A dual-response [2]rotaxane based on a 1,2,3-triazole ring as a novel recognition station

Article abstract of DOI:10.1002/chem.200901841

Two novel multilevel switchable [2]rotaxanes containing an ammonium and a triazole station have been constructed by a Cu^I-catalyzed azide-alkyne cycloaddition reaction. The macrocycle of [2]rotaxane containing a C6-chain bridge between the two

Full text of DOI:10.1002/chem.200901841

FULL PAPER
DOI: 10.1002/chem.200901841
A Dual-Response [2]Rotaxane Based on a 1,2,3-Triazole Ring as a Novel
Recognition Station
Haiyan Zheng,[a, b] Weidong Zhou,[a, b] Jing Lv,[a, b] Xiaodong Yin,[a, b] Yongjun Li,[a]
Huibiao Liu,[a] and Yuliang Li*[a]
Abstract: Two novel multilevel switch-
able [2]rotaxanes containing an ammo-
nium and a triazole station have been
constructed by a CuI-catalyzed azide–
alkyne cycloaddition reaction. The
macrocycle of [2]rotaxane containing a
C6-chain bridge between the two hy-
drogen bonding stations exhibits high
selectivity for the ammonium cation in
the protonated form. Interestingly, the
macrocycle is able to interact with the
two recognition stations when the
bridge between them is shortened.
Upon deprotonation of both [2]ro-
taxanes, the macrocycle moves towards
the triazole recognition site due to the
hydrogen-bond interaction between the
triazole nitrogen atoms and the amide
groups in the macrocycle. Upon addi-
tion of chloride anion, the conforma-
tion of [2]rotaxane is changed because
of the cooperative recognition of the
chloride anion by a favorable hydro-
gen-bond donor from both the macro-
cycle isophthalamide and thread tri-
azole CH proton.
Keywords: anions · click chemistry ·
rotaxanes · supramolecular chemis-
try · triazoles
Introduction
its high efficiency, tolerance of sensitive functional groups,
and mild reaction conditions.[7] Various complex structures,
such as dendrimers,[8] polymers,[9] macrocycles,[10] molecular
nanocages,[11] and derivatization of biological molecules[12]
have been accomplished successfully by the click reaction.
In particular, it can occur in apolar solvent at room temper-
ature. These conditions are favorable for the hydrogen-bond
recognition between macrocycle and thread in construction
mechanical interlocked molecules.[13] Recently, examples of
a click-reaction-based synthesis of rotaxanes and catenanes
have been reported.[14] The molecular rotaxane and muscle
developed by Busseron et al. also showed that the triazolium
cation could be recognized by dibenzo-[24]crown-8.[15] This
recognition process mainly relies on the positively charged
triazolium ion. However, to the best of our knowledge, the
1,2,3-triazole generated by the click reaction as a molecular
station is still rare.[16] In our system, the click reaction is not
only a key step of stoppering the reaction but it also pro-
vides a potential alternative binding site, which is introduced
directly by a coupling procedure.
Mechanical interlocked molecules, in particular rotaxanes
and catenanes, have received considerable attention due to
their challenging construction and potential application in
nanometer-scale molecular devices.[1] The rotaxanes that can
be switched between two or more states on different stimuli
have gained much more interest.[2] Various external stimuli
have been employed to induce such switching, such as ion
binding,[3] conformational changes,[4] and alternation of the
oxidation state[5] or protonation level of the molecule.[6] CuI-
catalyzed 1,3-dipolar cycloaddition reactions of organic
azides and terminal alkynes also called “CuAAC click
chemistry” has emerged as a powerful and appealing syn-
thetic tool for the construction of complex materials due to
[a] H. Zheng, W. Zhou, J. Lv, X. Yin, Dr. Y. Li, Dr. H. Liu, Prof. Y. Li
CAS Key Laboratory of Organic Solids
Beijing National Laboratory for Molecular Sciences (BNLMS)
Institute of Chemistry, Chinese Academy of Sciences
Beijing 100190 (P.R. China)
Previous reports described the hydrogen-bond acceptor[17]
and Lewis base properties of triazole nitrogen atoms[18] as
well as the recognition study of anions by the polarized CH
proton of triazole.[19] The large dipole (5D) of triazole, the
positive end of which points toward the H atom, contributes
to its unexpectedly strong hydrogen-bonding capabilities.[19a]
Isophthalamide and its derivatives play an important role in
Fax : (+86)10-82616576
E-mail: ylli@iccas.ac.cn
[b] H. Zheng, W. Zhou, J. Lv, X. Yin
Graduate University of Chinese Academy of Sciences
Beijing 100190 (P.R. China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200901841.
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the design of anion receptors,[20] rotaxanes,[21] and cate-
nanes[22] because of their abilities to act as strong hydrogen-
bonding donors in various solutions. With these in mind, we
are very interested to examine 1) whether the 1,2,3- triazole
ring system resulting from the facile cycloaddition reaction
could interact with the macrocycle containing amide units
by hydrogen bonding and whether a new type of molecular
shuttle could be generated and, if so, 2) whether the confor-
mation of the macrocycle can be changed by anions due to
the cooperative complexation in the pocket generated by
the isophthalamide group of the macrocycle and the CH
proton of triazole in the thread. For these reasons, two
[2]rotaxanes have been designed and synthesized that incor-
porate alkyl ammonium and 1,2,3-triazole “stations” in the
thread and an isophthalamide group and polyether chain in
the macrocycle by a click reaction. In this system, the shut-
tling of the macrocycle along
hydrogen-bond interactions with the macrocycle which pro-
vides a second binding site.
The MALDI-TOF spectrum of R-H-1 gave sharp peaks at
m/z: 2041.5 [MÀPF6ÀH+Na]+ and 2057.5 [MÀPF6ÀH+K]+
(see the Supporting Information) which revealed the fea-
tures of an interlocked molecule. The position of the macro-
cycle M-1 in rotaxane could be readily determined by com-
1
paring the H NMR spectra of the uncomplexed dumbbell-
shaped thread and the rotaxane since the xylylene parts of
the macrocycle shield the encapsulated regions of the
thread.[23,13c]
1
As shown in Figure 1, the H NMR spectra of thread T-H-
1, rotaxane R-H-1, and macrocycle M-1 in acetonitrile readi-
ly confirm the interlocked structure and show that the mac-
rocycle M-1 in rotaxane R-H-1 is largely localized on the
alkyl ammonium region of the thread under acidic condi-
the thread driven by acid/base
and the conformational alterna-
tion of the macrocycle driven
by anions has been realized.
In this contribution, we wish
to highlight that the click reac-
tion is not only a valuable tool
to fabricate the functional ro-
taxane, but also the generated
1,2,3-triazole resulting in hydro-
gen-bond interactions with the
macrocycle, which will be a reli-
able building style for the con-
struction of novel and complex
structures.
Results and Discussion
The shuttle R-H-1 was synthe-
sized according to Scheme 1. In
CH2Cl2, macrocycle M-1 assem-
bled with the monostoppered
ammonium containing com-
pound 8 to form a pseudorotax-
ane.[23] Covalent capture of the
threaded intermediate by
a
click reaction at room tempera-
ture in the presence of [Cu-
ACHTUNGTRENNUNG(MeCN)4]BF4 as the catalyst af-
forded the thread T-H-1 and
[2]rotaxane R-H-1 in 50 and
35% yield after chromato-
graphic column purification, re-
spectively.
In our system, the azide–
alkyne cycloaddition is not only
a key step of the stoppering re-
action, but also the generated
1,2,3-triazole can participate in Scheme 1. Synthesis of R-H-1 and T-H-1.
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A Dual-Response [2]Rotaxane
FULL PAPER
À À
nounced, which results from a combination of C H O and
[6]
N+ H O hydrogen-bond interactions.
À À
As shown in Figure 2, upon addition of 1.2 equivalents of
iPr2NEt to R-H-1, the ammonium group was neutralized
and the hydrogen bonds between the polyether moiety and
the ammonium group were destroyed. Several characteris-
tics reflect the position of the macrocycle M-1 in rotaxane
R-1: 1) the signals for the protons adjacent to the triazole
ring exhibit a substantial upfield shift (Hl: d=0.28 and Hn:
0.26 ppm) compared with the free thread T-1, which could
be attributed to the aromatic shielding effect by the macro-
cycle; 2) a significant downfield shift by d=0.35 ppm is ob-
served for the amide protons HD of the macrocycle M-1,
which indicates significant hydrogen-bond interactions be-
1
Figure 1. Partial H NMR spectra (400 MHz, CD3CN, 4ꢁ10À3 m, 298 K) of
a) T-H-1, b) R-H-1, and c) M-1. The letters corresponding to the protons
are shown in Scheme 1.
tions. As expected, the protons adjacent to the ammonium
unit experience an upfield shift (He: d=0.24, Hd: 0.14 ppm)
relative to those in free T-H-1 due to the aromatic shielding
effect of the macrocycle, whereas no variation of the protons
near the triazole ring are noticed, which indicates that the
macrocycle resides exclusively around the ammonium cation
center. The thread phenylene protons Hf and Hg are shifted
upfield in R-H-1 as a result of the aromatic shielding effect
of the macrocycle. In addition, the signals of HF and HG be-
longing to the macrocycle also experience an upfield shift,
which indicates that the macrocycle is probably sandwiching
the phenylene spacer so as to benefit from supplementary
stabilization by means of weak p–p stacking interactions.
The polyether protons HH and HI are shifted upfield slight-
ly; the upfield shifts of protons HJ and HK are more pro-
1
Figure 2. Partial H NMR spectra (400 MHz, CD3CN, 4ꢁ10À3 m, 298 K) of
a) deprotonated thread T-1, b) deprotonated rotaxane R-1, and c) M-1.
The letters corresponding to the protons are shown in Scheme 1.
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Y. Li et al.
tween the amide and the hydro-
gen-bond acceptor of the tri-
azole nitrogen atoms;[23] 3) the
proton of the triazole ring Hm is
shifted upfield by d=0.14 ppm
as
a result of the aromatic
shielding effect (upfield) and
hydrogen bonding to the poly-
ether (downfield). All these
features confirm that the mac-
rocycle moves to the triazole
recognition site because of the
hydrogen bonds between them
(Scheme 2). In addition, the
polyether protons (HH–HK) are
shifted upfield by roughly d=
0.1 ppm, which indicates that
the polyether oxygen atoms
accept hydrogen bonds from
the proton of the triazole ring.
Upon addition of CF3COOH to
the deprotonated rotaxane R-1,
the four protons Hl and Hn
appear at d=4.98 and 4.45 ppm
as well as the signal for the tria-
zole ring proton, which reso-
nates at d=7.75 ppm, which
suggests that the M-1 compo-
nent shuttles back completely
Scheme 2. Movement process of R-H-1 under acid/base stimuli.
+
to the NH2 recognition site
following reprotonation (Fig-
ure S1, Supporting Informa-
tion). According to the signal
of the proton Hl, it is apparent
that the PH-controlled switch-
ing process is reversible and
can be cycled in several times
(Figure S2, Supporting Informa-
tion).
To verify the hydrogen-bond
interactions between the mac-
rocycle M-1 and the 1,2,3-tri-
azole ring, a rotaxane R-H-2
containing a short bridge be-
tween the two recognition sites
was synthesized with the by a
similar
reaction
process
(Scheme 3). The MALDI-TOF
spectrum of R-H-2 revealed a
high-intensity peak at m/z:
1827.5 corresponding to R-H-
Scheme 3. Synthesis of R-H-2 and T-H-2.
À
2+ after the loss of a PF6 unit.
Interestingly, differing from rotaxane R-H-1, an aromatic
shielding effect is observed for the proton adjacent to the
1,2,3-triazole ring (Hh =0.25 ppm) in R-H-2 compared with
it in free thread T-H-2 (Figure 3). Moreover, the ring amide
protons HD experience a downfield shift of d=0.25 ppm in
R-H-2 with respect to M-1, which is ascribed to hydrogen
bonding to the hydrogen-bond acceptor, that is, the triazole
nitrogen atoms. However, the proton Hi of the triazole ring
and Hj close to it do not exhibit an obvious shift relative to
those in thread T-H-2. All these features probably indicate,
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A Dual-Response [2]Rotaxane
FULL PAPER
of symmetry orthogonal to the principal axis in the molecu-
lar shuttle.[6] The polyether protons (HH–HK) shift upfield by
À À
d=0.1 ppm roughly as a result of a combination of C H O
[6]
and N+ H O hydrogen bonds.
À À
Thus, the 1H NMR spectra support that the isophthal-
amide group interacts with the triazole and the polyether
moiety interacts with ammonium cation. That is to say, the
macrocycle spans two potential hydrogen-bonding recogni-
tion stations by
Scheme 4).
a short bridge between them (see
Deprotonation of R-H-2 with 1.2 equivalents of iPr2NEt
resulted in significant changes to the 1H NMR spectra in
acetonitrile (Figure 4). The upfield shifts of the protons near
the 1,2,3-triazole ring (Hh: d=0.3, Hj: 0.3 ppm) in R-2 com-
pared with those in free thread T-2 should be ascribed to
1
Figure 3. Partial H NMR spectra (400 MHz, CD3CN, 4ꢁ10À3 m, 298 K) of
a) T-H-2, b) R-H-2, and c) M-1. The letters corresponding to the protons
are shown in Scheme 3.
to some extent, that the isophthalamide group interacts with
the triazole ring due to the hydrogen bonds between them.
However, M-1 does not reside around the triazole center
completely, which arises from the ammonium cation–crown
ether interaction. The signals corresponding to phenylene
protons (Hf: d=0.3 and Hg: 0.4 ppm) and the macrocycle
benzyl groups (HF: d=0.21 and HG: 0.31 ppm) experience a
significant upfield shift as a result of the aromatic shielding
effect between them. Based on this fact, the macrocycle M-1
also forms the sandwiching structure with the phenylene
spacer in thread T-H-2 by means of weak p–p stacking inter-
actions. The protons HE/E’, HH/H’, HI/Iꢂ separate into two dif-
ferent sets of signals as a consequence of losing the planes
Scheme 4. Movement process of multistable rotaxane R-H-2 under differ-
ent stimuli.
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Y. Li et al.
Figure 5. Partial H NMR spectra (400 MHz, CD3CN, 4ꢁ10À3 m, 298 K) of
a) rotaxane R-H-2, and b) deprotonated rotaxane R-2. The letters corre-
sponding to the protons are shown in Scheme 3.
1
1
Figure 4. Partial H NMR spectra (400 MHz, CD3CN, 4ꢁ10À3 m, 298 K) of
a) deprotonated thread T-2, b) deprotonated rotaxane R-2, and c) M-1.
The letters corresponding to the protons are shown in Scheme 3.
deprotonation of the neighboring ammonium center and the
shuttling of the macrocycle. As shown in Figure 5, when
1.2 equivalents of iPr2NEt were added to the solution of R-
H-2, the signal assigned to Hh shifted upfield (d=0.1 ppm),
whereas HD shifted downfield by d=0.17 ppm. The protons
Hh and HD shift further after the addition iPr2NEt to the R-
H-2, which confirms the M-1 spans the two hydrogen-bond
recognition sites in acidic conditions (Scheme 4). The con-
version of originally separate broad signals for the protons
of methylene groups in the diethylene glycol moiety of the
macrocycle into the overlapping signals suggests the strong
hydrogen bonding between the ammonium cation and the
polyether has been destroyed after addition of iPr2NEt to
the solution of R-H-2. The upfield shifts of Hi (d=
0.22 ppm) and Hj (d=0.2 ppm) of R-H-2 indicate that the
the aromatic shielding effect by the encapsulating M-1. The
ring amide protons HD experience a significant downfield
shift of d=0.42 ppm with respect to M-1 due to hydrogen
bonding with the hydrogen-bond acceptor of the triazole ni-
trogen atoms. In addition, the d=0.12 ppm upfield shift of
the triazole ring proton Hi is characteristic of a combination
interaction of aromatic shielding effects (upfield) and hydro-
gen bonding to the polyether moiety in M-1 (downfield).
All these features support the fact that the macrocycle
moves towards the triazole recognition site completely
where they can interact by hydrogen bonding (Scheme 4).
1
The H NMR spectra of R-H-2 and R-2 in acetonitrile are
shown in Figure 5. On addition of iPr2NEt to R-H-2, the
signal for He was shifted upfield by d=0.46 ppm because of
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A Dual-Response [2]Rotaxane
FULL PAPER
macrocycle mainly resides around the triazole station due to
the hydrogen bonds between them. Upon addition of
CF3COOH to the fully deprotonated R-H-2, the signals for
Hj and the triazole hydrogen Hi are shifted downfield by d=
0.19 and 0.16 ppm relative to R-2, whereas slight variations
were observed for the protons Hh (d=0.04 ppm) and HD
(Figure S3, Supporting Information). All features indicate
that the isophthalamide group of M-1 interacts with the tri-
azole and the polyether moiety switches between the two
recognition sites by a de-/reprotonation process (Figure S4,
Supporting Information).
We employed the deprotonated[2]rotaxane R-2 to demon-
strate the chloride anion controllable conformational chang-
ing behavior in acetonitrile solution because the 1H NMR
spectrum was fairly simpler than R-1. Upon addition of the
chloride anion as its tetrabutylammonium (TBA) salt to a
solution of [2]rotaxane R-2, dramatic changes of the
1H NMR spectrum have been observed (Figure 6). As
shown in Figure 6b, after the addition of 10 equivalents of
chloride, the isophthalamide protons HC and HD are shifted
downfield by d=0.68 and 1.54 ppm, respectively, which is
due to hydrogen bonds between them.[20c] The signal for the
triazole proton experiences a downfield shift of d=0.2 ppm
due to hydrogen bonding to the chloride anion.[19] These
phenomena can be attributed to the cooperative recognition
of the chloride anion by a favorable hydrogen-bond donor
from both macrocycle isophthalamide (HC and HD) and
thread triazole proton. In addition, the proton Hh is shifted
downfield by d=0.14 ppm relative to itself in R-2, but still
less than d=5.12 ppm, which suggests the shielding effect of
the macrocycle is reduced as a result of the conformational
change on cooperative recognition of the chloride anion.
However, a slight upfield shift is observed for Hj (d=
0.1 ppm) relative to itself in R-2, which indicates that the
shielding effect of the macrocycle is increased after confor-
mational change. To demonstrate the chloride anion as an
effective choice to alter the conformation of R-2, the TBA
salts of bromide and iodide anions were also investigated by
1H NMR spectra (Figure S5 and S6, Supporting Informa-
tion). Based on the Job-plot determination of a 1:1 binding
stoichiometry (Figure S7, Supporting Information), associa-
tion constants for all anions (Table 1) were obtained by fit-
ting the changes in the chemical shift of proton C to the
binding isotherm (Figure S8, S9, and S10, Supporting Infor-
Figure 6. Partial 1H NMR spectra (400 MHz, CD3CN, 3.6ꢁ10À3 m, 298 K)
of rotaxane R-2 in the presence of a) 0, b) 10 equiv of TBACl (CD3CN,
0.12m), and c) T-2. The letters corresponding to the protons are shown in
Scheme 3.
mation).[24] The strength of anion association was observed
to increase in the order IÀ <BrÀ <ClÀ . This is consistent
with the increasing hydrogen-acceptor ability of the anions
(IÀ <BrÀ <ClÀ). It also reflects the size and shape comple-
mentarities of the interlocked binding cavity generated by
R-2 to the chloride anion. All these features suggest that the
macrocycle isophthalamide (HC and HD) and thread triazole
proton encircle the chloride anion through cooperative hy-
drogen-bonding interactions, which leads the conformational
alternation of the macrocycle of R-2.
Table 1. Stability constants [MÀ1] for 1:1 complexes of R-2 with various
anions in acetonitrile at 298 K.
Anion
R-2
Dd
K[a]
ClÀ
BrÀ
IÀ
0.70[b]
0.61[c]
0.16[d]
312.07
34.50
12.15
[a] Errors<10%. [b] Changes of chemical shift [ppm] of proton C after
addition of 50 equiv of the chloride anion. [c] Changes of chemical shift
[ppm] of proton C after addition of 162 equiv of the bromide anion.
[d] Changes of chemical shift [ppm] of proton C after the addition of
140 equiv of the iodide anion.
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Y. Li et al.
64.46, 63.23, 48.44, 34.43, 31.56, 29.01 ppm; MS (EI): m/z 587 [M]+; ele-
mental analysis calcd (%) for C40H49N3O : C 81.73, H 8.40, N 7.15;
found: C 81.68, H 8.46, N 6.91.
Conclusions
We have successfully demonstrated an acid/base and chlo-
ride anion dual-response [2]rotaxane. In this system, the
shuttling of the macrocycle along the thread driven by acid/
base and the conformational alternation of the macrocycle
driven by anions has been realized. Combination of the mul-
tiple hydrogen-bonding interactions with the anion-con-
trolled translational isomerism in interlocked molecules has
been well carried out. In addition, we have also demonstrat-
ed that the click reaction is not only a valuable tool to fabri-
cate the functional rotaxane, but also the generated 1,2,3-tri-
azole can participate in hydrogen-bond interactions with the
macrocycle, which provides a novel recognition site. Inter-
estingly, the macrocycle is able to interact with the ammoni-
um cation and the triazole recognition station simultaneous-
ly by a short bridge under acidic conditions, whereas the
macrocycle of [2]rotaxane with a longer bridge only locates
on the ammonium region. Our work highlights the excellent
hydrogen-bonding capacity of triazole and provides a new
recognition system to construct complex structures.
Compound 3: A solution of compound 2 (2.2 g, 3.8 mmol) in ethyl ace-
tate and methanol (200 mL, acetate/methanol 1:1) was heated under
reflux in the presence of Pd/C (200 mg) under hydrogen. The reaction
was monitored by TLC until it was completed. The mixture was filtered
and the solvent was removed under vacuum. The residue was purified by
chromatography (CH2Cl2/MeOH 15:1) to afford compound 3 almost
quantitatively. 1H NMR (400 MHz, MeOD, 258C, TMS): d=7.26 (d, J=
7.79 Hz, 6H), 7.08 (d, J=7.25 Hz, 8H), 6.83 (d, J=8.44 Hz, 2H), 4.10 (t,
J=5.49 Hz, 2H), 3.13 (t, J=6.24 Hz, 2H), 2.11 (m, 2H), 1.31 ppm (s,
27H); 13C NMR (400 MHz, MeOD, 258C, TMS): d=159.23, 151.10,
147.06, 142.82, 134.73, 133.25, 126.62, 115.66, 67.61, 65.77, 40.15, 36.57,
33.22, 29.83 ppm; MS (EI): m/z 561 [M]+; elemental analysis calcd (%)
for C40H51NO: C 85.51, H 9.15, N 2.49; found: C 85.77, H 8.82, N 2.22.
Compound 5: A solution of compound 4[26] (9 g, 31.6 mmol) and hydro-
quinone (5.2 g, 47.2 mmol) in dried acetonitrile (250 mL) was heated
under reflux in the presence of anhydrous K2CO3 (17.4 g 126.3 mmol)
under nitrogen. The reaction was monitored by TLC until it was complet-
ed. The mixture was filtered and the solvent was removed under vacuum.
The crude product was dissolved in CH2Cl2 and washed with water three
times. The combined organic layers were dried over Na2SO4. After re-
moval of the solvent under reduced pressure, the residue was purified by
chromatography (CH2Cl2/MeOH 30:1) to afford compound 5 as a white
solid (4.3 g, 43%). 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.88 (s,
1H), 7.83 (d, J=8.68 Hz, 2H), 6.99 (d, J=8.68 Hz, 2H), 6.79–6.74 (m,
4H), 4.05 (t, J=6.44 Hz, 2H), 3.91 (t, J=6.4 Hz, 2H), 1.89–1.76 (m, 4H),
1.58–1.53 ppm (m, 4H); 13C NMR (400 MHz, CDCl3, 258C, TMS): d=
191.07, 164.39, 153.36, 149.68, 132.18, 129.92, 116.17, 115.76, 115.58,
114.92, 68.62, 68.40, 29.43, 29.14, 25.98, 25.93 ppm; MS (EI): m/z 314
[M]+; elemental analysis calcd (%) for C19H22O4: C 72.59, H 7.05; found:
C 72.33, H 7.05.
Experimental Section
General methods: Unless stated otherwise, all reagents were purchased
from Aldrich Chemicals and used without further purification. Solvents
were purified according to the standard laboratory methods. Chromato-
graphic separations were performed on silica gel (200–300 mesh). Reac-
tions were monitored by TLC, which was performed on glass plates
coated with SiO2 F254 and visualized by ultraviolet (UV) light (l=254
and l=365 nm). 1H and 13C NMR spectra were recorded on Bruker AV
400 instruments at a constant temperature of 258C. All chemical shifts
are reported in parts per million (ppm) from low to high field and refer-
enced to TMS. MALDI-TOF mass spectrometric measurements were
performed on Bruker Biflex III MALDI-TOF.
Compound 1: Tris(p-tert-butylphenyl)(4-hydroxyphenyl)methane[25] (2.5 g,
4.96 mmol) and 1,3-dibromopropane (3 g, 14.9 mmol) were dissolved in
dry acetonitrile (100 mL) and refluxed overnight in the presence of anhy-
drous K2CO3 (2.05 g, 14.9 mmol) under nitrogen. The mixture was fil-
tered and the solvent was removed under vacuum. The crude product
was dissolved in CH2Cl2 and washed with water three times. The com-
bined organic layers were dried over Na2SO4. After removal of the sol-
vent under reduced pressure, the residue was purified by chromatography
(petroleum ether/CH2Cl2 2:1) to afford compound 1 as a white solid
(3.0 g, 97%). 1H NMR (400 MHz, CDCl3, 258C, TMS): d=7.23 (d, J=
7.79 Hz, 6H), 7.08 (d, J=7.93 Hz, 8H), 6.77 (d, J=8.21 Hz, 2H), 4.08 (t,
J=5.72 Hz, 2H), 3.60 (t, J=6.4 Hz, 2H), 2.32–2.89 (m, 2H), 1.30 ppm (s,
27H); 13C NMR (400 MHz, CDCl3, 258C, TMS): d=156.60, 148.43,
144.26, 140.00, 132.43, 130.88, 124.19, 113.13, 65.24, 63.20, 34.43, 32.62,
31.55, 30.26 ppm; MS (EI): m/z 626 [M]+; elemental analysis calcd (%)
for C40H49BrO: C 76.78, H 7.89; found: C 76.53, H 7.85.
Compound 6: A mixture of compound 5 (3 g, 9.6 mmol) and propargyl
bromide (1.7 g, 14.3 mmol) in dried acetonitrile (100 mL) was heated
under reflux for 6 h in the presence of anhydrous K2CO3 (5.3 g
38.2 mmol) under nitrogen. The mixture was filtered and the solvent was
removed under vacuum. The crude product was dissolved in CH2Cl2 and
washed with water three times. The combined organic layers were dried
over Na2SO4. After removal of the solvent under reduced pressure, the
residue was purified by chromatography (CH2Cl2) to afford compound 6
(3.1 g, 91%). 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.88 (s, 1H),
7.82 (d, J=8.72 Hz, 2H), 6.99 (d, J=8.72 Hz, 2H), 6.93–6.89 (m, 2H),
6.85–6.82 (m, 2H), 4.64 (s, 2H), 4.05 (t, J=6.44 Hz, 2H), 3.93 (t, J=
6.4 Hz, 2H), 2.50 (s, 1H), 1.87–1.79 (m, 4H), 1.57–1.53 ppm (m, 4H);
13C NMR (400 MHz, CDCl3, 258C, TMS): d=190.77, 164.22, 153.99,
151.69, 132.00, 129.84, 116.16, 115.36, 114.79, 79.01, 75.39, 68.33, 68.28,
56.63, 29.30, 29.03, 25.88, 25.82 ppm; MS (EI): m/z 352 [M]+; elemental
analysis calcd (%) for C22H24O4: C 74.98, H 6.86; found: C 74.75, H 6.89.
Compound 7: A solution of the compound 6 (0.853 g, 2.42 mmol) and 3
(1.3 g, 2.32 mmol) in toluene (50 mL) was heated under reflux for 30 h by
using a Dean–Stark apparatus. The solvent was removed under reduced
pressure after the reaction was cooled to room temperature. The residue
was dissolved in methanol (150 mL), then NaBH4 (2 g, 52.8 mmol) was
added cautiously at 08C. The mixture was stirred at room temperature
for a further 4 h. Water was added to quench the excess NaBH4. The sol-
vent was evaporated off, and the residue was extracted with CH2Cl2. The
combined organic layers were dried over Na2SO4. After concentrated in
vacuo, the crude product was purified by chromatography (CH2Cl2/
MeOH 30:1) to afford compound 7 as slightly yellow solid (1.2 g, 58%).
1H NMR (400 MHz, CDCl3, 258C, TMS): d=7.22 (d, J=8.44 Hz, 8H),
7.08 (d, J=8.52 Hz, 8H), 6.91 (d, J=9.12 Hz, 2H), 6.85–6.82 (m, 4H),
6.75 (d, J=8.80 Hz, 2H), 4.63 (s, 2H), 4.01 (t, J=6.04 Hz, 2H), 3.96–3.90
(m, 4H), 3.75 (s, 2H), 2.82 (t, J=6.84 Hz, 2H), 2.50 (s, 1H), 1.98 (t, J=
6.36 Hz, 2H), 1.80–1.79 (m, 4H), 1.52 ppm (m, 4H); 13C NMR (400 MHz,
CDCl3, 258C, TMS): d=158.24, 156.80, 154.03, 151.66, 149.64, 148.31,
147.02, 144.26, 139.58, 132.29, 132.08, 130.81, 129.42, 129.18,
124.12,116.16, 115.37, 114.47, 113.05, 79.01, 75.41, 68.40, 67.87, 66.20,
Compound 2: A mixture of compound 1 (2.9 g, 4.64 mmol) and sodium
azide (0.9 g, 13.9 mmol) in DMF was heated overnight at 808C. The mix-
ture was filtered and the solvent was evaporated. The crude product was
dissolved in CH2Cl2 and washed with water several times. The combined
organic layers were dried with Na2SO4, and the solvents were evaporated
to yield a white solid. Chromatography on silica gel (petroleum ether/
CH2Cl2 2:1) afforded 2 in 95% yield. 1H NMR (400 MHz, CDCl3, 258C,
TMS): d=7.23 (d, J=7.81 Hz, 6H), 7.08 (d, J=7.68 Hz, 8H), 6.76 (d, J=
8.09 Hz, 2H), 4.02 (t, J=5.78 Hz, 2H), 3.51 (t, J=6.68 Hz, 2H), 2.05–
2.02 (m, 2H), 1.30 ppm (s, 27H); 13C NMR (400 MHz, CDCl3, 258C,
TMS): d=156.62, 148.44, 144.29, 140.03, 132.45, 130.90, 124.19, 113.13,
13260
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 13253 – 13262

A Dual-Response [2]Rotaxane
FULL PAPER
63.73, 63.12, 56.62, 53.42, 46.35, 34.68, 34.35, 31.49, 31.32, 29.69, 29.37,
29.32, 25.97 ppm; MS (MALDI-TOF): m/z: 897.5 [M]+, 920.5 [M+Na]+,
936.5 [M+K]+; elemental analysis calcd (%) for C62H75NO4: C 82.90, H
8.42, N 1.56; found: C 82.65, H 8.34, N 1.52.
115.89, 115.61, 115.19, 113.08, 68.38, 67.94, 65.99, 63.96, 63.19, 62.54,
52.26, 47.50, 46.17, 34.72, 34.41, 31.76, 31.51, 31.34, 30.05, 29.29, 29.13,
26.60, 25.81, 26.78 ppm; MS (MALDI-TOF): m/z: 1486.9 [MÀPF6]+; ele-
mental analysis calcd (%) for C102H125N4F6O5P: C 75.06, H 7.72, N 3.43;
found: C 75.41, H 7.88, N 3.80.
Compound 8: Compound 7 (500 mg, 0.56 mmol) was dissolved in acetoni-
trile and a few drops of trifluroacetic acid were added. After 1 hour, the
solvent was removed under vacuo. The residue was dissolved in a mixture
of acetone and water. Then the aqueous of NH4PF6 (136 mg, 0.84 mmol)
was added. The mixture was stirred for 1 h and then the acetone was
evaporated off. The aqueous solution was extracted with CH2Cl2 several
times. The collected organic layers were dried over Na2SO4, filtered, and
concentrated in vacuo to yield 8 as a yellow solid (584 mg, 83%).
1H NMR (400 MHz, CDCl3, 258C, TMS): d=7.30 (d, J=8.40 Hz, 2H),
7.23 (d, J=8.40 Hz, 6H), 7.10–7.05 (m, 8H), 6.89–6.83 (m, 6H), 6.70 (d,
J=8.72 Hz, 2H), 4.63 (s, 2H), 4.06 (s, 2H), 4.03–4.02 (m, 2H), 3.91–3.88
(m, 4H), 3.15–3.13 (m, 2H), 2.49 (s, 1H), 2.17–2.16 (m, 2H), 1.79–1.76
(m, 4H), 1.50 (m, 4H), 1.29 ppm (s, 27H).
Rotaxane R-H-2 and thread T-H-2: [Cu
0.56 mmol) was added to a solution of compound 2 (330 mg, 0.56 mmol),
compound 10 (484.7 mg, 0.57 mmol), and macroycle (300 mg,
ACHTUNGRTEN(UNGN MeCN)4]BF6 (177 mg,
1
0.56 mmol) in dry CH2Cl2. The mixture was stirred at room temperature
under nitrogen for 24 h. After concentration, the crude was purified by
column chromatography (CH2Cl2/MeOH 30:1) to afford rotaxane R-H-2
(353 mg, 32%) and thread R-H-2 (394 mg, 49%).
Rotaxane R-H-2: 1H NMR (400 MHz, CD3CN, 258C, TMS): d=7.96 (d,
J=7.6 Hz, 2H), 7.92 (s, 1H), 7.87 (s, 1H), 7.46 (m, 3H), 7.30(d,
J=8.4 Hz, 14H), 7.15 (m, 14H), 7.09 (d, J=8.8 Hz, 2H), 7.04 (m, 6H),
6.74 (m, 4H,), 6.64 (m, 2H), 6.55 (d, J=8.4 Hz, 4H), 4.88 (s, 2H), 4.55–
4.50 (m, 2H), 4.44 (t, J=6.8 Hz, 2H), 4.20–4.15 (m, 2H), 4.00–3.97 (m,
4H), 3.90–3.81 (m, 6H), 3.76–3.62ACTHNUTRGENUGN(m, 6H), 3.58–3.48 (m, 6H), 3.14 (m,
Compound 9: Compound 9 was synthesized from 4-hydroxy-1-(2’-propy-
nyloxy)benzene and compound 3 by using the same procedure as de-
scribed for the preparation of compound 7. 1H NMR (400 MHz, CDCl3,
258C, TMS): d=7.37 (d, J=7.71 Hz, 2H), 7.22 (d, J=7.73 Hz, 6H), 7.07
(d, J=7.83 Hz, 8H), 6.94 (d, J=7.95 Hz, 2H), 6.71 (d, J=8.26 Hz, 2H),
4.62 (s, 2H), 3.99 (m, 2H), 3.87 (s, 2H), 2.92 (t, J=6.08 Hz, 2H), 2.45 (s,
1H), 2.11–2.10 (m, 2H), 1.30 ppm (s, 27H); 13C NMR (400 MHz, CDCl3,
258C, TMS): d=157.19, 156.67, 148.41, 144.29, 144.25, 139.83, 132.35,
130.83, 130.13, 124.14, 115.10, 113.07, 78.59, 75.65, 65.93, 63.16, 55.93,
52.60, 45.80, 34.39, 31.49, 31.32 ppm; MS (EI): m/z 706 [M]+; elemental
analysis calcd (%) for C50H59NO2 : C 85.06, H 8.42, N 1.98; found: C
85.32, H 8.29, N 2.15.
2H), 2.20 (t, J=6.4 Hz, 2H), 2.11 (m, 2H), 1.27 ppm (s, 54H); 13C NMR
(400 MHz, CDCl3, 258C, TMS): d=166.70, 158.92, 156.89, 156.33, 155.92,
149.82, 148.44, 148.40, 146.87, 144.16, 144.12, 142.93, 140.62, 140.13,
134.64, 132.44, 132.40, 131.66, 131.49, 131.38, 130.79, 130.69, 130.20,
129.26, 124.22, 124.13, 123.21, 122.76, 115.16, 114.23, 113.07, 70.72, 70.65,
70.53, 67.18, 64.16, 64.10, 63.78, 63.16, 63.14, 61.14, 51.99, 47.53, 45.96,
43.44, 34.69, 34.36, 31.47, 31.34, 31.31, 30.05, 26.31 ppm; MS (MALDI-
TOF): m/z: 1827.5 [MÀPF6]+; elemental analysis calcd (%) for
C120H143N6F6O10P: C 73.02, H 7.25, N 4.26; found: C 73.23, H 7.20, N
4.34.
Thread T-H-2: 1H NMR (400 MHz, CD3CN, 258C, TMS): d=7.83 (s,
1H), 7.36 (d, J=8.8 Hz, 2H), 7.29 (d, J=8.0 Hz, 14H), 7.16 (m,18H),
7.05 (d, J=8.0 Hz, 2H), 6.80–6.72 (m, 4H), 5.14 (s, 2H), 4.53 (t, J=
6.8 Hz, 2H), 4.11 (s, 2H), 4.03 (t, J=5.6 Hz, 2H), 3.92 (m, 2H) 3.20 (t,
J=6.4 Hz, 2H), 2.29 (m, 2H), 2.10 (m, 2H), 1.27 ppm (s, 54H); 13C NMR
(400 MHz, CDCl3, 258C, TMS):d=159.09, 156.34, 155.99, 148.44, 144.26,
144.19, 143.37, 140.48, 14.019, 132.46, 132.33, 131.60, 130.83, 130.77,
124.23, 124.18, 123.96, 122.70, 115.40, 113.06, 64.01, 63.17, 34.71, 34.38,
31.52, 31.35, 29.96 ppm; MS (MALDI-TOF): m/z 1293.7 [MÀPF6]+; ele-
mental analysis calcd (%) for C90H109N4F6O3P: C 75.08, H 7.63, N 3.89;
found: C 74.94, H 7.80, N 4.05.
Compound 10: Compound 10 was synthesized by using the same proce-
dure as described for the preparation of compound 8. 1H NMR
(400 MHz, CDCl3, 258C, TMS): d=7.34 (d, J=7.86 Hz, 2H), 7.23 (d, J=
7.87 Hz, 6H), 7.10–7.05 (m, 8H), 6.95 (d, J=8.01 Hz, 2H), 6.68 (d, J=
8.36 Hz, 2H), 4.63 (s, 2H), 4.17 (s, 2H), 4.02 (m, 2H), 3.24 (m, 2H), 2.42
(s, 1H), 2.18 (m, 2H), 1.30 ppm (s, 27H).
Rotaxane R-H-1 and thread T-H-1: A mixture of compound 2 (290.6 mg,
0.50 mmol), compound 491 mg, 0.47 mmol)
8
(
,
macroycle 1[23]
(264.3 mg, 0.49 mmol), and [CuACHTUNTGREN(NUNG MeCN)4]BF6 (148.3 mg, 0.47 mmol) was
stirred in dry CH2Cl2 at room temperature under nitrogen for 24 h. After
removal of the solvent, the crude product was purified by column chro-
matography (CH2Cl2/MeOH 30:1) to afford rotaxane R-H-1 (356 mg,
35%) and thread T-H-1 (383 mg, 50%).
Rotaxane R-H-1: 1H NMR (400 MHz, CD3CN, 258C, TMS): d=7.96 (d,
J=8.17 Hz, 2H), 7.90 (s, 1H), 7.75 (s, 1H), 7.52 (t, J=7.20 Hz, 1H), 7.35
(m, 2H), 7.29 (d, J=7.60 Hz, 12H), 7.25 (m, 2H), 7.14 (m, 22H), 6.86–
6.77 (m, 6H), 6.72–6.70 (m, 8H), 4.99 (s, 2H), 4.47 (t, J=6.80 Hz, 2H),
4.40–4.38 (m, 4H), 3.95 (m, 4H), 3.92–3.85 (m, 10H), 3.70 (m, 4H), 3.61–
3.57 (m, 2H), 3.48–3.46 (m, 4H), 3.36–3.32 (m, 2H), 3.06 (m, 2H), 2.24
(t, J=6.40 Hz, 2H), 2.06 (m, 2H), 1.70 (m, 4H), 1.44 (m, 4H), 1.27 ppm
(s, 54H); 13C NMR (400 MHz, CDCl3, 258C, TMS): d=166.76, 160.44,
156.84, 156.41, 156.03, 153.88, 152.46, 148.56, 144.26, 140.74, 140.36,
134.75, 132.55, 132.25, 131.81, 131.70, 130.91, 130.85, 130.79, 130.74,
129.39, 129.22, 128.41, 124.34, 124.25, 122.92, 122.40, 116.02, 115.64,
115.12, 114.37, 113.17, 70.90, 70.82, 70.70, 68.58, 68.30, 67.18, 64.27, 64.21,
64.11, 63.91, 63.29, 63.26, 62.78, 62.75, 52.22, 47.63, 47.57, 46.17, 43.60,
35.00, 34.86, 34.81, 34.66, 34.60, 34.48, 34.31, 31.83, 31.77, 31.58, 31.42,
30.13, 29.88, 29.44, 29.24, 27.92, 26.41, 26.05, 25.96, 25.72, 25.47, 22.83,
21.64 ppm; MS (MALDI-TOF): m/z: 2041.5 [MÀPF6ÀH+Na]+, 2057.5
[MÀPF6ÀH+K]+; elemental analysis calcd (%) for C132H159N6F6O12P: C
73.20, H 7.35, N 3.88; found: C 73.59, H 7.19, N 4.15.
Thread T-H-1: 1H NMR (400 MHz, CD3CN, 258C, TMS): d=7.76 (s,
1H), 7.33–7.28 (m, 14H), 7.16–7.09 (m, 16H), 6.90–6.85 (m, 4H), 6.79–
6.70 (m, 6H), 5.02 (s, 2H), 4.52 (t, J=6.76 Hz, 2H), 4.06 (s, 2H), 4.02 (t,
J=4.97 Hz, 2H), 3.95 (t, J=6.14 Hz, 2H), 3.89(t, J=5.78 Hz, 4H), 3.16 (t,
J=6.8 Hz, 2H), 2.30–2.27 (m, 2H), 2.08 (m, 2H), 1.75–1.71 (m, 4H), 1.48
(m, 4H), 1.27 ppm (s, 54H); 13C NMR (400 MHz, CDCl3, 258C, TMS):
d=159.90, 156.32, 156.07, 153.82, 152.30, 148.48, 144.45, 144.19, 140.47,
140.29, 132.49, 132.40, 131.01, 130.84, 130.80, 124.19, 124.03, 123.46,
Acknowledgements
This work was supported by the National Nature Science Foundation of
China (20531060, 20831160507, 10874187, 20873155, and 20721061) and
the National Basic Research 973 Program of China, NSFC-DFG joint
fund (TRR 61).
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Received: July 3, 2009
Published online: October 28, 2009
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