regression
3
3
2
54
coefficient R ≈0.999 and studied ILs can be referred as “good” ILs. The slope (α) and
intercept (log C) values for linear equation 6 are shown in Table S3.
Rheological Study. The effect of chain length and branching of synthesized triazolium based
ILs have been investigated by the steady rheological measurements at room temperature. In
Newtonian flow, shear stress (resistance to flow) is proportional to shear rate (rate of motion
of fluid with respect to nearby fluid elements). Therefore, viscosity should be constant
55
regardless of shear rate unless a sample is nonꢀNewtonian fluid. Figure 6(A) shows the
variation of steady shear viscosity as a function of shear rate for studied ILs and exhibits a
56
constant viscosity, which is indication to the Newtonian flow of behavior. The viscosity (η)
values over the studied range of shear rate has been estimated and it follow the same trend as
[
3 3 3 3 3 3
IpTzm][CF SO ] ˃ [HxTzm][CF SO ] ˃ [BtTzm][CF SO ]. Additionally, steady shear
rheology (see figure 6(B)) also depicts that the relation between shear stress and shear rate is
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ꢀ
1
linear over studied range (0ꢀ1000) s , which is also appropriate for the Newtonian fluid
56,57
behavior of ILs.
The flow behavior of the ILs was then studied by frequencyꢀsweep dynamic rheology.
The G’ (Storage modulus) normally tell us about solid like nature while G” (Loss modulus)
tell us about liquid like nature. Usually for gels (G’ > G’’) which states that storage modulus
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is greater than loss modulus. Figure 7, represents the frequency response of ILs where, the
step in the storage modulus at ~ 80 rads/sec is not real as it is an instrument artifact. At high
frequency range, due to inertia the equipment creeps in for low viscous samples (studied ILs).
Although with increase in the angular frequency both G’ and G” were changed while the G”
(loss modulus) dominates the G’ (storage modulus) over the frequency range. This response
indicated more of liquid like behavior of ILs.
ꢀ
Conclusions
A series of 1ꢀ alkylꢀ1,2,4ꢀ triazolium [CF SO ] ionic liquids were synthesized by the Nꢀ
3
3
alkylation followed by quaternization at Nꢀ4 position of triazole. Temperature dependence of
physiochemical properties such as density, speed of sound, viscosity and conductivity were
determined and Walden plot was constructed in order to determine the ionicity of ILs. ILs
having branched substituent at Nꢀ1 position are found to be more denser and viscous than
linear alkyl substituent analogues. The density and speed of sound are found to decrease
linearly with temperature. Densities of studied ILs were also predicted through Gardas and
Coutinho model, and are found to be in good accordance with the experimental values.
Furthermore, molecular volume of the triazolium cation has been predicted for the first time
with a deviation less than 0.04%. With increase in temperature, viscosity of studied ILs
decreases whereas conductivity increases asymptotically, and the measured data have been
correlated well using the VTF equation. Walden plot shows that the values of studied ILs fall
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close to the magnitude of ideal KCl line and thus can be considered as good (high ionicity)
ILs”. Among the studied ILs, the ionicity is found to be highest for the IL having smaller
3 3
cation size, [BtTzm][CF SO ] and this indicates that constituted ions could move more
independently of one another. Additionally, Newtonian flow behavior of ILs inspected by
shear rate experiment shows that the viscosity of studied ILs is not affected over the studied
range of shear rate. The higher value of storage modulus (G’) than the loss modulus (G”)
found through frequency sweep method indicates the typical liquidꢀlike behavior of all the
studied ILs.
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ꢀ
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website.
1
13
H, C and DEPT NMR spectra of synthesized ILs, TGA curve, plot of temperature
dependent expansivity (
CF SO H to RSO H of [IpTzm][CF
and compressibility ( ), experimental data of density, viscosity, speed of sound, molar
α
p
) and compressibility(
s
κ ) of ILs, plot of proton transfer from
3
3
3
3
SO ]. Table of temperature dependent expansivity (
3
p
α )
κ
s
conductivity, expansivity and compressibility over studied range of temperature (293.15ꢀ
343.15) K, coefficient of linear fitted density and absolute relative deviation and liner fitted
parameters of Walden plot are provided in supporting information.
ꢀ
Acknowledgements
The authors would like to acknowledge Council of Scientific and Industrial Research
(CSIR), and IIT Madras for their financial support through grant numbers 09/084
(0650)/2013ꢀEMRꢀ1, and CHY/15ꢀ16/833/RFIR/RAME, respectively.
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References
(
1)
Hallett, J. P.; Welton, T. Roomꢀ Temperature Ionic Liquids: Solvents for Synthesis and
Catalysis.2 Chem. Rev. 2011, 111, 3508–3576.
(
2) Hoogerstraete, T. V.; Onghena, B.; Binnemans, K. Homogeneous Liquidꢀ Liquid
Extraction of Metal Ions with a Functionalized Ionic Liquid. J. Phys. Chem. Lett.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
013, 4, 1659–1663.
(
3) Singh, A.; Kumar, A. Probing the Mechanism of Baylisꢀ Hillman Reaction in Ionic
Liquids. J. Org. Chem. 2012, 77, 8775–8779.
(
4)
5)
Sebastiao, E.; Cook, C.; Hu, A.; Murugesu, M. Recent Developments in The Field of
Energetic Ionic Liquids. J. Mater. Chem. A 2014, , 8153–8173.
2
(
Jiang, W.; Yan, T.; Wang, Y.; Voth, G. A. Molecular Dynamics Simulation of the
Energetic Roomꢀ Temperature Ionic Liquid, 1ꢀHydroxyethylꢀ4ꢀaminoꢀ1,2,4ꢀtriazolium
Nitrate (HEATN). J. Phys. Chem. B 2008, 112, 3121–3131.
(6) Singh, R. P.; Verma, R. D.; Meshri, D. T.; Shreeve, J. M. Energetic NitrogenꢀRich
Salts and Ionic Liquids. Angew. Chem. Int. Ed. 2006, 45, 3584–3601.
(
7)
8)
Zhang, Q.; Shreeve, J. M. Energetic Ionic Liquids as Explosive and Propellant Fuels:
A New Journey of Ionic Liquid Chemistry. Chem. Rev. 2014, 114, 10527–10574.
Tao, G. H.; Guo, Y.; Joo, Y. H.; Twamley, B.; Shreeve, J. M. Energetic Nitrogenꢀ Rich
Salts and Ionic Liquids: 5ꢀaminotetrazole (AT) As a Weak Acid. J. Mater. Chem.
(
2
008, 18, 5524–5530.
(9)
Dong, L. L.; He, L.; Liu, H. Y.; Tao, G. H.; Nie, F. D.; Huang, M.; Hu, C. W.
Nitrogenꢀ Rich Energetic Ionic Liquids Based on the N,NꢀBis(1Hꢀtetrazolꢀ5ꢀyl) amine
Anionꢀ Synthesis, Structures and Properties. Eur. J. Inorg. Chem. 2013, 28, 5009–
5
019.
18
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Page 19 of 34
The Journal of Physical Chemistry
1
2
3
4
5
6
7
8
9
(10) Jimenez, P.; Roux, M. V.; Turrion, C. Thermophysical Properties of Nꢀ heterocyclic
Compounds II. Enthalpies of Combustion, Vapour Pressures, Enthalpies of
Sublimation, and Enthalpies of Formation of 1,2,4ꢀTriazole and Benzotriazole. J.
Chem. Thermodyn. 1989, 21, 759–764.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(11) Srinivas, D.; Ghule, V. D.; Muralidharan, K. Synthesis of Nitrogenꢀ Rich Imidazole,
1
,2,4ꢀTriazole and Tetrazole Based Compounds. RSC Adv. 2014, 4, 7041–7051.
(
12) Mirzaei, Y. R.; Twamley, B.; Shreeve, J. M. Synthesis of 1ꢀAlkylꢀ1,2,4ꢀtriazoles and
the formation of Quaternary 1ꢀAlkylꢀ4ꢀpolyfluoroalkylꢀ 1,2,4ꢀtriazolium Salts Leading
to Ionic Liquids. J. Org. Chem. 2002, 67, 9340–9345.
(13) Schmidt, M. W.; Gordon, M. S.; Boatz, J. A. Triazoliumꢀ Based Energetic Ionic
Liquids. J. Phys. Chem. A 2005, 109, 7285–7295.
(
14) Ren, J., Wu, L.; Li, B. G. Potential for Using Simple 1,2,4ꢀTriazole Salt Solutions as
Highly Efficient CO Absorbents with Low Reaction Enthalpies. Ind. Eng. Chem. Res.
2013, 52, 8565–8570.
2
(
15) Meyer, D.; Strassner, T. 1,2,4ꢀ Triazoleꢀ Based Tunable Aryl/ Alkyl Ionic Liquids. J.
Org. Chem. 2011, 76, 305–308.
(
16) Nagarajan, S.; Elango, K. Reusable 1,2,4ꢀ Triazolium Based Bronsted Acidic Room
Temperature Ionic Liquids as Catalyst for Mannich Base Reaction. Catal. Lett. 2014,
144, 1507–1514.
(
17) Liang, X.; Yang, J. Synthesis of a Novel Multi –SO H Functioalized Ionic Liquid and
3
Its Catalytic Activities for Biodiesel Synthesis. Green Chem., 2010, 12, 201–204.
18) Hoz, A. T. D. L.; Brauer, U. G.; Miller, K. M. Physiochemical and Thermal Properties
for a Series of 1ꢀAlkylꢀ4ꢀmethylꢀ1,2,4ꢀtriazolium Bis(trifluoromethylsulfonyl) imide
Ionic Liquids. J. Phys. Chem. B 2014, 118, 9944ꢀ9951.
(
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5
5
5
5
5
5
5
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(19) Daily, L. A.; Miller, K. M. Correlating Structure with Thermal Properties for a Series
of 1ꢀAlkylꢀ4ꢀmethylꢀ1,2,4ꢀtriazolium Ionic Liquids. J. Org. Chem. 2013, 78, 4196–
4
201.
(
20) Greaves, T. L.; Drummond, C. J. Protic Ionic Liquids: Evolving StructureꢀProperty
Relationships and Expanding Applications. Chem. Rev. 2015, 115, 11379–11448.
21) Gardas, R. L.; Coutinho, J. A. P. Group Contribution Method for the Prediction of
Thermophysical and Transport Properties of Ionic Liquids. AIChE J. 2009, 55, 1274–
0
1
2
3
4
5
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3
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0
1
2
3
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5
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9
0
(
1
290.
(22) Narita, A.; Shibayama, W.; Ohno, H. Structural Factors to Improve Physicoꢀ Chemical
Properties of Zwitterions as Ion Conductive Matrices. J. Mat. Chem. 2006, 16, 1475–
1
482.
(
23) Tokuda, H.; Hayamizu, K.; Ishii, K.; Susan, M. A. B. H.; Watanabe, M.
Physiochemical Properties and Structures of Room Temperature Ionic Liquids. 1.
Variation of Anionic Species. J. Phys. Chem. B 2004, 108, 16593–16600.
(
24) Gardas, R. L.; Coutinho, J. A. P. A Group Contribution Method for Viscosity
Estimation of Ionic Liquids. Fluid Phase Equilib. 2008, 266, 195–201.
(
25) Marsh, K. N.; Brennecke, J. F.; Chirico, R. D.; Frenkel, M.; Heintz, A.; Magee, J. W.;
Peters, C. J.; Rebelo, L. P. N.; Seddon, K. N. Thermodynamic and Thermophysical
Properties of the Reference Ionic Liquid: 1ꢀHexylꢀ3ꢀmethylimidazolium
bis[(trifluoromethyl)sulfonyl] amide (including mixtures). Part1. Experimental
Methods and Results. Pure. Appl. Chem. 2009, 81, 781–790.
(26) Mirzaei, Y. R.; Xue, H.; Shreeve, J. M. Low Melting N ꢀ4ꢀFunctionalizedꢀ1ꢀAlkyl or
Polyfluoroalkylꢀ1,2,4ꢀ Triazolium Salts. Inorg Chem. 2004, 43, 361–367.
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4
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6
7
8
9
(27) Yoshizawaꢀ Fuzita, M.; Byrne, N.; Forsyth, M.; MacFarlane, D. R.; Ohno, H. Proton
Transport Properties in Zwitterion Blends with Bronsted Acids. J. Phys. Chem. B
2
010, 114, 16373–16380.
(28) Green, M. D.; Schreiner, C.; Long, T. E. Thermal , Rheological , and IonꢀTransport
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59
60
Properties of PhosphoniumꢀBased Ionic Liquids. J. Phys. Chem. A 2011, 115, 13829–
1
3835.
(
29) Sharma, G.; Gardas, R. L.; Coronas, A.; Venkatarathnam, G. Effect of Anion Chain
Length on Physiochemical Properties of N,Nꢀdimethylethanolammonium Based Protic
Ionic Liquids. Fluid Phase Equilib. 2016, 415, 1–7.
(30) Vera, R. R. M.; Plenet, S. J.; Gaillon, L.; Rizzi, C.; Rodriguez, M. A.; Cote, G.;
Chagnes, A. Physiochemical Properties of Novel Cholinium Ionic Liquids for the
Recovery of Silver from Nitrate Media. RSC Adv. 2015, 5, 78268–78277.
(
31) Tokuda, H.; Hayamizu, K.; Ishii, K.; Susan, M. A. B. H.; Watanabe, M.
Physiochemical Properties and Structures of Room Temperature Ionic Liquids. 2.
Variation of Alkyl Chain Length in Imidazolium Cation. J. Phys. Chem. B 2005, 109
,
6
103–6110.
(
32) Lartey, M.; Ilse, J. M.; Watkins, J. D.; Roth, E. A.; Bowser, S.; Kusuma, V. A.;
Damodaran, K.; Zhou, X.; Haranczyk, M.; Albenze, E.; Luebke, D. R.; Hopkinson, D.;
Kortright, J. B.; Nulwala, H. B. Branched Isomeric 1,2,3ꢀ triazoliumꢀ based Ionic
Liquids: New Insight Into Structureꢀ property Relationships. Phys. Chem. Chem. Phys.
2
015, 17, 29834–29843.
(
33) Gardas, R. L.; Coutinho, J. A. P. Extension of Ye and Shreeve group contribution
Method for Density Estimation of Ionic Liquids in a Wide Range of Temperatures and
Pressures. Fluid Phase Equilib. 2008, 263, 26–32.
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(34) Gardas, R. L.; Freire, M. G.; Carvalho, P. J.; Marrucho, I. M.; Fonseca, I. M. A.;
Ferreira, A. G. M.; Coutinho, J. A. P. PρT Measurements of ImidazoliumꢀBased Ionic
Liquids. J. Chem. Eng. Data 2007, 52, 1881–1888.
(
35) Gardas, R. L.; Freire, M. G.; Carvalho, P. J.; Marrucho, I. M.; Fonseca, I. M. A.;
Ferreira, A. G. M.; Coutinho, J. A. P. Highꢀ Pressure Densities and Derived
Thermodynamic Properties of ImidazoliumꢀBased Ionic Liquids. J. Chem. Eng. Data
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(
(
(
36) Ye, C.; Shreeve, J. M. Rapid and Accurate Estimation of Densities of Roomꢀ
Temperature Ionic Liquids and Salts. J. Phys. Chem. A 2007, 111, 1456–1461.
37) Gardas, R. L.; Coutinho, J. A. P. Estimation of Speed of Sound of Ionic Liquids Using
Surface Tensions and Densities. Fluid Phase Equilib. 2008, 265, 57–62.
38) Chhotaray, P. K.; Gardas, R. L. Thermophysical Properties of Ammonium and
Hydroxylammonium Protic Ionic Liquids. J. Chem. Thermodyn. 2014, 72, 117–124.
(39) Kavitha, T.; Attri, P.; Venkatesu, P.; Devi, R. S. R.; Hofman, T. Influence of Alkyl
Chain Length and Temperature on Thermophysical Properties of Ammoniumꢀ Based
Ionic Liquids with Molecular Solvent. J. Phys. Chem. B 2012, 116, 4561–4574.
(
40) Capelo, S. B.; Morales, T. M.; Carrete, J.; Lago, E. L.; Vila, J.; Cabeza, O.; Rodriguez,
J. R.; Turmine, M.; Varela, L. M. Effect of Temperature and Cationic Chain Length on
the Physical Properties of Ammonium Nitrateꢀ Based Protic Ionic Liquids. J. Phys.
Chem. B 2012, 116, 11302–11312.
(
41) Atilhan, M.; Jacquemin, J.; Rooney, D.; Khraisheh, M.; Aparicio, S. Viscous Behavior
of Imidazoliumꢀ Based Ionic Liquids. Ind. Eng. Chem. Res. 2013, 52, 16774–16785.
(42) Chhotaray, P. K.; Gardas, R. L. Structural Dependence of Protic Ionic Liquids on
Surface, Optical and Transport Properties. J. Chem. Eng. Data. 2015, 60, 1868–1877.
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(43) Tokuda, H.; Hayamizu, K.; Ishii, K.; Susan, M. A. B. H.; Watanabe, M.
Physiochemical Properties and Structures of Room Temperature Ionic Liquids. 2.
Variation of Alkyl Chain Length in Imidazolium Cation. J. Phys. Chem. B 2005, 109
,
6
103–6110.
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53
54
55
56
57
58
59
60
(44) Zhang, Y.; Xue, L.; Khabaz, F.; Doerfler, R.; Quitevis, E. L.; Khare, R.; Maginn, E. J.
Molecular Topology and Local Dynamics Govern the Viscosity of Imidazoliumꢀ based
Ionic Liquids. J. Phys. Chem. B 2015, 119, 14934–14944.
(45) Barnes, H. A. A Handbook of Elementar Rheology, Institute of Nonꢀ Newtonian Fluid
Mechanics, University of Wales, 2000.
(46) Fukumoto, K.; Yoshizawa, M.; Ohno, H. Room Temperature Ionic Liquids from 20
Natural Amino Acids. J. Am. Chem. Soc. 2005, 127, 2398–2399.
(
47) Sun, L.; Collazo, O. M.; Xia, H.; Brennecke, J. F. Effect of Structure on Transport
Properties (Viscosity, Ionic Conductivity, and SelfꢀDiffusion Coefficient) of Aprotic
Heterocyclic Anion (AHA) Roomꢀ Temperature Ionic Liquids. 1. Variation of Anionic
Species. J. Phys. Chem. B 2015, 119, 15030–15039.
(
48) Izgorodina, E. I.; Maganti, R.; Armel, V.; Dean, P. M.; Pringle, J. M.; Seddon, K. R.;
MacFarlane, D. R. Understanding the Effect of the C2 Proton in Promoting Low
Viscosities and High Conductivities in ImidazoliumꢀBased Ionic Liquids: Part I.
Weakly Coordinating Anions. J. Phys. Chem. B 2011, 115, 14688–14697.
(
49) Tao, R.; Simon, S. L. Rheology of ImidazoliumꢀBased Ionic Liquids with Aromatic
Functionality. J. Phys. Chem. B 2015, 119, 11953–11959.
(
50) MacFarlane, D. R.; Forsyth, M.; Izgorodina, E. I.; Abbott, A. P.; Annat, G.; Fraser, K.
On the Concept of Ionicity in Ionic Liquids. Phys. Chem. Chem. Phys. 2009, 11, 4962–
4
967.
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(51) Pinkert, A.; Ang, K. L.; Marsh, K. N.; Pang, S. Density, Viscosity and Electrical
Conductivity of Protic Alkanolammonium Ionic Liquids. Phys. Chem. Chem. Phys.
2
011, 13, 5136–5143.
(52) Luo, J.; Hu, J.; Saak, W.; Beckhaus, R.; Wittstock, G.; Venkelocom, I. F. J.; Agert, C.;
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Conrad, O. Protic Ionic Liquid and Ionic Melts Prepared from Methanesulfonic Acid
and 1Hꢀ1,2,4ꢀ Triazole as Highly Temperature PEMFC Electrolytes. J. Mater. Chem
.
2
011, 21, 10426–10436.
(
53) Schreiner, C.; Zugmann, S.; Hartl, R.; Gores, H. J. Fractional Walden Rule for Ionic
Liquidsꢂ: Examples from Recent Measurements and a Critique of the SoꢀCalled Ideal
KCl Line for the Walden Plot. J. Chem. Eng. Data. 2010, 55, 1784–1788.
54) Fraser, K. J.; Izgorodina, E. I.; Forsyth, M.; Scott, J. L.; MacFarlane, D. R. Liquids
intermediate between "Molecular" and "Ionic Liquids": Liquids Ion Pairs. Chem.
Commun. 2007, 37, 3817–3819.
(
(55) Burrell, G. L.; Dunlop, N. F.; Separvoic, F. Nonꢀ Newtonian Viscous Shear Thinning
in Ionic Liquids. Soft Matter. 2010, , 2080–2086.
6
(
56) Smith, J. A.; Webber, G. B.; Warr, G. G.; Atkin, R. Rheology of Protic Ionic Liquids
and Their Mixtures. J. Phys. Chem. B 2013, 117, 13930–13935.
(
57) Kulkarni, P. S.; Branco, L. C.; Crespo, J. G.; Nunes, M. C.; Raymundo, A.; Afonso, C.
A. M. Comparison of Physiochemical Properties of New Ionic Liquids Based on
Imidazolium, Quaternary Ammonium, and Guadinium Cations. Chem. Eur. J. 2007,
13, 8478–8488.
(
58) Babu, T. M.; Prasad, E. Chargeꢀ Transferꢀ Assisted Supramolecular 1 D Nanofibers
Through a Cholesteric Structureꢀ Directing Agent: Selfꢀ Assembly Design For
Supramolecular Optoelectronic Materials. Chem. Eur. J. 2015, 21, 11972–11975.
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ꢀ
Figure Captions
Figure 1.
Temperature dependent Density curve for an ionic liquid over studied range
298.15ꢀ 343.15)K. The symbol represents experimental values and the solid
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(
line symbolizes the values calculated from equation 1.
Figure 2.
Figure 3.
Figure 4.
Temperature dependent Speed of Sound curve for an ionic liquid over studied
range (298.15ꢀ 343.15)K.
Correlation between experimental density and estimated density of ionic
liquids at temperature range from 298.15 to 343.15 K.
Temperature dependent viscosity (A) and molar conductivity (B) curves for
an ionic liquid over studied temperature range (298.15ꢀ 343.15) K. where the
symbols represents experimental values and solid lines represents the values
calculated from equation 4 and 5 respectively.
Figure 5.
Figure 6.
Molar conductivity against the fluidity (Walden Plot) for the studied ILs.
(A) Curve for Steady Shear Viscosity as a function of Shear rate and
(B) Plot of Shear stress versus shear rate of studied ILs.
Figure 7.
Frequency sweep dynamic rheology of ILs: Open symbol represents the
Storage modulus (G’) and closed symbols symbolized the loss modulus
(G”).
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*
*
Table 1. Effective molecular Volume of anion (V
a
) and cation (V
c
) and estimated molecular
volumes (V ) of the studied ILs at 298.15K along with absolute relative deviation (ARD) and
m
maximum absolute deviation (MAD) obtained from Gardas and Coutinho model.
*
*
(expt)⊥
m
IL
M
V
c
V
a
V
m
(estd)
ARD
MAD
V
0
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9
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0
ꢀ1
3 #
3 $
3
3
(
g.mol )
(Å )
(Å )
(Å )
(
Å )
[
BtTzm][CF
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SO
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]
411.42
425.44
439.47
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129.0
498.5
515.0
554.5
498.0
514.0
554.0
0.04
0.02
0.04
0.06
0.06
0.09
[
IpTzm][CF
3
3
]
[
HxTzm][CF
3
3
]
# estimated in this work;
$
from reference [21], [27] and [30].
calculated from experimental density at 298.15 K
⊥
Table 2. VTF equation (4) parameters for viscosity data
ILs
η0 (mPa.s)
0.074
B (K)
0
T (K)
[BtTzm][CF SO ]
1059
987
151
162
158
3
3
[IpTzm][CF
3
SO
3
]
0.094
[HxTzm][CF SO ]
0.098
995
3
3
Table 3. VTF equation (5) parameters for molar conductivity data
2
ꢀ1
ILs
˄o (S.cm .mol )
B (K)
T
0
(K)
[
[
[
BtTzm][CF
3
SO
SO
SO
3
]
370.6
666.5
945.1
859
1006
970
171
169
185
IpTzm][CF
HxTzm][CF
3
3
]
3
3
]
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Figure 1
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