N-(2-hydroxyethyl)-ethylenediamine-based ionic liquids: Synthesis, structural characterization, thermal, dielectric and catalytic properties

Article abstract of DOI:10.1016/j.molliq.2012.10.040

Three novel acetate and formate ammonium salts of N-(2-hydroxyethyl)- ethylenediamine (Hydeten) were synthesized as room temperature ionic liquids (RTILs) {2-(2-hydroxy ethylamino)-ethanaminium formate (IL1a), 2-amino-N-(2-hydroxyethyl)-ethanaminium forma

Full text of DOI:10.1016/j.molliq.2012.10.040

Journal of Molecular Liquids 177 (2013) 369–375
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Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
N-(2-hydroxyethyl)-ethylenediamine-based ionic liquids: Synthesis, structural
characterization, thermal, dielectric and catalytic properties
⁎
Ahmet Karadağ , Ali Destegül
Department of Chemistry, Gaziosmanpasa University, Tokat, 60400, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 25 June 2012
Received in revised form 11 September 2012
Accepted 31 October 2012
Available online 24 November 2012
Three novel acetate and formate ammonium salts of N-(2-hydroxyethyl)-ethylenediamine (Hydeten) were syn-
thesized as room temperature ionic liquids (RTILs) {2-(2-hydroxy ethylamino)-ethanaminium formate (IL1a),
2-amino-N-(2-hydroxyethyl)-ethanaminium formate (IL1b), and 2-(2-hydroxyethylamino)-ethanaminium ac-
etate (IL2)}. Their structures were characterized by using elemental analysis, FT-IR, 1H and 13C NMR techniques.
Some thermal properties of these ILs were determined by using TG and DSC techniques. Real dielectric
(ε′)-frequency (ω), imaginary dielectric (ε″)-frequency (ω), and conductivity (σAC)-frequency (ω) relationships
of IL1a–b, IL2, and doped IL1–2 were investigated. These ILs were also tested as solvent or catalyst in the synthe-
sis of some organic compounds.
Keywords:
Ionic liquids
N-(2-hydroxyethyl)ethylenediamine
Catalyst
© 2012 Elsevier B.V. All rights reserved.
Thermal analysis
Dielectric property
1. Introduction
asymmetric synthesis, polymers, and biomaterials and material science
[11–19].
Ionic liquids (ILs) are molten salts having a melting point at room or
lower temperatures. Generally, ILs are liquid at temperatures less than
100 °C and can remain as stable liquids over a wide temperature
range, making them stable polar solvents for organic transformations
in industrial processes. Ionic liquids (ILs) have recently received tre-
mendous attention in several branches of the chemical industry as
green chemicals instead of traditional solvents [1–5]. The main advan-
tages of ILs as compared to common molecular organic solvents are
their negligible vapor pressure resulting in reduced inhalatory expo-
sure, absence of flammability, and their high variability concerning
chemical structure of head groups, substituents and anions. Due to
their lower vapor pressures and lack of flammability, ILs are good can-
didates for replacement of toxic and volatile organic compounds. ILs
generally constitute of a pair of a cation like ammonium, phosphonium,
pyridinium, imidazolium, or cholinium cation and an anion like a fluo-
rinated anion. The cation–anion combinations have been extensively
studied for physical properties of ILs. These variability and combina-
tions thereof lead to an enormous number of theoretically accessible
ILs. The technical applicability of ILs depends upon modification of
structural elements in order to optimize properties like solvation, vis-
cosity, conductivity and thermal properties as well as electrochemical
stability [6–10]. ILs have been extensively reviewed over the years in
case of applications including organic synthesis, electrochemistry, chro-
matography, transition metal catalysis, biocatalytic transformations,
Ionic liquids referred to as room temperature ionic liquids (RTILs)
are salts which can be liquid at room or lower temperatures. Most of
the RTILs have very low melting points attributed to the asymmetrical
nature of the ions which prevents the compact packing [12]. The in-
creasing importance of RTILs is associated with their desirable prop-
erties such as almost no vapor pressure, resulting in their low
volatility, non-flammability, thermal stability and recyclability. RTILs
are also important with the properties of tunable density, viscosity,
polarity, melting point, refractive index by modifying the structures
of their cation and anion components [20]. In this study, the three
ionic liquids which are liquids at room temperature were synthe-
sized. The compositions of these ILs were confirmed by elemental
analysis, FT-IR and NMR techniques. Thermal, dielectric and catalysis
properties of new ILs were also investigated.
2. Experimental details
2.1. Materials and instrumentation
N-(2-hydroxyethyl)-ethylenediamine {alternatively named 2-
(2-aminoethylamino)ethanol} (C4H12N2O), HCOOH, CH3COOH, KCl,
CaCl2 and MnCl2 were purchased from commercial sources and
used without further purification.
All ILs were characterized by NMR spectra using 1D and 2D NMR
techniques. For the NMR measurements, the ILs were purified under
vacuum and then samples were then diluted in CDCl3 NMR spectra
measured with a Bruker Avance-III spectrometer with 1H and 13C reso-
nance frequencies of 400 and 100 MHz, respectively, at 298 K. The
⁎
Corresponding author. Fax: +90 356 2521582.
E-mail address: ahmet.karadag@gop.edu.tr (A. Karadağ).
0167-7322/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molliq.2012.10.040

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A. Karadağ, A. Destegül / Journal of Molecular Liquids 177 (2013) 369–375
assignment of the 1H and 13C signals of ILs was determined from 2D
NMR of 1H–1H COSY, 1H–13C HETCOR and 1H–13C HMBC spectra. 1H
NMR and 13C NMR spectra for ILs were recorded. No extra peak was
found in all spectra. IR spectra were recorded on a Jasco FT/IR 430
spectrometer in KBr disks and reported in cm−1 units. The TG and
DTG curves were obtained using a PYRIS Diamond TG/DTA apparatus
in a dynamic nitrogen atmosphere (heating rate: 5 °C/min, platinum
crucibles, mass ~10 mg and temperature range 30–750 °C). Dielectric
measurements of the ILs were performed with a Hewlett-Packard
4194A Impedance/Gain-Phase Analyzer. The samples were placed into
glass cells having 5 Å spacing between ITO-coated internal surfaces
(Gebze Institute of Technology, TURKEY). Also, all reactions were mon-
itored on an Agilent 6890N GC system by GC-FID with a HP-5 column of
30 m length, 0.32 mm diameter and 0.25 μm film thicknesses for catal-
ysis studies. Column chromatography was performed by using silica gel
60 (70–230 mesh) (solvent ratios are given as v/v) (İnönü University,
Turkey).
Table 1
Infrared spectra data for Hydeten, IL1a–b and IL2.
Groups (1/λ, cm−1
)
Hydeten
IL1a,b
IL2
ν (O\H)
ν (N\H)
ν (C\H)
ν (C\N) (\HN\CH2\)
ν(C\O)
δ(N\H)
δ(CH2)
ν (C\H) (\O\CH_O)
ν (C_O)
δ(C\H) (CH3\C_O)
3352
3288
2939–2862
1122
1053
3361
3286
2943–2881
1122
1061
1587
1456
1376
1656
3369
1081
1018
1562
1338
1571
1471
1646
1407
from acetic acid in the IR spectrum of IL2 appeared to 1646 cm−1 and
1407 cm−1. The C\H stretching vibration frequencies of the CH3 of
CH3\C_O group are expected in the range of 3300–2400 cm−1, but
due to very broad and strong O\H and N\H stretching vibration
bands overlapping in these ranges, the C\H stretching bands were
seen as a shoulder in broad peaks.
2.2. Synthesis
A mixture of Hydeten (5.15 g, 49.45 mmol) and formic acid (2.27 g,
49.32 mmol) or acetic acid (2.97 g, 49.46 mmol) is prepared in the
molar ratio 1:1. Hydeten is placed in
Three 2-(2-aminoethylamino)-ethanol based RTILs differing in their
acetate and formate anions and protonated amino side are shown in
Scheme 2. To evaluate the flexibility of the different anions, mostly pri-
mary amino group captured the acidic proton to give ammonium salt
determined at the NMR spectra was observed. Since ILs were diluted
in solvents for NMR measurements, the mobility of a substituent etha-
nol group in the ammonium cation was only observed for the free ion
in IL1b. IL1a and IL2 illustrate the free ions on seventy amino groups
as shown in Scheme 2.
a
two-necked 100 cm3
round-bottomed flask, which is fitted with a dropping funnel, and
connected to a condenser. Formic acid or acetic acid is placed in the
dropping funnel, and added the acid dropwise to the Hydeten in the
flask. The reaction is vigorous and the rate is controlled by regulating
the addition of acid. The reaction should be complete in about 24 h.
The product should be viscose orange-yellow liquid. The most probable
formation reactions of IL1a, IL1b and IL2 are illustrated in Scheme 1.
Anal. Calc. (%) for C5H14N2O3 (IL1a–b): C, 39.99; H, 9.40; N, 18.65.
Found: C, 40.53; H, 9.34; N, 18.70 and Anal. Calc. (%) for C6H16N2O3
(IL2): C, 43.89; H, 9.82; N, 17.06. Found: C, 44.26; H, 9.69; N, 17.50%.
It can be seen that the change in 13C and 1H chemical shifts due to
the protonation on nitrogen is different for the various carbon/proton
types in the 2-(2-aminoethylamino)-ethanol molecule. Jakobsen et al.
stated that the protonation on the nitrogen atom has a major effect
on the carbon in β-position and the proton in α-position to that ni-
trogen [21]. In the first protonation stage, the protons will associate
with both the primary and secondary amine groups in a certain
ratio which cannot be determined from the experiments, but is as-
sumed to be 80–90% with the primary group. This assumption, that
the first protonation involves mainly the primary nitrogen group, is
supported by the fact that the first protonation shift is largest for
C3 and H4, i.e., the β-carbon and α-proton related to the primary ni-
trogen, respectively. Similarly, in the second protonation stage the
protons may associate with both the primary and secondary groups
depending on where the first protonation took place. Since the majority
of 2-(2-aminoethylamino)-ethanol molecules are assumed to be
3. Results and discussion
3.1. IR and NMR spectra
Characteristic IR absorption bands of the Hydeten, IL1a–b and IL2
were given in Table 1. Comparing the IR spectrum of the IL1a–b with
pure Hydeten, it is understood that bands at 1656 cm−1 and
1376 cm−1 different from the stretching and bending vibrations of
Hydeten corresponded to the C_O and C\H (\O\CH_O) stretching
frequencies coming from formic acid. On the other hand, it is seen
that the C_O stretching and C\H (CH3\C_O) bending bands coming
H
H
N
O
O
N
+
H
O
H
O
H2N
H
O
O
H3N
[Hydeten]+[HCOO]- (IL1a
)
O
O
H2
N
H
N
O
+
H
O
H
O
H2N
H
O
H2N
[Hydeten]+[HCOO] -(IL1b
)
H
H
N
O
N
O
+
H
O
H
O
H2N
H
O
H3N
O
[Hydeten]+[CH3COO]- (IL
2)
Scheme 1. The possible formation reactions of IL1a, IL1b and IL2.

A. Karadağ, A. Destegül / Journal of Molecular Liquids 177 (2013) 369–375
371
O
O-
8
O
H2
2
2
6
H
N
4
N
1
H
O
1
O
6
O-
4
H2N
H3N
7
H
8
3
5
3
5
7
2-(2-hydroxyethylamino)ethanaminium formate (IL1a
)
2-amino-N-(2-hydroxyethyl)ethanaminium formate (IL1b)
O
2
H
N
4
1
6
8
O-
H3N
H
O
3
5
7
9
2-(2-hydroxyethylamino)ethanaminium acetate (IL2)
Scheme 2. Molecular structures of 2-(2-hydroxyethylamino)ethanaminium formate (IL1a), 2-amino-N-(2-hydroxyethyl)ethanaminium formate (IL1b), and 2-(2-hydroxy
ethylamino)ethanaminium acetate (IL2).
protonated on the primary nitrogen group in the first stage, the second
protonation can be associated with protonation on the secondary nitro-
gen group. There the shift is largest for the β-carbons C1 and C4 and the
α-proton H3 related to the secondary nitrogen group.
primary and secondary protonation of amines and evaluated the an-
alog of the protonated form (see Fig. 2).
The 1H, 13C and DEPT NMR results of IL1a–b and IL2 are summarized
in Table 2. As shown in this table, 1H and 13C NMR values of CH3 group
which is decisive for IL2 were found as 1.58 ppm and 23.43 ppm, re-
spectively. The molecular structure of IL2 drawn using ChemBioOffice
was given in Fig. 3.
The atomic numbering is also shown on each chemical structure in
Scheme 2. As in the case of 2-(2-aminoethylamino)-ethanol, the nitrogen
groups are protonated and we cannot distinguish in the NMR spectra be-
tween the species and their protonated form because the proton ex-
change is fast with respect to the NMR time scale. Therefore, the
integrated peak areas represent the concentration of both forms. The
peak position is an average and changes with pH according to the relative
ratio of the two forms. In 2-(2-aminoethylamino)-ethanol both N-groups
can be protonated, whereas the first protonation (−6.1496 kcal/mol) is
favorable than both N-groups protonation (51.8014 kcal/mol) in
terms of the minimum energy calculations (see Fig. 1). Both con-
formers (primary protonation IL1a and secondary protonation
IL1b) that we suggest to be populated have similar stability in
terms of total energy calculations (−6.1496 kcal/mol for IL1a and
−9.7565 kcal/mol for IL1b). The carbon and proton NMR signals
are in concordance with the above assumption and calculations
using ChemBioOffice 2008 Ultra version 11 program. We simulated
3.2. Thermal properties
To examine the thermal stability of ILs, TG analysis has been
performed under conditions given in Section 2.1. The TG curves related
to the thermal decomposition of IL1a–b and IL2 were illustrated in
Fig. 4. The TG curves clearly indicate that thermal decompositions of
ILs are not similar. Decomposition temperature (Td) was estimated by
the cross point of two extrapolated lines according to the conventional
method. High thermal stability for IL1a–b (Td=158 °C) has been ob-
served as compared to the thermal stability of IL2 which was found to
be 138 °C.
On other hand, the melting points and the solidification tempera-
tures of IL1a–b and IL2 were determined using DSC technique. The
DSC curves obtained under inert nitrogen atmosphere in Seiko
DSC7020 equipment at
a
heating rate of 10 °C min−1 in the
Fig. 1. Primary protonation (a) and secondary protonation (b) in IL1.
Fig. 2. Primary and secondary protonation of 2-(2-aminoethylamino)ethanol in IL1a–b.

372
A. Karadağ, A. Destegül / Journal of Molecular Liquids 177 (2013) 369–375
Table 2
where tanδ is loss tangent in which δ is phase angle formed by the
loss in dielectric material. Also, ac conductivity of a material is given
1H, 13C and DEPT NMR spectra of IL1a–b and IL2.
by the following equation [23–25].
No
IL1a
IL1b
IL2
1H
DEPT
13C
60.87
51.56
51.00
41.53
169.50
1H
DEPT
13C
60.11
52.56
39.15
46.23
164.80
1H
DEPT
13C
59.22
50.55
46.42
37.93
174.61
23.43
ꢀ ꢁ
d
A
σac
¼
ωC tanδ ¼ ε″ωε0
ð4Þ
2
3
5
6
8
9
3.65
2.72
2.80
2.84
8.5
CH2
CH2
CH2
CH2
CH
3.71
3.39
3.09
3.42
8.16
CH2
CH2
CH2
CH2
CH
3.50
2.69
2.77
2.63
CH2
CH2
CH2
CH2
C
The permittivity is related to relative dimensionless complex per-
mittivity (called rather the dielectric constant) by expression ε=ε0εr.
For free space εr equals to 1, so the other dielectric materials have
much greater values of dielectric constant than 1.
1.58
CH3
A dielectric material must contain a charge that can be displaced
by applying an electric field and store a part of the applied field. The
displacement of the charge by applying the electric field is called as
“polarization”. Complex dielectric permittivity of the material de-
pends on the polarizability of the molecules. As the polarizability of
the molecules rises, the permittivity of the material increases. Polar-
ization within the ionic liquid occurs as a response to an electric field.
The relative permittivity is directly related to the electronic polariza-
tion, atomic polarization, orientation polarization and interfacial po-
larization. In a dielectric material, the total polarization is the sum of
all the polarizations resulting from each one of them. For ionic liq-
uids studied here, in this frequency range (102–107 Hz) orientation
polarization plays a more dominant role. The orientation polariza-
tion only exists in polar materials, and that their molecules have a
permanent dipole moment.
As seen in Fig. 6, all samples have showed the similar dielectric be-
haviors according to frequency. In a low frequency range, the IL2/
MnCl2 sample has the lowest dielectric constant value and IL2/CaCl2
the highest value. In the high frequency range, all samples indicate
a strong decrease in reel dielectric constant with increasing frequen-
cy and also remain almost constant at the higher frequencies. The de-
crease in dielectric constant is due to dielectric dispersion as a result
of the lag of molecules behind the alternation of the electric field at
higher frequency [26]. That is, in this rapid decrease region of reel
relative permittivity, the polarization cannot follow an alternating
electric field.
temperature range of (−100)–30 °C are shown in Fig. 5. IL1a–b and IL2
were cooled from 30 °C to −100 °C and heated up again from this tem-
perature to the initial temperature. The starting temperatures of solidi-
fication for IL1a–b and IL2 are −67.7 °C and −61.8 °C, respectively as
the ends of solidification are observed at −76.1 °C and −72.0 °C, re-
spectively. As shown in Fig. 5, while melting peaks are clearly seen,
second-order transitions are observed instead of peaks which appear
as a clear for solidifications. The shapes of the solidification curves of
IL1a–b and IL2 are shoulder like, which can be attributed to irregular so-
lidification of the ILs at different states of crystallinity. The irregularity is
a result of consistence of different crystalline structures simultaneously.
The melting points (and the melting enthalpies) of IL1a–b and IL2 are
also observed at −66.9 °C (6.52 J/g) and −56.0 °C (3.43 J/g), respec-
tively. The low-melting enthalpies of IL1a–b and IL2 may be evidence
of their irregular solidification.
3.3. Dielectric properties
Dielectric properties involve the measurement of the response of
dipoles on the material to a sinusoidal varying voltage. The polariza-
tion induced by alternating electric field in the materials is dependent
on frequency, temperature and chemical composition, so the permit-
tivity becomes complex. The complex permittivity of the materials is
described as follows [22],
Fig. 7 shows dependence of the imaginer relative permittivity (a
measure of dielectric loss) on frequency for the IL2 sample, with dif-
ferent dopants, at room temperature. From this graph, a presence of
relaxation type polarization can be seen. Variation of imaginary per-
meability in all the samples is similar. For each sample, there is a fre-
quency of relaxation. For IL2, it is 29 kHz, IL2/CaCl2 26 kHz, IL2/MnCl2
42 kHz and IL2/KCl 29.8 kHz. Dopants have shifted the relaxation fre-
quency of IL2. The shifts of relaxation frequencies in Fig. 7 may imply
that the molecules of the ionic liquid led to complexation or a type of
interaction between metal atoms and dopants.
Below 1 kHz, dielectric loss is very small. Because at low frequencies,
the rotation of molecules is quite slow and energy consumption is less.
So the polarization easily follows the electric field. After this frequency
dielectric loss (εr″) indicates a rapid rise until the relaxation frequency.
In this range εr′ also rapidly decreases. At relaxation frequency a maxi-
mum occurs in the εr″. After this frequency, molecules cannot follow the
applied field, therefore, they continue to rotate slowly and the dielectric
loss begins to decrease again. After 1 MHz, dielectric loss becomes quite
small, so εr′ remains almost constant.
εꢀ ¼ ε′−jε″
ð1Þ
where ε′ is the reel and the imaginer parts of the permittivity. The
reel part is expressed as
d
ε0A
ε′ ¼ C
ð2Þ
where d is the spacing between ITO-coated internal surfaces of the
sample cells, A is the effective area ε0 is the permittivity of free
space at 8.85×10−12 F/m and the imaginer part is expressed as,
ε′ ¼ ε′ tanδ
ð3Þ
In this study, some of the electrical properties of both ILs and their
various metal salt mixtures were investigated. For this purpose, the
ILs were mixed with metal salts at a rate of 1/10.
As shown in Fig. 8, at a low frequency region, AC conductivities of
all samples remain constant. Then, it indicates the rapid increase with
increasing frequency up to nearly 100 kHz. After this frequency AC
conductivity remains almost constant until 6.3 MHz for all samples
and thereafter begins to decrease again. At a frequency region in
which AC conductivity is constant the highest conductivity belongs
to the IL2 sample and the lowest IL2/KCl.
Fig. 3. Primary protonation of 2-(2-aminoethylamino)ethanol in IL2.

A. Karadağ, A. Destegül / Journal of Molecular Liquids 177 (2013) 369–375
373
Fig. 4. TG curves of IL1a–b and IL2.
Fig. 5. DSC curves of IL1a–b and IL2.
As for the IL1a–b samples, the similar dielectric behaviors were ob-
served. Fig. 9 shows dependence of reel relative dielectric constant on
frequency for IL1a–b in the frequency range of 100–107 Hz, with differ-
ent dopants and initiator material (Hydeten). From this graph, it is seen
that while the highest value of ε′ belongs to the IL1a–b and IL1a–b/
MnCl2 samples, the lowest value belongs to an initiator material, and
so the greater polarization for the IL1a–b and IL1a–b/MnCl2 samples.
The IL1a–b/KCL and IL1a–b/CaCl2 samples also have similar dielectric
trends.
Fig. 10 shows dependence of the imaginer relative permittivity (a
measure of dielectric loss) on frequency for the IL1a–b sample, with dif-
ferent dopants, at room temperature. From this graph, a presence of the
Fig. 6. Dependence of ε′ on frequency for IL2, with different dopants.
Fig. 7. Dependence of ε″ on frequency for IL2, with different dopants.

374
A. Karadağ, A. Destegül / Journal of Molecular Liquids 177 (2013) 369–375
Fig. 8. Variation of AC conductivity versus frequency for IL2 and different dopants.
Fig. 10. Dependence of ε″ on frequency for IL1a–b, with different dopants and initiator
material (Hydeten).
same type of polarization with that of IL2 has been observed. Variation
of imaginary permeability in all the samples is similar. The frequencies
of relaxation are the following: IL1a–b 588 Hz, IL1a–b/CaCl2 415 Hz,
IL1a–b/MnCl2 552 Hz, IL1a–b/KCl 442 Hz and Hydeten 347 Hz. Dop-
ants have shifted also the relaxation frequency of IL1a–b.
achieved. It is thought that the alkyl halides used in these reactions
were bonded to the IL1. Hence, the amine and ester formation reactions
of IL2 were not tested.
The variation of AC conductivity according to frequency for the IL1a–
b samples is very similar to those of the IL2 samples (Fig. 11). At a fre-
quency region in which AC conductivity is constant the highest conduc-
tivity belongs to the IL1a–b sample and the lowest initiator material
(Hydeten). Thermo-analytical and AC conductivity data for IL1a–b and
IL2 were summarized in Table 3.
As a result, it is seen in Figs. 8 and 11 that the addition of various
metal salts in ILs is not increasing their AC conductivity, but only reduc-
ing partially. This change in conductivity may be an evidence of partial
solubility of metal salts in ILs. If the metal salts dissolve in ILs complete-
ly, the conductivity of ILs would increase proportional to its content.
This can be explained by that metal salts dissolve partially to increase
the conductivity and then phase separated to decrease conductivity of
the saturated system. In addition, complexation tendency of metal
ions of the metal salts in ILs is thought to increase conductivity of
metal salts in the order of MnCl2, CaCl2 and KCl. This tendency is be-
lieved to be partially effective on conductivity change.
Heck reactions are very difficult reactions conducted at high temper-
atures using organic solvents like THF, dioxane, DMF, and DMSO. It is
well known that these organic solvents cause environmental problems
due to their high boiling temperatures, high vapor pressure, and inabil-
ity to dissolve in water. On the other hand, usage of DMF and DMSO
which are aprotic polar solvents causes difficulty of recovery of reaction
products from the intermediate and catalyst activity to slow down due
to the ability of these solvents to coordinate cations (too high giving
property). Therefore these solvents are not preferred generally. These
kinds of solvents are not preferred because of their high cost and
harm to environment for the issue of green chemistry. Besides using
them in these reactions does not bring advantages. Thus, usage of ILs
that are environmentally friendly becomes important not only as sol-
vent but also as catalyst.
The Heck reaction for the preparation of disubstituted olefins [27] is
a considerably useful and powerful method. Heck reactions conducted
with tertiary phosphine [28] or NHC [29] complexes generally require
temperatures between 100 and 130 °C and polar solvents. In this
work, both catalyst and solvent properties of IL1a–b and IL2 for the
Heck were studied under the certain reaction conditions. In the first
round, using the KOtBu base, the ILs were tested in the catalyst-free me-
dium, but the coupling reaction did not occur. In another study, using
3.4. Catalytic properties
To recover the product from the reaction medium completely in the
amine and ester formation reactions performed using IL1 was not
Fig. 9. Dependence of ε′ on frequency for IL1a–b, with different dopants and initiator
material (Hydeten).
Fig. 11. Variation of AC conductivity versus frequency for IL1a–b and different dopants.

A. Karadağ, A. Destegül / Journal of Molecular Liquids 177 (2013) 369–375
375
Table 3
Thermo-analytical and AC conductivity results for IL1a–b and IL2.
Ionic liquid
Td (thermal stability) °C
So (solidification onset) °C
Sf (solidification end) °C
−76.1
Mp (melting point) °C
−66.9
ΔH (melting enthalpy)
(J/g)
σ (AC conductivity)
(μS/cm)
IL1a–b
158
−67.7
6.52
66.7/100 kHz
65.0/100 kHz
51.9/100 kHz
46.5/100 kHz
58.8/1 MHz
54.5/1 MHz
52.1/1 MHz
49.5/1 MHz
IL1a–b/MnCl2
IL1a–b/CaCl2
IL1a–b/KCl
IL2
IL2/MnCl2
IL2/CaCl2
IL2/KCl
138
−61.8
−72.0
−56.0
3.43
Table 4
study were proven to be alternative solvents for Heck coupling reac-
tions in which organic solvents with high volatility are operated,
therefore they can be classified as green solvents.
Heck reactions using IL1a–b, IL2, and doped IL1–2.
NHC-Pd / ILs
Br
R
+
R
KOtBu, 80 oC, 1h
Acknowledgment
Entry
R
X
ILs
IL1a-b
Yield (%)
1
2
3
4
COCH3
COCH3
COCH3
COCH3
Br
Br
Br
Br
16
−
The authors are grateful to Professor İbrahim Demirtaş for NMR,
Professor Yetkin Gök for catalysis and Associate Professor Yusuf
Yerli for dielectric measurements in the study.
IL1a-b/MnCl2
IL1a-b/CoCl2
IL2
50
60
References
5
6
7
COCH3
COCH3
H
Br
Br
I
IL2/MnCl2
IL2/CoCl2
IL1a-b
75
27
95
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