Counter cation dependent and stimuli responsive supramolecular polymers constructed by calix[4]pyrrole based host–guest interactions

Article abstract of DOI:10.1002/ejoc.201801663

Carboxylate tethered calix[4]pyrroles in the form of their tetrabutylammonium (TBA) and cetyltrimethylammonium (CTA) salts were synthesized via an acid base reaction between the corresponding carboxylic acid functionalized calix[4]pyrrole and tetrabutyl-or cetyltrimethylammonium hydroxide. The host–guest recognition motif based on these calix[4]pyrrole macrocycles and tethered carboxylate units was employed to construct novel A–B type supramolecular polymers from low molecular weight monomers in chloroform. These supramolecular polymers were found to be dependent on the counter cation in terms of the properties of supramolecular polymers.¹H-, DOSY-, NOESY-NMR spectroscopic analyses, viscosity measurements, and SEM results were used to characterize supramolecular polymers and revealed that the CTA cation becomes a direct part of supramolecular polymer via cation–π interactions between the ammonium part of CTA and carboxylate-bound calix[4]pyrrole, effecting the overall properties of supramolecular polymers such as viscosity, gel formation, and drawing fibers. Additionally, reversible pH-and thermo-responsiveness of the supramolecular polymers were demonstrated for the first time for an anion recognition induced calix[4]pyrrole based supramolecular polymer.

Full text of DOI:10.1002/ejoc.201801663

DOI: 10.1002/ejoc.201801663
Full Paper
Supramolecular Polymers
Counter Cation Dependent and Stimuli Responsive
Supramolecular Polymers Constructed by Calix[4]pyrrole Based
Host–Guest Interactions
[a]
[a]
Samet Yuvayapan and Abdullah Aydogan*
Abstract: Carboxylate tethered calix[4]pyrroles in the form of DOSY-, NOESY-NMR spectroscopic analyses, viscosity measure-
their tetrabutylammonium (TBA) and cetyltrimethylammonium ments, and SEM results were used to characterize supramolec-
(CTA) salts were synthesized via an acid base reaction between ular polymers and revealed that the CTA cation becomes a di-
the corresponding carboxylic acid functionalized calix[4]pyrrole rect part of supramolecular polymer via cation–π interactions
and tetrabutyl- or cetyltrimethylammonium hydroxide. The between the ammonium part of CTA and carboxylate-bound
host–guest recognition motif based on these calix[4]pyrrole calix[4]pyrrole, effecting the overall properties of supramolec-
macrocycles and tethered carboxylate units was employed to ular polymers such as viscosity, gel formation, and drawing fi-
construct novel A–B type supramolecular polymers from low bers. Additionally, reversible pH- and thermo-responsiveness of
molecular weight monomers in chloroform. These supramolec- the supramolecular polymers were demonstrated for the first
ular polymers were found to be dependent on the counter cat- time for an anion recognition induced calix[4]pyrrole based
1
ion in terms of the properties of supramolecular polymers. H-, supramolecular polymer.
Introduction
tetramers are widely investigated.[8] However, pH- and thermo-
responsive high performance supramolecular polymers based
on the recognition of anionic guest species have not been fully
exploited yet.
Highly complicated and ordered materials having stimuli-re-
sponsiveness are ubiquitous in biological systems, in which the
reversible interactions play a critical role. Development of new
materials with unique properties requires the understanding of
reversibility and responsiveness. At this junction, supramolec-
ular chemistry provides a platform to develop advanced and
sophisticated materials with unconventional properties. Supra-
molecular polymers, constructed from low molecular weight
monomers with the aid of reversible noncovalent interactions,
are kind of responsive polymers that can be sensitive to solvent,
concentration, pH, temperature and chemical stimuli. Numer-
ous types of forces, such as hydrogen bonding, metal-ligand
coordination, and hydrophobic and donor–acceptor interac-
tions are employed to engineer supramolecular polymers.
Among these, host–guest interactions have been widely utilized
to construct supramolecular polymers by using various macro-
Calix[4]pyrroles, known as selective anion receptors that
recognize anions (e.g., fluoride, chloride, and acetate) well in
organic media, have been widely employed as anion extraction
[9]
[10]
agents, anion separating solid supports,
ion transport-
and ion-pair re-
Calix[4]pyrroles have also been used as building
[11]
[12]
ers,
ceptors.
electroactive, optical anion sensors
[13]
blocks to construct functional assemblies with complementary
guest species. For instance, Sessler and co-workers reported
heterocomplementary subunits consisting of a tetrathiafulval-
ene-functionalized calix[4]pyrrole and glycol diester-linked bis-
[
1]
2
,5,7-trinitrodicyanomethylenefluorene-4-carboxylate or bis(di-
[
2]
[14]
nitrophenyl)-meso-substituted calix[4]pyrrole.
These mono-
mers were found to produce short oligomers stabilized by
hydrogen bonding and donor–acceptor charge transfer interac-
tions. An imidazolium-functionalized calix[4]pyrrole in the form
of its bromide salt was also used to produce a supramolecular
polymer via recognition of both the anion and imidazolium cat-
[
3]
[4]
cyclic hosts such as crown ethers, calixarenes, cyclodex-
[
5]
[6]
[7]
trins, cryptands and pillar[5]arenes. In this context, a num-
ber of guest molecules (e.g., adamantane, anthracene, charged-
naphthalenes, -amines, -imidazoles, and viologens) have been
used as neutral or positively charged guest species when they
incorporated into the structures of above mentioned host mol-
ecules. Supramolecular chemistry of anionic dimers, trimers and
ion. Unfortunately, this system was suffered from low solubility
[15]
in organic solvents such as CHCl and CH Cl .
Although the
3
2
2
above resulting supramolecular assemblies were found to show
dynamic guest dependent structural transformations and good
fidelities, these systems suffered from either complicated syn-
[
a] Department of Chemistry, Istanbul Technical University,
Maslak, Istanbul, 34469 Turkey
thetic steps, low degrees of supramolecular polymeriza-
[14a,15]
tion
or higher critical supramolecular polymerization con-
E-mail: aydoganab@itu.edu.tr
http://akademi.itu.edu.tr/en/aydoganab
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejoc.201801663.
[
16]
centrations (CPC).
Calix[4]pyrrole based, counter cation de-
pendent, dual responsive, and high performance supramolec-
ular polymers with low CPC have not been reported yet.
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Structural analyses of supramolecular monomers reported conditions.[18] Therefore we followed the click reaction strategy
earlier reveals that, for an A–B type monomer, favoring the for- to obtain calix[4]pyrrole 1 starting from an alkyne-functional-
mation of linear supramolecular polymers with low CPC can be ized calix[4]pyrrole and an azido compound having a carboxylic
achieved by using long and flexible alkyl chain linkers between acid functionality. To do so, alkyne-functionalized calix[4]pyrrole
[
17]
[9d]
[19]
host and guest moieties.
On the basis of these findings, we
3
was dissolved in THF and reacted with 4 in the presence
report here the design and synthesis of a novel, dual responsive of an aqueous solution of CuSO ·5(H O) and sodium ascorbate
4
2
and counter cation dependent supramolecular polymer, which at room temperature. After completion of the reaction, crude
was constructed from a heteroditopic A–B type calix[4]pyrrole products were extracted with methylene chloride and precipi-
monomer (2) by utilizing the reversible host–guest interactions tated from hexane after workup. This was yielded 1 in 96 % as
between the calix[4]pyrrole core and its tethered carboxylate a pale yellow solid. Once we have the carboxylic acid-function-
unit (Figure 1). The effect of counter cation on the properties alized calix[4]pyrrole 1 in hand, it was treated with TBAOH or
of supramolecular polymers was also investigated by using two cetyltrimethylammonium hydroxide (CTAOH)[20] to obtain 2a
different ammonium cations, namely tetrabutylammonium and 2b, respectively. For instance, a methanol solution of 1
(
TBA) and cetyltrimethylammonium (CTA). When CTA was used treated with equimolar TBAOH to give essentially pure 2a quan-
as counter cation, the long alkyl chain was envisioned as the titatively in 1 h after removal of the solvent. 2b was also ob-
basis of high solubility and enhancements in the properties of tained in the same manner when 1 reacted with CTAOH.
supramolecular polymers (e.g., viscosity, drawing fibers and gel
formation) via additional hydrophobic interactions between
long alkyl chains of CTA which was a direct part of supramolec-
ular polymer through cation–π interactions.
Figure 1. Structures of carboxylic acid (1), carboxylate-functionalized calix[4]-
pyrroles (2), and the counter cation dependent supramolecular polymeriza-
tion of 2a and 2b.
4 2
Scheme 1. Synthesis of 1 and 2. i) CuSO ·5(H O), sodium ascorbate/THF, r.t.,
4
8 h. ii) In MeOH, r.t., 1 h.
Characterizations of the precursor 1 and carboxylate-func-
tionalized target compounds (2a and 2b) were carried out us-
Results and Discussion
1
13
Preparation of carboxylate-functionalized calix[4]pyrroles 2a ing H and C NMR spectroscopy, as well as low- and high-
1
and 2b starts with the synthesis of corresponding carboxylic resolution mass spectroscopy. For example, H NMR analysis of
acid functionalized calix[4]pyrrole 1 as illustrated in Scheme 1. compound 1 revealed the CH protons of triazole ring at
Sharpless and co-workers introduced the “Click Chemistry” as a 7.59 ppm as a singlet peak. Pyrrole NH proton signals were
term describing the reactions displaying high yields with toler- observed at 7.23 and 7.12 ppm as two distinctive resonance
ance to a wide range of substrates and solvents under mild signals, reflecting the asymmetric nature of the compound 1.
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Similarly, the presence of multiplet and triplet peaks at 5.92 the tethered carboxylate via hydrogen bonding.[15,23] This was
and 5.67 ppm was attributed to the CH protons of pyrrole ring also supported by the existence of correlated 2D-NOESY signals
(
Figure 2a and S2).
between the methyl protons of CTA and pyrrole CH protons of
calix[4]pyrrole core (Figure S22).
1
Variable concentration H NMR analyses provide important
insights into the self-assembly behavior of supramolecular ag-
[
24]
gregates in solution. Although the calix[4]pyrroles 2a and 2b
were expected to form monomers and short oligomers at low
concentrations, they were anticipated to self-assemble into
higher order aggregates at elevated concentrations to give
supramolecular polymers. This is because of an association con-
3
–1
stant (K = 1.77 × 10 ± 24.6
M
in CDCl , Fig. S15) between
a
3
calix[4]pyrrole and tethered carboxylate unit and the existence
of a long flexible alkyl chain linker. In accordance, concentra-
1
tion-dependent H NMR analyses of 2a and 2b were carried out
in CDCl . As shown in Figure 3 and Figure 4, calix[4]pyrroles
3
2a and 2b behave differently when their NMR spectra were
compared under the same concentrations. For instance, while
pyrrole NH proton resonance signals of 2a were observed at
9.55 ppm, in the case of 2b these signals were found to reso-
Figure 2. Partial 1H NMR spectra (500 MHz) of (a) 1, (b) 2a, (c) 2b, and (d)
CTAOH recorded in CDCl at 25 °C. * denotes residual solvent peaks.
3
nate at 11.09 and 11.27 ppm at 12 mM concentrations (cf. Fig-
ure 3a and Figure 4a). The corresponding signals undergo a
downfield shift (10.70 ppm) as the concentration of 2a was in-
1H NMR measurements can also be used to obtain important
information regarding the complexation behavior of supra-
creased to 191 mM. These peaks were found to resonate at
[
21]
1
molecular monomers.
Therefore, H NMR spectra of 2a and
1
1.09 and 11.27 ppm and not to be affected over the course of
2
b in CDCl3 (12 m ) were compared with the ones that of
M
the above concentration increment in the case of 2b (cf. Fig-
precursor 1 and CTAOH. As shown in Figure 2, while pyrrole NH
resonance signals of 1 were observed as two distinct peaks at
ure 3d and Figure 4d). Another result that can be inferred from
1
the concentration-dependent H NMR spectra is that as the
7.12 and 7.23 ppm, in the case of 2a they were found to be
concentrations of 2a and 2b were increased gradually, all pro-
ton signals become broader, indicating the formation of higher
order supramolecular aggregates in solution. In the case of 2b
these peak broadenings were significantly enhanced when
compared to 2a.
shifted downfield to 9.55 ppm as a single broad peak. In con-
trast, pyrrole CH proton signals of 2a appeared to be shifted
upfield from 5.91 ppm to 5.78 ppm (cf. Figure 2a and 2b). When
a calix[4]pyrrole was bound to an anion these lower and upper
[
22]
field peak shifts are known as typical.
Parallel to the above
results, similar peak shifts were observed in the case of 2b. For
instance, pyrrole NH peaks of 2b were observed at 11.09 and
11.27 ppm, pyrrole CH proton resonances gave rise around
5.66 ppm (cf. Figure 2a and 2 d). These results clearly indicate
that 2a and 2b exhibit intermolecular interactions via complex-
ation of pyrrole NHs and tethered carboxylate units.
Since the counter cations of 2a and 2b are different, their
effect on the self-assembly process was investigated by using
1
H NMR spectroscopy. An inspection of Figure 2b reveals that
while the methylene protons connected to the nitrogen atom
of TBA resonate at 3.06 ppm, in the case of CTA resonance
signals of the same protons appear as a broad peak at
2.23 ppm. Similar to this observation, resonance signals belong-
ing to the methyl protons of CTA gave rise as a very broad
peak at 1.90 ppm (Figure 2c). On the other hand, methyl and
methylene protons connected to the nitrogen atom of CTAOH
gave resonance signals originally at 3.38 and 3.26 ppm, respec-
tively (Figure 2d). When a calix[4]pyrrole is bound to an anion
it adopts a cone conformation while forming a “cup-like” π elec-
[
16]
tron cloud by means of oriented pyrrole rings. Upfield chemi-
cal shifts belonging to methyl and methylene protons of CTA
clearly indicate that calix[4]pyrrole core of 2b acts as an ion
pair receptor for both tethered carboxylate unit and CTA, bind-
ing the ammonium cation of CTA via cation–π interactions and
1
Figure 3. H NMR spectra (CDCl
3
, 500 MHz, 25 °C) of 2a at different concentra-
. * denotes residual solvent peaks.
tions: (a) 12, (b) 35, (c) 125, (d) 191 m
M
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Figure 4. Partial 1H NMR spectra (CDCl
, 500 MHz, 25 °C) of 2b at different
3
concentrations: (a) 12, (b) 35, (c) 125, (d) 190 m
peaks.
M. * denotes residual solvent
Figure 5. Specific viscosity (Vs) changes of 2a and 2b plotted against mono-
3
mer concentration in CHCl at 25 °C.
Two-dimensional diffusion ordered NMR (DOSY) can be util-
ized to investigate the self-assembly process of monomers and broader peaks than 2a even at low concentrations that can
to compare the sizes of supramolecular aggregates quantitatively be judged from Figure 3a and Figure 4a and lower diffusion
[
25]
by using diffusion coefficients.
dependent DOSY experiments of 2a and 2b were performed curve slope (m=3.09 and 2.72 for 2b and 2a, respectively) was
Figures S23–26). Specifically, weighted average diffusion coeffi- obtained in the case of viscosity measurements. Furthermore, a
Therefore, concentration- coefficient during DOSY NMR analyses. Additionally, a higher
(
–10
–10
2 –1
cients were measured as 6.81 × 10 and 4.79 × 10 m s for binding constant because of the interaction between the π-
2 m 2a and 2b solutions, respectively. When the concentration electron cloud of cone-shaped carboxylate-bound calix[4]pyrr-
was increased, diffusion coefficients of the 2a (300 m ) and 2b ole 3 and the ammonium cation of cetyltrimethylammonium
191 m ) were found to be decreased to 1.20 × 10 and acetate (CTAOAc) (cf. Figure 2c and Figure 2d) was calculated
1
M
M
–10
(
1
M
–
10
2
–1
2
–1
.04 × 10
m s , respectively. These sharp decreases in the to be K = 1.13 × 10 ± 0.87
M
in CDCl (Figure S18), indicating
a
3
diffusion coefficients indicate the existence of higher order that CTA becomes a direct part of supramolecular polymer. This
supramolecular polymers at elevated concentrations of 2a and was also supported by NOESY NMR analyses of 10.2 and
2b.
191 mM CDCl solutions of 2b. The correlated 2D-NOESY signals
3
Viscosity is a direct index for the formation of polymers. between methylene units of CTA were found to be enhanced
Therefore, viscosity measurements were also carried out by us- at high concentration (cf. Figures S21 and S22). All of these
ing an Ubbelohde semi-micro dilution viscometer to analyze results let us to conclude that the presence of long alkyl chains
further the supramolecular polymers obtained from 2a and 2b. of CTA provides additional hydrophobic interactions, as the
As shown in Figure 5, a double-logarithmic plot of specific vis- supramolecular polymer of 2b grows. These enhanced proper-
cosity (Vs) vs. concentration changes of monomers exhibited ties were also found to be reflected in the degree of polymeri-
viscosity transitions. At low concentration ranges, the curve has zation (DP). DP values of 2b were estimated to be at least 40 %
a slop of 1.05. As the concentrations increased gradually, the higher than those of 2a (Table S1).
slopes of curves approach 2.72 and 3.09 for 2a and 2b, respec-
Since 2b exhibits better supramolecular polymerization per-
tively. The linear relationship (slope of 1.05) between concentra- formance, a high concentration solution of 2b was used to draw
tion and viscosity indicates the presence of monomers and oli- rod-like fibers. Scanning electron microscopy (SEM) images of
gomers with constant sizes for both 2a and 2b. Whereas, expo- fibers are shown in Figure 6a and revealed fibers with diameters
nential relationships (slopes of 2.72 and 3.09) are indicative for of 9.03 and 4.06 μm, providing direct evidence for the forma-
the formation of supramolecular polymers in which the size of tion of supramolecular polymers with high degree of molecular
[
26]
supramolecular aggregates exhibited a nonlinear change with weights.
concentration increments. The CPCs for the monomers 2a and 230 m
b in CHCl were found to be about 43 and 32 m , respectively, ing the solution to 25 °C afforded the reformation of supra-
After heating to 50 °C, the gel obtained from a
CHCl solution of 2b dissociated into a solution. Cool-
M
3
2
M
3
as evidenced from clear changes of slopes occurring at these molecular gel (cf. Figure 6c and Figure 6d). The SEM image of
concentrations, indicating transition from oligomeric and cyclic a freeze-dried gel sample exhibited a paraffin like network
species to highly ordered supramolecular polymers.
structure (Figure 6b). Thermo-responsive behaviour of the
NMR analyses and viscosity measurements reveal that 2b ex- supramolecular polymer formed by 2b was also supported by
hibits a better performance in the properties of supramolecular variable temperature viscosity measurements. As illustrated in
polymer when it was compared with 2a. This is because 2b Figure 6e, Vs. of a 158 m
M
CHCl solution of 2b was found to
3
1
exhibits notable enhanced peak broadenings when the H NMR be 4.04 at 25 °C. When the temperature of the solution was
spectra of equimolar high concentration solutions of 2a and 2b increased to 50 °C, it was measured as 1.1. 2a also showed a
were compared (cf. Figure 3d and Figure 4d). 2b also shows similar result when it was exposed to variable temperature vis-
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cosity measurements (Figure 8b). These sharp viscosity de- 10.56 to 7.35 and 7.25 ppm, indicating the disruption of host–
creases reflects the dynamic nature of noncovalent interactions guest interaction between calix[4]pyrrole and carboxylate units.
between calix[4]pyrrole and carboxylate units, and the presence However, the chemical shift reversed back to 10.33 ppm after
of high molecular weight supramolecular polymers at low tem- addition of equimolar TBAOH, which is an indication of the re-
peratures.
establishment of complexation between the same host–guest
units. When the resulting solution was treated with CH SO H
3
3
again, the corresponding NH proton signals were observed at
.19 ppm as a broad singlet, showing that this process can be
7
repeated over the course of consecutive acid base treatments.
The pH responsiveness of 2a was also confirmed by viscosity
measurements which were carried out with a 100 m
M CHCl3
solution of 2a while increasing the concentration of CH SO H
3
3
gradually (Figure 8a). As the concentration of acid was in-
creased, Vs. of the solution decreased gradually, since the
H-bonding interactions between calix[4]pyrrole core and the
carboxylate unit were broken step by step. These studies clearly
indicate that the supramolecular polymerization of 2 can be
controlled by changing the pH of solution. DOSY NMR analyses
also support these findings. While the diffusion coefficient
of a 100 m
2
M
2
CDCl3 solution of 2a was determined as
.62 × 10– m s , after treatment with equimolar CH SO H it
10
–1
3
3
–10
2 –1
was found to be 4.04 × 10 m s (Figures S27 and 28).
Figure 6. SEM images of gold-coated (a) fiber drawn from a 251 m
M CHCl
3
solution of 2b, and (b) supramolecular polymer gel obtained via freeze-dry-
ing of the same solution. Reversible sol-gel transition of supramolecular gel
obtained from a 251 m
Temperature dependent viscosity change of a 158 m
M
CHCl
3
solution of 2b at (c) 25 °C, (d) 50 °C. (e)
CHCl solution of 2b.
M
3
Calix[4]pyrroles 2a and 2b contains tethered carboxylate
units. Carboxylate salts can be protonated by adding an acid,
thus destroying the host–guest interaction between calix[4]-
pyrrole core and the carboxylate unit and making the supra-
molecular aggregates disassemble. Hence, the reversible supra-
molecular polymer–monomer transition could be achieved by
changing pH. Evidence for this was provided by chemical shift
Figure 8. Specific viscosity changes of CHCl
3
solutions 2a (a) (100 m
M
) upon
1
incremental addition of CH SO H, (b) (257 mM) upon incremental change in
changes in H NMR spectra (Figure 7). When equimolar
3
3
the temperature.
CH SO H was added to a CDCl solution of monomer 2a
3
3
3
(
100 m
M
), pyrrole NH resonances were found to be shifted from
Conclusions
We present the synthesis and characterization of a carboxylic
acid-functionalized calix[4]pyrrole with a long alkyl chain linker
between the calix[4]pyrrole core and carboxylic acid unit. This
calix[4]pyrrole is then converted to its corresponding carboxyl-
ate derivatives (as TBA and CTA slats) by treatment with either
TBAOH or CTAOH. The resulting heteroditopic A–B type supra-
molecular monomers consisting of a calix[4]pyrrole core and a
tethered carboxylate unit with two different counter cations
were found to self-assemble into the higher order aggregates
at elevated concentrations to give pH- and thermo-responsive
supramolecular polymers, which was evidenced by various
techniques such as NMR spectroscopy, viscosity measurements,
and SEM analyses. When CTA was used as the counter cation,
it was shown to be a direct part of the supramolecular polymer
via cation–π interactions, providing enhanced properties to the
supramolecular polymers formed. The present work demon-
strates the first example of stimuli responsive and counter cat-
1
Figure 7. Partial H NMR spectra (500 MHz) of (a) 2a (100 m
M
, 0.5 mL), after
addition of equimolar (b) CH
CDCl at 25 °C.
3
SO
3
H, (c) TBAOH, and (d) CH SO H recorded in
3 3
3
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ion dependent supramolecular polymers based on calix[4]- and the resulting solid washed with diethyl ether followed by dry-
ing under vacuum afforded 2a as a white solid (632 mg, 95 %).
pyrroles and their anion recognition ability.
1
Melting point: > 213 °C (decomposes). H NMR (500 MHz, CDCl ,
3
2
6
5 °C): δ = 10.42 (br s, 4H, NH), 7.72 (s, 1H, triazole –CH), 6.86 and
.81 (d, 4H, benzene–CH), 5.88–5.65 (m, 8H, pyrrole–CH), 5.19 (s, 2H,
Experimental Section
-
OCH -), 4.40 (t, J=7.2 Hz, 2H, -CH -), 2.92 (m, 8H, -CH -), 1.91 (t, J=
2 2 2
1
. General Information: All solvents were dried before use accord-
7.5 Hz, 2H, -CH -), 1.27–1.83 (m, 51H, meso-CH and -CH -), 0.97
2
3
2
13
ing to standard literature procedures. Unless specifically indicated, ppm (t, J=7.3 Hz, 12H, -CH3). C NMR (126 MHz, CDCl ): δ = 186.6,
3
all other chemicals and reagents used in this study were purchased
from commercial sources and used as received. H, C, DOSY and
NOESY NMR spectra were recorded on Agilent VNMRS 500 spec- m/z 756.403 [M] . HRMS: m/z calcd for C H N O , 756.46013,
144.3, 140.5, 138.7, 136.8, 128.5, 122.4, 113.9, 105.7, 102.8, 53.4, 50.4,
44.0, 35.2, 33.3, 31.6, 29.7, 28.6, 26.3, 24.6, 22.7, 14.1. ppm. LRMS:
1
13
–
–
46 58 7 3
trometers using TMS as an internal reference. Mass spectra were
measured on a Thermo Scientific TSQ Quantum GC and Micromass
Autospec Ultima. Viscosity measurements were carried out with an
Ubbelohde micro dilution viscometer (Shanghai Liangjing Glass In-
strument Factory, 0.40 mm inner diameter) at 293 K in chloroform.
Melting points were determined using a Gallenkamp instrument
with 1 °C/min. temperature increment under ambient conditions.
found 758.46125. Elemental analysis: calculated for C H N O :
62 94 8 3
C 74.51, H 9.48, N 11.21; found C 74.93, H 9.79, N 11.14.
Compound 2b: This compound was prepared from 1 (126.5 mg,
.42 mmol) and CTOH (318 mg, 0.42 mmol) using the same proce-
dure that was used to produce 2a. The product was a white solid
0
(
(
(
431 mg, 98 %). M.p. > 213 °C (decomp). Melting point: > 198 °C
1
decomposes). H NMR (500 MHz, CDCl , 25 °C): δ = 11.45 and 11.27
The Compounds 3,[
9d] [19]
[27]
3
4
and CTAOAc
were synthesized ac-
br s, 4H, NH), 7.86 (br s, 1H, triazole–CH), 6.88 (m, 4H, benzene–
cording to previously reported literature procedures.
. Synthesis
Compound 1: 3 (830 mg, 1.52 mmol) and 10-azidodecanoic acid
4) (328 mg, 1.54 mmol) were dissolved in THF (20 mL). Then, the
CH), 5.60–5.83 (br m, 8H, pyrrole–CH), 5.31 (s, 2H, -OCH -), 4.40 (t,
2
2
J= 7.3 Hz, 2H, -CH -), 2.33 (t, J= 7 Hz, 2H, -CH -), 2.23 (br s, 2H,
2
2
-
NCH -), 1.90 (br m, 9H, -NCH ), 1.84 (s, 3H, -CH ), 1.69–121 (m, 60H,
2 3 3
1
3
meso-CH3 and -CH -), 0.89 ppm (t, J= 7 Hz, 3H, -CH ). C NMR
2
3
(
(
126 MHz, CDCl ): δ = 178.0, 156.2, 143.5, 141.3, 140.0, 138.2, 128.8,
3
solution of Na-ascorbate (664 mg, 3.35 mmol) in 1 mL of water was
added to reaction mixture dropwise followed by addition of solu-
tion of CuSO ·5H O (418 mg, 1.68 mmol) in 1 mL of water. The
1
2
23.9, 114.2, 103.5, 100.8, 66.1, 62.4, 51.0, 44.2, 34.8, 32.0, 29.7, 26.1,
–
4.9, 22.7 ppm. LRMS: m/z 756.412 [M] . HRMS: m/z calcd for
4
2
–
C H N O , 756.46013, found 758.46084. Elemental analysis: cal-
46 58 7 3
reaction mixture was stirred at room temperature for 24 h. After
the completion of the reaction solvent was removed under reduced
pressure. Then the crude mixture was dissolved in DCM (30 mL)
and washed with water three times. This was followed by washing
the organic phase with 0.1N HCl (30 mL) and brine (30 mL). Excess
solvent was removed under vacuum after drying the organic phase
culated for C H N O : C 74.96, H 9.68, N 10.76; found C 75.16, H
65 100 8 3
9.87, N 10.28.
Acknowledgments
with anhydrous Na SO . Resulting viscous solution was added drop- This work was supported by Istanbul Technical University (Grant
2
4
wise into excess hexane, causing the precipitation of 1 as a pale Number: TDK-2017-40643).
yellow solid (1.11 g, 96 %). Melting point: > 224 °C (decomposes).
1
H NMR (500 MHz, CDCl , 25 °C): δ =7.59 (s, 1H, triazole-CH), 7.23
3
Keywords: Supramolecular polymers · Self-assembly · Host-
guest systems · Macrocycles
and 7.12 (br s, 4H, NH), 6.94 and 6.86 (d, 4H, benzene-CH), 5.92 (m,
6
4
2
H, pyrrole CH), 5.67 (t, J=3 Hz, 2H, pyrrole CH), 5.19 (s, 2H, -OCH -),
2
.36 (t, J=7.2 Hz, 2H, -CH -), 2.35 (t, J=7.5 Hz, 2H, -CH -), 1.92 (br m,
2
2
H, -CH -), 1.86 (s, 3H, -CH ), 1.64 (br m, 2H, -CH -), 1.52 (br s, 18H,
2
3
2
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1
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86.56, 144.30, 140.50, 138.50, 136.77, 128.46, 122.37, 113.85,
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46 60 7 3
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OH ) form was washed with MeOH (100 mL). Methanol solution of
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Eur. J. Org. Chem. 0000, 0–0
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© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Supramolecular Polymers
A host–guest recognition motif based
on a calix[4]pyrrole macrocycle and
tethered carboxylate unit was em-
ployed to construct counter cation de-
pendent supramolecular polymers
from low molecular weight A–B type
monomers. Reversible pH- and
thermo-responsiveness of the supra-
molecular polymers were demon-
strated for the first time for a calix-
S. Yuvayapan, A. Aydogan* ............ 1–8
Counter Cation Dependent and
Stimuli Responsive Supramolecular
Polymers Constructed by Calix[4]-
pyrrole Based Host–Guest Interac-
tions
[
4]pyrrole based and anion recognition
induced supramolecular polymer.
DOI: 10.1002/ejoc.201801663
Eur. J. Org. Chem. 0000, 0–0
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8
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim