Thermodynamic properties of salophen schiff base + ionic liquid ([C nmIm][Br]) + dimethylformamide ternary mixtures at 298.15 K

Article abstract of DOI:10.1021/je200872n

The densities and viscosities of ternary mixtures of N,N′- salicylidenephenylenediamine Schiff base (Salophen) + ionic liquid + N,N-dimethylformamide (DMF) have been determined at 298.15 K and at atmospheric pressure. The ionic liquids were: 1-propyl-3-me

Full text of DOI:10.1021/je200872n

Article
pubs.acs.org/jced
Thermodynamic Properties of Salophen Schiff Base + Ionic Liquid
(
[C mIm][Br]) + Dimethylformamide Ternary Mixtures at 298.15 K
n
,
†
‡
§
Hemayat Shekaari,* Abolfazl Bezaatpour, and Rasoul Elhami-Kalvanagh
†
Department of Physical Chemistry, University of Tabriz, Tabriz, Iran
‡
Department of Chemistry, Faculty of Science, University of Mohaghegh Ardabili, Ardabil, Iran
§Department of Chemistry, Mamaghan Branch, Islamic Azad University, Mamaghan, Iran
ABSTRACT: The densities and viscosities of ternary mixtures of N,N′-salicylidene-
phenylenediamine Schiff base (Salophen) + ionic liquid + N,N-dimethylformamide
(
DMF) have been determined at 298.15 K and at atmospheric pressure. The ionic
liquids were: 1-propyl-3-methylimidazolium bromide ([C mIm][Br]), 1-butyl-3-
3
methylimidazolium bromide ([C mIm][Br]), 1-pentyl-3-methylimidazolium bromide
4
(
[C mIm][Br]), and 1-hexyl-3-methylimidazolium bromide ([C mIm][Br]). These
5
6
0
data have been used to calculate the standard partial molar volumes, V , transfer partial
molar volumes, Δ V , and viscosity B-coefficients for the investigated mixtures. An
ϕ
0
ϕ
tr
increase in concentration and alkyl chain length of ionic liquid results in a decreasing
trend in the calculated volumetric and viscometric parameters. All of these parameters
were used to interpret the effect of ionic liquids on the nonaqueous solutions of
Salophen Schiff base and solute−solvent interactions occurring between the various
components.
INTRODUCTION
3-methylimidazolium hexafluorophosphate, [C mIm][PF ],
4 6
■
17
introduced in constructing the optode membrane. A novel
Schiff base extracting agent (PMBP-2-ABT) was synthesized
and used for the extraction of heavy metal ions by PMBP-2-
ABT/IL binary-water phase system. In IL binary-water phase
system, PMBP-2-ABT was an excellent extracting agent for
Ionic liquids (ILs) are a new class of organic salts containing an
asymmetric organic cation and noncoordinating inorganic
anion. Owing to their unique chemical and physical properties,
−
10
such as negligible vapor pressure ([C mIm][PF ] is 10 Pa at
4
6
1
2
98 K), good thermal stability, a wide liquid range, excellent
18
heavy metal ions.
solvent power for organic and inorganic and polymeric
compounds, suitable viscosity, and nonflammability, easy
recyclability, and reusability, they have been recognized as an
The generalized use of these new compounds needs an
accurate knowledge of their thermodynamic properties both
when pure and when they are mixed with compounds. The
study of thermodynamic properties of Schiff base in the
presence of IL mixtures is crucial from a technological point of
view, but it also provides a better understanding of the
mechanisms involved when using these new media. For
example, their volumetric and viscometric properties of the
mixtures have been used to provide information on solute−
solvent interactions in mixtures. However, there are not any
reports on the thermodynamic properties of Schiff base ligand
in the presence of ILs according to our literature survey.
This work is a continuation of systematic studies on the
thermodynamic properties of Schiff base ligands in the presence
of ILs. In this work, we report the density, d, and viscosity, η, of
N,N′-salicylidenephenylenediamine (Salophen) Schiff base
2
−5
alternative solvent for organic and inorganic synthesis.
Recently, ILs have been applied to transition metal catalysis
containing Schiff base ligands with the benefit of a convenient
catalyst separation, hence, an easy recovery/recycling proce-
dure. The efficiency of such a catalyst/IL system is strongly
dependent on the nature of the ILs. The presence of ILs
modifies many important properties of transition metal catalysis
containing a Schiff base and their derivatives related to their
thermophysical properties, such as density and viscosity. The
Schiff base ligand has imine groups that are produced by the
condensation reactions of aldehydes, ketones, or β-ketones with
primary amines and related derivatives which are used
extensively, as important groups of ligands in coordination
6
−16
chemistry, medicine, agriculture, industry, and electronics.
(
Figure 1) + IL + N,N-dimethylformamide (DMF) ternary
mixtures at several concentrations of ILs. The ILs were: 1-
propyl-3-methylimidazolium bromide ([C mIm][Br]), 1-butyl-
Some studies have been reported on the application of ILs in
the processes containing the Schiff base ligand. A new cyanide
optode was designed using a [N,N′-bis(salicyliden)-2,3-
diaminopyridine] tributylphosphine cobalt(III) percholorate
monohydrate complex. The reduction in the absorbance value
of the optode at the maximum wavelength of 380 nm was
related to cyanide concentration in aqueous samples. The
sensitivity of the method was improved by using an IL, 1-butyl-
3
3
-methylimidazolium bromide ([C mIm][Br]), 1-pentyl-3-
4
Received: August 7, 2011
Accepted: January 8, 2012
Published: January 26, 2012
©
2012 American Chemical Society
345
dx.doi.org/10.1021/je200872n | J. Chem. Eng.Data 2012, 57, 345−351

Journal of Chemical & Engineering Data
Article
−1
H, 4.9; N, 8.98. IR (KBr, cm ): 1613 [υ (CN)], 3442 [υ
1
(
(
OH)]. H NMR (500 MHz) chemical shift (δ ppm), 12.95
s, 2H, OH), 8.49 (s, 2H, CHN), 6.60−7.33 (m, 12H, H-
aryl). Elemental analyses (C, H, and N) were performed using a
Heraeuse elemental analyzer CHN-O-Rapid (Elemental-Anal-
yses system, GmbH).
Apparatus and Procedure. The ternary mixtures
containing IL, Salophen Schiff base, and DMF were prepared
by weight and filling glass vials and closing them tightly. The
sample was taken from the vial with a syringe and immediately
injected into the apparatus. The mass of chemicals was
determined using an analytical balance (Sartorius AG
TE214S) with an uncertainty of ± 1·10− kg.
7
The densities of mixtures were measured using a vibrating
tube densimeter (DMA 4500M, Anton Paar, Austria). The
apparatus was calibrated with doubly distilled, deionized, and
degassed water and dry air at atmospheric pressure. Density is
extremely sensitive to temperature, so it was kept constant
within ± 1·10− K using the built-in Peltier technique. The
reproducibility of density measurements was better than ±
Figure 1. Structure of the N,N′-salicylidenephenylenediamine Schiff
base (Salophen).
methylimidazolium bromide ([C mIm][Br]), and 1-hexyl-3-
5
methylimidazolium bromide ([C mIm][Br]). Apparent molar
6
3
volumes, V , of Salophen were calculated at 298.15 K and used
ϕ
0
ϕ
to calculate the standard partial molar volumes, V , and transfer
partial molar volumes, Δ V . The viscosity B-coefficients were
0
ϕ
−5
−3
5·10 g·cm . Triplicate measurements were done to obtain
tr
calculated by using the Jones−Dole equation. All of these
parameters were used to investigate the effect of IL on the
thermodynamic properties of Salophen Schiff base and
interpret the solute−solute and solute−solvent interactions
occurring between the various components in these types of
ternary mixtures.
the average values of density.
The viscosities were measured using an Ubbelohde-type
̈
viscometer, which has a flow time of about 230 s for water at
298.15 K. The viscometer was calibrated with doubly distilled
deionized water. The viscosity of mixture, η, is given by the
following equation
η
= Lt − Kt
EXPERIMENTAL SECTION
■
(1)
d
Chemicals. Reagents used in this work were N-methyl-
imidazole (>99 %, in mass fraction), 1-bromopropane (>99 %,
in mass fraction), 1-bromobutane (>99 %, in mass fraction), 1-
bromopentane (>99 %, in mass fraction), and 1-bromohexane
where d is the density, t is the flow time of the mixture, and L
and K are the viscometer constants. A digital stopwatch with a
precision of 0.01 s has been used for the flow time
measurement. The temperature was controlled using a
circulating bath thermostat (Julabo NP, Germany) with a
temperature stability of ± 0.01 K. The measured physical
properties of DMF and their values reported in literature are
given in Table 1.
(
>99 %, in mass fraction) purchased from Merck, the
salicylaldehyde (99 %, in mass fraction) obtained from Fluka,
and N,N-dimethylformamide (99.5 %, in mass fraction)
obtained from Rankem (India). These reagents were used
without further purification.
Synthesis of ILs. ILs ([C mIm][Br]) were prepared and
purified by using the procedure described in the literature.
n
1
9,20
Table 1. Density, d, Viscosity, η, and Refractive Index, n , of
D
Briefly, [C mIm][Br] was synthesized by direct alkylation of N-
Pure Dimethylformamide (DMF) at T = 298.15 K
n
methylimidazole with an excess of 1-bromoalkane in a round-
bottom flask at about 353 K for 48 h under a nitrogen
atmosphere. The product was dried in high vacuum at 333.15 K
using a rotary evaporator for at least 4 h in reduced pressure.
The synthesized ILs have a purity greater than mass fraction
d
η
g·cm3
mPa·s
nD
0.94400 (exp.)
0.805 (exp.)
1.4281 (exp.)
3
1
33
29
0.94446
0.94380
0.8605
1.4267
29
32
30
0
.98, which was used after vacuum desiccated for at least 48 h
to remove a trace amount of moisture. The water contents in
0.803
1.4275
30
34
0.9445
1.4282
the [C mIm][Br] were found by the Karl Fischer method to be
n
1
less than mass fraction 0.05 %. ILs were analyzed by H NMR
RESULTS AND DISCUSSION
(
Bruker Av-300) and FT-IR (Perkin Elmer, Spectrum RXI)
■
spectra to confirm the absence of any major impurities and
were found to be in agreement with those reported in the
literature.
Volumetric Properties. The experimental densities, d, of
ternary Salophen + [C mIm][Br] + DMF mixtures as a
2
1
n
function of Salophen molality, m, at different molalities of ILs
Synthesis of Salophen Schiff Base. To a vigorously
stirred ethanolic mixture (40 mL) of salicylaldehyde (20 mmol)
was added dropwise a mixture of 1,2-diaminobenzene (10
mmol) in 40 mL of ethanol. After the addition was complete,
the mixture was stirred and refluxed for 60 min. The mixture
was then cooled, and the orange precipitate of the ligand was
collected by filtration, then washed with ethanol and dried in a
desiccator. Yield of Salophen: 2.69 g (85 %). Anal. Calcd for
C H Br N O : C, 75.93; H, 5.10; N, 8.85. Found: C, 75.74;
(
m ) are reported in Table 2 at 298.15 K. The concentration
IL
range studied for both ILs and Salophen was in the dilute
region, (0 to 0.2) mol·kg . For each concentration of IL, the
densities of the mixtures increase with increasing Salophen
concentration. The apparent molar volumes, V , of Salophen in
the DMF and reference solvent (DMF + [C mIm][Br]) were
calculated from the densities of the mixtures using the following
equation:
−1
ϕ
n
22
20
16
2
2
2
3
46
dx.doi.org/10.1021/je200872n | J. Chem. Eng.Data 2012, 57, 345−351

Journal of Chemical & Engineering Data
Article
Table 2. Densities, d, and Apparent Molar Volumes, V , of Salophen in the DMF + IL Mixture at 298.15 K
ϕ
a
m
d
Vϕ
m
d
Vϕ
m
d
Vϕ
m
d
Vϕ
mol·kg−
1
g·cm−3
cm ·mol
3
−1
mol·kg−1
g·cm−3
cm ·mol
3
−1
mol·kg−1
g·cm−3
cm ·mol
3
−1
mol·kg−1
g·cm−3
cm ·mol
3
−1
Salophen + [C mIm][Br] + DMF
3
m = 0.0000
IL
m = 0.0300
IL
m = 0.0789
IL
m = 0.1220
IL
0
0
0
0
0
0
0
0
0
0
.0000
.0295
.0510
.0697
.0894
.1106
.1299
.1465
.1701
.1898
0.94400
0.94601
0.94747
0.94875
0.95008
0.95151
0.95282
0.95394
0.95551
0.95683
0.0000
0.0506
0.0697
0.0894
0.1103
0.1299
0.1499
0.1693
0.1856
0.2095
0.94619
0.94965
0.95094
0.95228
0.95368
0.95499
0.95631
0.95758
0.95864
0.96019
0.0000
0.0507
0.0697
0.0901
0.1087
0.1293
0.1515
0.1700
0.1921
0.2132
0.94963
0.95308
0.95436
0.95573
0.95696
0.95832
0.95978
0.96098
0.96241
0.96377
0.0000
0.0491
0.0691
0.0897
0.1089
0.1296
0.1501
0.1685
0.1895
0.2110
0.95252
0.95585
0.95719
0.95856
0.95983
0.96119
0.96252
0.96372
0.96506
0.96642
258.06
257.82
257.44
257.23
256.90
256.59
256.31
256.13
255.85
257.05
256.95
256.68
256.50
256.36
256.26
256.14
256.10
255.95
256.85
256.64
256.50
256.43
256.29
256.13
256.07
255.98
255.84
256.56
256.45
256.32
256.20
256.08
256.03
255.91
255.86
255.82
Salophen + [C mIm][Br] + DMF
4
m = 0.1012
IL
m = 0.1527
IL
m = 0.1970
IL
0
0
0
0
0
0
0
0
0
0
.0000
.0099
.0296
.0502
.0698
.0908
.1106
.1300
.1509
.1697
0.95101
0.95169
0.95303
0.95443
0.95576
0.95717
0.95849
0.95978
0.96117
0.96240
0.0000
0.95440
0.95506
0.95639
0.95776
0.95906
0.96023
0.96174
0.96309
0.96443
0.96572
0.0000
0.95720
0.95796
0.95920
0.96057
0.96196
0.96349
0.96451
0.96578
0.96738
0.96855
256.73
256.70
256.39
256.17
255.99
255.92
255.75
255.52
255.41
0.0097
0.0292
0.0495
0.0689
0.0865
0.1092
0.1298
0.1504
0.1702
256.35
256.28
256.17
255.97
255.97
255.75
255.71
255.62
255.48
0.0111
0.0293
0.0497
0.0705
0.0935
0.1090
0.1285
0.1533
0.1714
255.72
255.55
255.61
255.58
255.42
255.39
255.36
255.36
255.23
Salophen + [C mIm][Br] + DMF
5
m = 0.0260
IL
m = 0.0508
IL
m = 0.0747
IL
0
0
0
0
0
0
0
0
0
0
.0000
.0292
.0496
.0698
.0916
.1090
.1301
.1499
.1712
.1912
0.94747
0.94947
0.95086
0.95224
0.95372
0.95488
0.95631
0.95764
0.95906
0.96039
0.0000
0.94926
0.95119
0.95267
0.95399
0.95536
0.95669
0.95793
0.95932
0.96061
0.96216
0.0000
0.0287
0.0496
0.0702
0.0905
0.1093
0.1295
0.1516
0.1696
0.1915
0.95079
0.95277
0.95419
0.95559
0.95695
0.95821
0.95955
0.96101
0.96220
0.96363
255.69
255.55
255.55
255.39
255.15
255.42
255.19
255.13
254.46
0.0282
0.0498
0.0693
0.0895
0.1094
0.1279
0.1486
0.1682
0.1917
256.78
256.40
256.28
256.06
255.91
255.75
255.49
255.38
255.18
256.33
256.07
255.90
255.79
255.66
255.62
255.43
255.30
255.17
Salophen + [C mIm][Br] + DMF
6
m = 0.0245
IL
m = 0.0738
IL
m = 0.1205
IL
0
0
0
0
0
0
0
0
0
0
.0000
.0490
.0690
.0924
.1122
.1292
.1466
.1716
.1906
.2100
0.94576
0.94911
0.95047
0.95206
0.95340
0.95454
0.95570
0.95735
0.95863
0.95988
0.0000
0.94890
0.95251
0.95378
0.95512
0.95649
0.95765
0.95907
0.96011
0.96171
0.96313
0.0000
0.0492
0.0685
0.0903
0.1110
0.1279
0.1523
0.1714
0.1900
0.2181
0.95172
0.95512
0.95643
0.95790
0.95929
0.96041
0.96202
0.96325
0.96446
0.96625
256.06
256.11
256.02
255.83
255.75
255.66
255.56
255.29
255.30
0.0523
0.0709
0.0907
0.1110
0.1285
0.1498
0.1656
0.1901
0.2122
255.78
255.69
255.56
255.48
255.48
255.32
255.26
255.15
255.13
255.43
255.23
255.23
255.11
255.13
255.03
255.08
255.01
255.00
a
mIL is the molality of IL where solvent is DMF, and m is the molality of Salophen where solvent is (DMF + IL).
uncertainty of calculated apparent molar volumes was less than
± 0.06 cm .mol .
Vϕ = Md
−
1000(d − d0)
3
−1
mdd0
(2)
The variation of apparent molar volumes with respect to
23
concentration is expressed by the following equation:
where M is the molar mass of the Salophen Schiff base, m is the
molality of the Salophen in ternary mixtures of Salophen +
C mIm][Br] + DMF, d and d are the densities of (Salophen +
n 0
C mIm][Br] + DMF) mixtures and reference solvent (desired
0
V = V + S ·m
ϕ
ϕ
v
(3)
[
[
0
ϕ
n
where V is the value of the limiting apparent molar volumes
molality of [C mIm][Br] in DMF), respectively. The maximum
that equals the standard partial molar volume of the solute, and
n
3
47
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Journal of Chemical & Engineering Data
Article
0
0
Table 3. Standard Partial Molar Volumes, V , Transfer Partial Molar Volumes, Δ V , Experimental Slopes, S , and Standard
ϕ
tr
ϕ
v
Deviations of Apparent Volumes, σ(V ), of Salophen in DMF + [C mIm][Br] Mixtures
ϕ
n
0
ϕ
0
ϕ
mIL
V
Sv
ΔtrV
1
3
−1
3
−2
3
−1
system
Salophen + DMF
mol·kg−
cm ·mol
cm ·mol ·kg
cm ·mol
σ(Vϕ)
0.0000
0.0300
0.0789
0.1220
0.1012
0.1527
0.1970
0.0260
0.0508
0.0747
0.0205
0.0738
0.1205
258.47 ± 0.05
257.34 ± 0.06
257.07 ± 0.04
256.75 ± 0.04
256.84 ± 0.04
256.41 ± 0.03
255.71 ± 0.03
257.47 ± 0.06
256.94 ± 0.04
256.43 ± 0.04
256.44 ± 0.07
255.97 ± 0.03
255.43 ± 0.06
−14.07 ± 0.40
−6.95 ± 0.46
−5.91 ± 0.27
−4.75 ± 0.28
−8.57 ± 0.41
−5.47 ± 0.27
−2.66 ± 0.33
−12.26 ± 0.48
−9.43 ± 0.36
−6.66 ± 0.33
−5.48 ± 0.48
−4.18 ± 0.22
−2.19 ± 0.39
0.06
0.07
0.04
0.04
0.06
0.04
0.05
0.07
0.06
0.05
0.07
0.03
0.06
Salophen + DMF + [C mIm][Br]
−1.11
−1.40
−1.72
−1.61
−2.06
−2.76
−1.00
−1.51
−2.04
−2.03
−2.50
−3.03
3
Salophen + DMF + [C mIm][Br]
3
Salophen + DMF + [C mIm][Br]
3
Salophen + DMF + [C mIm][Br]
4
Salophen + DMF + [C mIm][Br]
4
Salophen + DMF + [C mIm][Br]
4
Salophen + DMF + [C mIm][Br]
5
Salophen + DMF + [C mIm][Br]
5
Salophen + DMF + [C mIm][Br]
5
Salophen + DMF + [C mIm][Br]
6
Salophen + DMF + [C mIm][Br]
6
Salophen + DMF + [C mIm][Br]
6
S is the experimental slope. The sign of S shows the nature of
Salophen with an increasing alkyl chain length of IL and
ν
v
0
the solute−solute interactions, while V values reflect the
preferential solvation of Salophen with [C mIm][Br].
ϕ
n
2
4,25
presence of solute−solvent interactions.
The plots of
The same result can also be obtained from the partial molar
volume of transfer for the Salophen from DMF to DMF + IL
solutions. Limiting thermodynamic properties of transfer yield
qualitative and quantitative information regarding the inter-
actions of a cosolute and a solute without having to take into
account the effects of solute−solute interactions as at infinite
dilution the interactions between solute molecules are
apparent molar volumes versus m were linear, and using the
0
ϕ
least-squares treatment, the values of V and S can be obtained
v
0
ϕ
from the intercept and slope, respectively. The values of V and
S along with their standard deviations are given in Table 3. The
v
0
ϕ
values of V shown in this table decrease with an increase in
concentration of IL which indicate that the solvent molecules
0
ϕ
(
DMF) are loosely attached to Salophen Schiff base, thus
negligible. The partial molar volumes of transfer, Δ V , for
tr
0
resulting in lower values of V at higher concentrations of ILs.
the Salophen from DMF to [C mIm][Br] + DMF mixtures
n
23
ϕ
The S values as shown in Table 3 are negative and increase
were calculated as follows:
v
with an increase of IL concentration, suggesting weak solute−
0
0
solute interactions, but these interactions increase with the
Δ V = V (in [C mIm][Br] + DMF)
tr
ϕ
ϕ
n
0
ϕ
increase in IL concentration. As can be seen, the V values of
0
Salophen Schiff base are also greater than their values for Salen
Schiff base reported in our previous paper due to the higher
− V (in DMF)
ϕ
(4)
26
0
ϕ
intrinsic volume of Salophen.
The Δ V values have negative values in this mixture and
tr
decrease with increasing concentration and alkyl chain length of
C mIm][Br]. According to the cosphere overlap model of
[
n
ternary mixtures, four types of interactions may occur between
the Salophen and the [C mIm][Br] molecules in DMF: (a) the
n
polar−ionic group interactions between the ionic centers of
[
C mIm][Br] and OH groups of Salophen Schiff base, (b)
n
polar−polar group interactions between the OH groups of
Salophen Schiff base and the amine group of [C mIm][Br]
n
through the hydrogen bonding, (c) polar−nonpolar group
interactions between the OH groups of Salophen Schiff base
and alkyl group attached to the imidazolium ring of
[
C mIm][Br] and amine groups of [C mIm][Br] and nonpolar
n
n
groups of Salophen, and (d) nonpolar−nonpolar group
interactions between the aromatic and CH groups of Salophen
Figure 2. Comparison of apparent molar volumes of Salophen in
−
1
(
[
Salophen + DMF + [C mIm][Br] (0.1 mol·kg )) mixtures. ⧫,
and alkyl group attached to the imidazolium ring of
n
▲
, [C mIm][Br]; ×, [C mIm][Br]; +, [C mIm][Br] at
27
C mIm][Br];
3
4
5
6
[C mIm][Br]. Taking the cosphere overlap model as the
n
298.15 K.
guideline, polar−nonpolar group interactions and nonpolar−
0
ϕ
nonpolar group interactions would lead to a negative Δ V ,
tr
The values of V for Salophen Schiff base in ([C mIm][Br]
.1 mol·kg− + DMF) mixtures have been compared together
Figure 2). The values of V for Salophen in the investigated
ϕ
n
since the introduction of the alkyl group provides an additional
tendency of polar−nonpolar and nonpolar−nonpolar groups to
interact and as a result there will be a reduction in the structure
of solvent formed as a result of their cospheres overlapping. In
this case the c and d types of interactions are dominant
between ILs and Salophen Schiff base.
1
0
0
ϕ
(
mixtures have the order: [C mIm][Br] > [C mIm][Br] >
3
4
[
C mIm][Br] > [C mIm][Br]. These values are decreasing
5 6
with alkyl chain length of [C mIm][Br]. It is concluded that
n
Viscometric Results. The measured viscosities, η, for
there are weak solute−solvent interactions between DMF and
(Salophen Schiff base + [C mIm][Br] + DMF) ternary
n
3
48
dx.doi.org/10.1021/je200872n | J. Chem. Eng.Data 2012, 57, 345−351

Journal of Chemical & Engineering Data
Article
Table 4. Viscosities, η, of Salophen Schiff Base in DMF + [C mIm][Br] Mixtures at 298.15 K
n
m*
η
m
η
m
η
m
η
mol·kg−
1
mPa·s
mol·kg−1
mPa·s
mol·kg−1
mPa·s
mol·kg−1
mPa·s
Salophen + [C mIm][Br] + DMF
3
*
m = 0.0000
IL
m = 0.0300
IL
m = 0.0789
IL
m = 0.1220
IL
0
0
0
0
0
0
0
0
0
.0100
.0302
.0505
.0698
.0851
.1098
.1268
.1507
.1705
0.802
0.818
0.833
0.847
0.859
0.878
0.890
0.905
0.919
0.0506
0.0697
0.0894
0.1103
0.1299
0.1499
0.1693
0.1856
0.2095
0.829
0.841
0.852
0.866
0.882
0.897
0.912
0.923
0.940
0.0507
0.0697
0.0901
0.1087
0.1293
0.1515
0.1700
0.1921
0.2132
0.854
0.871
0.883
0.900
0.912
0.929
0.943
0.958
0.970
0.0491
0.0691
0.0897
0.1089
0.1296
0.1501
0.1685
0.1895
0.2110
0.877
0.892
0.908
0.922
0.939
0.951
0.964
0.977
0.993
Salophen + [C mIm][Br] + DMF
4
m = 0.1012
IL
m = 0.1520
IL
m = 0.1970
IL
0
0
0
0
0
0
0
0
0
.0100
.0296
.0502
.0698
.0908
.1106
.1300
.1509
.1697
0.872
0.887
0.903
0.919
0.932
0.947
0.958
0.970
0.983
0.0097
0.0292
0.0495
0.0689
0.0865
0.1092
0.1298
0.1504
0.1702
0.886
0.897
0.911
0.927
0.940
0.954
0.967
0.981
0.993
0.0111
0.0293
0.0497
0.0705
0.0935
0.1090
0.1285
0.1533
0.1714
0.918
0.927
0.939
0.950
0.968
0.978
0.990
1.001
1.010
Salophen + [C mIm][Br] + DMF
5
m = 0.0260
IL
m = 0.0508
IL
m = 0.0747
IL
0
0
0
0
0
0
0
0
0
.0489
.0672
.1009
.1081
.1265
.1473
.1675
.1923
.2085
0.827
0.843
0.860
0.876
0.890
0.903
0.917
0.931
0.944
0.0282
0.0498
0.0693
0.0895
0.1094
0.1279
0.1486
0.1682
0.1917
0.836
0.855
0.871
0.885
0.898
0.910
0.924
0.938
0.953
0.0287
0.0496
0.0702
0.0905
0.1093
0.1295
0.1516
0.1696
0.1915
0.852
0.864
0.876
0.888
0.901
0.917
0.934
0.947
0.962
Salophen + [C mIm][Br] + DMF
6
m = 0.0205
IL
m = 0.0738
IL
m = 0.1205
IL
0
0
0
0
0
0
0
0
0
.0490
.0690
.0924
.1122
.1292
.1466
.1716
.1906
.2100
0.852
0.864
0.876
0.888
0.901
0.917
0.934
0.947
0.962
0.0523
0.0709
0.0907
0.1110
0.1285
0.1498
0.1656
0.1901
0.2122
0.880
0.889
0.902
0.914
0.924
0.941
0.953
0.966
0.983
0.0492
0.0685
0.0903
0.1110
0.1279
0.1523
0.1714
0.1900
0.2181
0.939
0.950
0.964
0.977
0.989
1.001
1.018
1.031
1.042
*
mIL is the molality of IL where solvent is DMF + and m is the molality of Salophen where solvent is (DMF + IL).
mixtures as a function of Salophen molality, m, at different
concentrations of ILs at 298.15 K are tabulated in Table 4. The
estimated uncertainty of the experimental viscosity data was ±
η
η0
=
1 + Ac1/2 + Bc
(5)
0
.003 mPa·s. The results show an increase in the viscosity of
mixtures studied with an increase in concentration of ILs,
C mIm][Br]. This is due to the fact that, with the increasing of
where η and η are the viscosities of (Salophen Schiff base +
0
[
C mIm][Br] + DMF) ternary mixtures and reference solvent
([C mIm][Br] + DMF), respectively, and c is the molar
n
[
n
n
IL concentration, the number of collision between the
molecules also increases to result in a loss of kinetic energy;
therefore, the molecules tend to stack together to induce the
increase in the viscosity. Most studies on viscosity are confined
to the description of dilute mixtures of solutes via
determination of the B-coefficients in the Jones−Dole
concentration (calculated from molality) of Salophen Schiff
base in the (Salophen Schiff base + [C mIm][Br] + DMF)
n
ternary mixtures. The A-coefficient is a measure of solute−
solute interactions which are very small and then ignored in this
equation. The viscosity B-coefficient is an empirical constant
which depends on solute−solvent interactions and structural
factors. The calculated B values along with their standard
2
8
equation:
3
49
dx.doi.org/10.1021/je200872n | J. Chem. Eng.Data 2012, 57, 345−351

Journal of Chemical & Engineering Data
Article
deviations are given in Table 5 by fitting the experimental
viscosity data to the Jones−Dole equation. The viscosity B-
Table 5. The Values of Viscosity B-Coefficients, Solvation
0
ϕ
Numbers (B/V ), and Related Standard Deviations σ(η) for
Salophen + DMF + [C mIm][Br] Ternary Mixtures at
n
298.15 K
mIL
B
mol·kg−
1
dm ·mol
3
−1
σ(η)·103
B/V0
ϕ
DMF + Salophen
0.844 ± 0.99·10−
3
1.49
3.27
0.0000
Salophen + [C mIm][Br] + DMF
3
3
3
3
Figure 3. Viscosities of (Salophen + DMF + [C mIm][Br] (0.1
n
0.0300
0.0789
0.1220
0.936 ± 3.92·10−
2.10
2.27
1.83
3.64
3.50
3.38
−1
0.899 ± 4.25·10−
mol·kg )) mixtures. ⧫, [C mIm][Br]; ▲, [C mIm][Br]; ×, [C mIm]-
3
4
5
0.869 ± 3.42·10−
[Br]; +, [C
6
mIm][Br] at 298.15 K.
Salophen + [C mIm][Br] + DMF
4
0
0.825 ± 5.41·10−
3
solvation number, B/V , for Salophen Schiff base in the
ϕ
0.1012
0.1527
0.1970
2.90
3.21
3.10
2.62
−
3
presence of ILs {1-propyl-3-methylimidazolium bromide
([C mIm][Br]), 1-butyl-3-methylimidazolium bromide
[C mIm][Br]), 1-pentyl-3-methylimidazolium bromide
([C mIm][Br]), and 1-hexyl-3-methylimidazolium bromide
([C mIm][Br])} in DMF mixtures decrease with the increasing
concentration and alkyl chain length of IL. This trend suggests
the dominance of nonpolar−nonpolar interactions between
Salophen and ILs. Also, the calculated solvation numbers, B/
0.796 ± 3.46·10
1.85
2.41
0.671 ± 4.51·10−
3
3
(
4
Salophen + [C mIm][Br] + DMF
5
0.929 ± 4.83·10−
3
5
0.0260
0.0508
0.0747
2.58
3.61
3.47
3.36
−3
6
0.892 ± 5.08·10
2.71
2.57
0.862 ± 4.80·10−
3
Salophen + [C mIm][Br] + DMF
6
0.895 ± 6.45·10−
0.758 ± 3.52·10−
0.736 ± 2.02·10−
3
3
3
0.0205
0.0738
0.1205
3.45
1.88
1.08
3.49
2.96
2.88
0
ϕ
V , for Salophen shows that its solute−solvent interactions
between Salophen and DMF decrease at high concentrations of
ILs and the preferential solvation of Salophen with [C mIm]-
n
[
Br].
coefficients decrease with increasing concentration, which
suggest the net structural decrease. Further, the viscosity B-
coefficients of Salophen in nonaqueous ILs solutions increase in
the order of [C mIm][Br] > [C mIm][Br] > [C mIm][Br] >
AUTHOR INFORMATION
■
Corresponding Author
*Tel.: 984113393139. Fax: 984113340191. E-mail address:
hemayatt@yahoo.com (H. Shekaari).
3
4
5
[
C mIm][Br]. It is well-known that the size, shape, and charge
6
of solute molecules are important in determining the viscosity
B-coefficients. In the case of studied ILs, the charge of ILs are
the same, hence the observed order of viscosity B-coefficients
may be rationalized in terms of the alkyl chain length of ILs.
Hence the higher values of the viscosity B-coefficient for the
Funding
The authors are grateful for the financial support from the
Graduate Council of the University of Mohaghegh Ardabili.
[
C mIm][Br] as compared to other studied ILs agree well with
3
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Journal of Chemical & Engineering Data
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