Unsymmetric Bistable [c2]Daisy Chain Rotaxanes which Combine Two Types of Electroactive Stoppers

Article abstract of DOI:10.1002/ejoc.201900179

Mechanically interlocked molecules (MIMs) have emerged as intriguing building blocks for the construction of stimuli-responsive devices and materials. A particularly interesting and well-implemented subclass of MIMs is composed of symmetric bistable [c2]daisy chain rotaxanes. Topologically, they consist in the double thread of two symmetric macrocycles that are covalently linked to an axle bearing two switchable stations and a bulky stopper to avoid unthreading. Herein we report the synthesis and characterization of a series of unsymmetric bistable [c2]daisy chain rotaxanes that present two different electroactive units as stoppers (an electron donor triarylamine and an electron acceptor perylene bisimide unit). Using a combination of 1D and 2D NMR along with cyclic voltammetry, we demonstrate that the pH actuation of the mechanical bond can be used to modulate the electrochemical properties of the bistable [c2]daisy chain rotaxanes when switching between the contracted and extended forms.

Full text of DOI:10.1002/ejoc.201900179

A Journal of
Accepted Article
Title: Unsymmetric bistable [c2]daisy chain rotaxanes which combine
two types of electroactive stoppers
Authors: Adrian Wolf, Juan-José Cid, Emilie Moulin, Frédéric Niess,
Guangyan Du, Antoine Goujon, Eric Busseron, Adrian Ruff,
Sabine Ludwigs, and Nicolas Giuseppone
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to ensure accuracy of information. The authors are responsible for the
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900179
Link to VoR: http://dx.doi.org/10.1002/ejoc.201900179
Supported by

European Journal of Organic Chemistry
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Unsymmetric bistable [c2]daisy chain rotaxanes which combine
two types of electroactive stoppers
[
a]
[a]
[a]
[a]
[a]
[a]
Adrian Wolf, Juan-José Cid, Emilie Moulin,* Frédéric Niess, Guangyan Du, Antoine Goujon,
[
a]
[b, c]
[b]
[a]
Eric Busseron, Adrian Ruff,
Sabine Ludwigs and Nicolas Giuseppone*
Abstract: Mechanically interlocked molecules (MIMs) have emerged
transition metal ions binding selectively the two stations with
different coordination geometries. This seminal work inspired
several other groups (including us) to reproduce the natural
contractile motion of muscles up to the macroscopic level.[
Symmetric [c2]daisy chain rotaxanes were also used towards
functional devices such as logic gates[ or even plasmonic
actuators.[16] However, the design of unsymmetric [c2]daisy
chain rotaxanes remains unexplored. In this paper, we describe
the syntheses and the pH-controlled contraction/extension of
unsymmetric [c2]daisy chain rotaxanes with two different
electroactive stoppers – an electron donor (Figure 1, blue) and
an electron acceptor (red). The donor stoppers consist of
triarylamine units (TAAs),[17–23] and the acceptor stoppers of
unsymmetrical 1,7-dipyrrolidinyl-substituted perylene diimides
(PDIs).[24–29] This interlocked structure presents two molecular
stations – an ammonium group (orange in Figure 1) and a
triazolium group (purple in Figure 1) – with different affinities for
the macrocycle. The mechanical actuation of the [c2]daisy chain
as intriguing building blocks for the construction of stimuli-responsive
devices and materials.
implemented subclass of MIMs is composed of symmetric bistable
c2]daisy chain rotaxanes. Topologically, they consist in the double
A
particularly interesting and well-
5–14]
[
15]
thread of two symmetric macrocycles that are covalently linked to an
axle bearing two switchable stations and a bulky stopper to avoid
unthreading. Here we report the synthesis and characterization of a
series of unsymmetric bistable [c2]daisy chain rotaxanes that
present two different electroactive units as stoppers (an electron
donor triarylamine and an electron acceptor perylene bisimide unit).
Using
a combination of 1D and 2D NMR along with cyclic
voltammetry, we demonstrate that the pH actuation of the
mechanical bond can be used to modulate the electrochemical
properties of the bistable [c2]daisy chain rotaxanes when switching
between the contracted and extended forms.
is based on a strategy developed by Coutrot[30] and already used
Introduction
in our laboratory.[8–10,15] In the protonated state, the macrocycles
reside around the ammonium stations via ion-dipole and
hydrogen bonding interactions, while, in the deprotonated state,
the macrocycles shuttle to the triazolium stations, which are
favored over the amine groups. We demonstrate hereafter,
using optical spectroscopy and cyclic voltammetry, that a switch
between the contracted and the extended forms induces
modifications of the optical and electronic properties of the
mechanically interlocked rotaxanes.
Control of the mechanical bond has been a source of inspiration
for molecular and supramolecular chemists over the past thirty
years.[1] In particular, the possibility to reach large intramolecular
motions by switching interlocked molecules between different
stations appears of first interest to access molecular
machines.[ For instance, in 2000, Sauvage designed the first
topologically double-threaded rotaxane which mimics (at
nanoscale) the function of a sarcomere in muscular tissues (at
microscale).[4] The so-called [c2]daisy chain rotaxane proved to
contract or extend by 1.8 nm because of the interplay of
2,3]
[
a]
Dr. A. Wolf, Dr. J.-J. Cid, Dr. E. Moulin, Dr. F. Niess, Dr. G. Du, Dr.
A. Goujon, Dr. E. Busseron, Prof. Dr. N. Giuseppone
SAMS research group, Institut Charles Sadron, CNRS, University of
Strasbourg,
23 rue du Loess, BP 84087,
67034 Strasbourg Cedex 2, France
E-mails: emoulin@unistra.fr; giuseppone@unistra.fr
http://sams.ics-cnrs.unistra.fr/
[
[
b]
c]
Dr. A. Ruff, Prof. Dr. S. Ludwigs
IPOC-Functional Polymers, Institute of Polymer Chemistry,
Universität Stuttgart,
Pfaffenwaldring 55,
70569 Stuttgart, Germany
Dr. A. Ruff
present address: Analytical Chemistry – Center for Electrochemical
Sciences (CES), Faculty of Chemistry and Bioelectrochemistry,
Ruhr University Bochum, Universitätsstr. 150, 44780 Bochum,
Germany
Figure 1. (a) General representation of the mechanical actuation of an
unsymmetric [c2]daisy chain rotaxane incorporating electron donor (blue) and
electron acceptor (red) stoppers; (b) Molecular structures of the pH-switchable
[
c2]daisy chain rotaxanes 16Ext-Cont and 17Ext-Cont
.
Supporting information for this article is given via a link at the end of
the document.
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European Journal of Organic Chemistry
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Results and Discussion
80 °C for 25 hours, we obtained azido-functionalized perylene
diimide 10 in 70 % yield.
Synthesis of unsymmetric [c2]daisy chain rotaxanes
The general synthetic route to access mechanically interlocked
molecules 16 and 17 (Figure 1b) involves the introduction of
triarylamines 2 or 3 (Scheme 1) and perylene diimides 7 or 10
[
31]
(
a
(
Scheme 2) on the pseudo [c2]daisy chain rotaxane 11 using
copper catalyzed [3+2] Huisgen cycloaddition reaction
Scheme 3). The corresponding detailed syntheses are
described hereafter.
Triarylamine 3 was prepared in three steps and excellent yields
from 4-nitro-N,N-bis[4-(benzyloxy)phenyl]-phenylamine following
previously described protocols of the literature.[15,32] On the other
hand, N,N-bis(4-(benzyloxy)phenyl) benzene-1,4-diamine 1 was
converted into compound 2 in a good yield by a diazotation
reaction using sodium nitrite in the presence of hydrochloric acid
and followed by aromatic nucleophilic substitution (S
N
Ar) using
sodium azide in deionized water (Scheme 1).
Scheme 1. Synthetic pathways to reach azido-triarylamine derivatives 2 and 3.
Compounds 7 and 10 were accessed in five and seven steps
respectively, in moderate to good yields starting from
commercially available perylene-3,4:9,10-tetracarboxylic acid
dianhydride (PTCDA) (Scheme 2). Bromination of PTCDA
according to literature procedures[33] afforded a crude mixture of
the 1,6 : 1,7 : 1,6,7 bromo-isomers in a ratio of 24 : 70 : 6 as
indicated by 1H NMR spectroscopy in deuterated sulfuric acid
Scheme 2. Synthetic route towards unsymmetric perylene bisimide 7 and 10.
The reaction pathways to access (non-methylated) triazole
rotaxanes 12-15 are shown in Scheme 3. In the one pot version
(Scheme 3a), the bisalkynyl-substituted pseudorotaxane 11[
was reacted with azido-substituted triarylamine 2 or 3 and azido-
substituted perylene 7 or 10 via [3+2] Huisgen cycloaddition
using a 1:1:1 (11 / (2 or 3) / (7 or 10)) stoichiometric ratio.
Unfortunately, all reaction conditions used to couple compound
7 failed probably due to the strong delocalization of electrons in
the perylene ring making the azido group unreactive. The
reactions involving 10 were carried out in the presence of 2,6-
lutidine and tetrakisacetonitrile copper(I) hexafluorophosphate in
dichloromethane at room temperature for 3–4 days. They
satisfyingly gave the desired triarylamine-perylene diimide (TAA-
PDI) systems 14 and 15 in 25 % and 10 % isolated yields,
respectively. The difficulty of this one-pot approach to prepare
unsymmetrical systems 14 and 15 relied on the purification of
the crude reaction mixtures, which contained at least five
different species on TLC. Several factors account for this very
(
96–98 % w/w solution in D
diimidated using n-dodecylamine in N-methylpyrrolidinone
NMP) in the presence of acetic acid at 120 °C for 19 hours. An
2
O). The crude mixture was then
30,31]
(
isomeric mixture of 1,6 and 1,7 isomers of diimide 4 (1,6:1,7-4)
in a ratio of about 1 : 4 (estimated by 1H NMR spectroscopy)
was obtained in 48 % yield over two steps. The isomers could
not be separated at this stage by flash column chromatography
and thus, the mixture was used as such in the next step.
N
Subsequent S Ar of the bromide groups by pyrrolidine provided
dipyrrolidinated diimide 1,6-5 and 1,7-5 in 13 % and 38 % yields,
respectively (the two isomers were separated by column
chromatography at that stage). Compound 1,7-5 was then
mono-saponified using potassium hydroxide in tert-butanol
under reflux for 10 minutes to give the key intermediate 6 in
29]
6
3 % isolated yield.[ Compound 7 was then obtained in one
step and 85
aminophenylazide.
%
yield from
Alternatively, imidation of with p-
6
via imidation with 4-
[
34]
6
phenylenediamine gave unsymmetrical PDI 8 in quantitative
yield, which was further chloroacetylated to form compound 9 in
complex mixture: 1) the presence of stereoisomers of the
[c2]daisy chain unit;[
31]
2) the formation of mono-coupled
8
9 % yield using equimolar amounts of 2-chloroacetyl chloride
cycloadducts between 10 and 11 as well as between 2 or 3 and
11; 3) the formation of bis-coupled cycloadducts between 10 and
11 as well as between 2 or 3 and 11; and 4) the presence of
and triethylamine in dichloromethane. Finally, after stirring
compound 9 with sodium azide in N,N'-dimethylformamide at
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European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
residual amounts of unreacted starting materials. Purification of
was obtained in 30% yield after an easier chromatography
column.
14 and 15 was however accomplished by conventional flash
column chromatography on silica gel. First, elution with pure
dichloromethane was used to remove unreacted triarylamine 2
Finally, the triazole groups in 14 and 15 were selectively
methylated in the 3 position using a mixture of methyl iodide and
dichloromethane over 4 days, followed by anion exchange using
ammonium hexafluorophosphate to give the extended systems
or
dichloromethane, methanol and toluene starting with a ratio of
00 : 0 : 2 and increasing polarity slowly up to 100 : 5 : 2 allowed
3 and PDI 10. Then, a ternary eluent mixture of
Ext
Ext
1
16 and 17 in 80 % and 94 % yields, respectively (Scheme 4,
top). Deprotonation of these compounds to the contracted form,
16Cont and 17Cont, was accomplished using a biphasic mixture of
0.1 M aqueous sodium hydroxide and dichloromethane at room
temperature for 1 hour and proceeded in 95 % yield (Scheme 4,
bottom). Compounds 16Cont and 17Cont proved less soluble in
the sequential removal of 1) [2+11+2] or [3+11+3];[15] 2) mono-
coupled cycloadducts ([2+11] or [3+11]), and 3) desired
compound 14 or 15. Further elution with increasing polarity
afforded PDI derivatives [10+11] and [10+11+10].
Alternatively, we envisioned a sequential approach involving first
the formation of mono-coupled cycloadducts [2+11], [3+11] or
acetonitrile than their extended forms 16Ext and 17Ext
.
[
10+11] as intermediates (Scheme 3b for [10+11]). In this
stepwise approach, 4.7 equivalents of 11 were first stirred with
either one equivalent of 2, 3 or 10 for three days in the presence
of one equivalent of tetrakisacetonitrile copper(I) hexafluoro-
phosphate and 2,6-lutidine in dichloromethane to give the
intermediates [2+11], [3+11] or [10+11] in 32 %, 19 % and 32 %
isolated yields, respectively. For the synthesis of [2+11] and
Characterization of [c2] daisy chain rotaxanes 16 and 17
All compounds were characterized by H and 13C NMR and by
either ESI or MALDI-TOF mass spectroscopy (see Experimental
Section and SI for 1H and 13C NMRs of key compounds). In
order to probe the contraction/extension event of the
unsymmetric [c2] daisy chain rotaxanes, a precise determination
of the 1H signals of compounds 16 and 17 is necessary. This
was achieved thanks to a combination of standard 1D and 2D
NMR techniques on most of the synthetic intermediates and
particularly on compounds 2, 3, 10, 14 and 15. For compounds 2
1
[
3+11], the side-products resulted only in excess quantities of 11
and a small amount of [2+11+2] or [3+11+3] (see SI). For the
synthesis of [10+11], bis-coupled cycloadducts [10+11+10] could
not be detected by LC-MS. The second step was then tested
1
between [10+11] and
2
which were mixed in
a
1
:
1
and 3, the H NMR spectra of the aromatic region was assigned
stoichiometric ratio in dichloromethane for three days in the
presence of an equimolar amount tetrakisacetonitrile copper(I)
hexafluorophosphate and 2,6-lutidine. In this way, compound 15
based mainly on the integration of the aromatic proton signals of
the triarylamine unit and on H- H COSY NMR (Figure 2 and SI).
1
1
Scheme 3. a) One-pot synthetic route towards unsymmetrical [c2] daisy chain rotaxanes 12-15; b) Sequential synthetic route towards unsymmetrical [c2] daisy
chain rotaxane 15.
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European Journal of Organic Chemistry
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Scheme 4. Synthetic route towards unsymmetric [c2] daisy chain rotaxanes 16 and 17 and their subsequent acid/base controlled actuation.
Figure 2. Partial 1H NMR spectra (400 MHz, CDCl
a) and 3 (b) with chemical shift assignments.
3
, 25 °C) of compounds 2
(
Figure 3. Partial 1H NMR spectra (400 MHz, CDCl
, 25 °C) of compound 10
3
with chemical shift assignments a) in the low-field region from 8.6 to 7.0 ppm
and b) in the high-field region from 4.5 to 0.5 ppm.
For both compounds, the aromatic protons of the Bn group
showed a multiplet between 7.50 and 7.30 ppm while the two
doublet peaks integrating for 4 each at  ~ 7.04 and 6.92 ppm
were assigned to the phenyl ring B.[35] For compound 3, one
doublet with an integral of 2 was found strongly shifted towards
the low-field region of the spectrum compared to 2 and was thus
assigned to proton HA1. The other doublet at  ~ 6.97 ppm in
determine the different proton signals (Figure 3 and SI for 1
H
and COSY NMRs of compounds 5, 6, 8, 9 and 10). Below, we
describe only the 1H NMR spectrum of compound 10. Two
singlets are observed for HA1 and HD1. Compared to proton A1,
the chemical shift of proton D1 should not be affected during the
whole synthetic sequence from 1,7-5 to 10 and thus, based on
between the two H
1
B
protons was assigned to HA2. For compound
0, the use of 1H and/or 1H- H COSY NMRs on all synthetic
1
1
H NMR spectra, the lowest field singlet ( = 8.48 ppm) was
intermediates from compound 1,7-5 was necessary to precisely
ascribed to HA1 while the highest field one ( ~ 8.39 ppm) was
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European Journal of Organic Chemistry
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ascribed to HD1. Protons HB1,B2 and HC1,C2 were identified based
on their multiplicity (doublet) and on COSY correlations.
Aromatic ortho or bay protons were discriminated based on their
proximity to the electron-withdrawing imide groups. Namely, the
low-field shifted doublets ( ~ 8.41-8.36 ppm) was assigned to
the ortho protons (HB1 and HC1) as they experience a stronger
deshielding effect from the imide group compared to the bay
protons (HB2 and HC2), which thus appear at higher field ( ~
the azide involved in hydrogen bonding compared to the chlorine
atom, thus causing the shielding effect that makes the amide
proton in 10 resonate upfield shifted compared to PDI 9. This
observation is in good agreement with the upfield shift ( = -
0.07 ppm; from  = 4.23 to 4.16 ppm) observed for the protons in

the  position (H .
Our experience with molecules based on [c2]daisy chain
rotaxane 11,[
8,9,15]
together with the precise determination of the
1
1
1
7
.63, 7.57 ppm). Protons HB2 and HC2 (and respectively HB1 and
C1) were then identified following a similar reasoning to the one
made for HA1 and HD1, i.e. H protons are shifted to higher field
compared to H protons. Protons HE1 and HE2 were identified
H signals of compounds 2 and 10 and complemented by H- H
COSY NMR allowed us to assign all protons on compound 14
H
B
3
from their chemical shifts in CDCl (Figures S16 and S17).
However, the solubility of the unsymmetric [c2]daisy chain
C
based mainly on their integrations compared to all protons from
the perylene core. The more downfield shifted signal was
attributed to protons HE2, because the HE1 ones, closer in space
to the free primary amine group, might experience a greater
shielding effect resulting in a lower resonance frequency. Finally,
the amide proton (Ham) was clearly evidenced when comparing
rotaxane 15 proved to be quite limited in d-chloroform and thus
1H and 1H- H COSY NMR in CD
1
CN were used to precisely
3
assign the different proton signals of compound 15 (Figures S19
and S20). Methylation of compounds 14 and 15 did not greatly
1
affect their H NMR spectra, which displayed mainly a downfield
shift of the signals corresponding to the protons of the triazole
units (from  ~ 7.50 ppm to  ~ 8.20 ppm) and the appearance of
new singlets at  ~ 4.20-4.10 ppm corresponding to the methyl
groups on the triazole (Figures 4a, S20a, and S21a).
1
H NMR spectra of compounds 9 and 10. In the aromatic region,
this proton signal exhibits an upfield shift ( = - 0.16) from 8.44
ppm in PDI 9 to 8.28 ppm in PDI 10. This observation probably
results from an increased electron density on the nitrogen from
Figure 4. 1H NMR spectra (400 MHz, CD CN, 25 °C) of compounds a) 16Ext and b) 16Cont showing different chemical shifts between extended and contracted
3
states. The purple, blue and green dashed lines indicate important shifts of protons influenced by the shuttling of the macrocycles.
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European Journal of Organic Chemistry
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We then probed the pH-controlled contraction/extension for 16
chloroform, a solvent in which all components display a good
solubility (Figure 6 and S1a). We found that reference
compound 3 absorbs light below 400 nm while perylene 9
1
and 17 by H NMR. Figure 4 shows a comparison between the
1
Ext
Cont
H NMR spectra of 16
and 16
in CD
3
CN. The signals
assigned to the vinylic protons of the triazolium groups (T1 and
T1') and to the methylene protons in between the amide and
triazolium units ( and ') show downfield shifts going from the
extended state (16Ext) to the contracted state (16 ) as a result
of the shuttling motion of the macrocycles from the ammonium
stations to the triazolium stations. Furthermore, the benzylic
methylene protons (9 and 9') next to the ammonium station and
the methylene protons (3 and 3') next to the triazolium station
show up- and downfield shifts, respectively (green dashed lines).
These observations are in agreement with what was observed
for other molecules based on [c2] daisy chain rotaxane
displays a maximum of absorption at 705 nm with a small
0 1
shoulder at 645 nm, corresponding to the S -S electronic
transition, along with a higher energy S -S electronic transition
0
2
Cont
[24]
at 436 nm, in agreement with the literature. Overall, we found
that the absorption spectra of 16Cont correspond well to the sum
of its reference components in the contracted state. However,
for compound 16Ext, a bathochromic shift of the absorbance
0 1
corresponding to the S -S electronic transition (725 nm) was
observed (Figure 6a). Compared to reference perylene 9 and
compound 16Cont, such behavior can suggest the formation of J-
Ext
aggregates in the extended state. However, for compounds 17
and 17
1
1.[
8,9,15,31]
Similar observations were made for compounds 17
Ext
Cont
in benzonitrile, the actuation did not lead to significant
Cont
and 17 , regarding the vinylic protons of the triazolium groups,
the methylene protons in between the amide and triazolium units,
the benzylic methylene protons next to the ammonium station
and the methylene protons next to the triazolium station (Figure
S22).
differences by UV-Vis spectroscopy (Figure S1b).
We also used 1H DOSY NMR spectroscopy to confirm the
contraction/extension event on compound 16 (Figure 5).
Figure 6. Molar absorbance coefficient (plain line) and fluorescence spectra
(
(
dashed line) upon excitation at 440 nm of rotaxanes 16Ext (red) and 16Cont
black) recorded in chloroform at a concentration of 0.1 mM.
Figure 5. Partial DOSY NMR spectra of compounds 16Ext and 16Cont (400
MHz, CD
extended and contracted states.
3
CN, 25 °C) showing differences in the diffusion coefficient between
Steady-state fluorescence experiments on compounds 9, 16Ext
and 16Cont were also recorded in chloroform after excitation at
4
40 nm (Figure 6 and S1c). The fluorescence spectrum of
Ext
extended compound 16 shows a maximum of emission at 773
nm, which is red-shifted by 39 nm compared to the fluorescence
spectrum of reference perylene compound 9. Interestingly, for
DOSY NMR experiments provide information on the diffusion
behavior of the molecules and thus on their hydrodynamic radii
(
H
R ) using the Stokes-Einstein equation which considers a hard
Cont
contracted compound 16 , the maximum of emission was
sphere model. For the extended state, lower diffusion
a
located at around 753 nm, which is blue-shifted by 20 nm
compared to its extended counterpart 16Ext. Furthermore, we
can note that the intensity of emission is enhanced for the
contracted rotaxane compared to the extended one. These
observations are in agreement with the steady-state absorption
studies and suggest that, in the extended state, aggregation of
the perylene units occurs while in the contracted one, the
presence of the crown ether macrocycle in the vicinity of the
perylene unit prohibits this phenomenon.
coefficient is expected compared to the contracted state. DOSY
NMR spectra confirmed the presence of a single diffusing
species in both the contracted and extended forms. Diffusion
coefficients (D) of 247 µm2s-1 and 343 µm s , which correspond
2
-1
H
to hydrodynamic radii R of 2.47 and 1.78 nm, were measured
for 16 and 16Cont, respectively. This result is consistent with
the expected extended and contracted states and confirms the
occurrence of the contraction/extension event upon pH
modulation. This stands also for compound 17 (see Figure S3).
We then studied the optical properties of the unsymmetric
rotaxanes by means of UV-Vis-NIR absorption and fluorescence
experiments. UV-Vis-NIR absorption spectra of compounds 16Ext
and 16Cont, together with references 3 and 9, were recorded in
Ext
Finally, the electrochemical behavior of compounds 16 and 17
including the determination of reduction and oxidation potentials
to define their energy levels and electronic properties was
4 6 2 2
probed by cyclic voltammetry in 0.1 M NBu PF /CH Cl at a gold
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European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
disk electrode under planar diffusion conditions (Figures 7 and
S2). Cyclic voltammograms of 16Ext (Figure 7a, black trace)
show a chemical reversible reduction process with a mid-point
values when going from 17Ext (+0.13 V, +0.27 V and +0.36 V) to
17Cont (0.18 V, 0.31 V and 0.41 V). Comparison with the model
compound S3 (isolated triarylamine unit, E1/2,a = +0.3 V, Figure
S2) suggests that the second oxidation process is most likely
located at the triarylamine based stopper.
+
potential E1/2,c centered at -1.30 V vs. Fc/Fc (Table 1) and two
chemically reversible oxidation processes with mid-point
+
potentials (E1/2,a) of +0.19 V and +0.31 V vs. Fc/Fc . The higher
peak amplitude of the first oxidation process indicates an
overlap of the oxidation of the TAA unit and the first oxidation of
the perylene unit. This becomes obvious by comparing the redox
potential of the isolated perylene (S2) and triarylamine (S4)
reference compounds (Figure S2) that reveal mid-point
potentials for the oxidation of +0.17 and +0.30 V (both S2) and
+0.17 V (S4). Due to the blocking of the para-positions in the
triarylamine stopper no follow-up reactions such as dimerization
occur.[
36,37]
Moreover, the pronounced current amplitude of the
reduction of the perylene unit in the reference compound S2 that
is about twice the current amplitude of the first oxidation process
in S2 (Figure S2a) strongly suggests a two-electron transfer
mechanism for the cathodic process. Evidently, the cyclic
voltammetric response of the extended form 16Ext reflects the
voltammetric signatures of the individual reference compounds
S2 and S4 and significant effects of the macrocycle on the
electrochemical response of the electroactive stoppers are
absent. Consequently, the donor and acceptor site can be
regarded as isolated redox sites within the daisy chain rotaxane
in 16ext. On the other hand, the contracted form 16Cont (Figure 7a,
red trace) shows a rather broad reduction wave of low chemical
reversibility and only a rather broad chemically reversible
oxidation wave. The crown ether-based macrocycle seems to
significantly alter the electrochemical response of the redox
active stoppers in the contracted conformation. In case of the
reduction the closer proximity of the crown ether moiety seems
to have a destabilizing effect on the reduced perylene stopper
form. This is seen from the weak re-oxidation peak in the
backward scan of the reduction suggesting lower chemical
stability. Comparing the oxidation waves of the extended and
contracted forms one sees that the potential of the second
oxidation of the perylene unit is shifted to lower potentials which
results in a stronger superposition with the first oxidation of the
perylene and the TAA stopper. A lower potential for this second
oxidation does also indicate easier oxidation in the contracted
form compared to the extended one.
Figure 7. Cyclic voltammograms of compounds 16 (a) and 17 (b) in 0.1 M
Ext
NBu
4 6 2 2
PF /CH Cl at a gold disk electrode (planar diffusion conditions). a) 16
Cont
(c = 0.77 mM); b) 17Ext (c = 0.25 mM), 17Cont (c = 0.28
(
c = 0.74 mM), 16
The electrochemical response of 17Ext (Figure 7b, black
trace) and 17Cont (red trace) shows a similar behavior. However,
the effect of the crown ether moiety seems to be less
pronounced. Cyclic voltammograms of 17Ext show a single
chemically reversible reduction process located at -1.33 V vs.
Fc/Fc (Table 1) in analogy to 16Ext. However, in the contracted
form, a peak splitting was observed that might be attributed to
an interaction of the macrocycle with the singly reduced
perylene unit. In contrast to 16Ext, here, the macrocycle seems to
have a stabilizing effect on the radical anion and shifts the
potential of the second reduction to more negative values (-1.45
mM); all voltammograms were recorded with a scan rate of 100 mV.s-1 and
were not background corrected; arrows indicate initial scan direction.
Although not fully deciphered, the difference in the
electrochemical behavior between the extended and contracted
forms can be attributed to the shuttling of the crown ether in the
vicinity of the redox unit and thus: i) change the solvation shell
around it; ii) induce van der Waals or H-bonds interactions; and
+
iii) have
a
general shielding effect on the structural
rearrangement upon electron transfer. All these effects will lead
to a change in the reorganization energy upon reduction /
oxidation and can also change the kinetics of the electron
transfer interactions which can induce peak splitting, as for
instance observed for the reduction of 17Cont. The differences in
+
V vs. Fc/Fc ). A similar effect on the potential was observed for
the oxidation processes. The mid-point potentials of the
oxidation processes (stepwise oxidation of the perylene unit and
1
e- oxidation of the triarylamine unit) are shifted to more positive
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European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
the electrochemical response between the extended and
contacted forms should in principle allow for an electrochemical
identification of the individual species under acidic or basic
conditions and shows the potential applicability of this system in
e.g. pH sensitive sensor devices based on an electrochemical
readout. It should be here mentioned that such an altered
electrochemical response of redox active rotaxane upon
that family of compounds. In addition, cyclic voltammetry
experiments show that the electrochemical properties of such
[c2] daisy chain rotaxanes can be altered by the shuttling event
occurring upon pH modulation. It can be anticipated that the
electrochemical discrimination - although not pronounced but
clearly visible - of the two conformations allow for the use of
such supramolecular structures in pH sensitive electrochemical
sensor devices. Moreover, the unsymmetrical nature of the
redox active daisy chain rotaxanes based on the integration of
an electron donor (triarylamine) and an electron acceptor
(perylene) unit allows for the selective electrochemical triggering
of only a single stopper unit and may thus be of particular
importance for the fabrication of complex electrochemically
active molecular machines.
protonation/deprotonation was recently reported for
[
a
2]rotaxane equipped with redox active viologen units.[38]
From the estimated mid-point potentials, the HOMO
highest occupied molecular orbital) and LUMO (lowest
(
unoccupied molecular orbital) energy levels (EHOMO and ELUMO
were calculated for the electron donor-acceptor systems 16 and
)
1
7 (Table 1, for details on the calculation see Supporting
Ext
Information). The lowest HOMO value was observed for 16
(
3
5.28 eV). The highest LUMO level was found for 17 (both forms,
.77 eV). The electrochemical band gaps, determined from the
Experimental Section
differences in energy levels, ranged from 1.46 to 1.51 eV. These
values are even above the values for TAA-fullerenes dyads and
triads (ECV, gap = 1.31 – 1.34 eV) and demonstrate the strong
electron affinity of the perylene unit.[32]
General methods. All reactions were performed under an atmosphere of
argon unless otherwise indicated. All reagents and solvents were
purchased at the highest commercial quality and used without further
purification unless otherwise noted. Dry solvents were obtained using a
double column SolvTech purification system. Yields refer to purified
Table 1. Mid-point potentials of the oxidation (E1/2,a) and reduction processes
1
spectroscopically ( H NMR) homogeneous materials. Thin Layer
(E
1/2,c), energy levels (EHOMO and ELUMO) and electrochemical band gap (ECV,
Chromatographies were performed with TLC silica on aluminium foils
gap) values for compounds 16 and 17 determined in 0.1 M NBu PF /CH Cl at a
4
6
2
2
(Silica Gel/UV254, Aldrich). In most cases, irradiation using a Bioblock
planar Au disk electrode with a nominal diameter of 3 mm. All potentials were
given vs. the potential of the Fc/Fc+ redox couple.
VL-4C UV-Lamp (6 W, 254 nm and/or 365 nm) as well as p-anisaldehyde,
phosphomolybdic acid and Cerium ammonium molybdate stainings were
used for visualization. Ultra Performance Liquid Chromatographies
coupled to Mass Spectroscopy (UPLC-MS) were carried out on a Waters
Acquity UPLC-SQD apparatus equipped with a PDA detector (190-500
nm, 80Hz), using a reverse phase column (Waters, BEH C18 1.7 µm,
1/2,a (V)[a]
HOMO (eV)[b]
LUMO (eV)[b]
gap (eV)[c]
E
E
E
1/2,c (V)
E
E
+
0.19
1
6Ext
-1.30
-5.29
-3.81
1.48
(+0.31)
2
.1mm x 50 mm), and the MassLynx 4.1 – XP software. MALDI mass
+
0.13
spectra were recorded on Bruker Daltonics Autoflex II TOF
spectrometer. High resolution mass spectra were recorded on a Micro-Q-
TOF apparatus from Bruker. H NMR spectra were recorded on a Bruker
Avance 400 spectrometer at 400 MHz and 13C spectra at 100 MHz in
CDCl
residual proton solvent signal (CDCl
for 1H spectrum, and CDCl
: 77.16 ppm and CD
3
ppm for 13C spectrum). For H NMR assignments, the chemical shifts are
given in ppm. Coupling constants J are listed in Hz. The following
notation is used for the 1H NMR spectral splitting patterns: singlet (s),
doublet (d), triplet (t), multiplet (m), large (l). Diffusion Order
Spectroscopy (DOSY) NMR spectra were recorded on a Bruker Avance I
spectrometer at 500 MHz at the Service de Résonance Magnétique
Nucléaire at the Faculty of Chemistry at the University of Strasbourg. UV-
Vis-NIR spectra were recorded on either Cary 500 Scan Varian or Perkin
Elmer – Lambda 25 UV-Vis-NIR spectrophotometers in a quartz glass
cuvette with 1.0 cm optical path. Fluorescence emission spectra were
recorded on a FluoroMax-4 (Horiba JobinYvon) spectrofluorometer with
the following settings: slit width = 5 nm, increment = 1 nm, integration
time = 0.1 s in a quartz glass cuvette with a 1.0 cm optical path. Cyclic
Voltammetry experiments were recorded according to the protocol
reported in the Supporting Information.
a
1
7Ext
(+0.27)
-1.33
-1.31
-5.23
-5.28
-5.28
-3.77
-3.80
-3.77
1.46
1.48
1.51
(+0.36)
1
1
6Cont
+0.18
3
or CD
3
CN at 25°C. The spectra were internally referenced to the
: 7.26 ppm and CD CN: 1.94 ppm
CN: 118.26 and 1.32
3
3
+
0.18
(+0.31)
+0.41)
-1.33
7Cont
3
1
(-1.45)
1
(
[
a] Values in parentheses correspond to the mid-point potentials of the
HOMO (=-(E1/2,a+5.1)[eV]) and
1/2,c+5.1)[eV]) values were calculated from the mid-point potentials of the first
second and third oxidation. [b]
E
ELUMO (=-
(E
oxidation or reduction process, respectively; the error in potential values is
estimated to be ≤ ± 0.01 V. [c] Egap calculated as the difference between the
HOMO and LUMO level.
Conclusions
To summarize, we have designed and synthesized two
unsymmetrical pH-switchable [c2]daisy chain rotaxanes which
combine electroactive triarylamine and perylene units as
stoppers. Using 1D and 2D NMR spectroscopies, we have
demonstrated the efficiency of the shuttling process upon
stepwise addition of base and acid. This advanced synthetic
example shows that complex [c2]daisy chains bearing distinct
substituents can enrich the number of chemical structures within
Compound 2: To a stirred, sticky suspension of 1 (188 mg, 398 mol) in
MeOH (5 mL) was added slowly a 1 M HCl solution (6 mL) followed by
two drops of conc. HCl. The mixture was then cooled down to 0°C. After
1
5 min at this temperature, NaNO
mL) was added dropwise within about
suspension immediately turned brown after the first drop. The mixture
2
(129 mg, 1.87 mmol) in water (0.8
2
min. The yellow-orange
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European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
was further stirred for 35 min. Then, NaN
3
(259 mg, 3.98 mmol) in water
128.4, 128.3, 123.3, 122.9, 117.9, 117.6, 117.0, 116.9, 52.2, 40.7, 40.5,
(
2.6 mL) was added in two portions. The brown suspension was further
32.0, 30.3, 29.7 (3C), 29.6, 29.5, 29.4, 28.4, 28.3, 27.4, 27.3, 27.0, 25.7,
+
stirred for 40 min, while allowing the mixture to warm up to room
temperature. Dichloromethane (90 mL) was added and the mixture was
washed with water (90 mL). The organic phase was washed with sat.
NaHCO
concentrated under reduced pressure. The oily brown crude product was
purified by flash column chromatography (SiO dichloro-
methane/cyclohexane: 1/1) to afford compound 2 (131 mg, 66 % over
72 4 4 2
22.8, 14.2; ESI-MS: m/z calcd for C56H N O : 882.56 [M+H O] , found
882.58;
Compound 1,7-5: R
f
(dichloromethane/cyclohexane: 4:1) = 0.22 (1,7-5);
(25 mL) followed by brine (25 mL), dried over Na
2
SO
4
and
1H NMR (CDCl
3
, 400 MHz, 25°C):  = 8.39 (s, 2H), 8.33 (d, J = 8.0 Hz,
3
3
2H), 7.56 (d, 3J = 8.0 Hz, 2H), 4.22 (t, J = 7.6 Hz, 4H), 3.82–3.50 (brm,
3
2
,
4H), 2.90–2.65 (brm, 4H), 2.15–1.85 (brm, 8H), 1.83–1.58 (brm, 4H),
1.52–1.10 (brm, 36H), 0.87 (t, J = 6.9 Hz, 6H); 13C NMR (CDCl
3
3
, 100
two steps) as a brown waxy solid. R
f
(dichloromethane/cyclohexane: 1/1)
MHz, 25°C):  = 164.2, 146.6, 134.3, 130.0, 126.7, 123.9, 122.2, 121.9,
120.8, 119.2, 118.2, 52.3, 40.7, 32.1, 29.8 (3C), 29.6, 29.5, 28.4, 27.4,
: 864.5523 [M+H]+,
72 4 4
25.9, 22.8, 14.3; HRMS: m/z calcd for C56H N O
=
0.27, 1H NMR (CDCl
3
, 400 MHz, 25°C):  = 7.50–7.33 (m, 10H), 7.04
3
3
3
(
d, J = 9.2 Hz, 4H), 6.98 (d, J = 8.8 Hz, 2H), 6.92 (d, J = 8.8 Hz, 4H),
3
6

1
.86 (d, J = 8.8 Hz, 2H), 5.06 (s, 4H); 13C NMR (CDCl
3
, 100 MHz, 25°C):
found 864.5554.
= 155.1, 146.1, 141.3, 137.2, 132.3, 128.7, 128.1, 127.6, 126.1, 122.9,
19.8, 115.8, 70.5; HRMS: m/z calcd for C32
: 499.2129 [M+H]+,
26 4 2
H N O
Compound 6: A solution of diimide 1,7-5 (420 mg, 485 mol) in tert-
butanol (75 mL) was heated up to reflux under an argon atmosphere.
KOH (1.91 g, 34.0 mmol) suspended in hot tert-butanol (38 mL) was then
added, whereas the dark-green reaction mixture turned blueish green.
After heating for 10 minutes, the hot mixture was carefully poured into
acetic acid (50 mL) and the mixture turned back dark-green. The reaction
mixture was cooled to room temperature and dichloromethane (33 mL)
found 499.2111.
Compound 1,6-4 and 1,7-4: Perylene-3,4:9,10-tetracarboxylic acid
bisanhydride (PDA, 13.4 g, 34.2 mmol) was dissolved in conc. H SO
200 mL) and the solution was heated at 55°C for 19 hours. I (330 mg,
.30 mmol) was then added to the reaction mixture which was stirred for
hours. Br (3.88 mL, 75.3 mmol) was added over 45 min and the
2
4
(
2
1
6
2
was added. The mixture was washed with H
aqueous phases were extracted with dichloromethane (100 mL). The
combined organic phases were dried over Na SO . The solvent was
removed under reduced pressure and the resulting crude product was
purified by flash column chromatography (SiO , chloroform/acetone/n-
2
O (3  80 mL) and the
mixture was heated at 85°C for 16 hours. After cooling down to room
temperature, the reaction mixture was carefully poured into H O (1 L).
The precipitate was filtered and washed with copious amounts of H O,
followed by MeOH to afford a crude mixture of 1,6-, 1,7-dibromo and
,6,7-tribromo isomers as a dark red solid (18.4 g). This crude mixture
was used without further purification. 1H NMR analysis in 96–98 %
SO in D O revealed a ratio of about 24:70:6 of 1,6-, 1,7- and 1,6,7-
2
2
4
2
2
1
hexane: 10/1/9) to give monoimide 6 (214 mg, 63 %) as a dark-green
solid. R
f
(chloroform/acetone/n-hexane: 10/1/9) = 0.49; 1H NMR (CDCl
3
,
3
D
2
4
2
400 MHz, 25°C):  = 8.51 (s, 1H), 8.45 (s, 1H), 8.44 (d, J = 8.2 Hz, 1H),
8.41 (d, J = 8.0 Hz, 1H), 7.74 (d, J = 8.0 Hz, 1H), 7.59 (d, J = 8.0 Hz,
1H), 4.22 (t, J = 7.2 Hz, 2H), 3.90–3.60 (brm, 4H), 3.00–2.70 (brm, 4H),
2.20–1.90 (brm, 8H), 1.82–1.68 (m, 2H), 1.50–1.14 (brm, 18H), 0.87 (t, J
= 6.8 Hz, 3H); 13C NMR (CDCl
, 100 MHz, 25°C):  = 164.2, 164.1, 161.5,
3
3
3
isomers, respectively.
3
Acetic acid (20.0 mL, 349 mmol) was added over a suspension of the
mixture of 1,6-, 1,7-dibromo and 1,6,7-tribromo isomers (4.00 g, 7.27
mmol) in N-methylpyrrolidinone (100 mL) under an argon atmosphere.
The mixture was stirred at 60°C for 20 minutes. N-Dodecylamine (3.37 g,
3
3
161.0, 147.2, 146.5, 136.1, 133.9, 130.6, 130.4, 128.9, 126.7, 124.9,
124.5, 123.9, 122.7, 122.6, 122.3, 121.1, 120.1, 119.8, 117.5, 117.2,
114.6, 52.7, 52.5, 40.8, 32.1, 31.1, 29.9, 29.8, 29.7, 29.6, 29.5, 28.4,
18.2 mmol) was then added and the mixture was stirred at 120°C for 12
hours. The resulting dark-red suspension was then poured into water (1
L) to give a precipitate, which was filtered off and washed with MeOH (1
L). The crude product was purified by flash column chromatography
27.3, 26.0 (2C), 22.8, 14.3; HRMS: m/z calcd for C44
[M] , found 697.3524.
47 3 5
H N O : 697.3516
+
(
SiO
mixture of N,N'-didodecyl-1,6- and 1,7-dibromoperylene-3,4,9,10-
tetracarboxylic acid diimides 1,6:1,7-4 (3.10 g, 48 % over two steps). R
2
, cyclohexane/ethyl acetate: 9/1) to provide a 1:4 regioisomeric
Compound 7: A solution of compound 6 (30 mg, 0.22 mmol) in DMF (1
mL) was added over a solution of 4-aminophenylazide (31 mg, 0.05
mmol) and imidazole (171 mg, 4.15 mmol) in toluene (5 mL), and the
resulting mixture was refluxed for 12 h. After cooling to room temperature,
chloroform (30 mL) was added. The solution was washed successively
f
(
(
cyclohexane/ethyl acetate: 9/1) = 0.23 (1,6-4), 0.18 (1,7-4); 1H NMR
CDCl
, 400 MHz, 25°C) of major 1,7 isomer:  = 9.45 (d, 3J = 8.2 Hz,
3
H), 8.89 (s, 2H), 8.67 (d, J = 8.2 Hz, 2H), 4.20 (t, 3J = 7.6 Hz, 4H),
3
2
1
.79–1.70 (brm, 4H), 1.46–1.25 (brm, 36H), 0.87 (t, 3J = 6.8 Hz,6H); 13
C
with HCl (1%) (20 mL), K
organic phase was concentrated under reduced pressure. The crude
product was purified by column chromatography (SiO
2 3
CO sat. (20 mL), water (20 mL) and the
NMR (CDCl
3
, 100 MHz, 25 °C) of major 1,7 isomer:  = 163.0, 162.5,
1
4
38.1, 133.1, 132.9, 130.1, 129.4, 128.6, 127.1, 123.3, 122.9, 120.9,
1.0, 32.1 (2C), 29.8, 29.8, 29.8, 29.7, 29.5, 28.2, 27.3, 22.8, 14.3;
2
,
cyclohexane/EtOAc: 1/1) to afford pure compound 7 (31 mg, 85%) as a
MALDI-TOF: m/z calcd for
85.685.
48
C H56Br
2 2 4
N O :
885.267 [M+H]+, found
(cyclohexane/EtOAc: 1/1) = 0.20; 1H NMR (CDCl
green solid. R
f
3
, 400
8
3
MHz, 25°C): δ = 8.50 (s, 1H), 8.46 (s, 1H), 8.44 (d, J = 8.1 Hz, 1H), 8.41
(
d, 3J = 8.1 Hz, 1H), 7.69 (d, 3J = 8.0 Hz, 1H), 7.68 (d, 3J = 8.0 Hz,
Compound 1,6-5 and 1,7-5: A solution of a 1:4 regioisomeric mixture of
,6:1,7-4 (1.30 g, 1.47 mmol) in pyrrolidine (85 mL) was heated at 55°C
1H),7.13 (d, 3J = 8.5 Hz, 2H), 6.84 (d, 3J = 8.5 Hz, 2H), 4.22 (t, 3J = 7.5
1
Hz, 2H), 3.82-3.65 (brm, 4H), 2.91-2.75 (brm, 4H), 2.16-1.90 (brm, 8H),
1.81-1.70 (brm, 2H), 1.40-1.19 (brm, 18H), 0.87 (t, 3J = 6.8 Hz, 3H); 13
C
NMR (CDCl , 100 MHz, 25°C): δ = 164.8, 164.7, 164.2, 164.2, 146.8,
3
for 26 hours under an argon atmosphere. The solvent was then
evaporated under reduced pressure and the crude product was purified
by flash column chromatography (SiO
/1  4/1) to give compound 1,6-5 (170 mg, 13 %) as a dark-blue solid
and compound 1,7-5 (481 mg, 38 %) as a dark-green solid.
2
, dichloromethane/cyclohexane:
146.6, 146.6, 134.5, 134.3, 130.2, 130.1, 129.5, 127.0, 126.8, 126.3,
124.1, 123.8, 122.6, 122.2, 122.1, 121.8, 121.2, 120.8, 119.4, 119.2,
118.4, 118.1, 115.8, 52.3, 40.7, 32.1, 29.8, 29.8, 29.7, 29.6, 29.5, 28.4,
27.3, 27.2, 25.9, 22.8, 14.3.
2
Compound 1,6-5: R
f
(dichloromethane/cyclohexane: 4:1) = 0.28 (1,6-5);
1
3
H NMR (CDCl
3
, 400 MHz, 25°C):  = 8.59 (d, J = 8.0 Hz, 2H), 8.24 (s,
3
3
3
2H), 7.78 (d, J = 8.0 Hz, 2H), 4.21 (t, J = 7.6 Hz, 2H), 4.14 (t, J = 7.5
Compound 8: A solution of p-phenylene diamine (293 mg, 2.71 mmol) in
Hz, 2H), 3.80–3.46 (brm, 4H), 2.80–2.50 (brm, 4H), 2.20–1.82 (brm, 8H),
.82–1.54 (brm, 4H), 1.50–1.10 (brm, 36H), 0.88–0.82 (m, 6H); 13C NMR
CDCl , 100 MHz, 25°C):  = 164.3, 164.1, 149.9, 135.7, 131.1, 130.2,
dry N,N'-dimethylformamide (6 mL) was added over
monoimide 6 (189 mg, 271 mol) and imidazole (313 mg, 4.60 mmol) in
toluene (35 mL) under an argon atmosphere. The mixture was heated up
a solution of
1
(
3
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European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
to 150°C for 14 hours. After cooling down to room temperature,
chloroform (65 mL) was added. The solution was washed successively
Compound 14: To a solution of pseudorotaxane 11 (78.9 mg, 53.8 mol),
azide
Cu(MeCN)
3
(29.9 mg, 53.8 mol), azide 10 (46.9 mg, 53.8 mol),
PF (40.1 mg, 108 mol) in dry dichloromethane (1.6 mL),
with 1 % HCl (40 mL) and sat. Na
dried over Na SO and concentrated under reduced pressure. The crude
product was purified by flash column chromatography (SiO
dichloromethane  dichloromethane/MeOH: 99.5/0.5  99/1) to give
2
CO
3
(40 mL). The organic phase was
4
6
2
4
2,6-lutidine (1.24 L, 10.8 mol) was added under an argon atmosphere.
The dark-green solution was stirred at room temperature for 3 days. The
reaction mixture was then evaporated and the crude product was purified
2
,
unsymmetrical diimide 7 (208 mg, quantitative) as a dark-green solid. R
f
by flash column chromatography (SiO
/toluene: 100/0/2  100/5/2) to give compound 14 (38.8 mg, 25 %) as a
dark-green solid. R (dichloromethane/methanol/toluene: 100/6/2) = 0.27;
1H NMR (CDCl
, 400 MHz, 25°C): = 8.90 (brs, 1H), 8.42 (brs, 1H),
2
, dichloromethane/methanol
(
2
=
3
dichloromethane/methanol: 99/1) = 0.19; 1H NMR (CDCl
3
, 400 MHz,
3
3
5°C):  = 8.47 (s, 1H), 8.41 (s, 1H), 6.39 (d, J = 8.5 Hz, 1H), 6.37 (d, J
8.2 Hz, 1H), 7.62 (d, J = 8.3 Hz, 1H), 7.60 (d, J = 8.8 Hz, 1H), 7.15 (d,
J = 8.4 Hz, 2H), 6.87 (d, J = 8.4 Hz, 2H), 4.22 (t, J = 7.2 Hz, 2H), 3.90–
f
3
3
3
3
3
8.40–8.16 (m, 4H), 7.82–7.62 (m, 2H), 7.61–7.49 (m, 3H), 7.49–7.42 (m,
1H), 7.42–7.27 (m, 14H), 6.93 (d, 3J = 8.8 Hz, 4H), 6.89–6.59 (m, 18H,),
6.59–6.49 (m, 2H), 5.25 (brs, 2H), 5.18 (brs, 2H), 4.96 (brs, 4H), 4.68–
4.25 (m, 6H), 4.25–3.47 (m, 52H), 3.47–3.24 (m, 4H), 2.89–2.43 (m, 8H),
2.14–1.81 (m, 8H), 1.81–1.52 (m, 12H), 1.51–1.01 (brm, 24H), 0.97–0.67
3
2
.50 (brm, 4H), 2.95–2.60 (brm, 4H), 2.20–1.85 (brm, 8H), 1.80–1.69 (m,
H), 1.52–1.19 (m, 18H), 0.87 (t, J = 6.8 Hz, 3H); 13C NMR (CDCl
3
3
, 100
MHz, 25°C):  = 164.8, 164.7, 164.3, 164.2, 146.7, 146.6, 146.4, 134.6,
1
1
5
1
7
34.3, 130.2, 130.1, 129.5, 127.1, 126.8, 126.6, 124.1, 123.9, 122.7,
22.2, 122.1, 121.9, 121.2, 120.9, 119.4, 119.3, 118.5, 118.1, 116.1,
2.3 (2C), 32.1, 29.8, 29.8 (2C), 29.7, 29.6, 29.5, 28.4, 27.4, 26.0, 22.8,
(brm, 3H); 13C NMR (CDCl
, 100 MHz, 25°C):  = 167.8, 164.5, 164.4,
3
164.2, 164.0, 163.7, 154.9, 148.2, 147.7, 147.6, 146.7, 146.5, 146.4 (2C),
146.2, 145.6, 141.4, 137.9, 137.2, 134.7, 133.9, 132.5 (2C), 132.0, 131.0,
130.9, 129.4, 129.0, 128.7, 128.1, 127.6, 126.5, 126.0, 124.1, 123.8,
4.3; HRMS: m/z calcd for
50 53 5 4
C H N O :
788.4181 [M+H]+, found
88.4170.
1
1
23.0 (2C), 122.5, 122.0, 121.4, 121.2, 121.1, 120.8, 119.4, 118.6, 117.6,
15.7, 113.0, 113.0, 112.7, 111.9, 72.3, 72.0, 70.8, 70.4, 67.6, 67.1, 66.9
Compound 9:
A
solution of diimide
7
(208 mg, 264 mol) and
(
2
2C), 53.1 (2C), 52.3 (2C), 52.2, 48.9, 40.8, 38.9, 37.2, 32.0, 29.8, 29.6,
9.5, 29.1, 28.9, 28.4, 26.6, 26.4, 25.9, 25.4, 23.1, 22.8, 14.2; ESI-MS:
m/z calcd for C152 : 1299.664 [M–2PF
]2+, found 1299.645.
triethylamine (36.8 L, 264 mol) in dry dichloromethane (7 mL) was
added slowly over a solution of 2-chloroacetyl chloride (21.0 L, 264
H F N O P
179 12 15 24 2
6

mol) in dry dichloromethane (1.6 mL) at 0°C under an argon
atmosphere. The reaction mixture was stirred for 2 hours at room
temperature and then further dissolved in Et O (40 mL). The organic
phase was extracted with sat. NH Cl (20 mL), brine (20 mL) and dried
over Na SO . After concentration under reduced pressure, the crude
product was purified by a short column (SiO , ethyl acetate/n-hexane:
/1) to afford compound 8 (203 mg, 89 %) as a dark-green solid, which
was pure enough to be used as such in the next step. R (dichloro-
2
Compound 15: To a solution of pseudorotaxane 11 (50.3 mg, 34.4 mol),
azide (17.2 mg, 34.4 mol), azide 10 (30.0 mg, 34.4 mol),
Cu(MeCN) PF (25.6 mg, 34.4 mol) in dry dichloromethane (1.2 mL),
one drop of 2,6-lutidine was added under an argon atmosphere. The
dark-green solution was stirred at room temperature for 3 days. The
reaction mixture was then evaporated and the crude was purified by flash
column chromatography (SiO
100/0/2  100/6/2) to give compound 15 (10.1 mg, 10 %) as a dark-
green solid. R
(dichloromethane/methanol/toluene: 100/6/2) = 0.14; 1
4
2
2
4
4
6
2
1
f
methane/methanol: 99/1) = 0.18; 1H NMR (CDCl
, 400 MHz, 25°C):  =
dichloromethane/methanol/toluene:
3
2
,
3
8
7
2
1
.51 (s, 1H), 8.44 (s, 1H), 8.37–8.31 (m, 3H), 7.76 (d, J = 8.7 Hz, 2H,),
.55 (d, 3J = 8.0 Hz, 1H), 7.49 (d, J = 8.0 Hz, 1H), 7.41 (d, J = 8.7 Hz,
3
3
H
f
3
H), 4.23–4.18 (m, 4H), 3.80–3.56 (brm, 4H), 2.89–2.60 (brm, 4H), 2.14–
.86 (brm, 8H), 1.81–1.69 (m, 2H), 1.50–1.15 (brm, 18H), 0.87 (t, J = 6.8
Hz, 3H); 13C NMR (CDCl
NMR (CD
3
CN, 400 MHz, 25°C): = 9.09 (s, 1H), 8.18 (s, 1H), 8.10 (d, J
3
3
= 8.0 Hz, 1H), 8.03 (s, 1H), 8.02 (d, J = 8.4 Hz,1H), 7.82 (s, 2H), 7.78 (d,
3
3
, 100 MHz, 25°C):  = 171.1, 164.6, 164.5,
64.3, 164.3, 146.8, 146.6, 137.1, 134.9, 134.2, 132.5, 130.2, 130.1,
J = 8.8 Hz, 2H), 7.64 (s, 2H), 7.50 – 7.28 (m, 14H), 7.28–7.20 (m, 2H),
6.99 (d, 3J = 9.2 Hz, 4H), 6.91 (d, J = 9.2 Hz, 4H), 6.81 (d, J = 8.8 Hz,
2H), 6.84–6.58 (m, 12H), 6.44–6.36 (m, 2H), 5.26 (s, 2H), 5.02 (brs, 4H),
4.60–4.32 (m, 4H), 4.31–3.55 (m, 50H), 3.55–3.28 (m, 8H), 2.68 (t, 3J =
7.4 Hz, 2H), 2.63 (t, 3J = 7.3 Hz, 2H), 2.60–2.40 (m, 4H), 2.32–1.48 (m,
3
3
1
1
1
2
29.7, 127.3, 126.8, 124.2, 123.9, 122.7, 122.2, 122.0, 121.7, 121.3,
21.0, 119.3, 118.9, 118.7, 117.9, 52.4, 52.4, 43.1, 40.7, 32.1, 29.8, 29.8,
9.7, 29.6, 29.5, 28.4, 27.3, 25.9, 22.8, 14.2; HRMS: m/z calcd for
+
20H), 1.48–0.99 (brm, 24H), 0.99–0.71 (brm, 3H); 13C NMR (CDCl
MHz, 25°C):  = 165.7, 165.1, 165.0, 164.5, 156.8, 150.0, 149.2, 148.7
3C), 147.3, 147.2, 147.1 (2C), 146.9, 141.2, 139.1, 138.3, 134.9, 134.2,
52 5 5
C H54ClN O : 863.3813 [M] , found 863.3795.
3
, 100
(
1
1
Compound 10: A solution of compound 9 (203 mg, 235 mol) and NaN
214 mg, 3.29 mmol) in dry N,N'-dimethylformamide (8 mL) was heated
at 80°C for 25 hours. After cooling down to room temperature, chloroform
65 mL) was added and the mixture was extracted with H O (3  45 mL).
The combined aqueous phases were extracted with chloroform (3  45
mL). The combined organic phases were dried over Na SO and
concentrated under reduced pressure. The resulting crude product was
purified by flash column chromatography (SiO cyclohexane/ethyl
3
33.6, 130.8, 130.7, 130.6, 130.3, 129.5, 129.0, 128.6, 128.2, 127.4,
27.1, 126.4, 126.3, 124.8, 124.4, 124.1, 123.6 (2C), 123.0, 122.5, 122.3
(
(2C), 122.1, 121.7, 121.3, 121.0, 120.4, 119.7 (2C), 116.9, 114.3, 113.1,
(
2
1
6
4
2
13.0, 112.8 (2C), 73.1, 73.0, 71.6 (2C), 71.5, 71.4, 71.3, 71.1, 71.0,
8.6, 68.4, 68.3, 68.1 (2C), 68.0, 53.5, 53.0, 52.9, 52.7, 52.6, 49.8, 49.7,
1.1, 34.3, 32.7, 30.4, 30.3, 30.2, 30.1, 30.0, 29.8, 29.7, 28.9, 28.8, 27.9,
7.2, 26.9, 26.4, 26.0, 25.9, 23.4, 14.4; HRMS: m/z calcd for
2
4
2
,
150 176 12 14 23 2 6
H F N O P : 1271.1528 [M–2PF
]2+, found 1271.1500.
C
acetate: 1/1) to give azide 10 (143 mg, 70 %) as a dark-green solid. R
f
(
cyclohexane/ethyl acetate: 1/1) = 0.37; 1H NMR (CDCl
3
, 400 MHz,
3
3
Compound 16Ext: First step: To a solution of rotaxane 14 (29.7 mg, 10.3
mol) in dry dichloromethane (1.56 mL), methyl iodide (0.51 mL) was
added at once under an argon atmosphere. The dark-green solution was
stirred at room temperature for 4 days and the solvent was then
evaporated to give the diiodide precursor of 16 as a dark-green solid
(33 mg). H NMR (CD
2
=
1
5°C): δ = 8.45 (s, 1H), 8.40 (s, 1H), 8.33 (d, J = 8.1 Hz, 1H), 8.29 (d, J
3
3
8.4 Hz, 1H), 8.28 (s, 1H), 7.71 (d, J = 8.7 Hz, 2H), 7.50 (d, J = 8.0 Hz,
3
3
3
H), 7.42 (d, J = 8.1 Hz, 1H), 7.38 (d, J = 8.7 Hz, 2H), 4.21 (t, J = 7.5
Hz, 2H), 4.11 (s, 2H) 3.72-3.55 (brm, 4H), 2.82-2.60 (brm, 4H), 2.10-1.85
3
Ext
(
brm, 8H), 1.81-1.69 (brm, 2H), 1.32-1.18 (brm, 18H), 0.87 (t, J = 6.8 Hz,
H); 13C NMR (CDCl
1
CN, 400 MHz, 25°C):  = 9.81 (s, 1H), 9.34 (s, 1H),
3
1
1
1
2
3
, 100 MHz, 25°C): δ = 165.0, 164.4, 164.4, 164.0,
3
3
64.0, 146.6, 146.3, 137.5, 134.5, 133.7, 132.0, 129.9, 129.7, 129.4,
27.0, 126.6, 124.1, 123.6, 122.5, 121.9, 121.8, 121.6, 121.0, 120.9,
20.7, 119.2, 118.8, 118.5, 117.5, 53.0, 52.3, 52.2, 43.6, 40.7, 32.0, 30.3,
8.46 (s, 1H), 8.37 (s, 1H), 8.20 (s, 1H), 8.13 (d, J = 8.0 Hz, 1H), 8.06 (s,
3
3
3
1H), 8.05 (d, J = 8.0 Hz, 1H), 7.89 (d, J = 8.4 Hz, 2H), 7.46 (d, J = 8.4
Hz, 2H), 7.44–7.24 (m, 14H), 6.98–6.83 (m, 8H), 6.83–6.60 (m, 14H),
6.48–6.38 (m, 2H), 5.71 (s, 2H), 5.55 (s, 2H), 5.00 (s, 4H), 4.60–4.36 (m,
4H), 4.34–3.57 (m, 50H), 4.19 (s, 3H), 4.14 (s, 3H), 3.57–3.34 (brm, 8H,),
9.8, 29.8, 29.7, 29.6, 29.5, 28.3, 27.3, 27.0, 25.9, 22.8, 14.2; HRMS:
+
m/z calcd for C52
H
54
N O
8
5
: 870.4217 [M] , found 870.4193.
This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
2
2
0
1
1
1
1
1
1
6
5
2
.77 (t, 3J = 7.2 Hz, 2H), 2.70 (t, 3J = 7.4 Hz, 2H), 2.70–2.40 (brm, 4H),
.08–1.80 (brm, 8H), 1.80–1.50 (m, 12H), 1.50–1.15 (brm, 24H), 0.92–
H
H
13
F’ or G’), 2.08–1.80 (brm, 8H, HF’ or G’), 1.80–1.50 (m, 12H, Him2’
7’), 1.50–1.15 (brm, 24H, H im2’), 0.92–0.80 (m, 3H, HMe’’);
C NMR (CD CN, 100 MHz, 25°C): = 165.1, 165.0, 164.5, 162.7, 157.6,
4 4’ 7
H H H
5 5’ 6 6’
H H H H
.80 (m, 3H); 13C NMR (CD
3
CN, 400 MHz, 25°C):  = 165.1, 165.0, 164.5,
3
64.5, 162.8, 162.0, 156.0, 148.0 (2C), 147.3, 147.2, 147.1 (3C), 146.9,
46.7, 145.7, 145.6, 142.1, 138.7, 138.4, 135.0, 134.2, 134.0, 132.2,
32.0, 130.9, 130.9, 130.5 (2C), 130.4, 129.7, 129.5, 128.9, 128.6, 128.4,
27.1, 126.3 (2C), 124.8, 124.4, 123.7, 123.6, 123.1, 122.5, 122.3 (2C),
22.0, 121.7, 121.3 (2C), 121.0, 119.8, 119.7, 119.0, 118.0, 116.7, 114.3,
13.2, 113.1, 112.9, 73.1 (2C), 71.6 (2C), 71.5 (3C), 71.3, 71.2, 70.9,
8.6, 68.4, 68.3, 68.2 (2C), 68.1, 68.0, 67.0, 66.6, 56.6, 56.4, 52.9, 52.7,
2.6, 49.7, 41.1, 38.8, 38.7, 32.7, 30.4 (2C), 30.3 (2C), 30.2, 30.1, 30.0,
8.8 (2C), 27.9, 27.5, 27.4, 27.3, 27.2, 26.9 (2C), 23.8, 23.7, 23.4, 14.4.
152.8, 148.8, 148.7, 147.2 (2C), 147.1, 147 (3C), 146.1, 145.8, 140.1,
138.6, 138.2, 135.0, 134.2, 134.1, 131.0, 130.8, 130.7, 130.4, 129.6,
129.2, 129.0, 128.7, 128.2, 127.4, 127.1, 126.8, 126.3, 126.2, 124.8,
124.4, 123.7, 123.6, 123.2, 121.7, 121.3, 121.2, 120.9, 119.8, 118.9,
117.1, 114.2, 113.1, 112.8, 73.0, 71.6, 71.5 (2C), 71.3, 71.1, 70.9 (2C),
68.6, 68.3, 68.1, 68.0 (2C), 56.3, 52.9, 52.7, 52.6, 49.7, 41.1, 38.7, 38.4,
34.2, 32.7, 30.4, 30.3, 30.2, 30.1, 29.8, 28.9, 28.8, 27.9, 27.8, 27.4, 27.3,
27.0, 26.9, 26.4, 25.6, 23.7, 23.4, 14.4; HRMS: m/z calcd for
152 182 24 14 23 4 6
H F N O P : 1431.1404 [M–2PF
]2+, found 1431.1465.
C
Second step: To a suspension of the previous solid in water (1.4 mL)
were added NH PF (13.4 mg, 82.4 mol) and dry dichloromethane (1.4
4
6
General protocol for the contraction of rotaxane 16Ext and 17Ext: To a
mL). The resulting biphasic solution was vigorously stirred for 1 hour. The
aqueous phase was extracted with dichloromethane (3  1.6 mL). The
solution of the extended rotaxane in dry dichloromethane (2 mL, 1 mM),
an aqueous solution of 0.1 M NaOH (2 mL) was added dropwise and the
mixture was vigorously stirred at room temperature for 1 hour. The
combined organic phases were dried over Na
reduced pressure to give rotaxane 16Ext (26.5 mg, 80 %) as a dark-green
solid. 1H NMR (CD
CN, 400 MHz, 25°C):  = 9.26 (s, 1H, Ham’), 8.83 (s,
H, Ham), 8.28 (s, 1H, HT1 or T1’), 8.24 (s, 1H, HA’ or D’), 8.19 (s, 1H, HT1 or
2 4
SO and evaporated under
2 4
organic phase was then separated, dried over Na SO and concentrated
3
under reduced pressure. The residual solid was triturated with MeOH,
filtered and washed with pentane to give the contracted rotaxane as a
dark-green solid.
1
3
T1’), 8.16 (d, J = 8.0 Hz, 1H, HB’, ortho or C’, ortho), 8.08 (s, 1H, HA’ or D’), 8.06
(
d, 3J = 8.0 Hz, 1H, HB’, ortho or C’, ortho), 7.80 (d, 3J = 8.8 Hz, 2H, HE1’ or E2’),
3
7.48 (d, J = 8.8 Hz, 2H, HE1’ or E2’), 7.46–7.26 (m, 14H, H
C
H
A1 or A2
H
B’, bay
General protocol for the extension of rotaxane 16Cont and 17Cont: To a
solution of the contracted rotaxane in chloroform (2 mL, 1 mM) was
added 2 equivalents of TFA. The solution was briefly stirred before
evaporating the solvents. The residue was taken back in a 1:1 mixture of
or C’, bay), 6.98–6.86 (m, 8H, HB1
DB24C8), 6.49–6.39 (m, 2H, Har, DB24C8), 5.53 (s, 2H, H’), 5.39 (s, 2H, H),
.03 (s, 4H, H), 4.58–4.36 (m, 4H, H 9’), 4.34–3.61 (m, 50H, HCH2O,
im1’), 4.19 (s, 3H, HMe or Me’), 4.14 (s, 3H, HMe or Me’), 3.62–3.34 (brm,
H, HF’ or G’
8’), 2.76 (t, 3J = 7.8 Hz, 2H, H3 or 3’), 2.69 (t, 3J = 7.8 Hz,
H, H3 or 3’), 2.75–2.45 (brm, 4H, HF’ or G’), 2.08–1.80 (brm, 8H, HF’ or G’),
.80–1.50 (m, 12H, Him2’ 7’), 1.50–1.15 (brm, 24H, H
im2’), 0.92–0.80 (m, 3H, HMe’’); 13C NMR (CD
CN, 400 MHz, 25°C): 
165.1 (2C), 164.5, 164.5, 162.8, 162.0, 156.1, 148 (2C), 147.3, 147.2
HB2), 6.83–6.60 (m, 14H, HA1 or A2
H
ar,
5
9
H
DB24C8
H
4 6
chloroform/aqueous NH PF sat. (2 mL) and stirred vigorously for one
8
2
1
8
H H
hour. The mixture was extracted with chloroform, the organic phase dried
with sodium sulfate, filtered, and evaporated to yield the extended
rotaxane as a dark-green solid.
H
4
H
4’
H
7
H
5 5’ 6
H H
H
6’
H
3
=
(2C), 147.1 (2C), 147.0, 146.8, 145.8, 145.7, 142.1, 138.6, 138.5, 135.1,
1
1
1
1
7
5
2
1
34.3, 134.2, 132.3, 131.8, 131.0, 130.7, 130.4, 129.5, 128.9, 128.7,
27.4, 127.2, 127.1, 126.3 (2C), 124.9, 124.4, 123.7, 123.6, 123.1, 122.6,
22.3, 122.2, 122.0, 121.7, 121.3 (2C), 121.0, 119.8 (2C), 119.0, 118.1,
16.8, 114.3, 113.1 (2C), 112.8, 73.1, 73.0, 71.6 (2C), 71.5 (3C), 71.3,
1.1, 70.9, 68.6, 68.3 (2C), 68.2 (2C), 68.1, 68.0, 56.3, 56.2, 52.9, 52.7,
2.6, 49.7 (2C), 41.1, 38.7, 38.6, 32.7, 30.4 (2C), 30.3 (2C), 30.1, 28.9,
8.8, 27.9, 27.4 (2C), 27.3, 27.2, 26.9 (2C), 26.4 (2C), 23.8, 23.7, 23.4,
Acknowledgements
This work was performed within the framework of the IRTG “Soft
Matter Science: Concepts for the Design of Functional Materials”
(
A.W., S. L. and N.G.). We wish to thank the international center
for Frontier Research in Chemistry (fellowship to A.W.) and the
Laboratory of Excellence for Complex System Chemistry. This
work was also supported by the Agence Nationale pour la
Recherche (ANR-09-BLAN-034-02), the French Ministry of
Research and the China Scholarship Council (fellowships to
J.J.C., F.N. and G. D. respectively).
185 24 15 24 4 6
4.4; ESI-MS: m/z calcd for C154H F N O P : 657.343 [M–4PF ,
]4+
found 657.317.
Compound 17Ext: To a solution of rotaxane 15 (13.5 mg, 4.77 mol) in
dry dichloromethane (0.7 mL), methyl iodide (237 L) was added at once
under an argon atmosphere. After 4 days, MeI (60 L) was added and
the mixture was stirred for 1 day, then the solvent was evaporated. To a
Keywords: rotaxane • triarylamine • perylene • pH-responsive •
suspension of the previous solid in water (0.6 mL) were added NH
4 6
PF
(
6.2 mg, 38.1 mol) and dry dichloromethane (0.6 mL). The resulting
electroactive
biphasic solution was vigorously stirred for 1 hour. The aqueous phase
was extracted with dichloromethane (3  0.7 mL). The combined organic
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2
SO
4
and evaporated under reduced pressure
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1
(
8
CD
.28 (s, 1H, HT1 or T1’), 8.25 (s, 1H, HA’ or D’), 8.17 (d, 3J = 8.0 Hz, 1H, HB’,
ortho or C’, ortho), 8.07 (s, 1H, HA’ or D’), 8.06 (d, 3J = 8.0 Hz, 1H, HB’, ortho or C’,
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3
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3
7
7
6
6
4
4
7
.49 (d, J = 8.4 Hz, 2H, HE1’ or E2’), 7.51–7.27 (m, 14H, H
C
HB’, bay or C’, bay),
.15 (d, 3J = 9.2 Hz, 4H, HB1 or B2), 7.01 (d, 3J = 9.2 Hz, 4H, HB1 or B2),
.98–6.59 (m, 12H, Har, DB24C8), 6.88 (d, 3J = 9.6 Hz, 2H, HA1 or A2), 6.49–
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H, H H9’), 4.34–3.61 (m, 50H, HCH2O, DB24C8 Him1’), 4.19 (s, 3H, HMe or Me’),
9
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H H
8’), 2.76 (t, 3J =
.16 (s, 3H, HMe or Me’), 3.62–3.32 (brm, 8H, HF’ or G’
.6 Hz, 2H, H3 or 3’), 2.71 (t, J = 7.6 Hz, 2H, H3 or 3’), 2.82–2.47 (brm, 4H,
3
[
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This article is protected by copyright. All rights reserved.

European Journal of Organic Chemistry
10.1002/ejoc.201900179
FULL PAPER
Entry for the Table of Contents
FULL PAPER
[
a]
[a]
Molecular Machines
Adrian Wolf, Juan-José Cid, Emilie
Moulin,*[a] Frédéric Niess, Guangyan
Du,[a] Antoine Goujon, Eric
[a]
pH-switchable [c2]daisy chain
rotaxanes that present two different
electroactive units as stoppers have
been synthesized and fully
characterized. Their actuation
between the contracted and
extended forms leads to a
[a]
Busseron, Adrian Ruff,[b,c] Sabine
Ludwigs[ and Nicolas Giuseppone*
[a]
b]
[a]
Page No. – Page No.
Unsymmetric bistable [c2]daisy
modification of their electrochemical
properties.
chain rotaxanes which combine two
types of electroactive stoppers
This article is protected by copyright. All rights reserved.