Formation of copper(I)-templated [2]rotaxanes using "click" methodology: Influence of the base, the thread and the catalyst

Article abstract of DOI:10.1007/s10847-011-9986-6

Three new copper(I)-assembled [2]rotaxanes incorporating the same macrocycle and different axes containing a bipy, a phen or a terpy have been synthesized thanks to CuAAC reaction for attaching the stoppers. The influence of the nature of the base used for the stoppering reaction was investigated on the formation of the bipy-containing rotaxane. The yield of the [2]rotaxane synthesis was increased when using a phen as a coordinating unit in the thread with [Cu(CH₃CN)₄](PF₆) as catalyst. The strong influence of the nature of the catalyst was clearly evidenced for the formation of the terpy rotaxane, increasing the yield of the stoppering reaction from 0 to 95% by just substituting the Cu(I) catalyst. Finally, the best conditions found for our systems are the use of Na₂CO₃ as a base and Cu(tren')Br as a catalyst.

Full text of DOI:10.1007/s10847-011-9986-6

J Incl Phenom Macrocycl Chem (2011) 71:507–515
DOI 10.1007/s10847-011-9986-6
ORIGINAL ARTICLE
Formation of copper(I)-templated [2]rotaxanes using ‘‘click’’
methodology: influence of the base, the thread and the catalyst
•
Fabien Durola Stephanie Durot Valerie Heitz
•
•
´
Antoine Joosten Jean-Pierre Sauvage
´
•
•
Yann Trolez
Received: 4 May 2011 / Accepted: 6 May 2011 / Published online: 28 May 2011
Ó Springer Science+Business Media B.V. 2011
Abstract Three new copper(I)-assembled [2]rotaxanes
incorporating the same macrocycle and different axes
containing a bipy, a phen or a terpy have been synthesized
thanks to CuAAC reaction for attaching the stoppers. The
influence of the nature of the base used for the stoppering
reaction was investigated on the formation of the bipy-
containing rotaxane. The yield of the [2]rotaxane synthesis
was increased when using a phen as a coordinating unit in
the thread with [Cu(CH3CN)4](PF6) as catalyst. The strong
influence of the nature of the catalyst was clearly evidenced
for the formation of the terpy rotaxane, increasing the yield
of the stoppering reaction from 0 to 95% by just substi-
tuting the Cu(I) catalyst. Finally, the best conditions found
for our systems are the use of Na2CO3 as a base and
Cu(tren0)Br as a catalyst.
Introduction
[2]rotaxanes are nowadays considered as very accessible
compounds, contrary to what was thought until the 80s
[1–4]. One of the reasons for this change was the excellent
yields obtained for preparing the rotaxane precursors by
threading reactions [5–17]. Another important improve-
ment was the yield increase of the stoppering reactions.
However, although templated strategies are nowadays well
documented, affording the desired rotaxanes or their pre-
cursors in high yields, substantial efforts are still needed to
increase the yield of the stoppering reactions [18–23]. In
the course of the last few years, ‘‘click reaction’’, which
implies azides and alkynes to give 1,2,3-triazoles in a
controlled fashion, [24, 25] has been extensively used and
sometimes considered as the ‘‘holy grail’’ of stoppering
reactions thanks to its generally good yields and high tol-
erance to many functions [26–28]. Indeed, many labora-
tories, including ours, currently use copper-catalyzed
azide-alkyne cycloaddition (CuAAC) with much success
for the elaboration of rotaxanes [29–32]. However, in most
cases, the CuAAC has not really been studied methodo-
logically in order to optimize the conditions and obtain the
highest possible yields. In particular, there is a lack of
information concerning the elaboration of rotaxane from
Cu(I)-complexes, this family of compounds being partic-
ularly important in relation to molecular machine proto-
types [33, 34].
Keywords Rotaxane ꢀ Copper(I) ꢀ Click chemistry ꢀ
Phenanthroline ꢀ Bipyridine ꢀ Terpyridine
Electronic supplementary material The online version of this
article (doi:10.1007/s10847-011-9986-6) contains supplementary
material, which is available to authorized users.
F. Durola ꢀ S. Durot (&) ꢀ V. Heitz ꢀ A. Joosten ꢀ J.-P. Sauvage
(&) ꢀ Y. Trolez
´
Laboratoire de Chimie Organo-Minerale, Institut de Chimie de
Strasbourg, UMR 7177 CNRS, Universite de Strasbourg, 4 rue
We would now like to report the synthesis of several
[2]rotaxanes whose axles contain different ligands, namely
2,20-bipyridine (bipy), 1,10-phenanthroline (phen) and
2,20,60,200terpyridine (terpy) by using the threading-stop-
pering strategy, as described in Scheme 1. Several reaction
conditions for CuAAC stoppering reactions were
investigated.
´
Blaise Pascal, 67070 Strasbourg Cedex, France
e-mail: sdurot@unistra.fr
J.-P. Sauvage
e-mail: jpsauvage@unistra.fr
Y. Trolez
e-mail: yanntrolez@chimie.u-strasbg.fr
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Ligands 1 and 2 were synthesized according to published
procedures [35, 36]. As for preparing other copper(I)-
complexed [2]rotaxanes, the synthesis sequence started
with a threading reaction. Threading bipy 1 into the
30-membered ring
2
afforded the corresponding
[2]pseudorotaxane 31. Subsequently, this compound was
directly engaged in a stoppering reaction without any
purification and characterization. The stoppering reaction
was performed with [Cu(CH3CN)4](PF6) as catalyst in the
presence of a base (0.5 equivalent). Various bases were
tested: lutidine, sodium carbonate, and none. The stopper 4,
bearing an azide function, [37] was added in slight excess.
The resulting copper(I)-complexed [2]rotaxane 51 was
then purified by silica chromatography.
Scheme 1 Principle of formation of a [2]rotaxane by the threading
and stoppering strategy; the small spheres represent Cu(I), and the big
spheres represent stoppers
In order to test the influence of the base used during the
stoppering reaction, we synthesized a [2]rotaxane con-
taining a non-hindered bipy on the axle by changing the
base. The use of a bipy rather than a phen is justified by the
fact that bipy is a less powerful chelate than phen, and
therefore the intermediate [2]pseudorotaxane should be
more sensitive to the basic conditions of stoppering
reaction.
The nature of the base strongly influenced the reaction
yield. Whereas 2,6-lutidine allowed to get the target
[2]rotaxane in moderate yields (30%), the use of a base
such as sodium carbonate led to compound 51 in a satis-
fying yield of 61%. Cu(I) complexes are sensitive to bases,
which could explain the differences observed. Indeed,
whereas lutidine is perfectly soluble in the mixture of
solvents used for the stoppering reaction (CH2Cl2/CH3CN:
3/1), sodium carbonate is hardly soluble. Consequently,
whereas the number of equivalents of base added in the
As indicated on Fig. 1, [2]rotaxane 51 was prepared in a
few steps from relatively easily accessible compounds.
Fig. 1 Synthesis of copper(I)-
complexed [2]rotaxane 51
-
+ PF6
O
O
O
O
N
N
O
O
O
[Cu(CH3CN)4]PF6
CH2Cl2 / CH3CN
N
+
N
N
N
Cu
O
O
N
N
O
O
O
3+
2
1
[Cu(CH3CN)4]PF6
Base
O
N3
4
CH2Cl2 / CH3CN
-
+ PF6
O
O
O
O
O
O
N
N
N
N
N
N
O
O
N
N
Cu
N
N
5+
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J Incl Phenom Macrocycl Chem (2011) 71:507–515
509
mixture was the same, the real quantity of base present in
the layer containing the Cu(I) complex was certainly lower
in the case of sodium carbonate, making the medium less
aggressive towards the copper complexes present in the
solution. This solubility difference could explain why the
yield increased when sodium carbonate was used. This
yield is similar to that reported for a similar bipy-incor-
porating [2]rotaxane, synthesized from a diazide axle and a
propargyl-bearing stopper [31].
temperature (except with activated acetylenes, [38] which
was not the case here) and the mixture was reacted at room
temperature. We suggest that partial decoordination of the
thread, which could thus play the role of the catalytic base,
could explain the formation of compound 51 in such a
yield. This partial decoordination would be more limited
than in the presence of a soluble base like 2,6-lutidine, as
suggested by the comparison of the yields.
In order to compare the influence of the coordinating
moiety belonging to the axle, we synthesized a [2]rotaxane
incorporating a 2,9-diphenyl-1,10-phenanthroline unit in
the axle instead of the bipy. The compounds used for the
synthesis of the corresponding [2]rotaxane and the final
rotaxane itself are represented in Fig. 2. We have already
reported the synthesis of a phen bearing azide functions
[39]. But its synthesis was tedious and involved low-
An unexpected result was obtained when the stoppering
reaction was performed without any base. Indeed, whereas
we did not expect to form any rotaxane or only trace
amounts, compound 51 was formed in 45% yield, which
was even more than when lutidine was used. The product
could not originate from the non-catalyzed Huisgen
cycloaddition because this reaction occurs only at high
Fig. 2 Synthesis of [2]rotaxane
101
Br
1)
Br
K2CO3, DMF
50 C
N
N
N
N
2) NaN3, DMF
74%
O
O
HO
OH
N3
N3
6
7
[Cu(CH3CN)4]PF6, 2
CH2Cl2 / CH3CN
-
O
O
+ PF6
O
O
O
O
N
N
Cu
N
N
O
O
N3
N3
O
8+
72%
[Cu(CH3CN)4]PF6
Na2CO3, 9
CH3CN / CH2Cl2
9
-
O
O
+ PF6
O
O
O
O
N
N
Cu
N
N
O
O
O
O
N
N
N
N
N
N
10+
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Fig. 3 Synthesis of a terpy-
containing [2]rotaxane 13 by
CuAAC, as well as the related
dumbbell 14
+ PF6
O
O
O
O
N
[Cu(CH3CN)4]PF6
quantitative
N
O
O
N
N3
+ 2
N
N3
N
N
Cu
N3
N3
N
N
11
12+
1) 9, [Cu(tren’)]Br
Na2CO3, sodium ascorbate
95%
2) KCN
N
O
N
N
N
N
N
N
N
N
N
OH
O
O
N
O
O
O
O
O
13
11 + 9
[Cu(CH3CN)4]PF6
Na2CO3, sodium ascorbate
84%
N
N
N
N
N
N
N
N
N
O
O
14
yielding steps. Therefore, a more accessible phen unit
incorporating two azide functions was designed. Dialky-
lation of the 2,9-di(p-hydroxy-phenyl)-1,10-phenanthroline
6 in presence of dibromoethane, followed by substitution of
the corresponding bromides by sodium azide in DMF led to
diazide 7 with an overall yield of 74% (Fig. 2). [2]pseud-
orotaxane 81 was then obtained quantitatively by mixing
an equimolar mixture of diazide 7, macrocycle 2 and
[Cu(CH3CN)4](PF6) in CH2Cl2/CH3CN (3/1). This
[2]pseudorotaxane 81 was subsequently stoppered in
presence of propargyl stopper 9 [31], Na2CO3 and
[Cu(CH3CN)4](PF6) to give the desired [2]rotaxane 101
with a good yield of 72%. On one hand, this better yield, in
comparison with the one obtained with the bipy moiety,
could be explained by a more stable pseudorotaxane 81
due to 2,9-substituents of phen and a longer axle. This
observation stresses the importance of the chelating moiety
in the axle: the more stable the intermediate cop-
per(I) pseudorotaxane, the less unthreading during the
synthesis of rotaxanes by CuAAC and the higher the yields.
On the other hand, this yield is in good agreement with the
yield of a previously published [2]rotaxane incorporating
the same macrocycle and a similar axis, using the same
conditions [39].
We also attempted to prepare a [2]rotaxane incorporat-
ing a terpy axle. Only few examples of reactions of click
chemistry on terpyridinic compounds have been reported in
the literature [40–45]. The threading reaction between the
copper(I) complex of ring 2 and the terpy thread 11 [44,
45] led quantitatively to the expected [2]pseudorotaxane
121 (Fig. 3) as confirmed by a proton NMR study (Fig. 4).
All the signals were assigned (see experimental part and
supplementary materials), and the phenyl protons labeled o
and m showed a strong upfield shift, resulting from their
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511
1
Fig. 4 Partial H NMR spectra
of a terpy-containing dumbbell
14, the related [2]rotaxane 13,
the macrocycle 2, the
copper(I) pseudorotaxane 121
and the terpy precursor 11 in
CDCl3 (except for 121 in
CD2Cl2)
presence in the anisotropy cone of the terpy axle. Similar
upfield shifts were also observed for the 6 and 600 protons of
the terpy moiety.
chromatography. This treatment afforded the free [2]ro-
taxane 13 in 95% yield. This excellent yield emphasized
the efficiency of [Cu(tren0)]Br as a catalyst, since it was the
best yield of the double click stoppering reactions among
the various [2]rotaxanes described in the present report.
The ES-MS and the 1H NMR spectra were in accordance
with the postulated structure of 13. The ES-MS spectrum
showed two peaks, one at m/z 1996.25 corresponding to
(13 ? H?) (calcd 1996.09), and the other at m/z 998.65
corresponding to ([13 ? 2H]2?/2) (calcd 998.55). The free
dumbbell of rotaxane 14 has also been synthesized in 84%
yield thanks to click chemistry by mixing compounds 9 and
11 in the presence of Cu(I). Thus, the 1H NMR spectrum of
this dumbbell-shaped molecule could be compared to that of
the rotaxane as discussed below. It can be noticed that this
reaction occurred very efficiently with Cu(CH3CN)4PF6
whereas [Cu(tren0)]Br was detrimental to the formation of
rotaxane 13. It is likely that Cu(CH3CN)4PF6 as a catalyst
participates to the coordination of the terpy incorporated in
the rotaxane and thus interferes too much with pseudoro-
taxane 121 to play its role of catalyst without destroying this
precursor 121. On the contrary, [Cu(tren0)]Br is strongly
protected and too hindered to interfere with this inter-
mediate.
The first attempt to synthesize the [2]rotaxane 13
(Fig. 3) by click chemistry was made using the following
optimized ‘‘standard’’ conditions: a CH2Cl2/CH3CN (2/1)
mixture with Na2CO3 as a base and 0.5 equivalents of
[Cu(CH3CN)4](PF6) for 5 days. No copper(I) [2]rotaxane
could be isolated. By comparison with the results con-
cerning the bipy-based [2]rotaxane 51 and the phen analog
101, we concluded that the presence of terpy was detri-
mental to the formation of the desired stoppered complex,
probably because the copper(I) centers supposed to act as
catalysts were not coordinated to any protective ligand. It
thus appeared necessary to use an ancillary ligand, able to
partially complex the catalytic copper(I) center and protect
it towards potentially coordinating fragments of the com-
pounds to be ‘‘clicked’’.
We recently reported the efficiency of such a protected
catalyst, [Cu(tren0)]Br, first described and used by Vincent
et al., [46, 47] in the synthesis of linear multi-rotaxanes,
incorporating terpy [44, 45]. Consequently, we mixed the
[2]pseudorotaxane 121 (Fig. 3) with the acetylenic stopper
9 (three equivalents), [Cu(tren0)]Br (0.25 equivalent),
sodium carbonate as a base (0.5 equivalent), and sodium
ascorbate (1.3 equivalent) as a reductant. After 3 days
under argon, the NMR spectrum of the crude reaction
mixture showed total conversion of azide functions to
1,2,3-triazoles. In order to confirm the threaded nature of
the non-isolated corresponding copper(I) [2]rotaxane and
to facilitate purification, the mixture was demetalated with
an excess of KCN and submitted to purification by alumina
The 1H NMR spectrum of rotaxane 13 (Fig. 4) was
significantly different from the superposition of the spectra
of both the macrocycle 2 and the symmetrical terpy
dumbbell compound 14 (Fig. 3). This confirmed that
compound 13 was a real rotaxane and that the stoppers
prevented unthreading of the ring. The protons labeled o,
m, 6 and 600 were again upfield shifted, but less than in the
presence of copper(I) like in the [2]pseudorotaxane 121.
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3
Conclusion
4.01 (t, J = 5.7 Hz, 4H, H-7), 4.80–4.60 (m, 20H, H-a,
3
H-b, H-c, H-d, H-e), 2.46 (q, J = 6.1 Hz, 4H, H-6), 1.29
To conclude, CuAAC was investigated in detail in order to
optimize the yield of stoppering for the elaboration of
copper(I)-complexed rotaxanes or their metal-free forms.
We applied this reaction to the synthesis of three [2]rotax-
anes containing each time the same macrocycle but a dif-
ferent axis. We could thus obtain rotaxanes encompassing a
bipy, a phen or a terpy in the axis. Particularly noteworthy is
the yield obtained for the terpy-containing [2]rotaxane
which was dramatically improved by using the recently
reported catalyst [46, 47] containing a copper(I) center
protected with a tripodal chelate. As a consequence, this
methodology paves the way to the elaboration of more
complex structures, such as multi-rotaxanes with different
kinds of chelating unit, in relation to new molecular
machines incorporating several coordinating units in their
axis or in the threaded rings.
(s, 54H, H-12) ppm. MS (ES) m/z (%) = 2009.101 (100)
[M–PF6]? (calcd: 2009.019 for [C128H140CuN10O8]?).
Diazidophenanthroline 7 To a solution of 2,9-di(p-
phenol)-1,10-phenanthroline 6 (500 mg, 1.372 mmol) in
DMF (50 mL) was added successively 1,2-dibromoethane
(6 mL, 68.7 mmol) and K2CO3 (3.8 g, 27.494 mmol) and
the solution was stirred 48 h at 50 °C. DMF was removed
under vacuum and the residue taking up in H2O–CH2Cl2.
The aqueous layer was extracted with CH2Cl2
(3 9 20 mL), the organic phases were combined, dried
over MgSO4, filtered and concentrated under vacuum. To
the crude material in DMF was added NaN3 (1.79 g,
27.44 mmol) and the solution was stirred overnight at
100 °C. DMF was removed under vacuum and the residue
taking up in H2O–CH2Cl2. The aqueous layer was extrac-
ted with CH2Cl2 (3 9 20 mL), the organic phases were
combined, dried over MgSO4, filtered and concentrated
under vacuum. The residue was purified by flash column
chromatography on silica gel eluting with CH2Cl2 to give
Experimental part
the desired product as
1.017 mmol, 74% yield).
a white powder (512 mg,
General procedure for the synthesis of [2]rotaxane 51
1H RMN (300 MHz, CD2Cl2) d = 8.44 (d, 3J =
8.8 Hz, 4H, H-o), 8.31 (d, J = 8.5 Hz, 2H, H-4), 8.12 (d,
3
Threading procedure Macrocycle 2 (143.2 mg, 250 lmol)
was dissolved in 5 mL of distilled and degassed dichloro-
methane. 5 mL of a solution of [Cu(CH3CN)4]PF6
(94.6 mg, 250 lmol) in distilled and degassed acetonitrile
were subsequently added and the resulting solution was
stirred for 15 min. Then, 5 mL of a solution of bipy 1
(51.7 mg, 250 lmol) were added to the previous solution
and the mixture was stirred overnight. The solvents were
evaporated, and the resulting precipitate was used as-is for
the next step.
3J = 8.5 Hz, 2H, H-3), 7.79 (s, 2H, H-5), 7.16 (d,
3J = 8.8 Hz, 4H, H-m), 4.28 (t, J = 5.1 Hz, 4H, H-a),
3
3
3.67 (t, J = 5.1 Hz, 4H, H-b) ppm. 13C RMN (75 MHz,
CD2Cl2) d = 49.9, 66.8, 114.5, 118.8, 125.3, 127.3, 128.5,
132.4, 136.4, 145.7, 155.4, 159.2 ppm. MS (ES) m/z
(%) = 1027.36 (100) [2M ? Na]? (calcd: 1027.36 for
[(C28H22N8O2)2Na]?).
[2]Rotaxane 101 Macrocycle 2 (14.3 mg, 25.2 lmol)
and [Cu(CH3CN)4]PF6 (9.4 mg, 25.2 lmol) were dissolved
in 2 mL of degassed CH2Cl2 and 1 mL of degassed
CH3CN. To this solution was subsequently added via
canula a solution of diazide 7 (14.7 mg, 25.2 lmol) in
2 mL of degassed CH2Cl2. The resulting solution was
stirred 1 h, and the solvents were then evaporated to give,
without any further purification, the desired [2]pseudoro-
Stoppering procedure A third of the previous Cu(I)-
complex (81 mg, 83 lmol), Cu(CH3CN)4PF6 (16 mg,
43 lmol) and 0.5 equivalent of base were dissolved in
3 mL of degassed dichloromethane and 1 mL of acetoni-
trile. The mixture was stirred at room temperature under
argon for 5 days. Then, the solvents were evaporated and
the resulting residue was purified by silica chromatography
(eluent: CH2Cl2/MeOH/CH3CN: 98/1/1) to afford the
desired [2]rotaxane 51.
taxane 81 in quantitative yield according to the H NMR
1
spectrum. To a solution of the corresponding [2]pseud-
orotaxane 81, Na2CO3 (1.4 mg, 12.6 lmol), sodium
ascorbate (10 mg, 50.4 lmol) and Cu(CH3CN)4PF6
(4.7 mg, 12.6 lmol) in a mixture of dichloromethane
(1 mL) and acetonitrile (1 mL) was added a solution of the
stopper 9 (41 mg, 75.6 lmol) in dichloromethane (2 mL)
and the resulting mixture was stirred overnight and con-
centrated under vacuum. The residue was purified by flash
column chromatography on silica gel eluting with a mix-
ture of CH2Cl2 and MeOH (99.5/0.5–97/3) to give the
desired [2]rotaxane 101 as a dark red solid (40.9 mg,
18.4 lmol, 72% yield).
1H-NMR (300 MHz, CDCl3, 25 °C): d = 8.59 (d,
3J = 8.2 Hz, 2H, H-m4), 8.44 (d, J = 1.4 Hz, 2H, H-3),
4
8.37 (dd, 3J = 8.4 Hz, 4J = 2.0 Hz, 2H, H-2), 8.30 (d,
3J = 8.4 Hz, 2H, H-1), 8.10 (s, 2H, H-m3), 8.09 (s, 2H,
H-4), 8.03 (d, 3J = 8.4 Hz, 2H, H-m5), 7.45 (d,
3J = 8.6 Hz, 4H, H-o), 7.24 (d, J = 8.6 Hz, 12H, H-11),
3
7.18 (d, 3J = 8.7 Hz, 4H, H-9), 7.14 (d, 3J = 8.6 Hz, 12H,
H-10), 6.80 (d, 3J = 8.9 Hz, 4H, H-8), 6.17 (d,
3J = 8.8 Hz, 4H, H-m), 4.66 (t, J = 6.8 Hz, 4H, H-5),
3
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J Incl Phenom Macrocycl Chem (2011) 71:507–515
513
3
7.85 (d, J = 8.4 Hz, 2H, H-m3), 7.67 (s, 2H, H-g), 7.43
1H RMN (300 MHz, CDCl3) d = 8.63 (d, 3J = 8.8 Hz,
4H, H-4), 8.32 (d, J = 8.4 Hz, 2H, H-m4), 8.25 (s, 2H,
3
4
(dd, 3J = 8.3 Hz, J = 1.6 Hz, 2H, H-4,400), 7.23 (d,
3
H-5), 7.86 (d, J = 8.4 Hz, 2H, H-3), 7.84 (s, 2H, H-m5),
3
3J = 8.6 Hz, 12H, H-b), 7.15 (d, J = 8.6 Hz, 12H, H-c),
3
3
7.13 (d, J = 8.9 Hz, 4H, H-d), 6.91 (d, J = 8.9 Hz, 4H,
3
7.83 (s, 2H, H-g), 7.76 (d, J = 8.3 Hz, 4H, H-m3), 7.46
3
H-e), 6.74 (d, J = 8.4 Hz, 4H, H-m), 5.43 (s, 4H, H-h),
(d, 3J = 8.6 Hz, 4H, H-o0), 7.27 (d, 3J = 8.6 Hz, 4H, H-o),
7.24 (d, 3J = 8.5 Hz, 12H, H-b), 7.20 (d, 3J = 8.9 Hz, 4H,
H-d), 7.15 (d, 3J = 8.5 Hz, 12H, H-c), 6.04 (d,
3
5.15 (s, 4H, H-f), 4.00 (t, J = 5.9 Hz, 4H, H-a), 3.60 (t,
3J = 5.9 Hz, 4H, H-b), 3.58 (s, 4H, H-e), 3.53 (s, 8H, H-c,
H-d), 1.28 (s, 54H, H-a) ppm. MS (ES) m/z (%) = 1996.25
(100) [M ? 1H]? (calcd: 1996.09 for [C131H140N11O8
H4]?), 998.65 (94) [M ? 2H]2? (calcd: 998.55 for [C131
H141N11O8H4]2?/2).
3
3J = 8.6 Hz, 4H, H-m0), 5.97 (d, J = 8.6 Hz, 4H, H-m),
3
5.30 (s, 4H, H-f), 4.65 (t, J = 4.7 Hz, 4H, H-h), 3.89 (t,
3J = 4.7 Hz, 4H, H-i), 3.83 (s, 4H, H-e), 3.69-3.75 (m, 4H,
H-d), 3.58-3.62 (m, 4H, H-c), 3.52-3.58 (m, 4H, H-b), 3.48
3
(t, J = 4.7 Hz, 4H, H-a), 1.28 (s, 54 H, H-a) ppm. MS
Terpy dumbbell 14 Di(azidomethyl)terpyridine 11
(0.040 g, 116 lmol) was dissolved in 750 lL of distilled
and degassed CH2Cl2 under argon. [Cu(CH3CN)4]PF6
(0.063 g, 170 lmol) dissolved in 350 lL of degassed
CH3CN was added under argon. The dark green solution
was agitated for 2 h. Then, stopper 9 (158 mg, 291 lmol)
was added under argon, as well as Na2CO3 (5.5 mg,
52.4 lmol) and sodium ascorbate (35 mg, 175 lmol). The
mixture was stirred for 18 h under argon. KCN (111 mg,
1.7 mmol) diluted in the minimum amount of distilled
water was then added and the mixture was stirred for 2 h
30 min. Then, 20 mL of distilled water were added and this
layer was extracted with CH2Cl2. The organic layer was
dried over Na2SO4, the solvent was then evaporated and
the resulting yellow residue was purified by alumina
chromatography (elution ether/ethylacetate) to give
140 mg (98 lmol) of pure 15 (84%).
(ES) m/z (%) = 2218.081 (100) [M–PF6]? (calcd:
2218.071 for [C142H148CuN10O10]?).
Diazido [2]pseudorotaxane 121 To a degassed solution
of macrocycle 2 (15.3 mg, 27.0 lmol) in dry CH2Cl2
(0.7 mL) was added a solution of [Cu(CH3CN)4]PF6
(10.2 mg, 27.0 lmol) in dry and degassed CH3CN
(0.3 mL) and it was stirred at room temperature during
15 min under inert atmosphere. A degassed solution of
di(azidomethyl)terpyridine 11 (9.5 mg, 27.6 lmol) in dry
CH2Cl2 (2.1 mL) was then added to this orange solution
via canula; the mixture turned immediately intensely dark
red and was reacted during 3 h. After evaporation of the
solvents, the crude [2]pseudorotaxane 121 (35 mg,
1
27.0 lmol) was checked by H NMR in CD2Cl2.
1H-NMR (300 MHz, CD2Cl2, 25 °C): d = 8.52 (d,
3J = 8.2 Hz, 2H, H-m4), 8.05 (m, 3H, H-30,40,50), 8.04 (s,
2H, H-m5), 7.96 (d, 3J = 8.2 Hz, 2H, H-m3), 7.89 (d,
3J = 8.1 Hz, 2H, H-3,300), 7.67 (s, 2H, H-6,600), 7.52 (d,
1H RMN (300 MHz, CDCl3, 25 °C): d (ppm) = 8.67 (d,
4J = 2.1 Hz, 2H, H-6,600), 8.55 (d, 3J = 8.2 Hz, 2H,
3
3
3J = 8.6 Hz, 4H, H-o), 7.42 (d, J = 8.1 Hz, 2H, H-4,400),
H-3,300), 8.44 (d, J = 7.7 Hz, 2H, H-30, H-50), 7.94 (t,
3
4
4.15 (s, 4H), 3.93–3.90 (m, 4H, H-a), 3.82–3.72 (m, 16H,
H-b, H-c, H-d, H-e).
3J = 7.9 Hz, 1H, H-40), 7.69 (dd, J = 8.2, J = 2.5 Hz,
3
2H, H-4,40), 7.59 (s, 2H, H-7), 7.20 (d, J = 8.8 Hz, 12H,
Demetalated [2]rotaxane 13 [2]pseudorotaxane 121
H-12), 7.07 (d, 3J = 9.0 Hz, 4H, H-10), 7.05 (d,
3
(35 mg, 27.0 lmol), acetylenic stopper
9
(44.2 mg,
3J = 8.8 Hz, 12H, H-11), 6.81 (d, 4H, H-9, J = 9.0 Hz),
5.61 (s, 4H, H-2), 5.16 (s, 4H, H-8), 1.26 (s, 54H, H-13) ppm.
81.4 lmol), Na2CO3 (1.6 mg, 15 lmol), [Cu(tren0)]Br
catalyst (12.5 mg, 6.9 lmol), sodium ascorbate (6.9 mg,
35 lmol) were introduced in 1.4 mL of distilled and
degassed CH2Cl2 and 0.7 mL of degassed anhydrous
CH3CN. The mixture was stirred for 3 days under argon.
KCN (31 mg, 476 lmol) diluted in the minimum amount of
distilled water was then added and the mixture was stirred
for 4 h. Then, 20 mL of distilled water were added and this
layer was extracted with CH2Cl2. The organic layer was
dried over Na2SO4, the solvent was then evaporated and the
resulting yellow residue was purified by alumina chroma-
tography. A gradient of elution (CH2Cl2/MeOH) gave
52 mg (25.8 lmol) of pure [2]rotaxane 13 (95%).
Acknowledgments We thank the Agence Nationale de la Recher-
che (ANR no. 07-Blan-0174, MOLPress) for its financial support as
well as the French Ministry of Research for a fellowship to YT.
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