Cyclic [2]pseudorotaxane tetramers consisting of two rigid rods threaded through two bis-macrocycles: Copper(I)-templated synthesis and X-ray structure studies

Article abstract of DOI:10.1021/ja801924y

Variously substituted coordinating rigid rods have been synthesized which incorporate a central 4,7-phenanthroline nucleus attached to two 2-pyridyl groups via its 3 and 8 positions, so as to yield bisbidentate chelates, the two-coordinating axes of the chelates being parallel to one another. Regardless of the nature of the substituents borne by the rods, the copper(I)-induced threading reaction of two such rods through the rings of two bis-macrocycles affords in a quantitative yield the 4-copper(I) threaded assembly. The [2]pseudorotaxane tetramers thus obtained have been fully characterized in solution and, for one of them, an X-ray structure could be obtained, confirming the threaded nature of the complex and providing important structural information.

Full text of DOI:10.1021/ja801924y

Published on Web 07/25/2008
Cyclic [2]Pseudorotaxane Tetramers Consisting of Two Rigid
Rods Threaded through Two Bis-Macrocycles:
Copper(I)-Templated Synthesis and X-ray Structure Studies
Julien Frey,† Christian Tock,† Jean-Paul Collin,*,† Vale´rie Heitz,*,†
Jean-Pierre Sauvage,*,† and Kari Rissanen‡
Laboratoire de Chimie Ogano-Mine´rale, LC3 UMR 7177 du CNRS, UniVersite´ Louis Pasteur,
Institut de Chimie, 4 rue Blaise Pascal, 67070 Strasbourg Cedex, France, and Nanoscience
Center, Department of Chemistry, UniVersity of JyVa¨skyla¨, P.O. Box 35,
40014 UniVersity of JyVa¨skyla¨, Finland
Received March 14, 2008; E-mail: jpcollin@chimie.u-strasbg.fr; heitz@chimie.u-strasbg.fr; sauvage@chimie.u-strasbg.fr
Abstract: Variously substituted coordinating rigid rods have been synthesized which incorporate a central
4,7-phenanthroline nucleus attached to two 2-pyridyl groups via its 3 and 8 positions, so as to yield bis-
bidentate chelates, the two-coordinating axes of the chelates being parallel to one another. Regardless of
the nature of the substituents borne by the rods, the copper(I)-induced threading reaction of two such rods
through the rings of two bis-macrocycles affords in a quantitative yield the 4-copper(I) threaded assembly.
The [2]pseudorotaxane tetramers thus obtained have been fully characterized in solution and, for one of
them, an X-ray structure could be obtained, confirming the threaded nature of the complex and providing
important structural information.
Introduction
noteworthy are the muscle-like compounds reported by two
groups,4,5 a molecular elevator,6 illustrating the complexity that
The field of catenanes and rotaxanes1 is particularly active,
mostly in relation to the novel properties that these compounds
may exhibit (electron transfer, controlled motions, mechanical
properties, etc...). A particularly promising area is that of
synthetic molecular machines and motors.2 In recent years,
several spectacular examples of molecular machines leading to
real devices have been proposed, based either on interlocking
systems or on non interlocking molecules.3 In parallel, more
and more sophisticated molecular machines have been reported,
frequently based on multicomponent rotaxanes. Particularly
dynamic threaded systems can reach, and light-driven linear
motors containing an organic chromophore7 or a ruthenium(II)
complex acting as light-harvesting species.8 Complex interlock-
ing topologies are thus needed if one wants to increase the
functionality of future molecular machines. The quest for new
molecular topologies is also a challenge in itself, to demonstrate
the power of modern synthetic strategies, based most of the
time on organic or inorganic templates.
The synthesis of multirotaxanes incorporating several rings
and several thread-like fragments is still far from being trivial.9
The copper(I) templated strategy proposed long ago has been
† Laboratoire de Chimie Ogano-Mine´rale.
‡ Nanoscience Center, Department of Chemistry, University of Jyva¨skyla¨.
(1) For early work, see: (a) Schill, G., Catenanes, Rotaxanes and Knots;
Organic Chemistry: Academic Press: New York, 1971; Vol 22;(b)
Dietrich-Buchecker, C. O.; Sauvage, J.-P. Chem. ReV. 1987, 87, 795–
810. (c) Amabilino, D. B.; Stoddart, J. F. Chem. ReV. 1995, 95, 2725–
2828. (d) Johnston, A. G.; Leigh, D. A.; Pritchard, R. J.; Deegan,
M. D. Angew. Chem., Int. Ed. 1995, 34, 1209–1212. (e) Vo¨gtle, F.;
Du¨nnwald, T.; Schmidt, T. Acc. Chem. Res. 1996, 29, 451–460. (f)
Molecular Catenanes, Rotaxanes and Knots: A Journey through the
World of Molecular Topology; Sauvage, J.-P., Dietrich-Buchecker, C.,
Eds; Wiley: Chichester, U.K., 1999. (g) Fujita, M. Acc. Chem. Res.
1999, 32, 53–61. (h) Hoshino, T.; Miyauchi, M.; Kawaguchi, Y.;
Yamaguchi, H.; Harada, A. J. Am. Chem. Soc. 2000, 122, 9876–9877.
(i) Bogdan, A.; Vysotsky, M. O.; Ikai, T.; Okamoto, Y.; Bo¨hmer, V.
Chem. Eur. J. 2004, 10, 3324–3330. (j) Beer, P. D.; Sambrook, M. R.;
Curiel, D. Chem. Commun. 2006, 2105–2117.
(3) (a) Livoreil, A.; Sauvage, J.-P.; Armaroli, N.; Balzani, V.; Flamigni,
L.; Ventura, B. J. Am. Chem. Soc. 1997, 119, 12114–12124. (b)
Koumura, N.; Zijistra, R. W. J.; van Delden, R. A.; Harada, N.;
Feringa, B. L. Nature 1999, 401, 152–155. (c) Collier, C. P.;
Mattersteig, G.; Wong, E. W.; Luo, Y.; Beverly, K.; Sampaio, J.;
Raymo, F. M.; Stoddart, J. F.; Heath, J. R. Science 2000, 289, 1172–
1175. (d) Leigh, D. A.; Wong, J. K. Y.; Dehez, F.; Zerbetto, F. Nature
2003, 424, 174–179. (e) Korybut-Daszkiewicz, B.; Wiec¸kowska, A.;
Bilewicz, R.; Domagata, S.; Wozniak, K. Angew. Chem., Int. Ed. 2004,
43, 1668–1672. (f) Fabbrizzi, L.; Foti, F.; Patroni, S.; Pallavicini, P.;
Taglietti, A. Angew. Chem., Int. Ed. 2004, 43, 5073–5077.
(4) (a) Jime´nez, M. C.; Dietrich-Buchecker, C.; Sauvage, J.-P. Angew.
Chem., Int. Ed. 2000, 39, 3284–3287. (b) Jime´nez-Molero, M. C.;
Dietrich-Buchecker, C.; Sauvage, J.-P. Chem. Eur. J. 2003, 8, 1456–
1466.
(5) (a) Huang, T. J.; Brough, B.; Ho, C.-M.; Liu, Y.; Flood, A. H.;
Bonvallet, P. A.; Tseng, H.-R.; Stoddart, J. F.; Baller, M. Appl. Phys.
Lett. 2004, 85, 5391–5393. (b) Liu, Y.; Flood, A. H.; Bonvallet, P. A.;
Vignon, S. A.; Northrop, B. H.; Jeppesen, J. O.; Huang, T. J.; Brough,
B.; Baller, M.; Magonov, S. N.; Solares, S. D.; Goddard, W. A.; Ho,
C.-M.; Stoddart, J. F. J. Am. Chem. Soc. 2005, 127, 9745–9759.
(6) (a) Badjic, J. D.; Balzani, V.; Credi, A.; Serena, S.; Stoddart, J. F.
Science 2004, 303, 1845–1849. (b) Badjic, J. D.; Ronconi, C. M.;
Stoddart, J. F.; Balzani, V.; Serena, S.; Credi, A. J. Am. Chem. Soc.
2006, 128, 1489–1499.
(2) (a) Acc. Chem. Res., 2001, 34, 409-522, (Special Issue on Molecular
Machines), and references therein. (b) Molecular Machines and
Motors, Structure and Bonding; Sauvage, J.-P., Ed.; Springer: Berlin,
Germany, 2001. (c) Balzani, V.; Venturi, M.; Credi, A. Molecular
DeVices and Machines: A Journey into the Nanoworld; Wiley-VCH:
Weinheim, Germany, 2003. (d) Kay, E. R.; Leigh, D. A.; Zerbetto, F.
Angew. Chem., Int. Ed. 2007, 46, 72–191. (e) Bonnet, S.; Collin, J.-
P.; Koizumi, M.; Mobian, P.; Sauvage, J.-P. AdV. Mater. 2006, 18,
1239–1350.
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2008 American Chemical Society
J. AM. CHEM. SOC. 2008, 130, 11013–11022 11013

A R T I C L E S
Frey et al.
Scheme 1. Principle of the Transition Metal-Directed Threading
second part, we will discuss the copper(I) based threading
reactions and illustrate the prototypical example by an X-ray
structure. This structure will not only prove in a definitive
manner the topology of the 4-copper complex but it will at the
same time show that the very large molecule obtained can
accommodate a certain degree of distortion. The third part will
be devoted to the attempts to prepare a [3]catenane from an
appropriately substituted threaded complex; as will be discussed,
the compound could not be isolated pure but its formation could
unambiguously be demonstrated by High Resolution Electro
Spray Mass Spectrometry (HR ES-MS).
Process Leading To a Cyclic [2]Pseudo-rotaxane Tetramera
a The black dot represents the metal center (copper(I) in the present work)
and the U-shaped sign symbolizes a bidentate chelate (a diimine ligand of
the 1,10-phenanthroline family).
Results and Discussion
extended to more and more complex molecules, incorporating
several metal centers.10 As far as Cu(I)-complexed rotaxanes
are concerned, various compounds are worth noting which
contain several metal centers: a [5]rotaxane with porphyrinic
stoppers11 and a cyclic rotaxane tetramer whose organic
components consist of a coordinating “filament” appended to a
ring12 are particularly representative. Recently, our group has
reported an unusual topology consisting of a large ring threading
the two halves of a bis-macrocycle (“handcuff”).13 Incidentally,
such a topology had already been reported by Becher et al.
containing totally different components.14
The bis-macrocycle used for the synthesis of a “handcuff”
catenane can be utilized for constructing other complex systems
such as, in particular, a rotaxane tetramer (stoppered or
nonstoppered analogue), as depicted in Scheme 1.
The success of the strategy represented in Scheme 1 relies to
a large extent on the design and synthesis of the appropriate
constituents, the rod and the bis-macrocycle. In the present
report, we will first describe the synthesis of the various rods
used for the formation of the pseudorotaxane structures. In a
The various organic fragments leading to the formation of
the threaded species described in the present report are depicted
in Figure 1.
The two key components are the bis-macrocycle 1, whose
synthesis has been described not long ago,15 and a two-chelating
unit thread (2 or 3). 1 contains two back-to-back rigidly
connected dpp-type chelates (dpp: 2,9-diphenyl-1,10-phenan-
throline) incorporated in 30 membered-rings. The rigidity of
the system is such that folding of the central aromatic part of
the compound is expected to be very limited, thus allowing good
control over the geometry of complexes formed by threading
various fragments through the ring and, in particular, over the
distance between two hypothetical metal centers coordinated
in the diimine sites. Compounds 2 and 3 incorporate side-to-
side bidentate chelating units, the central 4,7-phenanthroline
nucleus being such that, like for 1, the distance between the
coordination sites is well-controlled. A recent X-ray structure
of a di-iridium complex consisting of two iridium(III) centers
coordinated to the diimine coordination sites of a ligand similar
to 2 or 3 and ancillary ligands shows that the Ir-Ir distance is
8.17 Å,16 whereas molecular models tend to indicate that the
ideal distance, in a non-distorted ligand, should be around 8.5
Å. The 3,8-di(2′-pyridyl)-4,7-phenanthroline motif (dpyp) has
already been used in a few studies, in relation to copper(I)-
complexed molecular grids or pseudorotaxanes.17 The use of
unsubstituted ligands of the dpyp family such as 2 can be
problematic in the course of synthetic work aiming at affording
functionalized compounds. In fact, 2 and some of its precursors
are highly insoluble, which prevents their use in further reactions
except in simple coordination chemistry reactions. This is the
reason why solubilizing groups have been introduced in 3 and
its precursors, making the handling and the chemical modifica-
tion of these molecules much easier than for 2. Compound 3 is
end-functionalized by two long fragments bearing allyl groups.
These terminal olefins will be used after the threaded species
has been made for preparing a cyclic structure by ring-closing
metathesis (RCM), as discussed in the last section of the present
report.
(7) (a) Murakami, H.; Kawabuchi, A.; Kotoo, K.; Kunitake, M.; Na-
kashima, N. J. Am. Chem. Soc. 1997, 119, 7605–7606. (b) Brouwer,
A. M.; Frochot, C.; Gatti, F. G.; Leigh, D. A.; Mottier, L.; Paolucci,
F.; Roffia, S.; Wurpel, G. W. H. Science 2001, 291, 2124–2128. (c)
Stanier, C. A.; Alderman, S. J.; Claridge, T. D. W.; Anderson, H. L.
Angew. Chem., Int. Ed. 2002, 41, 1769–1772. (d) Pe´rez, E. M.; Dryden,
D. T. F.; Leigh, D. A.; Teobaldi, G.; Zerbetto, F. J. Am. Chem. Soc.
2004, 126, 12210–12211. (e) Wang, Q.-C.; Qu, D.-H.; Ren, J.; Chen,
K.; Tian, H. Angew. Chem., Int. Ed. 2004, 43, 2661–2665.
(8) (a) Schofield, E. R.; Collin, J.-P.; Gruber, N.; Sauvage, J.-P. Chem.
Commun. 2003, 188–189. (b) Pomeranc, D.; Jouvenot, D.; Chambron,
J.-C.; Collin, J.-P.; Heitz, V.; Sauvage, J.-P. Chem. Eur. J. 2003, 9,
4247–4254. (c) Mobian, P.; Kern, J.-M.; Sauvage, J.-P. Angew. Chem.,
Int. Ed. 2004, 43, 2392–2395. (d) Bonnet, S.; Collin, J.-P.; Sauvage,
J.-P. Inorg. Chem. 2006, 45, 4024–4034. (f) Balzani, V.; Clemente-
Leon, M.; Credi, A.; Ferrer, B.; Venturi, M.; Flood, A. H.; Stoddart,
J. F. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 1178–1183.
(9) (a) Ashton, P. R.; Reder, A. S.; Spencer, N.; Stoddart, J. F. J. Am.
Chem. Soc. 1993, 115, 5286–5287. (b) Gibson, H. W.; Bheda, M. C.;
Engen, P. T. Prog. Polym. Sci. 1994, 19, 843–945. (c) Belaissaoui,
A.; Shimada, S.; Ohishi, A.; Tamaoki, N. Tetrahedron Lett. 2003, 44,
2307–2310. (d) Wenz, G.; Han, B.-H.; Mu¨ller, A. Chem. ReV. 2006,
106, 782–817.
1. Synthesis of the Dpyp-Type Rods. To allow further
functionalization of the dpyp ligand, compound 7, bearing two
bromine atoms at the right positions was synthesized by
modification of a literature procedure developed for a slightly
(10) (a) Dietrich-Buchecker, C. O.; Sauvage, J.-P. Chem. ReV. 1987, 87,
795–810. (b) Chambron, J.-C.; Dietrich-Buchecker, C. O.; Sauvage,
J.-P. ComprehensiVe Supramolecular Chemistry: Templating, Self-
Assembly, and Self-Organization; Atwood, J. L., Davies, J. E. D.,
MacNicol, D. D., Vo¨gtle, F., Lehn, J.-M., Sauvage, J.-P., Hosseini,
M. W.,Eds.;, 1996, Vol. 9, 43-83.
(11) (a) Solladie´, N.; Chambron, J.-C.; Dietrich-Buchecker, C. O.; Sauvage,
J.-P. Angew. Chem., Int. Ed. 1996, 35, 906–909. (b) Solladie´, N.;
Chambron, J.-C.; Sauvage, J.-P. J. Am. Chem. Soc. 1999, 121, 3684–
3692.
(15) Frey, J.; Kraus, T.; Heitz, V.; Sauvage, J.-P. Chem. Eur. J. 2007, 13,
7584–7594.
(16) Auffrant, A.; Barbieri, A.; Barigelletti, F.; Lacour, J.; Mobian, P.;
Collin, J.-P.; Sauvage, J.-P.; Ventura, B. Inorg. Chem. 2007, 46, 6911–
6919.
(12) Kraus, T.; Budes´ınsky, M.; Cvacka, J.; Sauvage, J.-P. Angew. Chem.,
Int. Ed. 2006, 45, 258–261.
(17) (a) Sleiman, H.; Baxter, P. N. W.; Lehn, J.-M.; Airola, K.; Rissanen,
K. Inorg. Chem. 1997, 36, 4734–4742. (b) Baxter, P. N. W.; Khoury,
R. G.; Lehn, J.-M.; Baum, G.; Fenske, D. Chem. Eur. J. 2000, 6, 4140–
4148.
(13) Frey, J.; Kraus, T.; Heitz, V.; Sauvage, J.-P. Chem. Commun. 2005,
5310–5312.
(14) Li, Z.-T.; Becher, J. Chem. Commun. 1996, 5, 639–640.
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Cyclic [2]Pseudorotaxane Tetramers
A R T I C L E S
Figure 1. Chemical structures of the bis-ring 1, the short rod 2, and the elongated rod 3.
Scheme 2. Stille Coupling between 4 and 6 to Afford The Bis-bidentate Ligand 7 and Preparation of the
5-Bromo-2-trimethylstannylpyridine (6)
different compound.17 As shown in Scheme 2, the Stille coupling
between 3,8-dibromo-4,7-phenanthroline, 4, and the trimethyl
stannyl derivative 6, prepared from 5 under classical condi-
tions,18 furnished the desired molecule 7 in good yield.
During the Stille coupling reaction between 4 and 6,19
oxidative addition to the palladium catalyst is possible on two
different bromo-aryl sites. The 85% yield for compound 7 shows
that it is much more likely to happen on the 1,10-phenanthroline
nucleus than on the pyridine moiety. This can be explained by
the electrophilic nature of the carbon ortho to the nitrogen atom
in 4. Hence, homocoupling between two pyridine heterocycles
is not observed. Compound 7 is highly insoluble and could only
be purified by extracting it, after sonication, from diatomaceous
earth with boiling chloroform.
Scheme 3. Synthesis of the Functionalized Threads 8 and 2 by
Suzuki Coupling
In subsequent reactions, the axle was elongated by Suzuki
coupling20 with 4-(trimethylsilyl)phenylboronic acid and 4-meth-
oxyphenylboronic acid, which are both commercially available
(Scheme 3). These boronic acids were chosen because they
permit further functionalization. The trimethylsilyl group (TMS)
can easily be substituted by an iodide, thus allowing further
coupling reactions, whereas deprotection of the methoxyphenyl
results in a phenol, able to undergo Williamson reactions.
Compounds 8 and 2, obtained in 66% and 82% yield
respectively, are the first important fragments toward the
construction of a longer thread, but they are also interesting by
themselves, as they can be used to drive the formation of several
(18) (a) Wang, X.; Rabbat, P.; O’Shea, P.; Tillyer, R.; Grabowski, E. J. J.;
Reider, P. J. Tetrahedron Lett. 2000, 41, 4335–4338. (b) Colasson,
B. X.; Dietrich-Buchecker, C.; Sauvage, J.-P. Synlett 2002, 2, 271–
272.
(19) (a) Stanforth, S. P. Tetrahedron 1998, 54, 263–303. (b) Nicolaou,
K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem., Int. Ed. 2005, 44,
4442–4489.
(20) (a) Miyaura, N.; Yanagi, T.; Suzuki, A. Synth. Commun. 1981, 11,
513–519. (b) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457–
2483.
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A R T I C L E S
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Scheme 4. Synthesis of 2,5-Diethyl-4-trimethylsillyl-phenylboronic
Acid 12
Scheme 5. Synthesis of the Rod 13, Containing Ethyl Solubilizing
Groups and of Compound 14, Functionalized by Two Iodide
Groupsa
copper-complexed multicomponent systems. It is worth noticing
that compound 2 is even less soluble than compound 7, due to
additional anisyl groups, elongating the delocalized system. To
a A numbering of the various carbon atoms is also indicated.
1
be able to carry out useful H NMR spectroscopy in CDCl3,
we were forced to add a small amount of TFA (trifluoroacetic
acid), thus protonating the diimines, and making the compound
slightly more soluble. Compound 8 benefits from the presence
of TMS groups as solubilizing agents and is slightly easier to
handle than 7 and 2. Nevertheless, the poor solubility of
compounds 7, 8, and 2 prompted us to attach solubilizing groups
on the dpyp-type compounds. Since, in a later stage, the rods
derived from 7, 8, and 2 were expected to be threaded through
the 30-membered rings of 1, it was essential to avoid bulky
groups as solubilizing functions. If too large, then such groups
could inhibit threading of the rod through the ring. The use of
ethyl groups seemed to be a good compromise between size
and solubilizing effect. The precursors to compound 3 were
prepared following the sequence of reactions represented in
Schemes 4, 5, and 6.
Scheme 6. Synthesis of the Diphenol 17
Diethyl-phenyl boronic acid 12 was prepared similarly to
comparable molecules of the literature21 starting from the
commercially available 1,4-diethylbenzene, as shown in
Scheme 4.
After dibromination of compound 9 to give 2,5-diethyl-1,4-
dibromobenzene 10, a first bromine atom was replaced by a
TMS group upon reaction with n-BuLi and TMSCl to yield
compound 11. Finally, the required boronic acid is obtained by
reacting 11 with first n-BuLi, then B(OiPr)3 and, subsequent,
hydrolysis. The TMS group is added so as to be converted later
on to an iodide and hence allow further coupling reactions.
Suzuki coupling between 12 and 7, as indicated in Scheme 5,
generates ligand 13.
This new compound is now readily soluble in classical
solvents, such as dichloromethane or chloroform. The short ethyl
groups are thus very effective solubilizing agents. The bis-TMS
compound 13 was quantitatively converted to the diiodide 14
using ICl in dichloromethane, which is also soluble in most
common solvents.
groups at the ends of 14. The chemical steps leading first to
16, an elongated version of 14, then to the corresponding
diphenol (compound 17) and subsequently to compound 3, are
represented in Schemes 6 and 7.
The THP-protected boronic acid 1522 was connected to
the iodo-rod 14, to give the elongated thread 16. A satisfying
yield of 75% for a double-Suzuki coupling reaction is an
indication that the steric hindrance imposed by the ethyl
groups close to the iodine atoms does not interfere with the
Suzuki coupling reaction. After deprotection of the OTHP
groups, the diphenol axis 17 was obtained in a nearly
quantitative yield. The rod now contains eight aromatic cycles
in line. Despite this structural feature and the presence of
the phenol moieties at each end of molecule 17, it can be
In order to functionalize the rod, Williamson reaction seemed
to be convenient. It was thus necessary to introduce two phenolic
1
readily manipulated and analyzed by H NMR. As already
noted, the four ethyl groups are really powerful solubilizing
(21) (a) Rehahn, M.; Schlueter, A. D.; Feast, W. J. Synthesis 1988, 386–
388. (b) Hensel, V.; Schlu¨ter, D. A. Liebigs Ann. Recueil 1997, 303–
309.
(22) Shen, D.; Diele, S.; Pelzl, G.; Wirth, I.; Tschierske, C. J. Mater. Chem.
1999, 9, 661–672.
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Cyclic [2]Pseudorotaxane Tetramers
A R T I C L E S
Scheme 7. Synthesis of the Diolefinic Thread 3 by Williamson Reaction
Scheme 8. Copper(I)-Directed Threading Reaction Leading to the 4-Copper [2]Pseudo-rotaxane Tetramer 194+a
a Due to the poor solubility of the organic fragments and to the many complexes which can potentially be formed, formation of the most stable species,
namely the threaded complex 194+, requires a long period of time at room temperature (several days).
agents. The synthesis of 3 was then carried out using the
triethylene glycol derivative 1823 and the diphenol 17.
2. Formation of a [2]Pseudorotaxane Tetramer from the Bis-
macrocycle 1 and the Rod 2: The Gathering and Threading
Effect of Copper(I). In recent years, transition metals have been
much utilized in association with various types of ligands to
generate complex architectures. Ideally, the complexation reac-
tion should be performed under thermodynamic control. Under
such conditions, the system will self-repair if unfavorable
reaction pathways are taken and will finally give rise to the
most stable situation. One of the main requirements to reach
the thermodynamic equilibrium is certainly that the coordination
and decoordination reactions must be sufficiently fast for the
system to find its stable position. In spectacular studies reported
by Fujita and co-workers,24 the assembling metal is palladium(II)
which is indeed able to undergo fast ligand substitution reactions
and is thus well adapted to the formation of complexes under
thermodynamic control. Many other groups have based their
studies on related principles and could demonstrate that highly
complex and multicomponent species can be obtained in high
yield by simply mixing appropriate multisite ligands and metals
and then waiting for the equilibrium to be reached.25 Along
these lines, our group has used copper(I) extensively to generate
a variety of threaded species.26 In a preliminary communication,
we recently described the copper(I)-driven threading reaction
of 1 by rod 2.27 The reaction is depicted in Scheme 8. The
[2]pseudorotaxane tetramer 194+ is obtained quantitatively after
(25) (a) Constable, E. C. Tetrahedron 1992, 48, 10013–10059. (b) Caulder,
D. L.; Raymond, K. N. Acc. Chem. Res. 1999, 32, 975–982. (c)
Leininger, S.; Olenyuk, B.; Stang, P. J. Chem. ReV. 2000, 100, 853–
907. (d) Molecular Self-Assembly Organic Versus Inorganic Ap-
proaches, Structure and Bonding; Saalfrank, R. W., Uller, E.,
Demleitner, B., Bernt, I., Eds.; Springer: Berlin, Germany, 2000, 96,
149-175. (e) Bunzli, J. C.; Piguet, C. Chem. ReV. 2002, 102, 1897–
1928. (f) Lehn, J.-M. Science 2002, 295, 2400–2403.
(26) Collin, J.-P.; Dietrich-Buchecker, C.; Hamann, C.; Jouvenot, D.; Kern,
J.-M.; Mobian, P.; Sauvage, J.-P. ComprehensiVe Coordination
Chemistry II. From the Molecular to the Nanoscale, Synthesis and
Structure ; Fujita, M., Powell, A., Eds.; Elsevier: New York, 2003, 7,
303-355.
(23) Arico, F.; Mobian, P.; Kern, J.-M.; Sauvage, J.-P. Org. Lett. 2003, 5,
1887–1890.
(24) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem. Res.
2005, 38, 371–380.
(27) Collin, J.-P.; Frey, J.; Heitz, V.; Sakellariou, E.; Sauvage, J.-P.; Tock,
C. New J. Chem. 2006, 30, 1386–1389.
9
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A R T I C L E S
Frey et al.
Figure 3. Space-filling zoom of one of the Cu(I) complex units of 194+
.
structure of Figure 2). The flattening of the copper complexes
is not new. It has been observed in many similar copper(I)
complexes including catenanes.28 In the present case, the
flattened situation is well-illustrated on the zoom view of the
structure represented in Figure 3. For each macrocycle, one of
the two phenyl rings undergoes π-π interaction with an external
pyridyl heterocycle of the bis-diimine ligand of the thread (blue
arrow). The distance between the centroids of these two cycles
is 3.865 Å, i.e., close to the expected distance between stacking
aromatic nuclei. The second phenyl ring of each macrocycle
moves closer to the central 4,7-phenanthroline of the rod, either
toward the ethenyl-bridge or in the direction of one of the
heterocycles (red arrow). These distances do allow π-π
interactions and also explain why the central protons of the 4,7-
phenanthroline nucleus (HCdCH bridge) are dramatically
Figure 2. Crystal structure of the [2]pseudorotaxane tetramer 194+
.
Hydrogen atoms and counterions (PF6-) have been omitted for the sake of
clarity.
Table 1. Important Structural Features of 194+
distances
CusCu
CusN
on one thread:
on one bis-macrocycle:
7.808 Å
12.661 Å
1.999-2.048 Å
2.030-2.052 Å
CusNTHREAD
:
CusNMACROCYCLE
:
PyrazinesPyrazine (centroids of the bis-macrocycles): 8.271 Å
angles
distortion angles
Phen (macrocycle) - Bipy (thread): 53.82°
57.74°
NsCusN
Phen (macrocycle) bite angles:
Bipy (thread) bite angles:
81.51° - 82.67°
81.76° - 82.04°
1
upfield shifted in the H NMR spectrum upon coordination of
the macrocycles to the rods (see experimental section). The
protons of the central HCdCH bridge experience the ring
current effect of the phenyl nucleus belonging to the threaded
ring.
3. Formation of a [2]Pseudorotaxane Tetramer from the
Bis-macrocycle 1 and the Long Thread 3. As already mentioned,
the rod 3 was prepared in view of making a new type of catenane
incorporating two units of 1 and a very large ring passing
through the inner parts of the 4 rings of the two bis-macrocycles.
The synthesis strategy is depicted in Scheme 9.
7 days at room temperature. Even though the starting materials,
the rod as well as the bis-macrocycle, are almost completely
insoluble, the template effect of Cu(I) is strong enough to drive
the reaction to completion and afford the thermodynamically
favored compound 194+. This, again, demonstrates the power
of coordination chemistry, and in particular the efficiency of
copper(I) acting as a “gathering and threading” element.
-
The [2]pseudorotaxane tetramer 194+ was obtained as its PF6
salt. It is well soluble and crystals of 19.4PF6 could be grown
from slow diffusion of THF into a CH2Cl2 solution. The crystal
structure was solved. It is represented in Figure 2. Some relevant
geometrical features of 194+ are given in Table 1.
It is remarkable that the central aromatic groups (phenazine)
of the bis-macrocycles are slightly bent away from each other,
thus increasing the distance between them to 8.271 Å, compared
to 7.808 Å for the copper(I)-copper(I) distances. The threads
on the other hand are bent about 13° toward the copper centers,
adopting some kind of curved banana shape in spite of the
apparent rigidity of the rods, consisting of 6 aromatic groups
in line.
The geometry of the diimine-phen environment around the
metal centers is that of a distorted tetrahedron. In fact, the two
chelates are not orthogonal to one another, their dihedral
distortion angle being only about 54° and 58° instead of the
required 90° for a perfect tetrahedron. This “flattening” of the
geometry brings the phenyl groups in the 2 and 9 positions of
the macrocycle phenanthrolines closer to the thread (see crystal
Since 2 and 3 display exactly the same coordination properties
and considering that, in the presence of the stoichiometric
amount of copper(I), the reaction between 1 and 2 results in a
quantitative yield of the threaded species 194+, the formation
of a precursor (pseudorotaxane) adapted to the strategy of
Scheme 9, consisting of 4 copper(I) atoms, two equiv of 1 and
two equiv of 3, seemed to be very likely to afford the desired
threaded species. In the course of the past decade, various
catenanes and knots incorporating one or several templating
metal centers (copper(I) and ruthenium(II) [2]catenanes, cop-
per(I) and iron(II) trefoil knots) have been prepared by our
group.29 To a large extent, such sophisticated topologies have
become accessible or at least easier to obtain, thanks to the
development of the powerful RCM reaction initiated by Grubbs
(28) (a) Dobson, J.; Green, B. E.; Healy, P. C.; Kennard, C.; Pakawatchai,
C.; White, A. H. Aust. J. Chem. 1984, 37, 649–659. (b) Cesario, M.;
Dietrich-Buchecker, C.; Guilhem, J.; Pascard, C.; Sauvage, J.-P.
J. Chem. Soc., Chem. Commun. 1985, 244–247.
9
11018 J. AM. CHEM. SOC. VOL. 130, NO. 33, 2008

Cyclic [2]Pseudorotaxane Tetramers
A R T I C L E S
Scheme 9. Putative Formation of a Catenane from an Appropriately Functionalized [2]Pseudo-Rotaxane Tetramer via RCM: Principle
Scheme 10. Formation of the [2]Pseudo-rotaxane Tetramer from the Stoichiometric Amounts of Bis-macrocycle 1, Copper(I) and Rod 3
and co-workers.30 The chemical structure of rod 3 was carefully
designed: the ideal length of the allyl-bearing fragments was
estimated from CPK models, allowing the two rods to be linked
together once the threaded precursor was obtained but being
too short to permit cyclization between two terminal ally groups
borne by the same rod.
in passing a long thread through the eye of a needle. Generally
speaking, it represents a key reaction in the synthesis of
catenanes and rotaxanes. In the present case, the thread to be
passed through the ring is 50 atoms long. Perhaps even more
striking is the fact that there are 22 noncoordinating atoms
between the end of the axis and the first diimine nitrogen atom
of the rod met by the copper(I) center and the ring in the course
of the threading step. In terms of intimate mechanism, many
factors of the reaction are still poorly understood in view of
the complexity of the process. Compound 204+ was character-
The [2]pseudorotaxane tetramer 204+ was obtained following
the same experimental procedure as for the [2]pseudorotaxane
tetramer 194+. Two equiv of the axle 3 and two equiv of bis-
macrocycle 1 were reacted with four equiv of [Cu(CH3-
CN)4](PF6) in CH2Cl2/MeCN at room temperature for 7 days.
After filtration and removal of the solvents the [2]pseudoro-
taxane tetramer 20.4PF6 was obtained in quantitative yield
(Scheme 10).
1
ized by H NMR, COESY, ROESY, and mass spectrometry
(see experimental section). Unfortunately, various attempts to
prepare the hypothetical [3]catenane drawn in Scheme 9 using
first generation Grubbs catalyst31 turned out to lead to a mixture
of cyclic compounds only. Although the desired catenane was
clearly identified as the major components of this mixture, we
have not been able to isolate it pure as yet.
Remarkably, as for the synthesis of 194+, the 4-copper
threaded assembly 204+ was obtained quantitatively, in spite
of a much longer thread to be passed through the ring of each
bis-macrocycle. This process is reminiscent of that consisting
Experimental Section
(29) (a) Mohr, B.; Sauvage, J.-P.; Grubbs, R. H.; Weck, M. Angew. Chem.,
Int. Ed. 1997, 36, 1308–1310. (b) Dietrich-Buchecker, C.; Rapenne,
G.; Sauvage, J.-P. J. Chem. Soc., Chem. Commun. 1997, 2053–2054.
(c) Weck, M.; Mohr, B.; Sauvage, J.-P.; Grubbs, R. H. J. Org. Chem.
1999, 64, 5463–5471. (d) Rapenne, G.; Dietrich-Buchecker, C.;
Sauvage, J.-P. J. Am. Chem. Soc. 1999, 121, 994–1001. (e) Mobian,
P.; Kern, J.-M.; Sauvage, J.-P. J. Am. Chem. Soc. 2003, 125, 2016–
2017.
General Methods. Dry solvents were distilled from suitable
drying agents (THF from sodium/benzophenone, CH2Cl2 from
P2O5). Thin-layer chromatography was carried out using precoated
polymeric sheets of silica gel (Macheray-Nagel, POLYGRAM, SIL
G/UV254). Preparative column chromatography was carried out
(30) (a) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18–29. (b)
Grubbs, R. H. Angew. Chem., Int. Ed. 2006, 45, 3760–3765.
(31) Schwab, P.; Grubbs, R. H.; Ziller, J. W. J. Am. Chem. Soc. 1996,
118, 100–110.
9
J. AM. CHEM. SOC. VOL. 130, NO. 33, 2008 11019

A R T I C L E S
Frey et al.
using silica gel (Merck Kieselgel, silica gel 60, 0.063-0.200 mm).
Flash column chromatography was carried out using silica gel
(Merck Geduran, silica gel 60, 40-63 µm).
8 mL of DMF. The solution was degassed and heated to 60 °C
before the bromo-ally poly(ethylene glycol) chain 18 (206.8 mg,
8.17 × 10-4 mol) in 10 mL DMF was added dropwise from a
dropping funnel. After 24 h, the solvent was evaporated, and the
remaining solid was dissolved in CH2Cl2 and washed twice with
100 mL H2O. After additional washing with hexane, the pure white
solid is obtained in 80% yield (90 mg).
Nuclear magnetic resonance (NMR) spectra for 1H were acquired
on Bruker AVANCE 500 or 300 spectrometers. The 13C NMR
spectra were proton-decoupled. The spectra were referenced to
residual proton-solvent references (1H: CD2Cl2 at 5.32 ppm, CDCl3
at 7.25 ppm; 13C: CD2Cl2 at 54.0 ppm and CDCl3 at 77.23 ppm).
In the assignments, the chemical shift (in ppm) is given first,
followed, in brackets, by the multiplicity of the signal (s: singlet,
d: doublet, t: triplet, dd: doublet of doublets, tt: triplet of triplets,
dt: doublet of triplets, m: multiplet), the value of the coupling
constants in Hertz if applicable, the assignment and finally the
number of protons implied.
1H NMR (300 MHz, CD2Cl2, 25 °C): δ ) 9.10 (d, J ) 8.9 Hz,
H1′, 2H), 8.86 (d, J ) 8.7 Hz, H2′, 2H), 8.81 (d, J ) 8.3 Hz, H3′,
2H), 8.78 (dd, J1 ) 2,2 Hz, J2 ) 0.5 Hz, H5′, 2H), 8.34 (s, H6′,
2H), 7.93 (dd, J1 ) 8.2 Hz, J2 ) 2.3 Hz, H4′, 2H), 7.31 (d, J ) 8.7
Hz, Ho′, 4H), 7.24 (s, H8′, 2H), 7.21 (s, H7′, 2H), 7.01 (d, J ) 8.5
Hz, Hm′, 4H), 5.93 (m, Hh′, 2H), 5.32-5.24 (ddt, J1 ) 17.4 Hz, J2
) 1,9 Hz, J3 ) 1,5 Hz, Hj, 2H), 5.19-5.14 (ddt, J1 ) 10.4 Hz, J2
) 1,7 Hz, J3 ) 1,5 Hz, Hi′, 2H), 4.18 (m, Ha′, 4H), 4.00 (dt, J1 )
5.5 Hz, J2 ) 1,5 Hz, Hg′, 4H), 3.87 (m, Hb′, 4H), 3.74-3.56 (m,
Hc′, Hd′, He′, Hf′, 16H), 2.68 (m, H9′, 8H) 1.15 (m, H10′, 12H) ppm.
MS (Maldi-TOF): m/z (%) )1127.508 (100) [3 + H]+ (calcd:
1127.59).
Mass spectra were obtained by using a VG ZAB-HF (FAB)
spectrometer, a VG-BIOQ triple quadrupole, positive mode, a
Bruker MicroTOF spectrometer (ES-MS). MALDI analysis were
performedonanAutoflexIITOF/TOFBrukerDaltronicsspectrometer.
Starting Materials. All chemicals were of the best commercially
available grade and used without further purification (except when
mentioned). 4-Methoxyphenylboronic acid and 5-bromo-2-iodopy-
ridine 5 are commercially available and used without further
purification. Compounds 1,15 4,17 6,18 15,22 and 18,23 were prepared
according to the literature procedures.
X-ray Data Collection and Crystal Structure Determination.
X-ray data for 194+ were collected on a Bruker Nonius Kappa
APEX II diffractometer using graphite-monochromatized Moa
radiation at 173.0 K. Structure solution was performed by SIR-
9232 and refined on F2 by full-matrix least-squares techniques in
three blocks using SHELXL-97.33 Hydrogen atoms were calculated
to their idealized positions and refined as riding atoms (temperature
factor 1.5 times C temperature factor). No absorption correction
was applied. Due to the very heavy disorder of the
OsCH2sCH2sO moieties in the macrocycles and on the solvent
THF and dichloromethane molecules as many as 1779 geometrical
and/or temperature parameter restraints (DFIX, EADP, DELU,
SIMU) had to be used in order to keep the model chemically
acceptable.
3,8-Bis(4-bromo-2′-pyridyl)-4,7-phenanthroline (7). 5-bromo-2-
trimethylstannyl pyridine 6 (1.96 g, 6.05 mmol) and 3,8-dibromo-
4,7-phenanthroline 4 (1 g, 2.96 mmol) were suspended in dry
toluene (130 mL) and the mixture degassed for 5 min. To this,
Pd(PPh3)4 (230 mg, 0.2 mmol) was added, and the resulting reaction
mixture degassed for a further 5 min. It was then refluxed (140
°C) under argon atmosphere for 18 h. A further 160 mg of Pd(PPh3)4
was added, and the reaction stirred for 44 h under reflux.
Evaporation of toluene afforded the crude product as a gray solid
that was washed with MeOH (2 × 150 mL) and Et2O (2 × 150
mL). Compound 7 was extracted from the remaining solid by
washing it 5× with 150 mL of chloroform. After evaporating the
chloroform, the gray solid was washed again with MeOH and Et2O,
giving 1.26 g of a grayish yellow solid (85% yield).
1H NMR (300 MHz, CDCl3, 25 °C): δ ) 9.05 (d, J ) 8.7 Hz,
H1′, 2H), 8.80 (d, J ) 1.6 Hz, H5′, 2H), 8.74 (d, J ) 8.7 Hz, H2′,
2H), 8.64 (d, J ) 9.1 Hz, H3′, 2H), 8.31 (s, H6′, 2H), 8.03 (dd, J1
) 8.4 Hz, J2 ) 2.3 Hz, H4′, 2H) ppm.
MS (FAB): m/z (%) ) 493.0 (100) [7 + H]+ (calcd: 492.9).
3,8-Bis(4-(4-trimethylsilylphenyl)-2′-pyridyl)-4,7-phenanthro-
line (8). The following reactants were added under argon atmosphere
in DMF (total 25 mL) in the following order: compound 7 (200
mg, 0.4 mmol), Pd(PPh3)4 (46 mg, 0.04 mmol), K3PO4 (255 mg,
1.2 mmol), 4-(trimethylsilyl)phenylboronic acid (171 mg, 0.88
mmol). After each addition, the reaction mixture was degassed.
The mixture was then heated to 100 °C and stirred for 28 h. After
cooling to room temperature, the solution was poured over 250
mL of water. The resulting precipitate was filtered off and washed
with Et2O (2 × 250 mL) and EtOH (2 × 250 mL). The product
was extracted from the remaining solid with chloroform (350 mL).
The combined organic fractions were filtered over diatomaceous
earth and evaporated to dryness. After recrystallizing the yellowish-
white product in chloroform, the white product 8 was obtained in
66% yield (166 mg).
3,8-Bis(4-(4-methoxyphenyl)-2′-pyridyl)-4,7-phenanthroline (2).
A solution of 3,8-bis(4-bromo-2′-pyridyl)-4,7-phenanthroline 7 (200
mg, 0.4 mmol), 4-methoxyphenylboronic acid (134 mg, 0.88 mmol)
and potassium carbonate (425 mg, 2 mmol) in 25 mL DMF was
degassed (3× vacuum/argon) before palladium tetrakistriphe-
nylphosphine (46 mg, 0.04 mmol, 10% mol) was added. The
solution was heated at 120 °C under argon and stirred for 3 h, then
15 mg of catalyst was added. After another 18 h of heating, the
reaction mixture was cooled to room temperature and poured into
250 mL of water. The impure product that precipitated was filtered
over diatomaceous earth and washed with EtOH and dichlo-
romethane. The diatomaceous earth-product mixture was then
extracted with boiling chloroform. The organic fractions were
collected and washed one more time with chloroform. Compound
2 is finally obtained in 82% yield (179 mg).
1H NMR (300 MHz, CDCl3, TFA 3%, 25 °C): δ ) 9.42 (d, J
) 8.3 Hz, H1′, 2H), 9.12 (s, H5′, 2H) 8.79 (dd, J1 ) 3.5 Hz, J2 )
1.3 Hz, H4′, 2H), 8.73 (d, J ) 8.2 Hz, H2′, 2H), 8.57 (d, J1 ) 8.8
Hz, H3′, 2H), 7.70 (d, J1 ) 8.8 Hz, H7′, 4H), 7.15 (d, J ) 8.9 Hz,
H8′, 4H), 3.99 (s, HO-CH3, 4H) ppm.
1H NMR (300 MHz, CDCl3, 25 °C): δ ) 9.10 (d, J ) 8.9 Hz,
H1′, 2H), 9.02 (dd, J1 ) 1.6 Hz, J2 ) 0.8 Hz, H11′, 2H), 8.83 (d, J
) 8.5 Hz, H2′, 2H), 8.81 (d, J ) 7.5 Hz, H13,H13′, 2H), 8.37 (s, H6′,
2H), 8.13 (dd, J1 ) 8.0 Hz, J2 ) 2.0 Hz, H4′, 2H), 7.70 (s, H7′, H8′,
8H), 0.33 (s, HSi(CH3)3, 9H) ppm.
MS (ES): m/z (%) ) 547.2161 (100) [2 + H]+ (calcd: 547.2129).
Poly(ethylene glycol)-allyl Thread (3). A round-bottom flask
was loaded under argon atmosphere with the phenol-thread 17, (80
mg, 1.02 × 10-4 mol), Cs2CO3, (216 mg, 6.13 × 10-4 mol) and
MS (ES): m/z (%) ) 631.3131 (100) [8 + H]+ (calcd: 631.2713).
1,4-Dibromo-2,5-diethylbenzene (10). A 50-mL three-necked
round-bottom flask was loaded with commercially available 1,4-
diethylbenzene (5.0 g, 37.2 mmol) which was then cooled to 0 °C.
In the absence of light, I2 (44 mg, 0.17 mmol) was added and the
mixture stirred for 10 min at 0 °C. Then Br2 (12.19 g, 3,9 mL) was
added in the dark via a dropping funnel over a period of 30 min.
The ice-bath was removed and the reaction mixture left at room
temperature for 24 h after which time 30 mL of KOH (20% aqueous
solution) was added to neutralize the excess of bromide. After the
red color had disappeared, the aqueous phase was removed and
(32) SIR97 Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. J. Appl. Crystallogr. 1999, 32, 115–119.
(33) SHELXS-97 and SHELXL-97: Sheldrick, G. M., SHELX97-Programs
for Crystal Structure Analysis (Release 97-2), Institut fu¨r Anorga-
nische Chemie der Universita¨t Go¨ttingen, Tammanstrasse 4, D-3400
Go¨ttingen, Germany, 1998.
9
11020 J. AM. CHEM. SOC. VOL. 130, NO. 33, 2008

Cyclic [2]Pseudorotaxane Tetramers
A R T I C L E S
the crude product dissolved in 200 mL of hot EtOH. The solvents
were partly removed by evaporation until crystallization occurred.
The mixture was left at 4 °C overnight. After filtration the white
product 10 was obtained in 60% yield (6.52 g).
on alumina with pentane/ethyl acetate (100:0 to 70:30), the white
solid 13 was obtained in 73% yield (108 mg).
1H NMR (500 MHz, CD2Cl2, 25 °C): δ ) 9.11 (d, J ) 8.8 Hz,
H1′, 2H), 8.84 (d, J ) 8.6 Hz, H2′, 2H), 8.80 (dd, J1 ) 7.3 Hz, J2
) 0.6 Hz, H3′, 2H), 8.79 (dd, J1 ) 0.7 Hz, J2 ) 0.6 Hz, H5′, 2H),
8.37 (s, H6′, 2H), 7.93 (dd, J1 ) 8.3 Hz, J2 ) 2.0 Hz, H4′, 2H),
7.47 (s, H8′, 2H), 7.17 (s, H7′, 2H), 2.87 (q, J ) 7.5 Hz, H9’b, 4H),
2.73 (q, J ) 7.5 Hz, H9’a, 4H), 1.33 (t, J ) 7.5 Hz, H10’b, 6H), 1.19
(t, J ) 7.5 Hz, H10’a, 6H), 0.41 (s, HSi(CH3)3, 18H) ppm.
1H NMR (300 MHz, CDCl3, 25 °C): δ ) 7.37 (s, Haromatic, 2H),
2.68 (q, J ) 7.5 Hz, H-CH2-, 4H), 1.20 (t, J ) 7.5 Hz, H-CH3, 6H)
ppm.
13C NMR (75 MHz, CD2Cl2, 25 °C): δ ) 142.54, 133.04,
123.01, 28.7, 13.86 ppm.
13C NMR (125 MHz, CD2Cl2, 25 °C): 156.73, 154.71, 149.78,
148.11, 148.06, 138.93, 138.69, 138.64, 138.57, 137.94, 135.78,
132.93, 132.20, 129.97, 125.26, 121.23, 119.77, 28.98, 26.27, 16.75,
16.27, 0.56 ppm.
MS (ES): m/z (%) ) 292.0 (100) [10]+ (calcd: 291.93).
2,5-Diethyl-4-trimethylsilyl-bromobenzene (11). An oven-dried
three-necked round-bottom flask was loaded with 1,4-dibromo-2,5-
diethylbenzene 10 (1 g, 3.42 mmol) and 20 mL of ether under argon.
After cooling the solution to -78 °C, a solution of n-BuLi in hexane
(1.34 M, 3.35 mL, 4.45 mmol) was added slowly dropwise. The
mixture was then allowed to warm up to 0 °C and then cooled
down again to -78 °C. Then trimethylsilylchloride (0.875 mL, 6.84
mmol) was added dropwise and mixture was allowed to warm to
room temperature and stirred for another 15 h. A 10-mL portion
of water was then added and stirred for 10 min. The aqueous phase
was extracted twice with 10 mL of ether. The combined organic
phases were washed with water (2 × 10 mL) and then dried over
MgSO4. After removal of the solvents, the pure product was
recovered as an oil in 75% yield (730 mg).
MS (ES): m/z (%) ) 743,3961 (100) [13 + H]+ (calcd:
743.3960).
3,8-Bis(4-(2,5-diethyl-4-iodophenyl)-2′-pyridyl)-4,7-phenanthro-
line (14). A three neck round-bottom flask was loaded with the
TMS-thread 13 (322 mg, 4.3 × 10-4 mol) and 70 mL of freshly
distilled CH2Cl2. After purging the solution with argon, it was
cooled down to -10 °C. A 19-mL portion of a 0.23 M solution of
ICl (4.6 × 10-3 mol) in freshly distilled and degassed CH2Cl2 was
added slowly. The solution obtained was allowed to warm up to
room temperature and left for 15 h under argon, during which time
an orange precipitate formed. The reaction was then quenched with
Na2S2O5 (stirred until the orange color had disappeared). A 50-mL
portion of water was then added and the aqueous phase was
extracted with CH2Cl2 (3 × 150 mL). The combined organic layers
were then washed with water (3 × 50 mL). After evaporation to
dryness, the white solid product was obtained quantitatively (365
mg).
1H NMR (300 MHz, CDCl3, 25 °C): δ ) 7.45 (s, H7′, 1H), 7.34
(s, H8′, 1H), 2.77 (m, H-CH2-, 4H), 1.29 (m, H-CH3, 6H), 0.38
(s,HSi(CH3)3, 9H) ppm.
13C NMR (75 MHz, CD2Cl2, 25 °C): δ ) 149.45, 139.46,
137.41, 135.58, 131.87, 125.64, 28.94, 28.20, 16.07, 14.37, 0.03
ppm.
1H NMR (500 MHz, CDCl3, 25 °C): δ ) 9.13 (d, J ) 8.9 Hz,
H1′, 2H), 8.85 (d, J ) 8.6 Hz, H2′, 2H), 8.81 (dd, J1 ) 9.8 Hz, J2
) 0.6 Hz, H3′, 2H), 8.73 (dd, J1 ) 2.2 Hz, J2 ) 0.6 Hz, H5′, 2H),
8.39 (s, H6′, 2H), 7.89 (dd, J1 ) 8.2 Hz, J2 ) 2.2 Hz, H4′, 2H),
7.82 (s, H8′, 2H), 7.12 (s, H7′, 2H), 2.81 (q, J ) 7.5 Hz, H9’b, 4H)
2.63 (q, J ) 7.5 Hz, H9’a, 4H), 1.27 (t, J ) 7.5 Hz, H10’b, 6H) 1.16
(t, J ) 7.5 Hz, H10’a, 6H) ppm.
MS (ES): m/z (%) ) 287.2557 (100) [11]. (calcd: 287.0694).
2,5-Diethyl-4-trimethylsilylphenylboronic Acid (12). An oven-
dried 50-mL three-necked flask was loaded with 2,5-diethyl-4-
trimethylsilylbromobenzene 11 (500 mg, 1.75 mmol), 12 mL of
ether and 3 mL of distilled THF under argon. After cooling down
the solution to -78 °C, 3.75 mL (1.4 M solution in hexane) of
n-BuLi (5.25 mmol) was added dropwise. The solution was then
allowed to warm up to -10 °C then cooled to -78 °C again. 1.62
mL of triisopropylborate (7.02 mmol) was slowly added and the
solution warmed up to room temperature and left under argon
overnight. Then, 15 mL of water was added and the solution stirred
for 15 min before evaporation to dryness. The crude product was
dissolved in dichloromethane and washed with water. The aqueous
phase was extracted 3× with 150 mL of dichloromethane. The
combined organic phases were evaporated to dryness. After a rapid
column chromatography on silica with pentane/ethyl acetate as
eluent (100/0 to 65/35), the pure product was obtained in 72% yield
as a white powder (608 mg).
13C NMR (125 MHz, CDCl3, 25 °C): 156.20, 154.73, 149.24,
147.74, 144.30, 141.53, 139.77, 138.02, 137.54, 137.29, 132.69,
131.86, 129.90, 124.88, 121.25, 119.52, 100.59, 33.68, 25.48, 15.64,
14.68 ppm.
MS (ES): m/z (%) )851.1119 (100) [14 + H]+ (calcd:
851.1102).
OTHP-Thread (16). A two-necked round-bottom flask was
loaded under argon atmosphere with 182 mg (0.214 mmol) of the
iodo-thread 14, 210 mg (0.944 mmol) of the 4-(tetrahydro-2H-
pyran-2-yloxy)phenylboronic acid 15, 226 mg (2.14 mmol) of
Na2CO3, in solution in 24 mL of toluene, 8 mL of H2O, and 4 mL
of EtOH. After degassing the mixture, 25 mg (2.14 x10-5 mol) of
Pd(PPh3)4 were added, and the mixture was heated to 90 °C. After
5 h, the reaction mixture was cooled, and the solvents evaporated.
The product was purified by column chromatography on alumina
with pentane/ethyl acetate (100:0 to 50:50). The white product was
obtained in 75% yield (171 mg).
1H NMR (300 MHz, CDCl3, 25 °C): δ ) 8.10 (s, H7′, 1H), 7.41
(s, H8′, 1H), 3,21 (m, 2H), 2.79 (m, H-CH2-, 4H), 1.31 (m, H-CH3
6H), 0.37 (s, HSi(CH3)3, 9H).
,
13C NMR (75 MHz, CD2Cl2, 25 °C): δ ) 148.76, 146.45,
142.91, 136.65, 135.41, 28.56, 28.50, 17.73, 16.35, 0.02 ppm.
MS (ES): m/z (%) ) 301.17 (100) dimethoxyboronic ester
derivative (MeOH used as a solvent for the spectrometry) + Na+
(calcd: 301.18).
1H NMR (300 MHz, CD2Cl2, 25 °C): δ ) 9.14 (d, J ) 8.7 Hz,
H1′, 2H), 8.88 (d, J ) 8.7 Hz, H2′, 2H), 8.83 (d, J ) 7.8 Hz, H3′,
2H), 8.80 (d, J ) 2.4 Hz, H5′, 2H), 8.35 (s, H6′, 2H), 7.96 (dd, J1
) 8.4 Hz, J2 ) 2.4 Hz, H4′, 2H), 7.32 (d, J ) 8.7 Hz, Ho′, 4H),
7.24 (s, H8′, 2H), 7.21 (s, H7′, 2H) 7.12 (d, J ) 8.7 Hz, Hm′, 4H),
5.46 (s, HOTHP, 1H), 3.95-3.64 (m, HOTHP, 2H), 2.67 (m, H9′, 8H),
1.87 (m, HOTHP, 6H) 1.14 (m, H10′, 12H) ppm.
3,8-Bis(4-(2,5-diethyl-4-trimethylsilylphenyl)-2′-pyridyl)-4,7-
phenanthroline (13). A 25-mL round-bottom double-neck flask was
loaded with 3,8-bis(4-bromo-2′-pyridyl)-4,7-phenanthroline 7 (99.5
mg, 0.202 mmol), 215 mg of K3PO4, (1.011 mmol), and 10 mL of
DMF, then degassed before 23 mg of Pd(PPh3)4 (0,202 mmol) was
added under argon. After further degassing, 150 mg of 2,5-diethyl-
4-trimethylsilylphenylboronic acid 12 (0.606 mmol) was added, and
the solution was purged with argon once more before being heated
to 120 °C. After 32 h, 23 mg of catalyst was added again and the
reaction mixture left under argon at 120 °C for additional 18 h.
The solution was then poured into 150 mL of water and the
precipitate collected by filtration. After column chromatography
13C NMR (75 MHz, CD2Cl2, 25 °C): δ ) 156.24, 154.20,
149.43, 147.57, 141.35, 139.40, 139.15, 138.04, 137.59, 136.54,
134.83, 132.46, 131.73, 130.72, 130.29, 130.12, 124.76, 120.78,
119.29, 116.07, 96.63, 62.23, 30.44, 25.71, 25.26, 19.00, 15.61,
15.51 ppm.
MS (Maldi-TOF): m/z (%) )951.511 (100) [16 + H]+ (calcd:
951.483).
9
J. AM. CHEM. SOC. VOL. 130, NO. 33, 2008 11021

A R T I C L E S
Frey et al.
Phenol-Thread (17). A 100-mL round-bottom flask was loaded
under argon atmosphere with OTHP-thread 16 (136 mg, 0.143
mmol), which was dissolved in a minimum of CH2Cl2, then 50
mL of MeOH and 3 mL of concentrated HCl (37%) were added.
The mixture was heated to reflux for 4 h. The solvents were then
evaporated and the remaining solid dissolved in 100 mL of CH2Cl2,
before 150 mL of aqueous NaOH 1 M was added. By adding HCl
(37%) the solution was brought to pH ) 7, then the aqueous layer
was extracted with CH2Cl2 (2 × 100 mL). The combined organic
layers were then washed twice with 100 mL of H2O and after
evaporation of the solvent the pure product was obtained in 95%
yield (104 mg).
(d, J ) 8.6 Hz, H3,H8, 8H), 8.19 (s, H5′, 4H), 8.14 (d, J ) 7.5 Hz,
H4′, 4H), 7.56 (s, H6′, 4H), 7.40 (d, J ) 7.8 Hz, Ho, 16H), 7.23 (d,
J ) 7.8 Hz, Ho′, 8H), 7.17 (s, H7′, 4H), 7.13 (s, H8′, 4H), 6.96 (d,
J ) 8.5 Hz, Hm′, 8H), 6.20 (d, J ) 7.8 Hz, Hm, 16H), 5,90 (m, J1
) 17.0 Hz, J2 ) 10.1 Hz, J3 ) 5.4 Hz, Hh′, 4H), 5.25 (d, J ) 17.0
Hz, Hj′, 4H), 5.13 (d, J ) 10.1 Hz, Hi′, 4H), 4.18 (t, J ) 5.1 Hz,
Ha′, 8H), 4.09-3.89 (m, HR, Hꢀ, Hγ, Hδ Hꢀ, 80H), 3.88 (t, J ) 5.1
Hz, Hb′, 8H), 3.75-3.54 (m, Hc′, Hd′, He′, Hf′, Hg′, 40H), 2.70-2.54
(2m, J ) 7.0 Hz, H9′, 16H), 1.14 (t, J ) 7.0 Hz, H10′, 24H) ppm.
MS (ES): m/z(%) ) 1655.755 (100) [20.PF6]3+ (calcd: 1655.590).
Conclusions
1H NMR (300 MHz, CD2Cl2, 25 °C): δ ) 9.15 (d, J ) 8.7 Hz,
H1′, 2H), 8.89 (d, J ) 8.7 Hz, H2′, 2H), 8.83 (dd, J1 ) 8.1 Hz, J2
) 0.5 Hz, H3′, 2H), 8.78 (dd, J1 ) 2.2 Hz, J2 ) 0.5 Hz, H5′, 2H),
8.37 (s, H6′, 2H), 7.96 (dd, J1 ) 8.1 Hz, J2 ) 2.2 Hz, H4′, 2H),
7.27 (d, J ) 8.6 Hz, Ho′, 4H), 7.23 (s, H8′, 2H), 7.20 (s, H7′, 2H),
6.93 (d, J ) 8.6 Hz, Hm′, 4H), 2.68 (m, H9′, 8H), 1.16 and 1.13 (2t,
J ) 7.6 Hz, H10′, 12H) ppm.
The present report represents another illustration of the
efficiency of copper(I) to act as a template in the formation of
multicomponent threaded species of the rotaxane family. Under
mild conditions, the copper(I)-driven formation of threaded
species composed of two rods and two bis-macrocycles was
shown to be quantitative. This was particularly true for a long
fragment (3), consisting of a rigid aromatic core terminated by
two long flexible chains. The driving force for making such
[2]pseudorotaxane tetramers is the coordination of diimine type
ligands to Cu(I). Each copper(I) center is strongly stabilized
by two diimines, leading to approximately tetrahedral complexes
and, in turn, each ligand “is eager” to bind avidly to a copper(I)
atom. This situation, combined with the fact that the complexes
are relatively labile and thus permit thermodynamic control, is
very favorable to the formation of multicomponent discrete
species. Another important feature of the present assembly
principle is related to the translational entropy factor, which
clearly favors formation of the smallest assembly as possible.
This is one of the possible reasons to explain that no polymer
nor uncharacterised open-chain complex is observed in the
formation of the threaded compounds. Finally, an aesthetically
attractive X-ray structure could be obtained which demonstrates
in a nonambiguous fashion the threaded nature of the 4-copper
complexes.
MS (ES): m/z (%) )783.3608 (100) [17 + H]+ (calcd: 783.694).
[4]Pseudorotaxane (19.4PF6). A solid-solid mixture of the bis-
macrocycle 1 (50 mg, 4.32 × 10-5 mol) and the thread 2 (23.6
mg, 4.32 × 10-5 mol) was suspended in freshly distilled CH2Cl2
(40 mL) under argon. A degassed solution of MeCN containing
[Cu(MeCN)4](PF6) (33.3 mg, 8.94 × 10-5 mol, 20 mL) was added
via canula technique. The solution was stirred at room temperature
avoiding light exposure. After 7 days, the mixture was homoge-
neous. The solvents were then evaporated and the product extracted
from water with dichloromethane. After evaporation of the solvent,
the tetrameric pseudorotaxane 19.4PF6 was obtained quantitatively
(91 mg).
1H NMR (CD2Cl2, 500 MHz, COSY, ROESY, 25 °C): δ )
10.02 (d, J ) 8.2 Hz, H4,H7, 8H), 9.54 (d, J ) 8.9 Hz, H1′, 4H),
8.76 (d, J ) 9.0 Hz, H2′, 4H), 8.61 (d, J ) 8.6 Hz, H3′, 4H), 8.33
(dd, J1 ) 8.6 Hz, J2 ) 2.2 Hz, H4′, 4H), 8.27 (d, J ) 1.8 Hz, H5′,
4H), 8.24 (d, J ) 8.2 Hz, H3, H8, 8H), 7.57 (m, J ) 9.1 Hz, H7′
8H), 7.43 (s, H6′, 4H), 7.34 (m, J ) 8.4 Hz, Ho, 8H), 7.06 (m, J )
9.1 Hz, H8′, 8H), 6.10 (m, J ) 8.5 Hz, Hm, 8H), 3.95-3.78 (m,
HR, Hꢀ, Hγ, Hδ Hꢀ,H-OMe, 92H) ppm.
MS (ES): m/z(%) ) 915.2614 (100) [194+. (calcd: 915.2621).
Crystallographic Details for 194+. Suitable crystals were
obtained from slow diffusion of THF into a CH2Cl2 solution at
room temperature. C245H218Cl8Cu4F24N20O32P4, M ) 5072.09 g
Acknowledgment. We thank the CNRS for financial support.
We acknowledge the French Ministry of Education for fellowships
(J.F. and C.T.) and Luxemburg Ministry of Research for financial
support (C.T.). We are also grateful to Dr. Lionel Allouche (Service
Commun de RMN, Universite´ Louis Pasteur, Strasbourg, France)
for recording the NMR spectra, and to Aure´lie Meˆme and Dr.
Emmanuelle Leize-Wagner (Laboratoire de Dynamique et Structure
Mole´culaire par Spectrome´trie de Masse, ISIS, Universite´ Louis
Pasteur, Strasbourg, France) for recording mass spectra.
mol-1, triclinic, P1 (no. 2), a ) 18.4923(2) Å, b ) 19.6458(4) Å,
j
c ) 20.4339(4) Å, a ) 86.311(1)°, b ) 66.573(1)°, g ) 64.109(1)°,
V ) 6074.0(2) Å3, Z ) 1, Dcalc ) 1.387 Mg m-3, m ) 0.550 mm-1
GOF on F2 ) 1.093, R1 ) 0.1149, wR2 ) 0.3003 [I > 2s(I)].
,
[4]Pseudorotaxane (20.4PF6). To a degassed suspension of 1
(80 mg, 6.91 × 10-5 mol) and 3 (78 mg, 6.91 × 10-5 mol, 1 eq.)
in dry CH2Cl2 (50 mL), a solution of [Cu(MeCN)4](PF6) (52.0 mg,
13.95 × 10-5 mol, 2.02 eq.) in dry MeCN (25 mL) was added.
The mixture immediately turned red but was reacted for further 7
days to complete threading of the bis-macrocycle. The crude was
then filtered and evaporated to dryness giving 20.4PF6 quantitatively
(186 mg).
Supporting Information Available: Crystallographic data for
[4]pseudorotaxane (19.4PF6) in Cif format and as a checkcif
file. A thermal ellipsoid figure of this compound is also included.
This material is available free of charge via the Internet at http://
pubs.acs.org.
1H NMR (CD2Cl2, 500 MHz, COSY, ROESY, 25 °C): δ )
10.03 (d, J ) 8.3 Hz, H4, H7, 8H), 9.67 (d, J ) 8.3 Hz, H1′, 4H),
8.88 (d, J ) 8.3 Hz, H2′, 4H), 8.71 (d, J ) 7.5 Hz, H3′,4H), 8.27
JA801924Y
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11022 J. AM. CHEM. SOC. VOL. 130, NO. 33, 2008