Dendritic ionic liquids based on imidazolium-modified poly(aryl ether) dendrimers

Article abstract of DOI:10.1002/asia.201402960

A series of dendritic ionic liquids (DILs) based on imidazoliummodified poly(aryl ether) dendrimers IL-Br-Gn (n=0-3) were synthesized by a modified convergent approach and "click" chemistry. The resulting DILs exhibited high thermal resistance with decomposition temperatures up to 270 °C and low glass transition temperatures in the range of approximately -5-0 °C. All IL-Br-Gn were found to be miscible with water at any ratio and could encapsulate hydrophobic molecules. The reversible phase transfer of the DILs between the aqueous and organic phases was accomplished by simple anion exchange between the hydrophilic Br^- anion and the hydrophobic bis(trifluoromethylsulfonyl)amide anion (NTf₂^-). IL-Br-Gn could be used as transporters to shuttle hydrophobic molecules between the organic and aqueous phases efficiently. The present work provides a new kind of transporting materials with potential applications in substance separation, drug delivery, and biomolecule transport.

Full text of DOI:10.1002/asia.201402960

FULL PAPER
DOI: 10.1002/asia.201402960
Dendritic Ionic Liquids Based on Imidazolium-Modified Poly(aryl ether)
Dendrimers
Tianyi Qin,[a] Xuying Li,[a] Jinping Chen,*[a] Yi Zeng,[a] Tianjun Yu,[a]
Guoqiang Yang,*[b] and Yi Li*[a]
Abstract: A series of dendritic ionic
liquids (DILs) based on imidazolium-
modified poly(aryl ether) dendrimers
IL-Br-Gn (n=0–3) were synthesized
by a modified convergent approach
and “click” chemistry. The resulting
DILs exhibited high thermal resistance
with decomposition temperatures up to
2708C and low glass transition temper-
atures in the range of approximately
À5–08C. All IL-Br-Gn were found to
be miscible with water at any ratio and
could encapsulate hydrophobic mole-
cules. The reversible phase transfer of
the DILs between the aqueous and or-
ganic phases was accomplished by
simple anion exchange between the hy-
drophilic BrÀ anion and the hydropho-
bic bis(trifluoromethylsulfonyl)amide
anion (NTf2 ). IL-Br-Gn could be used
as transporters to shuttle hydrophobic
molecules between the organic and
aqueous phases efficiently. The present
work provides a new kind of transport-
ing materials with potential applica-
tions in substance separation, drug de-
livery, and biomolecule transport.
À
Keywords: dendrimers
·
ion
exchange · ionic liquids · phase
transfer · transporters
Introduction
conductivity, low toxicity, and a wide electrochemical
window, in addition to their potential for facile construction
of highly multifunctional systems. Poly(ionic liquid)s (PILs),
that is, polymerized ionic liquids, combining the properties
of ionic liquids and the superior processability afforded by
the polymer nature,[4] have been widely used in the fields of
catalysis,[5] synthesis,[6] gas adsorption and separation,[7] elec-
trochemistry,[8] and thermoresponsive materials.[9] Replacing
polymers with special macromolecules such as hyper-
branched polymers or dendrimers in PILs affords hyper-
branched or dendritic ionic liquids (BILs or DILs). Various
applications of BILs or DILs can be envisioned, such as
sorbents, liquid separation media, catalyst scaffolds, dispers-
ing agents, and transporters for shuttling functional materi-
als. Recently, Ludwigs and co-workers reported a series of
ionically functionalized branched polythiophenes with car-
boxylic acid or methylimidazolium end groups. The conju-
gated BILs exhibit characteristics of both conjugated poly-
mers and polyelectrolytes, which implies potential applica-
tions in dye-sensitized solar cells and electrochemical devi-
ces.[10] Mꢀlhaupt and co-workers developed new families of
BILs with onion-like topology, containing a core of hyper-
branched poly(1,3-diether), a polar inner imidazolium cation
shell, and an nonpolar outer n-alkyl shell. BILs are very ef-
fective phase-transfer systems, and they enable extraction of
water-soluble dyes and nanomaterials from an aqueous
phase.[11] Up to now, only a few examples have dealt with
DILs.[12] Our research group has developed carboxylate- and
tetraethylene glycol terminated poly(aryl ether) dendrimers
that can act as microreactors to control pathways of photo-
chemical reactions.[13] In continuation of this research, we
anticipate that the construction of imidazolium-terminated
poly(aryl ether) dendrimers may provide macromolecules
Dendrimers are regularly and hierarchically branched mac-
romolecules with excellent monodispersity, globular shape,
interior pockets, and numbers of surface functionality.[1] The
specific properties of dendrimers endow them with great po-
tential in miscellaneous applications such as catalysis, supra-
molecular chemistry, and drug delivery.[2] Furthermore, the
stepwise synthesis of dendrimers allows for a large degree of
control over the molecular architecture. Desired functional
groups can be accurately located at the core, focal point, pe-
riphery, or even at each branching point of the dendritic
structure.[3]
Ionic liquids (ILs) nowadays have attracted rapidly in-
creasing interest as a result of their unique properties, which
include negligible vapor pressure, low flammability, ionic
[a] T. Qin, X. Li, Dr. J. Chen, Dr. Y. Zeng, Dr. T. Yu, Prof. Dr. Y. Li
Key Laboratory of Photochemical Conversion and Optoelectronic
Materials
Technical Institute of Physics and Chemistry
Chinese Academy of Sciences
Beijing, 100190 (China)
Fax : (+86)10-8254-3518
E-mail: yili@mail.ipc.ac.cn
chenjp@mail.ipc.ac.cn
[b] Prof. Dr. G. Yang
Beijing National Laboratory for Molecular Sciences (BNLMS)
Key laboratory of Photochemistry, Institute of Chemistry
Chinese Academy of Sciences
Beijing, 100190 (China)
Fax : (+86)10-8261-7315
E-mail: gqyang@iccas.ac.cn
Supporting Information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201402960.
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with the merits of both dendrimers and ILs, which will rein-
force applications of dendritic ionic liquids in materials
chemistry.
formed in the presence of potassium carbonate and 18-
crown-6 in dry acetone, which gave desired compound 3 in
81% yield. Reduction of 3 with LiAlH4, which was followed
by bromination with PPh3/CBr4 afforded A-G0-Br (5) in
97% yield. Reaction of 5 with 3,5-dihydroxybenzyl alcohol
(6) gave the first-generation dendritic alcohol A-G1-OH (7)
in 91% yield after purification by column chromatography.
By repeating bromination and reaction with 6, first- to
third-generation dendrons 8, 10, and 12 were prepared with
6, 12, and 24 alkynyl groups at their periphery, respectively.
Details of the synthesis and characterization of the com-
pounds are described in the Experimental Section. All of
Herein, we attempt to take advantage of the dendritic ar-
chitecture with numerous peripheral groups that could
densely incorporate ionic liquid moieties to obtain DILs.
Numerous ionic groups at the periphery will greatly affect
the physical properties of the dendrimers, which should
result in lower glass transition temperatures (Tg), reversible
phase-transfer properties, and efficient transporting capabili-
ties for hydrophobic molecules.
1
the compounds were characterized by H NMR spectrosco-
Results and Discussion
py and mass spectrometry (MALDI-TOF or ESI).
The obtained dendrons were attached to a polyfunctional
1,1,1-tris(4’-hydroxyphenyl)ethane (13) core to build acety-
The design of DILs is based on the following ideas: One,
the hydrophobic poly(aryl ether) dendritic backbone is
adopted owing to its controllable synthetic method[3] and ca-
pability of encapsulating hydrophobic molecules;[1a,2a,13] two,
alkynyl end groups are engineered to preinstall in the pe-
riphery of the precursor ready for the following “click” reac-
tion; three, the efficient “click” reaction between azides and
terminal alkynes is selected to attach the imidazolium
groups to the periphery of the dendrimers completely.
The alkynyl-terminated poly(aryl ether) dendrons (A-Gn-
Br, n=1–3) were synthesized by the adapted convergent
synthetic methodology[14] shown in Scheme 1. The reaction
of methyl gallate (1) with propargyl bromide (2) was per-
lene-terminated trisACTHNUGRTNE(NUG phenolic)-cored dendrimers ([A-Gn]3-
C) by using the same chemistry in constructing the den-
drons, and the synthesis of the third generation is shown in
Scheme 2. An acetone solution of dendron A-G3-Br (12,
3.2 equiv.) was heated at reflux with core molecule 13
(1.0 equiv.) in the presence of potassium carbonate and 18-
crown-6. The desired acetylene-terminated trisACTHNUTRGNE(UNG phenolic)-
cored dendrimer [A-G3]3-C (17) was obtained in 57% yield
after simple purification by column chromatography. A simi-
lar reaction was performed to produce [A-Gn]3-C (n=0–2)
by using the corresponding generation of dendrons with
yields of 84, 80, and 77% for generations 0, 1, and 2, respec-
Scheme 1. Synthesis of alkynyl-terminated poly(aryl ether) dendrons. Reagents and conditions: a) acetone, K2CO3, 18-crown-6, reflux, 24 h; b) THF,
LiAlH4, RT, 3 h; c) THF, CBr4, PPh3, RT, 10 min.
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Scheme 2. Synthetic route to dendrimer 17 and IL-terminated trisACTHUNGTRENNG(U phenolic)-cored dendrimer IL-Br-G3 (26) with 72 imidazolium end groups.
tively. The copper(I)-catalyzed Huisgen 1,3-dipolar cycload-
dition between azides and terminal alkynes is one of the
most used “click” reactions, and it has many advantages
such as high selectivity, functional group tolerance, mild re-
action conditions, and quantitative yield.[15] Astrucꢂs group
functionalized the periphery of dendrimers by using the
“click” reaction.[16] In the present case, the azide-substituted
molecule [N-C-Min]+BrÀ (22, Min=1-methylimidazolium)
was used as a coupling molecule to “click” with the acety-
C635H864Br19N180O57: 789.6 [MÀ17BrÀ]17+) in the mass spec-
tra.
The thermal properties of all the dendritic ionic liquids
(IL-Br-Gn, n=0–3) were measured by thermogravimetric
analysis (TGA) and differential scanning calorimetry (DSC)
as shown in Figure 1. IL-Br-Gn (n=0–3) exhibit excellent
thermal resistance with decomposition temperatures (Td) up
to 2708C and major weight changes at 270–3608C (70–
75%), which approximate to the weight percentage of satu-
rated hydrocarbons formed by the elements in the mole-
cules. Therefore, we speculate that the major weight loss
corresponds to the decomposition of the molecules with res-
idue of carbon. Similar thermal stability observed for differ-
ent generations of IL-Br-Gn (n=0–3) indicates little effect
of the number of imidazolium groups on the thermal stabili-
ty of the dendritic ionic liquids. A small weight loss below
1008C can be ascribed to the trace amount of water within
IL-Br-Gn (n=0–3), and the water contents were estimated
to be 1.1, 1.6, 1.9, and 2.0 wt% for generations 0, 1, 2, and 3,
respectively. DSC analysis demonstrates that all four genera-
tions of IL-Br-Gn show similar glass transition temperatures
in the range of approximately À5–08C. Evidently, peripheral
functionalization with imidazolium groups decreases the
value of Tg greatly in comparison with the corresponding
acetylene-terminated dendrimers.[17] Generally, it is accepted
that the absence of polar groups or ion pairs will minimize
intermolecular interactions, which will thus lower Tg. In our
DILs, the flexible poly(aryl ether) dendritic backbone tends
to form a globular shape because of electrostatic repulsion
of the peripheral imidazolium cation groups, which shields
lene-terminated trisACHTUNGTRENNUNG(phenolic)-cored dendrimers to prepare
imidazolium-terminated ones. The synthetic route for the
synthesis of the third-generation DIL, IL-Br-G3 (26), is
shown in Scheme 2 as a representative example. Click reac-
tion of 17 with 22 afforded desired dendritic ionic liquid 26
1
in 68% yield. The H NMR spectrum of 26 exhibits clearly
the structure with two singlets at d=8.71 and 7.38 ppm for
1
the imidazolium protons. Compared with the H NMR spec-
trum of 17, the disappearance of the acetylene protons at
d=2.46 ppm further confirms the occurrence of the “click”
reaction and the formation of the ionic-liquid-terminated
structure. With a similar procedure, the lower generation
DILs of IL-Br-Gn (n=0–2; 23, 24, 25) were prepared and
1
characterized by H NMR spectroscopy. We failed to obtain
the molecular ion peak of IL-Br-G3 by MS, because of the
limitation of the equipment for high molecular weights
(calcd for C1271H1728Br72N360: 29588.2 [M]+). IL-Br-G0 (23),
IL-Br-G1 (24), and IL-Br-G2 (25) show ion peaks with mul-
ticharges at m/z=2928.6 (calcd for C158H208N45O12: 2927.7
[MÀ9BrÀÀ8H+]+), 5924.8 (calcd for C317H415N90O27: 5914.4
[MÀ18BrÀÀ17H+]+),
and
792.6
(calcd
for
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The solubility of imidazolium-containing materials can be
easily modulated by exchanging the corresponding counter-
ions.[18] The introduction of imidazolium cations to the pe-
riphery of the dendritic structures should also result in
phase-transferable DILs. The phase-transfer process of DILs
was achieved through sequential anion exchanges (genera-
tion two as a representative example is shown in Scheme 3).
Two molar equivalents of lithium bis(trifluoromethylsulfony-
l)amide (LiNTf2) based on the terminal groups of DIL was
dissolved in water (ꢀ50 mgmLÀ1), and the solution was
added to an aqueous solution of IL-Br-G2 dropwise. A
white precipitate formed immediately owing to substitution
of the hydrophilic anion (BrÀ) by the hydrophobic anion
À
(NTf2 ) within the DIL. The resulting hydrophobic IL-NTf2-
G2 was isolated and readily redissolved in polar aprotic sol-
vents such as acetonitrile (MeCN), dimethylformamide
(DMF), tetrahydrofuran (THF), and N-methylpyrrolidone
(NMP). Furthermore, IL-NTf2-G2 dissolved in organic sol-
vents was transferred to the aqueous phase in a similar way
by the addition of appropriate salts containing hydrophilic
anions such as tetrabutylammonium bromide (TBAB).
Thereby, reversible phase transfer of second-generation
DILs between the aqueous and organic phases was accom-
plished by simple anion-exchange treatments. The same re-
versible phase-transfer phenomenon was observed for other
generations of DILs.
Figure 1. a) TGA and b) DSC curves of the dendritic ionic liquids. Heat-
The reversible phase transfer of DILs caused by anion ex-
change was further confirmed by validation of the structures
of the hydrophobic IL-NTf2-Gn (n=0–3). IL-NTf2-Gn (n=
0–3) were full characterized by NMR and IR spectroscopy
and MALDI-TOF or ESI mass spectrometry (Supporting
ing rate: 108CminÀ1, under a nitrogen atmosphere.
the coulombic interactions among the dendritic molecules
and, consequently, decreases Tg. Additionally, the alkyl link-
age between the dendritic backbone and the imidazolium
groups may facilitate the motion of the dendritic building
blocks at relatively lower temperatures.
1
Information). The H NMR, 13C NMR, and ESI mass spec-
tra of IL-NTf2-G2 in CD3CN are shown in Figure 2 as an ex-
ample to illustrate the anion exchange of the DILs. The
Scheme 3. Phase-transfer process for a second generation DIL between the aqueous and organic phases by anion exchange.
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Figure 2. NMR and mass spectra of IL-NTf2-G2. a) 1H NMR and b) 13C NMR spectra in CD3CN; c) ESI-TOF mass spectrum.
1H NMR spectrum gave more specific information than that
of IL-Br-G2 in D2O; it exhibits clearly the structure with
a singlet at d=8.40 ppm and a doublet at d=7.32 ppm for
the imidazolium protons (Figure 2a). Compared with the
13C NMR spectrum of IL-Br-G2, a singlet at d=119.3 ppm
can be clearly observed in the spectrum of IL-NTf2-G2 (Fig-
was chosen as a probe to detect the interior of IL-Br-Gn
(n=0–3). The UV/Vis absorption spectra of Nile Red in
water and aqueous solutions of IL-Br-Gn were measured
(Figure S40). The solubility of Nile Red is very low in water
and is evidently enhanced in the presence of IL-Br-Gn (n=
0–3). According to the absorption data, the solubility of Nile
Red is approximately 1.7, 17, 23, and 73 times higher for
generations 0, 1, 2, and 3 DILs, respectively. The average
numbers of Nile Red molecules encapsulated within each
IL-Br-Gn molecule were estimated to be 0.03, 0.3, 0.4, and
1.4 for generations 0, 1, 2, and 3, respectively; this is consis-
tent with other water-soluble poly(aryl ether) dendrimer-
s.[13a,21] These results indicate that IL-Br-Gn are capable of
encapsulating hydrophobic molecules, and the encapsulation
ability increases with the generation. There is a steep in-
crease in the encapsulation ability of the third-generation
DIL relative to that of the second-generation DIL. There-
fore, we infer that IL-Br-G3 has better transporting ability.
The ability of IL-Br-G3 to serve as a transporter was fur-
ther estimated by using Nile Red as a model of hydrophobic
substance. A IL-Br-G3/water mixture (33 wt%) was used as
the phase-transfer agent for Nile Red because of the high
viscosity of IL-Br-G3 at room temperature. The process for
transporting Nile Red from the hexane organic phase into
the aqueous phase is shown in Figure 3. A n-hexane solution
of Nile Red was added to the IL-Br-G3/water mixture as
a top, yellow organic phase (Figure 3a). After shaking, the
upper organic layer was almost colorless (Figure 3b); this
indicated that Nile Red was transferred completely from the
n-hexane phase to the aqueous phase (IL-Br-G3/water mix-
ture) immediately. Back transportation of Nile Red from
the aqueous phase to another organic phase was performed
À
ure 2b), which is assigned to the carbon atom of NTf2 ac-
cording to the literature.[19] Multicharged ion peaks of IL-
NTf2-G2 are observed at m/z=2867.5, 2473.0, 2166.9, and
À
À
À
1921.8 for [MÀ7NTf2 ]7+, [MÀ8NTf2 ]8+, [MÀ9NTf2 ]9+
,
À
and [MÀ10NTf2 ]10+, respectively, in its ESI-TOF mass
spectrum (Figure 2c). Similar to IL-Br-G3, the molecular
ion peak of IL-NTf2-G3 was not observed in its MALDI-
TOF or ESI-TOF mass spectrum as a result of equipment
limitations for high molecular weights. All the characteriza-
tions unambiguously confirm the formation of IL-NTf2-Gn
(n=0–3); this indicates that anion exchange is the cause of
the reversible phase transfer of DILs. Notably, the values of
Tg for IL-NTf2-Gn are almost the same as those of IL-Br-
Gn, and thus, the anions have little effect on the thermal
properties of the DILs (Figure S39, Supporting Informa-
tion).
Transporters of small organic molecules play a crucial role
in biological processes, drug delivery, and catalysis. Meijerꢂs
early work indicated that dendrimers could be used as a box
to encapsulate and release different dyes stepwise.[20] The
novel DILs, IL-Br-Gn (n=0–3), which contain an inner hy-
drophobic poly(aryl ether) branch unit and a hydrophilic
outer imidazolium shell, may have the capability to serve as
effective transporters of small organic molecules. Prior to
detecting the capability of DILs as transporters, understand-
ing the encapsulation ability of DILs is essential. Nile Red
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Experimental Section
General methods
All reagents were obtained from Acros, TCI, or Beijing Chemicals and
were used without further purification unless otherwise noted. Tetrahy-
drofuran (THF) and acetone were dried with sodium and anhydrous po-
tassium carbonate (K2CO3), respectively, and were distilled under a N2
atmosphere. 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were
obtained by using a Bruker Avance P-400 spectrometer with tetrame-
thylsilane as the internal standard. MS spectra were measured by using
a Bruker BIFLEX III spectrometer (MALDI-TOF) or a Waters LCT
Premier XE spectrometer (ESI-TOF). Absorption spectra were run with
a Shimadzu UV-1601PC spectrometer. Chromatographic purifications
were performed by column chromatography on silica gel (200–300 mesh).
IR spectra were measured as KBr pellets by using a Varian Excalibur
3100 spectrometer. The glass transition temperature (Tg) was measured
with a TA Instruments Q2000 modulated differential scanning calorime-
ter (DSC) at a heat/cool rate of 108CminÀ1 under a N2 atmosphere for
heat/cool/heat cycles. TGA was performed on a TA Instruments Q600 at
a heating rate of 108CminÀ1 under a N2 atmosphere.
Figure 3. Photograph of transporting Nile Red between different phases:
a) before shaking (the upper layer: Nile Red/hexane solution, bottom
layer: DILs/H2O mixture); b) after shaking; c) back transport to EtOAc
(the upper layer: Nile Red/EtOAc solution, bottom layer: DILs/H2O
mixture); d) the second time for back transport with EtOAc. The concen-
trations of Nile Red and IL-Br-G3 were 1.0ꢃ10À4 m and 33 wt%, respec-
tively.
by adding ethyl acetate (same volume of n-hexane) to the
IL-Br-G3/water mixture encapsulating Nile Red. Nile Red
was completely back transferred to the ethyl acetate organic
phase after shaking (Figure 3c), which was validated by the
almost colorless organic layer of the second back-transport-
ing experiment (Figure 3d). The phase transfer of Nile Red
from the organic phase to the aqueous phase and then to an-
other organic phase in the presence of IL-Br-G3 indicates
that IL-Br-G3 is an effective phase transporter (color photo-
graph shown in Figure S41). More importantly, the IL-Br-
G3 phase-transporting agent exhibits excellent cyclability
and can be reused without any loss after the back-transport-
ing experiment. Notably, the brown-orange color of IL-Br-
G3 itself is caused by oxidation and decomposition of the
N-heterocycles during heating or long-term storage,[5e] al-
Syntheses
3: Potassium carbonate (37.5 g, 271.5 mmol) and 18-crown-6 (0.05 g,
0.2 mmol) were added to a solution of methyl gallate (1; 10 g, 54.3 mmol)
and propargyl bromide (2; 28.4 g, 238.9 mmol) in acetone (60 mL). The
mixture was heated at reflux under an atmosphere of nitrogen for 24 h.
The mixture was allowed to cool and was then evaporated to dryness
under reduced pressure. The residue was partitioned between H2O and
CH2Cl2, and the aqueous layer was extracted with CH2Cl2 (3ꢃ50 mL).
The combined organic layer was then dried and evaporated to dryness.
The crude product was purified by recrystallization (methanol) to give 3
as
a
white solid (13.1 g, 81%). M.p. 84–858C; 1H NMR (400 MHz,
CDCl3): d=7.47 (s, 2H, Ar), 4.82 (d, J=2.4 Hz, 2H, p-CH2), 4.80 (d, J=
2.4 Hz, 4H, m-CH2), 3.91 (s, 3H, CH3), 2.53 (t, J=2.4 Hz, 2H, m-Cꢁ
CH), 2.45 ppm (t, J=2.4 Hz, 1H, p-CꢁCH).
4: Lithium aluminum hydride (4.1 g, 107.3 mmol) was added to anhy-
drous THF (250 mL) in small portions, and a solution of 3 (12.8 g,
42.9 mmol) in anhydrous THF (50 mL) was added dropwise at 08C. The
mixture was then stirred at ambient temperature for 3 h. Subsequently,
the reaction was quenched with an excess amount of H2O (200 mL) and
was extracted with CH2Cl2 (3ꢃ100 mL). The combined organic layer was
dried with anhydrous MgSO4. After removal of the solvent under re-
duced pressure, the residue was purified by recrystallization (methanol)
1
though its H NMR spectrum exhibits no change.
Conclusions
to produce
a
white solid (10.9 g, 94.0%). M.p. 95–978C; 1H NMR
In summary, we accomplished the synthesis of a series of
dendritic ionic liquids (DILs) based on imidazolium-modi-
fied poly(aryl ether) dendrimers by a modified convergent
approach and “click” chemistry. The ionic end groups at-
tached to the periphery of the dendritic structures had
a major impact on the physical properties of the DILs, and
high thermal resistance and low glass transition tempera-
tures were obtained. The DILs were miscible with water at
any ratio, and the reversible phase transfer of the DILs be-
tween the aqueous and organic phases was achieved by
simple anion exchange between the hydrophilic anion (BrÀ)
(400 MHz, CDCl3): d=6.79 (s, 2H, Ar), 4.77 (d, J=2.4 Hz, 4H, m-CH2),
4.73 (d, J=2.4 Hz, 2H, p-CH2), 4.66 (s, 2H, ArCH2O), 2.51 (t, J=2.4 Hz,
2H, m-CꢁCH), 2.45 ppm (t, J=2.4 Hz, 1H, p-CꢁCH).
General procedure for the bromination
Triphenylphosphine (1.5 equiv.) was added to a mixture of dendritic
benzyl alcohol (1.00 equiv.) and carbon tetrabromide (1.5 equiv.) in a min-
imum amount of dry THF required to dissolve the above reagents. The
mixture was stirred under an atmosphere of nitrogen for 15 min. For the
second and third generations, larger excess amounts of CBr and PPh3
were required to force the reaction to completion. The reaction was
quenched with H2O, and the mixture was extracted with CH2Cl2 (3ꢃ);
the combined extract was dried and evaporated to dryness. The residue
was purified by column chromatography on silica gel to afford the de-
sired product.
À
and the hydrophobic anion (NTf2 ). The DILs showed the
ability to serve as transporters to transfer hydrophobic sub-
stances efficiently between the organic and aqueous phases,
and they could be reused without any loss; this is in accord-
ance with the concept of “green chemistry”. This work pro-
vides a new kind of transporting materials with potential ap-
plications in substance separation, drug delivery, and bio-
molecule transport.
General procedure for the synthesis of dendritic benzyl alcohols
A mixture of the appropriate dendritic benzyl bromide (2.1 equiv.), 3,5-
dihydroxybenzyl alcohol (6, 1.0 equiv.), dry potassium carbonate
(2.50 equiv.), and 18-crown-6 (0.2 equiv.) in dry acetone was heated at
reflux and was stirred under an atmosphere of nitrogen for 24 h. The
mixture was allowed to cool and was evaporated to dryness under re-
duced pressure. The residue was partitioned between H2O and CH2Cl2.
The combined organic layer was then dried and evaporated to dryness.
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The residue was purified by column chromatography on silica gel to
afford the desired product.
at reflux and stirred under an atmosphere of nitrogen for 48 h. The mix-
ture was allowed to cool and was evaporated to dryness under reduced
pressure. The residue was partitioned between H2O and CH2Cl2. The
combined organic layer was then dried and evaporated to dryness. The
residue was purified by column chromatography on silica gel to afford
the desired product.
A-G0-Br (5): Prepared by the reaction of alcohol 4 (2.4 g, 8.9 mmol),
carbon tetrabromide (4.4 g, 13.3 mmol), and triphenylphosphine (3.5 g,
13.3 mmol) upon stirring at ambient temperature for 10 min according to
the general procedure. Purification by column chromatography on silica
gel (CH2Cl2/petroleum ether=1:1) afforded 5 as a white solid (2.9 g,
97%). M.p. 64–658C; 1H NMR (400 MHz, CDCl3): d=6.80 (s, 2H, o-
Ar), 4.77 (d, J=2.4 Hz, 4H, m-CH2), 4.73 (d, J=2.4 Hz, 2H, p-CH2),
4.45 (s, 2H, CH2Br), 2.53 (t, J=2.4 Hz, 2H, m-CꢁCH), 2.46 ppm (t, J=
2.4 Hz, 1H, p-CꢁCH).
A-G1-OH (7): Prepared from 3,5-dihydroxybenzyl alcohol (6) and bro-
mide 5 according to the general procedure. Purification by column chro-
matography on silica gel (CH2Cl2/EtOAc=20:1) afforded 7 as a white
solid (91%). M.p. 104–1068C. 1H NMR (400 MHz, CDCl3): d=6.83 (s,
4H, o-Ar), 6.62 (s, 2H, o-Ar), 6.53 (s, 1H, Ar), 4.98 (s, 4H, ArCH2O),
4.76 (d, J=2.1 Hz, 8H, m-CH2CꢁC), 4.73 (d, J=2.3 Hz, 4H, p-CH2Cꢁ
C), 4.63 (s, 2H, CH2OH), 2.49 (s, 4H, m-CꢁCH), 2.46 ppm (s, 2H, p-Cꢁ
CH).
AHCTUNTGREG[NNUN A-G0]3-C (14): Prepared from 1,1,1-tris(4-hydroxyphenyl)ethane (13)
and propargyl bromide 5 (3.3 equiv.) according to the general procedure
for alkylation with potassium carbonate and 18-crown-6 in acetone. The
crude product was purified by column chromatography (CH2Cl2/EtOAc=
100:0 to 20:1) to give 14 as
a
pale yellow glass (84%). 1H NMR
(400 MHz, CDCl3): d=7.01–6.99 (d, J=8.8 Hz, 6H, o-Ph), 6.87–6.85 (d,
J=8.9 Hz, 6H, m-Ph), 6.83 (s, 6H, o-Ar), 4.98 (s, 6H, ArCH2O), 4.76 (d,
J=2.4 Hz, 12H, m-CH2CꢁC), 4.73 (d, J=2.4 Hz, 6H, p-CH2CꢁC),
2.47–2.46 (m, 9H, CꢁCH), 2.11 ppm (s, 3H, CH3C); MS (MALDI-
TOF): m/z: calcd for C68H54O12Na: 1085.4 [M+Na+]+; found: 1085.5.
AHCTUNTGREG[NNUN A-G1]3-C (15): Prepared from 1,1,1-tris(4-hydroxyphenyl)ethane (13)
and bromide 8 (3.3 equiv.) according to the general procedure. The crude
product was purified by column chromatography (CH2Cl2/EtOAc=100:0
to 20:1) to give 15 as a colorless glass (80%). 1H NMR (400 MHz,
CDCl3): d=7.01–6.99 (d, J=8.8 Hz, 6H, o-Ph), 6.86 (s, 6H, m-Ph), 6.83
(s, 12H, o-Ar), 6.68 (d, J=1.9 Hz, 6H, o-Ar), 6.55 (s, 3H, p-Ar), 4.98 (s,
12H, ArCH2O), 4.96 (s, 6H, ArCH2O), 4.76–4.73 (m, 36H, CH2CꢁC),
2.48–2.45 (m, 18H, CꢁCH), 2.11 ppm (s, 3H, CH3C); MS (MALDI-
TOF): m/z: calcd for C137H108O27Na: 2207.7 [M+Na+]+; found: 2208.1.
A-G1-Br (8): Prepared from benzyl alcohol 7 according to the general
procedure for bromination. Purification by column chromatography
(CH2Cl2) gave bromide 8 as a white solid (82%). M.p. 115–1168C.
1H NMR (400 MHz, CDCl3): d=6.83 (s, 4H, o-Ar), 6.64 (d, J=2.2 Hz,
2H, o-Ar), 6.52 (s, 1H, p-Ar), 4.98 (s, 4H, ArCH2O), 4.75 (s, 8H, m-
CH2CꢁC), 4.73 (s, 4H, p-CH2CꢁC), 4.41 (s, 2H, CH2Br), 2.49 (s, 4H,
m-CꢁCH), 2.46 (s, 2H, p-CꢁCH).
AHCTUNTGREG[NNUN A-G2]3-C (16): Prepared from 1,1,1-tris(4-hydroxyphenyl)ethane (13)
and bromide 10 (3.3 equiv.) according to the general procedure for alky-
lation with potassium carbonate and 18-crown-6 in acetone. The crude
product was purified by column chromatography (CH2Cl2/EtOAc=20:1)
to give 16 as a colorless glass (77%). 1H NMR (400 MHz, CDCl3): d=
7.00–6.98 (d, J=8.0 Hz, 6H, o-Ph), 6.86 (d, J=8.6 Hz, 6H, m-Ph), 6.84–
6.81 (m, 24H, o-Ar), 6.66 (s, 18H, o-Ar and p-Ar), 6.54–6.52 (d, J=
6.0 Hz, 9H, o-Ar and p-Ar), 4.98–4.94 (m, 42H, ArCH2O), 4.76–4.71 (m,
72H, CH2CꢁC), 2.46–2.44 (d, J=8.2 Hz, 36H, CꢁCH), 2.09 ppm (s,
3H, CH3C); MS (MALDI-TOF): m/z: calcd for C275H216O57Na: 4452.4
[M+Na+]+; found: 4448.0.
A-G2-OH (9): Prepared from 3,5-dihydroxybenzyl alcohol (6) and bro-
mide 8 (2.1 equiv.) according to the general procedure for alkylation with
potassium carbonate and 18-crown-6 in acetone. The crude product was
purified by column chromatography (CH2Cl2/EtOAc=20:1) to give alco-
hol 9 as a colorless glass (90%). 1H NMR (400 MHz, CDCl3): d=6.82 (s,
8H, o-Ar), 6.65 (d, J=2.0 Hz, 4H, o-Ar), 6.59–6.52 (m, 4H, o-Ar and p-
Ar), 6.46 (s, 1H, p-Ar), 4.98 (m, 12H, ArCH2O), 4.74 (m, 24H, CH2Cꢁ
C), 4.62 (s, 2H, CH2OH), 2.47 ppm (m, 12H, CꢁCH); MS (MALDI-
TOF): m/z: calcd for C85H68O19Na: 1415.4 [M+Na+]+; found: 1415.5.
A-G2-Br (10): Prepared from alcohol 9 according to the general proce-
dure with CBr4 (2.0 equiv.) and PPh3 in anhydrous THF. The crude prod-
uct was purified by column chromatography (CH2Cl2/EtOAc=100:0 to
AHCTUNTGREG[NNUN A-G3]3-C (17): Prepared from 1,1,1-tris(4-hydroxyphenyl)ethane (13)
and bromide 12 (3.2 equiv.) according to the general procedure. The
crude product was purified by column chromatography (CH2Cl2/EtOAc=
10:1) to give 17 as a colorless glass (57%). 1H NMR (400 MHz, CDCl3):
d=6.98–6.96 (d, J=8.7 Hz, 6H, o-Ph), 6.83–6.73 (m, 54H, m-Ph and o-
Ar), 6.66–6.58 (m, 42H, o-Ar), 6.53–6.51 (m, 21H, p-Ar), 4.96–4.92 (m,
90H, ArCH2O), 4.73–4.70 (m, 144H, CH2CꢁC), 2.45–2.43 (m, 72H, Cꢁ
CH), 2.17 ppm (s, 3H, CH3C); MS (MALDI-TOF): m/z: calcd for
C551H432O117Na: 8941.8 [M+Na+]+; found: 8940.1.
1
20:1) to give bromide 10 as a white solid (78%). M.p. 93–958C; H NMR
(400 MHz, CDCl3): d=6.84 (s, 8H, o-Ar), 6.68 (d, J=1.5 Hz, 4H, o-Ar),
6.64 (d, J=1.6 Hz, 2H, p-Ar), 6.57 (s, 2H, o-Ar), 6.52 (s, 1H, p-Ar), 4.99
(m, 12H, ArCH2O), 4.76 (m, 24H, CH2CꢁC), 4.43 (s, 2H, CH2Br),
2.49 ppm (m, 12H, CꢁCH).
A-G3-OH (11): Prepared from 3,5-dihydroxybenzyl alcohol (6) and bro-
mide 10 (2.1 equiv.) according to the general procedure for alkylation
with potassium carbonate and 18-crown-6 in acetone. The crude product
was purified by column chromatography (CH2Cl2/EtOAc=20:1) to give
alcohol 11 as a colorless glass (69%). 1H NMR (400 MHz, CDCl3): d=
6.81 (s, 16H, o-Ar), 6.76 (s, 1H, p-Ar), 6.64–6.66 (m, 12H, o-Ar), 6.58 (s,
2H, o-Ar), 6.52–6.53 (m, 6H, p-Ar), 4.96 (s, 28H, ArCH2O), 4.73 (m,
48H, CH2CꢁC), 4.58 (s, 2H, CH2OH), 2.46 ppm (m, 24H, CꢁCH); MS
(MALDI-TOF): m/z: calcd for C177H140O39Na: 2911.9 [M+Na+]+; found:
2917.2.
1-Azido-6-bromohexane (20):
A solution of 1,6-dibromohexane (18;
18.8 g, 76.9 mmol) and sodium azide (19; 5 g, 76.9 mmol) in DMF
(20 mL) with H2O (5 mL) was stirred at 608C for 24 h. The aqueous
phase was extracted with CH2Cl2 (3ꢃ50 mL), dried with MgSO4, and
evaporated to dryness to give 20 as a pale yellow oil (9.6 g, 61%).
1H NMR (400 MHz, CDCl3): d=3.41 (t, J=6.7 Hz, 2H, CH2Br), 3.28 (t,
J=6.8 Hz, 2H, CH2N3), 1.84–1.91 (m, 2H, CH2CBr), 1.48–1.58 (m, 2H,
CH2CN3), 1.37–1.41 ppm [m, 4H C
ACHTUGNRTNE(NUNG CH2)2C].
AHCTUNGTRENNUNG
A-G3-Br (12): Prepared from alcohol 11 according to the general proce-
dure with CBr4 (2.5 equiv.) and PPh3 in anhydrous THF. The crude prod-
uct was purified by column chromatography (CH2Cl2/EtOAc=100:0 to
20:1) to give bromide 12 as a colorless glass (71%). 1H NMR (400 MHz,
CDCl3): d=6.81 (s, 16H, o-Ar), 6.76 (s, 1H, p-Ar), 6.64–6.66 (m, 12H, o-
Ar), 6.62 (d, J=2.0 Hz, 2H, o-Ar), 6.54 (s, 6H, p-Ar), 4.96 (s, 28H,
ArCH2O), 4.73 (m, 48H, CH2CꢁC), 4.38 (s, 2H, CH2Br), 2.46 ppm (m,
24H, CꢁCH).
22.3 mmol) and 1-methylimidazole (21; 2.2 g, 26.8 mmol) in toluene
(10 mL) was stirred at 608C for 24 h. The mixture was partitioned be-
tween toluene and oil. The oil was extracted with EtOAc (5ꢃ5 mL) and
evaporated to dryness to give 22 as a pale yellow viscous oil (6.0 g,
94%). 1H NMR (400 MHz, D2O): d=8.71 (s, 1H, NCHN in imidazole),
7.47 (s, 1H, imidazole), 7.43 (s, 1H, imidazole), 4.20 (t, J=7.1 Hz, 2H,
NCH2), 3.89 (s, 3H, NCH3), 3.31 (t, J=6.8 Hz, 2H, N3CH2), 1.94–1.83
(m, 2H, CH2 in hexyl), 1.64–1.54 (m, 2H, CH2 in hexyl), 1.46–1.27 ppm
(m, 4H, CH2 in hexyl).
General procedure for the synthesis of acetylene-terminated tris
cored dendrimers
ACHTUNGTRENUN(NG phenolic)-
General procedure for the click reaction
A mixture of the appropriate dendritic benzyl bromide (3.3 equiv.), 1,1,1-
tris(4-hydroxyphenyl)ethane (13, 1.0 equiv.), anhydrous potassium car-
bonate (5.0 equiv.), and 18-crown-6 (0.3 equiv.) in dry acetone was heated
A solution of sodium ascorbate (2.0 equiv.) and CuSO4·H2O (2.0 equiv.)
in H2O was added to a mixture of the appropriate acetylene-terminated
trisACTHNUTRGNE(NUG phenolic)-cored dendrimer (1.0 equiv.) and coupling molecule 22 (
Chem. Asian J. 2014, 9, 3641 – 3649
3647
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
Li et al.
ꢀ18–144 equiv.) in H2O/THF (v/v=1:1). The mixture was stirred at am-
bient temperature for 48 h. After removal of the organic solvents, the
crude product was further purified by repeated anion exchange to afford
the desired product.
CH2), 3.83–3.82 (d, J=4.8 Hz, 216H, NCH3), 1.66 (br, 288H, CH2 in
hexyl), 1.13 ppm (br, 288H, CH2 in hexyl); 13C NMR (100 MHz, D2O):
d=25.5, 25.7, 29.8, 30.0, 36.5, 49.8, 50.7, 58.8, 63.2, 70.2, 107.6, 122.7,
124.1, 125.5, 134.2, 136.2, 136.4, 136.7, 143.5, 144.4, 152.4, 160.3 ppm; IR
(KBr pellet): n˜max =3435, 3080, 2935, 2960, 1635, 1560, 1510, 1450, 1360,
1165, 835 cmÀ1; MS (MALDI-TOF): molecular ion peak could not be ob-
tained.
General procedure for the anion exchange
An aqueous solution of LiNTf2 (2.0 equiv. to BrÀ) was added dropwise to
an aqueous solution of IL-Br-Gn (1.0 equiv., crude product). The mixture
was stirred vigorously at ambient temperature for 2 h, and a white pre-
cipitate formed immediately. After filtration, the residue was washed
with H2O (3ꢃ) to afford the corresponding IL-NTf2-Gn. The IL-NTf2-Gn
was redissolved in MeCN and the anion was exchanged again with tetra-
butylammonium bromide (TBAB) to afford pure IL-Br-Gn.
IL-NTf2-G0 (27): Prepared from dendrimer IL-Br-G0 (23) according to
the general procedure for anion exchange to give 27 as a viscous gum
(89%). 1H NMR (400 MHz, CD3CN): d=8.39 (s, 9H, NCHN in imida-
zole), 7.88 (s, 6H, m-NCHC in triazole), 7.77 (s, 3H, p-NCHC in tria-
zole), 7.34–7.31 (d, J=9.5 Hz, 18H, NCHCHN in imidazole), 7.06–7.04
(d, J=8.7 Hz, 6H, o-Ar), 6.93 (s, 6H, o-Ph; 6H, m-Ar), 5.14 (s, 12H, m-
triazole-CH2), 5.02 (s, 6H, p-triazole-CH2), 4.98 (s, 6H, ArCH2O), 4.36–
4.27 (m, 18H, imidazole-CH2), 4.08–4.04 (t, J=7.3 Hz, 18H, triazole-
CH2), 3.80 (s, 27H, NCH3), 2.09 (s, 3H, CCH3), 1.88–1.74 (m, 36H, CH2
in hexyl), 1.29 ppm (s, 36H, CH2 in hexyl); 13C NMR (100 MHz,
CD3CN): d=26.1, 30.4, 37.0, 50.6, 63.9, 66.9, 70.9, 108.9, 119.6 (CF3SO),
122.7, 123.4, 124.8, 130.7, 134.7, 137.0, 138.3, 143.3, 153.5, 158.1 ppm; IR
(KBr pellet): n˜max =3155, 2945, 1629, 1605, 1352, 1193, 1055 cmÀ1; MS
(MALDI-TOF): m/z: calcd for C174H216F48N53O44S16: 5175.1 [MÀNTf2À]+;
found: 5176.9.
IL-Br-G0 (23): Acetylene-terminated dendrimer 14 (0.5 g, 0.47 mmol)
+
À
À À
and [N C Min] Br (22; 2.4 g, 8.47 mmol) were added a H2O/THF mix-
ture (1:1 v/v, 10 mL). Then, a solution of sodium ascorbate (0.1677 g,
0.85 mmol) and CuSO4·H2O (0.1057 g, 0.42 mmol) in H2O (5 mL) was
added. The mixture was stirred at ambient temperature for 48 h. After
evaporation of the organic solvent, the crude product was purified by the
general procedure for repeated anion exchange to give 23 as a pale
yellow viscous gum (1.4721 g, 86%). 1H NMR (400 MHz, D2O): d=8.70
(s, 9H, NCHN in imidazole), 7.95 (s, 6H, m-NCHC in triazole), 7.75 (s,
3H, p-NCHC in triazole), 7.41 (s, 18H, imidazole), 6.75 (br, 12H, o-Ar
and m-Ar), 6.58 (br, 6H, o-Ph), 4.92 (br, 24H, ArCH2O and triazole-
CH2), 4.29–4.21 (br, 18H, imidazole-CH2), 4.11–4.07 (m, 18H, triazole-
CH2), 3.86 (s, 27H, NCH3), 1.72–1.18 ppm (br, 72H, CCH3 and CH2 in
hexyl); 13C NMR (100 MHz, D2O): d=25.5, 29.8, 36.4, 49.9, 62.7, 70.2,
107.5, 122.7, 124.2, 125.7, 134.2, 136.2, 136.5, 142.6, 152.4, 156.9 ppm; IR
(KBr pellet): n˜max =3430, 3065, 2940, 2860, 1605, 1565, 1500, 1455, 1360,
IL-NTf2-G1 (28): Prepared from dendrimer IL-Br-G1 (24) according to
the general procedure for anion exchange to give 28 as a viscous gum
(87%). 1H NMR (400 MHz, CD3CN): d=8.39 (s, 18H, NCHN in imida-
zole), 7.87 (s, 12H, m-NCHC in triazole), 7.75 (s, 6H, p-NCHC in tria-
zole), 7.33–7.30 (d, J=9.5 Hz, 36H, NCHCHN in imidazole), 7.03–7.01
(d, J=8.0 Hz, 6H, o-Ar), 6.93–6.90 (d, J=13.6 Hz, 6H, m-Ar; 12H, o-
Ph), 6.76 (s, 6H, o-Ph), 6.62 (s, 3H, p-Ph), 5.13 (s, 18H, ArCH2O), 5.01
(s, 36H, triazole-CH2), 4.34–4.25 (m, 36H, imidazole-CH2), 4.08–4.03 (m,
36H, triazole-CH2), 3.79 (s, 54H, NCH3), 2.05 (s, 3H, CCH3), 1.85–1.76
(m, 72H, CH2 in hexyl), 1.27 ppm (s, 72H, CH2 in hexyl); 13C NMR
(100 MHz, CD3CN): d=25.9, 30.2, 36.8, 50.2, 63.4, 66.5, 70.7, 108.2, 119.3
(CF3SO), 122.4, 123.2, 124.6, 134.3, 136.8, 137.6, 143.0, 153.2, 161.0 ppm;
IR (KBr pellet): n˜max =3150, 2941, 1639, 1597, 1352, 1192, 1055 cmÀ1; MS
840 cmÀ1
; MS (MALDI-TOF): m/z: calcd for C158H208N45O12: 2927.7
[MÀ9BrÀÀ8H+]+; found: 2928.6.
IL-Br-G1 (24): Prepared from acetylene-terminated dendrimer 15 and
+
À
À À
[N C Min] Br (22, 36 equiv.) according to the general procedure for
the click reaction. Purification by the general procedure for anion ex-
change gave 24 as a viscous gum (85%). 1H NMR (400 MHz, D2O): d=
8.72 (s, 18H, NCHN in imidazole), 8.00 (s, 12H, m-NCHC in triazole),
7.76 (s, 6H, p-NCHC in triazole), 7.41 (s, 36H, imidazole), 6.77 (br, 12H,
o-Ar and m-Ar), 6.41–6.55 (br, 21H, PhH), 4.93 (br, 44H, ArCH2O and
triazole-CH2), 4.21–4.27 (m, 36H, imidazole-CH2), 4.08 (s, 36H, triazole-
CH2), 3.85 (s, 54H, NCH3), 1.71 (s, 75H, CCH3 and CH2 in hexyl),
1.17 ppm (s, 72H, CH2 in hexyl); 13C NMR (100 MHz, D2O): d=25.5,
29.8, 36.4, 49.8, 50.8, 58.8, 62.7, 70.1, 107.6, 122.7, 124.1, 125.5, 134.0,
136.2, 136.4, 143.4, 152.4, 160.3 ppm; IR (KBr pellet): n˜max =3440, 3075,
2935, 2860, 1635, 1560, 1510, 1450, 1360, 1165, 835 cmÀ1; MS (MALDI-
TOF): m/z: calcd for C317H415N90O27: 5914.4 [MÀ18BrÀÀ17H+]+; found:
5924.8.
(MALDI-TOF): m/z: calcd for C351H432F102N107O95S34
:
10690.1
[MÀNTf2À]+; found: 10694.6.
IL-NTf2-G2 (29): Prepared from dendrimer IL-Br-G2 (25) according to
the general procedure for anion exchange to give 29 as a viscous gum
(85%). 1H NMR (400 MHz, CD3CN): d=8.40 (s, 36H, NCHN in imida-
zole), 7.86 (s, 24H, m-NCHC in triazole), 7.73 (s, 12H, p-NCHC in tria-
zole), 7.32–7.29 (d, J=11.3 Hz, 72H, NCHCHN in imidazole), 7.01–6.96
(m, 6H, o-Ar), 6.92–6.88 (d, J=15.6 Hz, 6H, m-Ar; 24H, o-Ph), 6.75 (s,
18H, o-Ph), 6.61 (s, 9H, p-Ph), 5.10 (s, 42H, ArCH2O), 4.98 (s, 72H, tria-
zole-CH2), 4.30–4.23 (m, 72H, imidazole-CH2), 4.07–4.01 (m, 72H, tria-
zole-CH2), 3.78 (s, 108H, NCH3), 2.00 (s, 3H, CCH3), 1.81–1.74 (m,
144H, CH2 in hexyl), 1.25 ppm (s, 144H, CH2 in hexyl); 13C NMR
(100 MHz, CD3CN): d=25.9, 26.3, 30.2, 30.5, 36.8, 50.2, 63.5, 66.8, 70.8,
IL-Br-G2 (25): Prepared from acetylene-terminated dendrimer 16 and
[N-C-Min]+BrÀ (22, 72 equiv.) according to the general procedure for the
click reaction. Purification by the general procedure for anion exchange
108.3, 119.3ACHTNUTRGENNG(U CF3SO), 122.4, 123.2, 124.6, 134.2, 136.8, 137.8, 144.1, 153.3,
161.0 ppm; IR (KBr pellet): n˜max =3153, 2947, 1639, 1597, 1352, 1192,
1
gave 25 as a viscous gum (70.4%). H NMR (400 MHz, D2O): d=8.72 (s,
1055 cmÀ1; MS (ESI-TOF): m/z: calcd for C693H864F174N209O173S58: 2862.9
36H, NCHN in imidazole), 7.98 (s, 24H, m-NCHC in triazole), 7.76 (s,
12H, p-NCHC in triazole), 7.41 (s, 72H, imidazole), 6.80–6.42 (m, 63H,
ArH and PhH), 4.92 (br, 114H, ArCH2O and triazole-CH2), 4.27–4.21
(m, 72H, imidazole-CH2), 4.08 (s, 72H, triazole-CH2), 3.85 (s, 108H,
NCH3), 1.71 (br, 144H, CCH3 and CH2 in hexyl), 1.17 ppm (br, 144H,
CH2 in hexyl); 13C NMR(100 MHz, D2O): d=25.5, 25.7, 29.8, 30.0, 36.4,
49.8, 50.8, 62.6, 70.2, 107.6, 122.7, 124.1, 125.5, 134.1, 136.4, 143.5, 152.5,
160.2 ppm; IR (KBr pellet): n˜max =3435, 3075, 2940, 2860, 1630, 1560,
À
[MÀ7NTf2
]
7+; found:2867.5.
IL-NTf2-G3 (30): Prepared from dendrimer IL-Br-G3 (26) according to
the general procedure for anion exchange to give 30 as a viscous gum
(81%). 1H NMR (400 MHz, CD3CN): d=8.40 (s, 72H, NCHN in imida-
zole), 7.84 (s, 48H, m-NCHC in triazole), 7.71 (s, 24H, p-NCHC in tria-
zole), 7.31–7.27 (d, J=12.5 Hz, 144H, NCHCHN in imidazole), 6.89 (s,
6H, o-Ar; 48H, o-Ph), 6.73 (s, 6H, m-Ar; 18H, o-Ph; 21H, p-Ph), 6.58
(s, 24H, o-Ph), 5.06–4.96 (m, 90H, ArCH2O; 144H, triazole-CH2), 4.30–
4.19 (m, 144H, imidazole-CH2), 4.05–3.99 (m, 144H, triazole-CH2), 3.78–
3.76 (m, 216H, NCH3), 2.13 (s, 3H, CCH3), 1.73 (m, 288H, CH2 in
hexyl), 1.23 ppm (s, 288H, CH2 in hexyl); 13C NMR (100 MHz, CD3CN):
d=25.9, 26.3, 30.3, 30.5, 36.8, 50.3, 50.7, 63.5, 66.7, 70.8, 108.3, 119.3
(CF3SO), 122.4, 123.1, 124.6, 134.2, 136.8, 137.8, 144.0, 153.3, 161.0 ppm;
IR (KBr pellet): n˜max =3152, 2947, 1629, 1602, 1350, 1195, 1053 cmÀ1; MS
(MALDI-TOF): molecular ion peak could not be obtained.
1510, 1460, 1365, 1170, 835 cmÀ1
; MS (ESI-TOF): m/z: calcd for
C635H864Br19N180O57: 789.6 [MÀ17BrÀ]17+; found 792.5.
IL-Br-G3 (26): Prepared from acetylene-terminated dendrimer 17 and
[N-C-Min]+BrÀ (22, 144 equiv.) according to the general procedure for
the click reaction. Purification by the general procedure for anion ex-
change gave 26 as a viscous gum (68%). 1H NMR (400 MHz, D2O): d=
8.71 (s, 72H, NCHN in imidazole), 7.98 (br, 48H, m-NCHC in triazole),
7.73 (br, 24H, p-NCHC in triazole), 7.38 (s, 144H, imidazole), 6.76 (m,
6H, o-Ar; 6H, m-Ar; 90H, o-Ph; 21H, p-Ph), 4.90 (br, 90H, ArCH2O;
144H, triazole-CH2), 4.20–4.06 (m, 144H, imidazole-CH2; 144H, triazole-
Chem. Asian J. 2014, 9, 3641 – 3649
3648
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.chemasianj.org
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Acknowledgements
Financial support from the National Basic Research Program (Grants
2013CB834703 and 2013CB834505), the National Natural Science Foun-
dation of China (Grant Nos. 21233011, 21173245, 21273258, 21002109,
21172229), and the Chinese Academy of Sciences is gratefully acknowl-
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Received: August 16, 2014
Published online: October 16, 2014
Chem. Asian J. 2014, 9, 3641 – 3649
3649
ꢁ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim