[3]Rotaxanes and [3]pseudorotaxanes with a rigid two-bidentate chelate axle threaded through two coordinating rings

Article abstract of DOI:10.1039/b9nj00278b

New [3]rotaxanes and [3]pseudorotaxanes have been synthesised using the "gathering and threading" effect of copper(i). By using click chemistry as the "stoppering" reaction, a good yield of the [3]rotaxane was obtained, either as a dicopper complex or as

Full text of DOI:10.1039/b9nj00278b

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[3]Rotaxanes and [3]pseudorotaxanes with a rigid two-bidentate chelate
axle threaded through two coordinating ringsw
b
Jean-Paul Collin,a Jean-Pierre Sauvage,*a Yann Troleza and Kari Rissanenz
Received (in Montpellier, France) 22nd June 2009, Accepted 23rd July 2009
First published as an Advance Article on the web 19th August 2009
DOI: 10.1039/b9nj00278b
New [3]rotaxanes and [3]pseudorotaxanes have been synthesised using the ‘‘gathering and
threading’’ effect of copper(I). By using click chemistry as the ‘‘stoppering’’ reaction, a good yield
of the [3]rotaxane was obtained, either as a dicopper complex or as a metal-free compound
after demetallation. The axle contains a central rigid aromatic block incorporating two
bidentate chelates, and the threaded macrocycles are 30-membered rings. A model
dicopper(I) [3]pseudorotaxane whose axle was end-functionalised by triisopropylsilyl groups could
be crystallised and studied by X-ray diffraction. A particularly attractive structure was obtained
showing a ‘‘slanted’’ geometry for the two rings and the axle, the two 1,10-phenanthroline units
of the rings being almost parallel to one another but their respective mean planes being more
than 7 A apart.
effect was found that governs the success of pseudorotaxane
Introduction
formation. Using a molecular filament bearing relatively
Although catenanes and rotaxanes1 are nowadays relatively
voluminous end-groups, it was shown that the copper(I)-
accessible compounds, thanks to the template strategies
induced threading reaction leads quantitatively to the desired
introduced by various groups over the course of the last
[3]pseudorotaxane when the macrocycle is a 33-membered
25 years,2,3 the synthesis of such compounds continues to
ring, whereas a 30-membered ring cannot be threaded at all
benefit from more and more efficient cyclisation procedures
under the same conditions.
(for catenanes) or stoppering techniques (for rotaxanes). In
recent years, the Cu(I)-catalysed dipolar cycloaddition of
Results and discussion
azides and terminal alkynes, known as ‘‘click’’ chemistry,
has been used as a mild and efficient stoppering reaction for
The general synthesis principle is shown in Scheme 1.
the preparation of new rotaxanes and catenanes,4 including
Several examples of [3]pseudorotaxanes with ‘‘innocent’’
copper(I)-complexed rotaxanes5 belonging to the family of
stoppers (i.e. non-electro-, non-magneto- and non-photoactive)
compounds prepared in Strasbourg since the 1980s. This
and porphyrin-stoppered rotaxanes have already been
reaction, which is an important extension of the Huisgen
described by our group, but the axle consisted of two
reaction developed by Sharpless, Meldal and their co-workers,6
nowadays is one of the most efficient procedures for stoppering
pre-rotaxanes whose axle is end-functionalised by appropriate
functions, such as terminal alkynes or azides. Several years
ago, a wide family of porphyrin-stoppered rotaxanes was
prepared in our group using the ‘‘gathering and threading’’
effect of copper(I).7,8 Unfortunately, in most cases, the limiting
step of the overall synthesis was the final stopper-fixing
reaction. In the present report, we describe the efficient
synthesis of new [3]rotaxanes based on click chemistry. In
addition, during the threading step, an interesting ring size
1,10-phenanthroline chelates connected by a flexible linker.9
A few years ago, Lehn and co-workers reported the synthesis
of [3] and [4]pseudorotaxanes assembled via copper(I)
coordination, whose central axle was a rigid block with no
spacer between the two chelating units.10 In the present report,
the threaded fragment is a rigid rod, affording good control
over the geometry of the assembly. In addition, the click-based
stoppering reaction gives higher yields and is much simpler in
terms of experimental procedure than the previous techniques
used for making copper-complexed rotaxanes, which were
generally based on Williamson reactions. The target [3]rotaxane
is depicted in Fig. 1.
a
´
Laboratoire de Chimie Organo-Minerale, Institut de Chimie,
LC3 UMR 7177 du CNRS, Universite de Strasbourg,
1. Synthesis of the organic components
´
4 rue Blaise Pascal, 67070 Strasbourg Cedex, France.
E-mail: sauvage@chimie.u-strasbg.fr; Fax: +33 (0)3 90 24 13 68
b Nanoscience Center, Department of Chemistry, University of
The various organic precursors used are shown in Fig. 2.
Macrocyclic components 6 and 7 were synthesized according
to previously published experimental procedures.2a,11
Two-chelate rods 4 and 5 were prepared from compound 2
(Fig. 2), 4 being an intermediate in the preparation of 5. The
CRC bonds were introduced by a Sonogashira coupling
involving tri(isopropylsilyl)acetylene, NEt3 and PdCl2(PPh3)2
as a catalyst. The reaction was performed in hot DMF because
Jyvaskyla, P.O. Box 35, 40014 University of Jyvaskyla, Finland.
¨
¨
E-mail: kari.t.rissanen@jyu.fi
¨
¨
w Electronic supplementary information (ESI) available: NMR
assignment of the new compounds. CCDC reference number
733684. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/b9nj00278b
z X-Ray crystallography.
ꢀc
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Scheme 1 The construction principle of a [3]rotaxane by copper(I)-driven ‘‘gathering and threading’’ followed by stoppering. The coordinating
fragments are represented by U-shaped symbols, the small spheres are copper(I) atoms and the big spheres represent the stoppers.
Fig. 1 The chemical structure of [3]rotaxane 12+. The central part of the axle is a rigid block consisting of two laterally-connected bidentate
chelates.
2. The ‘‘gathering and threading’’ reaction
The first attempt to gather two macrocycles onto axle 4 were
realized by using ‘‘classical’’ 30-membered ring 6 in the
presence of two copper(I) equivalents (Fig. 3). Surprisingly,
essentially no threaded species was obtained, whatever
experimental conditions were employed (various solvents,
temperatures and reaction times). This result indicates that
the size of the triisopropyl group is too large to thread through
the central cavity of precursor complex [Cu(6)(CH3CN)2]+.
Interestingly, the use of a larger macrocycle, 7, consisting of
33 bonds in its inner circumference, led almost quantitatively
1
to the expected [3]pseudorotaxane 82+, as confirmed by a H
NMR study.
X-Ray quality crystals of 8(PF6)2 could be grown by slow
diffusion of diisopropylether into an acetone solution. The
X-ray study (Fig. 4) confirms the [3]pseudorotaxane structure.
Due to the nature of the axle, the Cu(I) ions reside on the same
Fig. 2 The chemical structures of the organic components: axles 4
side of the axle (a cis-rotaxane). The Cu(I) ions show a heavily
and 5, acetylenic fragment 3, and rings 6 and 7; compound 2 is the
distorted tetrahedral coordination, with N–Cu–N bond angles
precursor to both axles 4 and 5.
between 80–1391 and bond distances between 2.03–2.08 A
(Table 1). The long (Siꢁ ꢁ ꢁSi distance of 2.4 nm) axle is not
of the poor solubility of precursor 212 in common organic
linear, but is bent by the coordination to the copper ions so
that the angle between the centroid of the axle and the
terminal Si atoms is 1641.
solvents. The resulting axle 4 (TIPS-ended rod; TIPS =
triisopropylsilyl) was highly soluble in many common organic
solvents thanks to the triisopropyl functions and could be
easily purified by chromatography. Axle 4 was obtained in a
moderate yield of 55%. An attempt to introduce CRC triple
bonds with trimethylsilylacetylene by following the same
procedure was successful, in spite of a low yield, but the
solubility of the resulting compound was too low to allow its
effective purification. The acetylenic axle was obtained by the
reaction of TBAF (tetra-n-butyl-ammonium fluoride) with 4 in
THF. The poor solubility of the resulting compound meant
that it quickly precipitated in the reaction flask, thus allowing
purification by simple filtration and washing with water,
n-pentane and diethyl ether. This compound was obtained with
a yield of 97%. Thus, this functionalized ligand was easily
synthesized in 7 steps (5 steps for precursor 2 and 2 extra steps),
which is much less than the 15 steps of synthesis required for the
related ligands previously used in our laboratory.13
In similar rigid axle but non-acetylenic [3]- and [4]rotaxanes,10
comparable axle length-dependent and Cu coordination-based
bending is also observed. Two cis-[3]rotaxanes with shorter
1.1 nm axles show bending angles of 167.7 and 171.11,10a while
a bipy-like cis-4-rotaxane with a 1.48 nm axle10b shows curved
bending of 156.71. Contrary to the above mentioned [3]- and
[4]rotaxanes and our rotaxane 8, another bipy-like trans-
[3]rotaxane with a 1.59 nm long axle is not bent at all
(angle 1801).10c The phenanthroline moieties of threaded
macrocycles 7 are nearly parallel to each other but form a
51.4 and 52.31 angle between the plane defined by the central
part of the axle and the plane of the 5-N-phenanthroline part,
leading to a ‘‘slanted’’ overall orientation of the wheels around
the axle. The very strong intramolecular p–p stacking in the
cis-[3]- and -[4]rotaxanes10a,b orients the wheels perpendicularly
towards the axle. However, the trans-[3]-rotaxane10c shows a
ꢀc
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Fig. 3 Threading tests of the TIPS-bearing axle.
Due to the trans configuration of the Cu ions in trans-[3]-
rotaxane,10c the Cuꢁ ꢁ ꢁCu distance is 9.6 A, but the Cu ions are
on the opposite sides of the axle. The large Cuꢁ ꢁ ꢁCu separation
in 8 inhibits the intramolecular p–p interactions observed in
other similar rotaxanes10a,b and leads to relaxation of the
coordination around the Cu(I) ions by the slanted orientation
of the wheels around the axle. However, the intramolecular
distance between the phenanthroline moieties is perfect for
an insertion of the phenanthroline moiety of the adjacent
pseudorotaxane molecule, and thus pseudorotaxane 8 exists
in the crystal lattice as a p–p enhanced dimer (Fig. 5). It should
be noted that the tilted geometry of the chelating units
coordinated to Cu(I) ions has been observed both in
copper(I)-complexed catenanes and knots made in our group,
and studied by X-ray diffraction.14
In order to test the click chemistry method as a stoppering
reaction, we chose to introduce two alkyne functions
onto axle 5 and one azide function onto the classical
tris(p-tert-butylphenyl)(phenyl)methane stopper (compound 11).
This latter reagent was obtained in good yield by the reaction
of iodo derivative 1015 with NaN3 (Fig. 6(a)). Compound 11
has already been synthesized by Leigh’s group in a different
way.4d The threading of two macrocycles 6 onto axle 5 in
presence of two equivalents of [Cu(CH3CN)4](PF6) afforded
quantitatively the copper [3]pseudorotaxane 92+ (Fig. 6(b)), as
Fig. 4 Ball and stick (top) and the CPK (bottom) presentations of
[3]pseudorotaxane 8. The PF6 anions, solvent molecules and the
disorder of threaded macrocycle 7 are omitted for clarity.
Table 1 The bond distances (A) and angles (1) around the two copper
ions
Cu(1A)–N(6)
2.030(9)
2.042(7)
2.049(18)
2.076(8)
N(6)–Cu(1A)–N(11)
N(1A)–Cu(1A)–N(11A)
N(6)–Cu(1A)–N(1A)
N(11)–Cu(1A)–N(1A)
N(6)–Cu(1A)–N(11A)
N(11)–Cu(1A)–N(11A)
N(19)–Cu(1B)–N(25)
N(1B)–Cu(1B)–N(11B)
N(19)–Cu(1B)–N(1B)
N(25)–Cu(1B)–N(1B)
N(19)–Cu(1B)–N(11B)
N(25)–Cu(1B)–N(11B)
80.7(4)
80.3(6)
Cu(1A)–N(11A)
Cu(1A)–N(1A)
Cu(1A)–N(11)
139.4(4)
112.4(4)
115.9(5)
138.8(4)
81.1(3)
Cu(1B)–N(25)
Cu(1B)–N(19)
Cu(1B)–N(1B)
Cu(1B)–N(11B)
2.039(7)
2.045(8)
2.053(10)
2.079(9)
83.9(5)
137.2(3)
112.6(3)
112.7(4)
139.2(3)
slanting by 58.91; this is due to the absence of intramolecular
p–p stacking and its centrosymmetry.10c The Cuꢁ ꢁ ꢁCu distance
in [3]pseudorotaxane 8 is 7.8 A, much longer that in similar
cis-[3]- and -[4]rotaxanes,10a,b where the corresponding
distances are 3.5 and 3.7,10a and 3.6 and 4.3 A, respectively.10b
Fig. 5 p–p enhanced dimer formation of 8 in the crystal lattice.
ꢀc
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Fig. 6 (a) The synthesis of stopper 11, (b) copper [3]pseudorotaxane 92+ and (c) the double stoppering reaction.
1
confirmed by a H NMR study. This ligand has already been
used for the quantitative formation of [4]pseudorotaxane-
containing porphyrins.16 The double stoppering reaction
(Fig. 6(c)) was achieved in a CH2Cl2/CH3CN (3 : 1) mixture
with a catalytic amount of [Cu(CH3CN)4](PF6) and Na2CO3
as a base for 5 d. After work-up, the copper [3]rotaxane 12+
was obtained in 46% yield, which is very close to the yield
obtained in the laboratory for the formation of a similar
[3]rotaxane with other ligands but the same click reaction.13
3. Demetallation of copper [3]rotaxane 12+
In order to confirm the threaded nature of copper rotaxane
12+, it was demetallated and submitted to purification by silica
chromatography. The treatment of 12+ with an excess of KCN
in a CH2Cl2/CH3CN/H2O (2 : 1 : 1) mixture at room
temperature afforded free [3]rotaxane 12 in 96% yield. The
Fig. 8 1H NMR spectra of metallated rotaxane 12+ and demetallated
rotaxane 12.
1
ES-MS and H NMR spectrum were in accordance with the
postulated structure (Fig. 7).
Conclusion
We noticed large differences between the spectra of the
metallated and demetallated compounds (Fig. 8). Indeed, the
aromatic region of the spectrum of copper rotaxane 12+ is
spread over 3.5 ppm from d 6 to 9.5, which is characteristic
of a threaded copper complex, whereas the spectrum of
demetallated rotaxane 12 is spread over 2.5 ppm from d 6.7
to 9.2. The signals of the threaded macrocycles are different
from the signals of the free macrocycles, confirming that
compound 12 is a real rotaxane and that the stoppers prevent
the unthreading of the macrocycles.
In conclusion, the use of a bis(2-pyridyl)-4,7-phenanthroline
unit as a central part of an axle, with its rigid structure and two
bidentate chelating sites, allowed the preparation of a copper-
complexed [3]rotaxane in good yield. The synthesis relied on a
copper(I)-induced double threading reaction of two large
macrocycles onto the rigid axle and, subsequently, click
chemistry as the stopper-fixing reaction. Demetallation
afforded quantitatively the metal-free [3]rotaxane. Dicopper
[3]pseudorotaxane 8, containing TIPS groups at the ends of
Fig. 7 The demetallation of 12+
.
ꢀc
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the threaded axle, could be crystallised and studied by X-ray
crystallography. This structure is a rare example of a Cu(I)
rotaxane or pseudorotaxane. It shows that the two threaded
rings are coordinated to the axle and that the rings are slanted
towards the axle, the planes of the ring-incorporated
1,10-phenanthroline chelates being tilted with respect to the
axis and not at all perpendicular to it.
This solution was then added to a de-gassed solution of TIPS
thread 4 (9.97 mg, 14.4 mmol) in CH2Cl2 (2 mL) via a cannula;
the mixture immediately turned brown and was reacted
overnight. After evaporation of the solvents, the crude
product was redissolved in CH3CN and filtered in order to
eliminate the possible excess of organic ligands. The CH3CN
was evaporated to give 33 mg (14.1 mmol) of [3]pseudorotaxane
1
(96% yield). H NMR (300 MHz, CD2Cl2, 25 1C): d = 9.44
(d, J3 = 8.8 Hz, 2H), 8.69 (d, J3 = 8.8 Hz, 2H), 8.60 (d, J3 =
8.3 Hz, 4H), 8.50 (d, J3 = 8.3 Hz, 2H), 8.26 (dd, J3 = 8.3 Hz,
J4 = 1.8 Hz, 2H), 8.08 (s, 4H), 7.98 (d, J3 = 8.3 Hz, 4H), 7.94
(d, J4 = 1.8 Hz, 2H), 7.30 (s, 2H), 7.24 (d, J3 = 8.6 Hz, 8H),
6.11 (d, J3 = 8.6 Hz, 8H), 4.00–3.70 (m, 48H) and 1.15
(s, 42H). MS (ES): m/z (%) = 1021.3189 (100) [M2+]/2
(calc. 1021.3924).
Experimental section
TIPS axle 4
12 mL of anhydrous DMF and 1 mL of distilled NEt3 were
introduced into an oven-dried flask. The mixture was
de-gassed for 20 min with argon. 11.5 mg (60.4 mmol) of
CuI, 31.7 mg (45.2 mmol) of PdCl2(PPh3)2, 301 mg (612 mmol)
of bromide thread 2 and 0.6 mL (2.72 mmol) of triisopropyl-
silylacetylene were subsequently added. The solution was then
heated up to 100 1C under an argon atmosphere and stirred
for 17 h. The reaction mixture was cooled down to room
temperature and 13.4 mg (19.1 mmol) of PdCl2(PPh3)2 was
added. The solution was heated to 100 1C for a further 5 h and
then cooled down to room temperature. The solvents were
evaporated and the product purified by silica chromatography
with CH2Cl2. The product was then washed with pentane, and
was obtained in 55% yield. 1H NMR (300 MHz, CDCl3,
25 1C): d = 9.05 (d, J3 = 8.8 Hz, 2H), 8.82 (dd, J4 = 1.3 Hz,
J5 = 0.7 Hz, 2H), 8.78 (d, J3 = 8.8 Hz, 2H), 8.68 (dd, J3 =
8.2 Hz, J5 = 0.7 Hz, 2H), 8.33 (s, 2H), 7.95 (dd, J3 = 8.2 Hz,
J4 = 2.2 Hz, 2H) and 1.17 (s, 42H). 13C NMR (300 MHz,
CDCl3, 25 1C): d = 155.70, 154.44, 152.28, 147.61, 139.81,
132.59, 131.77, 124.81, 121.03, 120.84, 119.67, 103.80, 96.38,
18.69 and 11.30. MS (ES) : m/z (%) = 695.4044 (100)
[M + H]+ (calc. 695.3960) and 717.3862 (100) [M + Na]+
(calc. 717.3779).
ꢂ
Acetylenic [3]pseudorotaxane 92+(PF6
)
2
To a de-gassed solution of macrocycle 6 (29.6 mg, 52.2 mmol)
in dry CHCl3 (5 mL) was added solution of
a
[Cu(CH3CN)4](PF6) (21 mg, 56.3 mmol) in dry and de-gassed
CH3CN (5 mL), and stirred at room temperature for 30 min
under an inert atmosphere. This solution was then added to a
de-gassed suspension of acetylenic axle 5 (9.8 mg, 25.6 mmol)
in dry CHCl3 (15 mL) via a cannula; the mixture turned
immediately brown and homogeneous, and was reacted
overnight. After evaporation of the solvents, the crude
product was redissolved in CH3CN and filtered in order to
eliminate the possible excess of organic ligands. The CH3CN
was evaporated to give the [3]pseudorotaxane (49 mg,
25.4 mmol) in quantitative yield. 1H NMR (300 MHz, CD2Cl2,
25 1C): d = 9.54 (d, J3 = 8.8 Hz, 2H), 8.77 (d, J3 = 8.8 Hz,
2H), 8.64 (d, J3 = 8.4 Hz, 4H), 8.57 (d, J3 = 8.3 Hz, 2H), 8.23
(dd, J3 = 8.2 Hz, J4 = 1.9 Hz, 2H), 8.13 (s, 4H), 8.06 (d, J4 =
1.6 Hz, 2H), 8.03 (d, J3 = 8.3 Hz, 4H), 7.38 (s, 2H), 7.22
(d, J3 = 8.7 Hz, 8H), 6.12 (d, J3 = 8.7 Hz, 8H), 4.00–3.75
(m, 40H) and 3.53 (s, 2H). MS (ES): m/z (%) = 821.2281 (100)
[M2+]/2 (calc. 821.2324).
Acetylenic axle 5
101 mg (0.14 mmol) of TIPS axle 4 was diluted in 7 mL of
THF. 0.39 mL of a 1 M solution of TBAF (0.39 mmol) in THF
was then added and a fine precipitate immediately formed.
After half an hour of stirring, the solvent was evaporated. The
residual brown precipitate obtained after the evaporation of
the THF was washed well with water, ether and n-pentane,
and filtered over a Millipore filter. 54 mg (0.14 mmol) of a
yellowish powder was thus obtained (97% yield). 1H NMR
(300 MHz, CDCl3, 25 1C): d = 9.07 (d, J3 = 8.8 Hz, 2H), 8.85
(dd, J4 = 2.0 Hz, J5 = 0.7 Hz, 2H), 8.78 (d, J3 = 8.8 Hz, 2H),
8.72 (dd, J3 = 8.1 Hz, J5 = 0.6 Hz, 2H), 8.33 (s, 2H), 7.99
(dd, J3 = 8.1 Hz, J4 = 2.1 Hz, 2H) and 3.34 (s, 2H). 13C NMR
(300 MHz, CDCl3, 25 1C): d = 161.53, 160.95, 160.39, 159.81,
148.49, 146.79, 138.80, 132.22, 120.77, 119.97, 116.20, 112.43
and 108.65. MS (ES): m/z (%) = 383.1175 (100) [M + H]+
(calc. 383.1291).
Azide stopper 11
Iodide derivative 10 (603 mg, 0.90 mmol) and NaN3 (482 mg,
7.41 mmol) were diluted in 10 mL of DMF, 3 mL of water,
10 mL of THF and 10 mL of CH2Cl2. The solution was stirred
for 4 d and the solvents evaporated. The crude product was
then washed with 20 mL of water and the aqueous layer
extracted with CH2Cl2. The organic layer was dried over
MgSO4. After evaporation of the CH2Cl2, 506 mg (0.86 mmol)
of a white powder was obtained (96% yield). 1H NMR
(300 MHz, CDCl3, 25 1C): d = 7.27 (d, J3 = 8.8 Hz, 6H),
7.16 (d, J3 = 8.6 Hz, 6H), 7.16 (d, J3 = 8.6 Hz, 2H), 6.79
(d, J3 = 8.8 Hz, 2H), 4.02 (t, J3 = 6.0 Hz, 2H), 3.50 (t, J3 =
6.7 Hz, 2H), 2.03 (q, J3 = 6.3 Hz, 2H) and 1.31 (s, 27H).
ꢂ
[3]Rotaxane 12+(PF6
)
2
ꢂ
TIPS [3]pseudorotaxane 82+(PF6
)
2
[3]Pseudorotaxane 92+(PF6ꢂ)2 (49 mg, 25.5 mmol), N3 stopper
11 (50 mg, 85.1 mmol), Na2CO3 (1.8 mg, 16.9 mmol) and
[Cu(CH3CN)4](PF6) (5 mg, 13.4 mmol) were diluted in 3 mL
of dry and de-gassed CH2Cl2 and 1 mL of dry and de-gassed
CH3CN. The solution was stirred under argon for 5 d.
To a de-gassed solution of macrocycle 7 (17.5 mg, 28.7 mmol)
in CH2Cl2 (2 mL) was added a solution of [Cu(CH3CN)4](PF6)
(10.7 mg, 28.7 mmol) in de-gassed CH3CN (1 mL) and stirred
at room temperature for 20 min under an inert atmosphere.
ꢀc
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The solvents were then evaporated and the resulting black
residue purified by silica chromatography. A gradient of
elution CH2Cl2 : EtOH : CH3CN of 98 : 1 : 1 to 96 : 2 : 2 gave
36 mg (11.6 mmol) of rotaxane (46% yield). 1H NMR
(300 MHz, CD2Cl2, 25 1C): d = 9.49 (d, J3 = 8.9 Hz, 2H),
8.72 (d, J3 = 8.1 Hz, 2H), 8.58 (d, J3 = 8.2 Hz, 4H), 8.57
(d, J3 = 8.2 Hz, 2H), 8.50 (s, 2H), 8.47 (dd, J3 = 8.3 Hz, J4 =
1.9 Hz, 2H), 8.19 (s, 2H), 8.07 (s, 4H), 7.94 (d, J3 = 8.1 Hz,
4H), 7.34 (s, 2H), 7.22 (d, J3 = 8.6 Hz, 12H), 7.21 (d, J3 = 8.9
Hz, 4H), 7.15 (d, J3 = 7.9 Hz, 8H), 7.11 (d, J3 = 8.8 Hz, 12H),
6.78 (d, J3 = 8.9 Hz, 4H), 6.00 (d, J3 = 7.9 Hz, 8H), 4.65
(t, J3 = 6.8 Hz, 4H), 3.99 (t, J3 = 5.4 Hz, 4H), 3.92–3.70
(m, 40H), 2.43 (q, J3 = 6.1 Hz, 4H) and 1.26 (s, 54H). MS
(ES): m/z (%) = 1409.0656 (100) [M2+]/2 (calc. 1409.1217).
b = 20.1482(7), c = 26.926(1) A, a = 69.490(2), b =
88.660(2), g = 74.205(3)1, V = 6509.8(5) A3, Z = 2,
Dcalc = 1.267 g cmꢂ3, m = 0.45 mmꢂ1, 25 576 reflections
measured (2ymax = 22.51), 16 719 independent reflections,
7862 with I 4 2s(I), number of parameters = 1509, number
of restraints = 389, Rint = 0.0532, R = 0.1327 [I 4 2s(I)],
wR2 = 0.379 (all data), GOF = 1.149. Maximum and
minimum peaks in the difference map: 0.993 and ꢂ0.491 eAꢂ3
.
The severe disorder and large thermal movement of the
isopropyl methyl carbon renders the positions of the methyl
hydrogens inaccurate.w
Acknowledgements
The authors gratefully acknowledge the Academy of Finland
(K. R.: project no. 212588) and the Ministry of Education for
fellowships to Y. T. We also thank Jean-Francois Ayme for his
contribution to the synthesis of compound 4.
Demetallated [3]rotaxane 12
Metallated [3]rotaxane 12+(PF6
) (10 mg, 3.22 mmol) and
2
ꢂ
KCN (9 mg, 138 mmol) were diluted in 1 mL of CH2Cl2,
0.5 mL of CH3CN and 0.5 mL of distilled water, and stirred
for 3 h. Then, 10 mL of water and 10 mL of CH2Cl2 were
added and the two layers separated. The aqueous layer was
extracted three times with 10 mL of CH2Cl2 and the organic
layer dried over MgSO4. After evaporation of the solvent, the
crude product was purified by alumina chromatography.
A gradient of elution CH2Cl2 : EtOH of 100 : 0 to 98 : 2 gave
8.3 mg (3.1 mmol) of demetallated rotaxane (96% yield).
References
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1H NMR (300 MHz, CD2Cl2, 25 1C): d = 9.16 (d, J3
=
8.9 Hz, 2H), 9.07 (d, J4 = 1.4 Hz, 2H), 8.81 (s, 2H), 8.77
(d, J3 = 8.6 Hz, 2H), 8.64 (d, J3 = 8.2 Hz, 2H), 8.31 (s, 2H),
8.26 (d, J3 = 8.4 Hz, 4H), 8.15 (d, J3 = 8.2 Hz, 2H), 8.14
(d, J3 = 8.7 Hz, 8H), 7.95 (d, J3 = 8.4 Hz, 4H), 7.77 (s, 4H),
7.24 (d, J3 = 8.6 Hz, 12H), 7.14 (d, J3 = 8.7 Hz, 12H), 7.09
(d, J3 = 8.8 Hz, 4H), 6.78 (d, J3 = 9.0 Hz, 4H), 6.72 (d, J3 =
8.7 Hz, 8H), 4.31 (t, J3 = 7.1 Hz, 4H), 3.92–3.85 (m, 12H),
3.64 (s, 8H), 3.55–3.45 (m, 24H), 2.21 (q, J3 = 6.4 Hz, 4H) and
1.29 (s, 54H). MS (ES): m/z (%) = 2754.3143 (100) [M + H]+
(calc. 2754.1696).
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Crystallography
Data were recorded with a Bruker-Nonius Kappa APEX II
diffractometer using graphite-monochromatized Mo-Ka
radiation (l = 0.71073 A) at 123.0(1) K. The data were
processed with Denzo-SMN v0.95.373,17 and the structure
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correction was applied. The hydrogen atoms were calculated
in their idealized positions with isotropic temperature factors
(1.2 or 1.5 times the C temperature factor) and refined as
riding atꢂoms. Severe disorder in one of the macrocycles, one of
the PF6 anions and one of the solvent acetone molecules
in 8 was treated with robust restraints to prevent chemically
unreasonable bond distances and angles. The crystal lattice
contained voids and the electron density within them was
treated with the SQUEEZE program.20
Crystal data for 8
Formula: C123.5H142N8O17Cu2F12P2Si2, crystal size: 0.25 ꢃ
0.25 ꢃ 0.45 mm, triclinic, space group: P-1, a = 13.3567(7),
ꢀc
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