Pseudo[n,m]rotaxanes of Cucurbit[7/8]uril and Viologen-Naphthalene Derivative: A Precise Definition of Rotaxane

Article abstract of DOI:10.1002/cjoc.201800562

Rotaxane is a kind of classic supramolecule, which is usually constructed from a number of macrocycles and one axis molecule. Herein, we have expanded the supramolecular structure of [n]rotaxane to offer a precise definition of (pseudo)[n,m]rotaxane for a

Full text of DOI:10.1002/cjoc.201800562

cucurbit[7/8]uril, (pseudo)rotaxanes, self-assembly,
host-guest interaction, supramolecular chemistry
中
国 化 学
Pseudo[n,m]rotaxanes of Cucurbit[7/8]uril and Viologen-Naphthalene
Derivative: A Precise Definition of Rotaxane
a,ǂ
a,b,ǂ
a
a
a
,a
Beilin Zhang, Yunhong Dong,
Jie Li, Yang Yu, Chenyang Li, and Liping Cao*
a
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the Ministry of Education, College of Chemistry and Materials Science,
Northwest University, Xi’an, Shaanxi 710069, China
b
National Demonstration Center for Experimental Chemistry Education, College of Chemistry and Materials Science, Northwest University, Xi’an,
Shaanxi 710069, China
Cite this paper: Chin. J. Chem. 2019, 37, 269—275. DOI: 10.1002/cjoc.201800562
Summary of main observation and conclusion Rotaxane is a kind of classic supramolecule, which is usually constructed from a number of macrocycles
and one axis molecule. Herein, we have expanded the supramolecular structure of [n]rotaxane to offer a precise definition of (pseudo)[n,m]rotaxane for
accurately describing the two kinds of (pseudo)rotaxanes structures, which are self-assembled from cucurbit[7/8]uril (CB[7/8]) and viologen-naphthalene
derivative, respectively. Furthermore, these CB-based pseudorotaxanes exhibit varied photophysical properties, stimuli-responsive behavior triggered by
competitive guest, and self-sorting behavior.
Background and Originality Content
the supramolecular structures of [n]rotaxane to offer a precise
definition of (pseudo)[n,m]rotaxanes, where 'n' represents the
number of axis molecules and 'm' represents the number of mac-
rocyclic molecule, for accurately describing the assembled struc-
tures of (pseudo)rotaxanes (Scheme 1c).
In recent decades, mechanically interlocked molecules (MIMs)
have received considerable attention as molecular machines (e.g.
[
1]
[2]
molecular switches, molecular motors and molecular cata-
[
3]
lysts ), which can be defined as a kind of functional supramolec-
ular structure formed from a number of discrete molecular units
through non-covalent interactions. For examples, rotaxanes, cat-
enanes, and knots, as classic MIMs, have been widely studied
due to not only their fascinating supramolecular architectures but
The cucurbit[n]uril family (n = 5—8, 10) formed from cyclic
methylene-bridged glycoluril oligomers possess a hydrophobic
[7]
cavity and two cyclic carbonyl portals. They can bind various
[
4]
organic molecules through hydrophobic interaction and van der
Waals interactions of the cavity or hydrogen bond and ion-dipole
[
5]
also their potential applications. One of the most popular MIMs
[8]
interactions of carbonyl groups at two cyclic portals. As a result,
[
6]
is rotaxane, defined by Schill in 1971. Usually, it contains one or
several cyclic molecules (roda) and a linear molecule (axis). The
linear and cyclic molecules are held by supramolecular interac-
tions "mechanical-bonding" rather than by covalent or coordinate
bonds. To prevent cyclic molecules from sliding out of linear mol-
ecule, two groups of sufficiently large size are applied to the
stopper at both ends of the molecule. If the linear molecule can
be removed from the inner cavity of the cyclic molecules, the
supramolecule formed by cyclic and linear molecules is called
pseudorotaxane.
cucurbit[n]uril can choose guest molecules with an appropriate
size to form inclusion complexes, and then assemble into MIM
structures. In the cucurbit[n]uril family, cucurbit[7]uril (CB[7]) has
a cavity with the portal diameter of 5.4 Å and an inner diameter is
7
.3 Å, which can encapsulate one aromatic guest to form binary
[9]
complex. Compared with CB[7], cucurbit[8]uril (CB[8]) has a
larger cavity, with the portal diameter of 6.9 Å and an inner diam-
eter is 8.8 Å, which can form ternary complexes by encapsulating
[10]
two identical (e.g., diphenylpyridinium ) or different (e.g.,
[11,12]
naphthalene units and the viologen segments
) guest mole-
In previous reports, people often use [n]rotaxane to represent
different structures of rotaxanes, where 'n' represents the number
of assembled molecules, containing both cyclic and linear mole-
cules. However, the assembled structures of rotaxanes are be-
coming diversity, which results in that a simple 'n' cannot accu-
rately represent a complicated assembled structure (Scheme 1a).
For example, [3]rotaxane, referring to two possible assembled
modes: 1) one linear molecule and two macrocycles; 2) two linear
ones and one macrocycle (Scheme 1b). Herein, we have expanded
cules. Therefore, CB[7/8] are suitable building blocks for con-
structing various (pseudo)rotaxane.
Recently, supramolecular chemists have used CB[n] as a mac-
rocyclic host to synthesize many disperse rotaxanes or infinite
polyrotaxanes through their unique host-guest properties. For
example, one-dimensional (pseudo)rotaxanes based on CB[n]
[13]
from 1 : 1 or 1 : 2 stoichiometry,
(
two-dimensional network
[14]
[15
pseudo)rotaxanes (e.g., polyrotaxane, molecular necklace ]),
and extended three-dimensional (pseudo)rotaxanes, have been
constructed to exhibit applications in cell imaging, supramolec-
[16]
[
17]
[
18]
[19]
Scheme 1 Cartoon illustrations of propose definition of [n,m]rotaxanes
ular organic framework,
white-light emissions,
and so on.
Specifically, CB[8]-based pseudorotaxanes have exhibited a dis-
crete structure of novel 2 : 2 model system of host-guest inclu-
[
20]
sions.
For example, Scherman and co-workers studied CB[8]-
diarylviologen host-guest complexes and verified them to be 2 : 2
quaternary complexes rather than previously reported 1 : 1 binary
[21]
complexes. In this paper, we obtained two kinds of 1 : 2 and 2 :
CB-based pseudorotaxanes formed from CB[7/8] and viologen-
2
ǂ
*
E-mail: chcaoliping@nwu.edu.cn. These authors contributed equally.
For submission: https://mc.manuscriptcentral.com/cjoc
For articles: https://onlinelibrary.wiley.com/journal/16147065
†
Dedicated to the Special Issue of “Supramolecular Chemistry”.
Chin. J. Chem. 2019, 37, 269－275
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
269

Comprehensive Report
Zhang et al.
1
naphthalene derivative (1), respectively. According to our precise
definition for rotaxane, 2+2 quaternary complex between vio-
logen-naphthalene derivative and CB[8] can be represented as
pseudo[2,2]rotaxane rather than just pseudo[4]rotaxane, and 1+2
ternary complex between viologen-naphthalene derivative and
CB[7] can be represented as pseudo[1,2]rotaxane rather than just
pseudo[3]rotaxane (Scheme 2). Following this way, complicated
CB[7/8]. H NMR titration experiments were performed by adding
0—2.0 equiv. of 1 to a solution of CB[8] (0.5 mmol/L) in D O (Figure
2
2). When 0—1.0 equiv. of 1 was added to a solution of CB[8] (0.5
mmol/L), the signals of free 1 disappeared completely and only
one new set of resonances showed up, indicating the formation of
supramolecular assembly with 1 : 1 binding stoichiometry (Figure
2a—d). All the proton signals of the naphthalene ring were fully
assigned based on a H- H COSY experiment (Figures S4). Com-
pared with the peaks of free 1, we found that there were obvious
upfield shift (Δδ = ~1.0) of the protons (Ha'-g') on the naphthalene
ring, which indicated that CB[8] bound with the naphthalene ring
moiety at two terminals rather than the viologen moiety in the
middle of the guest. And one of the viologen protons (Hh’) exhib-
ited slight upfield shift by approximately δ 0.04, suggesting an
inclusion near the portal of CB[8] and average signals deriving
from a partial inclusion and partial exclusion by the cavity; anoth-
er viologen proton (Hi') shifted downfield slightly by approximately
δ 0.09, suggesting a location near the carbonyl portal yet outside
the CB[n] cavity. Compared with free CB[8], all the resonance
1
1
(pseudo)rotaxanes can be named easily.
Scheme 2 Schematic illustration of pseudo[2,2]rotaxane 1
2 2
•CB*8+ and
pseudo[1,2]rotaxane 1•CB*7+
2
Results and Discussion
Viologen derivatives as their cationic property and suitable
size are suitable recognition units of guests for fabricating host-
[
21,22]
guest complex with cucurbit[n]uril.
Therefore, we designed
and synthesized a linear and water-soluble guest, 2,2'-dinaphtha-
lene-4,4'-bipyridine-1,1'-diium dichloride (1), containing a vio-
logen unit in the middle and two naphthalene ring units at both
terminals. Guest 1 was synthesized by the Zincke reaction of
2
1
-naphthylamine with N,N'-bis(2,4-dinitrophenyl) 4,4'-bipyridine-
,1'-diium chloride salt, in 89% yield.
Figure 1 The single-crystal X-ray structures of (a) a single molecule of 1;
(b) side view of stacking structure 1•1 from the b axis and (c) front view of
stacking structure 1•1 from the c axis. Color code: C, grey; N, blue. Hydro-
gen atoms and chloride ions to balance the charge have been omitted for
clarity.
Fortunately, we obtained brown needle-like single crystals of 1
from MeOH solution by slow vapor diffusion of iPr O at room
2
temperature. Figure 1 illustrates the single molecule and stacking
structures of 1. The dihedral angle of two pyridine rings units in
o
the center of 1 is about 37.4 , while the dihedral angle of the two
o
naphthalene rings at two terminals is about 24.5 . And the dihe-
dral angles of two pyridine ring and their adjacent naphthalene
o
o
rings are about 31.6 and 33.4 , respectively. Subsequently, as
shown in Figure 1b, the adjacent molecules with each other are
arranged in a parallel and partially overlapped pattern of stacking
along c axis in stacking layers. Between the layers, both of the
adjacent naphthalene rings, naphthalene ring and the viologen
ring are stacked by π•••π interactions (d = ~3.48 Å). The front view
of stacking structure 1•1 is alternate permutation from the c axis
in Figure 1c. Furthermore, the adjacent layers of 1 are connected
with each other by the solvent molecules and anions to form a 3D
structure through weak non-covalent interactions (Figure S3).
Based on the different size of CB*7/8+’s cavities, CB*7+ can just
bind one molecule, while CB[8] with a large cavity can encapsulate
two liner molecules simultaneously to form a multiaxial (pseudo)-
rotaxane. Therefore, we presumed that viologen-naphthalene
derivative 1 would be self-assembled with CB[7/8] to generate
two kinds of pseudorotaxanes by the host-guest interaction with
different stoichiometric ratios. Initially, we used NMR and ITC
technology to research the self-assembly behavior between 1 and
1
Figure 2 H NMR spectra recorded (400 MHz, 298 K, D
2
O) for: (a) CB[8]
(0.5 mmol/L), (b) 1 (0.5 mmol/L), (c) CB[8] (0.5 mmol/L) and 1 (0.5 equiv.),
(d) CB[8] (0.5 mmol/L) and 1 (1.0 equiv.) , (e) CB[8] (0.5 mmol/L) and 1 (2.0
equiv.). Here, primes (’) denote resonances within the host-guest com-
plexes.
270
www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, 269－275

A Precise Definition of Rotaxane
Chin. J. Chem.
peaks of bound CB[8] shifted upfield slightly (δ 0.05—0.08) (Figure
the addition of over 2.0 equiv. of CB[7] into 1, the resonances did
not further shift, indicating that the stoichiometry of the complex
between 1 and CB[7] is 1 : 2 ratio (Figure S7). ITC curves fitted well
to a 1 : 2 binding model with n = 0.58 with binding constants K =
(3.74 ± 0.72) × 10 L∙mol (Figure S9). In addition, we only found 1
+ 1 complex of CB[7] and 1 through the electrospray ionization
mass spectrometry (ESI-MS), which suggested that pseudo[1,2]-
2
2
d). Moreover, the signals of free 1 could be observed by adding
.0 equiv. of 1 (Figure 2e), indicating a slow exchange between
bound and unbound 1 on the NMR time scale. Furthermore, when
more 1 existed, the protons (Hh') of viologen exhibited slight
6
–1
downfield shift by approximately δ 0.08 and another proton (Hi'
)
split into two signals. The DOSY experiment was performed to
explain the change of these protons. In Figure S5, two sets of dif-
rotaxane (1•CB[7]
MS (Figure S10). By comparing two sets of diffusion coefficients of
•CB[8] and 1•CB[7] , we found diffusion coefficient of 1 •CB[8]
is smaller than that of 1•CB[7] (Figure 4b), which confirmed
•CB[8] possessed more larger self-assembled systems with 2 +
2
) may be unstable under the condition of ESI-
–
10
2 –1
ferent diffusion coefficients of (1.758 ± 0.144) × 10 m ∙s and
–
10
2 –1
(
3.522 ± 0.100) × 10 m ∙s were observed, respectively. It indi-
cates the existence of two species of different sizes, so we con-
cluded that the split signals (H ') belonged to free and complexed
, the average proton (H ') signals derived from partial inclusion
1
2
2
2
2
2
2
i
1
2
2
1
h
2 mode. Furthermore, Job's plot by using UV-vis spectroscopy
displays a maximum absorption change at 0.3 and 0.5 (Figures S11
and S12), which confirmed that the stoichiometry of the complex
and partial free in Figure 2e.
The stoichiometry of the complex between 1 and CB[8] is 1 : 1
ratio as well as the isothermal titration calorimetry (ITC) (Figure
between 1 and CB[7/8] is 1 : 2 for pseudo[1,2]rotaxane (1•CB[7]
and 2 : 2 for pseudo[2,2]rotaxane (1 •CB[8] ), respectively.
2
)
3
a). The ITC curves fitted well to a 1 : 1 binding model with a high
2
2
7
–1
a
binding constant of K = (1.06 ± 0.33) ×10 L∙mol , suggesting that
the strong binding facilitates the stable self-assemblies in water.
However, in the present case of (1•CB[8]) , the binding stoichiom-
n
etry is clearly 2 : 2 rather than 1 : 1, confirmed through the elec-
trospray ionization mass spectrometry (ESI-MS), NOESY NMR, and
2
D diffusion ordered spectroscopy (DOSY) (Figures 3, 4, S6). In the
ESI-MS spectrum, not only 1 + 1 complex of CB[8] and 1 but also 2
2 were observed, which confirmed that a quaternary complex,
pseudo[2,2]rotaxane (1 •CB[8] ) may exist. NOESY NMR was em-
+
2
2
ployed to further confirm our quaternary binding model and to
investigate the stacking model of the two 1 molecules within the
cavity of CB[8] (Figure 3b). In NOESY spectrum, there were Hg'-He'
and Hb'-Hd' inter-correlation between two naphthalene rings,
suggesting that one benzene ring of naphthalene moiety in the
complex should indeed be close to the benzene ring from another
naphthalene moiety, and two complexed 1 molecules likely stack
with each other in a partially overlapped pattern rather than di-
rectly stacking of each other. As a result, each CB[8] molecule
includes two naphthalene groups from the neighboring two guest
molecules with a face-to-face arrangement, and the inclusion
mode is a 2 : 2 binding motif to form pseudo[2,2]rotaxane. Mean-
while, DOSY further confirmed the formation of a single species in
-
10
the solution with diffusion coefficient of (1.571 ± 0.065) × 10
2
–1
m ∙s , which is much lower than that of 1 : 1 complex (Figure 4a).
Figure 4 DOSY spectra recorded (600 MHz, D
and (b) 1•CB[7] . [1] = 0.5 mmol/L.
2
O, 298 K) for (a) 1
2
•CB[8]
2
2
To explore the photophysical properties of 1 and CB[7/8] in
aqueous solution, UV-vis and fluorescence titration experiments
were performed. First, the UV-vis spectrum of 1 displayed two
significant absorption bands centered approximately at 260 and
3
30 nm (Figure 5a), which are assigned to viologen unit in the
middle and naphthalene rings contained in 1. Under the addition
of 1.0 equiv. of CB[8] into the aqueous solution of 1, a remarkable
red shift (Δλ = 37 nm) of the peak around 330 nm and one shoul-
der at 464 nm were observed, ascribing to the charge transfer (CT)
process between host and guest. A similar situation also occurs in
Figure 3 (a) ITC data for the titration of CB[8] (20 μmol/L) in the cell with
a solution of 1 (180 μmol/L) in the syringe in H O at 298 K. (b) NOESY NMR
O, 298 K, 1 mmol/L) of 1 •CB[8]
2
the UV-vis titration experiment of 1•CB[7] : the one absorbance
2
spectrum recorded (400 MHz, D
2
2
2
.
maxima was red-shifted (Δλ = 13 nm) from 329 nm to 342 nm,
and a CT band at around 433 nm came out (Figure S13). Then,
fluorescence titration experiments were performed to investigate
the fluorescent emission properties of 1 and 1•CB[7/8] complexes.
1
Similarly, H NMR titration experiment was also performed to
research the host-guest interaction between 1 and CB[7] (Figure
S7). There were significant changes of the protons on naphthalene, With constantly adding CB[8] in an extremely dilute solution of 1
which were attributed to the shielding effect exerted by the cavity
of CB[7]. All the proton signals of the naphthalene ring were fully
assigned based on a H- H COSY experiment (Figure S8). Under
in water, the characteristic of the dual emission was observed,
which indicated that the luminescence property originated from
the intermolecular interactions (Figures 5b—c): The intensity of
1
1
Chin. J. Chem. 2019, 37, 269－275
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
271

Comprehensive Report
Zhang et al.
–6
Figure 5 UV-vis absorption (a) and Fluorescence spectra (b) of 1 (10 × 10 mol/L) in water upon addition of CB[8]. The inset shows a plot of absorbance
intensity at 450 nm and fluorescence intensity at 530 nm versus CB[8] concentration. (c) 1931 CIE chromaticity coordinate changes of 1 (10.0 μmol/L) in
the presence of CB[8] (0, 0.5, 1.0, 2.0, 3.0 equiv.). The inset shows the examples of fluorescence photographs with CIE coordinate (from left to right) of
2
1 •CB[8]
2 2 2
(1.0 mmol/L) from bluish violet to orange under the ultraviolet lamp. (d) Fluorescence(2D) spectrum recorded of 1 •CB[8] . The insets show a
plot of fluorescence intensity varying with time under 530 nm. λex = 340 nm, Ex/Em slit = 5 nm.
monomer emission of 1 at 409 nm decreased, accompanied by
the appearance of a new emission peak at 535 nm with Δλ = 126
nm, indicating the formation of host-guest complexes with dual
guests. Both the UV-vis and fluorescence titration experiments of
iment. When 1.0 equiv. of Me
2
ADA was added to the solution of
1
2
•CB[8] , the emission intensity of the complex decreased at 536
2
nm and the emission intensity of free 1 gradually increased at 406
nm, suggesting that most of the guest is out of the CB[8] cavity. It
is because the binding affinity of 1 with CB[8] is weaker than that
1
2 2
with CB[8] established a 2 : 2 stoichiometry of 1 •CB[8] . Inter-
estingly, 2D time-dependent fluorescence experiment was per-
formed to research the binding process of 1 and CB[8], suggesting
the formation of stable host-guest complex needed about 12 min
at least (Figure 5d). Similarly, the emission intensity at 409 nm
was gradually decreased and a new emission peak at 524 nm ap-
peared by adding CB[7]. However, the intensity of new peak re-
mained stable when adding an excess of CB[7] ( 2.0 equiv.) (Figure
S14), which supports that the formation of supramolecular as-
of Me
2
ADA with CB[8] (Figure S16). This result was also confirmed
by H NMR titration experiments (Figure S17). When 3.0 equiv. of
Me ADA was added, most of the guests came out of the CB[8]'s
cavity. These experiments indicate a transformation form 1 •CB[8]
By contrast to
CB[8], we performed H NMR titration of competitive experiment
among 1, Me ADA and CB[7] (Figure S18). When 6.0 equiv.
Me ADA was added, no guest came out of the CB[7] cavity, sug-
gesting that the binding constant of 1•CB[7] is stronger than that
of Me ADA with CB[7].
To understand the thermodynamic properties of the pseudo-
[2,2]rotaxane (1 •CB[8] ) and pseudo[1,2]rotaxane (1•CB[7] ), the
temperature-dependent fluorescence experiments were per-
formed. The emission of 1 •CB[8] decreased at 536 nm and the
1
2
2
2
[
23]
2
to the highly stable CB[8]•Me ADA complex.
1
2
2
sembly of 1•CB[7]
2
is 1 : 2 stoichiometry. Comparing the two fluo-
2
rescent experiments of pseudo[2,2]rotaxane and pseudo[1,2]-
rotaxane, we found that these two pseudorotaxanes exhibited
large but varying red-shifting. This observation indicated that the
assembled models about 1 with the different ratio of CB[7/8]
were definitely different. The two molecules array with a face-to-
face stacking pattern in CB[8]s' cavity, which enhanced the su-
pramolecular conjugation and electron transfer process. In the
contrast, two CB[7] molecules were at the terminal of the guest
molecules, the result of this ability of supramolecular conjugation
is lower than that of pseudo[2,2]rotaxane, so the red-shift dis-
tance is shorter than that of pseudo[2,2]rotaxane. The 1931 CIE
chromaticity coordinate changes of 1 in the presence of CB[7/8]
are summarized in Figure 5c and Figure S15, respectively. The
fluorescent colors of the system of 1 with different ratio of CB[8]
were changed from bluish violet to orange. However, with the
different ratio of CB[7], the fluorescent colors of the system
changed from bluish violet to pale yellow, including a near white-
light emission (0.33, 0.37).
2
2
2
2
2
2
emission of free guest increased at 406 nm when the temperature
rose from 278 K to 343 K (Figure 6a), suggesting the gradual dis-
sociation of 1 •CB[8] . In the case of 1•CB[7] , the maximum emis-
2 2 2
sion showed blue shift from 524 nm to 503 nm under the incre-
ment of external temperature. In this process, one of the two
CB[7] would separate from the assembly system (Figure S19).
Temperature-dependent H NMR and fluorescence experiments
2 2
showed that pseudo[2,2]rotaxane (1 •CB[8] ) and pseudo[1,2]-
rotaxane were not stable and could be destroyed at higher tem-
perature (Figure S20).
The aggregation behavior of 1•CB[7/8] was also investigated
by fluorescence experiments. As seen in Figures 6b and S21, the
1
2 2
fluorescence intensity of 1 •CB[8] at 540 nm increased linearly as
In order to further investigate the binding affinity between
CB[7/8] and 1, we chose a tight binding guest, 3,5-dimethyl-1-
the concentration was gradually raised from 2.0 to 28.2 μmol/L,
and then slowly increased from 28.2 to 100 μmol/L, which implies
that the critical aggregate concentration (CAC) of 1 •CB[8] is
2 2
adamantylamine•HCl (Me
2
ADA), to perform a competitive exper-
272
www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, 269－275

A Precise Definition of Rotaxane
Chin. J. Chem.
creased linearly with the concentration from 2.0 to 27.4 μmol/L
and from 27.4 to 100 μmol/L at 522 nm, respectively, which im-
plies that the CAC of 1•CB[7]
fore, we concluded that the aggregate state of 1•CB[7]
2
is 27.4 μmol/L (Figure S22). There-
at higher
2
concentration was through non-covalent interactions (e.g., π-π
interactions), which could cause aggregation-caused quenching
[
24]
(
ACQ) effect. In addition, quantum yields (Φ) and fluorescence
lifetime (τ) of 1 •CB[8] and 1•CB[7] were measured (Table S1).
The quantum yield of 1 •CB[8] and 1•CB[7] increased to 7.31%
and 4.49%, respectively (ΦF,1 = 2.24%). Both 1 •CB[8] and
•CB[7] displayed two decay kinetics. Compared with 1, the rela-
tively higher τ was ascribed to the host CB[n] enhancing the sta-
bility of the complexes at the excited state (Figures S23, S24).
2
2
2
2
2
2
2
2
1
2
F
[
19]
The phenomenon of molecular recognition between different
host-guest pairs without mutual interference is called ''Self-Sort-
[
25]
ing''. Scientists manage to utilize self-sorting principle to design
and construct a number of complicated systems, such as nano-
[
26]
[27]
fiber networks,
organic framework
growth,
supramolecular polymers,
supramolecular
[
28]
in varieties of applications, such as cell
[
29]
[30]
[31]
sensors,
drug solubilization,
and so on. In this
paper, a high level of affinity and selectivity between the different
guests and CB[8] is presented in self-sorting process. The self-
13c
sorting process, which involves 1 and 2 as well as cucurbit[8]uril
1
was investigated through the comparison of H NMR spectra (Fig-
1
ures 7 and S25). The H NMR spectrum of guest 1 in D
2
O was
shown in Figure S25a. Upon the addition of one equiv. of CB[8],
the strong host-guest interaction between 1 and CB[8] drove the
efficient formation of the pseudo[2,2]rotaxane (1
a). In a previous report, 2 and CB[8] were mixed in D
same molar ratio to form square [5]molecular necklace (2•CB[8])
2
•CB[8]
2
) (Figure
O in the
7
2
Figure 6 Fluorescence emission spectra: a) the plot of maximum emis-
4
sion intensity at 536 nm of CB[8]•1 as a function of temperature (5—70
o
(Figure 7b). Next, we focused on the self-sorting process of two
supramolecular assembles. As seen in Figure 7c, 1 and 2 at a mo-
lar ratio of 1 : 1 were mixed in one pot, followed by addition of
two molar equivalent of CB[8]. Interestingly, after careful analysis,
we found that the spectrum showed the same pattern with the
C). All the measurements were taken using CB[8]
2 2
•1 aqueous solution
with unified concentration (CB[8]
2
2
•1 = 10 µmol/L); b) plot of maximum
emission intensity at 541 nm of CB[8]•1 (2—100 µmol/L) in H
at 298 K. λex = 340 nm, Ex/Em slit = 5 nm.
2
O solution
1
simple spectral overlap by the comparisons of different H NMR
around 28.2 μmol/L. At high concentration, the aggregation or
packing of pseudo[2,2]rotaxane 1 •CB[8] probably enhances the
supramolecular conjugation and electron transfer process, leading
to an increase in emission and a shift from 540 nm to 556 nm. By
spectra, which can fully demonstrate that the efficiently and spe-
2
2
cifically formed 1 •CB[8] and (2•CB[8])4 are the predominant
2
2
species in this multi-component self-assembly process. It also
shows that the two guests and CB[8] have no interference when
they are assembled.
2
contrast, the emission intensity of 1•CB[7] increased and de-
1
Figure 7 H NMR spectra recorded (400 MHz, 298 K, D
2
O) for self-sorting behavior: (a) pseudo[2,2]rotaxane 1
2
•CB[8]
2
, (b) square molecular neck
4 2 2 4
(2•CB[8]) , (c) the mixture of 1 •CB[8] and (2•CB[8]) .
Chin. J. Chem. 2019, 37, 269－275
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
273

Comprehensive Report
Zhang et al.
Conclusions
Zhang, H.; Lei, J.; Carmieli, R.; Sarjeant, A. A.; Stern, C. L.; Wasielewski,
M. R.; Stoddart, J. F. Controlling Switching in Bistable [2]Catenanes
by Combining Donor−Acceptor and Radical−Radical Interactions. J.
Am. Chem. Soc. 2012, 134, 11709–11720.
In summary, two kinds of pseudorotaxanes were self-assem-
bled by viologen-naphthalene derivative (1), which were success-
fully synthesized by the Zincke reaction, and CB[7/8] through
host-guest interaction. The host-guest recognition of 1 with CB[n]
[
[
2] Lee, S.; Lu, W. The Switching of Rotaxane-Based Motors. Nano. Tech.
2011, 22, 205501.
1
was investigated by H NMR, ESI-MS, COSY, NOESY, DOSY, UV-vis
3] Cakmak, Y.; Erbas-Cakmak, S.; Leigh, D. A. Asymmetric Catalysis with
absorption and fluorescence spectra. Based on these two kinds of
pseudorotaxanes, we have expanded the definition of [n]rotaxane
to offer a precise definition, pseudo[n,m]rotaxanes, to accurately
describe the multiaxial pseudorotaxanes. This definition will help
people to easily understand the interlocking structures of compli-
cated MIMs. Furthermore, these two pseudorotaxanes exhibit
varied photophysical properties, stimuli-responsive behavior trig-
gered by competitive guest, and self-sorting behavior. We expect
these kinds of complicated supramolecular assemblies with
various supramolecular behaviors can be precisely defined and
utilized for potential applications such as molecular switches,
sensors, and even information storage.
a Mechanically Point-Chiral Rotaxane. J. Am. Chem. Soc. 2016, 138,
1749–1751.
[
[
4] Li, S.-H.; Zhang, H.-Y.; Xu, X.; Liu, Y. Mechanically Selflocked Chiral
Gemini-Catenanes. Nat. Commun. 2015, 6, 7590.
5] Xue, M.; Yang, Y.; Chi, X.; Yan, X.; Huang, F. Development of Pseu-
dorotaxanes and Rotaxanes: from Synthesis to Stimuli-Responsive
Motions to Applications. Chem. Rev. 2015, 115, 7398–7501.
[
[
[
6] Schill, G. Catenanes, Rotaxanes, and Knots. In Organic Chemistry, Vol.
22, Academic Press, New York, 1971, p. 192.
7] Lagona, J.; Mukhopadhyay, P.; Chakrabarti, S.; Isaacs, L. The Cucur-
bit[n]uril Family. Angew. Chem. Int. Ed. 2005, 44, 4844–4870.
8] Chen, Z.-H.; Zhou, F.-G.; Zhang, Y.-Q.; Zhu, Q.-J.; Xue, S.-F.; Zhu, T.
Crystal Structures of Three Host–Guest Complexes of Methylsubsti-
tuted Cucurbit[6]urils and Anthracene Derivatives. J. Mol. Struct.
2009, 930, 140–146.
[9] Choi, S.; Park, S. H.; Ziganshina, A. Y.; Ko, Y. H.; Lee, J. W.; Kim, K. A
Stable Cis-Stilbene Derivative Encapsulated in Cucurbit[7]uril. Chem.
Commun. 2003, 17, 2176–2177.
[10] Yang, B.; Yu, S.-B.; Wang, H.; Zhang, D.-W; Li, Z.-T. 2:2 Complexes
from Diphenylpyridiniums and Cucurbit[8]uril: Encapsulation-Pro-
moted Dimerization of Electrostatically Repulsing Pyridiniums. Chem.
Asian J. 2018, 13, 1312–1317.
[11] Jeon, Y. J.; Bharadwaj, P. K.; Choi, S.; Lee, J. W.; Kim, K. Supramolec-
ular Amphiphiles: Spontaneous Formation of Vesicles Triggered by
Formation of a Charge-Transfer Complex in a Host. Angew. Chem. Int.
Ed. 2002, 41, 4474–4476.
[12] Biedermann, F.; Scherman, O. A. Cucurbit[8]uril Mediated Donor-
Acceptor Ternary Complexes: A Model System for Studying Charge-
Transfer Interactions. J. Phys. Chem. B 2012, 116, 2842–2849.
[13] (a) Pessego, M.; Moreira, J. A.; Costa, A. M. R. D.; Corrochano, P.;
Poblete, F. J.; Garcia-Rio, L. Electrostatic Repulsion between Cucur-
bit[7]urils Can Be Overcome in [3]Pseudorotaxane without Adding
Salts. J. Org. Chem. 2013, 78, 3886–3894; (b) Gromov, S. P.; Veder-
nikov, A. I.; Kuz’mina, L. G.; Kondratuk, D. V.; Sazonov, S. K.; Stre-
lenko, Y. A.; Alfimov, M. V.; Howard, J. A. K. Photocontrolled Molec-
ular Assembler Based on Cucurbit[8]uril: [2+2]-Autophotocyclo-
addition of Styryl Dyes in the Solid State and in Water. Eur. J. Org.
Chem. 2010, 13, 2587–2599; (c) Baroncini, M.; Gao, C.; Carboni, V.;
Credi, A.; Previtera, E.; Semeraro, M.; Venturi, M.; Silvi, S. Light Con-
trol of Stoichiometry and Motion in Pseudorotaxanes Comprising a
Cucurbit[7]uril Wheel and an Azobenzene Bipyridinium Axle. Chem.
Eur. J. 2014, 20, 10737–10744; (d) Gamal-Eldin, M. A.; Macartney, D.
H. Cucurbit[7]uril Host–Guest Complexes and [2]Pseudorotaxanes
with N-methylpiperidinium, N-methylpyrrolidinium, and N-methyl-
morpholinium Cations in Aqueous Solution. Org. Biomol. Chem. 2013,
11, 1234–1241; (e) Jiang, W.; Wang, Q.; Linder, I.; Klautzsch, F.;
Schalley, C. A. Self-Sorting of Water-Soluble Cucurbituril Pseudoro-
taxanes. Chem. Eur. J. 2011, 17, 2344–2348; (f) Zhang, Y.; Zhou, T.-Y.;
Zhang, K.-D.; Dai, J.-L.; Zhu, Y.-Y.; Zhao, X. Encapsulation Enhanced
Dimerization of a Series of 4-Aryl-NMethylpyridinium Derivatives in
Water: New Building Blocks for Self Assembly in Aqueous Media.
Chem. Asian J. 2014, 9, 1530–1534; (g) Liu, Y.; Shi, K.; Ma, D. Wa-
ter-Soluble Pillar[n]arene Mediated Supramolecular Self-Assembly:
Multi-Dimensional Morphology Controlled by Host Size. Chem. Asian
J. 2018, DOI: 10.1002/asia.201801705; (h) Wei, P.; Yan, X.; Huang, F.
Reversible Formation of a Poly[3]rotaxane Based on Photo Dimeriza-
tion of an Anthracene-Capped [3]Rotaxane. Chem. Commun. 2014,
Experimental
General experimental methods. Starting materials were pur-
chased from commercial suppliers and used without further puri-
[
32]
fication. CB[n] (n = 7,8)
was prepared according to the pub-
lished procedure. Melting points were measured on an XT-4 ap-
paratus in open capillary tubes and are uncorrected. IR spectra
were recorded on a JASCO FT/IR 4100 spectrometer and are re-
–
1
ported in cm . UV-Vis spectra were done on Agilent Cary-100.
Fluorescence spectra were recorded on a Horiba Fluorolog-3
spectrometer. Fluorescence decay profiles were recorded on a
Flsp920. NMR spectra were measured on a spectrometer operat-
1
13
ing at 400 MHz for H and 100 MHz for C NMR spectra. Mass
spectrometry was performed using a JEOL AccuTOF electrospray
instrument (ESI). Isothermal titration calorimetry (ITC) was carried
o
out using a VP-ITC (Malvern) at 25 C, and computer fitting of the
data was performed using the VP-ITC analyze software. X-ray
crystal diffraction data for 1 were performed on a Bruker D8 Ven-
ture photon II diffractometer at low temperature (153 K) with
graphite-monochromated Mo Kα radiation (λ = 0.71073 Å).
Synthetic procedures. Compound 1: SI3 (892 mg, 1.59 mmol)
and SI4 (500 mg, 3.49 mmol) were mixed in ethanol (10 mL). After
being refluxed for 2 d, diethyl ether was added for precipitation.
The suspension was poured into a centrifuge tube and centrifuged
at 7600 r/min for 5 min at RT. The solid was washed successively
with diethyl ether (25 mL), ethyl acetate (25 mL) and acetone (25
mL). Then the solid product was dried under vacuum to give pure
–
o
–1
1
3
7
•2Cl (679 mg, 89%). m.p. 240—241 C. IR (cm ) ν: 3104m,
025m, 1623s, 1587m, 1508m, 1430m, 1329s, 1265m, 815m,
43w. H NMR (400 MHz, D
1
2
O) δ: 9.53 (d, J = 6.5 Hz, 4H), 8.85 (d,
J = 6.5 Hz, 4H), 8.42 (s, 2H), 8.30 (d, J = 8.8 Hz, 2H), 8.20—8.10 (m,
1
3
4
H), 7.89 (dd, J = 8.8, 2.1 Hz, 2H), 7.85—7.70 (m, 4H). C NMR
(
1
2
100 MHz, DMSO-d ) δ: 148.9, 146.2, 139.6, 133.5, 132.3, 130.4,
6
28.9, 128.8, 128.2, 128.1, 126.8, 124.6, 121.7. HRMS: m/z
2
+
2+
05.0890 ([C30
H
22
N
2
] , calcd. for [C30
H
22
N
2
] , 205.0886).
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.201800562.
Acknowledgement
This work was supported by the National Natural Science
Foundation of China (Nos. 21771145 and 21472149).
5
0, 14105–14108.
References
[
14] (a) Whang, D.; Kim, K. Polycatenated Two-Dimensional Polyrotaxane
[
1] Zhu, Z.; Fahrenbach, A. C.; Li, H.; Barnes, J. C.; Liu, Z.; Dyar, S. M.;
Net. J. Am. Chem. Soc. 1997, 119, 451–452; (b) Lee, E.; Kim, J.; Heo, J.;
274 www.cjc.wiley-vch.de
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2019, 37, 269－275

A Precise Definition of Rotaxane
Chin. J. Chem.
Whang, D.; Kim, K. A Two-Dimensional Polyrotaxane with Large Cavi-
ties and Channels: A Novel Approach to Metal-Organic Open-
Frameworks by Using Supramolecular Building Blocks. Angew. Chem.
Int. Ed. 2001, 40, 399–402.
Regulated Molecular Trafficking in a Synthetic Water-Soluble Host. J.
Am. Chem. Soc. 2016, 178, 5745–5748; (f) Liu, Y.; Yu, Y.; Gao, J.;
Wang, Z.; Zhang, X. Water-Soluble Supramolecular Polymerization
Driven by Multiple Host-Stabilized Charge-Transfer Interactions. An-
gew. Chem. Int. Ed. 2010, 49, 6576–6579.
[
15] (a) Samanta, S. K.; Brady, K. G.; Isaacs, L. Self-Assembly of Cucur-
bit[7]uril Based Triangular [4]molecular Necklaces and Their Fluo-
rescence Properties. Chem. Commun. 2017, 53, 2756–2759; (b)
Whang, D.; Park, K.-M.; Heo, J.; Ashton, P.; Kim, K. Molecular Neck-
lace: Quantitative Self-Assembly of a Cyclic Oligorotaxane from Nine
Molecules. J. Am. Chem. Soc. 1998, 120, 4899–4900; (c) Li, J.; Yu, Y.;
Luo, L.; Li, Y.; Wang, P.; Cao, L.; Wu, B. Square [5]molecular Necklace
Formed from Cucurbit[8]uril and Carbazole Derivative. Tetrahedron
Lett. 2016, 57, 2306–2310.
[21] Wu, G.; Olesinska, M.; Wu, Y.; Matak-Vinkovic, D.; Scherman, O. A.
Mining 2:2 Complexes from 1:1 Stoichiometry: Formation of Cucur-
bit*8+uril−Diarylviologen Quaternary Complexes Favored by Electron-
Donating Substituents. J. Am. Chem. Soc. 2017, 139, 3202–3208.
[22] Yu, Y.; Li, Y.; Wang, X.; Nian, H.; Wang, L.; Li, J.; Zhao, Y.; Yang, X.; Liu,
S.; Cao, L. Cucurbit[10]uril-Based [2]Rotaxane: Preparation and Su-
pramolecular Assembly-Induced Fluorescence Enhancement. J. Org.
Chem. 2017, 82, 5590–5596.
[
16] (a) Lee, E.; Heo, J.; Kim, K. A Three-Dimensional Polyrotaxane Net-
work. Angew. Chem. Int. Ed. 2000, 39, 2699–2701; (b) Fan, Z.-F.; Xiao,
X.; Zhang, Y.-Q.; Xue, S.-F.; Zhu, Q.-J.; Tao, Z.; Wei, G. A Three Dimen-
sional Framework Induced by π-π Stacking of 2,2'-(Alkylene-1,6-
diyl)diisoquinolinium from Q[6]-Based Pseudorotaxane. J. Incl. Phe-
nom. Macrocycl. Chem. 2011, 71, 577–581; (c) Sun, X.; Li, B.; Cao, J.;
Chen, J.; Wang, N.; Wan, D.; Zhang, H.; Zhou, X. Pseudopolyrotaxanes
[23] Barrow, S. J.; Kasera, S.; Rowland, M. J.; Barrio, J. D.; Scherman, O. A.
Cucurbituril-Based Molecular Recognition. Chem. Rev. 2015, 115,
12320–12406.
[24] Hong, Y.; Lam, J. W. Y.; Tang, B. Aggregation-induced Emission. Chem.
Soc. Rev. 2011, 40, 5361–5388.
[25] Mukhopadhyay, P.; Wu, A.; Isaacs, L. Social Self-Sorting in Aqueous
Solution. J. Org. Chem. 2004, 69, 6157–6164.
of Cucurbit[6]uril: A Three-Dimensional Network Self-assembled by
[26] Shigemitsu, H.; Fujisaku, T.; Tanaka, W.; Kubota, R.; Minami, S.;
Hamachi, K.; Hamachi, I. An Adaptive Supramolecular Hydrogel
Comprising Self-Sorting Double Nanofibre Networks. Nat. Nanotech.
2018, 13, 165–172.
[27] Huang, Z.; Qin, B.; Chen, L.; Xu, J.-F.; Faul, C. F. J.; Zhang, X. Supra-
molecular Polymerization from Controllable Fabrication to Living
Polymerization. Macromol. Rapid Commun. 2017, 38, 1700312.
[28] Pfeffermann, M.; Dong, R.; Graf, R.; Zajaczkowski, W.; Gorelik, T.; Pi-
sula, W.; Narita, A.; Mꢀllen, K.; Feng, X. Free-Standing Monolayer
Two-Dimensional Supramolecular Organic Framework with Good In-
ternal Order. J. Am. Chem. Soc. 2015, 137, 14525–14532.
[29] Vieira, V. M. P.; Lima, A. C.; Jong, M. D.; Smith, D. K. Commercially
Relevant Orthogonal Multi-Component Supramolecular Hydrogels
for Programmed Cell Growth. Chem. Eur. J. 2018, 24, 15112–15118.
[30] Shang, X.; Song, I., Jung, G. Y.; Choi, W.; Ohtsu, H.; Lee, J. H.; Koo, J. Y.;
Liu, B.; Ahn, J.; Kawano, M.; Kwak, S. K.; Oh, J. H. Chiral Self-Sorted
Multifunctional Supramolecular Biocoordination Polymers and Their
Applications in Sensors. Nat. Commun. 2018, 9, 3933.
-
ClO
4
(H
2
O)
2
Water Clusters. Chin. J. Chem. 2012, 30, 941–946; (d)
Zhang, C.-C.; Zhang, Y.-M.; Liu, Y. Photocontrolled Reversible Conver-
sion of a Lamellar Supramolecular Assembly Based on Cucurbiturils
and a Naphthalenediimide Derivative. Chem. Commun. 2018, 54,
13591–13594.
[
[
17] Chen, X.-M.; Chen, Y.; Yu, Q.; Gu, B.-H.; Liu, Y. Supramolecular As-
semblies with Near-Infrared Emission Mediated in Two Stages by
Cucurbituril and Amphiphilic Calixarene for Lysosome-Targeted Cell
Imaging. Angew. Chem. Int. Ed. 2018, 57, 12519–12523.
18] (a) Zhang, K.-D.; Tian, J.; Hanifi, D.; Zhang, Y.; Sue, A. C.-H.; Zhou, T.-Y.;
Zhang, L.; Zhao, X.; Liu, Y.; Li, Z.-T. Toward a Single-Layer Two-Di-
mensional Honeycomb Supramolecular Organic Framework in Water.
J. Am. Chem. Soc. 2013, 135, 17913–17918; (b) Li, Y.; Dong, Y.; Miao,
X.; Ren, Y.; Zhang, B.; Wang, P.; Yu, Y.; Li, B.; Isaacs, L.; Cao, L.
Shape-Controllable and Fluorescent Supramolecular Organic Frame-
works Through Aqueous Host–Guest Complexation. Angew. Chem.
Int. Ed. 2018, 57, 729–733.
[
[
19] Li, S.-H.; Xu, X.; Zhou, Y.; Zhao, Q.; Liu, Y. Reversibly Tunable White-
Light Emissions of Styrylpyridiniums with Cucurbiturils in Aqueous
Solution. Org. Lett. 2017, 19, 6650–6653.
20] (a) Kotturi, K.; Masson, E. Directional Self-Sorting with Cucurbit[8]uril
Controlled by Allosteric π-π and Metal–Metal Interactions. Chem. Eur.
J. 2018, 24, 8670–8678; (b) Liu, Y.; Yang, H.; Wang, Z.; Zhang, X. Cu-
curbit[8]uril-Based Supramolecular Polymers. Chem. Asian J. 2013, 8,
[31] Ganapati, S.; Isaacs, L. Acyclic Cucurbit[n]uril-Type Receptors: Prepa-
ration, Molecular Recognition Properties and Biological Applications.
Isr. J. Chem. 2018, 58, 250–263.
[32] Kim, J.; Jung, I.-S.; Kim, S.-Y.; Lee, E.; Kang, J.-K.; Sakamoto, S.; Ya-
maguchi, K.; Kim, K. New Cucurbituril Homologues: Syntheses, Isola-
tion, Characterization, and X-ray Crystal Structures of Cucurbit[n]uril
(n = 5, 7, and 8). J. Am. Chem. Soc. 2000, 122, 540–541.
1626–1632; (c) Chakrabarti, S.; Isaacs, L. Cucurbit[8]uril Controls the
Folding of Cationic Diaryl Ureas in Water. Supramol. Chem. 2008, 20,
1
91–199; (d) Ko, Y. H.; Kim, K.; Kim, E.; Kim, K. Exclusive Formation of
Manuscript received: December 12, 2018
Manuscript revised: January 9, 2019
1:1 and 2:2 Complexes between Cucurbit[8]uril and Electron Donor-
Acceptor Molecules Induced by Host-stabilized Charge-transfer In-
teractions. Supramol. Chem. 2007, 19, 287–293; (e) Barrio, J. D.;
Ryan, S. T. J.; Jambrina, P. G.; Rosta, E.; Scherman, O. A. Light-
Manuscript accepted: January 11, 2019
Accepted manuscript online: January 24, 2019
Version of record online: February 6, 2019
Chin. J. Chem. 2019, 37, 269－275
© 2019 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
275