Solvent-assisted organized structures based on amphiphilic anion-responsive π-conjugated systems

Article abstract of DOI:10.1002/chem.200802152

synthesis of amphiphilic π-conjugated acyclic oligopyrroles and the formation of solvent-assisted aggregates are reported. We have prepared various types of BF₂ complexes of 1,3-dipyrrolylpropane-1,3-diones bearing aryl rings substituted with h

Full text of DOI:10.1002/chem.200802152

DOI: 10.1002/chem.200802152
Solvent-Assisted Organized Structures Based on Amphiphilic
Anion-Responsive p-Conjugated Systems
Hiromitsu Maeda,*[a, b] Yoshihiro Ito,[a] Yohei Haketa,[a] Nazuki Eifuku,[a] Eunji Lee,[c]
Myongsoo Lee,[c] Takeshi Hashishin,[d] and Kenji Kaneko[e]
Abstract: The synthesis of amphiphilic
p-conjugated acyclic oligopyrroles and
the formation of solvent-assisted aggre-
gates are reported. We have prepared
various types of BF2 complexes of 1,3-
dipyrrolylpropane-1,3-diones bearing
aryl rings substituted with hydrophilic
polyethyleneglycol (PEG) chains, both
as acyclic anion receptors and as build-
ing subunits for organized architectures
based on p–p stacking. The formation
of supramolecular H-type assemblies of
these “amphiphilic” derivatives in
aqueous solution was suggested by
UV/Vis and fluorescence spectroscopy
ses. Cryogenic transmission electron
microscopy (cryo-TEM) analyses of the
aqueous solutions suggest that the fab-
rication of nanoscale network struc-
tures and vesicles depends on the pe-
ripheral substituents. The H-aggregates
in aqueous solution are sensitive to the
conditions required for transformation
into monomers through replacement
with miscible solvents such as alcohols
and into J-type aggregates by water
evaporation and freeze-drying proce-
dures. However, they are fairly stable
and sustainable to anion binding,
whereas on CH2Cl2 extraction they are
transformed into other assembled
modes but remain in the aqueous solu-
tion. The metastable states of affairs
for distributions between two immisci-
ble solvents are controlled by the
orders of solution preparation; this also
suggests that the formation of stable
assemblies is assisted by water mole-
cules. Furthermore, assemblies in
which the stacking modes depend on
the aliphatic side chains are also ob-
served in a nonpolar hydrocarbon sol-
vent.
Keywords: amphiphiles · H-aggre-
gates · pyrrole derivatives · supra-
molecular chemistry · vesicles
1
and further supported by H NMR and
dynamic light scattering (DLS) analy-
Introduction
[a] Prof. Dr. H. Maeda, Y. Ito, Y. Haketa, N. Eifuku
College of Pharmaceutical Sciences
Institute of Science and Engineering
Ritsumeikan University, Kusatsu 525-8577 (Japan)
Fax : (+81)77-561-2659
Supramolecular assemblies in aqueous solution are ubiqui-
tously observed in biotic systems, including in protein fold-
ing, DNA double helices, membranes consisting of lipid bi-
layers, etc.[1] These organized structures can be formed
through the interactions between hydrophobic moieties
inside the assemblies and the association of hydrophilic sites
with water molecules.[2] In artificial systems, various amphi-
philic molecules have been observed to form ordered aggre-
gates in the solution state.[3–6]
Among the building subunits used for supramolecular as-
semblies, p-conjugated systems bearing hydrophilic (and
also aliphatic) chains are useful for the formation of nano-
scale architectures through stacking of p-planes, which also
act as hydrophobic moieties, especially in aqueous solution.
Lee et al., for example, have reported oligophenylene deriv-
atives and their analogues that self-assemble to form nano-
fibers and nanosheets that act as liquid crystals and supra-
molecular gels, and also as micelles and multilayer vesicles.[3]
On the other hand, Fukushima and Aida et al. have report-
E-mail: maedahir@ph.ritsumei.ac.jp
[b] Prof. Dr. H. Maeda
PRESTO, Japan Science and Technology Agency (JST)
Kawaguchi 332-0012 (Japan)
[c] E. Lee, Prof. Dr. M. Lee
Center for Supramolecular Nanoassembly
and Department of Chemistry
Yonsei University, Seoul 120-749 (Korea)
[d] Dr. T. Hashishin
College of Life Sciences, Institute of Science and Engineering
Ritsumeikan University, Kusatsu 525-8577 (Japan)
[e] Prof. Dr. K. Kaneko
Department of Materials Science and Engineering
Graduate School of Engineering, Kyushu University
Fukuoka 819-0395 (Japan)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200802152.
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ed that self-assembly of amphiphilic hexabenzocoronenes
produces p-electronic, discrete nanotubular objects.[4] Fur-
thermore, Wꢁrthner et al. have also reported morphology
control of nanoaggregates governed by the shapes of amphi-
philic perylene bisimides.[5] Dynamic conformation changes
in amphiphilic aggregates resulting from changes in ambient
conditions are fascinating from the point of view of their po-
tential applications as soft materials in aqueous solutions.
Therefore, organized structures that can be modulated by
external physical and chemical stimuli[6] such as temperatur-
e,[6c] solvents,[6d] provide versatile actuators that can be acti-
vated in aqueous solutions and related solvents.
and sustainable to external stimuli such as anions, whereas
extraction with immiscible organic solvents or removal of
water switches the assemblies into other stacking modes
such as J-type aggregates.
Results and Discussion
Synthesis and characterization of amphiphilic C3-bridged oli-
gopyrroles: In this work two kinds of “amphiphilic” recep-
tors were designed: a) derivatives based on hydrophilic
chains and a hydrophobic p-plane, and b) derivatives incor-
porating both hydrophilic and aliphatic (hydrophobic)
chains together with a hydrophobic p plane. We selected
polyethyleneglycol (PEG) units as the neutral hydrophilic
moieties.
As scaffoldings for the formation of organized structures
based on p–p stacking interactions, we have reported acyclic
planar p-conjugated systems in the form of BF2 complexes
of
1,3-dipyrrolylpropane-1,3-diones
(e.g.,
1a–c,
Scheme 1a),[7–9] which are anion receptors[10–12] based on two
pyrrole NH components joined by bridging CH units, in
which anion binding is governed by the inversion of pyrrole
rings (Scheme 1b). In fact, a-aryl-substituted receptors in-
corporating long aliphatic chains, such as 1b or 1c, consti-
tute anion-responsive supramolecular organogels obtained
from octane solutions and exhibit transitions to the solution
state on addition of appropriate anions.[12a] This result sug-
gests that amphiphilic p-conjugated systems bearing hydro-
philic substituents also form stacking structures in aqueous
solution states, giving rise to organized structures potentially
responsive to stimuli such as anions, temperature, and sol-
vents.
As the precursors of amphiphilic anion receptors of
type A, diketones 2a’–c’, with two, four, and six triethylene-
glycol (TEG) chains, respectively, and 2d’, with six hexae-
thyleneglycol (HEG) substituents, at the 3,4,5-positions of
their aryl rings were obtained in 26, 61, 56, and 24% yields,
respectively, from the corresponding arylpyrroles (which
were in turn synthesized through Suzuki cross-coupling reac-
tions[14]) and malonyl chloride in CH2Cl2.[7–9,15] Subsequent
treatment with BF3·OEt2 led to the formation of the highly
fluorescent BF2 complexes 2a–d (Scheme 1c) in moderate
yields. Similarly, the “genuine” amphiphilic derivatives 3a–d
(type B; Scheme 1d), containing both hydrophilic and am-
phiphilic chains, were synthesized from the corresponding
dipyrrolyldiketones 3a’–d’, obtained by condensation of the
two kinds of arylpyrroles and malonyl chloride. The initial
characterization of 2a–d and 3a–d was performed by
1H NMR and FAB-MS or ESI-TOF-MS analysis. These am-
phiphilic derivatives are soluble in ordinary organic solvents
such as CH2Cl2. The absorption
In this article we report the syntheses of amphiphilic p-
conjugated acyclic oligopyrroles (2a–d and 3a–d;
Scheme 1c,d), which in aqueous solution give rise to sol-
vent-assisted assemblies such as nanoscale vesicles[13] based
on H-aggregates; these water-assisted aggregates are stable
maxima (lmax
)
of 2a–d in
CH2Cl2 are observed at 519,
503, 517, and 518 nm, respec-
tively, whereas those of 3a–d
are observed at 519, 520, 519,
and 519 nm, respectively (Fig-
ure S11 in the Supporting In-
formation). These lmax values
are red-shifted in relation to
the lmax value of the a-phenyl
derivative 1a (500 nm),[10a] due
to the electron-donating prop-
erties of the alkoxy groups.
The fluorescence emissions
(lem excited at each lmax) and
quantum yields (FF) of 2a–d
in CH2Cl2 are observed at 557,
534, 558, and 559 nm (FF =
0.94, 0.94, 0.78, and 0.68), re-
spectively, whereas 3a–d ex-
hibit almost the same lem
values: 564, 563, 564, and
Scheme 1. a) BF2 complexes of dipyrrolyldiketones 1a–c. b) Anion binding mode of 1a. c) Amphiphilic deriva-
tives 2a–d (type A). d) Amphiphilic derivatives 3a–d (type B).
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H. Maeda et al.
563 nm (FF =0.81, 0.73, 0.81, and 0.72) (Figure S12 in the
Supporting Information).
lation to those in MeOH (498, 510, and 512 nm) (Figure 1),
suggesting the formation of H-aggregates in aqueous solu-
tion. The absorption spectral changes of 2b–d in mixed sol-
vent systems of water and the miscible MeOH show sweep-
ing “transitions” with increasing proportions of water: the
sigmoidal curves observed in the transitions between mono-
mers (in MeOH) and assemblies (in water) are due to the
selective solvation for each state (monomers and assem-
blies) by MeOH and water, respectively. Moderate red shifts
with small amounts of water are due to the increasing sol-
vent polarity, which stabilizes the polarized excited state
rather than the ground state. In each case, small amounts of
monomers are observed as the shoulders around 500 nm—
especially in the case of 2d—in aqueous solutions. Further-
more, the formation of a tightly stacked assembly of 2b, as
opposed to those of 2c and 2d, is suggested by the shift
values in the absorption spectral changes and the smaller
ratio of water (ca. 70%) at the blue-shift transition; this is
The structures of the amphiphilic receptors optimized by
AM1 calculations show noticeably long molecules in the
stable conformations, with linearly aligned PEG and aliphat-
ic chains. The lengths of the molecules, for example, are
about 37 ꢂ for 2c, 53 ꢂ for 2d, and 39 ꢂ for 3a (Figure S1
in the Supporting Information). The folding geometry of
PEG[3,5,16] in the aqueous solution state, due to hydrogen
bonding with water molecules, is well known, and contrasts
with the straight (all-trans) geometries of alkyl chains. In the
“preorganized” conformations of the amphiphilic molecules
2a–d and 3a–d, with the two inverted pyrrole rings, the hy-
drophilic (and hydrophobic) substituents are located so as to
form hemi-cavities for anion binding.
Self-assembly of PEG-substituted anion receptors (type A)
in aqueous solution: The self-assembly behavior of the am-
phiphilic receptors 2a–d (type A) in aqueous solution was
investigated. Whereas the bis-TEG-substituted 2a exhibits
precipitation in water, the derivatives 2b–d are soluble in
that solvent, in which their lmax values are observed at 460,
496, and 506 nm (1ꢃ10À5 m), respectively, blue-shifted in re-
1
also supported by the broader nature of the H NMR signals
of 2b relative to those of the fairly soluble 2c and 2d in
D2O (Figure S15 in the Supporting Information). The fluo-
rescence spectra of 2b–d in aqueous solution show peaks at
546, 571, and 572 nm (Figure S12 in the Supporting Informa-
Figure 1. UV/Vis absorption spectral changes in H2O/MeOH mixed solvents (1ꢃ10À5 m) and the color changes in H2O and MeOH (insets, 5ꢃ10À4 m)
(top), the changes in the absorbances at the lmax in MeOH according to the proportion (v/v) of water (middle), and the changes in the lmax values accord-
ing to the proportion (v/v) of water (bottom): a) 2b, b) 2c, and c) 2d.
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Solvent-Assisted Organized Structures
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tion) with low emission quantum yields (FF, determined at
lex, which are equal to the corresponding lmax) of 0.01, 0.01,
and 0.09, respectively, which are characteristic features of
H-aggregates. The emissions from the aqueous solution
appear to originate from trace amounts of the monomeric
species in water, as is suggested by the fairly sharp excita-
tion spectrum of each emission maximum, with red-shifted
lmax values of 507 (2b), 524 (2c), and 529 nm (2d), relative
to the absorption maxima in aqueous solution (460, 496, and
504 nm) as H-aggregates and to those in the less polar
CH2Cl2 (503, 517, and 517 nm) as monomers (Figures S11
and S13 in the Supporting Information).[17] This suggestion
is also supported by the strongly emissive properties of 2a–d
in MeOH (lem =554, 533, 555, and 556 nm; FF =0.39, 0.69,
0.37, and 0.41, respectively) and in CH2Cl2 as already de-
scribed (Figures S11–S13 in the Supporting Information).
Dynamic light scattering (DLS) measurements on 2b–d
(1ꢃ10À5 m) in aqueous solutions suggest the formation of ag-
gregates with averaged medium sizes at 708C of 209, 181,
and 105 nm, respectively, whereas those at 208C exhibit
fairly random diagrams with larger distributions (Figure S16
in the Supporting Information).[18] The stacking assemblies
inferable from the spectroscopic analyses would be based on
efficient overlaps at the hydrophobic core p-planes. More
concentrated aqueous solutions of 2b–d (1ꢃ10À4 m) show
precipitation upon heating at about 36, 56, and 958C, re-
spectively, as lower critical solution temperatures (LCSTs),
because dehydration around PEG chains outweighs the
effect of the disaggregation of molecules at higher tempera-
tures.[16b] The variable-temperature (VT) UV/Vis absorption
spectra of 2b–d in aqueous solution might suggest irreversi-
ble transition processes between several aggregated forms
on treatment at high temperature (ca. 908C). In addition,
with use of optical waveguides, solid films cast from aqueous
solutions of 2b–d have almost the same red-shifted UV/Vis
absorption profiles (lmax =526, 540, and 530 nm, respective-
ly; Figure 2) as those cast from CH2Cl2 solutions (lmax =531,
541, and 535 nm; Figure S17 in the Supporting Information),
suggesting that the removal of water molecules by slow
evaporation at room temperature disrupts the H-aggregate
formations and, instead, produces the J-aggregates. Further-
more, freeze-drying is also not efficient in sustaining the
solid-state organized structures as observed in aqueous solu-
tion, as is suggested by the red-shifted J-like UV/Vis absorp-
tion spectra of these amphiphilic receptors (e.g., 2c) in the
solid state (film) obtained by this procedure.[19] These results
from solid-state absorptions with or without freeze-drying
suggest that the formation of H-aggregates in aqueous solu-
tion is supported by water molecules, and that the removal
of water molecules around the assemblies results in the for-
mation of different assembled structures (J-type aggregates;
Figure 3a), as observed in the reported single-crystal X-ray
structures of the receptors (e.g., 1a;[9a] Figure 3b).
Figure 2. UV/Vis absorption spectra of a) 2b, b) 2c, and c) 2d as solid-
state cast from aqueous solution (a) and in aqueous solution (c).
of aqueous solutions (1ꢃ10À5 m) of tetra-TEG-substituted
2b, hexa-TEG-substituted 2c, and hexa-HEG-substituted 2d
with UO2ACHTNUTRGENNG(U OAc)2 staining (Figure S18 in the Supporting In-
formation). In contrast, small rope-like network structures
of about 5 nm in width were observed by cryogenic TEM
(cryo-TEM) analysis of 2c (1ꢃ10À5 m; Figure 4). In aqueous
Next, the morphologies of the transformed organized
structures obtained from aqueous solution were examined.
Only larger assemblies without specific shapes were ob-
served by transmission electron microscopy (TEM) analysis
Figure 3. a) Possible proposed transition pathway (for 2c) from H-aggre-
gates to J-aggregates through removal of water molecules, and b) slipped
stacking structures of 1a in the solid state.[9a]
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H. Maeda et al.
the lengths of the hydrophilic and hydrophobic chains
appear to be essential.
The receptors 3a and 3b (1ꢃ10À5 m) exhibited absorption
maxima at 462 and 481 nm, respectively, in water and at 510
and 512 nm in MeOH. These results are quite similar to
those seen in the cases of 2b–d (type A), which exist as H-
aggregates in aqueous solution and as monomers in MeOH
(Figure 5). The stacking interactions of 3a and 3b are fairly
strong relative to those of the amphiphiles 2b–d (type A),
possibly due to the existence of the aliphatic long chains in
the type B derivatives, as observed in the smaller propor-
tions of water (ca. 30 and 40%), which are necessary before
blue shifts are observed. Furthermore, 3a has more tightly
stacked H-aggregates than 3b, due to the shorter hydrophil-
ic chains in 3a, as also observed in the cases of 2c and 2d.
The fluorescence emissions of 3a and 3b in aqueous solu-
tion are observed at 672 and 671 nm (Figure S11 in the Sup-
porting Information) with emission quantum yields (FF, de-
termined at lex values equal to the corresponding lmax
values) of 0.02 and 0.02, respectively, in contrast with those
Figure 4. Cryo-TEM image of 2c obtained from aqueous solution (1ꢃ
10À5 m) without staining.
solution, 2c appears to be soluble as an H-aggregated net-
work object, possibly fabricated through p–p stacking of the
core planes and interactions between the hydrophilic side
chains and water molecules. The widths of 5 nm are consis-
tent with the bundled architectures consisting of pairs of the
p–p stacking columns. In this case, TEG substituents can ef-
fectively function as the hydrophilic components of the net-
works associating with water
in MeOH [FF =0.32 (lem =558 nm) for 3a and 0.35 (lem
=
molecules. Removal of water
molecules around the hydro-
philic parts of the nanoscale
networks during the prepara-
tion of conventional TEM
samples might be expected to
result in their assembly to
form larger objects without
specific morphologies through
interaction between the hydro-
philic side chains.
Self-assemblies of amphiphilic
anion receptors with both
PEG and long aliphatic chains
(type B) in aqueous solution:
Similarly to the self-assemblies
based on 2b–d (type A) in
aqueous solution, those of 3a
and 3b (type B) are also very
fascinating. The formation of
nanoarchitectures in aqueous
solution was suggested by their
solvent-dependent UV/Vis ab-
sorption spectra (Figure S11 in
the Supporting Information).
The amphiphiles 3c and 3d,
though, are either completely
insoluble or less soluble, re-
spectively, in water, possibly
due to their more hydrophobic
hexadecyloxy groups. Although
Figure 5. UV/Vis absorption spectral changes in H2O/MeOH mixed solvents (1ꢃ10À5 m) and the color changes
in H2O and MeOH (insets, 5ꢃ10À4 m) (top), the changes in the absorbances at the lmax in MeOH according to
the proportion (v/v) of water (middle), and the changes in the lmax values according to the proportion (v/v) of
water (bottom): a) 3a, and b) 3b.
the solubilities of 3a–d in
aqueous solution cannot be ex-
plained in detail at this time,
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Solvent-Assisted Organized Structures
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558 nm) for 3b]. Red shifts in the emissions of 3a and 3b in
aqueous solutions, unlike those of 2b–d, originate from the
aggregates and not from the monomers, as is suggested by
excitation spectra, due to tighter stacking behavior of 3a
and 3b (type B) than of 2b–d (type A). Furthermore, DLS
measurements on 3a (1ꢃ10À5 m) at 708C exhibited aggre-
gates with the averaged medium size of 184 nm, which is
quite different from the diagrams at 208C, with a large dis-
tribution. In the case of 3b (1ꢃ10À5 m), on the other hand,
DLS analyses at 208C (85 nm) and at 708C (113 nm) appear
fairly similar (Figure S16 in the Supporting Information).[18]
Like those cast from 2b–d, the solid films cast from aqueous
solutions of 3a and 3b exhibit the formation of J-aggregates,
as suggested by the UV/Vis absorption profiles (lmax =548
and 531 nm, respectively, Figure 6), which are similar to
those cast from CH2Cl2 solutions (lmax =543 and 530 nm;
Figure S17 in the Supporting Information).
(ca. 3.9 nm by AM1 calculation). Among organized architec-
tures, vesicles are supramolecular self-assemblies consisting
of amphiphiles, such as the intracellular membrane-enclosed
capsules in biotic systems.[13] In most cases, including that of
biotic lipids, hydrophilic head groups face toward the aque-
ous phases to maintain hydrophobic tails inside the assem-
blies. Unlike the amphiphile 2c (type A), possessing only
hydrophilic chains, 3a (type B) might possibly form bilayers
like biotic lipids through the use of hydrophobic interactions
of aliphatic chains and the location of hydrophilic TEG
chains outside the layers to produce water-soluble vesicles
(Figure 7c).[20]
Figure 6. UV/Vis absorption spectra of a) 3a and b) 3b as solid-state cast
from aqueous solution (a) and in aqueous solution (c).
TEM analyses of aqueous solutions (1ꢃ10À5 m) of 3a and
Figure 7. Images of a) TEM of 3a from aqueous solution (1ꢃ10À5 m) with
3b with UO2ACHTUNGTRENNUNG(OAc)2 staining showed the formation of capsu-
UO2ACTHNUTRGNEUNG(OAc)2 staining, and b) cryo-TEM of 3a from aqueous solution (1ꢃ
10À5 m) without staining. c) Possible assembling mode of 3a in vesicles.
les of diameters in the 50–150 nm range (Figure 7a) and cy-
lindrical aggregates, respectively, as the transformed objects
formed by removal of water molecules around the hydro-
philic moieties (Figure S18 in the Supporting Information).
We cannot as yet confirm the extent of the effect of the as-
sembled modes—H- and J-aggregates—on the organized
structures, but some insights have been obtained for specu-
lation on the effect of the water-assisted assembled struc-
tures. Furthermore, cryo-TEM analysis of 3a (1ꢃ10À5 m)
also showed vesicular structures with diameters of 30–80 nm
(Figure 7b), which are consistent with the results of DLS
measurements. The wall thickness (dark part) of the capsu-
les is estimated to be about 5 nm, which suggests hydropho-
bic segments consisting of bilayers of amphiphilic molecules
Self-assembly of amphiphilic anion receptors in a nonpolar
solvent (hexane): Just as the amphiphiles (2b–d, 3a, and 3b)
in aqueous solutions are transformed from H-aggregates
into J-type assemblies on removal of solvent molecules,
whereas those in CH2Cl2 are transformed into J-aggregates
from monomers (see above), nonpolar solvents such as
hexane also enhance p–p stacking interactions to produce
assemblies in these solutions.[21] The UV/Vis absorption
spectrum of hexa-HEG-substituted 2d, which is almost in-
soluble in hexane, shows the formation of J-aggregates in
the form of red-shifted absorptions (lmax =526 nm), although
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H. Maeda et al.
the other amphiphiles of type A (2a–c) are completely in-
soluble in this solvent. The type B compounds 3a–d, on the
other hand, are “soluble” in hexane (1ꢃ10À5 m) at 208C as
mixtures of monomers and aggregates (Figure S19 in the
Supporting Information), whereas at 608C they exist as
monomers (lmax =500, 505, 500, and 505 nm, respectively;
Figure 8), like the derivative with six hexadecyloxy chains,
which is soluble in octane at room temperature.[9a] Less
polar hexane stabilizes the ground states of the amphiphiles
to produce absorption maxima that are blue-shifted relative
to those seen in CH2Cl2 (519–520 nm) and MeOH (510–
512 nm), corresponding to monomer forms.
Upon cooling of the 3a and 3b solutions to À608C, ab-
sorptions are observed in the red-shift region, either as a
shoulder (ca. 540 nm, 3a) or as a new peak (547 nm, 3b)
(Figure 8a,b), suggesting the formation of J-aggregates as
mixtures with monomers. In sharp contrast, cooling of 3c or
3d solutions to À608C results in spectral changes with blue
shifts to 444 (3c) or 455 nm (3d) (Figure 8c,d), indicating
the formation of H-aggregates in the case of hexadecyloxy-
substituted amphiphiles. The observation of the slight red
shifts (509 and 519 nm) at 20 and 408C in the case of 3d,
possibly due to J-aggregates, is of interest. In the cases of
3b–d, transitions to stable forms at low temperatures dra-
matically occur in the regions of 20–40, 10–20, and 10–208C,
respectively. In these cases, small amounts of H- (3b) and J-
aggregates (3c, 3d) also appear to exist and are reflected as
shoulders or small bands. Furthermore, the transitions be-
tween monomers and assembled forms are also detectable
by naked eye (insets of Figure 8). Such thermochromic be-
havior is due to temperature-responsive p–p stacking aggre-
gation properties[22,23] of the type B amphiphiles in hexane.
The type B amphiphiles exhibit the formation of aggre-
gates and, fascinatingly, modulate their preferable assembly
modes (H and J) as functions both of temperature and of
aliphatic chain length (octyloxy and hexadecyloxy) not only
in aqueous solution but also in nonpolar solvents. Such ob-
servations in interactions in the apolar solvent are due to
one of the unique properties of these amphiphiles: their pos-
session of both hydrophilic and hydrophobic (sp3) chains at-
tached to the core hydrophobic (sp2) plane as reported here.
Detailed investigations, including those of solvent effects,
are important topics for future research.
Figure 8. Variable-temperature UV/Vis absorption spectra of a) 3a,
b) 3b, c) 3c, and d) 3d in hexane (1ꢃ10À5 m) from 60 to À608C in steps
of 208C, as indicated by arrows, together with photographs at 60 and
À208C (insets).
Sustainable behavior of the assemblies consisting of amphi-
philic receptors for anions: The anion-binding behavior of
the amphiphiles in aqueous solution[24] was investigated by
observation of the UV/Vis absorption spectral changes of
mixtures of 1, 10, and 1000 equiv of anions (FÀ, ClÀ, BrÀ, IÀ,
cations) by polar protic solvents. Slightly decreased absorb-
ance may originate from the salting out of the aggregates
from the solution associated with the ion pairs, rather than
just the anions. Furthermore, like those in cases in the ab-
sence of anions, DLS measurements on 2b–d, 3a, and 3b
(1ꢃ10À5 m) in the presence of TBACl (1 equiv) in aqueous
solutions show complicated profiles at 208C and fairly or-
dered ones, with averaged diameters of 336 (2b), 77 (2c),
186 (2d), 212 (3a), and 99 nm (3b), at 708C (Figure S22 in
À
À
À
CH3CO2 , H2PO4 , and H2SO4 ) as their TBA salts and the
amphiphiles (e.g., 2c and 3a, 1ꢃ10À5 m) in aqueous solu-
tions, prepared in CH2Cl2 followed by evaporation of the
solvent and addition of water (Figures S20 and S21 in the
Supporting Information). The absorption maxima in aque-
ous solutions hardly shift, possibly due to i) lower anion af-
finities of assembled receptors in relation to those of the
monomeric receptors, and ii) tight solvation of anions (and
3712
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Chem. Eur. J. 2009, 15, 3706 – 3719

Solvent-Assisted Organized Structures
FULL PAPER
the Supporting Information).[18] These observations also sup-
port the robustness of H-aggregates consisting of amphiphil-
ic acyclic anion receptors in aqueous solution.[25]
of H- and J-type aggregates, suggesting that the CH2Cl2-sa-
turated aqueous solution also prefers J-like states, and not
just H-aggregates, possibly due to solvation of the amphi-
philes by small amounts of the less polar solvent molecules
(Figure S23 in the Supporting Information). DLS measure-
ments on the amphiphiles in the aqueous phases showed the
formation of fairly ordered assemblies, relative to those in
ordinary aqueous solutions, with discrete medium sizes both
at 20 and at 708C (Figure S24 in the Supporting Informa-
tion).[26] This result may suggest that only “non-standard” as-
semblies, as well as small amounts of monomers, can be
readily extracted into the organic (CH2Cl2) phase, due to
their lower tendency to stay in the hydrophilic environ-
ments. Furthermore, and in sharp contrast, amphiphiles 2b–
d and 3a, existing as their monomeric forms, in CH2Cl2 solu-
tion cannot be extracted into an aqueous phase (Figure 9a–
d,ii). These observations suggest that, once formed in aque-
ous solution, the self-assemblies are stable and resist extrac-
tion into an organic phase (CH2Cl2).[27]
Water-assisted rigid organized structures of amphiphilic
anion receptors suggested by distributions between aqueous
and organic solutions: The “water-soluble” amphiphiles 2b–
d (type A) and 3a and 3b (type B) exhibit unique behavior
during the extraction processes. The amphiphiles 2b–d
(type A) are spontaneously soluble in aqueous solution,
whereas 3a and 3b (type B) are stable as precipitates in
water and become soluble upon shaking (left-hand pictures
in Figure 9a–e,i). In water/CH2Cl2 immiscible solvent sys-
Unlike 2b–d and 3a, the amphiphile 3b undergoes almost
complete extraction with CH2Cl2 (Figure 9e,i), whereas, as
in the cases of the other amphiphiles, water cannot extract
3b from a CH2Cl2 solution (Figure 9e,ii). As shown in
Figure 5, 3b forms less stable stacking assemblies than 3a,
so the organized structures of 3b in an aqueous solution
should be readily extracted into a CH2Cl2 phase, even
though 3b has longer hydrophilic chains. The metastable sit-
uations for the distributions between two immiscible sol-
vents (water and CH2Cl2 in this case) are found to depend
on the substituents of the molecules and the stability of
each assembly in aqueous solution. Furthermore, the initial
conditions, based on water-assisted aggregation and CH2Cl2-
supported disaggregation, are crucial in providing the de-
sired metastable states in the different solvent systems.
Conclusions
In this article we have reported the synthesis of anion-re-
sponsive amphiphiles that form solvent-assisted organized
structures. From observations such as the binding affinity
toward anions and extraction experiments performed with
an immiscible organic solvent, it has been observed that the
p-conjugated acyclic oligopyrroles based on 1,3-dipyrrolyl-
propane-1,3-dione units, in which the p components are con-
nected by single bonds, enter into more rigid p–p stacking
interactions than expected; the H-type assemblies in aque-
ous solutions form nanoscale networks and vesicular struc-
tures detectable by cryo-TEM. The H-aggregates are sensi-
tive to the conditions and are transformed into J-aggregates
on removal of water. Formation mechanisms and styles of
nanoscale structures such as vesicles depend on the molecu-
lar structures of the building amphiphiles. Therefore, modifi-
cations in the numbers, positions, and shapes of the periph-
eral substituents should result in versatile, unique organized
architectures and stimuli-responsive soft materials with vari-
ous potential utilities such as carrier and exciton mobility. In
Figure 9. Photographs of extraction processes of a) 2b, b) 2c, c) 2d,
d) 3a, and e) 3b: i) aqueous solutions before shaking (left), two phases
(water and CH2Cl2; right), and extraction from the aqueous solutions
(center); ii) two phases (water and CH2Cl2; right), and extraction from
the CH2Cl2 solutions (left). Initial concentrations are 1ꢃ10À4 m.
tems, the “order” of preparation is essential for the forma-
tion of aggregates.[6d] As an example, the addition of CH2Cl2
to aqueous solutions of 2b–d or 3a (1ꢃ10À4 m) and subse-
quent extraction results in aqueous upper phases containing
larger quantities of amphiphiles than the organic lower
phases (Figure 9a–d,i). The “structures” in both layers are
postulated from the UV/Vis absorption spectra in each
phase under diluted conditions (1ꢃ10À5 m). The spectra of
the amphiphiles (e.g., 2c and 3a) in the CH2Cl2 phases are
quite similar to those in the pure solutions (as monomers),
whereas those in the aqueous phases correspond to mixtures
Chem. Eur. J. 2009, 15, 3706 – 3719
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3713

H. Maeda et al.
508C for 33 h. The mixture was allowed to cool and poured into a sepa-
rating funnel together with water (25 mL), and the aqueous solution was
extracted with CH2Cl2. The combined extracts were dried over anhydrous
MgSO4, and DMF was removed in vacuo to give an oil. The residue was
then chromatographed over silica gel (Wakogel C-300, 2.5% MeOH/
CH2Cl2) to give 5-bromo-1,2,3-tris-TEG-benzene (1.30 g, 69%) as a col-
orless oil. Rf =0.34 (5% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3,
208C): d=6.73 (s, 2H; Ar-H), 4.13–3.53 (m, 36H; OCH2), 3.38 ppm (m,
9H; OCH3); FAB-MS: m/z (%): calcd for C27H47BrO12: 642.23 [M]+;
found: 642.3 (100), 643.3 (59).
addition, even though further efforts are required in order
to predict the exact assembled modes by theoretical studies,
due to the less symmetrical structures of the amphiphiles, it
is crucial to elucidate the factors and mechanism of assem-
bly formation in detail. This is currently being investigated.
Experimental Section
5-Bromo-1,2,3-tris-HEG-benzene: Pulverized K2CO3 (1.56 g, 11.2 mmol)
was added to a DMF solution (18 mL) of 5-bromo-1,2,3-trihydroxyben-
zene (459.5 mg, 2.2 mmol) and hexaethyleneglycol (HEG) toluene-4-sul-
fonate (3.32 g, 7.4 mmol), and the system was stirred under nitrogen at
508C for 30 h. The mixture was allowed to cool and poured into a sepa-
rating funnel together with water (20 mL), and the aqueous solution was
extracted with CH2Cl2. The combined extracts were dried over anhydrous
MgSO4, and DMF was removed in vacuo to give an oil. The residue was
then chromatographed over silica gel (Wakogel C-300, 5% MeOH/
CH2Cl2) to give 5-bromo-1,2,3-tris-HEG-benzene (1.78 g, 77%) as a col-
orless oil. Rf =0.41 (10% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3,
208C): d=6.73 (s, 2H; Ar-H), 4.12 (m, 4H; OCH2), 4.10 (m, 2H; OCH2),
3.83 (m, 4H; OCH2), 3.76 (m, 2H; OCH2), 3.71–3.63 (m, 54H; OCH2),
3.55 (m, 6H; OCH2), 3.38 ppm (m, 9H; OCH3); FAB-MS: m/z (%):
calcd for C45H83BrO21: 1038.46 [M]+; found: 1038.5 (100).
Starting materials were purchased from Wako Chemical Co., Nacalai
Chemical Co., and Aldrich Chemical Co. and were used without further
purification unless otherwise stated. Aqueous solutions of the amphi-
philes for various analyses were prepared from water of spectroscopic
grade (Wako). UV/Vis spectra were recorded with a Hitachi U-3500
spectrometer for the solution state and with a System Instruments SIS-50
surface and interface spectrometer for the solid state. Variable-tempera-
ture UV/Vis spectra were obtained with the aid of a Unisoku USP-203 A
spectrophotometer cryostat. Fluorescence spectra and quantum yields
were recorded with a Hitachi F-4500 fluorescence spectrometer for ordi-
nary solutions and a Hamamatsu C9920-02 quantum yield measurement
system for organic LED materials. NMR spectra used in the characteriza-
tion of products were recorded on a JEOL ECA-600 600 MHz spectrom-
eter. All NMR spectra were referenced to solvent. Fast atom bombard-
ment mass spectrometric studies (FAB-MS) were performed with a
JEOL-GCmate instrument in the positive ion mode with a 3-nitrobenzyl
alcohol matrix. Electrospray ionization mass spectrometric studies (ESI-
MS) were recorded with a BRUKER microTOF instrument by negative
mode ESI-TOF. TLC analyses were carried out on aluminum sheets
coated with silica gel 60 (Merck 5554). Column chromatography was per-
formed on Sumitomo alumina KCG-1525, Wakogel C-300, and Merck
silica gel 60 and 60H.
1-tert-Butoxycarbonyl-2-(4-TEG-phenyl)pyrrole and 2-(4-TEG-phenyl)-
pyrrole: A solution of Na2CO3 (267.0 mg, 2.5 mmol) in water (2 mL) was
added at room temperature under nitrogen to a solution of 4-bromo-1-
TEG-benzene (191.1 mg, 0.60 mmol), 1-tert-butoxycarbonylpyrrole-2-bor-
onic acid (169.6 mg, 0.80 mmol), and tetrakis(triphenylphosphine)palladi-
um(0) (35.5 mg, 0.031 mmol) in 1,2-dimethoxyethane (17 mL).[30] The
mixture was heated at reflux for 6 h, allowed to cool, and then parti-
tioned between water and CH2Cl2. The combined extracts were dried
over anhydrous MgSO4 and concentrated to give an oil. The residue was
then chromatographed over silica gel (Wakogel C-300, 40% EtOAc/
4-Bromo-1-TEG-benzene: Pulverized K2CO3 (880.2 mg, 6.4 mmol) was
added to a DMF (9 mL) solution of 4-bromophenol (732.5 mg, 4.2 mmol)
and triethyleneglycol (TEG) toluene-4-sulfonate (677.3 mg, 2.1 mmol),
and the mixture was stirred under nitrogen at 508C for 27 h. The mixture
was allowed to cool and poured into a separating funnel together with
water (30 mL). The aqueous solution was extracted with CH2Cl2. The
combined extracts were washed with aq. NaOH (10%) and water. The
CH2Cl2 layer was dried over anhydrous MgSO4 and concentrated to give
an oil. The residue was then chromatographed over silica gel (Wako-
gel C-300, 1% MeOH/CH2Cl2) to give 4-bromo-1-TEG-benzene
hexane)
(197.7 mg, 81%) as
to
give
1-tert-butoxycarbonyl-2-(4-TEG-phenyl)pyrrole
colorless oil. Rf =0.45 (50% EtOAc/hexane);
a
1H NMR (600 MHz, CDCl3, 208C): d=7.31 (m, 1H; pyrrole-H), 7.25 (d,
J=8.4 Hz, 2H; Ar-H), 6.89 (d, J=8.4 Hz, 2H; Ar-H), 6.20 (m, 1H; pyr-
role-H), 6.12 (m, 1H; pyrrole-H), 4.15–3.55 (m, 12H; OCH2), 3.38 (s,
3H; OCH3), 1.38 ppm (s, 9H; Boc); FAB-MS: m/z (%): calcd for
C22H31NO6: 405.22 [M]+; found: 405.3 [M]+ (100), 406.3 [M+1]+ (51).
The product 1-tert-butoxycarbonyl-2-(4-TEG-phenyl)pyrrole (197.7 mg,
0.49 mmol) was heated at reflux (1608C) for 30 min and then allowed to
cool. The residue was then chromatographed over silica gel (Wakogel C-
300, 55% EtOAc/hexane) to give 2-(4-TEG-phenyl)pyrrole as a colorless
oil (105.3 mg, 71%). Rf =0.21 (50% EtOAc/hexane); 1H NMR
(600 MHz, CDCl3, 208C): d=8.34 (br, 1H; NH), 7.38 (d, J=7.8 Hz, 2H;
Ar-H), 6.93 (d, J=8.4 Hz, 2H; Ar-H), 6.83 (m, 1H; pyrrole-H), 6.40 (m,
1H; pyrrole-H), 6.27 (m, 1H; pyrrole-H), 4.15 (t, J=4.8 Hz, 2H; OCH2),
3.87 (t, J=4.8 Hz, 2H; OCH2), 3.75 (t, J=4.8 Hz, 2H; OCH2), 3.69 (t,
J=4.8 Hz, 2H; OCH2), 3.66 (t, J=4.8 Hz, 2H; OCH2), 3.55 (t, J=4.8 Hz,
2H; OCH2), 3.38 ppm (s, 3H; OCH3); FAB-MS: m/z (%): calcd for
C17H23NO4: 305.16 [M]+; found: 305.2 (100), 306.2 (68).
(583.3 mg, 86%) as
a
colorless oil. Rf =0.63 (EtOAc); 1H NMR
(600 MHz, CDCl3, 208C): d=7.36 (m, 2H; Ar-H), 6.80 (m, 2H; Ar-H),
4.09 (m, 2H; OCH2), 3.85 (m, 2H; OCH2), 3.73 (m, 2H; OCH2), 3.68 (m,
2H; OCH2), 3.65 (m, 2H; OCH2), 3.55 (m, 2H; OCH2), 3.38 ppm (s, 3H;
OCH3); FAB-MS: m/z (%): calcd for C13H19BrO4: 318.05 [M]+; found:
318.1 (70), 319.1 (100).
5-Bromo-1,3-bis-TEG-benzene: Pulverized K2CO3 (542.3 mg, 3.9 mmol)
was added to a DMF (8 mL) solution of 5-bromo-1,3-dihydroxyben-
zene[28] (221.5 mg, 1.2 mmol) and triethyleneglycol (TEG) toluene-4-sul-
fonate (747.0 mg, 2.4 mmol), and the system was stirred under nitrogen
at 508C for 32 h. The mixture was allowed to cool and poured into a sep-
arating funnel together with water (10 mL), and the aqueous solution
was extracted with CH2Cl2. The combined extracts were washed with aq.
NaOH (10%) and water. The CH2Cl2 layer was dried over anhydrous
MgSO4 and concentrated to give an oil. The residue was then chromato-
graphed over silica gel (Wakogel C-300, 2% MeOH/CH2Cl2) to give 5-
bromo-1,3-bis-TEG-benzene (418.8 mg, 74%) as a colorless oil. Rf =0.33
(EtOAc); 1H NMR (600 MHz, CDCl3, 208C): d=6.67 (m, 2H; Ar-H),
6.42 (m, 1H; Ar-H), 4.08–3.47 (m, 24H; OCH2), 3.38 ppm (s, 6H;
OCH3); FAB-MS: m/z (%): calcd for C20H33BrO8: 480.14 [M]+; found:
480.2 (19), 481.2 (100).
1-tert-Butoxycarbonyl-2-(3,5-bis-TEG-phenyl)pyrrole and 2-(3,5-bis-
TEG-phenyl)pyrrole: A solution of Na2CO3 (589.1 mg, 5.6 mmol) in
water (3 mL) was added under nitrogen at room temperature to a solu-
tion of 4-bromo-1,3-bis-TEG-benzene (418.8 mg, 0.87 mmol), 1-tert-but-
oxycarbonylpyrrole-2-boronic acid (371.1 mg, 1.76 mmol), and tetrakis-
(triphenylphosphine)palladium(0) (77.0 mg, 0.067 mmol) in 1,2-dime-
thoxyethane (35 mL). The mixture was heated at reflux for 6 h, allowed
to cool, and then partitioned between water and CH2Cl2. The combined
extracts were dried over anhydrous MgSO4 and concentrated to give an
oil. The residue was then chromatographed over silica gel (Wakogel C-
300, 2% MeOH/CH2Cl2) to give 1-tert-butoxycarbonyl-2-(3,5-bis-TEG-
phenyl)pyrrole (475.1 mg, 64%) as a colorless oil. Rf =0.50 (5% MeOH/
CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=7.31 (m, 1H; pyrrole-
H), 6.50 (m, 2H; Ar-H), 6.45 (m, 1H; Ar-H), 6.20 (m, 1H; pyrrole-H),
5-Bromo-1,2,3-tris-TEG-benzene: Pulverized K2CO3 (2.30 g, 16.7 mmol)
was added to a DMF solution (18 mL) of 5-bromo-1,2,3-trihydroxyben-
zene[29] (600.5 mg, 2.9 mmol) and triethyleneglycol (TEG) toluene-4-sul-
fonate (3.21 g, 10.1 mmol), and the system was stirred under nitrogen at
3714
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Chem. Eur. J. 2009, 15, 3706 – 3719

Solvent-Assisted Organized Structures
FULL PAPER
6.17 (m, 1H; pyrrole-H), 4.11–3.54 (m, 24H; OCH2), 3.38 (s, 6H; OCH3),
1.38 ppm (s, 9H; Boc); FAB-MS: m/z (%): calcd for C29H45NO10: 567.30
[M]+; found: 567.4 (100), 568.4 (86). The product 1-tert-butoxycarbonyl-
2-(3,5-bis-TEG-phenyl)pyrrole (475.1 mg, 0.84 mmol) was heated at
1608C for 30 min and then allowed to cool. The residue was then chro-
matographed over silica gel (Wakogel C-300, 2% MeOH/CH2Cl2) to give
2-(3,5-bis-TEG-phenyl)pyrrole as a colorless oil (359.6 mg, 92%). Rf =
0.45 (5% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=8.69
(br, 1H; NH), 6.84 (m, 1H; pyrrole-H), 6.68 (m, 2H; Ar-H), 6.49 (m,
1H; pyrrole-H), 6.35 (m, 1H; Ar-H), 6.27 (m, 1H; pyrrole-H), 4.15–3.55
(m, 24H; OCH2), 3.38 ppm (s, 6H; OCH3); FAB-MS: m/z (%): calcd for
C24H37NO8: 467.25 [M]+; found: 467.3 (73), 468.3 (100).
1,3-Bis[5-(4-TEG-phenyl)pyrrol-2-yl]propane-1,3-dione (2a’): In analogy
to a literature procedure, a CH2Cl2 solution (2 mL) of 2-(4-TEG-phenyl)-
pyrrole (105.3 mg, 0.35 mmol) was treated at 08C with malonyl chloride
(24.6 mg, 0.18 mmol) and stirred for 4 h at the same temperature. After
confirmation of the consumption of the starting pyrrole by TLC analysis,
the mixture was washed with saturated aq. Na2CO3 and saturated aq.
NaCl, dried over anhydrous Na2SO4, filtered, and concentrated to dry-
ness. The residue was then chromatographed over silica gel (Wakogel C-
300, 3.5% MeOH/CH2Cl2) and recrystallized from CH2Cl2/hexane to
afford 2a’ (30.6 mg, 26%) as a pale yellow solid. Rf =0.40 (5% MeOH/
1
CH2Cl2); H NMR (600 MHz, CDCl3, 208C; diketone 2a’ is obtained as a
mixture of keto and enol tautomers in the ratio of 1:0.23): d (keto
form)=9.45 (br, 2H; NH), 7.49 (d, J=9.0 Hz, 4H; Ar-H), 7.13 (m, 2H;
pyrrole-H), 6.96 (d, J=9.0 Hz, 4H; Ar-H), 6.49 (m, 2H; pyrrole-H), 4.22
(s, 2H; CH2), 4.16 (m, 4H; OCH2), 3.87 (m, 4H; OCH2), 3.75 (m, 4H;
OCH2), 3.69 (m, 4H; OCH2), 3.66 (m, 4H; OCH2), 3.55 (m, 4H; OCH2),
3.38 ppm (s, 6H; OCH3); d (enol form)=16.71 (s, 1H; OH), 9.34 (s, 2H;
NH), 7.50 (m, 4H; Ar-H), 6.97 (m, 4H; Ar-H), 6.95 (m, 2H; pyrrole-H),
6.52 (m, 2H; pyrrole-H), 6.33 (s, 1H; CH), 4.18–3.54 (m, 24H; OCH2),
1-tert-Butoxycarbonyl-2-(3,4,5-tris-TEG-phenyl)pyrrole and 2-(3,4,5-tris-
TEG-phenyl)pyrrole: A solution of Na2CO3 (260.8 mg, 2.5 mmol) in
water (2 mL) was added at room temperature under nitrogen to a solu-
tion of 5-bromo-1,2,3-tris-TEG-benzene (374.5 mg, 0.58 mmol), 1-tert-bu-
toxycarbonylpyrrole-2-boronic acid (164.9 mg, 0.78 mmol), and tetrakis-
(triphenylphosphine)palladium(0) (40.6 mg, 0.035 mmol) in 1,2-dime-
thoxyethane (15 mL). The mixture was heated at reflux for 6 h, allowed
to cool, and then partitioned between water and CH2Cl2. The combined
extracts were dried over anhydrous MgSO4 and concentrated to give an
oil. The residue was then chromatographed over silica gel (Wakogel C-
300, 2.5% MeOH/CH2Cl2) to give 1-tert-butoxycarbonyl-2-(3,4,5-tris-
TEG-phenyl)pyrrole (370.0 mg, 87%) as a colorless oil. Rf =0.35 (5%
MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=7.31 (m, 1H;
pyrrole-H), 6.56 (s, 2H; Ar-H), 6.20 (m, 1H; pyrrole-H), 6.14 (m, 1H;
pyrrole-H), 4.16–3.53 (m, 36H; OCH2), 3.38 (s, 3H; OCH3), 3.37 (s, 6H;
OCH3), 1.36 ppm (s, 9H; Boc); FAB-MS: m/z (%): calcd for C16H19NO2:
729.39 [M]+; found: 729.4 (100). The product 1-tert-butoxycarbonyl-2-
(3,4,5-tris-TEG-phenyl)pyrrole (444.3 mg, 0.61 mmol) was heated at
reflux (1608C) for 30 min and then allowed to cool. The residue was then
chromatographed over silica gel (Wakogel C-300, 2.7% MeOH/CH2Cl2)
to give 2-(3,4,5-tris-TEG-phenyl)pyrrole as a colorless oil (340.3 mg,
89%). Rf =0.27 (5% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3,
208C): d=9.04 (br, 1H; NH), 6.83 (m, 1H; pyrrole-H), 6.82 (s, 2H; Ar-
H), 6.41 (m, 1H; pyrrole-H), 6.25 (m, 1H; pyrrole-H), 4.23–3.54 (m,
36H; OCH2), 3.37 (s, 3H; OCH3), 3.37 (s, 6H; OCH3); FAB-MS: m/z
(%): calcd for C31H51NO12: 629.34 [M]+; found: 629.4 (100), 630.3 (56).
3.38 ppm (s, 6H; OCH3); FAB-MS: m/z (%): calcd for C37H46N2O10
678.32 [M]+; found: 678.3 (84), 679.3 (100).
:
1,3-Bis[5-(3,5-bis-TEG-phenyl)pyrrol-2-yl]propane-1,3-dione (2b’):
A
CH2Cl2 solution (40 mL) of 2-(3,5-bis-TEG-phenyl)pyrrole (918.1 mg,
1.96 mmol) was treated at 08C with malonyl chloride (138.4 mg,
0.98 mmol) and stirred for 2.5 h at the same temperature. After confirma-
tion of the consumption of the starting pyrrole by TLC analysis, the reac-
tion mixture was chromatographed over silica gel columns (Wakogel C-
300, 3% MeOH/CH2Cl2 and 4.5% MeOH/EtOAc) to afford 2b’
(603.4 mg, 61%) as a pale yellow oil. Rf =0.29 (5% MeOH/CH2Cl2).
1H NMR (600 MHz, CDCl3, 208C; diketone 2b’ is obtained as a mixture
of keto and enol tautomers in the ratio of 1:0.29): d (keto form)=9.70
(br, 2H; NH), 7.12 (m, 2H; pyrrole-H), 6.74 (m, 4H; Ar-H), 6.54 (m,
2H; pyrrole-H), 6.47 (m, 2H; Ar-H), 4.23 (s, 2H; CH2), 4.17–3.55 (m,
48H; OCH2), 3.37 ppm (s, 12H; OCH3); d (enol form)=16.65 (br, 1H;
OH), 9.57 (s, 2H; NH), 6.94 (m, 2H; pyrrole-H), 6.76 (m, 4H; Ar-H),
6.58 (m, 2H; pyrrole-H), 6.45 (m, 2H; Ar-H), 6.36 (s, 1H; CH), 4.17–
3.55 (m, 48H; OCH2), 3.38 ppm (s, 12H; OCH3); FAB-MS: m/z (%):
calcd for C51H74N2O18: 1002.4932 [M]+; found: 1002.4 (100).
1,3-Bis[5-(3,4,5-tris-TEG-phenyl)pyrrol-2-yl]propane-1,3-dione (2c’):
A
1-tert-Butoxycarbonyl-2-(3,4,5-tris-HEG-phenyl)pyrrole and 2-(3,4,5-tris-
HEG-phenyl)pyrrole: A solution of Na2CO3 (585.6 mg, 5.5 mmol) in
water (3 mL) was added at room temperature under nitrogen to a solu-
tion of 5-bromo-1,2,3-tris-HEG-benzene (1.760 g, 1.69 mmol), 1-tert-bu-
toxycarbonylpyrrole-2-boronic acid (473.9 mg, 2.25 mmol), and tetrakis-
(triphenylphosphine)palladium(0) (88.0 mg, 0.076 mmol) in 1,2-dime-
thoxyethane (35 mL). The mixture was heated at reflux for 4.5 h, allowed
to cool, and then partitioned between water and CH2Cl2. The combined
extracts were dried over anhydrous MgSO4 and concentrated to give an
oil. The residue was then chromatographed over silica gel (Wakogel C-
300, 5% MeOH/CH2Cl2) to give 1-tert-butoxycarbonyl-2-(3,4,5-tris-HEG-
phenyl)pyrrole (1.548 g, 81%) as a colorless oil. Rf =0.46 (10% MeOH/
CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=7.31 (m, 1H; pyrrole-
H), 6.56 (s, 2H; Ar-H), 6.20 (m, 1H; pyrrole-H), 6.14 (m, 1H; pyrrole-
H), 4.13–4.15 (m, 6H; OCH2), 3.84 (m, 4H; OCH2), 3.79 (m, 2H;
OCH2), 3.73–3.70 (m, 6H; OCH2), 3.67–3.63 (m, 6H; OCH2), 3.55–3.54
(m, 6H; OCH2), 3.38 (s, 3H; OCH3), 3.37 (s, 6H; OCH3), 1.36 ppm (s,
9H; Boc); FAB-MS: m/z (%): calcd for C54H95NO23: 1125.63 [M]+;
found: 1125.6 (100), 1126.5 (74). The product 1-tert-butoxycarbonyl-2-
(3,4,5-tris-HEG-phenyl)pyrrole (1.55 g, 1.37 mmol) was heated at 1608C
for 20 min and then allowed to cool. The residue was then chromato-
graphed over silica gel (Wakogel C-300, 6% MeOH/CH2Cl2) to give 2-
(3,4,5-tris-HEG-phenyl)pyrrole as a colorless oil (1310.3 mg, 93%). Rf =
0.37 (10% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=9.37
(br, 1H; NH), 6.85 (s, 2H; Ar-H), 6.82 (m, 1H; pyrrole-H), 6.40 (m, 1H;
pyrrole-H), 6.23 (m, 1H; pyrrole-H), 4.23 (m, 4H; OCH2), 4.16 (m, 2H;
OCH2), 3.83 (m, 4H; OCH2), 3.79 (m, 2H; OCH2), 3.72–3.61 (m, 54H;
OCH2), 3.54–3.52 (m, 6H; OCH2), 3.37 (s, 3H; OCH3), 3.36 ppm (s, 6H;
OCH3); FAB-MS: m/z (%): calcd for C49H87NO21: 1025.58 [M]+; found:
1025.7 (100), 1026.8 (76).
CH2Cl2 solution (35 mL) of 2-(3,4,5-tris-TEG-phenyl)pyrrole (1.132 g,
1.80 mmol) was treated at 08C with malonyl chloride (126.8 mg,
0.90 mmol) and stirred for 3 h at the same temperature. After confirma-
tion of the consumption of the starting pyrrole by TLC analysis, the reac-
tion mixture was chromatographed over silica gel columns (Wakogel C-
300, 3.6% MeOH/CH2Cl2 and 12% MeOH/EtOAc) to afford 2c’
(668.3 mg, 56%) as a pale yellow oil. Rf =0.24 (5% MeOH/CH2Cl2);
1H NMR (600 MHz, CDCl3, 208C; diketone 2c’ is obtained as a mixture
of keto and enol tautomers in the ratio of 1:0.28): d (keto form)=9.90
(br, 2H; NH), 7.11 (m, 2H; pyrrole-H), 6.85 (s, 4H; Ar-H), 6.49 (m, 2H;
pyrrole-H), 4.25–3.53 (m, 72H; OCH2), 3.36 ppm (m, 18H; OCH3);
d (enol form)=16.74 (s, 1H; OH), 9.79 (br, 2H; NH), 6.95 (m, 2H; pyr-
role-H), 6.88 (s, 4H; Ar-H), 6.53 (m, 2H; pyrrole-H), 6.38 (s, 1H; CH),
4.25–3.53 (m, 72H; OCH2), 3.37 ppm (m, 18H; OCH3); ESI-TOF-MS:
m/z (%): calcd for C65H101N2O26: 1325.66 [MÀH]À; found: 1325.7 (100),
1326.7 (64).
1,3-Bis[5-(3,4,5-tris-HEG-phenyl)pyrrol-2-yl]propane-1,3-dione (2d’):
A
CH2Cl2 solution (12 mL) of 2-(3,4,5-tris-HEG-phenyl)pyrrole (640.7 mg,
0.62 mmol) was treated at 08C with malonyl chloride (52.7 mg,
0.38 mmol) and stirred for 1.5 h at the same temperature. After confirma-
tion of the consumption of the starting pyrrole by TLC analysis, the reac-
tion mixture was purified by silica gel flash column chromatography
(5.5% MeOH/CH2Cl2) over silica gel columns to afford 2d’ (158.1 mg,
24%) as a pale yellow oil. Rf =0.37 (10% MeOH/CH2Cl2); 1H NMR
(600 MHz, CDCl3, 208C; diketone 2d’ is obtained as a mixture of keto
and enol tautomers in the ratio of 1:0.45): d (keto form)=10.24 (br, 2H;
NH), 7.10 (m, 2H; pyrrole-H), 6.91 (s, 4H; Ar-H), 6.48 (m, 2H; pyrrole-
H), 4.25 (s, 2H; CH2), 4.23–3.52 (m, 144H; OCH2), 3.35 ppm (m, 18H;
OCH3); d (enol form)=10.08 (br, 2H; NH), 6.96 (m, 2H; pyrrole-H),
Chem. Eur. J. 2009, 15, 3706 – 3719
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3715

H. Maeda et al.
6.94 (s, 4H; Ar-H), 6.52 (m, 2H; pyrrole-H), 6.44 (s, 1H; CH), 4.23–3.52
(m, 144H; OCH2), 3.36 (m, 18H; OCH3); ESI-TOF-MS: m/z (%): calcd
for C101H173N2O44: 2118.14 [MÀH]À; found: 2118.1 (93), 2119.1 (100).
ratio of 1:0.37): d (keto form)=9.81 (br, 1H; NH), 9.42 (br, 1H; NH),
7.12 (m, 2H; pyrrole-H), 6.85 (s, 2H; Ar-H), 6.71 (s, 2H; Ar-H), 6.49 (m,
2H; pyrrole-H), 4.23 (s, 2H; CH2) 4.25–4.17 (m, 6H; OCH2), 4.04–3.95
(m, 6H; OCH2C7H15), 3.87 (m, 4H; OCH2), 3.80 (m, 2H; OCH2), 3.76–
3.62 (m, 18H; OCH2), 3.56–3.53 (m, 6H; OCH2), 3.38–3.35 (m, 9H;
OCH3), 1.85–1.72 (m, 6H; OCH2CH2C14H29), 1.50–1.45 (m, 6H;
OC2H4CH2C13H27), 1.38–1.25 (m, 72H; OC3H6C12H24CH3), 0.88 ppm (m,
9H; CH3); d (enol form)=16.75 (s, 1H; OH), 9.70 (br, 1H; NH), 9.33
(br, 1H; NH), 6.95 (m, 2H; pyrrole-H), 6.87 (s, 2H; Ar-H), 6.74 (s, 2H;
Ar-H), 6.53 (m, 2H; pyrrole-H), 6.37 (s, 1H; CH), 4.25–4.17 (m, 6H;
OCH2), 4.04–3.95 (m, 6H; OCH2C7H15), 3.87 (m, 4H; OCH2), 3.80 (m,
2H; OCH2), 3.76–3.62 (m, 18H; OCH2), 3.56–3.53 (m, 6H; OCH2), 3.38–
3.35 (m, 9H; OCH3), 1.85–1.72 (m, 6H; OCH2CH2C14H29), 1.50–1.45 (m,
6H; OC2H4CH2C13H27), 1.38–1.25 (m, 72H; OC3H6C12H24CH3), 0.88 ppm
(m, 9H; CH3); ESI-TOF-MS: m/z (%): calcd for C92H155N2O17: 1560.13
[MÀH]À; found: 1560.1 (93), 1561.1 (100).
1-[5-(3,4,5-Trioctyloxyphenyl)pyrrol-2-yl]-3-[5-(3,4,5-tris-TEG-phenyl)-
pyrrol-2-yl]propane-1,3-dione (3a’): A CH2Cl2 solution (15 mL) of 2-
(3,4,5-tris-TEG-phenyl)pyrrole (241.9 mg, 0.38 mmol) and 2-(3,4,5-trioc-
tyloxyphenyl)pyrrole (201.0 mg, 0.38 mmol) was treated at room temper-
ature with malonyl chloride (56.5 mg, 0.40 mmol) and stirred at the same
temperature for 1 h. After confirmation of the consumption of the start-
ing pyrrole by TLC analysis, the reaction mixture was chromatographed
over silica gel columns (Wakogel C-300, 2.5% MeOH/CH2Cl2) to afford
3a’ (93.4 mg, 20%) as a pale yellow oil. Rf =0.28 (5% MeOH/CH2Cl2);
1H NMR (600 MHz, CDCl3, 208C; diketone 3a’ is obtained as a mixture
of keto and enol tautomers in the ratio of 1:0.50): d (keto form)=9.87
(br, 1H; NH), 9.44 (br, 1H; NH), 7.12 (m, 2H; pyrrole-H), 6.85 (s, 2H;
Ar-H), 6.72 (s, 2H; Ar-H), 6.49 (m, 2H; pyrrole-H), 4.25–4.17 (m, 6H;
OCH2), 4.04–3.96 (m, 6H; OCH2C7H15), 3.88–3.85 (m, 4H; OCH2), 3.81–
3.79 (m, 2H; OCH2), 3.76–3.62 (m, 18H; OCH2), 3.56–3.53 (m, 6H;
OCH2), 3.38–3.35 (m, 9H; OCH3), 1.86–1.72 (m, 6H; OCH2CH2C6H13),
1-[5-(3,4,5-Trihexadecyloxyphenyl)pyrrol-2-yl]-3-[5-(3,4,5-tris-HEG-phe-
nyl)pyrrol-2-yl]propane-1,3-dione (3d’): A CH2Cl2 solution (20 mL) of 2-
(3,4,5-tris-TEG-phenyl)pyrrole (236.6 mg, 0.27 mmol) and 2-(3,4,5-trihexa-
decyloxyphenyl)pyrrole (280.6 mg, 0.27 mmol) was treated at room tem-
perature with malonyl chloride (42.3 mg, 0.30 mmol) and stirred at the
same temperature for 2 h. After confirmation of the consumption of the
starting pyrrole by TLC analysis, the reaction mixture was chromato-
graphed over silica gel flash columns (5.5% MeOH/CH2Cl2) to afford
3d’ (28.7 mg, 5%) as a pale yellow oil. Rf =0.30 (10% MeOH/CH2Cl2);
1H NMR (600 MHz, CDCl3, 208C; diketone 3d’ is obtained as a mixture
of keto and enol tautomers in the ratio of 1:0.35): d (keto form)=10.18
(br, 1H; NH), 9.58 (br, 1H; NH), 7.11 (m, 2H; pyrrole-H), 6.91 (s, 2H;
Ar-H), 6.74 (s, 2H; Ar-H), 6.49 (m, 2H; pyrrole-H), 4.26–4.22 (m, 4H;
OCH2), 4.19–4.17 (m, 2H; OCH2), 4.04–3.95 (m, 6H; OCH2C15H31),
3.88–3.85 (m, 4H; OCH2), 3.81–3.78 (m, 2H; OCH2), 3.74–3.61 (m, 54H;
OCH2), 3.54–3.52 (m, 6H; OCH2), 3.36–3.35 (m, 9H; OCH3), 1.84–1.72
(m, 6H; OCH2CH2C14H29), 1.50–1.45 (m, 6H; OC2H4CH2C13H27), 1.38–
1.25 (m, 72H; CH2), 0.88 ppm (m, 9H; CH3); d (enol form)=16.70 (s,
1H; OH), 10.05 (br, 1H; NH), 9.43 (br, 1H; NH), 6.96 (m, 2H; pyrrole-
H), 6.94 (s, 2H; Ar-H), 6.75 (s, 2H; Ar-H), 6.53 (m, 2H; pyrrole-H), 6.40
(s, 1H; CH), 4.26–4.22 (m, 4H; OCH2), 4.19–4.17 (m, 2H; OCH2), 4.04–
3.95 (m, 6H; OCH2C15H31), 3.88–3.85 (m, 4H; OCH2), 3.81–3.78 (m, 2H;
OCH2), 3.74–3.61 (m, 54H; OCH2), 3.54–3.52 (m, 6H; OCH2), 3.36–3.35
(m, 9H; OCH3), 1.84–1.72 (m, 6H; OCH2CH2C14H29), 1.50–1.45 (m, 6H;
OC2H4CH2C13H27), 1.38–1.25 (m, 72H; CH2), 0.88 ppm (m, 9H; CH3);
1.50–1.47
(m,
6H;
OC2H4CH2C5H11),
1.36–1.28
(m,
24H;
OC3H6C4H8CH3), 0.88 ppm (m, 9H; CH3); d (enol form)=16.75 (s, 1H;
OH), 9.76 (br, 1H; NH), 9.34 (br, 1H; NH), 6.95 (m, 2H; pyrrole-H),
6.88 (s, 2H; Ar-H), 6.74 (s, 2H; Ar-H), 6.53 (m, 2H; pyrrole-H), 6.37 (s,
1H; CH), 4.25–4.17 (m, 6H; OCH2), 4.04–3.96 (m, 6H; OCH2C7H15),
3.88–3.85 (m, 4H; OCH2), 3.81–3.79 (m, 2H; OCH2), 3.76–3.62 (m, 18H;
OCH2), 3.38–3.35 (m, 9H; OCH3), 3.37 (s, 6H; OCH3), 1.86–1.72 (m,
6H; OCH2CH2C6H13), 1.50–1.47 (m, 6H; OC2H4CH2C5H11), 1.36–1.28
(m, 24H; OC3H6C4H8CH3), 0.88 ppm (m, 9H; CH3); ESI-TOF-MS: m/z
(%): calcd for C68H107N2O17: 1223.76 [MÀH]À; found: 1223.8 (100),
1224.8 (72).
1-[5-(3,4,5-Trioctyloxyphenyl)pyrrol-2-yl]-3-[5-(3,4,5-tris-HEG-phenyl)-
pyrrol-2-yl]propane-1,3-dione (3b’): A CH2Cl2 solution (11 mL) of 2-
(3,4,5-tris-HEG-phenyl)pyrrole (279.6 mg, 0.27 mmol) and 2-(3,4,5-trioc-
tyloxyphenyl)pyrrole (142.9 mg, 0.27 mmol) was treated at room temper-
ature with malonyl chloride (41.7 mg, 0.30 mmol) and stirred at the same
temperature for 1 h. After confirmation of the consumption of the start-
ing pyrrole by TLC analysis, the reaction mixture was chromatographed
over silica gel columns (Wakogel C-300, 4.5% MeOH/CH2Cl2) to afford
3b’ (129.4 mg, 29%) as a pale yellow oil. Rf =0.37 (10% MeOH/CH2Cl2).
1H NMR (600 MHz, CDCl3, 208C; diketone 3b’ is obtained as a mixture
of keto and enol tautomers in the ratio of 1:0.36): d (keto form)=9.94
(br, 1H; NH), 9.48 (br, 1H; NH), 7.12 (m, 2H; pyrrole-H), 6.89 (s, 2H;
Ar-H), 6.73 (s, 2H; Ar-H), 6.49 (m, 2H; pyrrole-H), 4.22 (s, 2H; CH2)
4.26–4.17 (m, 6H; OCH2), 4.04–3.88 (m, 6H; OCH2C7H15), 3.86 (m, 4H;
OCH2), 3.80 (m, 2H; OCH2), 3.73–3.61 (m, 54H; OCH2), 3.54–3.52 (m,
6H; OCH2), 3.36–3.35 (m, 9H; OCH3), 1.86–1.72 (m, 6H;
OCH2CH2C6H13), 1.51–1.46 (m, 6H; OC2H4CH2C5H11), 1.38–1.25 (m,
24H; OC3H6C4H8CH3), 0.90–0.87 ppm (m, 9H; CH3); d (enol form)=
16.74 (s, 1H; OH), 9.85 (br, 1H; NH), 9.37 (br, 1H; NH), 6.96 (m, 2H;
pyrrole-H), 6.92 (s, 2H; Ar-H), 6.74 (s, 2H; Ar-H), 6.53 (m, 2H; pyrrole-
H), 6.40 (s, 1H; CH), 4.26–4.17 (m, 6H; OCH2), 4.04–3.88 (m, 6H;
OCH2C7H15), 3.86 (m, 4H; OCH2), 3.80 (m, 2H; OCH2), 3.73–3.61 (m,
54H; OCH2), 3.54–3.52 (m, 6H; OCH2), 3.36–3.35 (m, 9H; OCH3), 1.86–
1.72 (m, 6H; OCH2CH2C6H13), 1.51–1.46 (m, 6H; OC2H4CH2C5H11),
1.38–1.25 (m, 24H; OC3H6C4H8CH3), 0.90–0.87 ppm (m, 9H; CH3); ESI-
TOF-MS: m/z (%): calcd for C86H143N2O26: 1619.99 [MÀH]À; found:
1620.0 (100), 1621.0 (96).
ESI-TOF-MS: m/z (%): calcd for
found: 1956.4 (87), 1957.4 (100).
C
110H191N2O26
:
1956.37 [MÀH]À;
BF2 complex of 2a’ (2a): BF3·OEt2 (139.6 mg, 0.98 mmol) was added to a
CH2Cl2 solution (7 mL) of diketone 2a’ (21.8 mg, 0.032 mmol), and the
system was stirred at room temperature for 30 min. Silica gel column
chromatography (Wakogel C-300, 2% MeOH/CH2Cl2) and crystallization
from CH2Cl2/hexane afforded 2a (10.6 mg, 45%) as a red solid. Rf =0.31
(5% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3, 208C): d=9.58 (br,
2H; NH), 7.56 (m, 4H; Ar-H), 7.19 (m, 2H; pyrrole-H), 7.00 (m, 4H;
Ar-H), 6.63 (m, 2H; pyrrole-H), 6.49 (s, 1H; CH), 4.20–3.56 (m, 24H;
OCH2), 3.39 ppm (s, 6H; OCH3); UV/Vis (CH2Cl2): lmax (eꢃ10À5)=
519.0 nm (1.19mÀ1 cmÀ1); FAB-MS: m/z (%): calcd for C37H45BF2N2O10
726.31 [M]+; found: 726.3 (100+), 727.3 (64).
:
BF2 complex of 2b’ (2b): BF3·OEt2 (23.2 mg, 0.16 mmol) was added to a
CH2ClCH2Cl solution (30 mL) of diketone 2b’ (108.5 mg, 0.11 mmol),
and the system was stirred at reflux temperature for 15 min. The reaction
mixture was first separated on a silica gel short column (Wakogel C-300,
5% MeOH/CH2Cl2) to eliminate acidic compounds. Purification by silica
gel flash column chromatography (4.5% MeOH/CH2Cl2) and on an alu-
mina short column (1% MeOH/CH2Cl2) then afforded 2b (103.2 mg,
91%) as a red oil. Rf =0.47 (10% MeOH/CH2Cl2); 1H NMR (600 MHz,
CDCl3, 208C): d=10.11 (br, 2H; NH), 7.18 (m, 2H; pyrrole-H), 6.85 (m,
4H; Ar-H), 6.67 (m, 2H; pyrrole-H), 6.52 (s, 1H; CH), 6.49 (m, 2H; Ar-
H), 4.20–3.56 (m, 48H; OCH2), 3.37 ppm (s, 12H; OCH3); UV/Vis
(CH2Cl2): lmax (eꢃ10À5)=503.0 nm (1.22mÀ1 cmÀ1); FAB-MS: m/z (%):
calcd for C51H73BF2N2O18: 1050.49 [M]+; found: 1050.5 (100), 1051.5 (88).
1-[5-(3,4,5-Trihexadecyloxyphenyl)pyrrol-2-yl]-3-[5-(3,4,5-tris-TEG-phe-
nyl)pyrrol-2-yl]propane-1,3-dione (3c’): A CH2Cl2 solution (11 mL) of 2-
(3,4,5-tris-TEG-phenyl)pyrrole (179.3 mg, 0.29 mmol) and 2-(3,4,5-trihexa-
decyloxyphenyl)pyrrole (246.3 mg, 0.29 mmol) was treated at room tem-
perature with malonyl chloride (44.2 mg, 0.31 mmol) and stirred at the
same temperature for 1 h. After confirmation of the consumption of the
starting pyrrole by TLC analysis, the reaction mixture was chromato-
graphed over silica gel columns (Wakogel C-300, 2.5% MeOH/CH2Cl2
and 5% MeOH/EtOAc) to afford 3c’ (120.8 mg, 27%) as a pale yellow
1
oil. Rf =0.23 (5% MeOH/CH2Cl2); H NMR (600 MHz, CDCl3, 208C; di-
ketone 3c’ is obtained as a mixture of keto and enol tautomers in the
3716
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3706 – 3719

Solvent-Assisted Organized Structures
FULL PAPER
BF2 complex of 2c’ (2c): BF3·OEt2 (167.5 mg, 1.4 mmol) was added to a
CH2Cl2 solution (30 mL) of diketone 2c’ (123.9 mg, 0.093 mmol), and the
system was stirred at 08C for 10 min. The reaction mixture was first sepa-
rated on a silica gel short column (Wakogel C-300, 7% MeOH/CH2Cl2)
to eliminate acidic impurities. Purification by silica gel column flash chro-
matography (6.5% MeOH/CH2Cl2) and on an alumina short column
(1% MeOH/CH2Cl2) then afforded 2c (63.5 mg, 49%) as a red oil. Rf =
BF2 complex of 3c’ (3c): BF3·OEt2 (14.7 mg, 0.10 mmol) was added to a
CH2ClCH2Cl solution (22 mL) of diketone 3c’ (106.9 mg, 0.068 mmol),
and the system was stirred at reflux temperature for 10 min. The reaction
mixture was first separated on a silica gel short column (Wakogel C-300,
2.5% MeOH/CH2Cl2) to eliminate acidic entities. Purification by silica
gel flash column chromatography (2.5% MeOH/CH2Cl2) and on an alu-
mina short column (1% MeOH/CH2Cl2) then afforded 3c (90.0 mg,
82%) as a red solid. Rf =0.33 (5% MeOH/CH2Cl2); 1H NMR (600 MHz,
CDCl3, 208C): d=10.44 (br, 1H; NH), 9.50 (br, 1H; NH), 7.20 (m, 1H;
pyrrole-H), 7.19 (m, 1H; pyrrole-H), 7.01 (s, 2H; Ar-H), 6.78 (s, 2H; Ar-
H), 6.65–6.63 (m, 2H; pyrrole-H), 6.53 (s, 1H; CH), 4.27 (m, 4H;
OCH2), 4.21 (m, 2H; OCH2), 4.06 (t, J=6.6 Hz, 4H; OCH2C15H31), 4.00
(t, J=6.6 Hz, 2H; OCH2C15H31), 3.88 (t, J=4.8 Hz, 4H; OCH2), 3.81 (t,
J=4.8 Hz, 2H; OCH2), 3.76 (m, 4H; OCH2), 3.72–3.68 (m, 10H; OCH2),
3.63 (m, 4H; OCH2), 3.59–3.55 (m, 6H; OCH2), 3.40 (s, 3H; OCH3), 3.35
(s, 6H; OCH3), 1.85 (m, 4H; OCH2CH2C14H29), 1.76 (m, 2H;
OCH2CH2C14H29), 1.53–1.46 (m, 6H; OC2H4CH2C13H27), 1.40–1.26 (m,
72H; OC3H6C12H24CH3), 0.89–0.86 ppm (m, 9H; OC15H30CH3); UV/Vis
(CH2Cl2): lmax (eꢃ10À5)=519.0 nm (1.28mÀ1 cmÀ1); ESI-TOF-MS: m/z
(%): calcd for C92H154BF2N2O17: 1608.13 [MÀH]À; found: 1608.1 (100),
1609.1 (62).
1
0.37 (10% MeOH/CH2Cl2); H NMR (600 MHz, CDCl3, 208C): d=10.43
(br, 2H; NH), 7.19 (m, 2H; pyrrole-H), 7.01 (s, 4H; Ar-H), 6.63 (m, 2H;
pyrrole-H), 6.55 (s, 1H; CH), 4.28–3.55 (m, 72H; OCH2), 3.39 (s, 6H;
OCH3), 3.34 ppm (s, 12H; OCH3); UV/Vis (CH2Cl2): lmax (eꢃ10À5)=
517.0 nm (1.16mÀ1 cmÀ1); FAB-MS: m/z (%): calcd for C65H101BF2N2O26
1374.67 [M]+; found: 1374.7 (100).
:
BF2 complex of 2d’ (2d): BF3·OEt2 (37.2 mg, 0.26 mmol) was added to a
CH2Cl2 solution (7 mL) of diketone 2d’ (56.3 mg, 0.027 mmol), and the
system was stirred at 08C for 10 min. The reaction mixture was first sepa-
rated on a silica gel short column (Wakogel C-300, 6.5% MeOH/CH2Cl2)
to eliminate acidic entities. Purification by silica gel flash column chro-
matography (6.5% MeOH/CH2Cl2) and on an alumina short column
(1% MeOH/CH2Cl2) then afforded 2d (26.9 mg, 51%) as a red oil. Rf =
1
0.35 (10% MeOH/CH2Cl2); H NMR (600 MHz, CDCl3, 208C): d=10.81
BF2 complex of 3d’ (3d): BF3·OEt2 (3.2 mg, 0.022 mmol) was added to a
CH2ClCH2Cl solution (5 mL) of diketone 3d’ (28.7 mg, 0.015 mmol), and
the system was stirred at reflux temperature for 10 min. The reaction
mixture was first separated on a silica gel short column (Wakogel C-300,
5% MeOH/CH2Cl2) to eliminate acidic entities. Purification by silica gel
flash column chromatography (4.5% MeOH/CH2Cl2) and on an alumina
short column (1% MeOH/CH2Cl2) then afforded 3d (20.1 mg, 68%) as a
red oil. Rf =0.39 (10% MeOH/CH2Cl2); 1H NMR (600 MHz, CDCl3,
208C): d=10.88 (br, 1H; NH), 9.58 (br, 1H; NH), 7.22 (m, 1H; pyrrole-
H), 7.19 (m, 1H; pyrrole-H), 7.11 (s, 2H; Ar-H), 6.79 (s, 2H; Ar-H), 6.65
(m, 1H; pyrrole-H), 6.63 (m, 1H; pyrrole-H), 6.57 (s, 1H; CH), 4.29 (m,
4H; OCH2), 4.22 (m, 2H; OCH2), 4.06 (t, J=6.6 Hz, 4H; OCH2C15H31),
3.98 (t, J=6.6 Hz, 2H; OCH2C15H31), 3.88 (m, 4H; OCH2), 3.80 (m, 2H;
OCH2), 3.73 (m, 4H; OCH2), 3.70–3.57 (m, 50H; OCH2), 3.53–3.51 (m,
6H; OCH2), 3.34 (s, 9H; OCH3), 1.85 (m, 4H; OCH2CH2C14H29), 1.76
(m, 2H; OCH2CH2C14H29), 1.53–1.46 (m, 6H; OC2H4CH2C13H27), 1.39–
1.25 (m, 72H; OC3H6C12H24CH3), 0.89–0.86 ppm (m, 3H; OC15H30CH3);
UV/Vis (CH2Cl2): lmax (eꢃ10À5)=519.0 nm (1.18mÀ1 cmÀ1); ESI-TOF-
MS: m/z (%): calcd for C110H190BF2N2O26: 2004.37 [MÀH]À; found:
2004.4 (81), 2005.4 (100).
(br, 2H; NH), 7.21 (m, 2H; pyrrole-H), 7.09 (s, 4H; Ar-H), 6.64 (m, 2H;
pyrrole-H), 6.60 (s, 1H; CH), 4.29 (m, 8H; OCH2), 4.22 (m, 4H; OCH2),
3.88 (m, 8H; OCH2), 3.80 (m, 4H; OCH2), 3.74 (m, 8H; OCH2), 3.70–
3.60 (m, 100H; OCH2), 3.54–3.51 (m, 12H; OCH2), 3.35 (s, 18H; OCH3);
UV/Vis (CH2Cl2): lmax (eꢃ10À4)=518.0 nm (9.75mÀ1 cmÀ1); ESI-TOF-
MS: m/z (%): calcd for C101H172BF2N2O44: 2166.13 [MÀH]À; found:
2166.1 (100), 2167.1 (99).
BF2 complex of 3a’ (3a): BF3·OEt2 (15.8 mg, 0.11 mmol) was added to a
CH2ClCH2Cl solution (24 mL) of diketone 3a’ (90.2 mg, 0.074 mmol),
and the system was stirred at reflux temperature for 10 min. The reaction
mixture was first separated on a silica gel short column (Wakogel C-300,
2.5% MeOH/CH2Cl2) to eliminate acidic entities. Purification by silica
gel flash column chromatography (2.5% MeOH/CH2Cl2) and on an alu-
mina short column (1% MeOH/CH2Cl2) then afforded 3a (80.5 mg,
86%) as a red oil. Rf =0.28 (5% MeOH/CH2Cl2); 1H NMR (600 MHz,
CDCl3, 208C): d=10.50 (br, 1H; NH), 9.55 (br, 1H; NH), 7.21–7.18 (m,
2H; pyrrole-H), 7.01 (s, 2H; Ar-H), 6.79 (s, 2H; Ar-H), 6.65–6.63 (m,
2H; pyrrole-H), 6.53 (s, 1H; CH), 4.27 (m, 4H; OCH2), 4.21 (m, 2H;
OCH2), 4.06 (t, J=6.6 Hz, 4H; OCH2C7H15), 4.00 (t, J=6.6 Hz, 2H;
OCH2C7H15), 3.87 (m, 4H; OCH2), 3.80 (m, 2H; OCH2), 3.76 (m, 4H;
OCH2), 3.70–3.57 (m, 14H; OCH2), 3.58–3.55 (m, 6H; OCH2), 3.39 (s,
3H; OCH3), 3.34 (s, 6H; OCH3), 1.86 (m, 4H; OCH2CH2C6H13), 1.76 (m,
2H; OCH2CH2C6H13), 1.54–1.47 (m, 6H; OC2H4CH2C5H11), 1.40–1.27
(m, 24H; OC3H6C4H8CH3), 0.90–0.88 ppm (m, 3H; OC7H14CH3); UV/Vis
(CH2Cl2): lmax (eꢃ10À5)=519.0 nm (1.24mÀ1 cmÀ1); ESI-TOF-MS: m/z
(%): calcd for C68H106BF2N2O17: 1271.76 [MÀH]À; found: 1271.8 (100),
1272.8 (95).
Methods for DLS: DLS measurements were obtained with a Malvern
Zetasizer Nano-ZS differential light scattering instrument.
Cryogenic transmission electron microscopy (cryo-TEM): The cryogenic
transmission electron microscopy (cryo-TEM) experiments were per-
formed with thin films of aqueous solutions of amphiphilic molecule
(5 mL) transferred to a lacey supported grid. The thin aqueous films were
prepared under controlled temperature and humidity conditions (97–
99%) in a custom-built environmental chamber in order to prevent evap-
oration of water from sample solutions. Excess liquid was blotted with
filter paper (2–3 s), and the thin aqueous films were rapidly vitrified by
plunging them into liquid ethane (cooled by liquid nitrogen) at its freez-
ing point. The grid was transferred on a Gatan 626 cryoholder using a
cryo-transfer device. After that it was transferred to a JEM-2010 TEM
instrument. Direct imaging was carried out at a temperature of approxi-
mately À1758C and with a 120 kV accelerating voltage, by use of the
images acquired with a SC 1000 CCD camera (Gatan, Inc., Warrendale,
PA).
BF2 complex of 3b’ (3b): BF3·OEt2 (14.1 mg, 0.099 mmol) was added to a
CH2ClCH2Cl solution (21 mL) of diketone 3b’ (107.4 mg, 0.066 mmol),
and the system was stirred at reflux temperature for 10 min. The reaction
mixture was first separated on a small silica gel precolumn (Wakogel C-
300, 4.5% MeOH/CH2Cl2) to eliminate acidic entities. Purification by
silica gel flash column chromatography (4.5% MeOH/CH2Cl2) and on an
alumina short column (2% MeOH/CH2Cl2) then afforded 3b (100.9 mg,
91%) as a red oil. Rf =0.39 (10% MeOH/CH2Cl2); 1H NMR (600 MHz,
CDCl3, 208C): d=10.84 (br, 1H; NH), 9.54 (br, 1H; NH), 7.22 (m, 1H;
pyrrole-H), 7.19 (m, 1H; pyrrole-H), 7.12 (s, 2H; Ar-H), 6.79 (s, 2H; Ar-
H), 6.65 (m, 1H; pyrrole-H), 6.63 (m, 1H; pyrrole-H), 6.57 (s, 1H; CH),
4.30 (m, 4H; OCH2), 4.23 (m, 2H; OCH2), 4.06 (t, J=6.6 Hz, 4H;
OCH2C7H15), 4.00 (t, J=6.6 Hz, 2H; OCH2C7H15), 3.88 (m, 4H; OCH2),
3.81 (m, 2H; OCH2), 3.74 (m, 4H; OCH2), 3.69–3.58 (m, 50H; OCH2),
3.54–3.51 (m, 6H; OCH2), 3.34 (s, 6H; OCH3), 3.34 (s, 3H; OCH3), 1.85
(m, 4H; OCH2CH2C6H13), 1.76 (m, 2H; OCH2CH2C6H13), 1.52–1.47 (m,
6H; OC2H4CH2C5H11), 1.39–1.25 (m, 24H; OC3H6C4H8CH3), 0.90–
0.88 ppm (m, 9H; OC7H14CH3); UV/Vis (CH2Cl2): lmax (eꢃ10À5)=
519.5 nm (1.19mÀ1 cmÀ1); ESI-TOF-MS: m/z (%): calcd for
C86H142BF2N2O26: 1667.99 [MÀH]À; found: 16 68.0 (100), 1669.0 (81).
AM1 calculations: AM1 calculations for 2a–d and 3a were carried out
with the Gaussian 03 program[31] and either an HP Compaq dc5100 SFF
computer or an HPC P4Linux.
Acknowledgements
This work was supported by Grants-in-Aid for Young Scientists (B)
(No. 17750137) and Scientific Research in a Priority Area “Super-Hier-
Chem. Eur. J. 2009, 15, 3706 – 3719
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3717

H. Maeda et al.
archical Structures” (Nos. 18039038, 19022036) from the Ministry of
Education, Culture, Sports, Science and Technology (MEXT) and the
“Academic Frontier” Project for Private Universities; namely the match-
ing fund subsidy from the MEXT, 2003–2008, and the Ritsumeikan
Global Innovation Research Organization (R-GIRO) project (2008–
2013). The authors thank Prof. Tomohiro Miyatake, Ryukoku University,
for FAB-MS measurements, Prof. Hiroshi Shinokubo, Nagoya University,
and Prof. Atsuhiro Osuka, Kyoto University, for the ESI-TOF-MS meas-
urements, and Dr. Ryugo Tero, Institute for Molecular Science (IMS),
Prof. Munenori Numata, Kyoto Prefectural University, and Prof. Hitoshi
Tamiaki, Ritsumeikan University, for helpful discussions. E.L. and M.L.
thank the National Creative Research Initiative Program of the Korean
Ministry of Science and Technology, and E.L. acknowledges a fellowship
of the BK21 program from the Ministry of Education and Human Re-
sources Development.
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3718
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ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 3706 – 3719

Solvent-Assisted Organized Structures
FULL PAPER
[21] Solvent-aided control of func-
tional nanostructures have been
reported: a) J.-K. Kim, E. Lee,
M. Lee, Angew. Chem. 2006,
Table 1. Binding constants (Ka, mÀ1) of the PEG-substituted receptors 2a–d, 3a, and 3b, and reference 1a
[a]
with various anions as TBA salts in CH2Cl2
.
À
À
À
ClÀ
BrÀ
CH3CO2
H2PO4
HSO4
2a
2b
2c
2d
3a
20000
29000
47000
14000
37000
26000
30000
N
2000
2500
3300
1200
3800
2600
2800
G
290000
210000
200000
190000
780000
350000
210000
G
6200
200000
360000
360000
190000
300000
72000
N
210
1200
1900
440
710 ACHTUNGTRENNUNG
380 ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
118, 7353–7356; Angew. Chem.
Int. Ed. 2006, 45, 7195–7198;
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A. Kitamura, Angew. Chem.
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Chem. Int. Ed. 2007, 46, 8005–
8009.
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
3b
1a[b]
540
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UV/Vis absorption spectral changes between 60 and À608C.
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salts are summarized in Table 1. The absorption maxima lmax are
hardly shifted (less than 6 nm) by the binding anions, and the inten-
sity is moderately decreased. Further, the Ka values of 2a–d, 3a, and
3b for ClÀ and BrÀ are comparable to those of a-phenyl-substituted
1a. In contrast to the fairly suppressed Ka of 2a for H2PO4À, those
of 2b–d, 3a, and 3b are significantly enhanced as compared to those
of 2a as well as 1a, possibly due to the stabilization of the polarized
acidic moieties of the oxoanions by hydrogen-bonding-accepting
[30] C. N. Johnson, G. Stemp, N. Anand, S. C. Stephen, T. Gallagher,
Synlett 1998, 1025–1027.
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À
TEG substituents. Other oxoanions, CH3CO2 and HSO4À, have the
comparable or augmented Ka values depending on the receptors (in
the Supporting Information Figure S2–10); b) Ka values for 3c and d
have not been determined because they cannot form the assemblies
in aqueous solutions because of their insolubility.
[25] Similar to the stable assemblies in aqueous solutions, J-type (3a and
Received: October 17, 2008
Published online: February 16, 2009
3b) and H-type assemblies (3c,d) in hexane (1ꢃ10À5 m) appear to be
Chem. Eur. J. 2009, 15, 3706 – 3719
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3719