Bifunctional hydrophobic ionic liquids: Facile synthesis by thiol-ene "click" chemistry

Article abstract of DOI:10.1039/c5gc01930c

We describe the facile, robust and orthogonal fabrication of a structurally comprehensive library of hydrophobic trimethoxysilyl-functionalized ionic liquids with C₇-C₁₅ thioether spacer, using thiol-ene "click" chemistry. The synthesized ionic liquids displayed very low glass transition temperatures, high thermal stability and were hydrophobic in character. And the ability to serve as surface coating agents was tested by immobilizing them on the surface of iron oxide supermagnetic nanoparticles and the organic loadings were quantified.

Full text of DOI:10.1039/c5gc01930c

View Article Online
View Journal
Green
Chemistry
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: M. Sanchez Zayas,
J. C. Gaitor, S. T. Nestor, S. Minkowicz, Y. Sheng and A. Mirjafari, Green Chem., 2015, DOI:
10.1039/C5GC01930C.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/greenchem

Please do not adjust margins
Green Chemistry
Page 1 of 10
View Article Online
DOI: 10.1039/C5GC01930C
Journal Name
ARTICLE
Bifunctional hydrophobic ionic liquids: Facile synthesis by thiol-
ene “click” chemistry
Manuel Sanchez Zayas, Jamie C. Gaitor, Stephen T. Nestor, Samuel Minkowicz, Yinghong Sheng
and Arsalan Mirjafari*
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
We describe the facile, robust and orthogonal fabrication of a structurally comprehensive library of hydrophobic
trimethoxysilyl-functionalized ionic liquids with C7−C15 thioether spacer, using thiol-ene “click” chemistry. The
synthesized ionic liquids displayed very low glass transition temperatures, high thermal stability and were
hydrophobic in character. And the ability to serve as surface coating agents was tested by immobilizing them on the
surface of iron oxide supermagnetic nanoparticles and the organic loadings were quantified.
functionalized ILs have been used for the fabrication of many
important materials and devices, including catalyst coated
magnetic and mesoporous metal oxides,5 metal-NHC
supported catalysts,6 organic-inorganic hybrid electrolytes for
lithium ion battery,7 dye-sensitized solar cells,8 CO2 capture,9
nanosilica-based ionogels and nanocamposites,10 thermally-
stable stationary phase for HPLC,11 electrochromic devices,12
and transducers.13
Introduction
Demands for the construction of advanced functional
materials with accurately engineered structures and properties
have increased significantly with the growing needs to address
resource, health, and energy challenges. In addition to the
structural requirements for the preparation of the novel
materials, scientists have also sought to synthesize them via
high-yielding, simple to perform, covalent and preferably
sustainable chemistry. These motivations in tandem with the
recent advances in “click” chemistry have created a growing
research area with concentration on robust, efficient, and
orthogonal methods for the preparation of new materials in
both fundamental and applied fields.1
Due to the nonvolatile nature of ILs, the challenges
traditionally associated with their functionalization
—
quantitative conversion, purification limitations (e.g.
ineffectiveness of distillation and crystallization methods due
to the lack of vapor pressure and their non-crystalline
structures) and controlling multiple reaction sites — represent
an important opportunity for efficient and functional group
tolerant strategies, such as “click” chemistry, to develop
concise methodologies for their synthesis. The chemo- and
regio-specificity, quantitative yields and orthogonality, that are
the hallmarks of click reactions, greatly enable the efficient
fabrication of functional ILs via the formation of new carbon-
heteroatom bonds, which fall within the realm of philosophy
of green chemistry.14
Recently, ionic liquids (ILs) have received a considerable
upsurge of interest as green solvents for organic synthesis and
separation technologies due to their superior physicochemical
properties (e.g. effectively non-existing vapor pressure, wide
liquid range, low flammability, high ionic and thermal
conductivity, wide electrochemical potential window, excellent
thermal, chemical and radiochemical stability and exceptional
solubility toward many substances, ranging from asphalt to
cellulose) over the conventional volatile organic solvents.2 By
incorporating ion-tethered functional groups into the IL
structures, an interesting subclass of ILs called task-specific
ionic liquids (TSILs),3 or simply functionalized ILs, has been
In this study, we report an efficient and robust photo-initiated
thiol-ene chemistry to synthesize
a series of tailored,
hydrophobic mercaptopropyltrimethoxysilane ILs containing
long alkyl spacers (C7−C15) with low melting points and high
thermal stability (Scheme 1). These ILs contain
trimethoxysilane moiety as an anchoring group to
hydroxylated surfaces such as inorganic oxides, which forms
strong covalent siloxane bonds to such surfaces, making them
particularly useful for bridging organic and inorganic
components. The thiol group, separated by an alkyl spacer
(C3−C11) from the cation, acts as a “symmetry-breaking” moiety
and imposes a significant depressive effect on the Tm values
without sacrificing hydrophobicity, according to our previous
report.15
generated as
a new class of materials with unique
physicochemical properties. These properties can be
customized by selecting the cations and/or anions for specific
tasks, ranging from organic synthesis and catalysis to energy,
materials and medicine.4
Particularly, trialkoxysilyl-
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 2 of 10
View Article Online
DOI: 10.1039/C5GC01930C
ARTICLE
Journal Name
Generally, modulation of functionality’s reactivity can be phenylacetophenone, 99% purity), 1-methylimidazole (98%
expected as a function of the length and structure of the purity), 1,2-dimethylimidazole (98% purity), triethylamine
spacers. However, their melting points begin to increase (99.7%), triphenylphosphine (99%) were purchased from Acros
significantly once an N-substituted tail exceeds seven carbon Organics and used without further purification. High purity
atoms for several homologous series of 1-alkyl-3- solvents, such as methylene chloride, methanol and hexanes
methylimidazolium ILs.16 However, we recently reported that it were purchased from Acros Organics and used without further
is possible to design 1-methyl-3-thiaalkylimidazolium purification. Potassium bistriflimide, employed for metathesis
bistriflimide ILs with alkyl chains as long as 20 carbons while reactions, was prepared via neutralization (pH = 7.0) of HNTf2
keeping their melting points below room temperature. This (Iolitec GmbH, 80%) with KOH followed by the removal of
was simply achieved by strategically incorporating sulfur atom water.
into the different positions of alkyl side chains via thiol-ene Characterization of the products using 1H and 13C was
reaction in order to incorporate a “kink” into the chains and performed on a Bruker 500 MHz NMR with multi-nuclear
disrupt packing, similar to natural fatty acids.15 The capabilities using DMSO-d6. Chemical shifts are reported
trialkoxysilane-functionalized ILs are uniquely amendable to relative to TMS as the internal reference at 0.00 ppm for both
1
unsymmetrical archetypes by introduction of sulfur atom, the H and 13C NMR data. ESI-MS analyses were performed by
which has profound implications on the physicochemical flow-injection on
a Thermo Scientific ion trap mass
properties of ILs. Furthermore, sulfur functionality enables the spectrometer using HPLC grade acetonitrile. As our interest
formation of an additional coordinative bond with metals that was in the cations of these salts, data was collected in positive
do not readily hydroxylate (e.g. Au, Ag and Pt), which have ion mode. Glass transition temperatures were determined by
difficulties with coating formation and/or adherence and using a TA Q20 differential scanning calorimeter, with a
significantly improves the effectiveness of organosilanes heating rate of 5 oCmin-1. Thermogravimetric analyses were
coupling with these less reactive metal substrates.17
performed using a TA instrument TGA Q50 under nitrogen
flow. Water content of samples was measured by coulometric
Karl-Fischer titration C20X from Mettler-Toledo. FT-IR spectra
were obtained by using JASCO FT-IR 4600. UV-Visible
absorption spectrum was obtained with Shimadzu UV 2450
spectrophotometer, using methylene chloride as solvent. FEI
Morgagni 268D TEM used as transmission electron
microscopy. Images were captured using an Olympus
MegaView III sidemount camera and measured with analySIS®
software from ResAlta Research Technologies. Dynamic
viscosity and density were measured by Stabinger Viscometer
SVM 3000 from Anton-Paar.
Scheme 1. Two-step preparation of ene-bearing ILs as starting
materials for the synthesis of imidazolium-type trimethoxysilyl-
functionalized ILs with long thioether spacers via photo-
initiated thiol-ene “click” reaction.
General Procedure for the synthesis of ene-bearing ILs
This is the first time that an efficient, robust and orthogonal
synthesis of a library of trimethoxysilyl-functionalized ILs (18
examples) with long thioether spacers (≥C7), while maintaining
the liquid state at ambient temperature, is reported. The
effects of structural variations on their physicochemical and
solvation properties are examined. In addition to their unique
physicochemical properties, it was found that the synthesized
marcaptosilane ILs can serve as active surface coasting agents.
In order to demonstrate that they can be employed as surface-
active materials, ILs with different spacer lengths (C7, C11 and
C15) were covalently bounded to iron oxide supermagnetic
nanoparticles (SPNs) and the IL loadings were quantified by
TGA. Also, the role of spacer lengths on the size of SPNs was
studied by transmission electron microscopy (TEM).
As shown in in Scheme 1, ene-bearing ILs was synthesized
using previously reported procedure from the literature with
some slight modification.15 Briefly,
1
equiv. of 1-
methylimidazole/1,2-dimethylimidazole (or triethylamine and
triphenylphosphine) was added slowly to 1.1 equiv. of
corresponding alkenyl bromide in toluene (Scheme 1, n = 1-3)
or acetonitrile (Scheme 1, n = 4-9). The reaction mixture was
allowed to stir for 2-3 days under reflux at 110 oC and 82 oC for
toluene and CH3CN, respectively. The crude product was
obtained by evaporating the solvent under reduced pressure,
washed it with excess of toluene to remove unreacted starting
materials and dried under vacuum to evaporate residual
solvents. It was dissolved in H2O and then added to a solution
of 1.1 equiv. of KNTf2 in H2O and stirred at room temperature
for 24 h. After drying, the residue was washed with H2O three
times and dried in vacuum in 70 oC for 12 h.
Experimental Section
The ene-bearing ILs were subjected to standard silver-ion tests
to ensure the completeness of the exchange of halide for the
Materials and Measurement
−
NTf2 anion. All gave negative results, indicating that residual
For the present study, all of the thiols employed were
commercially available in high purity and used without further
halide anion content in the salts was below accepted threshold
levels.
purification.
The
photoinitiator
(2,2-dimethoxy-2-
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 3 of 10
ARTICLE
View Article Online
DOI: 10.1039/C5GC01930C
Journal Name
General Procedure for the synthesis of mercaptopropylsilyl-
functionalized ILs
their syntheses. Consequently, access to trialkoxysilanes
depends upon the limited numbers of approaches. The N-
alkylation
of
the
1-methylimidazole
with
(3-
The synthesis of mercaptopropylsilyl-functionalized ILs is
shown in Scheme 1. In a dry 150 mL photochemical tube, 1
equiv. of ene-bearing ILs was added along with 0.5 equiv. of
the photoinitiator 2,2-dimethoxy-2-phenylacetophenone.
Minimal amount (<1 mL) of solvent, 1:1 ratio of DCM and
MeOH, was added and vigorously stirred until a homogenous
solution was obtained. The photochemical tube was capped
with a septum, purged with nitrogen, and then sealed with
Parafilm. The 3-mercaptopropyltrimethoxysilane (MPTMS) was
weighed into a syringe and added through the septum. The
contents were stirred briefly and then irradiated with UV for
8h at room temperature under nitrogen atmosphere. The
purification process was completed by washing the mixture
with hexanes (6 × 30 mL) and dried under vacuum at 70oC for
chloropropyl)trimethoxysilane is the most commonly
employed method for the preparation of trialkoxysilyl based
ILs because of its good to excellent yields and the readily
availability of starting materials.6-12 However, the major
limitation of this method is that only hydrophilic trialkoxysilyl-
based ILs with short alkyl spacer (C3) are synthesizable. Han et
al. reported Pd(II) immobilized on mesoporous silica using
imidazolium-based ILs as NHC ligands, containing an N1-
substituted propyltrimethoxysilane group and an N3-bonded
alkyl chain with different lengths for the hydrogenation of
alkenes and allyl alcohols. Pd(II)-NHC IL with a C10 side chain
demonstrates the higher selectivity in the hydrogenation of
allyl alcohol in comparison to the ILs with C1 and C4 side chains
and commercial Pd/C as well.6b Likewise, according to Alper’s
report, the N1-propyltrimethoxysilylated ILs with N3-octyl side
chain yields better results for the immobilization of Pt on Fe3O4
nanoparticles in terms of size of the nanoparticles, compared
to the C3 and C4 analogues for the selective hydrogenation of
α,β-unsaturated aldehydes.5a In a different approach, Kadib et
al. reported the hydrosilyation of alkenes using the Karsted’s
catalyst for the preparation of disilyated guanidine ILs.
Although the catalyst loading is quite low, it requires an
expensive Rh or Pd metal catalyst.18 In fact, both methods
mentioned above have only moderate functional group
tolerance and product regioselectivity and require post-
synthetic purification steps to remove excess metal/reactants
from moisture sensitive products. Not only does our strategy
have the potential to overcome many of these drawbacks, but
it also provides a facile and robust method to synthesize a
library of trimethoxysilyl-functionalized ILs, containing long
linear alkyl spacers (C7–C15) with the sulfur heteroatom
strategically placed from C4 to C12. The key objective of this
work is to develop a novel series of functional silane ILs that
are highly hydrophobic while being low melting salts. Recently,
Takamatsu et al. reported using the thiol-ene reaction for the
construction of mercaptopropylsilane ILs containing the
carboxylate anion, paired with different cations to serve as the
ionic component in the dielectric layer of a transducer with
improved electrostatic attraction between electrodes. In this
patent, neither the physicochemical properties, nor the
structure-property relationship of these ILs were discussed.13
The thiol-ene “click” chemistry can be used to regiospecifically
unite ene-bearing ILs with 3-mercaptopropyltrimethoxysilane
(MPTMS) to afford only linear mercaptoalkyltrimethoxysilyl-
12h. The IL products 1–16 were isolated as pale yellow liquids
in excellent yields (96–>99%).
General Procedure for the synthesis of functionalized magnetite
IL−Fe3O4 ionogel.
The IL-Fe3O4 ionogels were prepared according to a reported
procedure with some modifications.19 In an oven-dried flask, 1
mL of a 3.0 M FeCl2, 2 M HCl solution was mixed with 4 mL of
1.5 M FeCl3, 2 M HCl solution at room temperature. Then, 50
mL of 1.05 M NH4OH was added dropwise to the solution over
a 30 minute period. The dark black suspended particles were
separated from aqueous layer and then washed four times
with H2O and then three times with acetone. The collected
particles were then left to dry in an oven for 24 hours. Once
dried, the particles were crushed, weighed and placed in a
glass vial. An equal weight of oleic acid as added to the vial
with 1 mL of ethyl acetate per 0.1 g SPNs. Then, the vial was
capped and sonicated for 2h at room temperature. The
particles were magnetically separated, washed three times
with ample amounts of ethyl acetate, followed by three
washes with absolute MeOH, and then dried in vacuo. The
final oleate-coated SPNs (SPNs-OA) nanoparticles were
obtained as a dark brown power.
Oleate-coated SPNs (120 mg) and dioxane (60 mL) were added
to an oven-dried 100 mL flask. The flask was immediately
capped and purged with nitrogen. It was then sonicated for 30
min at room temperature to redisperse SPNs-OA particles.
Equal weights of the corresponding silane-functionalized ILs (1,
o
and 12) were added to the flask, placed in a 75 C oil bath
5
and heated for 48 h with vigorous stirring. The particles were
separated by a hand-held rare-earth magnet, washed it with
CH2Cl2 and acetone three times and then dried under vacuum
at 70 oC for 12h.
functionalized ILs
1–16 (Figure 1). The process is
experimentally simple, wide in scope and it was performed
using an approach modeled by Garrell et al.19 In this method,
equimolar amounts of ene-bearing ILs and MPTMS and 0.5 mol
photoinitiator DMPA (2,2-dimethoxy-2-phenylacetophenone)
(see ESI, Figure S1) are mixed in the presence of a minimal
amount of solvent (1:1 ratio of MeOH/DCM; 0.5-1 mL) and
irradiated at room temperature for 8 h. The resulting IL
products were formed in high yields with no chromatographic
separation required and were simply purified by washing with
Results and discussion
Synthesis: A “click” paradigm
In general, the relative hydrolytic instability of trialkoxysilanes
and trimethoxysilanes in particular, has significantly restricted
the range of useful methods and experimental conditions for
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 4 of 10
View Article Online
DOI: 10.1039/C5GC01930C
ARTICLE
Journal Name
hexanes, which none of the starting and product ILs were variety of cations and could be readily functionalized and
soluble, to remove small amounts of unreacted MPTMS, and purified. Also, the hydrophobicity of ILs can be controlled by
decomposed photoinitiator. As noted, the reaction is inclusion of additional nonpolar moieties into their structures.
operationally simple, oxygen- and water-tolerant conditions, Typical non-coordinating, hydrophobic bis(trifluoromethane-
−
and generate products in high yields with minimal sulfonyl)imide [NTf2 ] anion, which is highly stable from both
requirements for product purification process, which does not thermal and hydrolytic standpoints, was used.
involve the use of halogenated solvents nor chromatographic Both the 1H and 13C NMR spectra of each
1
–
16 clearly illustrate
separation. All are in accordance with the principles of Green complete hydrothiolation, which was readily ascertained on
Chemistry.
the basis of 1H NMR peak integration and the disappearance of
Mirjafari and O’Brien recently reported that the type of the olefinic peaks of the starting cations. This was further
solvent has a profound effect on the outcome of thiol-ene confirmed by their ESI-MS spectra. Despite extensive work, an
reaction. In the presence of a polar protic solvent like MeOH, X-ray crystal structure was not obtained for ILs
1 and 15,
−
the regioselectivity of thiol-ene reaction is reversed to afford paired with [BPh4 ] anion, most likely because
Markovnikov-oriented products in excellent yields, which led trimethoxysilane group diminishes the crystallinity of ILs.
to the formation of ILs with branched thioether lipidic tails that
have different physicochemical properties in comparison to
their linear counterparts.20 In order to avoid formation of
branched ILs for the work described within, we used 1:1
S
Si(OMe)3
Si(OMe)3
S
N
N
N
N
2
1
2
1
CH2Cl2/MeOH ratio. On the basis of H and 13C NMR, and MS,
Si(OMe)3
Si(OMe)3
S
S
N
N
N
no Markovnikov-oriented (branched) products were obtained
during the course of this study.
N
3
5
4
4
3
Using small quantities of photoinitiator relative to alkene
(mol/mol) in this reactions, did not lead to the satisfactory
results under air or nitrogen, prompting us to considerably
increase the amount photoinitiator (10 times more than
amount reported in Ref. 19). There was no significant
difference in outcomes whether the reactions were conducted
under nitrogen or air.
Si(OMe)3
Si(OMe)3
S
S
N
N
N
N
6
5
6
Si(OMe)3
Si(OMe)3
Si(OMe)3
Si(OMe)3
Si(OMe)3
S
S
N
N
N
N
N
N
7
8
6
8
7
The scope of the study was expanded to ILs with imidazolium
and ammonium cations bearing multiple ene groups. Reacting
these ILs with additional amounts of MPTMS under the same
reaction conditions led to the quantitative formation of the
desired polyadducts (Figure 1, IL 14) and were isolated in
excellent yields. However, the synthesis of IL 14 required a
longer irradiation time and additional amounts of
photoinitiator to achieve satisfactory product yields.
S
S
N
N
N
N
7
8
10
9
S
Si(OMe)3
S
N
N
9
11
12
A series of ene-bearing ILs containing C3−C11 side chains
including imidazolium, ammonium and phosphonium cations
can be quantitatively clicked with MPTMS to form the 17
Si(OMe)3
S
N
N
9
13
examples
of
structurally
comprehensive
16). The
mercaptopropyltrimethoxysilane ILs (Figure 1,
1
–
Si(OMe)3
S
(MeO)3Si
N
S
N
synthesis of imidazolium-based ene-bearing ILs from the N-
alkylation of imidazole with alkenyl bromide, followed by
metathesis with KNTf2, is shown in Scheme 1. This process is
14
extensively studied as
a standard procedure for the
S
Si(OMe)3
Et3N
S
Si(OMe)3
Ph3P
preparation of ILs with a high product yields in each step.16a
Imidazolium-based ILs are an extensively studied class of
materials because of the relatively low reagent costs and ease
of functionalization. The C2-position of imidazolium-based ILs
has an acidic proton, which favors hydrogen bonding with
anions and discourages the formation of higher melting point
ILs. Ammonium and phosphonium cations are commonly used
in ILs structures because of their ease of customization and
control over physicochemical properties;21 in addition,
phosphonium salts show very high thermal stability.22
Therefore, the strategy employed in this study involved the
design of hydrophobic ILs with low melting points, containing a
15
16
Figure 1. Cation Structures of trimethoxysilane-functionalized
−
ILs (the anion, [NTf2 ], is not shown), resulting from
photoinduced thiol-ene “click” reaction of ene-bearing ILs with
3-mercaptopropyltrimethoxysilane.
MPTMS was chosen as a silane precursor for the thiol-ene
reaction due to its superior reactivity for surface coating
relative to other alkylsilanes, combined with its commercial
availability at a low cost. It coupled successfully to ene-bearing
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 5 of 10
ARTICLE
View Article Online
DOI: 10.1039/C5GC01930C
Journal Name
o
ILs with no evidence of hydrolysis of the trimethoxysilane 80 C) is a combination of following factors: a) instruction of
group or cocondensation to form silane dimers. Therefore, we asymmetry by incorporation of the sulfur and trimethoxysilane
studied the simplicity and feasibility of scaling up the thiol-ene groups, b) “kink” effect produced by the sulfur heteroatom, c)
coupling of [allylmim][NTf2] (Scheme 1, n = 1, R = H) with charged-diffused, relatively large imidazolium cations and d)
MPTMS in order to resynthesize IL
reaction was selected because of the relatively low cost of IL 16, as a functionalized alkyltriphenylphosphonium salt,
starting materials and similarity of IL
to one the few showed the highest Tg (23.05 oC) in this series. Inclusion of the
commercially available mercaptosilanes.23 Following UV sulfur
and trimethoxysilane groups into the
1
on a >10 g scale. This effective charge distribution of the NTf2- anion.
1
irradiation of reactants for 8h, the reaction reached complete allytriphenylphosphonium-based IL converts a crystalline solid
conversion (measured by 1H, 13C NMR) and the obtained salt to an amorphous IL, which is liquid at room temperature.
isolated yield is 91%, which is slightly lower than small scale
reaction.
Table 1. Thermophysical properties of ILs synthesized in this
study
MW/gmol-1
599.65
613.68
627.70
641.73
655.76
669.79
683.81
683.81
697.84
697.84
711.87
711.87
725.89
618.74
711.84
822.02
Tg/oCa
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
<-80
23.05
Tonset5%/oCb
245.81
263.69
326.58
365.38
342.11
323.99
338.01
342.26
330.62
336.97
321.79
306.95
341.61
330.92
313.33
274.90
Thermophysical properties and solubility: Structure-property
relationships study
IL
1
2
The thermophysical properties including phase transition
behavior and thermal stability of these 16 new ILs were
studied using differential scanning calorimetry (DSC) and
thermal gravimetric analysis (TGA), and results compiled to
create Table 1. No melting or glass transition temperatures
3
4
5
6
o
o
7
were detected upon heating to 150 C and cooling to -80 C,
for the synthesized ILs, except IL 15 where their glass
transition temperatures (Tg; midpoints of phase transitions) is
23.05 oC.
8
9
10
11
12
13
14
15
16
The phase transition temperature of ILs is controlled by three
major factors: intermolecular forces, molecular symmetry and
the conformational degrees of the freedom.24 Our previous
report dictates that the total number of carbon atoms and
asymmetry of the cations govern the phase transition
temperature of ILs.20 Indeed, the Si(OMe)3 group is the main
structural feature of the new ILs that appears to have an
substantial influence upon lowering the phase transitions by
adding a degree of asymmetry. Another likely explanation for
the observed complete disappearance of crystallinity and very
low Tg values is that the heightened rotational freedom of the
long chains reduces lattice energy of the ILs, leading to the
situation in which high chain flexibility predominates over the
polarity of trimethoxysilane group. In this context, Jovanovski
et al. reported a very low Tg value of -64.4 oC for 1-methyl-3-[3-
(trimethoxysilyl)propyl]-imidazolium iodide, which illustrates
that the depression in the glass transition point brought about
by the inclusion of a Si(OMe)3 moiety is substantial regardless
of the nature of the anion.25 Typically, the rotational
disordered state of the bis(trifluoromethanesulfonyl)imide
[NTf2] anion in crystalline salts leads to the considerable Tm/Tg
depression, in comparison to halogen anions. Moreover,
Rothenberg et al. have proposed the former domain
constitutes a symmetry-breaking region, the impact of which is
eventually outweighed by that of the cumulative inter-chain
dispersion forces of progressively longer alkyl groups.24 Using
cues from biology, O’Brien et al. demonstrated that strategic
inclusion of a sulfur heteroatom into the symmetry-breaking
region of alkyl chains has a profound depressive effects on the
Tm/Tg values of amphiphile ILs by imparting a “kink” into the
chains and disrupt packing.15 Overall, the explanation for the
lack of packing efficiency of the crystal lattice in the structures
of the synthesized ILs and their very low Tg values (less than -
<-80
b
aTg = glass transition temperature. Temperature at which
5 wt % loss of ILs is observed.
The thermal decomposition temperature (Tonset5%
) was
determined using thermal gravimetric analysis (TGA) and
evaluated at 5% mass loss of the samples. Tonset5% values
substantially varied between the new ILs, as the exhibited 5%
weight loss between 245.81 oC and 365.38 oC, as shown in
Table 1. The thermal stability of the mercaptosilane ILs were
found to be notably greater than those have been observed
for many traditional ILs (1-alkyl-3-methylimidazolium-based ILs
typically have thermal stabilities ranging from 145–185 C16a).
o
Among these compounds, IL
4 exhibited the highest thermal
stability having Tonset5% of 365.38 oC, which may be one the
highest thermal stability for organic compounds. Although a C–
S bond is more thermally labile relative to a C–C bond,26 we
observed that the Tonset5% of IL
4
is higher than that of the
all-carbon reference compound,
Tonset5% of ~
65.38 oC) due to excellent
corresponding
[C10mim][NTf2],27
(ꢀ
thermal stability of trimethoxysilane group.
As shown by Sharma et al., cation-tethered functional groups
are able to significantly impact the solvent parameters of ILs
(Abraham parameter), which in turn have profound influence
on the bulk properties of the materials.28 To provide further
insight into structure-property relationship of the new ILs and
their bulk properties, dynamic viscosity (ƞ) and density (ρ) of a
representative IL
(
1)
were measured as function of
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 6 of 10
View Article Online
DOI: 10.1039/C5GC01930C
ARTICLE
Journal Name
temperature at 1 bar and are shown in Figure 2 graphically and Table 2. Comparative dynamic viscosity and density of IL
1
and
Ref.
29
Table S1 (see ESI). The obtained data was compared with the its alkyl and thioether analogs at 20 oC.
Row
IL
η
(mPa·s)a
ρ
(g/cm3)b
1.34
corresponding all-carbon and thioether references with the
same number of side-chain backbone atoms (Table 2). As
anticipated, the incorporation of sulfur and trimethoxysilane
1
77.2
functionalities has great influence on the viscosity of IL
1 in
comparison to ILs with alkyl and thioether-containing
structural counterparts. For instance, [C7C1im][NTf2], with its
2
3
149.9
201.5
1.47
1.38
30
―
saturated all-carbon side chain, has a
η
value of 77.25 mPa·s at
20 C29 but the replacement of its C4 methylene unit with a
sulfur atom provides its thioether counterpart with the value
η = 72.2 oC). Likewise, as shown
in Table 2, introduction of trimethoxysilane functionality to
form IL increased the
value to 201.5 mPa·s at 20 oC, which
is greater than the dynamic viscosity of its reference
o
η
o
of 149.9 mPa·s at 20 C.30
(ꢀ
aη = Dynamic viscosity. bρ = Density
Computational modeling and simulation
1
η
Molecular modeling can be a useful tool to establish both
qualitative and quantitative relations between the properties
of ILs and their structures. The molecular modeling was
o
compounds (ꢀ
η = 124.3 C and 51.6 oC for Entries 1 and 2 of
Table 1, respectively). Both of these trends are consistent with
increased inter-particle interaction brought upon by the
grafting of powerfully associating functional groups. For many
ILs, viscosity is a strong function of temperature near room
temperature, as is the case for the representative IL, with
conducted using IL
1 as the model. The structure of 1 was
optimized using the B3LYP exchange–correlation functional32
and the 6-311++G (d,p) basis set as implemented in the
Gaussian09 suite of programs.33 Stable structures were
confirmed by computing analytic vibrational frequencies.
viscosity varying over
7 orders of magnitude in the
temperature range studied (Figure 2).
Figure 3 shows the most stable conformation for IL
1 and its C7
reference compound with an all-hydrocarbon spacer. Only
front-conformations were obtained, while no top
conformation was found due to the presence of the flexibility
of the bulky NTf2 anion. The study also indicates a nonbonded
1.5
1.4
1.3
1.2
1.1
1
700
600
500
400
300
200
100
0
Viscosity
Density
interaction (C—H⋯N hydrogen bond; 1.9795 Å) between the
anion and the acidic hydrogen at C2 position of the
imidazolium ring. In addition, the electron density isosurface of
IL
1 and the all-carbon reference IL are shown in the
electrostatic potential energy map in Figure 1. The ESP
mapping illustrates the polarization of the cation with the
imidazolium ring as the blue region and Si(OMe)3 and S groups
as the regions with least positive charge region on the cation
(yellow colored) (Figure 3d). Clearly, the negative charge is
located on the formal anion (red colored).
0
20
40
60
80
100
Temperature (˚C)
Figure 2. The dynamic viscosity (ꢀ) and density (ꢁ) of IL 1 from
0 to 100 oC.
a)
b)
Generally, the ILs’ density was found to be dependent to the
−
nature of anion (1-alkyl-3-methylimidazolium ILs with [NTf2 ]
S4
C5
C6
C7
C1
C3
Si
C7
C5
C6
C3
C4
C2
C1
C2
Si
anion has the greater density among other common anions16a
)
and to increase with increasing the length of hydrocarbon
chain linkage. However, the density of the IL is slightly lower
1
compared to its thioether analogue (Figure 2 and Tables 2). As
is typical, the densities of each compound decreases slightly
with temperature, as the compounds are liquids far removed
from their critical points.
c)
d)
The miscibility of ILs with both water (polar) and hexanes
(nonpolar) solvents was evaluated. The low water solubility
observed for the synthesized ILs (less than 0.20% w/v) makes
them ideal hydrophobic compounds. Increasing the length of
spacers led to the decreasing of their water content. In
addition, these ILs are insoluble at 0.1% (w/v) in hexanes.
Indeed, the fact that these ILs are immiscible both in water
and hexanes can be a further added to their usefulness (see
ESI, Figure S2).31
Figure 3. a) The optimized structure of reference IL with an all-
carbon spacer at the B3LYP/6-311++G(d,p) level. b) The
optimized structure of IL 1 at the B3LYP/6-311++G(d,p) level. c)
The electrostatic potential energy map of reference IL with an
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 7 of 10
ARTICLE
View Article Online
DOI: 10.1039/C5GC01930C
Journal Name
all-carbon spacer. d) The electrostatic potential energy map of kinked chains leads to the substantial melting point depression
IL
1.
of the long-chain ILs.
All inter-ion interactions were taken into account by explicitly
modeling the entire liquid structure using DFT computations of
the highest occupied molecular orbital (HOMO) and lowest
unoccupied molecular orbital (LUMO) energies. Figure 4 shows
the MO patterns of the HOMO and the LUMO of the all-carbon
reference IL (a and b) and IL
1 (c and d). The HOMO orbital in
the structure of reference IL is more localized on the nitrogen
-
and oxygen atoms of the [NTf2 ] anion (Figure 4a), while the
LUMO orbital is localized on the imidazolium ring (Figure 4b)
and the HOMO–LUMO gap is 5.96 eV. In contrast, the HOMO
orbital of IL
LUMO orbital is on the imidazolium cation similar to the
reference IL (Figure 4d). In IL , the HOMO–LUMO gap is
reduced to 4.50 eV, likely due to the intramolecular transition
1 is localized on the sulfur atom (Figure 4c) and the
1
in IL
IL.
1
versus intermolecular transition in the case of reference
a)
b)
C7
C5
C3
C1
Si
C6
C4
C2
c)
d)
S4
C3
C7
C1
C6
Si
C2
C5
Figure 5. Relative conformational-energy landscape of the
imidazolium cation with C6 side chains for the rotation
about the C2–C3–X4–C5 (left) and C3–X4–C5–C6 (right)
where the X = C, O and S.
Figure 4. Molecular orbitals of HOMO and LUMO of C7
reference compound with an all-carbon spacer (a and b,
respectively). Molecular orbitals of HOMO (c) and LUMO of IL
(d).
1
Surface coating applications: Ionogel formation
Recently, preparation, stabilization and functionalization of
inorganic nanoparticles with ILs have been considerably
studied.34 A subclass of hybrid materials called ionogels are
formed by incorporating ILs on a variety of inorganic supports
In Figure 5, the conformational-energy landscapes of the
[C6mim] cation and its ether and thioether counterparts are
depicted as a function of dihedral angle of C2–C3–X4–C5 and
C3–X4–C5–C6 (X = C, O or S), relative to the angle at the
energy maxima. The results of the calculations are nearly
identical to the previously reported calculations for atomic-
level structures of n-pentane and its heteroatom analogues,15
demonstrating that the energy barrier between gauche and
anti conformations of the thioether analogue is lower than
that of the ether and hydrocarbon counterparts. This energy
gap is because of the difference in bonds length of C–S and C–
C (184 pm vs. 153 pm) and also C–S–C bond angles relative to
including
silica
nanoparticles,
metal/metal
oxide
nanomaterials, polymers, gelators and carbon nanotubes. As a
novel class of materials, they are broadly used in the fields of
immobilized
catalysts,
dye-synthesized
solar
cells,
supercapacitors, solid electrolyte-gated organics and drug
delivery.35,36 Ionogels are a class of hybrid materials that
combine the properties of ILs with organic/inorganic solid
host networks in order to obtain the solid and malleable
materials while retaining the unique properties of the IL
including large electrochemical window, high specific
capacitance, and high ionic conductivity. Importantly, by
adjusting the interaction between the ILs guest and their hosts
via the strategic introduction of different functionalities in ILs,
C–C–C angles (~ ~
99o vs. 109o). Considering the rotation of
both C–S bonds, the thiaalkyl chain has seven low-energy
conformation15 that imply the “kink” effect into the structures
of thioether linkages. Consequently, the high population of
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 8 of 10
View Article Online
DOI: 10.1039/C5GC01930C
ARTICLE
Journal Name
task-specific ionogels can be formed, which are tailored for magnetite SPNs coated with oleate demonstrated significantly
specific applications. higher IL loading compared to the bare SPNs (IL @SPNs-OA =
The feasible incorporation of functionalized ILs into the 39.81 wt%; IL @SPNs-OA = 31.29 wt%; IL 12@SPNs-OA =
structure of inorganic frameworks could induce accurate 27.40 wt%) (Figure 6). In this case, the IL with C7 spacer has
1
5
1
control over surface properties by modification of the profoundly higher IL loading. The plausible reasons for the
hydrophilic/hydrophobic profile, alteration of the surface loading variability is difference in ILs’ solubility in dioxan and
activity and adjustment of the bulk properties of these hybrid interaction between ILs and oleate moiety on SPNs.
materials. In this respect, the synthesized silane-functionalized The size of individual nanoparticles was measured by
ILs were found to be active surface coating agents and were transmission electron microscopy (TEM), which indicates
successfully bounded to the cations on the surface of average sizes of 6.74 ± 0.63, 10.12 ± 0.33 and 9.23 ± 0.41 nm
magnetite supermagnetic Fe3O4 nanoparticles (SPNs) to form a for the IL 1@SPNs-OA, IL 5@SPNs-OA and IL 12@SPNs-OA,
novel class of hydrophobic ionogels as shown in Scheme 2. respectively (see ESI, Figure S6).
Supermagnetic Fe3O4 is one the most widely used
nanosupports for anchoring of the silane ligand guests due to
its high surface area and the presence of OH groups in the
addition of advantageous facile separation. Furthermore,
magnetic nanoparticles are distinguished as highly stable and
low toxicity materials that have gained increasing attention in
many catalytic34a and biological35 fields.
In this study, we first prepared magnetite nanoparticles via co-
precipitation of Fe (II) and Fe (III) salts in a basic solution,
according to Massart’s methods.37 Typically, Fe3O4 magnetic
nanoparticles prepared via this method are characterized with
a diameter of 5–15 nm, as confirmed by TEM analysis. These
magnetic nanoparticles are slightly soluble in protic solvents
and have the tendency to agglomerate to decrease their high
surface energy that emerges from the high surface area to
Figure 6. TGA curves of supported ILs on magnetite SPNs
coated with oleate (IL @SPNs-OA = 39.81 wt%; IL @SPNs-OA
volume ratio.
1
5
= 31.29 wt%; IL 12@SPNs-OA = 27.40 wt%)
Conclusions
In summary, the thiol-ene “click” transformation described
here is a high-yielding and simplistic fusion process, leading to
a series of hydrophobic, multifunctionalized ILs containing long
thioether spacers (C7−C15) with low melting points and high
thermal stability. The process exhibits broad scope and
Scheme 2. Preparation of functionalized magnetite SPNs with
trimethoxysilyl-based ILs.
To verify that the synthesized ILs could be used as surface
coating agents, ILs
(IL @SPNs, IL @SPNs and IL 12@SPNs) and magnetite
supermagnetic Fe3O4 nanoparticles coated with oleate (IL
@SPNs-OA, IL @SPNs-OA and IL 12@SPNs-OA). Oleate
coated SPNs were heated at 75oC in dioxane for 48h. After
particle isolation with a hand-held rare earth magnet and
rinsing with acetone three times, the resulting constructs were
characterized by TGA, TEM and FT-IR spectroscopy (For FT-IR
and TEM data, see ESI, Figures S5 and S6). According to the
obtained data, the particle size and particle loading are
considerably dependent upon the spacer lengths.
1, 5 and 12 were supported on bare SPNs
provides
a
series of imidazolium, ammonium and
1
5
phosphonium-based mercaptosilyl-functionalized ILs (16
examples) in excellent yields and exclusive anti-Markovnikov
regioselectivity. In addition, the reaction can be scaled-up
simply without sacrificing the product’s yield or purity. In order
to aid in defining their practical range of use in various
applications, the thermophysical properties of the new ILs
such as glass transition temperature, decomposition
temperature, viscosity and density along with their water
contents, were studied. The mercaptosilane class of ILs can
have important applications due to their hydrophobicity,
moderately low viscosities, high thermal stabilities and wide
liquids range. The synthesized ILs were found to be active
surface coating agents and were successfully immobilized on
magnetite SPNs.
1
5
TG analysis was conducted to prove the existence of the ILs
part in the hybrid nanoparticle structures and the results show
that all six compounds had mass loss around 100 oC because of
desorbed inner water molecules. Further mass loss at higher
temperature was related to the elimination of ILs, immobilized
The ability to introduce trimethoxysilane into the structures of
ILs would open new horizons for their applications such as
surface modification and hybrid materials. The incorporation
of a thiol group to the structure of silane-functionalized ILs
on the surface of Fe3O4 nanoparticles. The loading of the ILs
1,
5
and 12 on bare SPNs were 5.15 wt%, 16.39 wt% and 4.56
wt%, respectively (see ESI, Figure S3). On the other hand,
8 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Green Chemistry
Page 9 of 10
View Article Online
DOI: 10.1039/C5GC01930C
ARTICLE
Journal Name
X. Ma, J. Li, M. Sheu, A. Righter and A. Gilmore, US
2015/014033 A1, 2015.
18 A. El Kadib, P. Hesemann, K. Molvinger, J. Brandner, C.
Biolley, P. Gaveau, J. J. E. Moreau and D. Brunel, J. Am.
Chem. Soc., 2009, 131, 2882.
19 A. K. Tucker-Schwartz, R. A. Farrell and R. L. Garrell, J. Am.
Chem. Soc., 2011, 133, 11026.
20 A. Mirjafari, R. A. O’Brien, K. N. West and J. H. Davis Jr.,
Chem.– Eur. J., 2014, 20, 7576.
21 D. M. Eike, J. F. Brenneke and E. J. Maginn, Green Chem.,
could be utilized to construct novel organic-inorganic materials
due to strong affinity of thiols to specific metallic surfaces.
Acknowledgements
A.M. and M.S.Z. gratefully acknowledge the generous support
from the Alice and Karl Sheffield Scholarship. A.M. also thank
Ms. Mobarrez at Arthrex Inc. for experimental assistance and
Dr. O’Brien at USA for insightful comments. We acknowledge
Department of Chemistry of USF for providing NMR
Spectroscopy service. Dr. Kavallieratos and Dr. Govor at FIU
are thanked for performing 29Si NMR experiment.
2003, 5, 323.
22 C. G. Cassity, A. Mirjafari, N. Mobarrez, K. J. Strickland, R. A.
O’Brien and J. H. Davis Jr., Chem. Commun., 2013, 49, 7590.
23 3-(2-pyridylethyl)thiopropyltrimethylsilane (SIP6926.2) sold
by Gelest Inc.
24 I. Lopez-Martin, E. Burello, P. N. Davey, K. R. Seddon and G.
Rothenberg, ChemPhysChem, 2007, 8, 690.
Notes and references
25 V. Jovanovski, B. Orel, R. Ješe, G. Mali, E. Stathatos and P.
Lianos, Int. J. Photoenergy, 2006, 2006, 1.
26 J. A. Kerr, Chem. Rev., 1966, 66, 465.
27 P. S. Kulkarni, L. C. Branco, J. G. Crespo, M. C. Nunes, A.
Raymundo and C. A. M. Afonso, Chem.–Eur. J., 2007, 13,
8487.
28 N. K. Sharma, M. D. Tickell, J. L. Anderson, J. Kaar, V. Pino, B.
F. Wicker, D. W. Armstrong, J. H. Davis Jr. and A. J. Russell,
Chem. Commun., 2006, 646.
29 T. Mandai, M. Imanari and K. Nishikawa, Chem. Phys. Lett.,
2011, 507, 100.
30 R. A. O’Brien, A. Mirjafari, V. Jajam, E. N. Capley, A. C.
Stenson, K. N. West and J. H. Davis Jr., Tetrahedron Lett.,
2011, 52, 5173.
31 (a) G. -T. Wei, Z. Yang, C. -Y. Lee, H. -Y. Yang, C. R. Wang and
J. Am. Chem. Soc. 2004, 126, 5036; (b) H. Itoh, K. Naka and Y.
Chujo, J. Am. Chem. Soc. 2004, 126, 3026; (c) P. Cui, H. He, D.
Chen, H. Liu, S. Zhang, and J. Yang, Ind. Eng. Chem. Res.,
2014, 53, 15909.
32 (a) A. D. Becke, J. Chem. Phys., 1993, 98, 5648; (b) W. Yang
and R. G. Parr, Phys. Rev. B: Condens. Matter, 1988, 37, 785;
(c) P. J. Stephens, F. J. Devlin, C. F. Chabalowski and M. J.
Frisch, J. Phys. Chem., 1994, 98, 11623.
1
R. K. Iha, K. L. Wooley, A. M. Nyström, D. J. Bruke, M. J. Kade
and C. J. Hawker, Chem. Rev., 2009, 109, 5620.
(a) T. Welton, Chem. Rev., 1999, 99, 2071; (b) P.
2
Wasserscheid and T. Welton (Eds), Ionic Liquids in Synthesis,
Wiley-VCH Verlag, Weinheim, 2008; (c) J. P. Hallett and T.
Welton, Chem. Rev., 2011, 111, 3508.
3
4
J. H. Davis Jr., Chem. Lett., 2004, 33, 1072.
(a) P. S. Kulkarni and C. A. M. Afonso, Green Chem., 2010, 12
1139; (b) R. Ferraz, L. C. Branco, C. Prudêncio, J. P. Noronha
and Ž. Petrovski, ChemMedChem, 2011, , 975; (c) S. Tang, G.
,
6
A. Baker and H. Zhao, Chem. Soc. Rev., 2012, 41, 4030; (d) A.
Brandt, J. Gräsvik, J. P. Hallett and T. Welton, Green Chem.,
2013, 15, 550; (e) D. R. MacFarlane, N. Tachikawa, M.
Forsyth, J. M. Pringle, P. C. Howlett, G. D. Elliott, J. H. Davis,
M. Watanabe, P. Simon and C. A. Angell, Energy Environ. Sci.,
2014, 7, 232.
5
6
(a) R. Abu-Reziq, D, Wang, M. Post and H. Alper, Adv. Synth.
Catal., 2007, 349, 2145; (b) J. Wang, B. Xu, H. Sun and G.
Song, Tetrahedron Lett., 2013, 54, 238.
(a) B. Karimi and D. Enders, Org. Lett., 2006, 8, 1237; (b) G.
Liu, M. Hou, T. Wu, T. Jiang, H. Fan, G. Yang and B. Han, Phys.
Chem. Phys. Chem., 2011, 13, 2062.
33 Gaussian 09, Revision D.01, M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G.
Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H.
Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J.
Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J.
E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K.
N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K.
Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi,
M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B.
Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A.
Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D.
Daniels, Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski
and D. J. Fox, Gaussian, Inc., Wallingford CT, 2009.
7
8
9
Y. Lu, K. Korf, Y. Kambe, Z. Tu and L. A. Archer, Angew. Chem.
Int. Ed., 2014, 53, 488.
E. Stathatos, V. Jovanovski, B. Orel, I. Jerman and P. Lianos, J.
Phys. Chem. C., 2007, 111, 6528.
J. M. Zhu, F. Xin, Y. C. Sun and X. C. Dong, Theor. Found.
Chem. Eng., 2014, 48, 787.
10 S. S. Moganty, S. Srivastava, Y. Lu, J. L. Scaefer, S. A. Rizvi and
L. A. Archer, Chem. Mater. 2012, 24, 1386.
11 M. Zhang, J. Chen, H. Qiu, A. K. Mallik, M. Tkafuji and H.
Ihara, RSC Adv., 2014, 4, 34654.
12 A. Šurca Vuk, V. Jovanovski, A. Pollet-Villard, I. Jerman and B.
Orel, Sol. Energ. Mater. Sol. Cells, 2008, 92, 126.
13 S. Takamatsu, R. Matsuno, S. Kumagai, Y. Kokubo, K.
Hashimoto, H. Yoshikawa, A. Takahara and H. Otsuka, US
20140300247, 2014.
14 For general aspects of click chemistry, see: (a) H. C. Kolb, M.
G. Finn and K. B. Sharpless, Angew. Chem. Int. Ed., 2001, 40,
2004 and references therein.
15 R. A. O’Brien, A. Mirjafari, K. M. Mattson, S. M. Murray, N.
Mobarrez, E. A. Salter, A. Wierzbicki, J. H. Davis Jr. and K. N.
West, J. Phys. Chem. B, 2014, 118, 10232.
16 (a) J. L. Anderson, R. Ding, A. Ellern and D. W. Armstrong, J.
Am. Chem. Soc., 2005, 127, 593; (b) A. Mirjafari, R. A.
O’Brien, S. M. Murray, K. M. Mattson, N. Mobarrez, K. N.
West and J. H. Davis Jr., ACS Symp. Ser., 2012, 9, 199.
17 (a) B. S. Lee, Y. S. Chi, J. K. Lee, I. S. Choi, C. E. Song, S. K.
Namgoong and S. Lee, J. Am. Chem. Soc., 2004, 126, 480; (b)
34 (a) Y. Jun, J. Choi and J. Cheon, Chem. Commun., 2007, 1203;
(b) J. Dupont and J. D. Scholten, Chem. Soc. Rev., 2010, 39,
1780; (c) Z. Ma, J. Yu and S. Dai, Adv. Mater., 2010, 22, 261.
35 M. H. Valkenberg, C. deCastro and W. H. Holderich, Green
Chem. 2002, , 88.
4
36 (a) D. L. Graham, H. A. Ferreira and P. P. Freitas, Trends
Biotechnol., 2004, 22, 455; (b) T. Neuberger, B. Schopf, H.
Hofmann, M. Hofmann and B. von Rechenberg, J. Magn.
Magn. Mater., 2005, 293, 483.
37 C. Chen, H. Lai, C. Lin, J. Wang and R. Chiang, Nanoscale.
Res. Lett., 2009, 4, 1343.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 9
Please do not adjust margins

Green Chemistry
Page 10 of 10
View Article Online
DOI: 10.1039/C5GC01930C
162x76mm (300 x 300 DPI)