Supramolecular polymeric complexes of calix[8]arenes

Article abstract of DOI:10.1134/S1070427206090199

Formation of ionic complexes of calix[8]arenes with polymers of various basicities was studied, and previously unknown ternary polymeric complexes of calix[8]arenes of the ion-ion (polymer-calixarene-uranyl ion) and ion-hydrophilic molecule-hydrophobic molecule (polymer-calixarene-fullerene) types were prepared.

Full text of DOI:10.1134/S1070427206090199

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 9, pp. 1494 1499. Pleiades Publishing, Inc., 2006.
Original Russian Text
pp. 1510 1515.
A.V. Ten’kovtsev, L.V. Abramova, M.M. Dudkina, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 9,
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Supramolecular Polymeric Complexes of Calix[8]arenes
A. V. Ten’kovtsev, L. V. Abramova, and M. M. Dudkina
Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
Received March 17, 2006
Abstract Formation of ionic complexes of calix[8]arenes with polymers of various basicities was studied,
and previously unknown ternary polymeric complexes of calix[8]arenes of the ion ion (polymer calixarene
uranyl ion) and ion hydrophilic molecule hydrophobic molecule (polymer calixarene fullerene) types were
prepared.
DOI: 10.1134/S1070427206090199
Calixarenes exhibit unique properties from the
viewpoint of the host guest complex chemistry [1, 2].
Firstly, methods have been developed for facile syn-
thesis of calixarenes of the required size under proper-
ly chosen condensation conditions. Secondly, calix-
arenes have internal cavities of different size formed
by a belt of phenyl rings; these cavities are capable
to accommodate a guest molecule of a definite size,
which allows their use in molecular recognition. It
should be noted that calixarenes form complexes both
with neutral organic molecules and with ions. Further-
more, calixarenes can be readily functionalized, which
allows variation of their affinity for a guest molecule.
Finally, expenses for the preparation of calixarenes
from p-substituted phenols and formaldehyde are rela-
tively low, which is an important factor for practical
applications. For example, calixarenes can be used as
specific ligands in analytical chemistry, sensor tech-
niques, medical diagnostics, and synthesis of new
materials in supramolecular chemistry.
with ionic monomers of various basicities. As investi-
gation objects we chose octa-p-tert-butylcalix[8]arene
and octa-p-nitrocalix[8]arene, polymers of various
basicities (polyalkyleneacetamidines and poly-4-vinyl-
2+
pyridine), and fullerene C and uranyl ions UO as
60
2
guest species. The choice of the guest species was
governed by the complementarity of their size and the
size of the calix[8]arene cavity, and also by the pro-
nounced tendency of many calixarene derivatives to
form complexes with uranyl cation. Owing to the lat-
ter property, sulfo derivatives of calixarenes were
suggested as a sensor element [3] in determination of
the uranium content in radiochemical production
wastes.
EXPERIMENTAL
p-tert-Butylphenol, paraform, and solvents were
used without additional purification. To prepare the
3
complexes, we used polyamidines (M = 2 10 ,
w
For many technical applications, it is desirable to
combine in one sample the useful properties of both
calixarenes and polymers. Synthesis of polymers
based on calixarenes is a challenging problem, be-
cause these are polyhomofunctional compounds and
preparation of di- and monofunctionalized derivatives
suitable as monomers for polymerization or polycon-
densation is difficult. However, the presence in calix-
arenes of functional groups capable of deprotonation
(e.g., hydroxy groups) suggests the possibility of for-
mation of ionic complexes of calixarenes with basic
polymeric carriers.
M /M = 2.2) and poly-4-vinylpyridine (Acros, M =
w
n
w
4
1.6 10 ).
The NMR spectra were recorded on Bruker AC200
(200 MHz) and Bruker AC300 (300 MHz) spectrom-
eters from solutions in DMSO and chloroform. The
UV spectra were taken with Varian Cary 100 and
SF-26 spectrophotometers. The luminescence spectra
were excited with the nitrogen laser radiation (
=
337 nm, pulse length 6 8 ns) and were recorded
during the persistence time of 1 s after the excitation
pulse at T = 300 K. To measure the linear-optical
properties of the samples, we used a Nd garnet pulse
laser with the emission wavelength of 1.06 m. The
laser operated in the modulated Q-factor mode; the
In this study we examined the possibility of prep-
aration of binary and ternary complexes of calixarenes
1494

SUPRAMOLECULAR POLYMERIC COMPLEXES OF CALIX[8]ARENES
3
1495
pulse length was 15 ns. The dynamic light scattering
was measured with a Brookhaven BI-200SM goniom-
eter and a Brookhaven BI-9000AT correlator. As a
light source we used a He Ne laser ( = 632.8 nm).
a 1.5 10 M solution. The solution is filtered while
hot and allowed to slowly cool over a period of 24 h.
The black precipitate is separated by centrifugation
and dissolved in 5 ml of toluene. A polymer film is
prepared by casting a solution of 0.2068 g (1.2
p-Nitrocalix[8]arene. To 10 ml of a 1 : 1 mixture
3
10 mol) of poly-1,8-octamethyleneacetamidine in
of 65% HNO and 98% H SO , cooled to +3 C, 1 g
3
2
4
1.2 ml of alcohol onto a rotating support; the film is
dried over concentrated H SO , placed in the hot solu-
tion of the calixarene fullerene complex (see above),
and allowed to stand for 4 6 h in a closed weighing
bottle. The ternary complex is formed as a gray-brown
film. The product is extracted with two 2-ml portions
of boiling toluene and vacuum-dried.
4
(7.7 10 mol) of p-tert-butylcalix[8]arene [4] is
gradually added with stirring, keeping the temperature
of the reaction mixture in the interval 3 5 C. The
product is precipitated by adding 40 ml of water. The
yellow precipitate is treated with 20 ml of boiling
methanol; the solution is cooled and filtered. This
treatment is repeated two times. By so doing, two
fractions (soluble and insoluble in methanol) are ob-
2
4
Octa-p-tert-butylcalix[8]arene was prepared as de-
scribed in [4] by the condensation of p-tert-butylphen-
ol with paraform in the presence of sodium oxide.
According to published data, the simplest route to
octa-p-nitrocalix[8]arene is ipso nitration of octa-p-
tert-butylcalix[8]arene with acetyl nitrate [5] or with
a mixture of anhydrous HNO and H SO [6]. How-
ever, we failed to reproduce these procedures. In the
case of nitration with acetyl nitrate, it appeared im-
possible to add the reagent to a solution of octa-p-tert-
butylcalix[8]arene in methylene chloride because of
extremely low solubility of the macrocycle in this
solvent (in agreement with data of [4]). Nitration of
octa-p-tert-butylcalix[8]arene under the conditions
described in [6] yields octa-p-nitrocalix[8]arene heavi-
ly contaminated with decomposition products; the
suggested purification procedure, reprecipitation from
2 M Na CO into dilute HCl, results in tarring and
1
tained. As follows from the H NMR data, the frac-
tion soluble in methanol is a mixture of partially de-
graded or incompletely substituted cyclic and acyclic
products. The fraction insoluble in methanol is the
1
target product; yield 0.25 g (27%), mp >360 C. H
NMR spectrum (300 MHz, DMSO, 25 C), , ppm:
7.97 s (2H, C H), 5.13 br (1H, OH), 4.00 s (2H,
3
2
4
ar
CH ).
2
Ternary complex poly-1,8-octamethyleneacet-
amidine octa-p-nitrocalix[8]arene UO (OH) . Ni-
2
2
5
trocalix[8]arene (0.02 g, 1.6 10 mol) is dissolved
in 2 ml of acetone, and UO (OH) (0.015 g, 0.5
2
2
4
10 mol) is suspended in 2 ml of acetone. Mixing of
the solution and suspension results in formation of
a soluble binary complex. To the resulting solution,
2 ml of an alcoholic solution of poly-4-vinylpyridine
3
2
3
(0.06 g, 0.5 10 mol) is added. The ternary com-
total decomposition of octa-p-nitrocalix[8]arene. In
this connection, we suggested a modification of this
method, allowing preparation of the desired com-
pound in a reasonable yield (up to 30%). We found
that ipso nitration does not occur at temperatures
below 3 C, whereas above 10 C the reaction becomes
uncontrollable and leads to the ring opening. When
the reaction is performed in the interval 5 7 C, >97%
pure octa-p-nitrocalix[8]arene can be isolated by se-
lective extraction with methanol.
plex is isolated on cooling as a dark orange precipi-
tate. Films of the complex are obtained by casting
onto a rotating support (3000 rpm, 30 s).
Ternary complex polymer calixarene fullerene.
Such ternary complexes can be prepared by two pro-
cedures differing in the order of combining the com-
ponents.
(1) A solution of p-tert-butylcalix[8]arene and
3
poly-1,8-octamethyleneacetamidine (1.2 10
mol)
The possibility of preparing double polymer calix-
arene complexes was examined with octa-p-tert-butyl-
calix[8]arene and octa-p-nitrocalix[8]arene as calix-
arene components, and polyoctamethyleneacetamidine
and poly-4-vinylpyridine, differing in the basicity of
nitrogen-containing moieties, as polymer components.
(calixarene : polymer ratio 1 : 40) in ethanol is pre-
pared. A polymer film is prepared by casting onto
a rotating support. After drying over concentrated
3
H SO , the film is placed in a hot 1.5 10 M solu-
2
4
tion of fullerene (2 mg) in toluene (2 ml). The ternary
complex is formed within 24 h as a gray-brown film.
The product is extracted with two 2-ml portions of
boiling toluene and vacuum-dried.
p-tert-Butylcalix[8]arene is insoluble in ethanol but
soluble in an alcoholic solution of polyamidine (pK
11), which suggests the deprotonation of the macro-
cycle and formation of an ionic bond between the
calixarene and polymer. As seen from Fig. 1, in a rel-
(2) Fullerene (1 mg) is dissolved in 2 ml of tolu-
ene on refluxing for 2 h. To the refluxing solution,
2 mg of p-tert-butylcalix[8]arene is added to obtain
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 9 2006

1496
TEN’KOVTSEV et al.
comb-shaped ionic complex. Apparently, owing to the
d, nm
steric factors associated with the size and shape of the
calixarene, the maximal capacity of the polymer for
the calixarene should be considerably lower than the
theoretical value (1 mol of polymer units per mole of
calixarene). Polarization-optical examination of the
complexes shows that the system becomes two-phase
at polymer : calixarene ratios less than 30 : 1, which is
in good agreement with the dynamic light scattering
data.
Mixing of an alcoholic solution of poly-4-vinyl-
pyridine with p-tert-butylcalix[8]arene does not lead
to their reaction, because of insufficient basicity of the
polymer (pK 9).
Fig. 1. Diameter d of particles of polyoctamethyleneacet-
amidine octa-p-tert-butylcalix[8]arene complex as a func-
tion of the polymer : macrocycle ratio A.
Octa-p-nitrocalix[8]arene (pK <0, pK 2.6, pK 7.2
1
2
3
3
[6]) is sparingly soluble in ethanol ( 3.2 10 M).
On mixing alcoholic solutions of the macrocycle and
a polymer (both polyamidine and poly-4-vinylpyri-
dine), a polymer calixarene complex precipitated,
suggesting the binding of the polymer with the calix-
arene via several hydroxy groups and formation of a
three-dimensional ionic network. Figure 2 shows the
spectra of the starting polyamidine, octa-p-nitrocalix-
[8]arene, and their complex in DMF solutions. As
seen, the spectrum of the complex differs essentially
from those of the components, confirming the ionic
interaction in the system. Figure 3 shows that the
electronic spectra of octa-p-nitrocalix[8]arene depend
on pH strongly and in a complex fashion, suggesting
successive deprotonation of several hydroxy groups.
It should be noted that the number of deprotonated
groups in the nitrocalix[8]arene molecule is as follows
[6], at pH 0, 0; at pH 6.0, 1; at pH 9.7, 2 or 3; and
at pH 13.0, 4 or more. Comparison of the electronic
spectrum of the complex with those of octa-p-nitro-
calix[8]arene suggests that the interaction involves
two or three hydroxy groups of the macrocycle.
, nm
Fig. 2. Absorption spectra of (1) polyoctamethyleneacet-
amidine, (2) octa-p-nitrocalix[8]arene, and (3) their com-
plex. (D) Optical density and ( ) wavelength; the same for
Figs. 3 and 5.
Thus, our data show that variation of the basicity
of the polymer and acidity of the hydroxy groups of
calixarene can lead to the formation of both comb-
shaped and cross-linked structures (Scheme 1).
The possibility of formation of ternary ion ion
complexes in a calixarene polymer metal ion system
was examined with the system poly-4-vinylpyridine
, nm
2+
octa-p-nitrocalix[8]arene UO
as example. The
2
Fig. 3. Absorption spectra of octa-p-nitrocalix[8]arene at
pH (1) 6.0, (2) 0, (3) 9.7, and (4) 13.
choice of this system was governed by the fact that
the less acidic octa-p-tert-butylcalix[8]arene does not
form sufficiently stable complexes with uranyl ion, as
judged from the identity of the luminescence spectra
of a mechanical mixture of octa-p-tert-butylcalix[8]-
arene and the residue after evaporation of a solution of
atively wide range of calixarene : polyamidine ratios
(up to 1 : 40, counting for functional groups), no
colloidal particles are formed, which suggests mono-
deprotonation of the macrocycle and formation of a
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 9 2006

SUPRAMOLECULAR POLYMERIC COMPLEXES OF CALIX[8]ARENES
1497
Scheme 1. Formation of binary complexes
the components in DMSO ethanol. However, the re-
action of an alcoholic solution of octa-p-tert-butyl-
calix[8]arene with UO (OH) is accompanied by the
are bound by a combination of ionic and hydrophilic
hydrophobic interactions was examined with the octa-
p-tert-butylcalix[8]arene poly-1,8-octamethyleneacet-
2
2
amidine C system as example. The complexes were
dissolution of UO (OH) , formation of a 1 : 1 com-
60
2
2
prepared by two pathways: treatment of the octa-p-
tert-butylcalix[8]arene poly-1,8-octamethyleneacet-
amidine complex with a boiling solution of fullerene
in toluene and treatment of the polyamidine with a hot
solution of the calixarene fullerene complex in tolu-
ene. Both procedures yielded the ternary complexes.
Figure 5 shows the electronic spectra of the binary
complexes fullerene octa-p-tert-butylcalix[8]arene
and poly-1,8-octamethyleneacetamidine octa-p-tert-
butylcalix[8]arene and of the ternary complex. It is
seen that the spectrum of the ternary complex fuller-
plex (according to elemental analysis), and disappear-
ance of the characteristic luminescence spectrum of
the uranyl ion, consisting of several well-resolved
lines (Fig. 4). The high acidity of octa-p-nitrocalix-
[8]arenes (first, pK <0, and second, pK 2.6, dissoci-
1
2
ation steps) suggests that two hydroxy groups of the
2+
macrocycle act as anionic ligands for UO , four less
2
acidic OH groups act as donor acceptor ligands, and
the remaining two phenolic groups do not participate
in the complexation. It should be noted that the equiv-
alence of all the hydroxy groups of the macrocycle
does not allow us to clearly distinguish the role of
each particular OH group of the calixarene in the com-
plexation.
I, arb. units
On mixing alcoholic solutions of the polyamidine
2+
and UO octa-p-nitrocalix[8]arene complex, the ter-
2
2+
nary complex UO octa-p-nitrocalix[8]arene poly-
2
amidine precipitates. Its qualitative composition is
suggested by a broad band with a maximum at about
500 nm, appearing in the luminescence spectrum
(Fig. 4). The appearance of the luminescence is prob-
ably associated with the electron density redistribution
2+
in the interaction of the UO octa-p-nitrocalix[8]-
2
arene complex with highly basic polyamidine, result-
ing in the deprotonation of the hydroxy groups of the
macroring that are not involved in ionic bonding with
uranyl ions (Scheme 2).
, nm
Fig. 4. Luminescence spectra of (1) uranic acid, (2) com-
plex of UO with octa-p-nitrocalix[8]arene, and (3) terna-
ry complex UO octa-p-nitrocalix[8]arene polyoctameth-
yleneacetamidine. (I) Intensity and ( ) wavelength.
2+
2
2+
The possibility of preparing ternary polymeric
complexes of calixarenes in which the components
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 9 2006

1498
TEN’KOVTSEV et al.
Scheme 2. Formation of ternary (a) hydrophilic-hydrophobic and (b) ion ion complexes
(a)
(b)
ene poly-1,8-octamethyleneacetamidine octa-p-tert-
butylcalix[8]arene is a superposition of the spectra of
the binary complexes. This fact indicates that both
procedures allow preparation of ternary complexes
combining the ionic and hydrophobic hydrophilic
binding of the components (Scheme 2).
taking into account the fact that the fullerene p-tert-
butylcalix[8]arene complex is soluble in toluene and
decomposes in polar solvents [7].
Thus, calixarenes are capable of forming ternary
complexes by simultaneous interactions with the func-
tional groups of ionic polymers and guest molecules;
the acidity basicity ratio for the polymer calixarene
system strongly affects the possibility of formation of
ion ion and ion hydrophobic component hydrophilic
component supramolecular structures. We believe that
the suggested route to polymer systems containing
fullerenes can find use in the development of new
materials for optoelectronics and of polymeric sensors
for environmental monitoring.
Both procedures for preparing the ternary complex
yield a stable film resistant to the action of boiling
hydrocarbons (toluene, xylene) but partially degrading
under the action of boiling ethanol. Such a behavior is
also indicative of the formation of a ternary complex,
CONCLUSION
The formation of ionic complexes by interaction
of ionic polymers with calix[8]arenes was studied in
relation to the basicity of functional groups of the
polymer and acidity of those of the macrocycle. The
possibility of formation of ternary supramolecular
complexes ion ion (polymer calixarene uranyl ion)
and ion hydrophilic component hydrophobic compo-
nent (polymer calixarene fullerene) was shown.
, nm
ACKNOWLEDGMENTS
Fig. 5. Electronic spectra of the binary complexes (1) ful-
lerene octa-p-tert-butylcalix[8]arene and (2) poly-1,8-
octamethyleneacetamidine octa-p-tert-butylcalix[8]arene;
(3) spectrum of the ternary complex.
The authors are grateful to Prof. F. Bohme (Insti-
tute of Polymer Research, Dresden, Germany) for sub-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 9 2006

SUPRAMOLECULAR POLYMERIC COMPLEXES OF CALIX[8]ARENES
1499
mission of samples of polyamidines and to Prof.
H. Tenhu (University of Helsinki, Finland) for the
assistance in the experiments.
2. Redshow, C., Coord. Chem. Rev., 2003, vol. 244, no. 1,
pp. 45 70.
3. Li, Q., Callahan, H., and Collins, G.E., Chem. Com-
mun., 2000, no. 10, pp. 1913 1914.
The study was financially supported by the Russian
Foundation for Basic Research (project no. 06-03-
32044-a).
4. Gutsche, C.D., Org. Synth., 1990, coll. vol. 8, pp. 80
82.
5. Kumar, S., Kurur, N.D., Chawla, H.M., and Varadara-
jan, R., Synth. Commun., 2001, vol. 31, no. 5, pp. 775
779.
REFERENCES
6. Bunzli, J.-C. and Ihrenger, F., Inorg. Chim. Acta, 1996,
1. Asfari, Z., Boehmer, V., Harrowfield, J., and Visens, J.,
J. Inclus. Phenom. Macrocyclic Chem., 2002, vol. 43,
nos. 1 2, pp. 149 151.
vol. 246, no. 3, pp. 195 205.
7. US Patent 5711927.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 9 2006