Assembly of a self-complementary monomer: Formation of supramolecular polymer networks and responsive gels

Article abstract of DOI:10.1002/chem.201002862

Self-complementary monomer 1, which combines a macrotricyclic polyether and two dibenzylammonium ions together, was synthesized, and its self-assembly into supramolecular polymer networks by host-guest interactions was studied. For the purpose of comparative study, two model molecules 2 and 3 were also prepared. It was found that model molecule 2 and dibenzylammonium ion 4 form a 1:2 complex in solution and in the solid state, which afforded a model system for the investigation of the assembly behavior of monomer 1. Consequently, the ¹H NMR spectrum of 1 in CD₃CN showed characteristic proton signals similar to the model system, which suggested that 1 self-assembles into a supramolecular polymer network. Formation of the supramolecular polymer was further evidenced by the MALDI-TOF MS spectrum, viscometry, and dynamic light-scattering (DLS) experiments. Moreover, it was found that the decomposition and re-formation of the supramolecular polymer could be chemically controlled by the use of triethylamine and trifluoroacetic acid. Interestingly, the supramolecular polymer forms an organogel both in CD₃CN and in 1:1 (v/v) CDCl₃/CD₃CN, and reversible thermo-and pH-induced gel-sol transitions were also found. The presented work will provide a new strategy for the construction of supramolecular polymers with specific structures and properties.

Full text of DOI:10.1002/chem.201002862

FULL PAPER
DOI: 10.1002/chem.201002862
Assembly of a Self-Complementary Monomer: Formation of Supramolecular
Polymer Networks and Responsive Gels
Yong-Sheng Su, Jia-Wei Liu, Yi Jiang, and Chuan-Feng Chen*[a]
1
Abstract: Self-complementary mono-
mer 1, which combines a macrotricyclic
polyether and two dibenzylammonium
ions together, was synthesized, and its
self-assembly into supramolecular poly-
mer networks by host–guest interac-
tions was studied. For the purpose of
comparative study, two model mole-
cules 2 and 3 were also prepared. It
was found that model molecule 2 and
dibenzylammonium ion 4 form a 1:2
complex in solution and in the solid
state, which afforded a model system
for the investigation of the assembly
behavior of monomer 1. Consequently,
the H NMR spectrum of 1 in CD3CN
showed characteristic proton signals
similar to the model system, which sug-
decomposition and re-formation of the
supramolecular polymer could be
chemically controlled by the use of
triethylamine and trifluoroacetic acid.
Interestingly, the supramolecular poly-
mer forms an organogel both in
CD3CN and in 1:1 (v/v) CDCl3/CD3CN,
and reversible thermo- and pH-induced
gel–sol transitions were also found.
The presented work will provide a new
strategy for the construction of supra-
molecular polymers with specific struc-
tures and properties.
gested that
1 self-assembles into a
supramolecular polymer network. For-
mation of the supramolecular polymer
was further evidenced by the MALDI-
TOF MS spectrum, viscometry, and dy-
namic light-scattering (DLS) experi-
ments. Moreover, it was found that the
Keywords: gels · molecular recog-
nition · polymers · self-assembly ·
supramolecular chemistry
Introduction
arm star poly(e-caprolactone) (PCL) and dibenzylammoni-
um-terminated two-arm star PCL. Although the integration
of molecular recognition with polymers results in the cross-
linkage of polymers for the formation of supramolecular
networks,[11] to the best of our knowledge, no supramolec-
ular polymer networks based on host–guest interactions of
self-complementary low-molecular-weight monomers with-
out polymeric backbones have hitherto been reported.
Recently, we reported a triptycene-derived macrotricyclic
polyether that contained two DB24C8 moieties, a powerful
host for complexation with different guests in different top-
ology.[12] In particular, we found that the macrocycle forms a
1:2 complex with 2 equiv dibenzylammonium ions
(Scheme 1a),[13] which inspired us to further design and syn-
thesize a self-complementary monomer 1 that combines a
macrotricyclic polyether (host units) and two dibenzylam-
monium ions (guest units) together (Scheme 1b). In this
paper, we report the synthesis of the monomer 1 and its
self-assembly into supramolecular polymer networks, which
represent the first example of supramolecular polymer net-
works formed by the assembly of self-complementary low-
molecular-weight monomers based on intermolecular host–
guest interactions. Interestingly, it was also found that the
supramolecular polymers showed gel properties in acetoni-
trile or acetonitrile/chloroform solution, and the supra-
molecular gels exhibited reversible thermo- and pH-induced
gel–sol transitions.
Supramolecular polymers,[1] a new field formed by the com-
bination of supramolecular chemistry and polymer science,
has currently attracted great interest. Consequently, chem-
ists have developed a variety of strategies for constructing
supramolecular polymers over the past years,[2,3] in which
host–guest interaction[4] has become one of the most impor-
tant and convenient approaches. In particular, crown ether
based molecular recognition has been successfully utilized in
the construction of supramolecular polymers with linear,[5]
star,[6] hyperbranched,[7] and dendronized[8] topologic struc-
tures. Some of the supramolecular polymers with specific
structures also form supramolecular gels,[9] which have re-
ceived significant and current attention because of their
wide potential application in materials science, drug deliv-
ery, and chemical sensors. Recently, Huang and Liu et al.[10]
reported the fabrication of responsive supramolecular gels
with a network structure based on the molecular recognition
between dibenzo[24]crown-8 (DB24C8)-terminated four-
[a] Y.-S. Su, J.-W. Liu, Y. Jiang, Prof. C.-F. Chen
Beijing National Laboratory for Molecular Sciences
CAS Key Laboratory of Molecular Recognition
and Function Institute of Chemistry
Chinese Academy of Sciences, Beijing 100190 (China)
Fax : (+86)10-62554449
E-mail: cchen@iccas.ac.cn
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201002862.
Chem. Eur. J. 2011, 17, 2435 – 2441
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2435

lar recognition moieties was produced in 95% yield by hy-
drolysis of precursor 9 with aqueous HPF6. Similarly, model
molecule 2 was prepared in 95% yield by the reaction of
acid anhydride 7 and aniline. Model molecule 3 was conven-
iently obtained by the reaction of 7 and 14, followed the hy-
drolysis by aqueous HPF6. Compound 2 was designed to
study its complexation with dibenzylammonium ions, and
subsequently afforded a model system for further study of
the assembly behavior of monomer 1. In the case of model
molecule 3, it has a similar structure to monomer 1 except
for the sterically hindered end groups in “guest moieties,”
which prevent its threading through the cavity of DB24C8
to form supramolecular polymers.
Complexation between model molecule 2 and guest 4: We
first tested the complexation between model molecule 2 and
dibenzylammonium ion 4 by NMR spectroscopy. As shown
1
in Figure 1b, the H NMR spectrum of a 1:2 mixture of 2
Scheme 1. a) Formation of the 1:2 complex between the macrotricyclic
host and dibenzylammonium salts; b) Structures and proton designations
of self-complementary monomer 1, model molecules 2 and 3, and guest
4.
1
Figure 1. Partial H NMR spectra (300 MHz, CDCl3/CD3CN=1:1, 298 K)
Results and Discussion
for a) guest 4; b) complexation between 2 and 2.0 equiv 4; and c) host 2.
c2 and c1 denote the 1:2 and 1:1 complex between the macrotricyclic
host and the dibenzylammonium ion, respectively. [2]0 =4.0 mm.
Synthesis of monomer 1 and model molecules 2 and 3: The
synthetic methodology for monomer 1 and model molecules
2 and 3 is depicted in Scheme 2. Firstly, we prepared diben-
zylammonium derivative 8 by the reaction of 4-nitrobenzal-
dehyde and benzylamine in toluene, reduction with NaBH4
in 1:1 THF/CH3OH, protection of the amine group, and
then catalytic hydrogenation in the presence of Pd/C. Under
the same conditions, compound 14 was prepared from 4-ni-
trobenzaldehyde and 3,5-dimethoxylbenzylamine. Starting
from anthracene derivative 10, macrotricyclic polyether 5
that contained two DB24C8 moieties was synthesized in
three steps according to a method described before.[14] Then,
Diels–Alder cycloaddition between 5 and dimethyl acetyle-
nedicarboxylate afforded the macrotricyclic derivative 6,
which was hydrolyzed, followed by heating it to reflux in
acetic anhydride to give acid anhydride 7. t-Butyloxycarbon-
yl (Boc)-protected precursor 9 was obtained by the reaction
of compound 7 with Boc-protected compound 8 (2 equiv).
Finally, monomer 1 that contained complementary molecu-
and 4, recorded in CDCl3/CD3CN (1:1 v/v), revealed the
characteristic complexed signals of both the host and the
guest. Since the complexation between host 2 and guest 4
showed a slow exchange process, the weak resonances for
the 1:1 complex and uncomplexed species in addition to
those strong resonances for 1:2 complex 2·42 were also
shown. It was found that the benzyl protons of guest 4 locat-
ed outside the cavity of host 2 showed downfield signals,
whereas the signals of the benzyl protons Ha, Hb, and Hc lo-
cated inside the cavity of 2 shifted upfield strikingly. In par-
ticular, the signal of the benzylic methylene proton Ha adja-
+
cent to the NH2 center exhibited a large downfield shift,
which was attributed to the hydrogen-bond interactions and
the deshielding effect of the aromatic rings in 2. Moreover,
an upfield shift for aromatic proton H1 of 2 and significant
changes in the chemical shifts of the protons in crown ether
2436
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2435 – 2441

Self-Complementary Monomer
FULL PAPER
Scheme 2. Schematic illustrations for the preparation of a) compound 8, b) compound 14, and c) monomer 1, and model molecules 2 and 3.
units were also observed. These observations were similar to
the cases of the complexation between the triptycene-de-
rived cylindrical macrotricyclic host and the dibenzylammo-
nium ions,[13] which suggested that an expected 1:2 complex
2·42 was formed in solution.
taxane-type complex in the solid state. Moreover, there ex-
isted multiple noncovalent interactions not only between
the host and the guest, but also between the two guests,
which played an important role in the formation of the 1:2
complex.[13] Formation of the expected 1:2 complex 2·42 pro-
vided a model system for further study of the assembly of 1
with the self-complementary moieties.
Formation of complex 2·42 was also confirmed by its ESI-
MS spectrum (see the Supporting Information). Conse-
quently, strong peaks at m/z 868.2 and 1538.5 for
À
À
[2·42À2PF6 ]2+ and [2·4ÀPF6 ]+, respectively, were found.
Further support for the formation of the complex 2·42 came
from its X-ray analysis (see the Experimental Section). As
shown in Figure 2, two dibenzylammonium ions were
threaded symmetrically through the center of the DB24C8
cavities of host 2, which resulted in a novel [3]pseudoro-
Assembly of self-complementary monomer 1: The self-as-
sembly of monomer 1 was first investigated by NMR spec-
1
troscopy. As shown in Figure 3a, the H NMR spectrum of
monomer 1 in CD3CN revealed characteristic complexed
signals between the host and the guest moieties. It was
found that the resonances for protons HA, HB, and HC of the
guest moieties strikingly shifted upfield, which indicated
that they were located inside the cavities of the host moiety.
Moreover, besides the resonances for 1:2 complexation be-
tween the macrotricyclic host moiety and the dibenzylam-
monium ions, the resonances for 1:1 complexed and uncom-
plexed species were also observed. All of these complexa-
tion behaviors of 1 were very similar to the case of the
model system described above. Since the short and rigid
linkers avoided self-recognition between the host and the
guest moieties of 1, it was thus implied that monomer 1 has
self-assembled into an expected supramolecular polymer
network based on the intermolecular host–guest interac-
Figure 2. a) Top view and b) side view of the crystal structure of complex
2·42. Solvent molecules and hydrogen atoms were omitted for clarity.
Chem. Eur. J. 2011, 17, 2435 – 2441
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2437

C.-F. Chen et al.
[1À2HPF6+Na]+) implied that monomer 1 showed strong
self-assembling abilities.
Viscometry provides a convenient and simple technique
to characterize the growth of supramolecular polymers with
increasing concentrations of the monomer. As shown in
Figure 4, the reduced viscosity of the acetonitrile solutions
Figure 3. Partial 1H NMR spectra (300 MHz, 298 K, 4 mm) of a) the
supramolecular polymer formed by the self-assembly of 1 in CD3CN;
b) complexation between 2 and 2.0 equiv 4 in CDCl3/CD3CN (1:1 v/v); c)
1 in [D6]DMSO; and d) 3 in CD3CN. c2 and c1 denote the 1:2 and 1:1
complex between the host moiety and the dibenzylammonium ion, re-
spectively.
Figure 4. Variation of reduced viscosities, VR (CH3CN, 298 K) as a func-
tion of the concentrations of the supramolecular polymers obtained by
&
the intermolecular host–guest complexation of monomer 1 ( ) and the
~
tions. Comparatively, we found that model molecule 3 only
showed the uncomplexed signals (Figure 3d) because the
sterically hindered end groups in the “guest moieties” pre-
vent their complexation. Since the complex between
DB24C8 and dibenzylammonium ions completely decom-
posed in DMSO,[13] it was found that monomer 1 showed
clear uncomplexed signals in [D6]DMSO (Figure 3c), which
also enabled us to obtain its characteristic NMR spectro-
scopic data.
The association and disassociation of the complex be-
tween DB24C8 and the dibenzylammonium ion can be
chemically controlled by the pH value,[12b] which inspired us
to further investigate the reversible formation of the supra-
molecular polymer from 1 by NMR spectroscopy (see the
Supporting Information). Consequently, we found that in
the presence of triethylamine (TEA), the characteristic
proton signals for the complexation between the host and
the guest moieties of monomer 1 completely disappeared,
which implied that the decomposition of the supramolecular
polymer networks occurred. Interestingly, it was found that
the addition of an excess amount of trifluoroacetic acid
(TFA) to the above system leads to the re-formation of the
supramolecular polymer.
The MALDI-TOF mass spectrum provided another piece
of evidence for the formation of the supramolecular poly-
mer (see the Supporting Information). As a result, the stron-
gest peak at m/z 3155 (100%) was shown, which corre-
sponds to the dimer [12À3HPF6ÀPF6]+. Moreover, a strong
peak at m/z 4879 for [13À4HPF6ÀPF6]+ was also observed,
which is consistent with the trimer. Although higher units in
the supramolecular polymer could not be found, probably
because of the restriction of their “fly” abilities and the ex-
perimental conditions, the higher intensities for the dimer
and trimer than the monomer (m/z 1599 for
model molecule 3 ( ).
of compound 1 varied exponentially with its concentrations,
thereby suggesting the formation of supramolecular polymer
networks. On the contrary, under the same conditions, the
reduced viscosity of 3 varied linearly with its concentrations
because of the sterically hindered end groups in the guest
moieties of 3 that prevented its thread through the cavity of
DB24C8. This observation indicated that no significant
physical entanglements or noncovalent intermolecular inter-
actions in 3 occurred, which is also in accordance with its
monomer structure.
Formation of the supramolecular polymer was further
supported by the dynamic light-scattering (DLS) experi-
ments (see the Supporting Information). As a result, a
15 mm solution of compound 1 in acetonitrile showed an
average hydrodynamic radius of 53.6 nm, which implied its
great aggregation. However, under the same conditions, no
aggregation could be detected for a solution of 3 per our ex-
pectation.
Formation of a responsive supramolecular gel: Interestingly,
it was found that the supramolecular polymer could form a
supramolecular gel at high concentrations. Consequently,
when an acetonitrile solution of 1 with a concentration
higher than 20 mm cooled from 80 to 258C, a transparent
supramolecular gel formed. Heating the gel resulted in re-
covery of the fluid solution again (Figure 5a). Formation of
the gel at lower temperatures could be ascribed to the resto-
ration of the supramolecular polymer from 1, which was par-
tially disrupted at elevated temperatures. Moreover, we also
found that the supramolecular gel could form at lower con-
centration (ꢀ5 mm) of 1 in 1:1 (v/v) CDCl3/CD3CN. Besides
2438
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2435 – 2441

Self-Complementary Monomer
FULL PAPER
the solution of the supramolecular polymer and model molecule 3 as a
function of concentrations were conducted using an Ubbelohde viscome-
ter at (25Æ0.05)8C. Hydrodynamic radii of solutions of 1 and 3 were
measured after solutions were filtered through a Teflon filter (pore size
0.2 mm) and using Wyatt DynaPro NanoStar dynamic light-scattering
(DLS) detectors.
Compound 11: K2CO3 (14.8 g, 107 mmol) was added to a stirred solution
of compound 10[15] (3.60 g, 13.3 mmol) and tri(ethylene glycol) monotosy-
late (17.8 g, 58.6 mmol) in dried CH3CN (300 mL). The reaction mixture
was stirred while heating to reflux for 24 h, cooled to ambient tempera-
ture, and then filtered. The filtrate was concentrated to give a residue,
which was dissolved in dried CH2Cl2 (250 mL), and 4-toluene sulfonyl
chloride (TsCl) (13.4 g, 70.3 mmol), Et3N (8.80 g, 87.1 mmol), and 4-di-
methylaminopyridine (DMAP) (0.360 g, 3.00 mmol), respectively, were
added to the solution. The reaction mixture was heated to reflux for 10 h,
cooled to ambient temperature, and then washed with HCl (2m) and
water successively. The organic layer was dried over anhydrous Na2SO4,
and then concentrated to afford a crude product, which was further puri-
fied by flash column chromatography with CH2Cl2 and CH3OH (3:1 v/v)
Figure 5. Supramolecular gel formed from 1 a) in CH3CN and its thermo-
induced gel–sol transitions, and b) in CDCl3/CD3CN (1:1 v/v) and its pH-
induced gel–sol transitions.
as eluent to afford 11 (12.2 g, 65%) as
a
colorless oil. 1H NMR
(300 MHz, CDCl3): d=7.77 (d, J=8.3 Hz, 8H), 7.45 (s, 4H), 7.28 (d, J=
8.3 Hz, 8H), 4.33 (t, J=4.9 Hz, 8H), 4.19–4.10 (m, 8H), 3.95 (t, J=
4.9 Hz, 8H), 3.77–3.56 (m, 24H), 2.89 (s, 6H), 2.38 ppm (s, 12H);
13C NMR (75 MHz, CDCl3): d=148.3, 144.8, 133.0, 129.8, 127.9, 126.1,
124.1, 105.1, 70.9, 70.9, 70.8, 69.7, 69.3, 68.7, 68.4, 21.6, 14.7 ppm;
MALDI-TOF MS: m/z: 1414.5 [M]+, 1437.5 [M+Na]+, 1453.6 [M+K]+;
elemental analysis calcd (%) for C68H86O24S4: C 57.69, H 6.12; found: C
57.49, H 6.30.
the temperature response, the gel also showed pH-induced
gel–sol transitions. As shown in Figure 5b, the gel could be
converted into a fluid solution upon the addition of TEA
(2.2 equiv), which resulted in the deprotonation of the di-
benzylammonium ions, and thus disrupted the supramolec-
ular polymer. It was also interestingly noted that the addi-
tion of TFA (about 2.4 equiv) to the above solution led to
the re-formation of the supramolecular gel. These complete-
ly reversible thermo- and pH-induced gel–sol transitions fur-
ther supported the formation of supramolecular polymer
networks, and also reflected their dynamic nature as typical
supramolecular systems.
Compound 5: A mixed solution of 11 (0.90 g, 3.3 mmol) and 10 (4.72 g,
3.33 mmol) in DMF (180 mL) was slowly added through a funnel into a
suspension that contained cesium carbonate (8.70 g, 26.7 mmol) in DMF
(130 mL) at 1108C over 36 h. After being stirred at 1108C for 3 d, the re-
action mixture was cooled to ambient temperature. Removal of DMF
under reduced pressure gave a residue, which was dissolved in chloro-
form and then filtered. The filtrate was washed with water twice, dried
over anhydrous Na2SO4, and concentrated to afford a crude product,
which was purified by flash column chromatography with CH2Cl2 and
methanol (80:1 v/v) as eluent to afford 5 (0.80 g, 24%) as a yellow solid.
M.p. >3008C; 1H NMR (300 MHz, CDCl3): d=6.83 (s, 8H), 4.38–4.17
(m, 8H), 4.19–3.95 (m, 32H), 3.94–3.74 (m, 8H), 2.30 ppm (s, 12H);
13C NMR (75 MHz, CDCl3): d=147.0, 125.0, 123.0, 103.0, 71.4, 69.02,
67.6, 14.1 ppm; MALDI-TOF MS: m/z: 996.6 [M]+, 1019.6 [M+Na]+,
1035.6 [M+K]+; elemental analysis calcd (%) for C56H68O16·0.5H2O: C
66.85, H 6.91; found: C 66.62, H 6.90.
Conclusion
In summary, we have synthesized a self-complementary mo-
nomer that combined a cylindrical macrotricyclic polyether
and two dibenzylammonium moieties together, and demon-
strated that the low-molecular-weight monomer self-assem-
bles into chemically controlled supramolecular polymer net-
works by intermolecular host–guest recognition. Interesting-
ly, we also found that the supramolecular polymers showed
gel properties in acetonitrile or acetonitrile/chloroform solu-
tions, and the supramolecular gels exhibit reversible thermo-
and pH-induced gel–sol transitions. We believe that the
work presented here can provide a strategy for the construc-
tion of the supramolecular polymers with specific structures
and properties.
Compound 6: Compound 5 (0.60 g, 0.60 mmol) was suspended in dimeth-
yl acetylenedicarboxylate (10 mL), which was heated at approximately
1808C for 30 min. Removal of volatile constituents under reduced pres-
sure gave a residue, which was washed with methanol. The collected
solid was recrystallized in CH2Cl2/CH3OH to afford 6 (0.68 g, 89%) as a
white solid. M.p. >3008C; 1H NMR (300 MHz, CDCl3): d=6.81 (s, 8H),
4.21–3.92 (m, 16H), 3.94–3.74 (m, 28H), 3.75–3.56 (m, 16H), 2.09 ppm (s,
12H); 13C NMR (75 MHz, CDCl3): d=166.1, 150.7, 145.7, 141.5, 109.2,
71.0, 69.9, 51.9, 49.1, 13.8 ppm; MALDI-TOF MS: m/z: 1303.5 [M+Na]+,
1319.5 [M+K]+; elemental analysis calcd (%) for C68H80O24: C 63.74, H
6.29; found: C 63.62, H 6.33.
Compound 6’: NaOH (0.31 g, 7.8 mmol) and H2O (2 mL) were added to
a suspension of 6 (0.50 g, 0.39 mmol) in CH3OH (30 mL). The reaction
mixture was heated at reflux for 10 h, and then concentrated under re-
duced pressure to give a residue, which was dissolved in H2O (15 mL).
After the solution was acidified to pH<3, the resultant precipitate was
filtered, washed with water, and then dried under vacuum to yield 6’
(0.48 g, 100%) as a white solid. M.p. >3008C; 1H NMR (300 MHz,
[D6]DMSO): d=12.87 (s, 4H), 6.87 (s, 8H), 3.98 (s, 16H), 3.79–3.42 (m,
32H), 2.06 ppm (s, 12H); 13C NMR (75 MHz, [D6]DMSO): d=167.0,
149.1, 144.9, 141.6, 108.9, 70.3, 69.1, 48.4, 13.6 ppm; MALDI-TOF MS:
m/z: 1247.7 [M+Na]+; elemental analysis calcd (%) for C64H72O24: C
62.74, H 5.92; found: C 62.69, H 5.85.
Experimental Section
General: Melting points, taken using an electrothermal melting point ap-
paratus, are uncorrected. The 1H and 13C NMR spectra were measured
using a Bruker DMX300 NMR spectrometer. 2D COSY experiments
were measured using a Bruker DMX600 NMR spectrometer. MALDI-
TOF MS were obtained using a Bruker BIFLEXIII mass spectrometer.
Elemental analyses were performed by the Analytical Laboratory of the
Institute of Chemistry, CAS. Measurements of the reduced viscosities of
Chem. Eur. J. 2011, 17, 2435 – 2441
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2439

C.-F. Chen et al.
Compound 9: A solution of 6’ (0.41 g, 0.33 mmol) in acetic anhydride
(10 mL) was heated to reflux under Ar for 4 h. Removal of the solvent
under reduced pressure gave 7 as a yellow solid, which was used without
further purification. Compound 12 (452 mg, 1.32 mmol) was dissolved in
1:1 (v/v) CH2Cl2/CH3OH (20 mL) and 10% Pd(C) (50 mg) was added.
The mixture was stirred under an H2 atmosphere for 3 h, filtered, and
then solvent was removed. The mixture of 7 and 8 obtained above was
dissolved in CHCl3 (15 mL) and stirred at 508C overnight, then solvent
was removed under reduced pressure. The residue was suspended in
acetic anhydride (15 mL), NaOAc (54 mg, 0.66 mmol) was added and
then stirred under N2 at 1008C for 3 h. Removal of solvent under re-
duced pressure gave a crude product, which was purified by flash column
chromatography with CH2Cl2 and methanol (60:1 v/v) as eluent, then re-
crystallized in CH2Cl2/Et2O to afford 9 (0.54 g, 92%) as a yellow solid.
M.p. >3008C; 1H NMR (300 MHz, CDCl3): d=7.38–7.09 (m, 18H), 6.90
(s, 8H), 4.45–4.25 (m, 8H), 4.18–4.07 (m, 8H), 4.07–3.97 (m, 8H), 3.91–
3.77 (m, 24H), 3.78–3.66 (m, 8H), 2.30 (s, 12H), 1.48 ppm (s, 18H);
13C NMR (75 MHz, CDCl3): d=165.3, 163.6, 163.4, 157.4, 155.9, 145.9,
141.6, 140.9, 137.9, 130.8, 128.5, 127.7, 127.3, 126.5, 109.7, 104.9, 86.0,
80.2, 71.1, 70.0, 69.9, 48.6, 28.4, 22.9, 12.1 ppm; MALDI-TOF MS: m/z:
1799.9 [M+Na]+; elemental analysis calcd (%) for C102H112N4O24·H2O: C
68.56, H 6.37, N 3.14; found: C 68.51, H 6.40, N 3.09.
3,5-dimethoxylbenzylamine
and
4-nitrobenzaldehyde.[16]
1H NMR
(300 MHz, CDCl3): d=8.18 (d, J=8.6 Hz, 2H), 7.43–7.29 (m, 2H), 6.38
(s, 2H), 6.33 (s, 1H), 4.63–4.19 (m, 4H), 3.77 (s, 6H), 1.62–1.32 ppm (m,
10H); 13C NMR (75 MHz, CDCl3): d=161.1, 155.8, 147.2, 145.8, 139.8,
128.4, 127.8, 123.8, 105.9, 105.4, 99.2, 80.7, 55.3, 50.3, 49.3, 48.9, 28.4 ppm;
ESI-MS: m/z: 425.2 [M+Na]+; elemental analysis calcd (%) for
C21H26N2O6: C 62.67, H 6.51, N 6.96; found: C 62.61, H 6.49, N 6.79.
Compound 15: According to a similar procedure for the synthesis of 9,
compound 15 as a yellow solid was synthesized in 92% yield by the reac-
tion of acid anhydride 7 and compound 14 (obtained from the reduction
of 13, and used without further purification). M.p. >3008C; 1H NMR
(300 MHz, CDCl3): d=7.33–7.07 (m, 8H), 6.90 (s, 8H), 6.35 (s, 6H),
4.46–4.19 (m, 8H), 4.18–3.95 (m, 16H), 3.95–3.59 (m, 44H), 2.30 (s,
12H), 1.47 ppm (s, 18H); 13C NMR (75 MHz, CDCl3): d=165.3, 161.0,
157.4, 155.9, 145.8, 141.6, 140.4, 130.8, 128.6, 127.8, 126.5, 109.7, 105.7,
105.3, 99.3, 80.2, 71.1, 70.0, 69.9, 55.3, 49.4, 48.6, 28.4, 12.1 ppm; MALDI-
TOF MS: m/z: 1919.9 [M+Na]+, 1936.0 [M+K]+; elemental analysis
calcd (%) for C106H120N4O28: C 67.07, H 6.37, N 2.95; found: C 67.35, H
6.40, N 3.06.
Compound 3: According to a similar procedure for the synthesis of 1,
compound 3 as a yellow solid was obtained in 93% yield from 15. M.p.
>3008C; 1H NMR (300 MHz, CD3CN): d=7.45 (d, J=8.2 Hz, 4H), 7.26
(d, J=8.2 Hz, 4H), 7.00 (s, 8H), 6.61 (d, J=2.0 Hz, 4H), 6.57 (d, J=
2.0 Hz, 2H), 4.22–4.12 (m, 8H), 4.12–3.96 (m, 16H), 3.81 (s, 12H), 3.78–
3.53 (m, 32H), 2.33 ppm (s, 12H); 13C NMR (75 MHz, CD3CN): d=
164.8, 161.0, 157.2, 145.1, 141.3, 133.0, 132.6, 130.3, 129.5, 127.0, 117.0,
109.2, 107.4, 100.7, 70.3, 69.3, 69.1, 54.9, 51.3, 50.7, 48.4, 11.3 ppm;
MALDI-TOF MS: m/z: 1720.8 [MÀ2HPF6+Na]+; elemental analysis
calcd (%) for C96H106F12N4O24P2·3H2O: C 56.41, H 5.52, N 2.74; found: C
56.40, H 5.52, N 2.93.
Monomer 1: In a suspension of 9 (0.20 g, 0.11 mmol) in CH3CN (15 mL),
an excess amount of HPF6 (0.5 mL) was added and stirred at 08C for 1 h.
Removal of the solvent under reduced pressure gave a residue, which
was washed with water. The solid was collected and dried under vacuum
to yield pure 1 (195 mg, 95%) as a yellow solid. M.p. >3008C; 1H NMR
(300 MHz, DMSO): d=9.06 (s, 4H), 7.64–7.38 (m, 14H), 7.31 (d, J=
8.3 Hz, 4H), 6.98 (s, 8H), 4.23–4.12 (m, 8H), 4.00 (s, 16H), 3.84–3.41 (m,
32H), 2.25 ppm (s, 12H); 13C NMR (75 MHz, DMSO): d=164.7, 164.3,
156.8, 149.4, 145.1, 143.7, 141.2, 139.5, 132.2, 131.8, 130.3, 129.9, 128.9,
128.7, 127.3, 127.1, 112.7, 109.5, 99.5, 70.3, 69.2, 65.3, 50.4, 49.8, 48.3, 46.2,
23.7, 11.9 ppm; MALDI-TOF MS: m/z: 1599 [MÀ2HPF6+Na]+, 3155
[2MÀ3HPF6ÀPF6À]+, 4879 [3MÀ4HPF6ÀPF6À]+; elemental analysis
calcd (%) for C92H98F12N4O20P2·H2O: C 58.54, H 5.34, N 2.97; found: C
58.51, H 5.40, N 3.09.
Crystal data for 2·42·2CH3CN: C108H116F12N6O20P2; Mr =2108.01; triclinic;
¯
P1; a=14.724(4), b=15.238(4), c=15.251(5) ꢁ; a=104.069(3), b=
106.313(3), g=104.044(3)8; V=3002.5(15) ꢁ3; Z=1; 1=1.166 gcmÀ3
;
T=173(2) K; R1 =0.1088, wR2 =0.2632 (all data), R1 =0.0881, wR2 =
0.2455 (I>2s(I)). CCDC-782052 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via www.ccdc.cam.
ac.uk/data_request/cif.
Compound 2: According to a similar procedure for the synthesis of 9,
compound 2 as a yellow solid was obtained in 95% yield by the reaction
of acid anhydride 7 and aniline. M.p. >3008C; 1H NMR (300 MHz,
CDCl3): d=7.35 (d, J=7.8 Hz, 4H), 7.28 (d, J=7.8 Hz, 2H), 7.18 (d, J=
7.5 Hz, 4H), 6.89 (s, 8H), 4.17–4.06 (m, 9H), 4.06–3.97 (m, 8H), 3.94–
3.77 (m, 24H), 3.77–3.67 (m, 8H), 2.29 ppm (s, 12H); 13C NMR
(75 MHz, CDCl3): d=165.3, 157.4, 145.8, 141.6, 131.7, 128.9, 127.4, 126.5,
109.6, 71.1, 70.0, 69.9, 48.6, 12.1 ppm; MALDI-TOF MS: m/z: 1361.6
[M+Na]+; elemental analysis calcd (%) for C76H78N2O20: C 68.15, H 5.87,
N 2.09; found: C 67.93, H 5.91, N 2.09.
Acknowledgements
We thank the National Natural Science Foundation of China (20625206,
20772126), the Chinese Academy of Sciences, and the National Basic Re-
search Program of China (2011CB932501) for financial support.
Compound 12: A mixture of 4-nitrobenzaldehyde (1.51 g, 10.0 mmol)
and benzylamine (1.07 g, 10.0 mmol) in toluene (65 mL) was heated at
reflux for 24 h, and then concentrated under reduced pressure. The resi-
due was dissolved in 1:1 (v/v) THF/CH3OH (40 mL), and NaBH4 (1.11 g,
30.0 mmol) was added in batches. After the mixture was stirred at room
temperature overnight, an excess amount of NaBH4 was decomposed by
adding water slowly, and the mixture was extracted three times by
CH2Cl2. The organic layer was dried over anhydrous Na2SO4, and then
concentrated to afford a residue, which was dissolved in CH2Cl2 (45 mL).
After adding di-tert-butyl dicarbonate (Boc2O) (4.36 g, 20.0 mmol) and
DMAP (122 mg, 1.00 mmol), the mixture was stirred at room tempera-
ture overnight. Removal of the solvent under reduced pressure gave a
crude product, which was purified by flash column chromatography with
petroleum and EtOAc (30:1 v/v) as eluent to afford 12 (2.12 g, 62%) as a
colorless oil. 1H NMR (300 MHz, CDCl3): d=8.17 (d, J=8.1 Hz, 2H),
7.65–6.88 (m, 7H), 4.68–4.25 (m, 4H), 1.50 ppm (s, 9H); 13C NMR
(75 MHz, CDCl3): d=155.8, 147.2, 145.8, 137.4, 128.7, 128.4, 128.1, 127.6,
123.8, 80.7, 50.2, 48.9, 28.4 ppm; ESI-MS: m/z: 365.2 [M+Na]+; elemen-
tal analysis calcd (%) for C19H22N2O4: C 66.65, H 6.48, N 8.18; found: C
66.48, H 6.48, N 8.02.
[1] a) J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995;
b) T. F. A. de Greef, E. W. Meijer, Nature 2008, 453, 171–173;
c) T. F. A. de Greef, M. M. J. Smulders, M. Wolffs, A. P. H. J. Schen-
ning, R. P. Sijbesma, E. W. Meijer, Chem. Rev. 2009, 109, 5687–
5754, and references therein.
[2] For examples of the formation of supramolecular polymers by hy-
drogen bonding, see: a) R. P. Sijbesma, F. H. Beijer, L. Brunsveld,
B. J. B. Folmer, J. H. K. K. Hirschberg, R. F. M. Lange, J. K. L.
Lowe, E. W. Meijer, Science 1997, 278, 1601–1604; b) T. F. A. de
Greef, G. Ercolani, G. B. W. L. Ligthart, E. W. Meijer, R. P. Sijbes-
ma, J. Am. Chem. Soc. 2008, 130, 13755–13764; c) T. Park, S. C.
Zimmerman, J. Am. Chem. Soc. 2006, 128, 11582–11590; d) T. Park,
S. C. Zimmerman, J. Am. Chem. Soc. 2006, 128, 13986–13987; e) S.
Yagai, T. Kinoshita, M. Higashi, K. Kishikawa, T. Nakanishi, T. Kar-
atsu, A. Kitamura, J. Am. Chem. Soc. 2007, 129, 13277–13287;
f) S. H. M. Sçntjens, R. P. Sijbesma, M. H. P. van Genderen, E. W.
Meijer, Macromolecules 2001, 34, 3815–3818; g) A. T. ten Cate, H.
Kooijman, A. L. Spek, R. P. Sijbesma, E. W. Meijer, J. Am. Chem.
Soc. 2004, 126, 3801–3808; h) M. F. Mayer, S. Nakashima, S. C. Zim-
merman, Org. Lett. 2005, 7, 3005–3008; i) T. Park, E. M. Todd, S.
Compound 13: According to a similar procedure for the synthesis of 12,
compound 13 as a colorless oil was obtained in 66% yield starting from
2440
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 2435 – 2441

Self-Complementary Monomer
FULL PAPER
Nakashima, S. C. Zimmerman, J. Am. Chem. Soc. 2005, 127, 18133–
18142; j) O. A. Scherman, G. B. W. L. Ligthart, R. P. Sijbesma, E. W.
Meijer, Angew. Chem. 2006, 118, 2126–2130; Angew. Chem. Int. Ed.
2006, 45, 2072–2076; k) O. A. Scherman, G. B. W. L. Ligthart, H.
Ohkawa, R. P. Sijbesma, E. W. Meijer, Proc. Natl. Acad. Sci. USA
2006, 103, 11850–11855; l) H. C. Ong, S. C. Zimmerman, Org. Lett.
2006, 8, 1589–1592; m) T. Park, S. C. Zimmerman, J. Am. Chem.
Soc. 2006, 128, 14236–14237; n) Y. Yang, H.-Y. Hu, C.-F. Chen, Tet-
rahedron Lett. 2007, 48, 3505–3509; o) Y. Yang, T. Chen, J.-F.
Xiang, H.-J. Yan, C.-F. Chen, L.-J. Wan, Chem. Eur. J. 2008, 14,
5742–5746.
1998, 37, 1294–1297; g) P. J. Ashton, I. W. Parsons, F. M. Raymo,
J. F. Stoddart, A. J. P. White, D. J. Williams, R. Wolf, Angew. Chem.
1998, 110, 2016–2019; Angew. Chem. Int. Ed. 1998, 37, 1913–1916;
h) S. J. Cantrill, G. J. Youn, J. F. Stoddart, D. J. Williams, J. Org.
Chem. 2001, 66, 6857–6872.
[6] F. H. Huang, D. S. Nagvekar, C. Slebodnick, H. W. Gibson, J. Am.
Chem. Soc. 2005, 127, 484–485.
[7] F. H. Huang, H. W. Gibson, J. Am. Chem. Soc. 2004, 126, 14738–
14739.
[8] a) K. C. F. Leung, P. M. Mendes, S. N. Magonov, B. H. Northrop, S.
Kim, K. Patel, A. H. Flood, H. R. Tseng, J. F. Stoddart, J. Am.
Chem. Soc. 2006, 128, 10707–10715; b) H. W. Gibson, N. Yamagu-
chi, L. M. Hamilton, J. W. Jones, J. Am. Chem. Soc. 2002, 124, 4653–
4665; c) K. C. F. Leung, F. Aric, S. J. Cantrill, J. F. Stoddart, Macro-
molecules 2007, 40, 3951–3959; d) N. Yamaguchi, L. M. Hamilton,
H. W. Gibson, Angew. Chem. 1998, 110, 3463–3466; Angew. Chem.
Int. Ed. 1998, 37, 3275–3279; e) K. C. F. Leung, F. Aric, S. J. Cantrill,
J. F. Stoddart, J. Am. Chem. Soc. 2005, 127, 5808–5810.
[3] For some examples of the formation of supramolecular polymers by
metal–ligand interactions, see: a) W. G. Weng, J. B. Beck, A. M. Ja-
mieson, S. J. Rowan, J. Am. Chem. Soc. 2006, 128, 11663–11672;
b) W. L. Leong, S. K. Batabyal, S. Kasapis, J. J. Vittal, Chem. Eur. J.
2008, 14, 8822–8829; c) J. M. J. Paulusse, D. J. M. van Beek, R. P. Sij-
besma, J. Am. Chem. Soc. 2007, 129, 2392–2397.
[4] a) A. Harada, Y. Takashima, H. Yamaguchi, Chem. Soc. Rev. 2009,
38, 875–882; b) D.-S. Guo, S. Chen, H. Qian, H.-Q. Zhang, Y. Liu,
Chem. Commun. 2010, 46, 2620–2622; c) R. Nally, L. Isaacs, Tetra-
hedron 2009, 65, 7249–7258; d) S. Pappalardo, V. Villari, S. Slovak,
Y. Cohen, G. Gattuso, A. Notti, A. Pappalardo, I. Pisagatti, M. F.
Parisi, Chem. Eur. J. 2007, 13, 8164–8173; e) H. Danjo, K. Hirata, S.
Yoshigai, I. Azumaya, K. Yamaguchi, J. Am. Chem. Soc. 2009, 131,
1638–1639; f) R. M. Yebeutchou, F. Tancini, N. Demitri, S. Geremia,
R. Mendichi, E. Dalcanale, Angew. Chem. 2008, 120, 4580–4584;
Angew. Chem. Int. Ed. 2008, 47, 4504–4508; g) G. Fernꢂndez, E. M.
Perez, L. Sanchez, N. Martin, Angew. Chem. 2008, 120, 1110–1113;
Angew. Chem. Int. Ed. 2008, 47, 1094–1097; h) G. Gattuso, A. Notti,
A. Pappalardo, M. F. Parisi, I. Pisagatti, S. Pappalardo, D. Garozzo,
A. Messina, Y. Cohen, S. Slovak, J. Org. Chem. 2008, 73, 7280–
7289; i) C. Leggio, M. Anselmi, A. Di Nola, L. Galantini, A. Jover,
F. Meijide, N. V. Pavel, V. H. S. Tellini, J. V. Tato, Macromolecules
2007, 40, 5899–5906; j) U. Rauwald, O. A. Scherman, Angew. Chem.
2008, 120, 4014–4017; Angew. Chem. Int. Ed. 2008, 47, 3950–3953;
k) L. Galantini, A. Jover, C. Leggio, F. Meijide, N. V. Pavel, V. H. S.
Tellini, J. V. Tato, C. Tortolini, J. Phys. Chem. B 2008, 112, 8536–
8541.
[5] a) F. H. Huang, D. S. Nagvekar, X. C. Zhou, H. W. Gibson, Macro-
molecules 2007, 40, 3561–3567; b) N. Yamaguchi, D. S. Nagvekar,
H. W. Gibson, Angew. Chem. 1998, 110, 2518–2520; Angew. Chem.
Int. Ed. 1998, 37, 2361–2364; c) H. W. Gibson, N. Yamaguchi, J. W.
Jones, J. Am. Chem. Soc. 2003, 125, 3522–3533; d) N. Yamaguchi,
H. W. Gibson, Angew. Chem. 1999, 111, 195–199; Angew. Chem.
Int. Ed. 1999, 38, 143–147; e) F. Wang, C. Y. Han, C. L. He, Q. Z.
Zhou, J. Q. Zhang, C. Wang, N. Li, F. H. Huang, J. Am. Chem. Soc.
2008, 130, 11254–11255; f) P. R. Ashton, I. Baxter, S. J. Cantrill,
M. C. T. Fyfe, P. T. Glink, J. F. Stoddart, A. J. P. White, D. J. Wil-
liams, Angew. Chem. 1998, 110, 1344–1347; Angew. Chem. Int. Ed.
[9] a) A. R. Hirst, B. Escuder, J. F. Miravet, D. K. Smith, Angew. Chem.
2008, 120, 8122–8139; Angew. Chem. Int. Ed. 2008, 47, 8002–8018;
b) W. Deng, H. Yamaguchi, Y. Takashima, A. Harada, Angew.
Chem. 2007, 119, 5236–5239; Angew. Chem. Int. Ed. 2007, 46, 5144–
5147; c) D. M. Loveless, S. L. Jeon, S. L. Craig, J. Mater. Chem. 2007,
17, 56–61; d) K. Morino, M. Oobo, E. Yashima, Macromolecules
2005, 38, 3461–3468.
[10] Z. S. Ge, J. M. Hu, F. H. Huang, S. Y. Liu, Angew. Chem. 2009, 121,
1830–1834; Angew. Chem. Int. Ed. 2009, 48, 1798–1802.
[11] a) Y. K. Joung, T. Ooya, M. Yamaguchi, N. Yui, Adv. Mater. 2007,
19, 396–400; b) L. Li, X. Guo, J. Wang, P. Liu, R. K. Prud’homme,
B. L. May, S. F. Lincoln, Macromolecules 2008, 41, 8677–8681;
c) C. G. Gong, H. W. Gibson, J. Am. Chem. Soc. 1997, 119, 5862–
5866; d) A. Charlot, R. Auzely-Velty, Macromolecules 2007, 40,
9555–9563; e) O. Kretschmann, S W. Choi, M. Miyauchi, I. Tomatsu,
A. Harada, H. Ritter, Angew. Chem. 2006, 118, 4468–4472; Angew.
Chem. Int. Ed. 2006, 45, 4361–4365.
[12] a) Q.-S. Zong, C.-F. Chen, Org. Lett. 2006, 8, 211–214; b) J.-M.
Zhao, Q.-S. Zong, T. Han, J.-F. Xiang, C.-F. Chen, J. Org. Chem.
2008, 73, 6800–6806; c) T. Han, C. F. Chen, Org. Lett. 2007, 9, 4207–
4210; d) T. Han, C.-F. Chen, J. Org. Chem. 2008, 73, 7735–7742;
e) Y. Jiang, J.-B. Guo, C.-F. Chen, Chem. Commun. 2010, 46, 5536–
5538.
[13] Q.-S. Zong, C. Zhang, C.-F. Chen, Org. Lett. 2006, 8, 1859–1862.
[14] Y.-S. Su, C.-F. Chen, Org. Lett. 2010, 12, 1888–1891.
[15] X.-Z. Zhu, C.-F. Chen, J. Am. Chem. Soc. 2005, 127, 13158–13159.
[16] P. W. Jeffs, J. F. Hansenza, G. A. Brinezb, J. Org. Chem. 1975, 40,
2883–2890.
Received: October 5, 2010
Published online: January 17, 2011
Chem. Eur. J. 2011, 17, 2435 – 2441
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2441