Poly[2]catenanes and cyclic oligo[2]catenanes containing alternating topological and covalent bonds: Synthesis and characterization

Article abstract of DOI:10.1002/(SICI)1521-3765(19990604)5:6<1841::AID-CHEM1841>3.0.CO;2-Q

Large bifunctionalized catenate and catenand, composed of macrocycles containing 45 atoms, have been synthesized and copolymerized with a terephthalic acid derivative to afford a cyclic oligo[2]catenand and a linear poly[2]catenate. Poly[2]catenand was ob

Full text of DOI:10.1002/(SICI)1521-3765(19990604)5:6<1841::AID-CHEM1841>3.0.CO;2-Q

FULL PAPER
Poly[2]catenanes and Cyclic Oligo[2]catenanes Containing Alternating
Topological and Covalent Bonds: Synthesis and Characterization
Jean-Luc Weidmann,[a] Jean-Marc Kern,*[a] Jean-Pierre Sauvage,*[a] Dirk Muscat,[b]
Susan Mullins,[b] Werner Köhler,[b, c] Christine Rosenauer,[b] Hans Joachim Räder,[b]
Kai Martin,[b] and Yves Geerts*[b, d]
Abstract: Large bifunctionalized cate-
nate and catenand, composed of macro-
cycles containing 45 atoms, have been
synthesized and copolymerized with a
terephthalic acid derivative to afford a
cyclic oligo[2]catenand and a linear
poly[2]catenate. Poly[2]catenand was
obtained by demetalation of poly[2]-
catenate. The molecular weight distri-
bution of these polymers, which are
composed of alternating topological
and covalent bonds, has been character-
ized by gel permeation chromatography
(GPC) with universal calibration, visc-
ometry, and MALDI-TOF mass spec-
trometry. We were able to synthesize a
poly[2]catenate and a poly[2]catenand
with a degree of polymerization (DP)
equal to 8 ± 9. In addition, an upper
value of the Kuhn segment length of
poly[2]catenand has been determined
and is discussed in the light of its
structure.
Keywords: catenanes
´ copper ´
polycondensations ´ structure eluci-
dation ´ supramolecular chemistry
Introduction
In the course of the last fifteen years, intense research efforts
have been devoted to the synthesis and characterization of
topologically and structurally appealing molecules, such as
catenanes 1, rotaxanes 2, and knots 3[1] (Scheme 1). All these
types of molecules contain defined topological or mechanical
bonds between some of their subunits, without the involve-
ment of covalent bonds.[2]
1
2
3
Conversely, entanglements that take place between poly-
mer chains in the solid state and in concentrated solutions
result from the statistical behavior of macromolecules and are
not defined at the molecular level. Therefore, the schematic
drawing of an entanglement 4, shown in Scheme 1, certainly
oversimplifies a complex reality since entanglements are
4
5
[a] Dr. J.-M. Kern, Dr. J.-P. Sauvage, Dr. J.-L. Weidmann
Â
Â
Laboratoire de Chimie Organo-Minerale, UMR 7513 CNRS Faculte
n
n
Â
de Chimie, Universite Louis Pasteur
7
6
4, rue Blaise Pascal, F-67000 Strasbourg (France)
Fax: (‡33)3-88-41-61-30
E-mail: sauvage@chimie.u-strasbg.fr
[b] Dr. Y. Geerts,[‡] Dr. D. Muscat, Dr. S. Mullins, Dr. W. Köhler,[‡‡]
Dr. C. Rosenauer, Dr. H. J. Räder, Dr. K. Martin
Max-Planck-Institute for Polymer Research
Ackermannweg 10, D-55128 Mainz (Germany)
‡
n
8
Â
[ ] Present address: Universite Libre de Bruxelles, Laboratoire de
Â
Chimie Macromoleculaire, CP 206/1
Scheme 1. Schematic drawings of topological bonds that occur in molec-
ular and macromolecular systems: [2]catenane 1, rotaxane 2, trefoil
molecular knot 3, entanglement 4, interpenetrating polymer network 5,
polyrotaxane 6, polycatenane 7, and poly[2]catenane 8.
Boulevard du Triomphe, B-1050 Bruxelles (Belgium)
‡‡
[
]
Present address: Physikalisches Institut Universität Bayreuth
D-95440 Bayreuth (Germany)
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J.-M. Kern, J.-P. Sauvage, Y. Geerts et al.
FULL PAPER
nonlocalized and dynamic in nature. However, they play a
central role in polymer physics and must be considered to
govern the mechanical properties,[3a] the rheology,[3b] and the
dynamics[4] of the polymers. A closely related example of a
complex system that results from nondefined topological
bonds is given by interpenetrating polymer networks 5 which
are composed of two independent networks that are mechan-
ically connected to each other by mutual interpenetration.[5]
Only a limited number of macromolecular architectures
contain defined topological bonds, namely, polyrotaxanes 6,[6]
polycatenanes 7, and poly[2]catenanes 8.[7] In the case of
polyrotaxanes, the topological bonds occur between the
polymer chain and the macrocycles. Consequently, the
properties of polyrotaxanes, although strictly different from
those of their individual components, deviate only partially
from the main stream of polymer properties. In particular, the
rupture of a single topological bond will not substantially
affect the macromolecular structure of the polyrotaxane
backbone. Polycatenanes 7 and poly[2]catenanes 8 are
structurally different from polyrotaxanes 6 since they contain
topological bonds in the main chain, and breaking one or
several topological bonds will result in the degradation of the
polymer. Clearly, the interest in polycatenanes and poly[2]-
catenanes goes beyond their structures, since catenane units
contain new elements of mobility which result from the free
rotational and elongational motions of one macrocycle within
the other. To date, there have been no reports of any polymers
that contain such molecular knee-joints. Thus, the dynamics
and viscoelastic properties of polycatenanes and poly[2]cate-
nanes are anticipated to deviate strongly from those of more
conventional polymer architectures. Specifically, it is antici-
pated that poly[2]catenanes will exhibit unusual viscoelastic
properties, for example, a very large loss modulus, low
activation energy for viscous flow, and rapid stress relaxation
as a consequence of the presence of the mobility elements
contained in the catenane units.
a)
Y
X
X
Y
Y
Y
A
+
A
X
A
X
Y
A
A
A
Y
9
b)
A
n
B
B
A
+ n
10
9
A
A
B
B
n
8
Scheme 2. Synthetic strategy leading to poly[2]catenane 8.
O
O
O
O
O
O
O
O
O
N
N
R
N
R
N
R
O
R
O
O
O
O
R
R
N
R
N
R
N
N
O
n
O
11 : R = CH3
Several attempts towards the daunting synthetic challenge
of high molecular weight polycatenanes have been made in
the past.[1c, 7] However, the lack of efficient characterization
methods, combined with nonselective synthetic strategies
resulted in intractable and ill-characterized materials.[8] An
outstanding forerunner of a real polycatenane is the olympia-
dane of Stoddart et al.; this is an oligocatenane of exact
molecular weight and is composed of five repeat units.[9]
The synthesis of poly[2]catenanes 8 that contain alternating
topological and covalent bonds does not encounter any
conceptual difficulties since they can be made according to
the general pathway presented in Scheme 2.[7] The synthesis
involves the preformation of a difunctionalized catenane 9
and its subsequent copolymerization with a spacer 10.
Hitherto, only a limited number of poly[2]catenanes have
appeared in the literature.[10±12]
Some of us have already reported the synthesis of the
poly[2]catenate 12a and the poly[2]catenand 12b, (a catenate
is a complex whose ligands consist of interlocking rings,
whereas catenand is a free ligand) based on a highly mobile
catenane that contains very large macrocycles of 45 atoms
(Scheme 3).[11] More recently, some of us synthesized the
poly[2]catenane 11 based on a highly rigid amide-type
O
O
O
O
O
O
O
O
O
O
O
R
R
R
O
N
O
N
N
M
O
n
N
O
R
O
O
O
O
O
O
O
O
O
A
12a M = Cu+, A = PF6- , R = n C6H13
12b M absent , A absent , R = n C6H13
KCN /
THF
Scheme 3. Previously reported poly[2]catenane 11 and poly[2]catenate
12a and poly[2]catenand 12b.[10, 11] Poly[2]catenand 12b is obtained by
demetalation of 12a (KCN, THF, room temperature).
catenane that comprises macrocycles of only 32 atoms.[10] In
the case of poly[2]catenane 11, the relative motions of the
macrocycles of the catenane units are frozen due to the
presence of the methyl groups on the amide functions.
Characteristically, poly[2]catenane 11 and poly[2]catenand
12b represent two extreme situations where the mobility
contained in the catenane units varies importantly. In
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Poly[2]catenanes
1841±1851
particular, it is anticipated that the comparison of poly[2]-
catenane 11 with poly[2]catenand 12 will make evident the
unusual viscoelastic properties expected from the presence of
catenane units in the polymer backbone.
Here, we describe the detailed synthesis of poly[2]catenate
12a and poly[2]catenand 12b and the comprehensive inves-
tigation of their macromolecular characteristics. This work is
intended to pave the way for the production of large amounts
of well-characterized poly[2]catenanes for physical studies
and represents the first step of a general research program,
aimed at the fundamental study of the unusual viscoelastic
properties and dynamics resulting from the introduction of
topological bonds into a polymer main chain.
O
O
a
c
O
e
O
O
O
O
3
O
O
O
A
B
N
N
N
X
5
M
b
d
f
O
X
N
φ
ε
O
O
δ
O
O
O
χ
A
β
α
m1 o2 m2
M = Cu+
M = nil
A = PF6
A = nil
-
13a
13b
14a
14b
X = CH2OH
X = CH2OH
M = Cu+
M = nil
-
X = CO2Me
X = CO2Me
A = PF6
A = nil
Results and Discussion
O
O
HO
HO
O
Design and synthesis of the polymer precursors: The three-
dimensional template effect of copper(i) ions, introduced by
some of us 15 years ago, made catenanes and related systems
reasonably accessible from a preparative viewpoint.[13] The
strategy, based on a precursor that consists of two phenan-
throline-type ligands entwined around a copper(i) center,
allows the preparation of gram-quantities of the interlocking
ring systems in a few steps.
O
N
N
N
CO2Me
N
O
O
O
O
15
16
Scheme 4. Catenate monomer 13a, catenand monomer 13b, and their
The original [2]catenane that contains two thirty-mem-
bered rings could not be used in the frame of the work
described in the present report because: i) the appropriate
functional groups had to be introduced at the correct
positions, that is in an antipodal arrangement with respect
to one another and ii) the size of the interlocking rings had to
be increased.
synthetic precursors.
15
+
16
+
Cu (CH3CN)4
OH
The difunctionalized copper [2]catenate 13a is based on
two identical interlocking macrocycles with 2,9-diaryl-1,10-
phenanthroline moieties coordinated to the metal center in a
tetrahedral geometry. In order to ensure pronounced mobility
of the demetalated system (the poly[2]catenand), these
macrocycles were designed so as to be rigid and large. The
rigidity requirement was satisfied by substituting the 2,9-
positions of the phenanthroline core with p-biphenyl nuclei.
These are linked through their p'-positions to a 5-functional-
ized (hydroxymethyl) resorcinol by triethyleneglycol chains.
The resulting macrocycles are thus 45-membered rings
(Scheme 4). Since the solubility of polymeric materials is an
essential condition for their physicochemical characterization,
lipophilic groups (n-hexyl chains) were introduced on the 4
and 7 positions of the phenanthroline core,[14] so as to
counterbalance the effects of 1,10-phenanthroline and bi-
phenyl units.
O
O
O
O
O
O
N
N
MeO2C
Cu
N
N
O
O
OH
Cu [15.16] +
O
O
O
I
MeO2C
Cs2CO
3 / DMF
O
O
O
I
17
14a
The principle of the synthesis of the coordinating inter-
locking molecules is based on the elaboration of a highly
preassembled system and on the generalized three-dimen-
sional template effect mentioned above.[13] In our case, the
‡
HDibal
HDibal
catenate precursor is the threaded precursor [Cu(15 ´ 16)]
14a
13a
13b
(Scheme 5), which is obtained quantitatively by threading 4,7-
di-(n-hexyl)-2,9-di-[4'-(p-hydroxyphenyl)phenyl]-1,10-phe-
nanthroline (16) through the macrocycle 15 by the use of
[Cu(CH3CN)4PF6] as the template agent.
-
CN
14a
14b
Scheme 5. Synthesis of catenate monomer 13a and catenand monomer
13b.
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J.-M. Kern, J.-P. Sauvage, Y. Geerts et al.
FULL PAPER
The cyclization of this pseudorotaxane is the key step in the
synthesis of the poly[2]catenate precursor 13a. Under rela-
tively mild reaction conditions, copper [2]catenate 14a was
OH
‡
X
X
O
O
O
O
O
O
obtained in 55% yield from the reaction of [Cu(15 ´ 16)] with
N
N
the dielectrophile 17 in dimethylformamide (DMF) in the
presence of Cs2CO3 as a base. The bis(hydroxymethyl)-
functionalized copper [2]catenate 13a was then obtained by
the reduction of 14a with diisobutylaluminum hydride
(HDibal). Catenand 13b was prepared by demetalation of
13a to give 14b, followed by reduction of the ester groups
using HDibal again, in tetrahydrofuran.
The synthesis of the diphenolic compound 16 is described
elsewhere.[15] The dielectrophile 17 was prepared in the
following manner (Scheme 6): methyl 3,5-dihydroxybenzoate
CO2Me
+
OH
16
17
Cs2CO3
/ DMF
O
O
O
OH
O
iv
iii
ii
i
20
17
N
N
19
18
MeO2C
CO2Me
O
OH
O
O
O
18
19
X = OTHP
X = OH
X = OMs
X = I
O
O
O
O
O
X
X
15
Scheme 7. Synthesis of the macrocycle 15.
MeO2C
20
17
O
R'
Scheme 6. Synthetic pathway to dielectrophile 17: i) Cl(-CH2-CH2-O)3-
THP, NaH, DMF; ii) pyridine ´ HCl, EtOH; iii) MsCl, Et3N, CH2Cl2;
iv) NaI, acetone.
i)
HO
O
O
12a,b
22a,b
13a,b
+
+
OH
R'
R'
=
O
O
21
was treated with the OTHP derivative of 2-[2-(2-chloroethox-
y)ethoxy]ethanol in a basic medium to afford 18. Acidic
cleavage of 18 led to the dialcohol 19, which was successively
mesylated (compound 20) and transformed into the diiodo
compound 17 by treatment with excess NaI. The synthesis of
the macrocycle 15 (Scheme 7) was based on the reaction of
the nucleophilic diphenolate derivative of 16 with the
dielectrophile 17 under conditions of high dilution (53%
yield).
O
O
O
O
O
O
R'
O
O
O
O
N
O
N
N
M
n
O
N
O
O
R'
O
O
A
O
O
O
O
12a,b
a M = Cu+, A = PF6
b M absent , A absent
-
A rigid diacid was designed as a structural unit to connect
the catenate or catenand moieties in the polymers. This diacid
21 (see Scheme 8), which is a derivative of terephthalic acid,
bears four tert-butyl groups in order to provide good solubility
for the diacid in the polymerization solvent (dichloro-
methane) and to contribute to the solubility of the poly-
mers.[10, 11]
O
O
O
O
O
O
O
O
N
N
N
A
M
N
O
O
O
O
O
O
O
O
R'
O
O
O
O
22a,b
R'
n
Polymer synthesis and characterization: The copolymeriza-
tion of catenate 13a or catenand 13b with the highly soluble
terephthalic spacer 21 was carried out with the polyesterifi-
cation method of Moore and Stupp (Scheme 8).[10a, 16] This
mild polymerization method, which uses N,N'-diisopropylcar-
bodiimide as a dehydrating agent and 4-(N,N'-dimethylami-
no)pyridinetoluene-p-sulfonic acid 1:1 complex as a catalyst,
has the advantage of functioning in dichloromethane, a
solvent in which catenate 13a is especially soluble. The
polymerization products were soluble in chlorinated solvents,
-
a M = Cu+, A = PF6
b M absent , A absent
Scheme 8. Synthesis of oligo- and poly[2]catenates (12a, 22a) and oligo-
and poly[2]catenands (12b, 22b). i) 4-(N,N'-dimethylamino)pyridine/p-
toluenesulfonic acid 1:1 complex, N,N'-diisopropylcarbodiimide.
N,N'-dimethylformamide, and tetrahydrofuran; no insoluble
fraction was observed. The purification was carried out by
precipitation in a large volume of methanol.
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Poly[2]catenanes
1841±1851
Cyclic oligo[2]catenand 22b: The polymerization of catenand
13b was conducted for three days at 108C, then two days at
08C, and finally one day at room temperature to afford the
cyclic oligo[2]catenand 22b in 77% yield. The structure of the
namely, the acid function of the spacer and the alcohol
function of the catenand, the mobility of the macrocycles of
the catenand units preferentially allows an intramolecular
cyclization rather than an intermolecular reaction which
would lead to an increase in the molecular weight.[12b] This
documents, however, the chemical reactivity of the catenanes,
whereby the reactivity of a functional group on a macrocycle
is influenced by the presence of another functional group on
the other macrocycle.[1e, 18]
1
oligo[2]catenand 22b was elucidated by H and 13C NMR
spectroscopy, gel permeation chromatography (GPC), and
viscometry.
In the 1H NMR spectrum of the polymerization product of
catenand 13b, all peaks were broadened compared to those of
the corresponding monomers, as expected for oligomers or
polymers. Typical resonances of the terephthalic ester spacer
and of the interlocked macrocycles were present and no
evidence of ring-opening or dethreading during polymeriza-
tion was observed. New resonances appeared, namely the
benzyl ester protons at d ˆ 5.17, and no benzyl proton signal at
d ˆ 4.43 for the catenand 13b was present in the correspond-
ing polymer spectra. Accordingly, the 13C NMR spectra
indicated that the characteristic resonance of the carboxyl
carbon atom of the acidic moiety at d ˆ 163.8 was shifted to
d ˆ 164.9 for the ester groups. The absence of end groups can
be caused by either high molecular weight poly[2]catenand
12b, by cyclic oligo[2]catenand 22b, or by a mixture of both.
Evidence for the presence of
Poly[2]catenate 12a: The polymerization of catenate 13a was
carried out at 208C for six days to afford the poly[2]catenate
1
12a in 94% yield. The structure was elucidated by H and
13C NMR spectroscopy, as well as by matrix-assisted laser-
desorption time-of-flight mass spectrometry (MALDI-TOF
MS).[19]
The characteristic features of the 1H spectrum of the
poly[2]catenate 12a (Figure 1) are: i) all peaks were broad-
ened compared to their corresponding monomers, as expected
for polymers; ii) typical resonances of the interlocked macro-
cycles of the catenane monomer were present which indicates
cyclic oligo[2]catenand 22b
was provided by GPC (Diol
columns (Merck), in N,N'-di-
methylformamide
which indicated
(DMF))
number-
a
average molecular weight
(Mn) of only 2500. Even if the
more compact structure of cat-
enane segments with respect to
polystyrene standards is con-
sidered, these GPC data show
that only oligomers have been
obtained. Previously reported
GPC data in chloroform[11]
overestimated the presence of
high molecular weight poly-
mers, namely number-average
molecular weight (Mn ˆ 4.2 Â
103) and weight-average mo-
lecular weight (Mw ˆ 1.8  106).
Figure 1. 1H NMR spectrum of poly[2]catenate 12a in CDCl3 at 500 MHz (s ˆ solvent).
Presumably, as a result of the acidic character of chloroform,
protonation of the phenanthrolines of the catenane units leads
to the formation of strong dipolar moments on the oligomers
which then aggregate by dipole ± dipole interactions and,
therefore, bias the molecular weight distribution.[17] The
viscometry study in DMF indicated that no significant
increase in the viscosity was observed, corroborating the
conclusions made from the GPC data that only oligomers
were reached. Therefore, it is concluded that cyclic oligo[2]-
catenands 22b were obtained which explains the absence of
that no ring opening and dethreading has occurred during the
polymerization; iii) resonances attributed to the diacyl moiety
were also observed; iv) new resonances appeared, namely
benzyl ester protons at d ˆ 5.25; v) in agreement, 13C NMR
spectra indicated that the characteristic resonance of the
carboxyl carbons of the acid moieties at d ˆ 163.8 was shifted
to d ˆ 165.0 characteristic for ester groups. The end-group
analysis of the 1H spectrum revealed that a low-intensity
resonance at d ˆ 4.63, attributed to the benzyl protons of
catenate end groups was observed. Assuming the equiprob-
able occurrence of catenate and spacer end groups, integra-
tion gives a relative concentration of end groups of 4%. Since
the formation of cyclic and linear oligo- and poly[2]catenates
are possible, a reliable average degree-of-polymerization
(DP) cannot be derived (see below). The use of Carotherꢁs
equation, DP ˆ 1/(1 p), which relates DP to the yield p, is
1
end groups evidenced from H and 13C NMR spectroscopy.
It is easily understandable from the mobility of the macro-
cycles of the catenand that cyclic oligo[2]catenands 22b are
formed preferentially over linear oligo- and poly[2]catenands
12b. In the course of the polyesterification reaction, when an
oligo[2]catenand carries two complementary end groups,
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J.-M. Kern, J.-P. Sauvage, Y. Geerts et al.
FULL PAPER
meaningless because of the low amount of monomers used for
the polymerization and the unavoidable loss of polymer upon
precipitation and filtration.
teristic of the phenanthroline copper(i) complex of the
poly[2]catenate 12a.[20]
The 1H NMR spectrum shows the typical resonances of the
terephthalate moiety, of the interlocked macrocycles, and the
presence of benzyl alcohol protons at d ˆ 4.38, which are
attributed to catenand end groups. Assuming the equiprob-
able occurrence of catenate and spacer end groups, then
integration gives a relative abundance of end groups of 4%.
The same end-group concentration for the poly[2]catenate
12a and the poly[2]catenand 12b demonstrates, within the
limit of experimental error, that no benzyl ester hydrolysis
took place during demetalation. It is, therefore, suggested that
the molecular weight distribution of poly[2]catenand 12b
accurately represents that of poly[2]catenate 12a. The
13C NMR spectrum exhibits, besides the characteristic reso-
nance of ester groups at d ˆ 165.0, a comparable resonance
pattern to oligo[2]catenand 22b. Definite evidence of the
presence of high molecular weight poly[2]catenand 12b is
provided by viscometry and GPC in DMF. In particular, the
specific viscosity, nsp, increased with concentration, which is
typical for high molecular weight polymers. Extrapolation to
zero concentration yields a value of intrinsic viscosity
A previous attempt[11] to characterize the molecular weight
distribution of poly[2]catenate 12a by GPC in chloroform
gave the values Mn ˆ 5.5  104 and Mw ˆ 1.8  106. However,
poly[2]catenate 12a contains one copper(i) complex and the
PF6 counterion per repeat unit; their presence creates strong
dipole moments along the oligomer and polymer chain.[17] It is
expected that aggregation as a result of dipolar interactions
occurs and leads to an overestimation of the molecular weight
distribution. This holds, of course, for other characterization
methods in solution, such as light scattering, osmometry, and
viscometry, which are all hampered by aggregation.[17] MAL-
DI-TOF MS has the advantage of being insensitive to
aggregation phenomena in solution[17] and thus was used to
investigate the molecular weight distribution of poly[2]caten-
ate 12a. Interestingly, signals that correspond to oligo[2]-
catenates with n ˆ 1 ± 4 were successfully observed. Theoret-
ical masses and experimental values for n ˆ 1 ± 4 are presented
in Table 1.
1
reaching 1.09 cLg . The macromolecular character-
Table 1. Theoretical and MALDI-TOF experimental masses of the poly[2]catenate
12a.[a]
istics of poly[2]catenand 12b are presented in Table 2.
Standard calibration with polystyrene gave the values
‡
‡
‡
‡
‡
n(SC )n ´ (X )n 1, (SC )n ´ (X )n
(SC )n S ´ (X )n
C
(SC )n ´ (X )n
1
1
1
Mn ˆ 16500, Mw ˆ 30500 Da and peak molecular weight
at Mp ˆ 37500 Da. These values are very probably
underestimated because of the more compact structure
of poly[2]catenand 12b compared to a polystryrene coil
of similar molecular weight.[10a] A universal calibration
was used to circumvent this problem.[21] The principle of
the universal calibration relies on the observation that
in a given solvent, the product of the intrinsic viscosity
[h] times the molecular weight M is a direct measure of
the hydrodynamic volume of the polymer coil, and
cyclic
22a
linear
12a
linear
12a ‡ 21
[b], (3458)
[b], (6399)
[c], (9340)
linear
12a ‡ 13a
5113 (5111)
8056 (8052)
[c], (10993)
[c], (13934)
1
2
3
4
2797 (2796)
5740 (5737)
8678 (8678)
11700[d] (11619) 11700[d], (11637) [c], (12281)
2814 (2814)
5756 (5755)
[c], (8696)
‡
[a] C ˆ catenate, S ˆ spacer, X ˆ PF6 , the number given in brackets is the
theoretical mass. [b] Peaks not observed. [c] Very low signal-to-noise ratio. [d] Low
signal-to-noise ratio.
An important feature is the formation of both linear and
cyclic oligo[2]catenates for n ˆ 1 and 2. Indeed, a space-filling
model indicates that oligo[2]catenate 22a, which contains
only one repeat unit, does not lead to a dramatic strain
Table 2. Macromolecular characteristics of poly[2]catenand 12b from
GPC in DMF
Calibration
Mn
DP
Mw
Mp
Mw/Mn
because of the high flexibility of polyether bridges. No
indication of any cyclic species could be obtained for n ˆ 3
and 4 owing to a poor resolution of the corresponding signals.
The absence of signals for n > 4 does not rule out the existence
of higher oligo- and poly[2]catenates; it simply shows that
they are not observable by MALDI-TOF MS (see below).
Thus, the exact molecular weight distribution of oligo- and
poly[2]catenates is not directly accessible because of their
strongly polar character and the intrinsic limitation of
MALDI-TOF MS. Clearly, only an indirect characterization
is possible, namely, the demetalation of poly[2]catenate 12a to
yield poly[2]catenand 12b.
polystrene standard
16500
22000
25000
6
8
9
30500
47000
42000
37500
63000
55000
1.85
2.12
1.68
1
a ˆ 0.5, K ˆ 0.0494 mLg
1
a ˆ 0.8, K ˆ 0.002 mLg
determines the retention time in the chromatographic col-
umn.[21] Since the chains of poly[2]catenand 12b may be
swollen in DMF to a different extent compared to a
polystryrene standard of equal molecular weight, the hydro-
dynamic volumes will not necessarily be equivalent.[22a] This
can be compensated for by applying a correction based on the
Mark ± Houwink ± Sakurada equation[22] [Eq. (1)], which re-
lates [h] to M, and K and a are system-specific constants that
Poly[2]catenand 12b: The poly[2]catenand 12b was obtained
in 81% yield by the reaction of poly[2]catenate 12a with a
large excess of potassium cyanide in tetrahydrofuran at room
temperature for one day (Scheme 3). The course of the
reaction was monitored by the disappearance of the metal-
to-ligand charge-transfer band at l ꢀ 440 nm which is charac-
[h] ˆ KMa
(1)
depend on the polymer, solvent, and temperature. Equa-
tion (1) contains two unknowns: K and a, whereas only the
intrinsic viscosity [h] of the poly[2]catenand 12b is known.
1846
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Poly[2]catenanes
1841±1851
Therefore, the problem remains unresolved.[23] However,
while no unique solution can be obtained, reasonable
estimates are possible by employing the two limiting values
of a: it is well-established for flexible polymers at room
temperature that 0.5 ꢁ a ꢁ 0.8, depending on the solvent
quality. Notably, a ˆ 0.5 corresponds to q conditions, that is, a
solvent in which the polymer under investigation is close to
precipitation, and a ˆ 0.8 corresponds to a random coil in a
good solvent.
It can be seen from Figure 2 that the molecular weight
distribution is not strongly influenced by the choice of a.
Specifically, a ˆ 0.5 yields Mn ˆ 22000 Da which corresponds
to a DP of 8, Mw ˆ 47000 Da, and peak molecular weight at
Figure 3. MALDI-TOF mass spectrum of poly[2]catenand 12b (n refers
to ˆ (spacer± catenand)n with n ˆ 1,2,3 to 15; * refers to (spacer± cate-
*
nand)n ± spacer; refers to catenand ± (spacer± catenand)n).
12b terminated by two spacers and two catenane end-groups
were also acquired; however, they are of lower intensity and
appear broader.
To summarize this section, the copolymerization of cate-
nand 13b with the spacer 21 leads preferentially to the
formation of cyclic oligo[2]catenates 22b because of the high
relative mobility of the constitutive macrocycles of catenand
13b. Conversely, the polymerization of catenate 13a with the
spacer 21 proceeds successfully to afford high molecular
weight poly[2]catenates 12a. The highly polar nature of
poly[2]catenate 12b renders its characterization difficult.
Fortunately, the facile demetalation reaction allows the
transformation of poly[2]catenate 12a into poly[2]catenand
12b without degradation, and thus its full characterization.
Figure 2. GPC trace in DMF of poly[2]catenand 12b relative to polystyr-
ene calibration (dotted line), and with a universal calibration where a ˆ 0.5
(solid line) and a ˆ 0.8 (bold solid line).
Solution properties of poly[2]catenand 12b: It is expected
that the properties in solution and, in particular, the overall
conformation of poly[2]catenand 12b will reflect the unusual
mobility elements that result from the introduction of
topological bonds into a polymer main chain.[10b] The mobility
elements present in a catenane unit are depicted in Figure 4.
Mp ˆ 63000 Da. While a ˆ 0.8 affords comparable values: that
is, Mn ˆ 25000 Da which corresponds to a DP of 9, Mw ˆ
42000 Da, and Mp ˆ 55000 Da. The molecular weight aver-
ages calculated with universal calibration are considerably
higher than the values obtained with polystyrene standards;
this corroborates the suggested compact structure of 12b. The
polydispersity index (Mw/Mn) is slightly more sensitive to the
choice of a: namely 2.1 and 1.7 for a ˆ 0.5 and 0.8,
respectively. However, to a first approximation Mw/Mn
remains close to 2.0, which is the generally observed value
for polycondensation products.
The molecular weight distribution of poly[2]catenand 12b
was also investigated by MALDI-TOF MS[19] (Figure 3).
Signals of m/z ꢁ 41000, which correspond to n ˆ 15, were
observed. This in good agreement with the presence of high
molecular weight polymers deduced from GPC. The resolu-
tion of the MALDI-TOF MS spectrum of poly[2]catenand
12b was sufficient to support the presence of the cyclic
oligo[2]catenand and the linear oligo[2]catenand, which bear
a spacer on one side and a catenand on the other in the low
molecular weight tail, up to n ˆ 2, of the molecular weight
distribution. However, the ratio between cyclic and linear
oligomers could not be deduced because of the poor signal-to-
noise ratio. The signals that correspond to poly[2]catenands
Figure 4. The mobility elements contained in catenand monomer units of
12b and 22b: rotational motions b and g, and elongational motion a.
Chem. Eur. J. 1999, 5, No. 6
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J.-M. Kern, J.-P. Sauvage, Y. Geerts et al.
FULL PAPER
One should differentiate between the rotational mobility
elements (b, g) and the elongational mobility element a.
Specifically, g is defined by the angle between the planes of
the catenane macrocycles and corresponds to rocking mo-
tions, which are also present in numerous polymers. On the
other hand, the angle between the two spacers connected to
the catenane unit, b, is an element of mobility which has not
yet been introduced into a polymer main chain. Taking into
account the thickness of the catenane macrocycles, one could
estimate b to vary between 60 and 3008. Therefore, it is
anticipated that little correlation will exist between the spatial
orientation of neighboring monomer segments of poly[2]ca-
tenand 12b and that it will represent the closest synthetic
equivalent of the freely jointed chain model. In this model a
real polymer chain is replaced by an equivalent chain
consisting of N rectilinear segments, the spatial orientations
of which are mutually independent (Figure 5).[24, 25]
units, l is the length of the repeat unit, and Rg the radius of
gyration. The Fox ± Flory equation [Eq. (3)][22] relates the
2
[h] ˆ f(6Rg )3/2/M
(3)
intrinsic viscosity to Rg, where M is the molar mass, f is the
Flory viscosity constant. The combination of Equations (2)
and (3) with the Mark ± Houwink ± Sakurada equation
[Eq. (1)], allows the calculation of lk, where Kq is the
lk ˆ Kq2/3f 2/3Mo/l
(4)
viscosity constant for a ˆ 0.5 and Mo/l the molar mass per unit
1
length. With Kq ˆ 0.0494 mLg
(Table 2), f ˆ 2.7 Â
1 [27]
1
1023 mol , Mo ˆ 2734 gmol , and l ˆ 32 Š, a Kuhn length
of lk ˆ 27 Š is obtained as a crude estimation (Figure6).
This value must be taken as the upper limit, since the
swelling of the polymer coil in a good solvent has not been
taken into account and would result in a further decrease of
lk.[28] Clearly, the unusual elements of mobility of poly[2]-
catenand 12b, that arise from the topological bonds as well as
from the flexibility of the ethyleneoxy bridges and of the
benzyl ester bonds, must be considered to account for the low
value of the Kuhn segment length. Moreover, the upper limit
of lk ˆ 27 Š of poly[2]catenand 12b is comparable to that of a
flexible polymer in a good solvent, for example, lk ˆ 25 Š for
polystyrene in benzene.[29] This observation also confirms that
little correlation exists between the spatial orientation of
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Figure 5. Snapshots of the conformation of the freely jointed chain model
(top) and of the poly[2]catenane (bottom).
The elongational mobility el-
ement, a, is also characteristic
of the relative motions of a
catenane made of large macro-
cycles and is defined as the
maximum allowed translational
degree-of-freedom of one ring,
considered as mobile, within
the other, taken as fixed. In
the present case, taking into
account the ring size and the
thickness of the organic groups,
a could be roughly estimated as
varying freely from 0 to 6 Š.
O
O
O
O
O
O
R
O
O
O
O
N
O
R
O
N
N
O
R
O
N
O
O
O
O
R
O
O
O
O
O
O
R = nC6H13
Figure 6. Estimation of the length of a monomer repeat unit of poly[2]catenand 12b.
Similarly to b, a has not yet
been introduced in a polymer
main chain.
Assuming that the poly[2]catenand 12b can be adequately
represented by the freely jointed chain model, the Kuhn
segment length (lk) has been estimated from GPC and
viscometry results in DMF. The lk value of a polymer chain
is a characteristic of its equilibrium flexibility in a given
solvent. The smaller the Kuhn segment length, the more
flexible is the polymer chain. Typically, lk values range from
15 ± 30 Š for highly flexible polymers to 150 ± 300 Š for rigid
rods.[26] For flexible coils under q conditions, lk is defined
according to Equation (2), where N is the number of repeat
neighboring monomer segments of poly[2]catenand 12b and
that this polymer is correctly described by the Freely Jointed
Chain model (Figure 5). Clearly, these preliminary results on
the Kuhn segment length of the poly[2]catenanes 11 and 12b
stress the importance of the mobility contained in the
catenane units on the conformation of these polymers.
Solid-state properties: Thermogravimetric analysis (TGA)
showed that poly[2]catenate 12a is stable up to 2108C,
whereas oligo[2]catenand 22b and poly[2]catenand 12b
exhibit a higher thermal stability, of up to 3008C. Differential
2
lk ˆ 6Rg /Nl
(2)
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Poly[2]catenanes
1841±1851
channel plate for high resolution analysis of polymers below 10000 Da. The
linear detector consists of a conversion dynode followed by a microchannel
plate, a scintillator, and a photomultiplier. This detector is advantageous
for characterization of the polymer molecular weight distribution. The
matrix for all experiments was 1,8,9-trihydroxyanthracene. Samples were
prepared by dissolving the polymer in CHCl3 at a concentration of
scanning calorimetry (DSC) was performed to investigate the
presence of melting and glass transitions which correspond to
first- and second-order phase transitions, respectively. No
melting transitions were observed for oligo[2]catenand 22b,
poly[2]catenand 12b, and poly[2]catenate 12a in the range
from room temperature to the decomposition temperature. It
is informative to investigate Tg as a function of the oligo- and
poly[2]catenane structure, since the higher the flexibility of
the polymer chain, the lower is the glass transition.[22a]
Specifically, glass transitions, determined from the second
heating curve and taken at the midpoint of the change in heat
capacity, were observed at 758C for oligo[2]catenand 22b and
poly[2]catenand 12b, and at 808C for poly[2]catenate 12a.
The comparison between Tg of poly[2]catenand 12b and
poly[2]catenate 12a indicates that it only slightly decreases on
removal of the copper(i) ion.
1
10 4 molL 1. This solution (10 mL) was added to 10 mL of a 0.1 mmolmL
matrix solution, dissolved in CHCl3. The mixture (1 mL) was applied to the
multistage target and air-dried. The ions were accelerated to 33.65 kV and
in reflection mode, reflected with 35 kV. Polystyrene (Mp ˆ 6000 Da) was
used for an external calibration, immediately before measurement. The
mass accuracy, thus determined, is ꢀ0.05%. Thermal analysis was carried
out on a Mettler DSC30 differential scanning calorimeter (heating rate:
20 Kmin 1). Viscometry was carried out on
viscosimeter in DMF.
a Ubblehode capillary
Solvents and reagents: [Cu(CH3CN)4BF4] was prepared by the reduction of
Cu(BF4)2 with excess Cu powder in CH3CN under argon at room
temperature. The mixture was stirred until the solution was completely
bleached. All other chemicals were of the best grades commercially
available and were used without further purification. The following
compounds were synthesized as described in the literature: 2,5-bis[2-(3,5-
(di-tert-butylphenoxy)ethoxy]terephthalic acid catalyst complex (4-N,N'-
dimethylamino-pyridine/p-toluenesulfonic acid 1:1).[16] Diethyl 2,5-dihy-
droxyterephtalate, dibromoethane, tert-butylphenol, and diisopropylcarbo-
diimide were purchased from Aldrich.
Conclusions
The syntheses of large bifunctional catenate and catenand
monomers and their copolycondensation with a spacer have
been developed. Specifically, catenand monomers lead mainly
to the formation of cyclic oligo[2]catenands 22b, whereas a
linear high molecular weight poly[2]catenate 12a resulted
from the use of catenate monomers. Demetalation of the
poly[2]catenate 12a afforded a poly[2]catenand 12b without
degradation. From a structural viewpoint, poly[2]catenand
12b contains topological and covalent bonds, that is, the
repeat units are mechanically connected to one another. A
reliable and comprehensive structure elucidation of the
oligo[2]catenands 22b, poly[2]catenate 12a, and poly[2]cate-
nand 12b was established. Moreover, a characterization of the
solution properties of poly[2]catenand 12b in DMF was
carried out, and the upper limit of the Kuhn segment length
was found to be 27 Š, which is lower than the length of a
monomer unit (32 Š). In the solid-state, poly[2]catenate 12a
and poly[2]catenand 12b exhibit a glass transition temper-
ature at 808C and 758C, respectively. This synthetic and
characterization work paves the way to the large-scale
production of poly[2]catenanes and the detailed investigation
of their potentially intriguing physical properties.
Compound 18: Sodium hydride (3.27 g, 60% suspended in oil, 82 mmol)
was added to a degassed solution of methyl 3,5-dihydroxybenzoate (6.0 g,
36 mmol) in DMF (100 mL) at room temperature. The mixture was stirred
for 0.5 h and then heated to 858C. To this was added 2-(2'-(2''-chloroe-
thoxy)ethoxy)ethyl 2-tetrahydro-2H-pyran ether (18.95 g, 75 mmol) dis-
solved in DMF (30 mL). After stirring at 858C for 48 h, the heterogeneous
brown solution was evaporated to dryness and the residue taken up with a
mixture of diethyl ether and aqueous NaOH (10mass%). The organic layer
was washed twice with an aqueous solution of NaOH (10mass%), once
with dilute HCl (0.05 molL 1), and twice with water. It was then dried over
Na2SO4 and evaporated to dryness. The crude product was purified by flash
column chromatography (silica gel, CH2Cl2), to give pure 18 (20.33 g,
33.8 mmol, 95% yield) as a colorless oil. 1H NMR (CDCl3): d ˆ 7.18 (d, J ˆ
2.3 Hz, 2H), 6.68 (t, J ˆ 2.3 Hz, 1H), 4.62 (t, J ˆ 3.4 Hz, 2H), 4.13 (t, J ˆ
4.8 Hz, 4H), 3.88 (s, 3H), 4.00 ± 3.80 (m, 8H), 3.80 ± 3.40 (m, 16H), 1.95 ±
1.40 (m, 12H); anal. calcd for C30H48O12 (%): C 59.99, H 8.05; found: C
60.06, H 8.19.
Dialcohol 19: Pyridinium p-toluenesulfonate (418 mg, 1.66 mmol) dis-
solved in methanol (10 mL) was added to a solution of 18 (500 mg,
0.83 mmol) in refluxing methanol (100 mL). After 2 h stirring at reflux, the
solvent was removed and the residue taken up in CH2Cl2. The organic
solution was washed twice with water, dried over Na2SO4, and evaporated
to dryness. The crude product was purified by flash column chromatog-
raphy (silica gel; CH2Cl2 containing 1.0 ± 2.0% MeOH) to give pure 19
1
(317 mg, 0.73 mmol, 88% yield) as a colorless oil. H NMR (CDCl3): d ˆ
7.18 (d, J ˆ 2.3 Hz, 2H), 6.72 (t, J ˆ 2.3 Hz, 1H), 4.14 (t, J ˆ 4.7 Hz, 4H),
3.88 (s, 3H), 3.84 (t, J ˆ 4.7 Hz, 4H), 3.75 ± 3.65 (m, 12H), 3.59 (t, J ˆ
4.5 Hz, 4H); anal. calcd for C20H32O10 (%): C 55.55, H 7.46; found: C 55.60,
H 7.35.
Experimental Section
Dimesylate 20: To a solution of 19 (317 mg, 0.73 mmol) and triethylamine
(1.23 mL, 890 mg, 8.8 mmol) in CH2Cl2 (100 mL) at 08C was added mesyl
chloride (0.34 mL, 4.4 mmol) in CH2Cl2 (25 mL) over a period of 20 min.
After stirring for 2.5 h at 08C, the solution was washed twice with water,
dried over Na2SO4, and evaporated to dryness. The crude product was
purified by flash column chromatography (silica gel; CH2Cl2 containing
0.5 ± 1.0% MeOH), to give pure 20 (396 mg, 0.67 mmol, 92% yield) as a
pale yellow oil. 1H NMR (CDCl3): d ˆ 7.18 (d, J ˆ 2.3 Hz, 2H), 6.68 (t, J ˆ
2.3 Hz, 1H), 4.37 (t, J ˆ 4.5 Hz, 4H), 4.13 (t, J ˆ 4.6 Hz, 4H), 3.89 (s, 3H),
3.83 (t, J ˆ 4.6 Hz, 4H), 3.75 ± 3.70 (unresolved t, 4H), 3.70 ± 3.65 (m, 8H),
3.05 (s, 6H); anal. calcd for C22H36O14S2 (%): C 44.89, H 6.16; found: C
44.71, H 6.19.
Measurements: 1H NMR spectra were acquired on Bruker WP200 SY,
Bruker AM400, Varian Gemini 200, Bruker AC300, and Bruker AMX500
spectrometers. Melting points were determined on a Bioblock IA8103
apparatus and are uncorrected. GPC analyses in CHCl3 were performed
with PL-gel columns (Spectra Physics PSSSDV8, 600  103 Š, 5 mm pore
widths). GPC analyses were carried out on a Diol column (Merck 100/300/
1000 Š) connected to a UV/Vis detector. Calibration was based on
polystyrene standards with narrow molecular weight distributions. Field-
desorption mass spectrometric analyses were performed on a VG analytical
ZAB2-SE-FPD: (8 kV). Mass spectra were obtained either by chemical
ionization (CI-MS), by positive-ion fast atom bombardment (FAB-MS) or
by electrospray (ES-MS) mass spectrometry. MALDI-TOF measurements
were performed with a Bruker Reflex mass spectrometer, equipped with a
nitrogen laser delivering 3 ns laser pulses at l ˆ 337 nm (LSI N2 Laser, 106 ±
107 Wcm 1, 100 mm diameter spot). The instrument can be used in a linear
and a reflection mode. The reflection detector consists of a dual micro-
Diiodide compound 17: A solution of 20 (4.0 g, 6.8 mmol) and NaI (20.4 g,
136 mmol) in acetone (250 mL) was refluxed for 12 h. The solvent was
removed and the yellow oil taken up in CH2Cl2. The resulting solution was
washed twice with water, dried over Na2SO4, and evaporated to dryness.
Chem. Eur. J. 1999, 5, No. 6
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1849

J.-M. Kern, J.-P. Sauvage, Y. Geerts et al.
FULL PAPER
The crude product was purified by flash column chromatography (silica gel,
CH2Cl2) to give pure 17 (3.796 g, 5.82 mmol, 86% yield) as a pale yellow
oil. 1H NMR (CDCl3): d ˆ 7.19 (d, J ˆ 2.3 Hz, 2H), 6.70 (t, J ˆ 2.3 Hz, 1H),
4.15 (t, J ˆ 4.7 Hz, 4H), 3.89 (s, 3H), 3.85 ± 3.80 (unresolved t, 4H), 3.80 ±
3.70 (unresolved t, 4H), 3.70 ± 3.60 (m, 8H), 3.25 (t, J ˆ 6.9 Hz, 4H) ); anal.
calcd for C20H30O8I2 (%): C 36.83, H 4.64; found: C 37.17, H 4.74.
give the pure [2]catenate 13a (31 mg, 0.0134 mmol, 64% yield) as a dark
red solid. M.p. 92 ± 948C; 1H NMR (CDCl3, 400 MHz): d ˆ 8.07 (s, 4H;
H5,6), 7.63 (s, 4H; H3,8), 7.58 (d, J ˆ 8.3 Hz, 8H; Ho1), 6.94 (s, 16H;
H
o2,Hm2), 6.67 (d, J ˆ 8.3 Hz, 8H; Hm1), 6.63 (d, J ˆ 2.2 Hz, 4H; HB), 6.54 (t,
J ˆ 2.2 Hz, 2H; HA), 4.65 (s, 4H; HM), 4.27 ± 4.18 (m, 16H; Ha,Hf), 3.98 ±
3.90 (m, 16H; Hb,He), 3.79 (s, 16H; Hg,Hd), 3.03 (t, J ˆ 7.8 Hz, 8H; Ha),
1.70 ± 1.60 (m, 8H; Hb), 1.48 ± 1.37 (m, 8H; Hc), 1.37 ± 1.25 (m, 16H; Hd,He),
0.92 (t, J ˆ 6.8 Hz, 12H; Hf); 13C NMR (CDCl3): d ˆ 160.3, 158.9, 155.4,
150.7, 143.9, 143.5, 140.8, 137.5, 131.6, 128.7, 127.5, 126.9, 124.6, 123.3, 122.1,
115.0, 105.7, 100.7, 71.0, 70.0, 69.7, 67.7, 67.6, 65.3, 32.4, 31.6, 30.0, 29.3, 22.6,
Macrocycle 15: To an argon-flushed suspension of Cs2CO3 (1.00 g,
3.1 mmol) in DMF (135 mL) maintained at 608C was added dropwise a
mixture of 16 (582 mg, 0.85 mmol) and 17 (730.54 mg, 1.12 mmol) in DMF
(75 mL) over a period of 16 h with efficient stirring. The mixture was stirred
at this temperature for 5 h. DMF was removed under high vacuum and the
residue taken up in CH2Cl2. The CH2Cl2 layer was washed twice with water,
dried over Na2SO4, and evaporated to dryness to give a crude yellow
product (4.89 g). It was purified by flash column chromatography (silica
gel, CH2Cl2 containing 0 ± 1.0% MeOH) to give pure macrocycle 15
(487 mg, 0.449 mmol, 53% yield) as a pale yellow solid. M.p. 162 ± 1648C;
1H NMR (CDCl3): d ˆ 8.58 (d, J ˆ 8.4 Hz, 4H), 8.02 (s, 2H), 8.00 (s, 2H),
7.79 (d, J ˆ 8.4 Hz, 4H), 7.66 (d, J ˆ 8.7 Hz, 4H), 7.24 (d, J ˆ 2.5 Hz, 2H),
7.04 (d, J ˆ 8.7 Hz, 4H), 6.72 (t, J ˆ 2.3 Hz, 1H), 4.24 (t, J ˆ 4.9 Hz, 4H),
4.16 (t, J ˆ 4.7 Hz, 4H), 4.00 ± 3.85 (m, 8H), 3.87 (s, 3H), 3.78 (s, 8H), 3.20
(t, J ˆ 7.7 Hz, 4H), 2.00 ± 1.80 (m, 4H), 1.60 ± 1.25 (m, 12H), 0.91 (t, J ˆ
6.9 Hz, 6H); anal. calcd for C68H76N2O10 (%): C 75.53, H 7.08, N 2.59;
‡
14.1; FAB-MS: m/z: calcd for [13a] : 2170.2; found: 2168.9.
[2]Catenand 14b: KCN (110 mg, 1.7 mmol) dissolved in water (6 mL) was
added to 14a (500 mg, 0.21 mmol) in CH3CN (30 mL) and CH2Cl2 (15 mL).
The characteristic dark red color of the stirred solution disappeared
progressively whereas free ligand precipitated as a pink solid. After the
mixture had been stirred for 5 h at room temperature, addition of more
KCN (27 mg, 0.42 mmol) allowed completion of the demetalation. The
mixture was stirred for 2 h, the resulting pale yellow solution was
evaporated to dryness, and then taken up in CH2Cl2/H2O. The aqueous
layer was extracted with CH2Cl2 (3 Â 30 mL). The combined organic layers
were carefully washed with water (three times), dried over Na2SO4, and
evaporated to dryness. The crude yellow product was purified by flash
column chromatography (silica gel, CH2Cl2 containing 1.5 ± 2.5% MeOH)
to give pure free ligand 14b (309 mg, 0.143 mmol, 68% yield) as a yellow
‡
‡
found: C 75.40, H 7.13, N 2.37; FAB-MS: m/z: calcd for [15‡H ] : 1082.4;
found: 1081.4.
1
solid. M.p. 89 ± 918C; H NMR (CDCl3): d ˆ 8.55 (d, J ˆ 8.1 Hz, 8H), 8.00
Pre-rotaxane [Cu(15 ´ 16)] ´ PF6: A solution of [Cu(CH3CN)4PF6] (121 mg,
0.326 mmol) in degassed acetonitrile (20 mL) was added by cannula to a
stirred solution of 15 (320 mg, 0.296 mmol) in CH2Cl2 (20 mL) at room
temperature under argon. After stirring for 0.5 h at room temperature, a
solution of 16 (203 mg, 0.296 mmol) in degassed THF (20 mL) was added
and the solution turned dark red immediately. Subsequently, the solution
was stirred for 2 h under argon at room temperature. The solvents were
removed under reduced pressure to afford a dark red solid of crude
[Cu(15 ´ 16)]PF6 in nearly quantitative yield (584 mg, 0.296 mmol). This
compound was utilized without further purification. M.p. 121 ± 1238C;
1H NMR (CDCl3): d ˆ 8.06 (s, 2H), 7.91 (s, 2H), 7.60 ± 7.35 (m, 12H), 7.27
(d, J ˆ 2.3 Hz, 2H), 7.00 ± 6.80 (m, 16H), 6.82 (t, J ˆ 2.1 Hz, 1H), 6.61 (d,
J ˆ 8.2 Hz, 4H), 6.55 (d, J ˆ 8.2 Hz, 4H), 4.30 ± 4.15 (m, 8H), 4.00 ± 3.90 (m,
8H), 3.88 (s, 3H), 3.84 (s, 8H), 3.00 ± 2.80 (m, 8H), 1.65 ± 1.45 (m, 8H),
1.45 ± 1.20 (m, 24H), 0.90 (m, 12H).
(s, 4H), 7.97 (s, 4H), 7.73 (d, J ˆ 8.3 Hz, 8H), 7.56 (d, J ˆ 8.7 Hz, 8H), 7.15,
(d, J ˆ 2.2 Hz, 4H), 6.96 (d, J ˆ 8.7 Hz, 8H), 6.62, (t, J ˆ 2.2 Hz, 2H), 4.14
(t, J ˆ 4.9 Hz, 8H), 4.05 (t, J ˆ 4.4 Hz, 8H), 3.90 ± 3.75 (m, 22H), 3.70 (s,
16H), 3.16, t, J ˆ 7.6 Hz, 8H), 1.95 ± 1.70 (m, 8H), 1.55 ± 1.20 (m, 24H), 0.89
‡
(t, J ˆ 6.9 Hz, 12H); FAB-MS: m/z: calcd: 2163.7 [14b‡H] , 1082.4
‡
[15‡H] ; found: 2162.7, 1081.5.
[2]Catenand 13b: To a degassed solution of 14b (283 mg, 0.13 mmol) in
THF (125 mL) cooled to 108C was added a solution of diisobutylalumi-
num hydride in toluene (3.5 mL, 1.5 molL 1, 5.2 mmol). After 0.5 h stirring
at 108C, an additional portion of diisobutylaluminum hydride (1.5 mL,
2.2 mmol) was added to the red solution, which was then stirred for a
further 15 min. The solution was hydrolyzed with an aqueous solution of
HPF6 (pH ˆ 1 according to a pH paper test), THF was removed, and the
yellow residue taken up in CH2Cl2/(H2O ‡ HPF6). NaOH was added to the
aqueous layer to give pH ˆ 9 and then extracted with CH2Cl2 (2  30 mL).
The combined organic layers were washed with slightly basic water (pH ˆ
9) and twice with water, dried over Na2SO4, and evaporated to dryness. The
crude yellow product was purified by flash column chromatography (silica
gel, CH2Cl2 containing 1.5 ± 2.5% MeOH) to give pure [2]catenand 13b
(200 mg, 0.095 mmol, 73% yield) as a yellow solid. M.p. 95 ± 978C; 1H NMR
(CDCl3, 400 MHz): d ˆ 8.55 (d, J ˆ 8.6 Hz, 8H; Ho1), 8.01 (s, 4H; H5,6),
7.98 (s, 4H; H3,8), 7.72 (d, J ˆ 8.3 Hz, 8H; Hm1), 7.56 (d, J ˆ 8.8 Hz, 8H;
Copper(i) [2]catenate 14a:
A solution of [Cu(15 ´ 16)]PF6 (270 mg,
0.137 mmol), 17 (98 mg, 0.150 mmol), [Cu(CH3CN)4PF6] (51 mg,
0.137 mmol), l-(‡)-ascorbic acid (17 mg, 0.096 mmol), and Cs2CO3
(223 mg, 0.684 mmol) was stirred in DMF (100 mL) under argon at 508C
for 2 h. A further portion of 17 (98 mg, 0.150 mmol) was added and the
mixture heated for a further 16 h. DMF was removed under high vacuum
and the dark red residue taken up in CH2Cl2. The resulting solution was
treated for 2 h with a large excess of KPF6, dissolved in a minimum amount
of water. By means of this anion exchange reaction, it was possible to
isolate 14a, originally formed as carbonate, iodide, and hexafluorophos-
phate, as its PF6 salt exclusively. The resulting organic layer was washed
twice with water, dried over Na2SO4, and evaporated to dryness to yield
462 mg of a dark red solid. Flash column chromatography [i) silica gel,
CH2Cl2 containing 0.25 ± 0.75% MeOH; ii) aluminum oxide, CH2Cl2
containing 0.1 ± 0.5% MeOH] gave pure 14a (178 mg, 0.075 mmol, 55%
yield) as a dark red solid. M.p. 95 ± 978C; 1H NMR (CDCl3): d ˆ 8.06 (s,
4H), 7.63 (s, 4H), 7.58 (d, J ˆ 8.2 Hz, 8H), 7.27 (unresolved d, 4H), 6.94 (s,
16H), 6.81 (t, J ˆ 2.2 Hz, 2H), 6.67 (d, J ˆ 8.2 Hz, 8H), 4.30 ± 4.15 (m, 16H),
4.00 ± 3.85 (m, 16H), 3.88 (s, 6H), 3.84 (s, 16H), 3.02 (t, J ˆ 7.5 Hz, 8H),
1.70 ± 1.50 (m, 8H), 1.50 ± 1.20 (m, 24H), 0.91 (t, J ˆ 6.3 Hz, 12H); FAB-
H
o2), 6.96 (d, J ˆ 8.8 Hz, 8H; Hm2), 6.46 (d, J ˆ 2.1 Hz, 4H; HII), 6.30 (t, J ˆ
2.0 Hz, 2H; HI), 4.44 (s, 4H; HM), 4.14 (t, J ˆ 5.1 Hz, 8H; Ha), 3.99 (t, J ˆ
4.7 Hz, 8H; Hf), 3.82, (t, J ˆ 4.9 Hz, 8H; Hb), 3.77 (t, J ˆ 4.7 Hz, 8H; He),
3.69 (s, 16H; Hg,Hd), 3.18 (t, J ˆ 7.8 Hz, 8H; Ha), 1.84 (m, 8H; Hb), 1.55 ±
1.40 (m, 8H; Hc), 1.40 ± 1.25 (m, 16H; Hd,He), 0.90 (t, J ˆ 7.0 Hz, 12H; Hf);
13C NMR (CDCl3): d ˆ 160.0, 158.5, 155.8, 149.3, 146.8, 144.0, 141.5, 138.1,
133.4, 128.2, 128.0, 127.0, 126.5, 121.4, 119.6, 115.1, 105.4, 100.3, 70.9, 70.8,
69.9, 69.6, 67.5, 67.4, 64.7, 33.0, 31.7, 30.6, 29.4, 22.6, 14.1; FAB-MS: m/z:
‡
calcd for [13b‡H] : 2107.7; found: 2106.9.
Oligo[2]catenand 22b: A two-necked flask (10 mL) was charged, under
argon, with the diol 13b (119 mg, 56.5 mmol), the substituted terephthalic
acid 21 (37.3 mg, 56.5 mmol), the catalyst complex 4-N,N'-dimethylamino-
pyridine/p-toluene sulfonic acid 1:1 (33 mg, 113 mmol, 2 equiv), and dry
dichloromethane (1.3 mL). The reaction mixture was cooled to 108C and
diisopropylcarbodiimide (0.1 mL) was added. The mixture was stirred for
‡
‡
MS: m/z: calcd: 2226.3 [14a] , 1144.9 [15‡Cu] ; found: 2225.1, 1143.5.
Copper(i) [2]catenate 13a: A solution of diisobutylaluminum hydride in
toluene (0.4 mL, 1.5 molL 1, 0.6 mmol) was added to a degassed solution of
14a (50 mg, 0.021 mmol) in THF (25 mL) cooled to 108C. After 1 h
three days at
108C, two days at 08C, and then one day at room
stirring at
108C,
a
further portion of diisobutylaluminum hydride
temperature. The crude polymer was purified by precipitation in methanol
(0.2 mL, 1.5 molL 1, 0.3 mmol) was added. The mixture was stirred for
10 min and then a saturated solution of NaPF6 in water was added. THF
was removed and the yellow residue taken up in CH2Cl2, washed with a
saturated aqueous solution of NaPF6, washed twice with water, dried over
Na2SO4, and evaporated to dryness. The dark red crude product was
purified by column chromatography [i) silica gel, CH2Cl2 containing 1.0 ±
2.0% MeOH; ii) aluminum oxide, CH2Cl2 containing 1.0 ± 2.0% MeOH) to
to afford 120 mg as a yellow powder in 77% yield. The H and 13C NMR
1
spectra of the various batches were comparable, specifically: 1H NMR
(500 MHz, CDCl3, 308C): d ˆ 8.54 (s, 8H, arom.), 7.80 ± 7.30 (m, 26H,
arom.), 7.05 ± 6.85 (m, 10H, arom.), 6.72 (m, 4H, arom.), 6.54 (s, 4H,
arom.), 6.35 (m, 2H, arom.), 5.18 (m, 4H, aliph.), 4.40 ± 3.60 (m, 56H,
aliph.), 3.04 (m, 8H, aliph.), 2.06 (s, 8H, aliph.), 1.72 (s, 8H, aliph.), 1.44 (s,
8H, aliph.), 1.31 (s, 8H, aliph.), 1.26 (s, 8H, aliph.), 1.23 (s, 36H, aliph.), 0.88
1850
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Chem. Eur. J. 1999, 5, No. 6

Poly[2]catenanes
1841±1851
13
ˆ
(s, 12H, aliph.); C NMR (125.75 MHz, CDCl3, 308C): d ˆ 164.9 (C O);
160.1, 158.8, 158.1, 155.3, 152.3, 152.2, 141.8, 137.9, 128.1, 127.0, 126.9, 126.4,
121.6, 118.3, 115.3, 115.1, 109.0, 106.8, and 100.9 (arom.); 70.9, 69.9, 69.3,
67.6, 67.5, 66.8, 66.3, 34.9, 33.0, 32.9, 31.7, 30.4, 29.7, 29.4, 22.6, and 14.1
(aliph.)
1993, 17, 697 ± 701; c) D. Klempner, L. H. Sperling in Interpenetrating
Polymer Networks (Ed.: L. A. Utracki), Advances in Chemistry
Series 239, American Chemical Society, Washington DC, 1994.
[6] a) H. W. Gibson, H. Marand, Adv. Mater. 1993, 5, 11 ± 21; b) D. B.
Amabilino, I. W.Parsons, J. F. Stoddart, Trends Polym. Sci. 1994, 2,
146 ± 152.
[7] a) H. W. Gibson, M. C. Bheda, P. T. Engen, Prog. Polym. Sci. 1994, 19,
843 ± 945; b) J. A. Semlyen in Large ring molecules (Ed.: J. A.
Semlyen), Wiley, 1996.
[8] a) Y. Lipatov, Y.Nizel'sky, New. J. Chem. 1993, 17, 715 ± 722; b) T. D.
Shaffer, L. M. Tsay, J. Polym. Sci. Polym. Chem. 1991, 29, 1213 ± 1215.
[9] a) D. B. Amabilino, P. R. Ashton, A. S. Reder, N. Spencer, J. F.
Stoddart, Angew. Chem. 1994, 106, 1316 ± 1319; Angew. Chem. Int. Ed.
Engl. 1994, 33, 1286 ± 1290; b) See also F. Bitsch, C. O.Dietrich-
Buchecker, A. K. Khemis, J.-P. Sauvage, A. Van Dorsselaer, J. Am.
Chem. Soc. 1991, 113, 4023 ± 4025.
[10] a) D. Muscat, A. Witte, W. Köhler, K. Müllen, Y.Geerts, Macromol.
Rapid Commun. 1997, 18, 233 ± 241; b) Y. Geerts, D. Muscat, K.
Müllen, Macromol. Chem. Phys. 1995, 196, 3425 ± 3435.
[11] J.-L. Weidmann, J.-M. Kern, J.-P. Sauvage, Y. Geerts, D. Muscat, K.
Müllen, J. Chem. Soc. Chem. Commun. 1996, 1243 ± 1244.
[12] a) S. Menzer, A. J. P. White, D. J. Williams, M. Belohradsky, C.
Hamers, F. M. Raymo, A. N. Shipway, J. F. Stoddart, Macromolecules
1998, 31, 295 ± 307; b) S. Shimada, K. Ishikawa, N. Tamaoki, Acta
Chem. Scand. 1998, 52, 374 ± 376.
Poly[2]catenate 12a: A two-necked flask (10 mL) was charged, under
argon, with the diol 13a (214.6 mg, 92.7 mmol), the substituted terephthalic
acid 21 (61.4 mg, 92.7 mmol), the catalyst complex 4-N,N'-dimethylamino-
pyridine/p-toluene sulfonic acid 1:1 (60 mg, 204 mmol, 2.1 equiv) and dry
dichloromethane (2 mL). The reaction mixture was cooled to 208C and
diisopropylcarbodiimide (0.27 mL) was added. The mixture was stirred for
six days at 208C. The crude polymer was purified by precipitation in
methanol to afford 256 mg of a violet powder (94% yield). 1H NMR
(500 MHz, CDCl3, 308C): d ˆ 8.10 (s, 4H, arom.), 7.75 ± 7.40 (m, 12H,
arom.), 7.00 (s, 2H, arom.), 6.90 (s, 16H, arom.), 6.75 (s, 4H, arom.), 6.63 (s,
12H, arom.), 6.53 (s, 2H, arom.), 5.26 (s, 4H, aliph.), 4.63 (benzyl alcohol
end-groups), 4.37 (m, 4H, aliph.), 4.30 (m, 4H, aliph.), 4.17 (s, 8H, aliph.),
4.15 (s, 8H, aliph.), 3.87 (s, 8H, aliph.), 3.77 (s, 8H, aliph.), 3.00 (s, 8H,
aliph.), 1.63 (s, 16H, aliph.), 1.40 (s, 8H, aliph.), 1.28 (s, 44H, aliph.), 0.88 (t,
13
ˆ
12H, aliph.); C NMR ( 125.75 MHz, CDCl3, 308C): d ˆ 163.6 (C O);
158.9, 157.6, 156.8, 151.0, 150.9, 136.6, 126.2, 124.0, 123.0, 117.1, 114.0, 113.5,
107.7, 105.5, 99.8, and 99.1 (arom.); 69.5, 68.6, 68.3, 68.1, 66.2, 65.4, 65.0,
33.6, 31.1, 30.1, 28.6, 27.9, 21.2, and 12.7 (aliph.).
Poly[2]catenand 12b: To a solution of poly[2]catenate 12a (200 mg) in
THF (30 mL) was added KCN (500 mg). The reaction mixture was stirred
for one day at room temperature until the characteristic violet color of
poly[2]catenate had disappeared. Precipitation in methanol afforded
150 mg of 12b as a yellow powder (81% yield). 1H NMR (500 MHz,
CDCl3, 308C): d ˆ 8.51 (s, 4H, arom.), 8.00 ± 7.89 (m, 8H, arom.), 7.75 ± 7.35
(m, 18H, arom.), 6.96 (s, 2H, arom.), 6.91 (d, 8H, arom.), 6.70 (s, 4H,
arom.), 6.52 (s, 4H, arom.), 6.33 (s, 2H, arom.), 5.16 (s, 4H, aliph.), 4.38 (s,
end groups, 4%), 4.37 ± 4.22 (m, 8H, aliph.), 4.10 (s, 8H, aliph.), 3.96 (s, 8H,
aliph.), 3.77 ± 3.64 (m, 32H, aliph.), 3.10 (s, 8H, aliph.), 1.77 (s, 8H, aliph.),
[13] a) C. O. Dietrich-Buchecker, J.-P. Sauvage, J.-P. Kintzinger, Tetrahe-
dron Lett. 1983, 24, 5095 ± 5098; b) C. O. Dietrich-Buchecker, J.-P.
Sauvage, J.-M. Kern, J. Am. Chem. Soc. 1984, 106, 3043 ± 3045; c) C. O.
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Ceroni, V. Balzani, Inorg. Chem. 1997, 36, 5329 ± 5338.
[16] J. S.Moore, S. I. Stupp, Macromolecules 1990, 23, 65 ± 70.
[17] a) G.Klärner, C. Former, X. Yan, R. Richert, R. K. Müllen, Adv.
Mater. 1996, 8, 932 ± 935; b) G. Klärner, C. Former, K. Martin, J.
Räder, K. Müllen, Macromolecules 1998, 31, 3571 ± 3577.
[18] M. Asakawa, C. L.Brown, S. Menzer, F. M. Raymo, J. F. Stoddart, D. J.
Williams, J. Am. Chem. Soc. 1997, 119, 2614 ± 2627.
[19] a) J. B. Williams, A. I. Gusev, D. M. Hercules, Macromolecules 1997,
30, 3781 ± 3787; b) Y. L.Kim, D. M.Hercules, Macromolecules 1994, 27,
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3296.
[20] C. O. Dietrich-Buchecker, P. A. Marnot, J.-P. Sauvage, J. R. Kirchoff,
D. R.McMillin, J. Chem. Soc. Chem. Commun. 1983, 513 ± 515.
[21] H. Benoit, P. Rempp, Z. Grubisic, J. Polym. Sci. 1967, B5, 753 ± 759.
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Materials, 2nd ed., A.&P. Blackie, London, 1977; b) P. A. Lovell,
Dilute Solution Viscometry in Comprehensive Polymer Science, (Eds.:
G. Allen, J. C. Bevington), Pergamon, Oxford, 1989, pp. 173 ± 197, and
references therein.
1.43 (s, 8H, aliph.), 1.31 (s, 8H, aliph.), 1.24 (m, 44H, aliph.), 0.86 (t, 12H,
13
ˆ
aliph.); C NMR (125.75 MHz, CDCl3, 308C): d ˆ 165.0 (C O); 162.5,
160.1, 158.5, 158.1, 155.4, 152.3, 152.2, 149.2, 146.8, 141.5, 137.9, 133.3, 128.1,
128.0, 126.8, 124.4, 125.3, 121.4, 119.3, 118.3, 115.3, 115.1, 109.1, 106.7, and
100.8 (arom.); 70.8, 69.8, 69.6, 69.3, 67.5, 67.4, 66.8, 66.3, 36.4, 34.9, 32.9, 31.7,
31.4, 30.5, 29.7, 29.4, 22.6, and 14.1 (aliph.).
Acknowledgments
Prof. K. Müllen and Dr. S. Shimada are gratefully acknowledged for fruitful
discussions. The authors would like to thank B. Müller and J. Spickermann
for their technical assistance in the characterization of the polymers. We
thank the CNRS and the European Communities for financial support. We
are also grateful to the French Ministry of Education for a fellowship to
JLW.
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Received: October 1, 1998
Revised version: January 27, 1999 [F 1376]
Chem. Eur. J. 1999, 5, No. 6
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0947-6539/99/0506-1851 $ 17.50+.50/0
1851