Dithienylethene-based rotaxanes: Synthesis, characterization and properties

Article abstract of DOI:10.1039/c4ob01213e

The photochromic materials have been widely applied in many fields. In this article, we report a class of photochromic ammoniums with a dithienylethene backbone. They were utilized as templates to construct mechanically interlocked rotaxanes and pseudorotaxanes showing photo-responsive behavior by template-directed clipping reaction and the threading approach. The structures of novel rotaxanes were well defined. It is worth mentioning that the single crystal structure of [3]rotaxane containing two N-hetero crown ether units was obtained. Their photoisomerization behavior was investigated. These N-hetero crown ether-based rotaxanes displayed good reversibility and similar photochromic behaviors to their corresponding ammoniums when they underwent UV/vis photoirradiation. Interestingly, the cucurbit[6]uril-based pseudorotaxane showed better photoisomerization than its corresponding ammonium and those of N-hetero crown ether-based rotaxanes.

Full text of DOI:10.1039/c4ob01213e

Organic &
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Dithienylethene-based rotaxanes: synthesis,
characterization and properties†
Cite this: Org. Biomol. Chem., 2014,
12, 7712
Fang Hu,a Juanyun Huang,a Meijiao Cao,a Zhao Chen,a Ying-Wei Yang,b
Sheng Hua Liu*a and Jun Yin*a
The photochromic materials have been widely applied in many fields. In this article, we report a class of
photochromic ammoniums with a dithienylethene backbone. They were utilized as templates to construct
mechanically interlocked rotaxanes and pseudorotaxanes showing photo-responsive behavior by
template-directed clipping reaction and the threading approach. The structures of novel rotaxanes were
well defined. It is worth mentioning that the single crystal structure of [3]rotaxane containing two
N-hetero crown ether units was obtained. Their photoisomerization behavior was investigated. These
N-hetero crown ether-based rotaxanes displayed good reversibility and similar photochromic behaviors
to their corresponding ammoniums when they underwent UV/vis photoirradiation. Interestingly, the
cucurbit[6]uril-based pseudorotaxane showed better photoisomerization than its corresponding
ammonium and those of N-hetero crown ether-based rotaxanes.
Received 12th June 2014,
Accepted 11th July 2014
DOI: 10.1039/c4ob01213e
www.rsc.org/obc
Accompanying the great development of dithienylethenes,
two main strategies have been employed to design such
Introduction
Photochromism refers to the reversible rearrangement of a materials with excellent photochromic behaviour. On the one
chemical species between two forms induced by alternating hand, changing the functional groups on the R (Scheme 1)
irradiation with UV and visible light that causes changes in the sites of the dithienylethene backbone has been a popular strat-
absorption spectra.1 The application of such species in optical egy, and various factors, such as steric hindrance, electronic
materials and photonic devices such as variable-transmission effects, the length of conjugation, and so on, have been con-
filters, optical information storage systems, and photoregulated sidered in the design of photochromic materials.3 On the
molecular switches has attracted considerable interest.1 Photo- other hand, the bridging unit (cyclopentene) has also been
chromic dithienylethene derivatives (Scheme 1) with heterocyclic substituted by other conjugated moieties.4 Compared with
aryl groups are among the most attractive families of photochro- covalent interactions, noncovalent interactions such as ion–
mic compounds because of their remarkable fatigue resistance, dipole interactions are being increasingly considered in the
excellent thermally irreversible properties, and high sensitivity.2
design of all kinds of functional materials, and extensive
research has shown that noncovalent interactions play crucial
roles in determining the properties of materials.5 Mechanically
interlocked molecules (such as rotaxanes),6 incorporating non-
covalently interacting components in one molecule, provide
ideal models for investigating the photochromic behaviour of
dithienylethenes with a mechanically interlocked backbone.
To date, several studies on dithienylethene-based rotaxanes
have been reported.7 For example, Irie found that the complex
of cyclodextrin and dithienylethene enhanced the photocycli-
zation quantum yield.8 Tian et al. reported a multi-state
[2]rotaxane based on the dithienylethene unit which could alter
intercomponent interactions in a photochromic multi-state[2]-
rotaxane.9 Recently, Liu and co-workers reported a [2]pseudo-
rotaxane containing a Eu3+ complex of terpyridinyldibenzo-24-
crown-8, which revealed dual-stimulus luminescent lanthanide
molecular switching behavior.10 Herein, we present three
unprecedented examples of dithienylethene-based [n]rotaxanes
Scheme 1 Ring-open and ring-closed photoisomerization of dithienyl-
ethene.
aKey Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of
Chemistry, Central China Normal University, Wuhan 430079, PR China.
E-mail: yinj@mail.ccnu.edu.cn
bState Key Laboratory of Supramolecular Structure and Materials, College of
Chemistry, Jilin University, Changchun, 130012, PR China
†Electronic supplementary information (ESI) available: The 1H NMR, 13C NMR
and MS spectra of all the new intermediates and [2]catenanes. CCDC 977069.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c4ob01213e
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by installing macrocyclic moieties at the R sites of the dithi- utilized to construct dithienylethene-based [n]rotaxanes 12
enylethene backbone. Our investigations have mainly focused and 13 by a template-directed clipping reaction based on di-
on their self-assembly process, structures and photoisomeriza- aldehyde 10 and diamine 11, as presented in Scheme 3. The
tion properties.
clipping reaction was first tested for 12 and 13 by mixing equi-
molar amounts of dialdehyde 10, diamine 11, and the corres-
ponding ammonium salts in CH3CN. The self-assembly
process was monitored by 1H NMR. The resonances of the
protons on the stopper units of [3]rotaxane 12 (H7 and H8,
Results and discussion
The stepwise synthesis of the dithienylethene-based Fig. 1B) displayed upfield shifts compared to those of the
ammonium salts 4 and 9 is outlined in Scheme 2. These were dithienylethene-based ammonium salt 4 (Fig. 1A) as a result of
Scheme 2 Synthesis of dithienylethene-based amines 3, 8 and ammoniums 4, 9.
Scheme 3 The structures of dithienylethene-based ammoniums 4 and 9, and the synthesis of [n]rotaxanes 12 and 13.
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Fig. 1 Partial 1H NMR spectra (400 MHz, CD3CN, 298 K) of 4 (A), 12 (B), 14 (C), 13 (D), 9 (E) (resonances labeled as “×” indicate impurities in the
solvents).
the shielding effect associated with the encircling crown ether
macrocyclic ring. In addition, the signals of the protons (Ha
and Hb) on the hetero-crown ether components were down-
field-shifted relative to those of these protons in 14 itself
(Fig. 1C). The observed shifts in the proton resonances, which
were in good agreement with those noted in our previous
studies,11 suggested that the newly installed crown ether ring
system in 12 encircles the ammonium moieties of the dithienyl-
ethene-based ammonium salt 4. Similarly, evidence for the
formation of [5]rotaxane 13 by this process was provided by
analysis of the relevant 1H NMR spectrum. As shown in
Fig. 1D, obvious upfield shifts for the signals of the benzene
ring protons (H13′ and H14′) between the spectra of 9 (Fig. 1E)
and 13 (Fig. 1D) indicated that the crown ether units had been
threaded onto the ammonium sites.
Additional evidence supporting this conclusion was pro-
vided by analysis of the respective MALDI-TOF mass spectra,
which featured peaks at m/z 1577.84 attributable to [M − HPF6
− PF6−]+ for [3]rotaxane 12 and at m/z 2735.13 attributable to
[M − 3HPF6 − PF6−]+ for [5]rotaxane 13 (see the ESI†). Gratify-
ingly, the structure of [3]rotaxane 12 could be further proved
by X-ray crystallographic analysis. A single crystal of 12 suitable
for X-ray diffraction analysis was grown by slow diffusion of
hexane into a solution of this rotaxane in dichloromethane.
The solid-state structure in Fig. 2A clearly revealed that two
crown ether units encircled the template sites of dithienyl-
Fig. 2 Single crystal structure (A) and packing views (B) of 12.
ethene ammonium salt 4.
The photoisomerization behaviour of 12 and 13 induced by
photoirradiation in CH3CN was studied at room temperature. transition.12 This colorless solution turned yellow and a new
Both rotaxanes underwent photoisomerization between the absorption band centered at 458 nm (ε = 0.245 × 10−4 L mol−1
ring-open isomer and the ring-closed isomer upon alternating cm−1) appeared when it was irradiated with 302 nm UV light,
irradiation with UV light (λ = 302 nm) and visible light (λ > as a result of a ring-closure reaction to give the ring-closed
402 nm), as illustrated in Scheme 1. As shown in Fig. S2A,† the isomer of [3]rotaxane 12. Upon irradiation with visible light
absorption maximum of compound 12 in CH3CN was observed (λ > 402 nm), the colored ring-closed isomer of [3]rotaxane 12
at 240 nm (ε = 6.31 × 10−4 L mol−1 cm−1) as a result of the π–π* underwent a cycloreversion reaction to the initial colorless
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ring-open isomer. The cyclization and cycloreversion quantum 2837.10 could be assigned to [M − 2HPF6 − PF6−]+, with M
yields of 12 were 0.155 and 0.019, respectively. Similar photo- being pseudo[3]rotaxane 19 (see ESI†).
chromic behaviour was observed for [5]rotaxane 13 (Fig. S2B†).
The photochromic behaviour of 19 induced by photoirra-
The photochromic parameters of N-hetero crown ether-based diation in CH3CN was measured at room temperature using
rotaxanes 12 and 13 are summarized in Table S1.† Although the same method as above. As illustrated in Fig. 3A, the
the photoisomerization processes of [3]rotaxane 12 and absorption maximum of compound 19 in CH3CN was observed
[5]rotaxane 13 showed good reversibility, no obvious enhance- at 237 nm (ε = 4.82 × 10−4 L mol−1 cm−1). This colorless solu-
ments of photochromism were observed in comparison with tion turned yellow and a new absorption band centered at
the corresponding ammonium salts (Fig. S3†). It is well known 454 nm (ε = 0.78 × 10−4 L mol−1 cm−1) appeared when it was
that the dithienylethene is not photoreactive when it lies in irradiated with 302 nm UV light, as a result of a ring-closure
the parallel conformation.8 Therefore, it is possibly derived reaction to give the ring-closed isomer of pseudo[3]rotaxane
from the similar ratio of antiparallel : parallel conformations.
19. In addition, a well-defined isosbestic point was observed at
Accordingly, we selected cucurbit[6]uril to construct a 280 nm. Upon irradiation with visible light (λ > 402 nm), the
further dithienylethene-based rotaxane due to the bigger steric ring-closed isomer underwent a cycloreversion reaction to the
configuration.13 The ammonium salt 18 was synthesized initial colorless ring-open isomer. Furthermore, compound 19
according to the established route (Scheme 4). The threading had good fatigue resistance. Surprisingly, in comparison with
of cucurbit[6]uril with the dithienylethene-based ammonium the ammonium salt 18, we found that the pseudo[3]rotaxane 19
salt was investigated by mixing the components in water had a higher degree of photoisomerization (Fig. 3B) and response
(Scheme 5). The 1H NMR spectrum of pseudo[3]rotaxane 19 rate, possibly due to the increase in the ratio of antiparallel :
(Fig. S1A†) showed obvious upfield shifts of the resonances of parallel conformations.8 Furthermore, it also showed better
the protons on the alkyl chain (H7″ and H10″) with respect to photochromism than crown ether-based dithienylethenes. These
the spectrum of 18 (Fig. S1B†).11a This indicated that the results suggested that the mechanically interlocked molecules
cucurbit[6]uril had become threaded onto the alkyl chain com- can also be considered as good candidates for photochromic
ponent between the two ammonium moieties to form a materials with excellent photochromic behaviors.
pseudo[3]rotaxane. Further proof was obtained by MALDI-TOF
Subsequently, the density functional theory (DFT) calcu-
mass spectrometry in acetonitrile. A peak observed at m/z lation had been performed to gain a deeper insight into the
Scheme 4 Synthesis of dithienylethene-based amine 17 and ammonium 18.
Scheme 5 The synthesis and models of dithienylethene-based [3]rotaxanes 19.
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Fig. 3 (A) Absorption spectral change of pseudo[3]rotaxane 19 by photoirradiation in CH3CN (2.0 × 10−5 mol L−1). The inset shows the fatigue resist-
ance of dithienylethene-based [n]rotaxanes (λUV = 302 nm; λVis > 402 nm); (B) The cyclization kinetics of 18 and 19 in CH3CN (2.0 × 10−5 mol L−1
upon irradiation with UV light (λ = 302 nm).
)
Fig. 4 The optimized structures of 12, 13 and 19 at the B3LYP/6-31G* level, using the Gaussian 09 program.
molecular structures of the open-ring and closed-ring forms. carbon atoms is less than 4.2 Å.14 The optimized structure of
Details of the optimized structures are given in Fig. 4. For the 12o was in agreement with the X-ray crystallographic analysis.
open forms, the optimized structures of 12o and 13o showed According to their structures in Fig. 4, the crown ether com-
good symmetry. The dihedral angles between the cyclopentene ponents presented the obviously tortuous configuration ascrib-
ring and the two thiophene rings of 12o were 43.91(1)° and ing to the flexible ethylene glycol chains. The dihedral angles
49.15(2)°, respectively. The distance between the centers of the between the cyclopentene ring and the two thiophene rings of
two thiophene rings was 5.011(1) Å. Furthermore, the unparal- 19o were 51.16(1)° and 46.16(2)°, respectively. The distance
lel confirmation of this molecule was useful for the photo between the centers of the two thiophene rings was 4.987(1) Å.
cyclization reaction to take place.2a In addition, the distance The distance between the two reactive carbons of 19o is
between the two reactive carbons was 3.667 Å (in the X-ray 3.718 Å. For the open isomer of compound 19, the distance
crystal structure, it was 3.998 Å), which was short enough for between the CB ring and the switch unit was from 4.954(2) Å
the cyclization reaction to take place. Photochromic reactivity to 5.429(2) Å while the distance was from 6.185(1) Å to 6.632(2)
usually only appears when the distance between the reactive Å in the closed isomer of compound 19. As early as 1986,
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Mock has reported that the dissociation constant of cucurbit The theoretical calculation in the present study was performed
[6]uril with ammonium of 1,6-diaminohexane was less than at the B3LYP/6-31G* level, using the Gaussian 09 program.
4 × 10−7 15
.
We have also confirmed the strong affinity between
Synthesis of 3
cucurbituril and ammonium in our previous work.16 This indi-
cated that the binding is not flexible. Furthermore, from the To a solution of 1 (0.50 g, 1.6 mmol) in anhydrous EtOH
structure of 19, the ring of cucurbituril has bigger rigidness (80 mL) was added 3,5-dimethoxybenzylamine (1.06 g,
and steric hindrance, possibly resulting in an increase in the 6.32 mmol) with anhydrous magnesium sulfate acting as a
ratio of antiparallel : parallel conformations, which was in drying agent under a nitrogen atmosphere. The mixture was
good agreement with a previous report by Takeshita and Irie.8 refluxed for 24 h. After removing the solvent, the compound
For crown ether-based rotaxanes, the binding constant was dissolved in anhydrous MeOH (50 mL) and THF (50 mL),
between crow ether and ammonium is less than 103 M−1 17
.
and sodium borohydride (605 mg, 16 mmol) was added under
Therefore, the crown ether components of rotaxanes 12 and 13 a nitrogen atmosphere. The mixture was reacted under dark
were more flexible than the cucurbituril components of rotax- conditions overnight at room temperature. The mixture was
ane 19 in the process of transformation from antiparallel to quenched with ice water, extracted with DCM, dried over
parallel conformations.
sodium sulfate, and upon removal of the solvent under
reduced pressure it was then purified on a silica gel column
using petroleum ether–ethyl acetate (2 : 1) as the eluent to give
1
3 in 65% yield as a brown gum. H NMR (400 MHz, CDCl3): δ
Conclusions
ppm = 1.92 (s, 6H, CH3), 1.96–2.04 (m, 2H, CH2), 2.75 (t, J = 8
Hz, 4H, CH2), 3.71 (s, 4H, CH2), 3.78 (s, 12H, CH3), 3.82 (s, 4H,
CH2), 6.35 (s, 2H, thiophene-H), 6.48 (s, 4H, Ph-H), 6.58 (s, 2H,
Ph-H). 13C NMR (100 MHz, CDCl3): δ ppm = 14.28, 22.91,
38.27, 47.19, 52.31, 55.27, 99.00, 105.97, 126.44, 133.61,
134.39, 135.14, 138.58, 141.96, 160.74. ESI MS m/z = 619.5
[M + H+]; calculated exact mass = 618.5. Anal. calcd for
C35H42N2O4S2: C, 67.93; H, 6.84; N, 4.53; S, 10.36. Found: C,
67.72; H, 6.60; N, 4.25 S, 10.65.
In summary, three novel dithienylethene-based [n]rotaxanes
have been successfully synthesized, and their isomerization
properties have been investigated. The photochromic activity is
apparently improved by the introduction of cucurbit[6]uril.
Our research has indicated that the mechanically interlocked
molecules can also be considered as good candidates for
photochromic materials with excellent photoisomerization
behaviors. Further work will focus on multi-responsive
materials based on dithienylethene.
Synthesis of 4
To a solution of 3 (0.18 g, 0.3 mmol) in dry DCM (30 mL), TFA
(0.19 mL, 3 mmol) was added at room temperature. After stir-
ring for 2 h under a nitrogen atmosphere, the solvent was
removed under vacuum. The residue was dissolved in MeOH
(1.0 mL), and then saturated NH4PF6 (2.0 mL, aq) was added
Experimental
Materials and methods
All manipulations were carried out under a nitrogen atmos- to yield a pale yellow precipitate. After filtering, washing with
phere using standard Schlenk techniques, unless otherwise H2O and drying under vacuum, compound 4 was obtained as a
1
stated. THF was distilled under nitrogen from sodium-benzo- pale yellow solid in 80% yield. H NMR (400 MHz, CD3CN): δ
phenone. 1,2-Bis(5-formyl-2-methylthien-3-yl)cyclopentene (1) ppm = 1.96 (s, 6H, CH3), 2.01–2.06 (m, 2H, CH2), 2.76 (t, J = 8
was prepared by literature methods.18 2,6-Pyridinedicarbox- Hz, 4H, CH2), 3.78 (s, 2H, CH3), 3.99 (s, 4H, CH2), 4.15 (s, 4H,
aldehyde (10) and tetraethyleneglycol bis(2-aminophenyl)ether CH2), 6.52 (s, 2H, thiophene-H), 6.57 (s, 4H, Ph-H), 6.85 (sm,
(11) were prepared by modified literature methods.11c Com- 2H, Ph-H). 13C NMR (100 MHz, CD3CN): δ ppm = 13.97, 22.23,
pound 7 was synthesized by a reported method.19 All other 38.36, 45.55, 51.00, 55.68, 101.22, 108.14, 129.01, 132.26,
starting materials were obtained commercially as analytical- 134.17, 135.35, 136.61, 137.61, 161.75. ESI MS m/z = 619.6
grade and used without further purification. The relative [M − 2HPF6 + H+]; calculated exact mass = 910.2. Anal. calcd for
quantum yields were determined by comparing the reaction C35H44F12N2O4P2S2: C, 46.15; H, 4.87; N, 3.08; S, 7.04. Found:
yield with the known yield of the compound 1,2-bis(2-methyl- C, 46.38; H, 4.50; N, 3.18 S, 6.95.
5-phenyl-3-thienyl)perfluorocyclopentene.20 1H and 13C NMR
Synthesis of 8
spectra were collected on a American Varian Mercury Plus 400
1
spectrometer (400 MHz or 600 MHz). H and 13C NMR chemi- To a solution of 1 (0.50 g, 1.6 mmol) in anhydrous EtOH
cal shifts are relative to TMS. UV-Vis spectra were obtained on (80 mL) was added 7 (1.68 g, 6.32 mmol) with anhydrous mag-
a U-3310 UV Spectrophotometer. Photoisomerization measure- nesium sulfate acting as a drying agent under a nitrogen
ments were carried out under a PHK 125 W mercury lamp as atmosphere. The mixture was refluxed for 24 h. After removing
an irradiation source. The ring-opening reactions were carried the solvent, the compound was dissolved in anhydrous MeOH
out using the light of a 200 W tungsten source that was passed (50 mL) and THF (50 mL), and sodium borohydride (605 mg,
through the appropriate cutoff filter to eliminate higher energy 16 mmol) was added under a nitrogen atmosphere. The
light. The distance between the sample and the lamp is 10 cm. mixture was reacted under dark conditions overnight at room
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temperature. The mixture was quenched with ice water, mixture was reacted under dark conditions overnight at room
extracted with DCM, dried over sodium sulfate, and upon temperature. The mixture was quenched with ice water,
removal of the solvent under reduced pressure, it was then puri- extracted with DCM, dried over sodium sulfate, and upon
fied on a silica gel column using ethyl acetate as the eluent to removal of the solvent under reduced pressure, it was then puri-
give 8 in 68% yield as a brown oil. 1H NMR (400 MHz, CD3CN): fied on a silica gel column using ethyl acetate as the eluent to
δ ppm = 1.29–1.31 (m, 8H, CH2), 1.41–1.45 (m, 8H, CH2), 1.95 give 17 in 50% yield as a brown oil. 1H NMR (600 MHz,
(s, 6H, CH3), 2.00–2.04 (m, 2H, CH2), 2.47–2.53 (m, 8H, CH2), CDCl3): δ ppm = 1.32–1.38 (m, 8H, CH2), 1.48–1.49 (m, 8H,
2.72 (t, J = 8 Hz, 4H, CH2), 3.65 (s, 4H, CH2), 3.74 (s, 4H, CH2), CH2), 1.88 (s, 6H, CH3), 2.00–2.02 (m, 2H, CH2), 2.58 (t, J =
3.75 (s, 12H, CH3), 6.34 (t, J = 2 Hz, 2H, Ph-H), 6.49 (t, J = 2 Hz, 6 Hz, 4H, CH2), 2.68 (t, J = 6 Hz, 4H, CH2), 2.74 (t, J = 6 Hz, 4H,
4H, Ph-H), 6.55 (s, 2H, thiophene-H). 13C NMR (100 MHz, CH2), 3.54 (s, 4H, NH), 3.78 (s, 4H, CH2), 3.81 (s, 4H, CH2),
CDCl3): δ ppm = 14.16, 22.83, 27.19, 29.91, 38.27, 48.36, 48.72, 6.56 (s, 2H, thiophene-H), 7.31 (s, 8H, Ph-H), 7.35 (s, 2H,
48.82, 49.24, 54.03, 55.09, 55.17, 58.26, 98.52, 98.75, 106.22, Ph-H). 13C NMR (100 MHz, CDCl3): δ ppm = 14.22, 22.93, 27.25,
125.86, 133.21, 134.19, 134.98, 139.24, 142.53, 142.77, 160.45, 29.90, 30.01, 38.34, 48.43, 48.80, 49.37, 54.04, 58.25, 125.97,
160.65. ESI MS m/z = 817.7 [M + H+]; calculated exact mass = 126.64, 126.82, 128.06, 128.32, 128.70, 133.30, 134.33, 135.09,
816.7. Anal. calcd for C47H68N4O4S2: C, 69.08; H, 8.39; N, 6.86; 139.36, 139.99, 140.42. ESI MS m/z = 697.8 [M + H+]; calculated
S, 7.85. Found: C, 69.43; H, 8.62; N, 6.91; S, 7.56.
exact mass = 696.8. Anal. calcd for C43H60N4S2: C, 74.09; H,
8.68; N, 8.04; S, 9.20. Found: C, 74.20; H, 8.52; N, 8.04; S, 9.03.
Synthesis of 9
Synthesis of 18
Compound 9 was prepared by an analogous method similar to
that used for 4 and was obtained as a pale yellow solid in 60% Compound 18 was prepared by an analogous method similar
1
yield. H NMR (400 MHz, CD3CN): δ ppm = 1.35–1.37 (m, 8H, to that used for 4 and was obtained as a pale yellow solid in
1
CH2), 1.61–1.66 (m, 8H, CH2), 1.88 (s, 6H, CH3), 1.96–2.08 (m, 60% yield. H NMR (600 MHz, CD3CN): δ ppm = 1.36 (s, 8H,
2H, CH2), 2.77 (t, J = 7.2 Hz, 4H, CH2), 2. 94 (t, J = 7.6 Hz, 4H, CH2), 1.66 (s, 8H, CH2), 1.95 (s, 6H, CH3), 2.05–2.09 (m, 2H,
CH2), 3.01 (t, J = 8 Hz, 4H, CH2), 3.81 (s, 12H, CH3), 4.08 (s, CH2), 2.76 (t, J = 6 Hz, 4H, CH2), 2.96 (t, J = 6 Hz, 4H, CH2),
4H, CH2), 4.19 (s, 4H, CH2), 5.12 (br, 4H, NH+), 6.56 (t, J = 2.4 3.02 (t, J = 6 Hz, 4H, CH2), 4.17 (s, 4H, CH2), 4.20 (s, 4H, CH2),
Hz, 2H, Ph-H), 6.61 (d, J = 2.4 Hz, 4H, Ph-H), 6.96 (s, 2H, thio- 5.51 (br, 4H, NH+), 6.91 (s, 2H, thiophene-H), 7.47 (s, 10H, Ph-
phene-H), 13C NMR (100 MHz, CD3CN): δ ppm = 13.93, 25.73, H). 13C NMR (100 MHz, CD3CN): δ ppm = 13.97, 23.33, 25.61,
45.74, 47.37, 47.99, 51.84, 55.69, 101.36, 108.18, 109.13, 38.19, 45.71, 47.27, 47.93, 51.87, 52.35, 57.64, 128.20, 129.58,
128.04, 132.59, 133.48, 135.38, 136.62, 137.83, 161.76. ESI MS 129.77, 130.07, 130.57, 131.67, 132.56, 136.68, 137.76. ESI MS
m/z = 817.7 [M − 3HPF6 − PF6−]; calculated exact mass = m/z = 697.6 [M − 4HPF6 + H+]; calculated exact mass = 1280.6.
1400.4. Anal. calcd for C47H72F24N4O4P4S2: C, 40.29; H, 5.18; Anal. calcd for C43H64F24N4P4S2: C, 40.32; H, 5.04; N, 4.37; S,
N, 4.00; S, 4.58. Found: C, 40.11; H, 4.96; N, 3.78; S, 4.48.
5.01. Found: C, 40.02; H, 5.02; N, 4.25; S, 5.03.
Synthesis of 16
Synthesis of 12
A solution of 1,6-hexanediamine (5.80 g, 50 mmol) in DCM A mixture of 4 (91 mg, 0.1 mmol), tetraethyleneglycol bis(2-
(100 mL) was cooled in an ice bath under a nitrogen atmosphere aminophenyl) ether (75 mg, 0.2 mmol) and 2,2′-(pyridine-2,6-
and benzyl chloride (1.27 g, 10 mmol) in DCM (40 mL) was diyl)diacetaldehyde (27 mg, 0.2 mmol) was stirred for 5 d in
added dropwise to the above solution. This solution was stirred dry CH3CN (20 mL) under a nitrogen atmosphere at room
for 24 h at 0 °C. After removing the solvent, the compound was temperature. Then, BH3·THF solution (1.6 mL) was added, and
dissolved in ethyl ether. After filtering, the solvent was removed the mixture was further stirred overnight. The solvents were
from the filtrate to give a white solid in a yield of 50%. 1H NMR removed under vacuum, and the residue was purified by
(400 MHz, CDCl3): δ ppm = 1.34 (s, 8H, CH2), 2.64 (t, J = 7.2 Hz, column chromatography (silica gel, DCM–MeOH = 25 : 1) to
4H, CH2), 3.78 (s, 2H, CH2), 7.28–7.31 (br, 5H, ph-H). 13C NMR give the 12 in 35% yield. 1H NMR (400 MHz, CD3CN): δ ppm =
(100 MHz, CDCl3): δ ppm = 26.77, 27.18, 33.71, 42.13, 49.37, 1.95 (s, 6H, CH3), 1.95–1.96 (m, 2H, CH2), 2.19 (t, J = 8 Hz, 4H,
54.05, 126.84, 128.08, 128.34. ESI MS m/z = 207.2 [M + H+]; cal- CH2), 3.36 (s, 12H, CH3), 3.41–3.52 (m, 4H, CH2), 3.62–3.64 (m,
culated exact mass = 206.2. Anal. calcd for C13H22N2: C, 75.68; 4H, CH2), 3.72–3.73 (m, 8H, CH2), 3.76–3.78 (m, 8H, CH2),
H, 10.75; N, 13.58. Found: C, 75.58; H, 10.85; N, 13.58.
3.79 (s, 4H, CH2), 3.87 (m, 2H, CH2), 3.91–3.93 (m, 6H, CH2),
3.98 (s, 2H, CH2), 4.10–4.14 (m, 6H, CH2), 4.47 (s, 2H, CH2),
4.66 (s, 2H, CH2), 4.67 (s, 2H, NH), 4.80 (s, 2H, NH), 5.87 (s,
Synthesis of 17
To a solution of 1 (0.50 g, 1.6 mmol) in anhydrous EtOH 1H, Ar), 6.01 (d, J = 2.4 Hz, 3H, Ar), 6.23 (d, J = 2 Hz, 2H, Ar),
(80 mL) was added 16 (1.30 g, 6.32 mmol) with anhydrous 6.38 (s, 3H, Ar), 6.54 (s, 2H, thiophene-H), 6.62 (s, 3H, Ar),
magnesium sulfate acting as a drying agent under a nitrogen 6.70–6.71 (m, 9H, Ar), 6.87 (s, 2H, Ar), 7.26 (d, J = 8.0 Hz, 1H,
atmosphere. The mixture was refluxed for 24 h. After removing Ar), 7.38 (d, J = 8.0 Hz, 3H, Ar), 7.82 (t, J = 8.0 Hz, 1H, Ar), 9.02
the solvent, the compound was dissolved in anhydrous MeOH (s, 4H, NH2+). The 13C NMR spectrum was not collected due to
(50 mL) and THF (50 mL), and sodium borohydride (605 mg, the poor solubility of [3]rotaxane 12. MALDI TOF m/z = 1577.84
16 mmol) was added under a nitrogen atmosphere. The [M − HPF6 − PF6−]; calculated exact mass = 1868.69. Anal.
7718 | Org. Biomol. Chem., 2014, 12, 7712–7720
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calcd for C89H110F12N8O14P2S2: C, 57.17; H, 5.93; N, 5.99; S, (201271130441). The work was also supported by the Scientific
3.43. Found: C, 57.43; H, 5.57; N, 5.80; S, 3.60.
Research Foundation for the Returned Overseas Chinese Scho-
lars, the Ministry of Education, the Natural Science Foundation
of Hubei Province (2013CFB207) and the Key Laboratory of
Pesticide and Chemical Biology for financial support (grant no.
201301A01). We thank Prof. Juyoung Yoon at Ewha Womans
University in Korea for his support and dedicate to him on the
occasion of his 50th birthday.
Synthesis of 13
A mixture of 9 (91 mg, 0.1 mmol), tetraethyleneglycol bis(2-
aminophenyl) ether (75 mg, 0.2 mmol) and 2,2′-(pyridine-2,6-
diyl)diacetaldehyde (27 mg, 0.2 mmol) was stirred for 5 d in
dry CH3CN (20 mL) under a nitrogen atmosphere at room
temperature. Then, BH3·THF solution (1.6 mL) was added, and
the mixture was further stirred overnight. The solvents were
removed under vacuum, and the residue was purified by
column chromatography (silica gel, DCM–MeOH = 40 : 1) to
give 13 in 30% yield. 1H NMR (600 MHz, CD3CN): δ ppm =
0.80–0.86 (m, 8H, CH2), 1.21–1.28 (m, 3H, CH2), 1.42–1.48 (m,
5H, CH2), 1.95 (s, 6H, CH3), 1.96–1.98 (m, 2H, CH2), 2.09 (s,
4H, CH2), 2.72 (s, 2H, CH2), 2.88 (d, J = 5.4 Hz, 5H, CH2), 3.37
(s, 6H, CH2), 3.46–3.59 (m, 11H, CH2), 3.63–3.74 (m, 34H,
CH2), 3.81–3.98 (m, 16H, CH2), 4.00–4.07 (m, 6H, CH2),
4.13–4.25 (m, 16H, CH2), 4.40 (s, 3H, CH2), 4.50 (s, 2H, CH2),
4.59 (s, 2H, CH2), 4.77 (s, 2H, CH2), 4.90 (s, 3H, CH2), 5.45 (s,
8H, NH), 6.00 (s, 2H, Ar), 6.23 (s, 3H, Ar), 6.32 (s, 2H, thio-
phene-H), 6.46–6.49 (m, 8H, Ar), 6.60–6.79 (m, 16H, Ar), 6.87
(d, J = 13.2 Hz, 6H, Ar), 7.37–7.40 (m, 7H, Ar), 7.63 (s, 2H, Ar),
Notes and references
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+
7.84 (s, 4H, Ar), 8.15 (s, 2H, Ar), 8.68 (s, 4H, NH2 ), 8.90 (s, 4H,
+
NH2 ). The 13C NMR spectrum was not collected due to the
poor solubility of [5]rotaxane 13. MALDI TOF m/z = 2735.13
[M − 3HPF6 − PF6−]; calculated exact mass = 3317.32. Anal. calcd
for C155H204F24N16O24P4S2: C, 56.08; H, 6.19; N, 6.75; S, 1.93.
Found: C, 56.21; H, 6.06; N, 6.74; S, 1.90.
Synthesis of 19
To a solution of 18 (0.32 g, 0.25 mmol) in H2O, cucurbit[6]uril
(0.75 g, 0.75 mmol) was added and the mixture was refluxed
for 24 h under a nitrogen atmosphere. After cooling, the
mixture was filtered and the filtrate was treated with saturated
NH4PF6 (2 mL, aq) to yield a white precipitate. The solid was
collected by filtration, washed with water and dried under
1
vacuum to give the title compound 19, 0.49 g in 45% yield. H
NMR (600 MHz, CD3CN): δ ppm = 0.45 (s, 8H, CH2), 0.81 (s,
8H, CH2), 1.95 (s, 6H, CH3), 2.04–2.09 (m, 2H, CH2), 2.79 (s,
4H, CH2), 3.01 (t, 4H, CH2), 4.16–4.25 (m, 24H, CB), 4.27 (s,
4H, CH2), 5.36 (s, 4H, CH2), 5.39–5.45 (m, 24H, CB), 5.51 (s,
4H, CH2), 5.72–5.75 (m, 24H, CB), 7.13 (s, 2H, thiophene-H),
7.45 (s, 8H, Ph-H), 7.66 (s, 2H, Ph-H). The 13C NMR spectrum
was not collected due to the poor solubility of pseudo[3]rotax-
ane 19. MALDI TOF m/z = 2837.10 [M − 3HPF6 − PF6−]; calcu-
lated
exact
mass
=
3272.90.
Anal.
calcd
for
C115H136F24N52O24P4S2: C, 42.18; H, 4.19; N, 22.24; S, 1.96.
Found: C, 42.48; H, 4.19; N, 24.54; S, 1.94.
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We acknowledge financial support from the National Natural
Science Foundation of China (20931006, 21072070, 21272088)
and the Program for Academic Leader in Wuhan Municipality
This journal is © The Royal Society of Chemistry 2014
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Paper
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