Tris-imidazolium and benzimidazolium ionic liquids: A new class of biodegradable surfactants

Article abstract of DOI:10.1039/c4ra14027c

Based on imidazolium and benzimidazolium, two series of novel tris-cationic ionic liquid surfactants containing ester groups were synthesized simply from readily available starting materials in high yields. Biodegradability and surfactants properties of the tris-imidazolium and tris-benzimidazolium ionic liquids were investigated. Some compounds showed assembly behaviour in the pure form (i.e. absence of solvent) and in the presence of polar or nonpolar solvents. These surfactants are effectively reducing the surface tension of water in the range of 28-31 mN m^-1. Through using the 'Closed-Bottle Test' OECD 301D, the incorporation of alkyl or phenyl side chains with ester groups in the same molecule significantly improved the biodegradation compared to sodium n-dodecyl sulphate (SDS) as a reference. The aliphatic alkyl side chain, i.e., butyl, hexyl, octyl, decyl and dodecyl, in both imidazolium and benzimidazolium ionic liquids have marked increasing biodegradation and phase behaviour results compared to aromatic side-chains.

Full text of DOI:10.1039/c4ra14027c

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Factors that improved the biodegradation of surfactants have successfully used to prepare higher ordered
biodegradable tris-imidazolium and benzimidazolium ionic liquids.

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Trisꢀimidazolium and benzimidazolium ionic liquids: A new class of
biodegradable surfactants
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Nassir N. AlꢀMohammed*, Rusnah Syahila Duali Hussen, Yatimah Alias* and Zanariah Abdullah
6
Chemistry Department, Faculty of Science, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur,
Malaysia
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Abstract
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Based on imidazolium and benzimidazolium, series of novel trisꢀcationic ionic liquid surfactants containing ester
groups synthesized simply from readily available starting materials in high yield. Biodegradability and
surfactants properties of trisꢀimidazolium and trisꢀbenzimidazolium ionic liquids were investigated. Some
compounds showed assembly behaviour in pure form (i.e. absence of solvent) and in the presence of polar or
nonpolar solvents. These surfactants are effectively reducing the surface tension of water in a range of 28ꢀ31
mN/m. Through using ‘ClosedꢀBottle Test’ OECD 301D, the incorporation of alkyl or phenyl side chains with
ester groups in the same molecule significantly improved the biodegradation comparing to sodium nꢀdodecyl
sulphate (SDS) as a reference. The aliphatic alkyl side chain, i.e., butyl, hexyl, octyl, decyl and dodecyl, in both
imidazolium and benzimidazolium ionic liquids have marked increasing biodegradation and phase behaviour
results compared to aromatic sideꢀchains.
20
Introduction
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26
Ionic liquids (ILs) are organic salts melt below 100 °C and consist of bulky organic cation associated with either
organic or inorganic anion.1,2 Typically, most common organic cations are either imidazolium, pyridinium, or
pyrrolidinium, with alkyl chain substituents3,4 while anions such as halogen, [AlCl4]−, [PF6]−, [BF4]−, [CF3SO3]−,
[(CF3SO2)2N]− , or [nꢀC8H17OSO3]−.5 ILs have become increasingly attractive as ‘‘green’’ solvents (or
environmental friendly) for a wide range of applications due to their low vapour pressure with recycling and
catalytic ability.6ꢀ12
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32
In principle, the physicochemical properties of IL solvents can be tailored for a given application by varying the
cationic (or anionic) components. Thus, their properties including melting point, solubility, viscosity, thermal
stability and hydrophobicity can be adjusted to suit a variety of wide applications. Some ILs also have surfactant
behaviour; therefore, their assemblies can be tuneable by adjusting the solvent composition. Application of ILs
as a solvent coupled with their liquid crystalline behaviour could be an advantage in anisotropic ionꢀconductors,
templating and electrolytes in dyeꢀsensitizer solar cells.13,14
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41
Through thorough studies against a wide range of organisms, the popular used ILs are proven as toxic in
nature15,16 where the both cationic and anionic components have influence on the toxicity.17,18 Moreover, ILs that
consist of a substituted cation with long linear hydrocarbon side chains ≥ 8 carbon atoms presented varying
toxicity levels.19,20 The positive head group of the cation plays essential role in IL toxicity21 where the longer
side chains have further biological serious influence on living cells.22,23 At the same time, ILs demonstrated
various levels of toxicity magnitude comparing to conventional organic solvents: acetone, acetonitrile, methanol,
dichloromethane and methyl tꢀbutyl ether.24,25 First study related ILs toxic nature contributed by Jastorff and coꢀ
workers26 in 2002 when reported theoretical multidimensional analysis of two ILs. They proposed environmental
risk assessment of 1ꢀbutylꢀ3ꢀmethylimidazolium tetrafluoroborate and 1ꢀdecylꢀ3ꢀmethylimidazolium tetrafluoroꢀ
1

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borate ILs with acetone as an organic solvent reference. Five ecotoxicological indicators were considered in this
multidimensional analysis including: release, spatiotemporal range, bioaccumulation, biological activity and
uncertainty. Further, the first comprehensive biological study by Ranke et al.25 included effects of different nꢀ
alkyl chains for methylꢀ and ethylꢀimidazolium ILs incorporated with variety of anions. The study revealed ILs
toxicity increasing due to elongation in both alkyl chains length of imidazolium ring. Obviously, ILs may have
greater potential to bioaccumulate (persist in the environment) and vice versa when not passing biodegradation
tests. Further studies of biodegradation, mineralization and bioaccumulation are necessary to estimate the toxic
hazards of ILs or their persisting in the environment. Although different studies on ILs, including toxicity,
ecotoxicity and biodegradation have been reported in the literature,15,27ꢀ31 biodegradation data are still seldom.
Wells and Coombe24 screened the biodegradation of ammonium, imidazolium, phosphonium and pyridinium ILs
using Biochemical Oxygen Demand measurements in five days (BOD5). Most of the investigated alkyl side
chain ILs showed biodegradation resistant.
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The first biodegradable compounds presented by Boethling32,33 when highlighted the importance of
biodegradable chemicals through biodegradable surfactants design for linear alkylbenzenesulfonates and dialkyl
quaternaries. Furthermore, Boethling presented readily biodegradable compounds when introduced the long
linear hydrocarbon side chain into an ester group. Generally, the biodegradable surfactants32ꢀ34 have been
developed based on: (i) the existence of potential sites of esters as an enzymatic hydrolysis, (ii) the introduction
of oxygen in the form of hydroxyl, aldehyde or carboxylic acid groups, in addition to (iii) the existence of
unsubstituted long linear alkyl chains or phenyl rings, which represent potential sites for attack by oxygenases.
Hydrolysable bond (esters or amides) as functional groups introduced into the ILs cation side chain were
required to synthesize early biodegradable ILs. The same principles were followed by Gathergood and coꢀ
workers35,36 when evaluated the biodegradation for series of dialkylimidazolium ILs with ester or amide
containing side chains using the closed bottle tests (OECD 301 B and D). Compounds with biodegradation levels
of 60 % or higher are considered to be ‘‘readily biodegradable’’.37,38
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The design of potential biodegradable ILs affected by structure of the components that include most ILs: the
cation core, cation side chain(s), and the anion. Imidazole such as the common amino acid; histidine is known to
be degraded by microorganisms.39 Further, imidazolium core has close structural relationship with surfactant like
quaternary ammonium compounds38; therefore, imidazolium moieties were selected as the cation core. Thus, the
factors that improved the biodegradation of surfactants could be applicable to design the ILs cation able to selfꢀ
assemble with or without the presence of a solvent. In the surfactant’s point of view, rodꢀlike molecules such as
singleꢀchain imidazole derivatives are generating nematic (N) and bilayer smectic A (SmA) phases40,41 while
tripleꢀtails compounds have the tendency to form wedgeꢀshape molecules. They have the affinity to form higher
ordered molecular arrangements such as columnar (Col) or cubic (cub) phases.42,43 Consequently, higher ordered
phases are good candidates for application as anisotropic ion conductors.13
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Although many researchers35,44ꢀ48 have studied degradable ILs, none have approached triꢀcationic ILs in the
literature up to authors’ knowledge. The current study concentrates on synthesis novel trisꢀimidazolium and trisꢀ
benzimidazolium degradable ILs surfactants, containing incorporated alkyl or phenyl side chains with triꢀester
groups in same molecule. Towards degradable IL surfactants with higher ordered molecular arrangements
phases, a unique evaluation of biodegradation, phase behaviour and their interaction with water of halogen ILs
are investigated. Broad practical applications of industrial and medical applications are highly expected. The
effects of anions on phase behaviour and biodegradation are beyond the scope of this study.
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Results and discussion
Synthesis
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ILs syntheses described in current study are based on a simple approach which was modified to prepare trisꢀ
imidazolium and trisꢀbenzimidazolium ILs from readily available starting materials in high yield. This process
involved alkylation of alkylꢀimidazole and alkylꢀbenzimidazole with appropriate triꢀester halide that synthesized
by simple esterification of 1,1,1ꢀTris (hydroxymethyl)ethane in net chloroacetyl chloride. Furthermore, the
halides in the alpha position to carbonyl compound reflect excellent starting materials for high purity and
excellent yield of ILs. The synthesis of different length chain of alkyl imidazoles and benzimidazoles was
beneficial to obtain plenty of ILs derivatives. Thus, treatment of imidazole or benzimidazole with alkyl halides
under basic conditions affords alkyl imidazoles (and benzimidazole) in optimum yield. Alkylation of the
obtained alkyl imidazoles and benzimidazoles with active triꢀester halide in acetonitrile at 45ꢀ55
quantitative yield of certain ILs as shown in (Scheme 1).
°C produced the
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Scheme 1. Synthesis of trisꢀimidazolium and trisꢀbenzimidazolium ILs
98
99
All the chloride ILs prepared in current work are semiꢀsolid to syrup at room temperature which have been set as
−
reference point to determine their classification as ILs.1 Metathesis of halogen anion to NTf2 produced clear
100
liquids at room temperature and clean samples were isolated after a simple workup. The process included mixing
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an aqueous solution of chloride salt with LiNTf2. The hydrophobic IL phase was then separated by simple
extraction with ethyl acetate to produce pure ILs after organic layer evaporation under reduced pressure. Table 1
summarized the synthetic details of the prepared ILs.
104
Table 1: Structural and synthetic details of trisꢀimidazolium and trisꢀbenzimidazolium ILs
IL Cations Alkyl chains Counter ions
Statusc
Semiꢀsolid 595.90
M.wt. Yield (%)
Ima
Ima
CH3
nꢀC4H9
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
NTf2
NTf2
NTf2
NTf2
NTf2
NTf2
NTf2
NTf2
NTf2
NTf2
97
98
98
97
99
99
91
97
99
98
99
99
96
81
84
85
94
91
84
90
90
96
96
8a
8b
8c
8d
8e
8f
8g
9b
9c
9d
9e
9f
9g
Syrup
Syrup
Syrup
Syrup
Syrup
722.14
806.30
890.46
974.62
1058.78
824.19
872.32
956.48
1040.64
1124.80
1208.96
Ima
nꢀC6H13
nꢀC8H17
nꢀC10H21
nꢀC12H25
ꢀCH2ꢀPh
nꢀC4H9
nꢀC6H13
nꢀC8H17
nꢀC10H21
nꢀC12H25
ꢀCH2ꢀPh
ꢀCH3
Ima
Ima
Ima
Ima
Semiꢀsolid
BImb
BImb
BImb
BImb
BImb
BImb
Ima
Syrup
Syrup
Syrup
Syrup
Syrup
Semiꢀsolid 974.37
1329.98
10a
10b
10c
10e
10g
11b
11d
11e
11f
11g
liquid
Ima
nꢀC4H9
1456.22
liquid
Ima
nꢀC6H13
nꢀC10H21
ꢀCH2ꢀPh
nꢀC4H9
nꢀC8H17
nꢀC10H21
nꢀC12H25
ꢀCH2ꢀPh
1540.38
liquid
Ima
1708.70
liquid
Ima
1558.27
liquid
BImb
BImb
BImb
BImb
BImb
1606.39
liquid
1774.71
liquid
1858.88
liquid
1943.04
liquid
1708.45
liquid
a Imidazolium
b Benzimidazolium
c
at room temperature
105
106
Liquid crystalline behaviour
107
108
109
110
111
112
113
114
115
116
117
118
Optical polarizing microscope equipped with heating stage was used to investigate liquid crystalline properties
of compounds 8bꢀf and 9bꢀf thermotropically and lyotropically as highlighted in the experimental section. In
absence of solvents, compounds 8b, 8c, 8d and 9b, 9c, 9d appeared to be viscous fluids at room temperature
with no birefringence, while compounds with ≥ C10 carbons chain length showed birefringent at room
temperature. Trisꢀimidazolium series showed birefringent property with clearing points of 116 °C and 172 °C for
compounds 8e and 8f, respectively. Both compounds expected to form smectic A phases (oily streaks) based on
the textures shown in Fig. 1. While trisꢀbenzimidazolium compound series showed relatively lower clearing
point i.e. 37 °C for 9e and 50 °C for 9f. The benzanelation of the imidazole reduced the clearing point
significantly and increased the molecules area of nonpolar domain; thus, the chains packed in a wedgeꢀshaped
molecule which favours the formation of columnar phase (Fig. 2). Precisely, ascending and descending trends
was observed in clearing points of trisꢀimidazolium and benzimidazolium ILs, respectively, as a function of
chains length increasing illustrated in Table 2. Clearing point13,49 is the transition temperature between liquid
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crystalline phase (mesophase) and isotropic liquid whereas the liquid crystal phase is completely converted to an
isotropic liquid above the clearing point.
40μm
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122
Fig. 1. The oily streaks texture observed under polarized microscope for compound 8f at 25°C (50×).
40μm
123
124
Fig. 2. The columnar texture observed under polarized microscope for compound 9e at 25°C (50×).
125
126
127
128
129
130
131
132
133
134
Lyotropic investigation was performed using contact penetration scans method where the samples are
sandwiched between two slides with or without adding solvent at the slide edge. The solvent diffused through
the sample by capillary force then the liquid crystalline phase was formed when the solvent penetrated the
sample with different concentration gradient. Water as polar solvent and 1ꢀundecanol as nonpolar were used to
investigate the polymorphism in different system. In water penetration study compounds 8b, 8c, 9b, 9c, and 9d
are very soluble; therefore, formation of micellar, L1, solution was expected, while for compounds 8d, 8e and 8f,
a normal hexagonal phase, H1, was observed with slowly dissolving into L1 phase. In contrast, trisꢀ
benzimidazolium compounds series was less soluble and exhibited a cubic phase. The penetration profile of
compound 8f at room temperature is shown in Fig. 3 and the image for 9e in contact with water is shown in Fig.
4.
5

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40μm
135
136
Fig.3. Water penetration scans observed under polarized microscope for compound 8f at 25 °C (50×).
40μm
137
138
Fig.4. Water penetration scans observed under polarized microscope for compound 9e at 25 °C (20×).
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The behaviour of trisꢀimidazolium series in contact with nonpolar solvent showed that longer chain compound
i.e. 8f is very soluble to form an inverted micellar solution, L2. Further, additional liquid crystalline phases were
observed for 8b, 8c, 8d and 8e besides the L2. E.g. inverted hexagonal (H2), maltese crosses with H2 and finally
lamellar phases with H2 for 8b, 8c and 8d ILs, respectively, as depicted in Fig. 5.
a
b
c
H2 L2
L2
H2 Lα
H2
L2
Lα
27μm
27μm
27μm
143
144
Fig.5. 1ꢀUndecanol penetration scans for compounds (a) 8b (b) 8c (c) 8d at 25 °C (50×).
145
146
147
Compounds 9b and 9c did not show any liquid crystal phase in contact with 1ꢀundecanol, while compound 9d
exhibited inverted hexagonal and inverted cubic phases. Generally, longer chains length of trisꢀbenzimidazolium
compounds such as 9e and 9f displayed H2 and lamellar phases as presented in Fig. 6.
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a
b
c
27μm
27μm
27μm
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149
150
Fig.6. 1ꢀUndecanol penetration scans at 25 °C for compound 9e (a) overall scan penetration study taken at (10×)
magnification, (b) zoom for the lamellar phase (50×), and (c) the outer penetration displays H2 (50×).
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For this type of mesogen in both trisꢀimidazolium and benzimidazolium ILs, compounds starting with 10 carbon
alkyl chains showed a birefringent behaviour while shorter than 10 are most likely not flexible enough to align
unisotropically. In present liquid crystal phase, the molecules are still ordered in some direction with flows like a
liquid. According to literature, the same trend was noticed for 2ꢀtridecylpyridine chloride50 which melts at 52 °C
and clears at 109 °C. Moreover, materials based on IL can selfꢀassemble into a liquid crystal phase by solvent
addition; for example, triethylammoniumdodecyloxycyanobiphenyl bromide51 showed lamellar phase in contact
with water. Thus, the phase behaviour of ILs can be produced in pure state (spontaneously) and during their
interaction with polar and nonpolar solvents.
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Prediction and cartoon molecular alignment of IL material in the liquid crystalline phase is illustrated in Fig. 7
where the microꢀphase separation within the material is the driving force for its assembly. At the molecular
level, all alkyl chains are aligned in parallel as depicted in Fig. 7 (a) for compound 8e, while, at lower
concentration of solvent, the material preferably arranged in a smectic A or lamellar phase as illustrated in Fig. 7
(b). Further, in contacting with solvent, the molecules tend to reassemble depending on the nature of solvents.
Where in water, the chains arranged near each other with the polar part domain contacted to water as
demonstrated in Fig. 7 (c). The reverse arrangement occurred in contact with 1ꢀundecanol, where several discs
assembled together to form hexagonal phase as shown in Fig. 7 (d). Phase behaviour summarization results of
synthesized trisꢀimidazolium and bezimidazolium ILs are illustrated in Table 2.
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171
172
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Cl
O
N
N
O
O
O
Cl
N
N
O
(a)
Cl
N
N
O
175
176
177
178
179
Solvent
180
181
(d)
(c)
(b)
182
183
Fig. 7. Assembly illustration of (a) single molecule, (b) molecules arrangement in lamellar phase, (c) molecules
arrangement in normal hexagonal, H1 and (d) molecules arrangement in inverted hexagonal, H2
.
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Table 2: Phase behaviours of the synthesized trisꢀimidazolium and bezimidazolium ILs as a function of alkyl
chain length.
IL
Number of carbon
atoms in side chains
Clearing point
Phase behaviour
In waterc
Soluble
Soluble
I1, H1, V1
H1
In pureb
In 1ꢀundecanold
(°C)
NDa
NDa
NDa
116
172
107
103
90
4
6
8
10
12
4
6
8
10
12
Nonꢀbirefringent
Nonꢀbirefringent
Nonꢀbirefringent
Smectic A
H2
H2, Lα
H2
H2
H2
I2
I2
H2
H2
8b
8c
8d
8e
8f
9b
9c
9d
9e
9f
Smectic A
H1
Nonꢀbirefringent
Nonꢀbirefringent
Nonꢀbirefringent
Columnar
Soluble
Soluble
Soluble
I1
37
50
Columnar
H1
H2
a not detected
b is absence of solvent
c is contact with water
d is contact with 1ꢀundecanol
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Airꢀwater interface behaviour
Results of surface properties; critical micelle concentration cmc, and surface tension
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189
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191
γcmc beside Krafft
temperature, TK, are presented in Table 3. The values of TK for all ILs solutions are below 10 °C. The surface
tension measurements were recorded at 25 °C. The synthesized IL materials showed very low Krafft points
indicating their solubility below room temperature and IL cmc results can be measured at room temperature. As
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expected, cmc value of ILs (Table 3) decreased with increasing chain length, where, compounds with 4 carbons
at chain length are very soluble in water and the cmc values are expected to be higher than 150 mM based on a
preliminary investigation. Essentially, the compounds showed common trend for single chain nonꢀionic
surfactant such as alkyl maltosides.52 It is a decreasing by factor 10 upon addition of two methylene groups
except compounds with 10 and 12 carbon atoms in side chains for both tris imidazolium and benzimidazolium
ILs. The deviation from the trend may be attributed to multiple charges at high dilution of the IL, which
destabilize the micellar assembly. Thus, the synthesized ILs materials lowered the water surface tension to 28ꢀ31
mN/m. Moreover, the hydrophobicity of ILs materials had very minor influence on the molecules packing at
air/water interface. However, this only applied to the trisꢀimidazolium series. For the molecular shape a nonꢀ
parallel alignment of the alkyl chains is assumed, figuring the shape of a tripod.
202
Table 3: CMC, surface properties and Krafft temperature of ILs/water systems at 25 °C
IL
Carbon atoms
in sideꢀchains
Cmc
(mM)
TK
(°C)
γ
cmc
(mN/m)
4
8b
—
—
—
6
8
10
62.0
6.5
1.3
0.89
—
29
28
28
29
—
<10
<10
<10
<10
—
8c
8d
8e
8f
12
Benzyl
8g
4
9b
—
—
—
6
8
10
40.8
3.8
0.9
0.3
—
29
31
30
31
—
<10
<10
<10
<10
—
9c
9d
9e
9f
12
Benzyl
9g
203
204
Biodegradation results
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208
209
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211
‘Closed bottle’ OECD 301D test was used to evaluate the biodegradability of synthesized ILs as highlighted in
the experimental section. ILs with only imidazolium cations revealed higher degradation than those based on
benzimidazolium moieties as shown in Fig. 8 and 9. Further, the biodegradation was improved to highest percent
of 51% in 8f (dodecyl side chain) due to alkyl side chain length increment53 as illustrated in Fig. 8. The presence
of fused aromatic rings increased the stability of the ILs towards microbial degradation, therefore, changing the
cationic part to benzimidazolium compound 9f (dodecyl side chain) has reduced the IL degradation to 45% as
revealed in Fig 9.
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Moreover, the triꢀester linkages improved the biodegradation progression of the synthesized ILs; and upon
concordance, it was agreed that microbial enzymatic hydrolysis of the ester bonds could be the possible initiation
stage in degradation enhancement. As a result, separation of imidazoliumꢀalkyl chain fragment and
corresponding primary alcohol that would consider as readily metabolized via fatty acid βꢀoxidation was
achieved.15,36,54 The ILs biodegradation was promoted due to reasonable solubility for both of the produced
fragments in water. Similar trend in degradation percentage have previously reported in literature36 for ILs with
monoꢀimidazolium cation containing ester groups.
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SDS
100
90
80
70
60
50
40
30
20
10
0
8f (Dodecyl)
8e (Decyl)
8d (Octyl)
8c (Hexyl)
8b (Butyl)
8g (Benzyl)
0
2
4
6
8
10
12
14
16
Time (day)
221
222
Fig 8. Biodegradation curves of trisꢀimidazolium ILs series using closedꢀbottle test.
SDS
100
9f (Dodecyl)
9e (Decyl)
90
9d (Octyl)
9c (Hexyl)
80
9b (Butyl)
9g (Benzyl)
70
60
50
40
30
20
10
0
0
2
4
6
8
10
12
14
16
Time (day)
223
224
Fig 9. Biodegradation curves of trisꢀbenzimidazolium ILs series using closedꢀbottle test.
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226
227
228
For the purpose of starting and end test identification based on standard SDS samples results38,55 and current ILs
biodegradation curves, 16 days test duration was considered due to attain a plateau from the last three
measurements of these curves as shown in Fig. 8 and 9. Moreover, obvious difference in biodegradation values
was notified in 10 days comparing to 16 days of the test duration as shown in Fig. 10 and 11.
229
230
231
232
233
234
235
Furthermore, the presence of aliphatic alkyl side chain altered the hydrophobicity of monoꢀcationic ILs and
subsequently enhanced their biodegradation.53 In comparison to monoꢀcationic ILs,36,56,57 current trisꢀcationic ILs
showed a higher degradation percentage within shorter test duration in the presence of long linear alkyl side
chains. Moreover, changing the side chains from aliphatic groups (butylꢀ dodecyl) to aromatic chains (benzyl)
demonstrated a significant decreasing in degradation; 20 % and 16% in both 8g and 9g, respectively, as shown in
Fig. 10 and Fig. 11. The summarized biodegradation results of synthesized trisꢀimidazolium and bezimidazolium
ILs are illustrated in Table 4.
236
237
Table 4: Biodegradation results of synthesized trisꢀimidazolium and bezimidazolium ILs as a function of alkyl
chains length.
Carbon
atoms in
sideꢀchains
Biodegradation (%)
10 day 16 day
22 27
IL
4
8b
8c
8d
8e
8f
6
8
10
12
25.5
39
39
36
47
45
43
51
Benzyl
14.5
16.5
20.5
27
31
36
20
22
27
35.5
40
8g
9b
9c
9d
9e
9f
4
6
8
10
12
45
Benzyl
13
16
9g
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71%
10 Days
16 Days
69%
70
60
50
40
30
20
10
0
51%
47%
45 %
43%
39%
36%
39%
27%
25.5%
22%
20%
14.5%
SDS
8b
8c
8d
8e
8f
8g
(Butyl) (Hexyl) (Octyl) (Decyl) (Dodecyl) (Benzyl)
IL (Alkyl Chain Length)
240
241
242
Fig 10. Biodegradation of trisꢀimidazolium ILs series as a function of aliphatic or aromatic side chains on 10 and
16 days.
71 %
69%
10 Days
70
16 Days
60
50
45%
40%
40
36%
35.5%
31%
30
20
10
0
27%
20.5%
27%
22%
16.5%
16%
13 %
SDS
9b
9c
9d
9e
9f
9g
(Butyl) (Hexyl) (Octyl) (Decyl) (Dodecyl) (Benzyl)
ILs (Alkyl Chain Length)
243
244
245
Fig 11. Biodegradation of trisꢀbenzimidazolium ILs series as a function of aliphatic or aromatic side chains on
10 and 16 days.
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250
Generally, the tested ILs displayed significant levels of biodegradation, where ILs (8d, 8e, 8f and 9f) showed
distinctive biodegradability values of 47%, 45%, 51%, and 45%, respectively, after 16 days period from test
evaluation. The results indicated that these ILs are on the border of 60% pass level of readily
biodegradation.35,37,53
251
Conclusions
252
253
254
255
256
257
258
259
260
Trisꢀimidazolium and trisꢀbenzimidazolium ILs contain incorporation of alkyl or phenyl side chains with triꢀ
ester groups was generally found semiꢀsolid to syrup at room temperature. Metathesis of chloride anion to NTf2
was tuned it to liquids in excellent yield and purity. In absence of solvent, only compounds with ≥ 10 carbon
atoms at their hydrocarbon chains shows assembly behaviour. Compounds containing 8 carbon atoms are still
possible to assembly by addition of solvents either polar or nonpolar. These ILs surfactants are useful in wide
temperature range with Krafft temperature lower than 10 °C and effectively reduce the water surface tension to
29 mN/m. The imidazolium ILs resulted significant increasing in phase behaviour properties and biodegradation
compared to benzimidazolium ILs. Generally, ILs bearing imidazolium cations exhibit higher percentages of
degradation as compared to those with benzimidazolium.
261
262
263
264
265
266
The factors that improved the biodegradation of surfactants have successfully been used to develop the
biodegradation and selfꢀassemble behaviour of the synthesized triꢀcationic ILs. Further, comparing to monoꢀ
cationic ILs, these developed properties of synthesized trisꢀimidazolium and benzimidazolium ILs are highly
enhanced by increasing the ILs hydrophobicity. Precisely, ILs incorporating the long linear alkyl (i.e. octyl,
decyl, dodecyl) in the side chains presented on the border of the 60% pass level of readily biodegradation results
with capability to selfꢀassemble spontaneously or in the presence of a solvent.
267
268
269
270
271
The resistance to aerobic biodegradation is generally increased for compounds with halogens (chloride) as a
counter ion.38 Therefore, a more detailed study of counterꢀion effect on biodegradation is in progress towards
readily biodegradable for these trisꢀimidazolium and benzimidazolium ILs. Antibacterial evolution for current
ILs will be reported in future work. Furthermore, determination of the physical properties of the synthesized ILs
(e.g. solubility, thermal stability, cyclic voltammetry and fluorescence) will be reported in due course.
272
Experimental
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281
282
283
284
285
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1ꢀMethylimidazole (99%) and 1ꢀbutylimidazol (98%) were purchased from Aldrich and distilled before usage to
remove the detrimental impurities. 1ꢀhexylimidazole, 1ꢀoctylimidazole, 1ꢀdecylimidazole, 1ꢀdodecylimidazole,
1ꢀbenzylimidazole, 1ꢀbutylbenzimidazole, 1ꢀhexylbenzimidazole, 1ꢀoctylbenzimidazole, 1ꢀdecylbenzimidazole,
1ꢀdodecylbenzimidazole, and 1ꢀbenzylbenzimidazole were prepared as described below. 1ꢀbromohexane, 1ꢀ
bromooctane, 1ꢀbromodecane, 1ꢀbromododecane and benzyl bromide were obtained from commercial sources
and used without further purification. All ILs were kept in fridge (5 °C) and freezer (‒18 °C) for further
evaluation of their properties. General grade solvents and reagents were purchased from commercial suppliers
and used without further purification. The IR spectra were obtained with a Perkin Elmer 400 Fourier Transform
1
Infrared (FTIR) spectrometer. Both of H and 13CꢀNMR spectra were recorded on Jeol Lambda and ECAꢀ
DELTA as well as Bruker spectrometers at 400 MHz while 19FꢀNMR was recorded using Bruker spectrometers
400 MHz. Highꢀresolution mass spectra were recorded on Agilent Technologies 6530 Accurate QꢀTOF LC–MS
system, applying DMSO /MeOH eluents for ILs sample compounds while Agilent 5975 system for EI/MS
(NUS, Singapore) for the rest compounds. Thin layer chromatography was carried out on preꢀcoated silica gel
plates (0.25 mm, 20 × 20 cm, 60F254, E. Merck).
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Procedure for Synthesis of compound 3
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290
291
292
293
294
This compound was prepared according to modification applied to a procedure described in literature.58
1,1,1ꢀTris(hydroxymethyl)ethane 1 (10 g, 83.3 mmol) was dissolved and refluxed with minimum amount of
chloroacetyl chloride 2 until all HCl gas was liberated (pursue by wet litmus paper). The reaction mixture was
evaporated in vacuo until the excess of acid chloride was removed. The crude product was purified by coꢀ
evaporation with toluene (4ꢀ5 times) to produce paleꢀyellow viscous syrup solidified after few days. Reꢀ
crystallization from dry acetonitrile gave compound 3 as colourless crystals.
295
General Procedure for Synthesis of 6cꢀg and 7bꢀg
296
297
298
299
300
301
302
These compounds were prepared according to modification applied to a procedure described in literature.59
Potassium hydroxide (8.24 g, 147 mmol) was added to a solution of imidazole (5g) or benzimidazole (8.67g),
(73.4 mmol) in DMSO (30 mL) and the mixture was stirred for 30 min at room temperature. The corresponding
alkyl halide (61.2 mmol) was added portionꢀwise under vigorous stirring in a water bath and the stirring was
continued for overnight. The mixture was quenched with water (200 mL) and extracted with diethyl ether (3 ×
25 mL). The combined extracts were washed with water, dried over anhydrous magnesium sulphate and the
solvent was evaporated off under reduced pressure.
303
304
Trisꢀ((Nꢀmethylꢀimidazoliumylꢀacetayloxy)methyl)ethane chloride (8a)
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
A solution of 1ꢀmethylimidazole (1.34 g, 1.3 mL, 16.3 mmol) in acetonitrile anhydrous (5mL) was added dropꢀ
wise to a stirred solution of trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3) (1.9g, 5.43 mmol) in
acetonitrile anhydrous (15 mL) at room temperature under a nitrogen atmosphere. The reaction mixture was
stirred vigorously for 3 hours and refluxed at 50ꢀ55 °C for 3ꢀ4 days. The acetonitrile top layer was decanted and
the IL washed with diethyl ether (3 × 10 mL), then residual solvent removed in vacuo. The product was dried at
(40 °C, 0.01 mmHg) for 48 h to provide a viscous hygroscopic semiꢀsolid in 97% yield (3.14 g). Molecular
Formula: C23H33Cl3N6O6; Mol. Wt.: 595.90; FTIR (cmꢀ1): 3072 (CꢀH)Ar, 2970, 2925, 2852 (CꢀH)Aliph, 1744
1
(C=O), 1631 (C=N), 1565, 1464 (C=C)Ar, 1214, 1185 (CꢀO); HꢀNMR (400 MHz, CD3OD) δ ppm: 9.13 (bt~s,
3H, CꢀHImidazole, major), 9.10 (bt~s, 3H, CꢀHImidazole, minor), 7.72 (t, J =1.95 Hz, 3H, CꢀHImidazole, major), 7.70 (t, J
=1.95 Hz, 3H, CꢀHImidazole, minor), 7.67 (t, J =1.95 Hz, 3H, CꢀHImidazole, major), 7.65 (t, J =1.95 Hz, 3H, Cꢀ
HImidazole, minor), 5.33 (s, 6H, OꢀCH2, major), 5.29 (s, 6H, OꢀCH2, minor), 4.18 (s, 6H, NꢀCH2), 3.99 (s, 9H, αꢀ
13
CH3, major), 3.94 (s, 9H, αꢀCH3, minor), 1.09 (s, 3H, CH3, major), 0.98 (s, 3H, CH3, minor); CꢀNMR (100
MHz, CD3OD) δ ppm: 167.81 (C=O, minor), 167.74 (C=O, major), 139.35 (CHImidazole, major), 137.88
(CHImidazole, minor), 125.14 (CHImidazole, major), 124.72 (CHImidazole, major), 124.45 (CHImidazole, minor), 123.36
(CHImidazole, minor), 68.68 (CH2ꢀO, minor), 67.98 (CH2ꢀO, major), 50.85 (CH2ꢀN), 39.90 (ꢀCꢀ), 36.80 (αꢀCH3,
major), 35.10 (αꢀCH3, minor), 17.11 (CH3, major), 16.99 (CH3, minor); HRMS: m/z, [M+3‒2H]−3Cl− calcd. for
C23H31N6O65+ : 487.2305, found: 487.2330.
322
Trisꢀ((Nꢀhexylꢀimidazoliumylꢀacetayloxy)methyl)ethane chloride (8c)
323
324
325
326
This compound was prepared analogously to 8a using trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3)
(1.9 g, 5.43 mmol) and 1ꢀhexylimidazole (6c) (2.48 g, 16.3 mmol) to provide a viscous hygroscopic syrup in
98% yield (4.29 g). Molecular Formula: C38H63Cl3N6O6; Mol. Wt.: 806.30; FTIR (cmꢀ1): 3058 (CꢀH)Ar, 2955,
2929, 2859 (CꢀH)Aliph, 1749 (C=O), 1641 (C=N), 1564, 1463 (C=C)Ar, 1192, 1165 (CꢀO);1HꢀNMR (400 MHz,
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328
329
330
331
332
333
334
335
336
DMSOꢀd6) δ ppm: 9.66 (bt~s, 3H, CꢀHImidazole, major), 9.60 (bt~s, 3H, CꢀHImidazole, minor), 9.53 (bt~s, 3H, Cꢀ
HImidazole, minor), 7.95 (t, J =1.71 Hz, 3H,CꢀHImidazole, major), 7.90 (t, J =1.71 Hz, 3H,CꢀHImidazole, major), 7.84 (t,
J =1.71 Hz, 3H, Hz, CꢀHImidazole, minor), 7.80 (t, J =1.71 Hz, 3H, CꢀHImidazole, minor), 5.50 (s, 6H, OꢀCH2, major),
5.43 (s, 6H, OꢀCH2, minor), 4.25 (t, J= 7.07 Hz, 6H,αꢀCH2, major), 4.16 (t, J= 7.07 Hz, 6H, αꢀCH2, minor), 4.06
(bs, 6H, NꢀCH2), 1.81ꢀ1.74 (m, 6H, βꢀCH2), 1.24 (bs, 18H, bulkꢀCH2), 0.94 (s, 3H, CH3), 0.84 (t, 9H, J =6.83
Hz, ωꢀCH3); 13CꢀNMR (100 MHz, DMSOꢀd6) δ ppm: 168.12 (C=O), 137.33 (CHImidazole, minor), 137.23
(CHImidazole, major), 123.94 (CHImidazole), 122.12 (CHImidazole, minor), 121.98 (CHImidazole, major), 63.98 (CH2ꢀO),
49.78 (CH2ꢀN, major), 49.68 (CH2ꢀN, minor), 49.00 (αꢀCH2, minor), 48.94 (αꢀCH2, major)), 40.68 (ꢀCꢀ), 30.52
(ωꢀ2), 29.34 (bulkꢀCH2), 25.09 (β), 21.91 (ωꢀ1), 16.62 (CH3, minor), 16.47 (CH3, major), 13.84 (ω); HRMS:
m/z, [M+3‒2H]−3Cl− calcd. for C38H61N6O65+ : 697.4653, found: 697.4648.
337
Trisꢀ((Nꢀdodecylꢀimidazoliumylꢀacetayloxy)methyl)ethane chloride (8f)
338
339
340
341
342
343
344
345
346
347
348
349
350
351
This compound was prepared analogously to 8a using trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3)
(1.9 g, 5.43 mmol) and 1ꢀdodecylimidazole (6f) (3.85 g, 16.3 mmol) to provide a viscous hygroscopic syrup in
99% yield (5.24 g). Molecular Formula: C56H99Cl3N6O6; Mol. Wt.: 1058.78; FTIR (cmꢀ1): 3058 (CꢀH)Ar, 2955,
2925, 2859 (CꢀH)Aliph, 1749 (C=O), 1677 (C=N), 1564, 1466 (C=C)Ar, 1199, 1164 (CꢀO); HꢀNMR (400 MHz,
CD3OD) δ ppm: 9.20 (bt~s, 3H, CꢀHImidazole, major), 9.14 (bt~s, 3H, CꢀHImidazole, minor), 9.08 (bt~s, 3H, Cꢀ
1
HImidazole, minor), 7.71 (dt, J =8.15, 1.81 Hz, 6H, CꢀHImidazole, major), 7.67 (dt, 6H, J =8.15, 1.81 Hz, CꢀHImidazole
,
minor), 5.31 (s, 6H, OꢀCH2, major), 5.28 (s, 6H, OꢀCH2, minor), 5.26 (s, 6H, OꢀCH2, minor), 4.27 (t, J= 7.25 Hz,
6H, αꢀCH2, major), 4.23 (t, J= 7.25 Hz, 6H, αꢀCH2, minor), 4.18 (s, 6H, NꢀCH2, major), 4.14 (s, 6H, NꢀCH2,
minor), 1.93ꢀ1.84 (m, 6H, βꢀCH2), 1.26 (bs, 54H, bulkꢀCH2), 1.07 (s, 3H, CH3, major), 1.05 (s, 3H, CH3, minor),
13
0.87 (t, 9H, J =6.80 Hz, ωꢀCH3); CꢀNMR (100 MHz, CD3OD) δ ppm: 167.87 (C=O, major), 167.78 (C=O,
minor), 138.82 (CHImidazole), 125.38 (CHImidazole), 123.56 (CHImidazole), 68.18 (CH2ꢀO, major), 67.87 (CH2ꢀO,
minor), 67.60 (CH2ꢀO, minor), 51.22 (CH2ꢀN), 50.98 (αꢀCH2, major), 50.69 (αꢀCH2, minor), 39.87 (ꢀCꢀ), 33.17
(ωꢀ2), 31.24, 30.85(2), 30.76, 30.66, 30.57, 30.22 (bulkꢀCH2), 27.36 (β), 23.83 (ωꢀ1), 17.24 (CH3, major), 17.18
(CH3, minor), 14.56 (ω); HRMS: m/z, [M+3‒2H]−3Cl− calcd. for C56H97N6O65+ : 949.7470, found: 949.7479.
352
Trisꢀ((Nꢀbenzylꢀimidazoliumylꢀacetayloxy)methyl)ethane chloride (8g)
353
354
355
356
357
358
359
360
361
362
363
364
This compound was prepared analogously to 8a using trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3)
(1.9 g, 5.43 mmol) and 1ꢀbenzylimidazole (6g) (2.58 g, 16.3 mmol) to provide a pale yellow hygroscopic semiꢀ
solid in 91% yield (4.12 g). Molecular Formula: C41H45Cl3N6O6; Mol. Wt.: 824.19; FTIR (cmꢀ1): 3063 (CꢀH)Ar,
2977 (CꢀH)Aliph, 1747 (C=O), 1661 (C=N), 1563, 1497 (C=C)Ar, 1197, 1158 (CꢀO); 1HꢀNMR (400 MHz, DMSOꢀ
d6) δ ppm: 9.69 (s, 3H, CꢀHImidazole, major), 9.57 (s, 3H, CꢀHImidazole, minor), 9.44 (s, 3H, CꢀHImidazole, minor), 7.92
(t, J =1.71, 6H, CꢀHImidazole, major), 7.87 (t, J =1.71, 6H, CꢀHImidazole, minor), 7.45ꢀ7.20 (m, 15H, CꢀHAr), 5.56 (s,
6H, ArꢀCH2), 5.47 (s, 6H, OꢀCH2, major), 5.42 (s, 6H, OꢀCH2, minor), 5.36 (s, 6H, OꢀCH2, minor), 4.03 (d~t,
13
6H, NꢀCH2), 0.89 (s, 3H, CH3); CꢀNMR (100 MHz, DMSOꢀd6) δ ppm: 167.19 (C=O, minor), 166.64 (C=O,
major), 137.54 (CHImidazole), 134.85 (ꢀCArꢀCH2ꢀ), 128.98 (2×CHA), 128.77 (CHAr) 128.39 (2×CHAr), 124.22
(CHImidazole), 122.22 (CHImidazole, minor) 122.15 (CHImidazole, major), 66.48 (CH2ꢀO, major), 66.34 (CH2ꢀO, minor)
51.88 (CH2ꢀN), 49.68 (ArꢀCH2ꢀ), 41.10 (ꢀCꢀ), 16.31 (CH3, major), 16.20 (CH3, minor); HRMS: m/z, [M+3‒
2H]−3Cl− calcd. for C41H43N6O65+ : 715.3244, found: 715.3274.
365
Trisꢀ((Nꢀbutylꢀbenzimidazoliumylꢀacetayloxy)methyl)ethane chloride (9b)
366
367
To a stirred solution of trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3) (1.9g, 5.43 mmol) in acetonitrile
anhydrous (15 mL), the solution of 1ꢀbutylꢀbenzimidazole (7b) (2.84 g, 16.3 mmol) in acetonitrile anhydrous (5
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369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
mL) was added dropꢀwise at room temperature and under nitrogen atmosphere. The reaction mixture was
refluxed at 45ꢀ50 °C for 2ꢀ3 days, then at room temperature for 5 hours. The acetonitrile top layer was decanted
and the IL washed with diethyl ether (3 × 10 mL), then residual solvent evaporated under reduced pressure. The
product was dried at (40 °C, 0.01 mmHg) for 72 h to provide a viscous hygroscopic syrup in 97% yield (4.65 g).
Molecular Formula: C44H57Cl3N6O6; Mol. Wt.: 872.32; FTIR (cmꢀ1): 3025 (CꢀH)Ar, 2950, 2935, 2862 (CꢀH)Aliph
,
1748(C=O), 1616(C=N), 1559, 1478, 1460 (C=C)Ar, 1197, 1160 (CꢀO); 1HꢀNMR (400 MHz, DMSOꢀd6) δ ppm:
10.30 (s, 3H, CꢀHBImidazole, major), 10.23 (s, 3H, CꢀHBImidazole, minor), 10.18 (s, 3H, CꢀHBImidazole, minor), 8.14ꢀ
8.07 (m, 6H, CHAr), 7.71ꢀ7.61 (m, 6H, CHAr), 5.81 (s, 6H, OꢀCH2, major), 5.76 (s, 6H, OꢀCH2, minor), 4.58 (t,
J=6.83, 6H, αꢀCH2, major), 4.50 (t, J=6.83, 6H, αꢀCH2, minor), 4.05 (s, 6H, NꢀCH2, minor), 4.00 (s, 6H, NꢀCH2,
major), 1.91ꢀ1.83 (m, 6H, βꢀCH2, major ), 1.79ꢀ1.72 (m, 6H, βꢀCH2, minor), 1.36ꢀ 1.27 (m, 6H, (ωꢀ1)), 0.89 (t,
13
9H, J =7.32 Hz, ωꢀCH3), 0.81 (s, 3H, CH3); CꢀNMR (100 MHz, DMSOꢀd6) δ ppm: 166.88 (C=O), 143.37
(CHBImidazole, major), 142.97 (CHBImidazole, minor), 131.43 (CAr), 129.71 (CAr), 124.80 (CHAr), 124.73 (CHAr),
115.03 (CHAr), 113.12 (CHAr), 66.22 (CH2ꢀO), 47.52 (CH2ꢀN), 45.91 (αꢀCH2, major), 45.09 (αꢀCH2, minor),
38.12 (ꢀCꢀ), 32.23 ((ωꢀ2), minor), 31.85 ((ωꢀ2), major), 17.98 ((ωꢀ1), minor), 17.32 ((ωꢀ1), major), 16.15 (CH3),
13.80 ((ω), minor), 13.69 ((ω), major); HRMS: m/z, [M+3‒2H]−3Cl− calcd. for C44H55N6O65+ : 763.4183, found:
763.4223.
384
Trisꢀ((Nꢀdecylꢀbenzimidazoliumylꢀacetayloxy)methyl)ethane chloride (9e)
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
This compound was prepared analogously to 9b using trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3)
(1.9 g, 5.43 mmol) and 1ꢀ decylꢀbenzimidazole (7e) (4.21 g, 16.3 mmol) to provide a viscous hygroscopic syrup
in 99% yield (6.00g). Molecular Formula: C62H93Cl3N6O6; Mol. Wt.: 1124.80; FTIR (cmꢀ1): 3134 (CꢀH)Ar, 2958,
1
2923, 2854 (CꢀH)Aliph, 1749 (C=O), 1619 (C=N), 1562 1485, 1463 (C=C)Ar, 1199 (CꢀO); HꢀNMR (400 MHz,
DMSOꢀd6) δ ppm: 10.36 (s, 3H, CꢀHBImidazole, major), 10.22 (s, 3H, CꢀHBImidazole, minor), 10.12 (s, 3H, Cꢀ
HBImidazole, minor), 8.14ꢀ8.09 (m, 6H, CHAr), 7.71ꢀ7.61 (m, 6H, CHAr, major), 7.30ꢀ7.20 (m, 6H, CHAr, minor),
5.84 (s, 6H, OꢀCH2, major), 5.78 (s, 6H, OꢀCH2, minor), 5.73 (s, 6H, OꢀCH2, minor), 4.56 (t, J=7.25, 6H, αꢀCH2,
major), 4.51 (t, J=7.25, 6H, αꢀCH2, minor), 4.04 (s, 6H, NꢀCH2, minor), 3.99 (s, 6H, NꢀCH2, major), 3.97 (s, 6H,
NꢀCH2, minor), 1.92ꢀ 1.85 (m, 6H, βꢀCH2), 1.20 (bs, 42H, bulkꢀCH2), 0.86 (s, 3H, CH3), 0.82 (t, 9H, J=6.80, ωꢀ
CH3); 13CꢀNMR (100 MHz, DMSOꢀd6) δ ppm: 167.17 (C=O, minor), 166.44 (C=O, major), 143.37 (CHBImidazole
,
major), 142.28 (CHBImidazole, minor), 131.51 (CAr), 130.63 (CAr), 126.77 (CHAr), 126.69 (CHAr), 114.09 (CHAr,
major), 113.99 (CHAr, minor), 113.77 (CHAr), 66.30 (CH2ꢀO, major), 66.17 (CH2ꢀO, minor), 47.53 (CH2ꢀN),
46.82 (αꢀCH2, major), 46.66 (αꢀCH2, minor), 38.17 (ꢀCꢀ), 31.29 ((ωꢀ2), major), 30.71 ((ωꢀ2), minor), 28.91,
28.87, 28.68, 28.57, 28.64 (bulkꢀCH2), 25.71 (β), 22.10 (ωꢀ1), 16.18 (CH3, major), 16.11 (CH3, minor), 13.95
(ω); HRMS: m/z, [M+3‒2H]−3Cl− calcd. for C62H91N6O65+ : 1015.7000, found: 1015.7055.
400
Trisꢀ((Nꢀdodecylꢀbenzimidazoliumylꢀacetayloxy)methyl)ethane chloride (9f)
401
402
403
404
405
406
407
408
409
410
This compound was prepared analogously to 9b using trisꢀ((2ꢀchloroꢀacetayloxy)methyl)ethane (compound 3)
(1.9 g, 5.43 mmol) and 1ꢀdodecylꢀbenzimidazole (7f) (4.67 g, 16.3 mmol) to provide a viscous hygroscopic
syrup in 99% yield (6.50g). Molecular Formula: C68H105Cl3N6O6; Mol. Wt.: 1208.96; FTIR (cmꢀ1): 3132 (CꢀH)Ar,
1
2955, 2925, 2855 (CꢀH)Aliph, 1749 (C=O), 1619 (C=N), 1562, 1486, 1455 (C=C)Ar, 1198 (CꢀO); HꢀNMR (400
MHz, CD3OD) δ ppm: 9.77 (s, 3H, CꢀHBImidazole, major), 9.73 (s, 3H, CꢀHBImidazole, minor), 9.67 (s, 3H, Cꢀ
HBImidazole, minor), 8.02ꢀ7.89 (m, 6H, CHAr), 7.73ꢀ7.57 (m, 6H, CHAr, major), 7.42ꢀ7.33 (m, 6H, CHAr, minor),
5.63 (s, 6H, OꢀCH2, major), 5.60 (s, 6H, OꢀCH2, minor), 5.58 (s, 6H, OꢀCH2, minor), 4.54 (t, J=7.25, 6H, αꢀCH2,
major), 4.34 (t, J=7.25, 6H, αꢀCH2, minor), 4.20 (s, 6H, NꢀCH2, minor ), 4.17 (s, 6H, NꢀCH2, major), 4.05 (s, 6H,
NꢀCH2), 2.04ꢀ 1.96 (m, 6H, βꢀCH2), 1.25 (bs, 54H, bulkꢀCH2), 1.00 (s, 3H, CH3), 0.86 (t, J=7.25, 9H, ωꢀCH3);
13CꢀNMR (100 MHz, CD3OD) δ ppm: 167.54 (C=O, minor), 166.26 (C=O, major), 142.72 (CHBImidazole, major),
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411
412
413
414
415
142.46 (CHBImidazole, minor), 131.90 (CAr), 131.09 (CAr), 127.19 (CHAr), 127.09 (CHAr), 113.47 (CHAr), 113.35
(CHAr), 66.59 (CH2ꢀO, minor), 66.48 (CH2ꢀO, major), 66.07 (CH2ꢀO, minor), 45.41 (CH2ꢀN), 40.33 (αꢀCH2),
38.75 (ꢀCꢀ), 31.75 (ωꢀ2), 29.44 (2), 29.35, 29.25, 29.15, 28.90, 28.87 (bulkꢀCH2), 26.34 ((β), minor), 26.18 ((β),
major), 22.42 (ωꢀ1), 15.72 (CH3), 13.17 (ω); HRMS: m/z, [M+3‒2H]−3Cl− calcd. for C68H103N6O6 : 1099.7939,
5+
found: 1099.7964.
416
417
Trisꢀ((Nꢀmethylꢀimidazoliumylꢀacetayloxy)methyl)ethane bis(trifluoromethylsulfonyl)amide
(10a)
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
A flask was charged with trisꢀ((Nꢀmethylꢀimidazoliumylꢀacetayloxy)methyl)ethane chloride 8a (0.6 g, 1.0 mmol)
and deionized water (10 mL). Lithium bisꢀ(trifluoromethanesulphonyl)imide LiNTf2 (1.0 g, 3.5 mmol) in
deionized water (3 mL) was added in one portion and the suspension was stirred vigorously for 7 h at room
temperature. The mixture was extracted with Ethyl acetate (3×5mL) after stirring for 1h each time. The
combined organic layers were evaporated on the rotary evaporator and under high vacuum for 8 h to remove the
solvent and produce a clear viscous hygroscopic liquid at room temperature in 81% yield (1.08 g). Molecular
Formula: C29H33F18N9O18S6; Mol. Wt.: 1329.98; FTIR (cmꢀ1): 3070 (CꢀH)Ar, 2970, 2932, 2857 (CꢀH)Aliph, 1750
(C=O), 1642 (C=N), 1555, 1468 (C=C)Ar, 1359, 1220 (CꢀF), 1362, 1150 (O=S=O), 1220, 1184(CꢀO); 1HꢀNMR
(400 MHz, CD3OD) δ ppm: 8.70 (s, 3H, CꢀHImidazole, minor), 8.68 (s, 3H, CꢀHImidazole, minor), 8.66 (s, 3H, Cꢀ
HImidazole, major), 7.39 (dt, 6H, J =10.79, 1.76, Hz, CꢀHImidazole), 4.98 (s, 6H, OꢀCH2, major), 4.97 (s, 6H, OꢀCH2,
minor), 4.94 (s, 6H, OꢀCH2, minor), 3.98 (s, 6H, NꢀCH2, major), 3.95 (s, 6H, NꢀCH2, minor), 3.93 (s, 6H, Nꢀ
CH2, minor), 3.75 (s, 9H, αꢀCH3), 0.87 (s, 3H, CH3); 13CꢀNMR (100 MHz, CD3OD) δ ppm: 167.90 (C=O,
minor), 167.75 (C=O, major), 139.32 (CHImidazole), 126.07, 122.89, 119.71, 116.52 (q, J=320, CF3), 125.22
(CHImidazole), 124.91 (CHImidazole), 68.76 (CH2ꢀO, minor), 68.00 (CH2ꢀO, major), 50.82 (CH2ꢀN), 40.19 (ꢀCꢀ),
͞
36.85 (αꢀCH3), 17.03 (CH3). 19F (336, MHz) δ ppm: ‒80.12; HRMS: m/z, [M+3‒2H]−3NTF2 calcd. for
C23H31N6O65+ : 487.2305, found: 487.2285; m/z, [NTF2] calcd. for C2F6NO4S2 : 279.9173, found: 279.9169.
͞
−
434
Trisꢀ((Nꢀbenzylꢀimidazoliumylꢀacetayloxy)methyl)ethane bis(trifluoromethylsulfonyl)amide (10g)
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
This compound was prepared analogously to 10a using trisꢀ((Nꢀbenzylꢀimidazoliumylꢀacetayloxy)methyl)ethaꢀ
ne chloride 8g (0.82 g, 1.0 mmole) and Lithium bisꢀ(trifluoromethanesulphonyl)imide LiNTf2 (1.0 g, 3.5 mmol)
to provide a clear viscous hygroscopic liquid at room temperature in 91% yield (1.41 g). Molecular Formula:
C47H45F18N9O18S6; Mol. Wt.: 1558.27; FTIR (cmꢀ1): 3070 (CꢀH)Ar, 2990 (CꢀH)Aliph, 1750 (C=O), 1661 (C=N),
1555, 1487 (C=C)Ar, 1340, 1210 (CꢀF), 1372, 1154 (O=S=O), 1207, 1169 (CꢀO); 1HꢀNMR (400 MHz, CD3OD)
δ ppm: 9.05 (s, 3H, CꢀHImidazole, minor), 9.03 (s, 3H, CꢀHImidazole, minor), 9.01 (s, 3H, CꢀHImidazole, major), 7.67
(bt~s, 6H, CꢀHImidazole, minor), 7.63 (bt~s, 6H, CꢀHImi, major), 7.59 (bt~s, 6H, CꢀHImidazole, minor), 7.43ꢀ7.21 (m,
15H, CꢀHAr), 5.45 (s, 6H, ArꢀCH2, minor), 5.43 (s, 6H, ArꢀCH2, major), 5.19 (s, 6H, OꢀCH2), 4.18 (s, 6H, Nꢀ
CH2, minor), 4.15 (s, 6H, NꢀCH2, major), 4.13 (s, 6H, NꢀCH2, minor), 1.05 (s, 3H, CH3, minor), 1.03 (s, 3H,
CH3, minor), 1.01 (s, 3H, CH3, major); 13CꢀNMR (100 MHz, CD3OD) δ ppm: 167.74 (C=O, major), 167.69
(C=O, minor), 138.88 (CHImidazole, minor), 138.79 (CHImidazole, major), 135.05 (ꢀCArꢀCH2ꢀ), 130.66 (2×CHA),
129.88 (2×CHA), 126.09, 122.91, 119.73, 116.55 (q, J=319, CF3), 125.65 (CHImidazole), 123.71 (CHImidazole), 68.15
(CH2ꢀO, minor), 68.01 (CH2ꢀO, major), 67.43 (CH2ꢀO, minor), 54.49 (CH2ꢀN), 50.97 (ArꢀCH2ꢀ), 40.14 (ꢀCꢀ),
͞
17.07 (CH3, minor), 17.00 (CH3, major). 19F (336, MHz) δ ppm: ‒79.97; HRMS: m/z, [M+3‒2H]−3NTF2 calcd.
͞
‒
for C41H43N6O65+ : 715.3244, found: 715.3281; m/z, [NTF2] calcd. for C2F6NO4S2 : 279.9173, found: 279.9164.
450
451
452
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453
454
Trisꢀ((Nꢀoctylꢀbenzimidazoliumylꢀacetayloxy)methyl)ethane bis(trifluoromethylsulfonyl)amide
(11d)
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
This compound was prepared analogously to 10a using trisꢀ((Nꢀoctylꢀbenzimidazoliumylꢀacetayloxy)methyl)
ethane chloride 9d (1.04 g, 1.0 mmole) and Lithium bisꢀ(trifluoromethanesulphonyl)imide LiNTf2 (1.0 g, 3.5
mmol) to provide a clear viscous hygroscopic liquid at room temperature in 90% yield (1.60 g). Molecular
Formula: C62H81F18N9O18S6; Mol. Wt.: 1774.71; FTIR (cmꢀ1): 3120 (CꢀH)Ar, 2945, 2920, 2850 (CꢀH)Aliph, 1742
1
(C=O), 1618 (C=N), 1566, 1483 1460 (C=C)Ar, 1360, 1220 (CꢀF), 1350, 1172 (O=S=O), 1192(CꢀO); HꢀNMR
(400 MHz, DMSOꢀd6) δ ppm: 10.03 (s, 3H, CꢀHBImidazole, major), 9.97 (s, 3H, CꢀHBImidazole, minor), 9.91 (s, 3H,
CꢀHBImidazole, minor), 8.13ꢀ8.05 (m, 6H, CHAr), 7.54ꢀ7.45 (m, 6H, CHAr, minor), 7.12ꢀ7.03 (m, 6H, CHAr, major),
5.83 (s, 6H, OꢀCH2, major), 5.79 (s, 6H, OꢀCH2, minor), 4.37 (t, J=7.07, 6H, αꢀCH2, major), 4.29 (t, J=7.07, 6H,
αꢀCH2, minor), 4.02 (s, 6H, NꢀCH2, minor), 3.97 (s, 6H, NꢀCH2, major), 1.92ꢀ1.86 (m, 6H, βꢀCH2), 1.22 (bs,
30H, bulkꢀCH2), 0.85 (s, 3H, CH3), 0.80 (t, 9H, J=6.80, ωꢀCH3); 13CꢀNMR (100 MHz, DMSOꢀd6) δ ppm: 168.10
(C=O, major), 166.72 (C=O, minor), 143.28 (CHBImidazole), 131.72 (CAr), 130.76 (CAr), 126.94 (CHAr), 126.71
(CHAr), 124.46, 121.23, 118.00, 114.76 (q, J=322, CF3), 113.96 (CHAr), 113.78 (CHAr), 62.78 (CH2ꢀO, minor),
62.13 (CH2ꢀO, major), 47.62 (CH2ꢀN), 46.95 (αꢀCH2), 38.43 (ꢀCꢀ), 31.24 (ωꢀ2), 28.58 (2), 28.47 (bulkꢀCH2),
25.77 (β), 22.15 (ωꢀ1), 21.07 (CH3, major), 20.78 (CH3, minor), 14.10 ((ω), minor), 13.94 ((ω), major). 19F (336,
͞
MHz) δ ppm: ‒80.02; HRMS: m/z, [M+3‒2H]−3NTF2 calcd. for C56H79N6O65+ : 931.6061, found: 931.6028;
͞
−
m/z, [NTF2] calcd. for C2F6NO4S2 : 279.9173, found: 279.9201.
471
Liquid crystal behaviour
472
473
474
475
476
Liquid crystalline properties of compounds 8bꢀf and 9bꢀf were investigated thermotropically and lyotropically.
Optical polarising microscopy (Olympus BHꢀ2 OPM equipped with Mettler FF82 hot stage and Mettler FP80
Central Processor), was used to identify the optical textures and the transition temperatures. A contact
penetration technique60 was applied in lyotropic investigation. It was carried out at room temperature with water
and 1ꢀundecanol as polar and nonpolar solvents, respectively. The images were recorded at 50× magnification.
477
Airꢀwater interface tension
478
479
480
481
482
483
The surface tensions were measured using KSV Sigma 702 tensiometer at 25 ± 0.5 ºC. The measurements were
based DuNouy ring method in five replications with a standard deviation of less than 0.1 mN mꢀ1. The critical
micelle concentration, cmc, was obtained from surface tension against logarithmic concentration plot through the
intersection of two regression lines, where one of them is concentration dependent. Solutions were prepared
using deionized water which was also filtered through 0.25 ꢀm pore membrane producing 71.96 ± 0.09 mN mꢀ1,
0.9996±0.0002 g mLꢀ1 and 1.0 ±0.1 ꢀS cmꢀ1 values for surface tension, density and conductivity, respectively.
484
Krafft point (TK)
485
486
487
488
489
490
The determination of Krafft temperature, (Tk), applied slow heating of 1 % (w/v) aqueous solution of ILs
surfactant in water bath. It was heated on an IKA hot plate stirrer equipped with temperature controller IKA
ETSꢀD4 at 5 ºC. minꢀ1 over the range 10 ºC to 50 ºC. The changes of transparency was optically monitored to
observe the temperature of clear solution formed.61
Closed Bottle Test
491
492
The biodegradability of synthesized ILs (i.e. 8bꢀg and 9bꢀg) was evaluated using ClosedꢀBottle test (OECD
301D) standard protocols.55 The analysis was based on biochemical oxygen demand (ꢀꢁꢂ) due to IL microbial
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493
494
495
degradation as reported.38 The ꢀꢁꢂ values were derived from the quantified respirometric dissolved oxygen
(ꢂꢁ) in a culture containing either IL or sodium nꢀdodecyl sulphate; SDS as a reference sample. The ꢂꢁ was
measured using CyberScan dissolve oxygen meter ꢂꢁ300 (Eutech Instruments; The Netherlands).
496
497
498
499
500
501
502
503
All samples were prepared in capped Scotch bottles, each containing 100 ml of sample solution at 100 mg/L
concentration of IL or reference sample in distilled water. Each sample bottle was inoculated with 1 mL of
microbial effluent collected from a wastewater treatment plant. Samples were prepared in three different groups
of 3 replicates per each sample. Group 1 contained both inoculum and the IL samples, Group 2 contained only
the inoculum (test blank) and Group 3 contained the inoculum and the reference sample (SDS). The solutions
were incubated in the dark at 25 ±1°C for 28 days under continuous shaking (200 rpm), and the ꢂꢁ values were
recorded after every 48 hours. Since the majority of biodegradation changes are only noticed within the first 16
days period of time, 10 and 16 days results were considered.
504
505
The ꢀꢁꢂ values were calculated based on observed ꢂꢁ using Equation 3 as reported in literature,62
ꢀꢁꢂ = ꢃꢄ ꢆꢃꢄ
(3)
ꢅ
ꢇ
506
ꢈ
507
508
509
where ꢂꢁꢉ is initial dissolved oxygen and ꢂꢁꢊ is the dissolved oxygen at time t. While ꢋ is fractional oxygen
volume defined as the ratio of the experimental ꢂꢁ volume to theoretical ꢂꢁ volume that obtained from
reference sample.
510
511
Further, the percentage biodegradation was calculated according to Equation 4 as following:38
ꢕꢄꢃ
% ꢀꢌꢍꢎꢏꢐꢑꢒꢎꢒꢓꢌꢍꢔ =
× 100
(4)
ꢘꢙ ꢚ
ꢘꢙ ꢜꢝꢘꢞꢟꢠ ꢡꢠꢢꢙꢣꢇ
ꢛ
ꢖꢗꢄꢃ (
)
512
513
where ꢤℎꢁꢂ represent the theoretical oxygen demand; the amount of oxygen consumed by the microorganisms
in sample corrected for the uptake of O2 by the blank inoculums.38
514
Acknowledgments
515
516
The authors thank the University of Malaya for financial support by High Impact Research Grant UMꢀMOE
UM.C/625/1/HIR/MOE/F00004ꢀ21001 from the Ministry of Education Malaysia.
517
References
518
519
520
521
522
523
524
525
526
527
528
529
1.
2.
3.
4.
5.
6.
K. R. Seddon, Nat. Mater., 2003, 2, 363ꢀ365.
J. S. Wilkes, Green Chem., 2002, 4, 73ꢀ80.
P. Wasserscheid and T. Welton, Ionic Liquids in Synthesis, 2 Volume Set, Wiley, 2007.
J. H. Davis, James, Chem. Lett., 2004, 33, 1072ꢀ1077.
P. Wasserscheid, R. v. Hal and A. Bosmann, Green Chem., 2002, 4, 400ꢀ404.
D. W. Rooney and K. R. Seddon, in Handbook of Solvents, ed. G. Wypych, ChemTec Publishing,
Toronto, Ontario 2001, pp. 1459ꢀ1484.
R. Sheldon, Chem. Commun., 2001, 2399ꢀ2407.
R. A. Sheldon, Green Chem., 2005, 7, 267ꢀ278.
C. M. Gordon, Appl. Catal. A: General, 2001/12/20/, 222, 101ꢀ117.
M. K. Munshi, P. S. Biradar, S. M. Gade, V. H. Rane and A. A. Kelkar, RSC Adv., 2014, 4, 17124ꢀ
17128.
7.
8.
9.
10.
19

Page 21 of 22
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View Article Online
DOI: 10.1039/C4RA14027C
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
11.
H. Li, Q. Zhang, X. Liu, F. Chang, D. Hu, Y. Zhang, W. Xue and S. Yang, RSC Adv., 2013, 3, 3648ꢀ
3654.
T. Welton, Chem. Rev., 1999, 99, 2071ꢀ2084.
12.
13.
14.
15.
16.
17.
18.
K. V. Axenov and S. Laschat, Materials, 2011, 4, 206ꢀ259.
W. Chi, H. Jeon, S. Kim, D. Kim and J. Kim, Macromol. Res., 2013, 21, 315ꢀ320.
D. Zhao, Y. Liao and Z. Zhang, CLEAN–Soil, Air, Water, 2007, 35, 42ꢀ48.
A. G. Santos, B. D. Ribeiro, D. S. Alviano and M. A. Z. Coelho, RSC Adv., 2014, 4, 37157ꢀ37163.
H. Hajfarajollah, B. Mokhtarani, A. sharifi, M. Mirzaei and A. Afaghi, RSC Adv., 2014, 4, 13153ꢀ13160.
M. Petkovic, J. L. Ferguson, H. Q. N. Gunaratne, R. Ferreira, M. C. Leitao, K. R. Seddon, L. P. N.
Rebelo and C. S. Pereira, Green Chem., 2010, 12, 643ꢀ649.
S. Stolte, M. Matzke, J. Arning, A. Boschen, W.ꢀR. Pitner, U. WelzꢀBiermann, B. Jastorff and J. Ranke,
Green Chem., 2007, 9, 1170ꢀ1179.
R. P. Swatloski, J. D. Holbrey, S. B. Memon, G. A. Caldwell, K. A. Caldwell and R. D. Rogers, Chem.
Commun., 2004, 668ꢀ669.
A. GarciaꢀLorenzo, E. Tojo, J. Tojo, M. Teijeira, F. J. RodriguezꢀBerrocal, M. P. Gonzalez and V. S.
MartinezꢀZorzano, Green Chem., 2008, 10, 508ꢀ516.
J. Pernak, K. Sobaszkiewicz and I. Mirska, Green Chem., 2003, 5, 52ꢀ56.
S. Morrissey, B. Pegot, D. Coleman, M. T. Garcia, D. Ferguson, B. Quilty and N. Gathergood, Green
Chem., 2009, 11, 475ꢀ483.
A. S. Wells and V. T. Coombe, Org. Process Res. Dev., 2006, 10, 794ꢀ798.
J. Ranke, K. Mölter, F. Stock, U. BottinꢀWeber, J. Poczobutt, J. Hoffmann, B. Ondruschka, J. Filser and
B. Jastorff, Ecotoxicol. Environ. Saf., 2004, 58, 396ꢀ404.
B. Jastorff, R. Stormann, J. Ranke, K. Molter, F. Stock, B. Oberheitmann, W. Hoffmann, J. Hoffmann,
M. Nuchter, B. Ondruschka and J. Filser, Green Chem., 2003, 5, 136ꢀ142.
K. M. Docherty and J. C. F. Kulpa, Green Chem., 2005, 7, 185ꢀ189.
K. J. Kulacki and G. A. Lamberti, Green Chem., 2008, 10, 104ꢀ110.
A. Latala, M. Nedzi and P. Stepnowski, Green Chem., 2010, 12, 60ꢀ64.
M. Matzke, S. Stolte, K. Thiele, T. Juffernholz, J. Arning, J. Ranke, U. WelzꢀBiermann and B. Jastorff,
Green Chem., 2007, 9, 1198ꢀ1207.
B. Jastorff, K. Molter, P. Behrend, U. BottinꢀWeber, J. Filser, A. Heimers, B. Ondruschka, J. Ranke, M.
Schaefer, H. Schroder, A. Stark, P. Stepnowski, F. Stock, R. Stormann, S. Stolte, U. WelzꢀBiermann, S.
Ziegert and J. Thoming, Green Chem., 2005, 7, 362ꢀ372.
R. S. Boethling, in Designing Safer Chemicals, American Chemical Society, 1996, vol. 640, ch. 8, pp.
156ꢀ171.
R. S. Boethling, in Cationic Surfactants, Surfactant Science Series eds. J. Cross and E. J. Singer, Marcel
Dekker, New York, 1994, vol. 53, pp. 95ꢀ135.
P. H. Howard, R. S. Boethling, W. Stiteler, W. Meylan and J. Beauman, Science of The Total
Environment, 1991, 109–110, 635ꢀ641.
N. Gathergood and P. J. Scammells, Australian J. Chem., 2002, 55, 557ꢀ560.
N. Gathergood, M. T. Garcia and P. J. Scammells, Green Chem., 2004, 6, 166ꢀ175.
N. Gathergood, P. J. Scammells and M. T. Garcia, Green Chem., 2006, 8, 156ꢀ160.
D. Coleman and N. Gathergood, Chem. Soc. Rev., 2010, 39, 600ꢀ637.
S. Wadud, R. Onodera and M. M. OrꢀRashid, Appl Microbiol Biotechnol, 2001, 55, 219ꢀ225.
X. Cheng, X. Bai, S. Jing, H. Ebert, M. Prehm and C. Tschierske, Chemistry – A Eur. J., 2010, 16, 4588ꢀ
4601.
N. V. Plechkova and K. R. Seddon, Chem. Soc. Rev., 2008, 37, 123ꢀ150.
F. Sander, S. Tussetschläger, S. Sauer, M. Kaller, K. V. Axenov and S. Laschat, Liq. Cryst., 2011, 39,
303ꢀ312.
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.
T. Ichikawa, M. Yoshio, A. Hamasaki, S. Taguchi, F. Liu, X.ꢀb. Zeng, G. Ungar, H. Ohno and T. Kato,
J. Am. Chem. Soc., 2012, 134, 2634ꢀ2643.
S. T. Handy, Chem. Eur. J., 2003, 9, 2938ꢀ2944.
20

RSC Advances
Page 22 of 22
View Article Online
DOI: 10.1039/C4RA14027C
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
45.
46.
47.
G.ꢀh. Tao, L. He, N. Sun and Y. Kou, Chem. Commun., 2005, 3562ꢀ3564.
J. Neumann, S. Steudte, C.ꢀW. Cho, J. Thoming and S. Stolte, Green Chem., 2014, 16, 2174ꢀ2184.
S. Stolte, S. Abdulkarim, J. Arning, A.ꢀK. BlomeyerꢀNienstedt, U. BottinꢀWeber, M. Matzke, J. Ranke,
B. Jastorff and J. Thoming, Green Chem., 2008, 10, 214ꢀ224.
S. Steudte, S. Bemowsky, M. Mahrova, U. BottinꢀWeber, E. TojoꢀSuarez, P. Stepnowski and S. Stolte,
RSC Adv., 2014, 4, 5198ꢀ5205.
48.
49.
J. W. Goodby, G. W. Gray, D. Demus, J. Goodby, G. W. Gray, H. W. Spiess and V. Vill, in Handbook
of Liquid Crystals, WileyꢀVCH Verlag GmbH, 2008, pp. 17ꢀ23.
50.
51.
52.
53.
54.
E. J. R. Sudholter, J. B. F. N. Engberts and W. H. De Jeu, J. Phys. Chem., 1982, 86, 1908ꢀ1913.
G. S. Attard, S. Fuller, O. Howell and G. J. T. Tiddy, Langmuir, 2000, 16, 8712ꢀ8718.
B. J. Boyd, C. J. Drummond, I. Krodkiewska and F. Grieser, Langmuir, 2000, 16, 7359–7367.
K. M. Docherty, J. K. Dixon and C. F. Kulpa Jr, Biodegradation, 2007, 18, 481ꢀ493.
M. J. Scott and M. N. Jones, Biochimica et Biophysica Acta (BBA) ꢀ Biomembranes, 2000, 1508, 235ꢀ
251.
OECD guideline for testing of chemicals, adopted by the council July 1992—ready biodegradability.
M. T. Garcia, N. Gathergood and P. J. Scammells, Green Chem., 2005, 7, 9ꢀ14.
S. P. M. Ventura, M. Gurbisz, M. Ghavre, F. M. M. Ferreira, F. Gonçalves, I. Beadham, B. Quilty, J. A.
P. Coutinho and N. Gathergood, ACS Sustainable Chem. Eng., 2013, 1, 393ꢀ402.
J. Ropponen, K. Nattinen, M. Lahtinen and K. Rissanen, CrystEngComm, 2004, 6, 559ꢀ566.
O. V. Starikova, G. V. Dolgushin, L. I. Larina, P. E. Ushakov, T. N. Komarova and V. A. Lopyrev,
Russian J. Org. Chem., 2003, 39, 1467ꢀ1470.
55.
56.
57.
58.
59.
60.
K. Rendall, G. J. T. Tiddy and M. A. Trevethan, J. Chem. Soc., Faraday Trans.1: Physical Chemistry in
Condensed Phases, 1983, 79, 637ꢀ649.
A. Piasecki and D. PiłakowskaꢀPietras, J Surfact Deterg, 2007, 10, 125ꢀ130.
V. MassardierꢀNageotte, C. Pestre, T. CruardꢀPradet and R. Bayard, Polym. Degrad. Stability, 2006, 91,
620ꢀ627.
61.
62.
607
608
21