A Fast-moving copper-based molecular shuttle: Synthesis and dynamic properties

Article abstract of DOI:10.1002/chem.200802510

The present report deals with the synthesis of a two-station [2]ro-taxane consisting of a dpbiiq-incorpo-rating macrocycle (dpbiiq: 8,8′-diphen-yl- 3,3′-biisoquinoline) threaded by a coordinating fragment whose complex-ing units are a dpp and a terpy liga

Full text of DOI:10.1002/chem.200802510

DOI: 10.1002/chem.200802510
A Fast-Moving Copper-Based Molecular Shuttle: Synthesis and Dynamic
Properties
Fabien Durola,*[a, b] Jacques Lux,[a] and Jean-Pierre Sauvage*[a]
Abstract: The present report deals with
the synthesis of a two-station [2]ro-
taxane consisting of a dpbiiq-incorpo-
rating macrocycle (dpbiiq: 8,8’-diphen-
copper translation motion between the
two stations of the axle. Based on an
analogous multistep strategy, a related
molecular shuttle has also been pre-
pared that contains exactly the same
axle and stoppers as the first com-
pound but whose threaded ring incor-
porates the sterically hindering dpp
chelate. The translation motions of this
other system are several orders of mag-
nitude slower than the corresponding
movements of the dpbiiq-based com-
pound. The motion corresponding to
the rearrangement of the unstable five-
coordinate copper(I) form of the com-
pounds is relatively fast for both shut-
tles; the half lifetime of the five-coordi-
nate CuI species being below 20 ms for
the dpbiiq-containing system and
below 1 s for the dpp-based molecule.
The reverse motion corresponding to
the rearrangement of the four-coordi-
nate copper(II) complexes is much
slower, especially for the dpp-based
system. It is of the order of several
hours for the dpp-based shuttle and
only one second or less for the dpbiiq
system, under exactly the same condi-
tions. The remarkable difference be-
tween the motion rates for the two
two-station shuttles demonstrates that
the use of a very open chelate such as
dpbiiq is extremely beneficial in the
context of fast-moving molecular ma-
chines.
yl-3,3’-biisoquinoline) threaded by
a
coordinating fragment whose complex-
ing units are a dpp and a terpy ligand
(dpp:
2,9-diphenyl-1,10-phenanthro-
line; terpy: 2,2’,6’,2”-terpyridine). The
[2]rotaxane was prepared in 11 steps
from commercially available or easy-
to-make molecules, without taking into
account the preparation of the dpbiiq-
containing 39-membered ring, which
was available in our group. The ring-in-
corporated bidentate chelate is at the
same time endocyclic and sterically
nonhindering, which is a specific prop-
erty of the dpbiiq-coordinating unit.
This unique feature has a profound in-
fluence on the rate of the ring-and-
Keywords: biisoquinoline · copper ·
molecular machines
· molecular
shuttles · N ligands · rotaxanes
Introduction
lated compounds of the rotaxane family demonstrates that
synthetic chemistry is now powerful enough to tackle prob-
lems whose complexity is sometimes reminiscent of biology,
although the elaboration of molecular ensembles displaying
properties as complex as biological assemblies is still a long-
term challenge. The most efficient strategies for making
such compounds are based on template effects. The first
templated synthesis relied on copper(I).[18] The use of CuI as
template allows one to entangle two organic fragments
around the metal center before incorporating them in the
desired catenane backbone. This metal has been extensively
used as a template in our group[1b,18] or in other research
teams.[19–21] Other transition-metal centers have also been
used successfully in the templated synthesis of various cate-
nanes and rotaxanes.[22–26] Organic templates, assembled via
formation of aromatic acceptor–donor complexes and/or hy-
drogen bonds, have also been very successful.[27–31] Nowa-
days, numerous template strategies are available that have
The field of catenanes and rotaxanes[1] is particularly active,
mostly in relation to the novel properties that these com-
pounds may exhibit (electron and energy transfer,[2] con-
trolled motions and mechanical properties,[3–9] and new “in-
telligent” materials[10–17]). In addition, catenanes represent
attractive synthetic challenges in molecular chemistry. The
creation of such complex functional molecules as well as re-
[a] Dr. F. Durola, J. Lux, Dr. J.-P. Sauvage
Institut Le Bel, Universitꢀ Louis Pasteur
4 Rue Blaise Pascal, 67070 Strasbourg (France)
Fax : (+33)3 90 24 13 68
E-mail: sauvage@chimie.u-strasbg.fr
[b] Dr. F. Durola
Present address: The Skaggs Institute for Chemical Biology
10550 North Torrey Pines Road
La Jolla, CA 92037 (USA)
4124
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Chem. Eur. J. 2009, 15, 4124 – 4134

FULL PAPER
led to the preparation of a
myriad of catenanes and rotax-
anes incorporating various or-
ganic or inorganic fragments
and displaying a multitude of
chemical or physical functions.
Among these functions, the
ability of catenanes and rotax-
anes to behave as molecular
machine prototypes[3–6,28,32] is
certainly the most popular, in
relation to potential applica-
tions in the field of informa-
tion storage and processing at
Scheme 1. Schematic representation of a metal-complexed [2]rotaxane acting as an electrochemically driven
molecular shuttle. The ring contains a coordinating unit interacting with the metal center in both states. The
axis incorporates two chelating units: a bidentate one and a tridentate chelate. It is attached to terminal stop-
pers.
the molecular level as well as the fabrication of molecular
electro- or photo-mechanical devices.[33] In the course of the
last 15 years, our group has proposed several molecular ma-
chine prototypes based on copper-complexed catenanes and
rotaxanes.[34] The driving force for setting the molecular sys-
tems in motion is the preference of the copper(I) or cop-
per(II) complexes for different geometries (four-coordinate
for CuI and five- or six-coordinate for CuII) and thus, their
rearrangement after oxidation or reduction. Critical to the
elaboration of efficient machine prototypes and potential
devices is the rate of the motion. The weak point of transi-
tion-metal-based dynamic systems is their relatively long re-
sponse time: one of the rate-limiting steps in the rearrange-
ment process is the substitution sphere of the metal. Ex-
changing ligands around a copper center can be relatively
slow, especially if the metal is hindered and if its environ-
ment is congested. Herein, we describe a new approach,
based on sterically non- or only slightly hindering ligands
whose incorporation into catenane and rotaxane backbones
is made possible thanks to their particular crescent shape. In
particular, the two-station molecular shuttle[35] reported now
is set in motion much faster than the previous examples
from our group based on sterically hindering ligands. A pre-
liminary account of the electrochemical and dynamic prop-
erties of the present shuttle has been reported recently.[36]
by changing the oxidation state of the metal center is indi-
cated in Scheme 1.
The coordination properties of the two axis ligands have
to be markedly different. In this way, by oxidizing or reduc-
ing the metal center, the system will be strongly destabi-
lized. For the system to relax, the ring and the metal will
have to glide along the axis. The driving force for the rear-
rangement of the rotaxane (i.e., for the shuttling motion of
the metal-coordinated ring between the two “stations“) will
be determined by the energy difference between one of the
two stable states and the corresponding unstable one gener-
ated by metal oxidation or reduction.
The first copper-complexed shuttle prepared and studied
in our group[48] is represented in Scheme 2. In this com-
pound, the thread is flexible, which makes it difficult to
have a clear view of the geometry with, in particular, an ac-
curate knowledge of the distance between the two stations
of the shuttle. In addition, and more important in terms of
function, the coordination site is highly congested in the
four-coordinate situation due the presence of a 2,9-diphenyl-
1,10-phenanthroline motif in the ring. This structural feature
is detrimental to fast ligand exchange and thus to fast mo-
tions.
The molecular shuttle represented in Scheme 2 turned out
to be kinetically very inert. The rearrangements of the un-
I
II
stable species Cu5 and Cu4 , described by Equations (1) and
(2) take place on the minute to hour timescale (the sub-
scripts 4 and 5 indicate the coordination number of the
copper atom).
Results and Discussion
Design of the two-station rotaxanes: Molecular shuttles con-
stitute a promising class of molecular machines. A ring can
glide in a controlled fashion along an axis on which it has
been threaded. This motion can even be realized over large
distances by playing with the length of the various fragments
incorporated in the thread and the number of “stations”
with which a given part of the ring is able to interact. Fol-
lowing the first molecular shuttle from Kaifer, Stoddart and
co-workers,[35] several purely organic examples of such dy-
namic systems have been described,[37–44] some of them
being the active components of molecular electronic
memory.[45–47] The approach of our group is based on transi-
tion metals and, in particular, on CuI and CuII. The principle
of a two-station molecular shuttle whose motions are driven
I
I
ð1Þ
ð2Þ
Cu5 ! Cu4
II
II
Cu4 ! Cu5
As shown recently for “pirouetting” copper-complexed
rotaxanes, decreasing the steric congestion around the
copper center has a strong effect on the rearrangement rates
of the complexes.[49] It thus seemed to be important to de-
velop a new series of molecules whose ring-incorporated
chelate would be as little hindering as possible. Conceptual-
ly, this problem is far from trivial since the chelate has to be
at the same time endotopic or endocyclic so as to be incor-
porated in a ring in such a way that its coordination site be
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4125

F. Durola, J.-P.Sauvage, and J. Lux
induced rearrangement pro-
cesses.[50] As described in the
present report, the acceleration
factor of the shuttling reaction
will even be more pronounced
when replacing the dpp-con-
taining ring of the compound
shown in Scheme 2 by
a
dpbiiq-incorporating fragment.
The chemical structure of
the two rotaxanes reported in
the present article and of the
various constitutive compo-
nents are represented in
Schemes 4, 5, and 6.
The choice of the rings was
dictated by various considera-
tions. Compound
3 incorpo-
rates the wide dpbiiq fragment
and it has therefore to be rela-
tively large to allow the macro-
cycle to occupy a roughly cir-
cular geometry once coordinat-
Scheme 2. The two stable states of a previously reported copper-complexed bistable rotaxane: a slow moving
shuttle.[48] The mobile ring is a 30-membered ring that incorporates a dpp chelate, whereas the “stations” are a
2,9-disubstituted-1,10-phenanthroline unit and a 6,6’,2’,6’’-terpyridine (terpy). As in many other examples from
our group, CuI is stabilized in a four-coordinate situation, that is, by interacting with two bidentate chelates of
the phenanthroline family. In contrast, CuII has a strong preference for higher coordination number (5 or 6)
and in the present case, its most stable coordination sphere will involve a phenanthroline and a terpy.
oriented towards the inner part of the ring in an unambigu-
ous fashion. In this respect, the 8,8’-diphenyl-3,3’-biisoquino-
line (dpbiiq) backbone seems to be ideally suited. As shown
in Scheme 3, the 8,8’-diphenyl-3,3’-biisoquinoline motif is
Scheme 3. a) The use of a dpp fragment as chelate induces high steric
hindrance once a metal is coordinated; b) by using a 3,3’-biisoquinoline
chelate, which is substituted far from the nitrogens in positions 8 and 8’,
a sterically nonhindering macrocycle is obtained.
such that endocyclic coordination will be certain and, equal-
ly important, the complexed metal center will be remote
from any organic group of the ligand organic backbone. In
ꢀ
dpp (Scheme 3a), the shortest C C distance between the
phenyl rings borne by the phen nucleus at its 2- and 9-posi-
tions is around 7 ꢂ, whereas it is around 11 ꢂ for the two
corresponding phenyl rings of dpbiiq (Scheme 3b).
The replacement of the dpp chelate by a dpbiiq in the
Scheme 4. Chemical formula and schematic representation of the CuI ro-
axis of “pirouetting” pseudo-rotaxanes turned out to have a
very significant effect on the rate of the electrochemically
+
+
taxanes 14 and 24
.
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A Fast-Moving Copper-Based Molecular Shuttle
FULL PAPER
of the copper center, that is, simultaneous participation of
the two stations (dpp and terpy) in the transition state of
the shuttling species when the copper-complexed ring moves
from one part to the other, can be totally excluded. This fea-
ture will thus make the ligand-exchange reaction particular-
ly difficult and, as a consequence, the motion should be con-
siderably slower than in systems where a concerted mecha-
nism is likely to be operative such as in “pirouetting” rotax-
anes.[51]
+
Synthesis of the copper(I) rotaxanes 14 and 24+: In the
present section we will detail the synthetic procedures of
a) the thread and b) the full rotaxanes.
a) Synthesis of the singly stoppered axis: The axis precur-
sor 18 is made up of three parts: the stopper, the dpp unit,
and the terpyridine. Due to the complexity of this molecule,
a
convergent strategy of synthesis has been adopted
(Scheme 7). The stopper fragment 8 is obtained in two steps
from the stopper molecule 6[52] usually used and previously
synthesized (in three steps) in our group. The first step is a
Williamson reaction with commercially available 2-[2-(2-
chloroethoxy)ethoxy]ethanol, under classical conditions with
cesium carbonate in DMF, and leads to compound 7 (90%
yield). In the second step, the alcohol function of 7 is first
activated with a mesyl group and then substituted with an
iodide. The mesylation reaction is done under usual condi-
tions, using mesyl chloride, dichloromethane and triethyla-
mine with a strict control of temperature. The crude product
is then allowed to react with an excess of sodium iodide in
acetone to give the halogenated stopper fragment 8 in high
yield (95%).
Scheme 5. Chemical formula and schematic representation of the rings 3
and 4.
The dpp fragment 11 is obtained in three steps from com-
mercially available 1,10-phenanthroline. The two first steps
are different substitutions of the a-positions to the nitrogen
atoms of the phenanthroline, by following a very efficient
organometallic method developed years ago in our group by
C. O. Dietrich-Buchecker.[53] In both cases, a solution of the
appropriate aryl lithium compound is first prepared, under
strict control of the temperature, by reaction of tert-butyl-
lithium or neo-butyllithium with 2-(4-bromophenoxy)-tetra-
hydro-2H-pyran and 1,4-dibromobenzene, respectively. This
solution is then added to a solution of the substrate, namely
1,10-phenanthroline and mono-substituted phenanthroline 9,
respectively, hydrolyzed, and finally rearomatized with
MnO2. After treatment and purification, the corresponding
substituted phenanthroline is obtained, namely monosubsti-
tuted phenanthroline 9 (67% yield) and disubstituted phe-
nanthroline 10 (80% yield), respectively. The THP protec-
tive group on the phenol function is finally removed in the
presence of hydrochloric acid in methanol to give the bi-
functionalized 2,9-diaryl-1,10-phenanthroline fragment 11
(90% yield).
Scheme 6. Chemical formula and schematic representation of the axis 5.
ed to CuI and threaded by the axis. On the other hand, its
size should be adapted to that of the stopper and can not
exceed 42 or 43 atoms in its periphery without relatively
easy unthreading of the end-stoppered axis from the ring in
the copper-free compound. The dpp-incorporating macrocy-
cle 4 is a classical ring from our group and, in particular, it
is this cyclic compound which was used in the previous shut-
tle of Scheme 2.
As far as the structure of the threaded fragment is con-
cerned (Scheme 6), the stoppers are the same ones as for
several other studies. For comparison purposes and to dem-
onstrate that dpbiiq is much more efficient than dpp as an
exchangeable chelate, we favored chemical structures that
induced, a priori, slow motions whose kinetics can be inves-
tigated by using classical electrochemical methods. Conse-
quently, specific to the present study is the structure of the
central part, which is very rigid and composed of aromatic
rings only. In this way, the axis has a limited possibility to
fold up, which leads to a reasonably good estimation of the
distance between the coordination sites of the two stations.
In addition, the structure is such that a concerted mecha-
nism for ligand substitution within the coordination sphere
Halogenated stopper fragment 8 and phenolic fragment
11 are coupled by using a Williamson reaction under classi-
cal conditions, in DMF with cesium carbonate as a base, to
give the bromo-ended singly stoppered fragment 12 (46%
yield). The bromide is then changed into a boronic ester
function thanks to a palladium-catalyzed reaction involving
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F. Durola, J.-P.Sauvage, and J. Lux
Scheme 7. Synthesis of a rigid mono-stoppered two-station axis precursor. a) Cs2CO3 in DMF, 908C, 48 h, 90%; b) MsCl, NEt3 in CH2Cl2, 08C, 4 h; then
NaI in Me2CO, reflux, 16 h, 95%; c) tBuLi in THF, ꢀ788C, 30 min; then 08C, 2 h; then MnO2, 258C, 16 h, 67%; d) BuLi in Et2O, 0 8C, 3 h; then MnO2,
258C, 16 h, 80%; e) HCl in MeOH, reflux, 16 h, 90%; f) Cs2CO3 in DMF, 508C, 16 h, 46%; g) [PdACTHNUGTRENUNG(dppf)Cl2], KOAc in dioxane, 808C, 16 h, (100%);
h) [PdACHTUNGTRENNUNG(PPh3)4], Na2CO3 in toluene/H2O/EtOH, 908C, 2 h, 38%; i) [PdACHTUTGNERN(NGUN PPh3)4], Na2CO3 in toluene/H2O/EtOH, 908C, 16 h; 93%; j) HCl in MeOH/
CH2Cl2, reflux, 4 h, 79%.
a diboron compound and [Pd
G
latter being necessary to solubilize the organic compounds.
In fact, the phenol-ended two-station thread 18 is poorly
soluble and therefore difficult to purify, which can also ex-
plain the non-quantitative yield (79%) of this deprotection
reaction.
phenylphosphino)ferrocene) in dioxane. The crude product
can not be purified but the boronic ester 13 seems to be ob-
tained quantitatively.
Dibromoterpyridine 14 is synthesized following an organ-
ometallic three-step strategy from commercially available
2,6-dibromopyridine and 5-bromo-2-iodopyridine.[53] In par-
allel, the formation of 4-(tetrahydro-2H-pyran-2-yloxy)phe-
nylboronic acid 15 is carried out in a classical way, by using
butyllithium and triisopropyl borate on commercially avail-
able 2-(4-bromophenoxy)-tetrahydro-2H-pyran.[54] These
two compounds react then in equal quantities under Suzuki
coupling conditions in toluene, water, and ethanol, with [Pd-
b) Synthesis of the rotaxanes: The two copper(I) molecular
+
+
shuttles 14 and 24 are synthesized from the same two-sta-
tion thread 18 and two different chelating rings. The synthe-
sis of these macrocycles, the recent biisoquinoline-based 39-
membered ring 3[55] and the former phenanthroline-based
30-membered ring 4,[56] have been previously described in
the literature. The formation of these two copper(I) rotax-
anes follows the same threading-and-stoppering strategy and
is carried out using exactly the same experimental proce-
dure (Scheme 8). In a first step, a dichloromethane solution
ACHTUNGTRENNUNG(PPh3)4] as a catalyst and with Na2CO3 as a base. Seeing that
terpyridine 14 contains two bromide functions, and since
only one equivalent of boronic acid is used, a statistical mix-
ture of nonsubstituted, mono- and disubstituted terpyridines
is obtained, from which asymmetric terpyridine 16 is isolat-
ed, by chromatography, in a satisfying yield (38%).
Finally, bromo-ended terpyridine fragment 16 and stop-
per-phenanthroline fragment 13, functionalized with a bor-
onic ester, are assembled together by a palladium-catalyzed
Suzuki coupling reaction, under classical conditions. Mono-
stoppered thread 17, containing a dpp and a terpyridine
ligand (called two-station thread), is thus obtained in a very
good yield (93%). The last step is the deprotection of the
phenol function, the THP group is removed in the presence
of hydrochloric acid in methanol and dichloromethane, the
of macrocycle 3 or 4 and [CuACTHNUTRGENNUG(MeCN)4]ACHTUNTGREN[NGUN PF6] dissolved in
acetonitrile are mixed to form a bright orange complex con-
sisting of one ring and one metal center. To this solution is
then added a solution of one equivalent of the thread 18 in
+
dichloromethane. The dark red threaded complex, 194 or
+
204 respectively, is instantaneously formed. Under rigor-
ously controlled stoichiometric conditions, the thermody-
namic equilibrium implies that the threaded complex is the
only species present in solution once the equilibrium has
been reached. The solvent is then evaporated and the crude
+
product, either 194 or 204+, is then used without further pu-
rification due to the relative air- and base-sensitivity. The
last stoppering reaction is a classical Williamson reaction be-
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A Fast-Moving Copper-Based Molecular Shuttle
FULL PAPER
+
Scheme 8. Threading and stoppering reactions leading to rotaxanes 14 and 24+. a) [Cu
ACHTUNGTREN(NUG MeCN)4]ACHTUNGTERN[NUGN PF6] in CH2Cl2/MeCN, 258C, 30 min; then 18 in
CH2Cl2, 258C, 16 h; b) stopper 8, Cs2CO3, sodium ascorbate in DMF, 508C, 20 h, 32% and 31% for 1+4 and 2+4, respectively.
tween the terminal phenol function of the threaded complex
and an excess of iodo-ended stopper molecule 8, with
cesium carbonate in DMF, in the presence of sodium ascor-
bate to prevent oxidation of copper(I). The yield of such a
reaction is generally moderate because of the sensitivity of
copper(I) complexes to basic conditions. In fact, copper(I)
rotaxanes 14 and 24 are obtained, after purification, with
satisfactory but medium yields of 32% and 31%, respective-
ly.
were estimated by regular cyclic voltammetry. As far as the
first process is concerned (movement of the ring from the
terpy subunit to the dpp fragment), the electrochemical
technique is not ideal and allows only to estimate a lower
limit for the rate constant of the motion. The translation
motion takes place within seconds or less for both systems
+
+
+
2+
15 and 25+, the dpbiiq-containing ring of 15 being shifted
from the terpy to the dpp fragment of the axle within tens
Since copper(I) complexes are preferably tetracoordinat-
ed, it is logical that, in rotaxanes 1+ and 2+, the bidentate
macrocycle and the metal center are linked to the two-sta-
tion thread by the means of the bidentate phenanthroline
1
ligand. This can be proved by H NMR spectroscopy. Con-
cerning the example of rotaxane 1+ (Figure 1), some pro-
tons of the copper(I) complex are highly upfield-shifted
compared to their counterparts on the rotaxaneꢃs organic
precursors. These protons, represented on the organic com-
ponents of 1+ in Figure 1, are all localized around the phe-
nanthroline of the thread and around the coordination site
of the macrocycle. This can be explained by the fact that
they are all subjected to strong ring current effects, due to
the proximity of the many aromatic fragments around the
central copper(I) atom. This observation confirms that the
species obtained is the four-coordinate complex, involving
two bidentate units as chelates around the central metal.
Electrochemical study: Translation of the copper-com-
plexed macrocyle between the biscoordinating dpp and tris-
coordinating terpy units is perfectly reversible as described
previously (Scheme 1).[36] Whereas the oxidation and reduc-
tion reactions can be considered as instantaneous in compar-
ison with the much slower macrocycle gliding motions, the
decoordination of the thermodynamically unstable com-
plexes, and thus the translation by ligand exchange, are rela-
tively slow. For both molecular shuttles, two different pro-
cesses can be distinguished: 1) the translation motion of the
ring-and-copper sub-complex in the thermodynamically un-
stable five-coordinate copper(I) complex and 2) the reverse
motion, corresponding to the rearrangement of the unstable
four-coordinate copper(II) species. The rearrangement rates
+
Figure 1. 1H NMR spectra of 14 and its precursors 17 and 3.
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F. Durola, J.-P.Sauvage, and J. Lux
of milliseonds or even faster. As expected, the second pro-
valent CuII center. The back and forth motion can finally be
described by the Equations (3)–(6):
2+
2+
cess is much slower for both unstable species 14 and 24
,
in agreement with previous studies from our group.[34,49] By
varying the potential scan rate, the speed of the translation
performed by the copper-complexed ring can be estimated.
Two important cyclic voltammograms (CVs) are represented
in Figure 2.
ꢀeꢀ
þ
2þ
ð3Þ
ð4Þ
ð5Þ
ð6Þ
14
14
15
15
1
4
ƒƒ!
k¼2 sꢀ1
gliding
2þ
2þ
2þ
1
ƒƒƒ!
5
4
þeꢀ
þ
1
ƒƒ!v
5
k>50 sꢀ1
þ
þ
1
ƒƒƒƒ!
gliding
By comparing this fast electrochemically driven shuttle
with the previous system, it is clear that the biisoquinoline
ligand has a pronounced kinetic effect, obviously due to its
nonsterically hindering nature.
To allow a thorough comparison of the macrocyclesꢃ ki-
+
netic properties, rotaxane 24 was synthesized with the same
axis and stoppers as in 14+, but with the strongly shielding
dpp-based macrocycle 4, a classical building block of our re-
+
search group. By contrast, after oxidation of 24 the thermo-
2+
dynamically unstable complex 24 seems to be kinetically
stable for several hours. A CV of this rotaxane in shown in
Figure 2c (100 mVsꢀ1).
To confirm the coordination number of copper(II) both in
thermodynamically stable (five-coordinated) and unstable
(four-coordinated) states, electronic spectroscopy measure-
ments were performed on 12+ and 22+. First the dark red so-
+
ꢀ
lution of [14 ]ACTHNGUTERNNUG
ꢀ
oxidized with NO+BF4 , in a similar way to previous stud-
ies,[58] which resulted in an immediate color change to give a
very pale yellow solution. The electronic spectrum shows a
band maximum at lmax ꢁ640 nm (eꢁ150), which is a clear
indication of a five-coordinate copper(II).[59] This form of
the complex was obtained quickly (mixing time), as expect-
ed from the electrochemical study. By contrast, a similar ex-
+
Figure 2. Cyclic voltammetry study of rotaxanes 14 and 24+. a) 14+: po-
tential range: ꢀ0.4 V to 1.0 V, followed by 1.0 V to ꢀ0.4 V; b) 14+: two
consecutive scans; c) 24+: CV of rotaxane 24 for comparison purpose.
+
+
ꢀ
The electrochemical experiments were performed at room temperature
in a 0.1m solution of Bu4NBF4 in MeCN/CH2Cl2 (9:1), with a Pt working
electrode, Ag wire as a pseudoreference electrode, and Pt wire as a coun-
terelectrode.
periment done with [24 ]AHCUTNEGRN[NUG PF6 ] under the same conditions
gave a green solution (lmax ꢁ670 nm, eꢁ750), representative
of a four-coordinate copper(II) complex, as expected for the
+
kinetically inert complex 24
.
Following the same method as in previous studies,[57] the
rearrangement rate was estimated from the shape of the CV.
On the CV shown in Figure 2a (400 mVsꢀ1) it appears that,
Conclusions
+
2+
after oxidation of Cu4 to Cu4 and subsequently by scan-
ning the potential from +1.0 V to ꢀ0.4 V, almost one half of
the complexes have undergone a translation to become pen-
tacoordinated, whereas the other half stays tetracoordinat-
ed. The half reaction time corresponding to the rearrange-
ment step, which is monomolecular (first order), can then be
deduced as well as the kinetic constant. As shown by the
CV in Figure 2b, whose second cycle is almost identical to
the first one, and in accordance with other investigations
made on previous copper-based molecular machines, the un-
Using the three-dimensional template effect of copper(I), a
pseudo-rotaxane containing a dpbiiq-incorporating ring and
a two-coordinating station axle has been assembled. The
threading step was carried out using a mono-stoppered axis
and, as observed in many previous examples, it was quanti-
tative. The second stoppering step was performed on the
threaded intermediate. The yield of this key reaction was
relatively mediocre (32%) and clearly represents the weak
point of the whole synthetic procedure leading to the de-
sired [2]rotaxane. An analogous [2]rotaxane was also pre-
pared, whose chemical structure is close to that of the first
compound. The only difference is that of the ring which now
contains a sterically hindering chelate of the dpp family. The
second stoppering reaction was not better yielding than that
+
stable five-coordinate copper(I) complex 15 rearranges
much faster than the four-coordinate copper (II) complex
142+. As expected, ligand–exchange reactions around the
singly charged metal center CuI are easier than around a di-
4130
www.chemeurj.org
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 4124 – 4134

A Fast-Moving Copper-Based Molecular Shuttle
FULL PAPER
7.14 (d, 6H; J=8.7 Hz), 7.13 (d, 2H; J=8.7 Hz), 6.78 (d, 2H; J=9.0 Hz),
4.08 (t, 2H; J=4.7 Hz), 3.80 (t, 2H; J=4.8 Hz), 3.73 (t, 2H; J=6.6 Hz),
3.65 (m, 6H), 3.25 (t, 2H; J=6.6 Hz), 1.29 ppm (s, 27H); ES-MS: m/z
769.3035 (calcd 769.3088 for [C43H55IO3+Na+]).
of the first compound. As shown by a succinct electrochemi-
cal study, the shuttle whose ring incorporates the wide and
nonsterically hindering dpbiiq chelate undergoes molecular
motions which are several orders of magnitude faster than
those of the dpp-based shuttle. This spectacular difference
will now be exploited to construct other more sophisticated
molecular machines such as muscles or presses, based on the
dpbiiq-coordinating fragment.
Synthesis of 2-[4-(OTHP)phenyl]phenanthroline 9: 2-(4-Lithiophenoxy)-
tetrahydro-2H-pyran was prepared by interconversion of commercially
available 2-(4-bromophenoxy)tetrahydro-2H-pyran with two equivalents
of tBuLi;
(17 mmol) in THF (50 mL) was obtained by slow addition of tBuLi
(35 mmol) to solution of 2-(4-bromophenoxy)-tetrahydro-2H-pyran
a
solution of 2-(4-lithiophenoxy)tetrahydro-2H-pyran
a
(4,37 g, 17.0 mmol) in THF (25 mL) at ꢀ788C under argon. After being
stirred for 30 min at ꢀ788C, this solution was slowly added to a degassed
solution of 1,10-phenanthroline (3.0 g, 16.6 mmol) in THF (70 mL) main-
tained at ꢀ28C. The phenanthroline solution turned dark red instantane-
ously and was stirred under argon at 08C for 2 h. Thereafter the reaction
was quenched by addition of water (30 mL) and the resulting mixture
was evaporate to dryness. The residue thus obtained was taken up in a
mixture of CH2Cl2 and water and decanted. The aqueous layer was
washed and extracted with more CH2Cl2. The organic phase was then
rearomatized by successive additions of batches of MnO2 (25 g). The
rearomatization was monitored by TLC (compound 9 can be recognized
by a blue luminescence under UV light). The solution was then dried by
addition of MgSO4 and the black MnO2/MgSO4 slurry was filtered
through sintered glass with celite. After evaporation of the solvent, the
crude product was purified by column chromatography over silica gel,
with CH2Cl2 as the eluent, to give the title compound 9 (pale yellow
glassy solid, 3.98 g, 67%). 1H NMR (300 MHz, CD2Cl2, 258C, TMS): d=
9.22 (dd, 1H; J=4.2, 1.8 Hz), 8.34 (d, 1H; J=8.4 Hz), 8.32 (dd, 1H; J=
8.1, 1.8 Hz), 8.31 (d, 2H; J=9.0 Hz), 8.12 (d, 1H; J=8.4 Hz), 7.87 (d,
1H; J=8.7 Hz), 7.82 (d, 1H; J=8.7 Hz), 7.69 (dd, 1H; J=8.1, 4.2 Hz),
7.26 (d, 2H; J=9.0 Hz), 5.57 (t, 1H; J=3.3 Hz), 3.96 (m, 1H), 3.67 (m,
1H), 2.07 (m, 2H), 1.94 (m, 2H), 1.74 ppm (m, 2H); ES-MS: m/z
357.1631 (calcd 357.1603 for [C23H20N2O2+H+]).
Experimental Section
General: Some solvents were dried in the laboratory by distillation under
argon, over the appropriate drying agent: tetrahydrofuran and diethyl
ether over sodium and benzophenone, dichloromethane over calcium hy-
dride, and triethylamine over potassium hydroxide. Other anhydrous sol-
vents used (DMF and dioxane) are commercially available. Thin-layer
chromatography was performed by using glass sheets coated with silica
or neutral alumina. Column chromatographies were carried out on silica
gel (Kieselgel 60, 0.063–0.200 mm or 0.040–0.063 mm, Merck) or alumina
(Aluminiumoxid 90 standardized or acid, 0.063–0.200 mm, Merck).
1H NMR spectra were acquired on either
a Bruker AVANCE 300
(300 MHz) or a Bruker AVANCE 500 (500 MHz) spectrometer. The
spectra were referenced to residual proton-solvent references. 1H:
[D6]DMSO: d=2.50 ppm, CD2Cl2: d=5.32 ppm, CDCl3: d=7.26 ppm.
Mass spectra were obtained by using a VG ZAB-HF (FAB) spectrome-
ter, a VG-BIOQ triple quadrupole, positive mode, a Bruker MicroTOF
spectrometer (ES-MS), or a Bruker Daltonics autoflex II TOF/TOF spec-
trometer with dithranol as a matrix (MALDI).
Synthesis of stopper with hydroxy-ended chain 7: 4-[Tris(4-tert-butylphe-
nyl)methyl]phenol
6 (2.00 g, 3.96 mmol), cesium carbonate (2.50 g,
Synthesis of 2-[4-(OTHP)phenyl]-9-(4-bromophenyl)phenanthroline 10:
A 6.9 mL portion (11 mmol) of a 1.6m nBuLi solution in hexane was rap-
idly added to a degassed solution of p-dibromobenzene (2.9 g, 12 mmol)
in distilled diethyl ether (20 mL) at 08C and allowed to warm at room
temperature. The p-bromophenyllithium solution thus obtained was
slowly added, by the means of a double-ended needle, to a degassed sus-
pension of phenanthroline compound 9 (2.14 g, 6 mmol) in distilled dieth-
yl ether (70 mL) kept at 08C. After the resulting dark red solution was
stirred for 3 h under argon at 08C, it was hydrolyzed with water (25 mL)
at 08C. The ether layer was decanted and the aqueous layer extracted
three times with CH2Cl2. The combined organic layers were thereafter
rearomatized by addition of MnO2 (15 g, 170 mmol) under effective stir-
ring overnight. The rearomatization was monitored by TLC (compound
10 can be recognized by a blue luminescence under UV light). After the
mixture was dried over Na2SO4, the black slurry could easily be filtered
on a sintered glass with celite, washed with CH2Cl2, and the filtrate
evaporated to dryness. The crude product was purified by column chro-
matography over silica gel, with CH2Cl2 as the eluent, to give the title
7.67 mmol), and 2-[2-(2-chloroethoxy)ethoxy]ethanol (1.2 mL, 1.4 g,
8.26 mmol) were mixed in dry DMF (150 mL) and stirred at 908C for
24 h.
More
2-[2-(2-chloroethoxy)ethoxy]ethanol
(1.2 mL,
1.4 g,
8.26 mmol) was added and the reaction mixture stirred for 24 h. The sol-
vent was removed and the residue was taken up with CH2Cl2/H2O. The
organic phase was separated and the aqueous phase extracted twice with
CH2Cl2. The combined organic phases were washed first with brine, then
with distilled water. The solvent was removed and the residue purified by
chromatography on silica gel by using CH2Cl2 as the eluent to give the
title compound 7 (white solid, 2.26 g, 90%). 1H NMR (300 MHz, CDCl3,
258C, TMS): d=7.22 (d, 6H; J=8.7 Hz), 7.07 (d, 8H; J=8.7 Hz), 6.77
(d, 2H; J=9.0 Hz), 4.11 (t, 2H; J=4.8 Hz), 3.85 (t, 2H; J=4.8 Hz), 3.71
(m, 6H), 3.61 (t, 2H; J=4.4 Hz), 2.38 (brs, 1H), 1.30 ppm (s, 27H).
Synthesis of stopper with iodo-ended chain 8: Compound 7 (2.36 g,
3.7 mmol) was dissolved in dry CH2Cl2 (250 mL). The solution was
cooled to about ꢀ28C in an ice/salt mixture, then triethylamine (8 mL)
was added. The subsequent addition of methylsulfonyl chloride (0.7 g,
0.5 mL, 6.1 mmol) in CH2Cl2 (60 mL) was made dropwise over a period
of 1 h; under an argon atmosphere. The solution was then allowed to stir
at 08C for 3 h. Distilled water (50 mL) was then added dropwise and the
mixture was allowed to warm to room temperature. The organic phase
was separated and the aqueous phase extracted twice with CH2Cl2. The
combined organic phases were washed with distilled water. The solvent
was evaporated and the residue purified by chromatography on silica gel
by using CH2Cl2 as the eluent to give the mesylated compound (white
solid, 2.52 g, 95%). It was then dissolved in acetone (200 mL) containing
sodium iodide (10 g, 67 mmol) and heated to reflux overnight, under an
argon atmosphere. A white precipitate of sodium mesylate appeared. The
solvent was evaporated and the residue dissolved in CH2Cl2 (100 mL)
and distilled water (100 mL). The organic phase was separated and the
aqueous phase extracted twice with CH2Cl2. The combined organic
phases were washed with distilled water. The solvent was evaporated and
the residue purified by chromatography on silica gel by using CH2Cl2 as
the eluent to give the title compound 8 (white solid, 2.50 g, 95%).
1H NMR (300 MHz, CD2Cl2, 258C, TMS): d=7.26 (d, 6H; J=8.7 Hz),
1
compound 10 (pale yellow glassy solid, 2.44 g, 80%). H NMR (300 MHz,
CD2Cl2, 258C, TMS): d=8.38 (d, 2H; J=9.0 Hz), 8.34 (d, 2H; J=
9.0 Hz), 8.32 (d, 1H; J=8.4 Hz), 8.29 (d, 1H; J=8.4 Hz), 8.11 (d, 1H;
J=8.4 Hz), 8.10 (d, 1H; J=8.4 Hz), 7.80 (d, 1H; J=8.7 Hz), 7.77 (d, 1H;
J=8.7 Hz), 7.74 (d, 2H; J=8.7 Hz), 7.25 (d, 2H; J=8.7 Hz), 5.55 (t, 1H;
J=3.2 Hz), 3.95 (m, 1H), 3.65 (m, 1H), 2.03 (m, 2H), 1.92 (m, 2H),
1.69 ppm (m, 2H); ES-MS: m/z 511.0992 (calcd 511.1021 for
[C29H23BrN2O2+H+]).
Synthesis of 2-(4-hydroxyphenyl)-9-(4-bromophenyl)phenanthroline 11:
Phenanthroline compound 10 (2.44 g, 4,77 mmol) was dissolved in metha-
nol (200 mL) in the presence of a catalytic amount of a 37% solution of
HCl (10 drops). The mixture was heated to reflux overnight (ca. 18 h).
The solvent was removed and the product was dispersed in distilled
water (100 mL) and CH2Cl2 (200 mL). The aqueous layer was neutralized
with a 1m solution of NaOH and the two layers were separated (a precip-
itate was in suspension in CH2Cl2). Pentane (200 mL) was then added to
the organic phase and the precipitate was filtered to give the title product
Chem. Eur. J. 2009, 15, 4124 – 4134
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
4131

F. Durola, J.-P.Sauvage, and J. Lux
11. This product was not soluble enough to be more purified and was
therefore used without further purification (yellow solid, 1.84 g, 90%).
1H NMR (300 MHz, [D6]DMSO, 258C, TMS): d=8.55 (d, 1H; J=
8.7 Hz), 8.53 (d, 1H; J=9.3 Hz), 8.41 (d, 2H; J=8.4 Hz), 8.34 (d, 1H;
J=8.7 Hz), 8.30 (d, 2H; J=8.4 Hz), 8.27 (d, 1H; J=9.3 Hz), 7.96 (s,
2H), 7.81 (d, 2H; J=8.4 Hz), 7.00 ppm (d, 2H; J=8.7 Hz); ES-MS: m/z
429.0344 (calculated 429.0423 for [C24H15BrN2O+H+]).
lution was heated at 908C overnight (about 18 h). The organic layer was
then decanted and the aqueous layer was extracted three times with
CH2Cl2. The combine organic layer was washed with distilled water and
evaporated. The crude product was purified by chromatography on alu-
minium oxide by using CH2Cl2 as the eluent to give the title compound
17 (colorless glassy solid, 340 mg, 93%). 1H NMR (CD2Cl2, 300 MHz):
d=9.10 (dd, 1H; J=2.3, 0.7 Hz, tp1), 8.93 (dd, 1H; J=2.4, 0.8 Hz, tp9),
8.79 (dd, 1H; J=8.3, 0.7 Hz, tp3), 8.73 (dd, 1H; J=8.3, 0.7 Hz, tp7), 8.63
(d, 2H; J=8.6 Hz, sp3), 8.55 (dd, 1H; J=7.9, 1.1 Hz, tp6), 8.51 (dd, 1H;
J=7.9, 1.0 Hz, tp4), 8.43 (d, 2H; J=8.9 Hz, sp2), 8.38 (d, 1H; J=8.5 Hz,
ph5), 8.31 (d, 1H; J=8.5 Hz, ph2), 8.25 (d, 1H; J=8.4 Hz, ph6), 8.24
(dd, 1H; J=8.4, 2.5 Hz, tp2), 8.12 (d, 1H; J=8.5 Hz, ph1), 8.07 (dd, 1H;
J=8.3, 2.4 Hz, tp8), 8.00 (t, 1H; J=7.9 Hz, tp5), 7.98 (d, 2H; J=8.5 Hz,
sp4), 7.83 (s, 2H; ph3–4), 7.65 (d, 2H; J=8.9 Hz, sp5), 7.23 (d, 6H; J=
8.7 Hz, st4), 7.19 (d, 2H; J=8.9 Hz, sp6), 7.16 (d, 2H; J=8.8 Hz, sp1),
7.13 (d, 6H; J=8.8 Hz, st3), 7.12 (d, 2H; J=8.9 Hz, st2), 6.78 (d, 2H; J=
9.0 Hz, st1), 5.49 (t, 1H; J=3.1 Hz, pr1), 4.25 (dd, 2H; J=6.0, 4.5 Hz,
c6), 4.09 (dd, 2H; J=6.1, 4.6 Hz, c1), 3.91 (m, 1H; pr2), 3.90 (dd, 2H;
J=4.6, 3.4 Hz, c5), 3.83 (dd, 2H; J=4.9, 3.4 Hz, c2), 3.73 (s, 4H; c3–4),
3.65 (m, 1H; pr3), 2.01 (m, 2H; pr5), 1.89 (m, 2H; pr6), 1.66 (m, 2H;
pr4), 1.27 ppm (s, 27H; st5); ES-MS: m/z 1374.7122 (calcd 1374.7048 for
[C93H91N5O6+H+]).
Synthesis of mono-stoppered and bromo-ended phenanthroline fragment
12: Phenanthroline compound 11 (550 mg, 1.29 mmol), cesium carbonate
(840 mg, 2.58 mmol), and stopper with iodo-ended chain
8 (1.93 g,
2.58 mmol) were mixed in dry DMF (150 mL) and stirred at 508C for
5 h. More stopper with iodo-ended chain 8 (960 mg, 0.65 mmol) was
added and the reaction mixture stirred at 508C overnight. The solvent
was removed and the residue was taken up with CH2Cl2/H2O. The organ-
ic phase was separated and the aqueous phase extracted twice with
CH2Cl2. The solvent was removed and the residue purified by chromatog-
raphy on silica gel by using CH2Cl2/MeOH (0.5%) as the eluent to give
the title compound 12 (yellowish glassy solid, 620 mg, 46%). 1H NMR
(300 MHz, CD2Cl2, 258C, TMS): d=8.39 (d, 2H; J=8.7 Hz), 8.35 (d, 1H;
J=8.1 Hz), 8.34 (d, 2H; J=8.7 Hz), 8.29 (d, 1H; J=8.4 Hz), 8.13 (d, 1H;
J=8.4 Hz), 8.10 (d, 1H; J=8.4 Hz), 7.82 (d, 1H; J=8.7 Hz), 7.79 (d, 1H;
J=8.7 Hz), 7.74 (d, 2H; J=8.7 Hz), 7.25 (d, 6H; J=8.8 Hz), 7.14 (d, 6H;
J=8.8 Hz), 7.13 (d, 4H; J=9.0 Hz), 6.78 (d, 2H; J=9.0 Hz), 4.24 (dd,
2H; J=4.6, 6.0 Hz), 4.09 (dd, 2H; J=4.6, 6.0 Hz), 3.90 (dd, 2H; J=3.3,
4.8 Hz), 3.82 (dd, 2H; J=3.4, 4.9 Hz), 3.73 (s, 4H), 1.28 ppm (s, 27H);
MALDI-MS: m/z 1047.375 (calcd 1047.450 for [C67H69BrN2O4+H+]).
Synthesis of OH-ended two-station thread 18: OTHP-ended two stations
thread 17 (340 mg, 0.247 mmol) was dissolved in CH2Cl2 (50 mL) and
methanol (50 mL) in the presence of a catalytic amount of a 37% solu-
tion of HCl (3 drops). The mixture was heated to reflux for 4 h. The sol-
vent was removed and the product was dispersed in distilled water
(100 mL) and CH2Cl2 (200 mL). The aqueous layer was neutralized with
an aqueous solution of NH3 (37%). The organic layer was then decanted
and the aqueous layer was extracted four times with more CH2Cl2. The
combined organic phases were washed with distilled water. The solvent
was evaporated and the crude product purified by chromatography on
aluminum oxide by using CH2Cl2/MeOH (1%) as the eluent to give the
title compound 18 (yellow glassy solid, 251 mg, 79%). ES-MS: m/z
1290.6537 (calcd 1290.6467 for [C88H83N5O5+H+]).
Synthesis of mono-stoppered and boronic ester-ended phenanthroline
fragment 13: Brominated phenanthroline fragment 12 (660 mg,
0.63 mmol), bis(neopentyl glycolato)diboron (157 mg, 0.70 mmol), potas-
sium acetate (186 mg, 1.90 mmol), and [PdACTHNUTRGNEG(NU dppf)Cl2] (16 mg, 0.02 mmol)
were dissolved in dry dioxane. The mixture was stirred under argon at
808C overnight. After the solution was cooled down at room tempera-
ture, water (50 mL) and CH2Cl2 (100 mL) were added. The organic layer
was then decanted and the aqueous layer was extracted two times with
CH2Cl2. The combined organic layer was dried over Na2SO4, filtered, and
evaporated. The title product obtained was used without further purifica-
tion (dark brown solid, 681 mg, 100%). 1H NMR (300 MHz, CD2Cl2,
258C, TMS): d=8.43 (d, 2H; J=8.4 Hz), 8.40 (d, 2H; J=8.9 Hz), 8.34
(d, 1H; J=8.4 Hz), 8.29 (d, 1H; J=8.5 Hz), 8.19 (d, 1H; J=8.5 Hz), 8.10
(d, 1H; J=8.5 Hz), 8.00 (d, 2H; J=8.4 Hz), 7.80 (s, 2H), 7.26 (d, 2H;
J=8.8 Hz), 7.24 (d, 6H; J=8.8 Hz), 7.14 (d, 6H; J=8.8 Hz), 7.12 (d, 2H;
J=9.0 Hz), 4.24 (m, 2H), 4.09 (m, 2H), 3.89 (m, 2H), 3.82 (m, 2H), 3.82
(s, 4H), 3.74 (s, 4H), 1.28 (s, 27H), 1.05 ppm (s, 6H).
Synthesis of two-station copper-based [2]rotaxane with mb-39 macrocycle
+
14
(via 194+): A solution of [Cu
E
G
degassed MeCN (10 mL) was transferred by a cannula to a stirred solu-
tion of macrocycle mb-39 3 (54.3 mg, 0.070 mmol) in CH2Cl2 (5 mL)
under argon, and the resulting orange solution was stirred at room tem-
perature for 30 min. This mixture was then transferred to a degassed so-
lution of OH-ended two-station thread 18 (90.1 mg, 0.070 mmol) in
CH2Cl2 (10 mL) by a cannula, resulting in the immediate formation of a
brown-red solution, which was stirred under argon at room temperature
overnight. Solvent was evaporated to give the pseudo-rotaxane [194+]-
Synthesis of 5-bromo-5’’-[4-(OTHP)phenyl]-2,2’:6’-2’’-terpyridine 16:
5,5’’-Dibromo-2,2’:6’-2’’-terpyridine 14 (800 mg, 2.05 mmol), boronic acid
15 (455 mg, 2.05 mmol), and Na2CO3 (2.16 g, 20.4 mmol) were dissolved
in toluene (120 mL), water (40 mL), and ethanol (20 mL). The solution
AHCTUNGTRENNUNG
[PF6ꢀ] (brown-red solid). It was then dissolved in dry and degassed DMF
(8 mL) with Cs2CO3 (90 mg, 0.276 mmol), stopper with iodo-ended chain
8 (155 mg, 0.205 mmol), and sodium ascorbate (3 mg, 0.015 mmol). This
mixture was stirred under argon at 508C for 20 h. DMF was evaporated
and the resulting crude product taken up in CH2Cl2 and washed with
water. After evaporation of the solvent and three successive column
was degassed three times, [PdACHTNUGTRENUNG(PPh3)4] (120 mg, 0.1 mmol) was added
under an argon stream and the mixture was degassed three times again.
The solution was heated at 908C for 2 h. The organic layer was then dec-
anted and the aqueous layer was extracted two times with CH2Cl2. The
combined organic layer was washed with water and evaporated. The
crude product was purified by chromatography on aluminum oxide by
using pentane/ethyl acetate (2%) as the eluent to give the title com-
chromatographies on alumina (CH2Cl2 containing 1% MeOH and 1%
+
MeCN) the title product [14
]
[PF6ꢀ] was obtained (brown-red solid,
65 mg, 32%). 1H NMR (500 MHz, CD2Cl2, 258C, TMS): d=8.93 (d, 1H;
J=2.0 Hz, tp9), 8.69 (d, 1H; J=8.3 Hz, tp3), 8.62 (d, 1H; J=8.0 Hz,
tp7), 8.54 (d, 1H; J=7.0 Hz, tp6), 8.54 (s, 2H; bi2), 8.49 (s, 2H; bi1), 8.48
(d, 1H; J=8.7 Hz, tp4), 8.37 (d, 1H; J=2.0 Hz, tp1), 8.07 (dd, 1H; J=
8.3, 2.3 Hz, tp8), 8.01 (t, 1H; J=7.9 Hz, tp5), 7.96 (d, 1H; J=8.3 Hz,
ph2), 7.95 (d, 2H; J=7.8 Hz, bi3), 7.93 (d, 1H; J=8.1 Hz, ph5), 7.84 (d,
1H; J=8.1 Hz, ph6), 7.83 (t, 2H; J=8.2 Hz, bi4), 7.80 (d, 1H; J=8.4 Hz,
ph1), 7.65 (d, 2H; J=8.7 Hz, sp5), 7.64 (d, 2H; J=8.2 Hz, sp3), 7.57 (dd,
2H; J=6.3, 0.7 Hz, bi5), 7.49 (dd, 1H; J=7.8, 2.2 Hz, tp2), 7.47 (d, 2H;
J=8.6 Hz, sp2), 7.40 (d, 4H; J=8.9 Hz, mc6), 7.30 (d, 1H; J=8.9 Hz,
ph3), 7.25 (d, 6H; J=8.8 Hz, st9), 7.23 (d, 1H; J=8.4 Hz, ph4), 7.19 (d,
6H; J=8.8 Hz, st4), 7.15 (d, 6H; J=8.3 Hz, st8), 7.14 (d, 4H; J=9.0 Hz,
bi6), 7.13 (d, 2H; J=9.0 Hz, st7), 7.10 (d, 2H; J=8.7 Hz, st2), 7.08 (d,
6H; J=8.8 Hz, st3), 7.07 (d, 2H; J=8.8 Hz, sp6), 6.99 (d, 2H; J=8.2 Hz,
sp4), 6.84 (d, 4H; J=8.7 Hz, bi7), 6.79 (d, 4H; J=8.8 Hz, mc5), 6.78 (d,
2H; J=9.0 Hz, st6), 6.72 (d, 2H; J=9.0 Hz, st1), 6.19 (d, 2H; J=8.7 Hz,
1
pound 16 (white solid, 386 mg, 38%). H NMR (300 MHz, CD2Cl2, 258C,
TMS): d=8.91 (dd, 1H; J=2.4, 0.8 Hz), 8.75 (dd, 1H; J=2.4, 0.7 Hz),
8.64 (dd, 1H; J=8.3, 0.8 Hz), 8.57 (dd, 1H; J=8.5, 0.7 Hz), 8.50 (dd, 1H;
J=7.9, 1.1 Hz), 8.42 (dd, 1H; J=7.9, 1.1 Hz), 8.04 (dd, 1H; J=8.4,
2.4 Hz), 8.01 (dd, 1H; J=8.6, 2.4 Hz), 7.97 (t, 1H; J=7.9 Hz), 7.63 (d,
2H; J=8.9 Hz), 7.17 (d, 2H; J=8.9 Hz), 5.48 (t, 1H; J=3.4 Hz), 3.90 (m,
1H), 3.61 (m, 1H), 2.00 (m, 2H), 1.87 (m, 2H), 1.67 ppm (m, 2H); ES-
MS: m/z 488.0992 (calcd 488.0968 for [C26H22BrN3O2+H+]).
Synthesis of OTHP-ended two stations thread 17: Boronic ester phenan-
throline fragment 13 (340 mg, 0.315 mmol), brominated terpyridine 16
(130 mg, 0.266 mmol), and Na2CO3 (282 mg, 2.66 mmol) were dissolved
in toluene (45 mL), water (15 mL), and ethanol (8 mL). The solution was
degassed three times, [Pd
ACHTUNGTERN(NUNG PPh3)4] (16 mg, 0.013 mmol) was added under
an argon stream and the mixture was degassed three times again. The so-
4132
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Chem. Eur. J. 2009, 15, 4124 – 4134

A Fast-Moving Copper-Based Molecular Shuttle
FULL PAPER
sp1), 4.19 (t, 2H; J=4.7 Hz, c12), 4.14 (t, 4H; J=6.0 Hz, mc1), 4.10 (t,
2H; J=4.7 Hz, c1), 4.08 (t, 2H; J=4.7 Hz, c7), 3.87 (t, 2H; J=4.7 Hz,
c11), 3.83 (t, 2H; J=4.8 Hz, c2), 3.81 (t, 2H; J=4.8 Hz, c8), 3.79 (t, 4H;
J=6.1 Hz, mc4), 3.72 (s, 8H; c3-c4-c9-c10), 3.65 (t, 2H; J=4.8 Hz, c5),
3.58 (t, 2H; J=4.8 Hz, c6), 1.89–1.81 (m, 8H; mc2-mc3), 1.76 (s, 6H;
mc7-mc8), 1.29 (s, 27H; st10), 1.24 ppm (s, 27H; st5); MALDI-MS: m/z:
2749.004 (calcd 2749.344 for [C184H185CuN7O12]).
4.7 Hz, c7), 3.87 (t, 2H; J=4.7 Hz, c11), 3.84 (t, 2H; J=4.7 Hz, c2), 3.82
(t, 2H; J=4.7 Hz, c8), 3.73 (t, 4H; J=4.8 Hz, m9), 3.72 (bs, 12H; c3-c4-
c9-c10 m10), 3.69 (t, 2H; J=4.6 Hz, c6), 3.63 (t, 2H; J=4.9 Hz, c5), 3.62
(t, 4H; J=5.5 Hz, m8), 3.59 (t, 4H; J=5.3 Hz, m6), 3.51 (t, 4H; J=
5.3 Hz, m7), 1.29 (s, 27H; st10), 1.25 ppm (s, 27H; st5); MALDI-MS: m/
z: 2539.181 (calcd 2539.222 for [C165H171CuN7O14]).
Synthesis of two-station copper-based [2]rotaxane with m-30 macrocycle
+
24
(via 204+): A solution of [Cu
E
G
Acknowledgements
degassed MeCN (10 mL) was transferred by a cannula to a stirred solu-
tion of macrocycle m-30 4 (26.3 mg, 0.046 mmol) in CH2Cl2 (10 mL)
under argon, and the resulting orange solution was stirred at room tem-
perature for 15 min. This mixture was then transferred to a degassed so-
lution of OH-ended two-station thread 18 (60 mg, 0.046 mmol) in CH2Cl2
(10 mL) by a cannula, resulting in the immediate formation of a brown-
red solution, which was stirred under argon at room temperature over-
night. Solvent was evaporated to give a brown-red solid. This solid was
dissolved in dry and degassed DMF (10 mL) with Cs2CO3 (60 mg,
184 mmol), stopper with iodo-ended chain 8 (103 mg, 138 mmol), and
sodium ascorbate (2 mg, 0.010 mmol). This mixture was stirred under
argon at 558C for 20 h. DMF was evaporated and the resulting crude
product taken up in CH2Cl2 and washed with water. After evaporation of
the solvent and four successive column chromatographies on alumina
(CH2Cl2 containing 1% MeOH and 1% MeCN) the title product [24+]-
We are grateful to the CNRS and the Rꢀgion Alsace for fellowships to
F.D. and J.L.
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Chem. Eur. J. 2009, 15, 4124 – 4134
ꢁ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: December 1, 2008
Published online: February 20, 2009
4134
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Chem. Eur. J. 2009, 15, 4124 – 4134