Ring-in-ring(s) complexes exhibiting tunable multicolor photoluminescence

Article abstract of DOI:10.1021/jacs.0c07745

One ring threaded by two other rings to form a non-intertwined ternary ring-in-rings motif is a challenging task in noncovalent synthesis. Constructing multicolor photoluminescence systems with tunable properties is also a fundamental research goal, which

Full text of DOI:10.1021/jacs.0c07745

Subscriber access provided by EDINBURGH UNIVERSITY LIBRARY | @ http://www.lib.ed.ac.uk
Article
Ring-in-Ring(s) Complexes Exhibiting
Tunable Multicolor Photoluminescence
Huang Wu, Yu Wang, Leighton O. Jones, Wenqi Liu, Bo Song, Yunpeng
Cui, Kang Cai, Long Zhang, Dengke Shen, Xiao-Yang Chen, Yang Jiao,
Charlotte L. Stern, Xiaopeng Li, George C. Schatz, and J. Fraser Stoddart
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.0c07745 • Publication Date (Web): 04 Sep 2020
Downloaded from pubs.acs.org on September 4, 2020
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the
course of their duties.

Page 1 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Ring-in-Ring(s) Complexes Exhibiting Tunable
Multicolor Photoluminescence
Huang Wu,† Yu Wang,† Leighton O. Jones,† Wenqi Liu,† Bo Song,† Yunpeng Cui,‡ Kang Cai,†
Long Zhang,† Dengke Shen,† Xiao-Yang Chen,† Yang Jiao,† Charlotte L. Stern,† Xiaopeng Li,⊥
George C. Schatz† and J. Fraser Stoddart*,†,∇,§
†Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208,
United States
‡Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States
∇School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
§Institute for Molecular Design and Synthesis, Tianjin University, 92 Weijin Road, Nankai District,
Tianjin 300072, P.R. China
⊥ College of Chemistry and Environmental Engineering, Shenzhen University, 3688 Nanhai Ave,
Shenzhen, Guangdong 518055, P.R. China
* E-mail: stoddart@northwestern.edu
MAIN TEXT
*Correspondence Address
Professor J Fraser Stoddart
Department of Chemistry
Northwestern University
2145 Sheridan Road
Evanston, IL 60208-3113 (USA)
Tel: (+1)-847-491-3793
E-Mail: stoddart@northwestern.edu
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 2 of 31
1
2
3
4
5
6
7
8
9
ABSTRACT: One ring threaded by two other rings to form a non-intertwined ternary ring-in-
rings motif is a challenging task in noncovalent synthesis. Constructing multicolor
photoluminescence systems with tunable properties is also a fundamental research goal, which
can lead to applications in multidimensional biological imaging, visual displays, and encryption
materials. Herein, we describe the design and synthesis of binary and ternary ring-in-ring(s)
complexes, based on an extended tetracationic cyclophane and cucurbit[8]uril. The formation
of these complexes is accompanied by tunable multicolor-fluorescence outputs. On mixing
equimolar amounts of the cyclophane and cucurbit[8]uril, a 1:1 ring-in-ring complex is formed
as a result of hydrophobic interactions associated with a favorable change in entropy. With the
addition of another equivalent of cucurbit[8]uril, a 1:2 ring-in-rings complex is formed,
facilitated by additional iondipole interactions involving the pyridinium units in the
cyclophane and the carbonyl groups in cucurbit[8]uril. Because of the narrowing in the energy
gaps of the cyclophane within the rigid hydrophobic cavities of cucurbit[8]urils, the binary and
ternary ring-in-ring(s) complexes emit green and bright yellow fluorescence, respectively. A
series of color-tunable emissions, such as skyblue, cyan, green, and yellow with increased
fluorescence lifetimes, can be achieved by simply adding cucurbit[8]uril to an aqueous solution
of the cyclophane. Notably, the smaller cyclobis(paraquat-p-phenylene), which contains the
same p-xylylene linkers as the extended tetracationic cyclophane, does not form ring-in-ring(s)
complexes with cucurbit[8]uril. The encapsulation of this extended tetracationic cyclophane by
both one and two cucurbit[8]urils provides an incentive to design and synthesize more advanced
supramolecular systems, as well as opening up a feasible approach toward achieving tunable
multicolor photoluminescence with a single chromophore.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
■
INTRODUCTION
Ever since Charles Pedersen1 reported the discovery of the crown ethers and their complexes
with Group IA and IIA metal cations in 1967, the investigation2 of macrocyclic hosts and their
recognition properties has skyrocketed. Relying on multiple noncovalent bonding interactions,
many intensively investigated macrocyclic hosts exhibit highly specific recognition for
different guests, forming a diverse array of molecular recognition motifs.3 Among these
recognition motifs, non-intertwined ring-in-ring motifs are not only a feasible goal but also an
essential one,4 since they are promising precursors for assembling Russian doll-like
superstructures,5 molecular Borromean rings,6 and neotype rotaxanes.7 One ring threaded by
two or more rings to form a non-intertwined ring-in-rings motif, however, is still rare.
Historically, endowing hostguest complexes with optical properties has often been a
2
ACS Paragon Plus Environment

Page 3 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
worthwhile goal for supramolecular chemists. Fluorescent molecules with tunable emission
colors have attracted an increasing amount of attention8 because of their potential applications
in multidimensional bioimaging,9 encryption materials,10 and visual displays.11 Conventional
methods of controlling the emission of fluorescent molecules involve mainly covalent
modification.12 In contrast to conventional approaches, a noncovalent strategy has recently
proven to be an efficient way to fabricate smart optical materials, in which fluorescent
molecules display distinctive photophysical properties when participating in hostguest
complexation.13 Constructing luminescent host-guest complexes, which integrate the features
of wavelength tunability, water solubility, and applicability to a wide concentration range, is an
attractive research objective.14
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The rigid tetracationic cyclophane, cyclobis(paraquat-p-phenylene)15 (CBPQT4+), which is
composed of two π-electron-deficient bipyridinium (BIPY2+) units connected by p-xylylene
linkers, has an centroid-to-centroid width of 6.8 Å. The well-defined inner cavity enables the
cyclophane to encapsulate π-electron-rich guests, e.g., 1,5-dioxynaphthalene units,16 and
tetrathiafulvalene derivatives.17 By taking advantage of these host–guest interactions,
CBPQT4+ serves as an ideal building block for constructing mechanically interlocked
molecules18 (MIMs). In order to modulate the size of the cavity in CBPQT4+, a series of
extended cationic cyclophanes have been designed and synthesized. These extended
cyclophanes exhibit a high bonding affinity for planar aromatic guests as a result of the electron-
deficient nature of their extended19 BIPY2+ units. Although most attention previously has been
focused20 on their properties as hosts, we have recently expanded their roles from being hosts
to being guests with the intention of exploring new recognition motifs. For example, the square-
shaped diradical cyclophane [cyclobis(paraquat-4,4′-biphenylene)]2(+•) can encapsulate
selectively a [cyclobis(paraquat-m-phenylene)]2(+•) in its cavity to form a tetraradical
tetracationic host–guest complex.21 Upon lengthening the centroid-to-centroid distance
between the two BIPY2+ units in the outer cyclophane to 13.1 Å, it can form22 a box-in-box
complex with CBPQT4+ in their two-electron reduced states. This complex is able to
accommodate small aromatic guest molecules inside the void of CBPQT2(+•), forming Russian
doll-like assemblies. These two box-in-box superstructures, however, can only survive in an
inert atmosphere, because of the instability of the BIPY+• radical under ambient conditions.
On the other hand, cucurbit[n]uril23 (CB[n]), benefiting from their well-defined electron
negative carbonyl portals and hydrophobic cavities, show high binding affinities for methyl
viologen dications and its derivatives,24 including25 the tetracationic cyclophane CBPQT4+ in
aqueous solutions. Cucurbit[8]uril (CB[8]), with a portal diameter26 of 9.9 Å, is a relatively
3
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 4 of 31
1
2
3
4
5
6
7
8
9
large homologue within the CB[n] family. It can (i) bind simultaneously electron-accepting and
electron-donating guests in its cavity,27 or (ii) accommodate two identical guests, e.g.,
naphthalene28, arylpyridinium,29 and others,30 inside its cavity resulting in compact [π···π]
stacking. The tetracationic cyclophane CBPQT4+, however, is not encapsulated by CB[8]
forming a ring-in-ring complex, on account of the rigid conformation of CBPQT4+ and the
limited space inside the cavity of CB[8].25 In this investigation, we found that (Scheme 1), when
installing the oligo(p-phenylenevinylene) bipyridinium (OPV2+) units in an extended
tetracationic cyclophane, OPVEBox4+, CB[8] is able to bind to the outside of this cyclophane,
forming ring-in-ring(s) complexes. The binary and ternary ring-in-ring(s) complexes,
corresponding to 1:1 and 1:2 stoichiometries between OPVEBox4+and CB[8], can be easily
obtained, as confirmed by NMR spectroscopy and electrospray ionization-mass spectrometry
(ESI-MS). The formation of the binary OPVEBox4+CB[8] and ternary OPVEBox4+2CB[8]
ring-in-ring(s) complexes are sustained, for the most part, by hydrophobic and iondipole
interactions. Moreover, on account of the specific electronic distributions of OPVEBox4+ inside
the rigid hydrophobic cavity of CB[8], the binary and ternary ring-in-ring(s) complexes display
green and bright yellow fluorescence, respectively. They are red shifted significantly compared
with the skyblue fluorescence of free OPVEBox4+. Fluorescence spectroscopy and visual
images reveal a variety of fluorescence colors, e.g., skyblue, cyan, green, and yellow with
increased fluorescence lifetimes, which can be reversibly obtained by adding different
equivalents of CB[8] to an aqueous solution of OPVEBox•4Cl, and following with the addition
of competitive guest.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
■
RESULTS AND DISCUSSION
Synthesis of OPVEBox4+
OPVEBox4+ was prepared (Scheme S1) in three steps as shown in the Supporting Information.
The key building block, 1,4-BPEB, was synthesized in 60% yield from a Knoevenagel
condensation between terephthalaldehyde and 4-picoline in acetic anhydride solution.
Subsequently, 1,4-BPEB was added dropwise into a MeCN solution of an excess of p-xylylene
dibromide under refluxing conditions, leading to the formation of BrOPV•2PF6 after
counterion exchange (NH4PF6 / H2O) in a yield of 82%. Finally, a mixture of equimolar
amounts of BrOPV•2PF6 and 1,4-BPEB, as well as 0.2 equiv tetrabutylammonium iodide
(TBAI), was heated under refluxing in MeCN for 3 days. A crude product was obtained after
precipitating with tetrabutylammonium chloride (TBACl). The desired product OPVEBox4+

was obtained as its PF6 salt in 40% yield following reverse-phase column chromatography and
4
ACS Paragon Plus Environment

Page 5 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
counterion exchange (NH4PF6 / H2O). The water-soluble counterpart, namely OPVEBox•4Cl,
was then obtained from OPVEBox•4PF6 by counterion exchange (TBACl / MeCN).
Characterization of OPVEBox4+
9
OPVEBox•4Cl was fully characterized by one dimensional (Figures S3 and S4) and two
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
13
dimensional (2D) (Figures S7S10) H and C NMR spectroscopies, as well as by ESI-MS
(Figure S21), which revealed the presence of [M – 2Cl]2+ and [M – 4Cl]4+ ions with m/z values
of 423.16 and 194.10, respectively. The UV-Vis absorption spectrum (Figure S26) of
OPVEBox•4Cl shows a strong absorption peak at 392 nm, and its aqueous solution exhibits
(Figure S33) skyblue fluorescence with a maximum emission wavelength at 482 nm. When
changing the concentration of OPVEBox4+ from 0.1 to 10.0 M, the intensity of the
fluorescence increases (Figure S34) more or less linearly with concentration. The intensity,
however, shows a downward trend upon changing the concentration from 10.0 to 80.0 M.
These observations indicate that there is no obvious aggregation-induced fluorescence
quenching on the part of OPVEBox4+ at concentrations lower than 10.0 M. The cyclic
voltammogram (CV) of OPVEBox4+ exhibits (Figure S25) only one set of reversible redox
peaks in degassed DMF, indicating the absence of electronic communications between the
pyridinium units within the extended tetracationic cyclophane.
A yellow single crystal of OPVEBox•4Cl was obtained by slow vapor diffusion of Me2CO into
an aqueous solution of OPVEBox•4Cl during the course of one week. Its solid-state structure
reveals (Figure 1a) a box-like geometry, with average dimensions (Figure 1b) of 18.7  7.6 Å.
The centroid-to-centroid distance (7.6 Å) between two OPV2+ units is larger than that15a (6.8
Å) in CBPQT4+. The distance between the two nitrogen atoms in the OPV2+ unit is (Figure 1c)
15.9 Å, a value which is more than twice the width26 (6.1 Å) of CB[8]. The solid-state
superstructure (Figure 1) of OPVEBox•4Cl reveals that it crystallizes in a monoclinic space
group P21/c. Every OPVEBox4+ molecule interacts (Figure 1d) with 16 Cl− anions. The
[CHCl] hydrogen bonding distances range from 2.6 to 2.9 Å. Accordingly, OPVEBox4+ and
Cl− anions adopt an alternating arrangement to form (Figure 1e) a well-ordered array that
constitutes the solid-state superstructure. By contrast, the OPVEBox•4PF6 superstructure
reveals (Figure S24) that the OPVEBox4+ molecules crystallize in a herringbone fashion,
stabilized by [ππ] stacking between pairs of OPV2+ units, as well as there being [ππ]
interaction between these OPV2+ units and the p-phenylene rings in adjacent cyclophane
molecules, with plane-to-plane distances of 2.7 and 3.9 Å, respectively. This observation
5
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 6 of 31
1
2
3
4
5
6
indicates that merely changing counterions provides a way of modulating solid-state
superstructures.
7
8
Formation of Diverse Ring-in-Ring(s) Complexes
9
Upon adding an excess of CB[8] to an aqueous solution of OPVEBox•4Cl, we found, quite
accidentally, that the fluorescence of the solution changed from skyblue to yellow, indicating
the occurrence of noncovalent bonding interactions between CB[8] and OPVEBox4+. Inspired
by this observation, 1H NMR spectroscopy and MS analyses were carried out in order to gain
further insight into the nature of these interactions. Upon adding an equimolar amount of CB[8]
to a D2O solution of OPVEBox•4Cl, the chemical shifts for protons in both the OPVEBox4+
and CB[8] all show (Figures 2d and S11) marked changes in the 1H NMR spectrum, indicating
the formation of a hostguest complex. The peaks in the spectrum were assigned on the basis
of in-depth analyses of their 2D 1H−1H COSY (Figure S12) and ROESY (Figure S13) spectra.
The chemical shifts of H-7, residing on the central phenylene groups, as well as H-5 and H-6,
attached to the C C double bonds, show (Figure 2d) large upfield shifts (Δδ = 0.64, 0.43
and 1.12 for H-5, H-6, and H-7, respectively). While the protons on CB[8] display (Figure S11)
small upfield shifts (Δδ = 0.09, 0.11 and 0.13 for H-a, H-b, and H-c, respectively). These
results indicate that CB[8] is bound in the middle of OPVEBox4+, forming a 1:1 ring-in-ring
complex. In the 1H NMR spectrum (Figure 2b) of an equimolar mixture of CBPQT4+ and CB[8],
the chemical shift of H-4 shows no change, while protons associated with the p-xylylene linkers
in CBPQT4+ exhibit small upfield shifts (Δδ = 0.10 and 0.13 for H-1 and H-2, respectively).
Hence, CB[8] may bind very weakly to the p-xylylene linkers, instead of forming ring-in-ring
complex with CBPQT4+, a result which is consistent with a previous report.25 Taken together,
it can be concluded that, although OPVEBox4+ and CBPQT4+ have the same p-xylylene linkers,
only OPVEBox4+ can form ring-in-ring(s) complexes with CB[8] in aqueous solutions. A
possible reasons for this observation is that the long OPV2+ building blocks in OPVEBox4+ is
much more flexible than the BIPY2+ units in CBPQT4+.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Upon the addition of another 1 equiv of CB[8] to a D2O solution of OPVEBox•4ClCB[8], a
1
new set of resonances, accompanied by severely broadened, appeared (Figure 2e) in the H
NMR spectrum. On analysis of the 2D 1H−1H COSY (Figure S15) and ROESY (Figure S16)
spectra, all the peaks in the spectra could be assigned. Diagnostic changes in chemical shifts,
on comparing (Figure S14) with the 1H NMR spectra of free OPVEBox4+and CB[8], indicate
the formation of a 1:2 ternary ring-in-rings complex, OPVEBox4+2CB[8]. All the protons
residing on the pyridinium units and C C double bonds display (Figure 2e) large upfield shifts
6
ACS Paragon Plus Environment

Page 7 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
(Δδ = 0.61, 1.20, 0.75 and 0.81 for H-3, H-4, H-5, and H-6, respectively), while the
chemical shift of H-7 does not change. The methylene protons (H-a and H-b) on CB[8] were
separated (Figure S14) into two sets of peaks (δ = 5.96 / 5.82 and 4.36 / 4.22 for H-a and H-b,
respectively), indicating that the centrosymmetric geometry of CB[8] molecules has been
broken. All these results reveal that two CB[8] molecules are bound to the pairs of pyridinium
units and C C double bonds at both ends of the extended cyclophane in the ternary
OPVEBox4+2CB[8] ring-in-rings complex. On continuing to add CB[8] into the D2O solution
of OPVEBox•4Cl2CB[8], the chemical shifts of both host and guest protons showed (Figure
S18) no appreciable changes. This observation suggests that the 1:2 complex is
thermodynamically stable, despite the presence of an excess of CB[8]. 2D Diffusion-ordered
NMR spectroscopy (DOSY) confirmed the formation of the binary and ternary ring-in-ring(s)
complexes. The spectra of OPVEBox4+ (Figure S17), OPVEBox4+CB[8] (Figure 3a), and
OPVEBox4+2CB[8] (Figure 3b) display narrow signal bands with diffusion coefficients of
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
3.94×10−6, 3.31×10−6, and 3.01×10−6 cm2/s, respectively. Furthermore, H NMR titrations
revealed (Figure S18) that the association and disassociation of both OPVEBox4+CB[8] and
OPVEBox4+2CB[8] complexes undergo slow exchange on the 1H NMR time scale.
In addition, ESI-MS provided strong evidence for the formation of these two ring-in-ring(s)
superstructures. In the ESI-MS of an equimolar mixture of OPVEBox•4Cl and CB[8], only one
peak (m/z = 526.20) is present (Figure 3c), corresponding to the 1:1 complex with four positive
charges, namely, [OPVEBox4+CB[8]]4+. Upon further addition of CB[8] to the solution of
OPVEBox4+CB[8], a series of new peaks appears (Figure 3d) in the ESI-MS, as a result of
the formation of the 1:2 OPVEBox4+2CB[8] ring-in-rings complex, accompanied by the
additions of differing numbers of Na+ ions. The isotopic patterns (Figure 3d and S23) with four,
five, and six positive charges at m/z = 858.29 ([OPVEBox4+2CB[8]4+), 691.23
([OPVEBox4+2CB[8]+Na+]5+), and 579.86 ([OPVEBox4+2CB[8]+2Na+]6+), respectively,
match well with their theoretical values, strongly supporting the formation of the ternary ring-
in-rings complex. Based on the NMR spectroscopic and ESI-MS experiments, it is can be
concluded that two kinds of new ring-in-ring(s) complexes can be assembled by simply mixing
the tetracationic cyclophane OPVEBox4+ with 1 or 2 equiv of CB[8] in aqueous solution.
DFT Calculations
In order to gain a better understanding of the superstructures and electronic properties of both
the binary OPVEBox4+CB[8] and ternary OPVEBox4+2CB[8] ring-in-ring(s) complexes,
density functional theory (DFT) calculations were performed. The optimized superstructure of
7
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 8 of 31
1
2
3
4
5
6
OPVEBox4+CB[8] was determined to be (Figures 4 and S43) such that the central phenylene
groups and C C double bonds are included inside the cavity of CB[8], in accordance with the
1
results obtained from H NMR spectroscopy. The OPVEBox4+ no longer adopts a box-like
7
8
9
conformation in the optimized superstructure (Figure 4c) of OPVEBox4+CB[8], wherein the
OPV2+ units are compelled to bend into the cavity of the cyclophane with the centroid-to-
centroid distance being reduced to 3.9 Å, on account of the tight encapsulation by the CB[8]
ring. The strain energy (Table S5) for the compressed OPVEBox4+ in this ring-in-ring complex
is 28.6 kcal/mol according to DFT calculations. In the case of OPVEBox4+2CB[8] complex,
two CB[8] are bound (Figures 4 and S44) to the two sides of OPVEBox4+, which is also in
agreement with the 1H NMR spectroscopic results. As a consequence of the compression by the
two CB[8] rings, the entire OPVEBox4+ is squeezed, and its strain energy is (Table S5) 42.9
kcal/mol, a value which is higher than that (28.6 kcal/mol) present in the binary ring-in-ring
complex. The p-xylylene linkers are forced to bend, with the distance (Figure 4g) between their
two peripheral nitrogen atoms of 5.3 Å. Meanwhile, the CB[8] rings assume (Figures 4d and
4h) an ellipsoidal deformation in order to form the ring-in-ring(s) complexes, reminiscent of
the induced fit of enzymes with respect to the substrates in biological systems.31 According to
the electrostatic potential analysis, after complexing with one and two CB[8] rings, the
electronic cloud density in the original electron deficient OPVEBox4+ cyclophane increases
gradually (Figures 4ik) as a result of intermolecular charge transfer.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
UV-Vis Absorption Spectroscopy
The changes in the absorption spectra induced by the formation of the ring-in-ring(s) complexes
afforded us an easy way to track molecular recognition processes. In a UV-Vis titration (Figure
5a), the absorbance at 415 nm increases (Figure 5b) gradually with the stepwise addition of 1
equiv of CB[8] to an aqueous solution of OPVEBox•4Cl. On the contrary, the absorbance
shows a downward trend when continuing to add another 4 equiv of CB[8]. These observations
indicate there is a two-stage binding process happening during titration of OPVEBox4+ with
CB[8]. In the first stage of the stepwise addition of 1 equiv of CB[8] to an aqueous solution of
OPVEBox•4Cl, the absorption peak of OPVEBox4+, centered on 392 nm, decreases (Figures
S28 and S29) gradually with a red shift of 21 nm. Also, two clear isosbestic points appear
(Figure 5a) at 282 and 407 nm in the UV-Vis spectra. These observations reflect the formation
of the binary OPVEBox4+CB[8] ring-in-ring complex. In the second stage, upon the further
addition of 4 equiv of CB[8], the absorption peak intensity of OPVEBox4+CB[8], centered
on 413 nm, continues to decrease (Figure S28). The peak is red shifted to 430 nm (Figure S29),
8
ACS Paragon Plus Environment

Page 9 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
accompanied by the appearance (Figure 5a) of a new isobestic point at 426 nm. These changes
are a result of the transformation from the binary OPVEBox4+CB[8] to the ternary
OPVEBox4+2CB[8] complexes. A Job plot shows (Figure S27) a maximum at a molar
fraction of 0.33, confirming the 1:2 stoichiometry between OPVEBox4+ and CB[8].
Frontier molecular orbital calculations reveal the origin of the changes in photophysical
properties upon the formation of these two complexes. The frontier molecular orbital diagrams
show (Figures S49 and S50) that both the HOMOs and LUMOs of the ring-in-ring(s) complexes
are localized predominantly on OPVEBox4+. The HOMOLUMO energy gaps (Table S3) for
the OPVEBox4+, OPVEBox4+CB[8] and OPVEBox4+2CB[8] are 2.79, 2.61 and 2.55 eV,
respectively, which become narrower upon binding one and then two CB[8] molecules. These
gradually narrowing energy gaps are consistent with the red shift in the absorption spectra upon
the encapsulation of OPVEBox4+ by CB[8].
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Binding Thermodynamics
The binding constants for the formation of the binary and ternary ring-in-ring(s) complexes can
be obtained from the UV-Vis titration spectroscopy and isothermal titration calorimetry (ITC).
The absorption band in the range from 450 to 460 nm increases (Figure S30) upon formation
of the binary complex, while it shows almost no change during the formation of the ternary
complex. Accordingly, the first-stage binding constant (K1) for the formation of the binary
OPVEBox4+CB[8] complex has been determined (Figure S31) to be 5.8 × 107 M−1, based on
the change in absorbance at 455 nm upon titrating OPVEBox4+ with CB[8]. Although it is
difficult to evaluate the K1 using ITC, because of the low solubility of CB[8] in H2O, the change
of enthalpy (ΔH) was estimated (Figure S40) to be 2.0 kcal/mol from the isotherm of a single
injection experiment.32 The Gibbs free energy (ΔG) was determined (Table 1) from the UV-Vis
titration carried out at 25 ℃, and then the value of TΔS was calculated to be 8.6 kcal/mol. It
follows that the formation of the OPVEBox4+CB[8] complex in aqueous solution is driven
mainly by a favorable entropy change with a small contribution from the change of enthalpy,
indicating that this binding process is dominated by hydrophobic effect. When the binary
OPVEBox4+CB[8] complex is converted into the ternary OPVEBox4+2CB[8] complex
during the second binding event, a new absorption peak appears (Figure S30) at approximately
480 nm in the UV-Vis absorption spectra. Consequently, the second-stage binding constant (K2)
was calculated (Figure S32) to be 1.8 ×105 M−1 by following the change in absorbance at 495
nm. The complex of OPVEBox4+CB[8] has a high water solubility, allowing us to perform
ITC experiment for the second-stage binding by titrating OPVEBox4+CB[8] complex into a
9
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 10 of 31
1
2
3
4
5
6
7
8
9
dilute aqueous solution of CB[8]. A value of K2 was determined (Figure S39) to be 1.5 × 105
M−1, which is matched well with that (1.8 × 105 M−1) estimated from the UV-Vis titration. The
change of enthalpy (ΔH) was determined to be 11.8 kcal/mol and the TΔS was calculated to
be 4.7 kcal/mol for the second stage binding event, indicating that the formation of the
OPVEBox4+2CB[8] complex is enthalpically driven. It is clear that the formation of the 1:2
complex involves a more favorable binding enthalpy (11.8 kcal/mol) than that (2.0 kcal/mol)
associated with the formation of the 1:1 complex. This difference might be a result of multiple
[N···OC] ion−dipole interactions in the 1:2 complex, while the [N···OC] ion−dipole
interactions are negligible when CB[8] is located in the middle of OPVEBox4+ in the case of
the 1:1 complex.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Multicolor Fluorescent Outputs
During the formation of the binary OPVEBox4+CB[8] and ternary OPVEBox4+2CB[8]
ring-in-ring(s) complexes, tunable fluorescent emissions ranging from skyblue to bright yellow
are observed. Upon adding an equimolar amount of CB[8] to a 2 M aqueous solution of
OPVEBox•4Cl, the fluorescence intensity of OPVEBox4+ decreases (Figure 6a) and the
maximum emission wavelength is red shifted (Figure S35) from 482 to 533 nm, as a result of
the formation of the 1:1 complex. The fluorescence quantum yield of OPVEBox4+CB[8] is
measured (Table S1) to be 2.4%, a value which is the same as that (2.4%) for the free
OPVEBox4+. By contrast, when continuing to add 1 equiv of CB[8] to the solution of 1:1
complex, the fluorescence intensity increases (Figure 6a) and the maximum emission
wavelength shifts to 575 nm, which is red shifted by 93 nm compared with that (482 nm) of
free OPVEBox4+. The fluorescence quantum yield reaches (Table S1) 8.1%, on account of the
formation of the OPVEBox4+2CB[8] complex. With increasing concentration of CB[8] from
2 to 5 equiv, the fluorescence intensity of the resulting solution shows (Figure 6a) an upward
trend, although the peaks are no longer red shifted (Figure S35), and a higher fluorescence
quantum yield of 18.6% is obtained (Table S1). These results are attributable to the larger
proportion of the ternary OPVEBox4+2CB[8] complex in the resulting aqueous solution with
increasing concentration of CB[8]. Upon complexing with 1 and 2 equiv CB[8], the average
fluorescence lifetimes (Table S2) of OPVEBox4+ increases from 0.3 ns to 6.0 and 12.0 ns,
respectively, indicating that CB[8] is able to stabilize the excited states of OPVEBox4+. In a
higher-concentration solution of OPVEBox4+ (10 M) and CB[8] (50 M), the fluorescence
quantum yield (Table S1) reaches 30.0%, and the proportion of the long fluorescence-lifetimes
(12.0 ns) species, arising from the OPVEBox4+2CB[8] complex, is 95%. These observations
10
ACS Paragon Plus Environment

Page 11 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
may be the result of the association and dissociation equilibrium shifting to produce larger
amounts of the ternary complex at higher concentration according to Le Chatelier's principles.33
The higher fluorescence quantum yields maybe benefit from the fact that CB[8] molecules
restrict the free pedal motion about the C C double bonds within OPVEBox4+. Both binary
and ternary ring-in-ring(s) complexes exhibit (Figure S37) bright fluorescence even at
concentrations of 0.1 mM in aqueous solutions, an observation which demonstrates that the
photoluminescence properties of the ring-in-ring(s) complexes persist over a wide range of
concentrations. In addition, upon the stepwise addition of CB[8] to an aqueous solution of
OPVEBox•4Cl, the resulting mixtures show multicolor fluorescent outputs. All of the
luminescent color coordinates, which have been calculated and plotted (Figure 6c) in the CIE
1931 chromaticity diagram, demonstrate that the fluorescent color changes from skyblue to
bright yellow with the addition of 0  5.8 equiv of CB[8] to an solution of OPVEBox•4Cl. The
fluorescent conversion process can also be detected by the naked eye. Aqueous solutions of
OPVEBox•4Cl with different equivalents of CB[8] exhibit (Figure 6e) remarkable colorful
emission capacities, e.g., skyblue, cyan, green, yellow and gold. These observations signify that
the encapsulation of OPVEBox4+ by CB[8], not only improves significantly the luminescent
properties of tetracationic cyclophane by endowing it with higher quantum yield and a longer
lifetime, but also realizes multicolor fluorescent outputs from a single fluorophore in aqueous
solution. Because of the strong binding affinity34 (Ka = 8.3 × 1012 M−1) of memantine
hydrochloride (Mem) for CB[8], it is possible to investigate the dissociative behavior of the
ring-in-ring(s) complexes by exploiting Mem as a competitive guest. Upon the stepwise
addition of Mem to an aqueous solution of the OPVEBox•4Cl2CB[8] ring-in-rings complex,
the fluorescence intensity at 575 nm decreased (Figure S38a) gradually, while the maximum
emission wavelength was blue shifted to 482 nm, owing to the break up of the ring-in-ring(s)
complexes, affording the free OPVEBox4+. Also, the fluorescent color changes (Figure S38b)
from yellow back to skyblue. These results demonstrate that the emission colors can be tuned
reversibly by adding a competitive guest.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
■
CONCLUSION
A semi-rigid tetracationic cyclophane, OPVEBox4+, which has been designed and synthesized,
is able to serve as a guest instead of as a host, forming two ring-in-ring(s) complexes with
CB[8] molecules. The smaller tetracationic cyclophane CBPQT4+, which has the same p-
xylylene linkers as OPVEBox4+, however, does not form ring-in-ring(s) complexes with CB[8].
The formation of 1:1 and 1:2 complexes are driven, for the most part, by hydrophobic effect
11
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 12 of 31
1
2
3
4
5
6
7
8
9
and iondipole interactions. To the best of our knowledge, this 1:2 non-intertwined ring-in-
rings complex, where one ring is threaded by two other rings, is an unknown superstructure in
the chemical literature. These two new ring-in-ring(s) recognition motifs not only enrich
hostguest chemistry2a,35, but they could also serve as building blocks for the construction of
exotic mechanically interlocked molecules36.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Notably, benefiting from the excellent photophysical properties of OPVEBox4+ and the rigid
hydrophobic cavity provided by CB[8], the resulting binary and ternary complexes show green
and yellow fluorescence, respectively, both of which are red-shifted significantly compared
with the skyblue fluorescence of the free tetracationic cyclophane. Furthermore, multicolor
fluorescent emission e.g., skyblue, cyan, green, and yellowcan be achieved by simply
adding different equivalents of CB[8] to an aqueous solution of OPVEBox•4Cl. And the
emission colors can be reversibly tuned by adding the competitive guests. The use of
macrocycles to regulate the emission of organic molecules provides a simple strategy for
fabricating multicolor smart luminescent materials in aqueous solutions, which have potential
applications in the design and synthesis of multicolor biological imaging reagents and
encryption materials.
■
ASSOCIATED CONTENT
Supporting Information
Detailed synthetic procedures, crystallographic, binding thermodynamic, spectroscopic (NMR,
ESI-MS, UV-Vis absorption, and fluorescence) characterization data and DFT calculations for
the tetracationic cyclophanes, OPVEBox•4PF6 and OPVEBox•4Cl, as well as the binary
OPVEBox4+CB[8] and ternary OPVEBox4+2CB[8] ring-in-ring(s) complexes, are
included in Scheme S1, Figures S1−S50 and Tables S1−S6. This information is available free
of charge via the internet at http://pubs.acs.org.
■
AUTHOR INFORMATION
Corresponding Author
* E-mail: stoddart@northwestern.edu
Notes
The authors declare no competing financial interest.
12
ACS Paragon Plus Environment

Page 13 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
■
ACKNOWLEDGMENTS
7
8
9
The authors thank Northwestern University (NU) for their support of this research. This work
made use of the IMSERC X-RAY facility at Northwestern University, which has received
support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF
ECCS1542205), and Northwestern University. This research was also funded by the Center
for Sustainable Separations of Metals (CSSM), a National Science Foundation (NSF) Center
for Chemical Innovation (CCI), grant number CHE1925708. This research was supported
in part by the computational resources and staff contributions provided for by the Quest High
Performance Computing Facility at NU, which is jointly supported by the Office of the Provost,
the Office for Research, and Northwestern University Information Technology.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
■
REFERENCES
(1) (a) Pedersen, C. J. Cyclic Polyethers and Their Complexes with Metal Salts. J. Am. Chem.
Soc. 1967, 89, 2495−2496. (b) Pedersen, C. J. Cyclic Polyethers and Their Complexes with
Metal Salts. J. Am. Chem. Soc. 1967, 89, 7017−7036. (c) Pedersen, C. J. The Discovery of
Crown Ethers (Nobel Lecture). Angew. Chem., Int. Ed. Engl. 1988, 27, 1021−1027.
(2) (a) Cram, D. J.; Cram, J. M. Host-Guest Chemistry: Complexes between Organic
Compounds Simulate the Substrate Selectivity of Enzymes. Science 1974, 183, 803−809. (b)
Lehn, J.-M. Supramolecular Chemistry: Receptors, Catalysts, and Carriers. Science 1985, 227,
849−856. (c) Lehn, J.-M. Supramolecular Chemistry—Scope and Perspectives Molecules,
Supermolecules, and Molecular Devices (Nobel Lecture). Angew. Chem., Int. Ed. Engl. 1988,
27, 89−112. (d) Cram, D. J. The Design of Molecular Hosts, Guests, and Their Complexes
(Nobel Lecture). Angew. Chem., Int. Ed. Engl. 1988, 27, 1009−1020. (e) Leininger, S.;
Olenyuk, B.; Stang, P. J. Self-Assembly of Discrete Cyclic Nanostructures Mediated by
Transition Metals. Chem. Rev. 2000, 100, 853−908. (f)
Harada, A.; Takashima, Y.;
Yamaguchi, H. Cyclodextrin-Based Supramolecular Polymers. Chem. Soc. Rev. 2009, 38,
875−882. (g) Lee, S.; Chen, C. H.; Flood, A. H. A Pentagonal Cyanostar Macrocycle with
Cyanostilbene CH Donors Binds Anions and Forms Dialkylphosphate [3]Rotaxanes. Nat.
Chem. 2013, 5, 704−710. (h) Peng, S.; He, Q.; Vargas-Zuniga, G. I.; Qin, L.; Hwang, I.; Kim,
S. K.; Heo, N. J.; Lee, C. H.; Dutta, R.; Sessler, J. L. Strapped Calix[4]pyrroles: From Syntheses
to Applications. Chem. Soc. Rev. 2020, 49, 865−907.
13
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 14 of 31
1
2
3
4
5
6
7
8
9
(3) (a) Ikeda, A.; Shinkai, S. Novel Cavity Design Using Calix[n]arene Skeletons: Toward
Molecular Recognition and Metal Binding. Chem. Rev. 1997, 97, 1713−1734. (b) Rekharsky,
M. V.; Inoue, Y. Complexation Thermodynamics of Cyclodextrins. Chem. Rev. 1998, 98,
1875−1918. (c) Ogoshi, T.; Yamagishi, T. A.; Nakamoto, Y. Pillar-Shaped Macrocyclic
Hosts Pillar[n]arenes: New Key Players for Supramolecular Chemistry. Chem. Rev. 2016, 116,
7937−8002. (d) Ji, X.; Chi, X.; Ahmed, M.; Long, L.; Sessler, J. L. Soft Materials Constructed
Using Calix[4]pyrrole- and "Texas-Sized" Box-Based Anion Receptors. Acc. Chem. Res. 2019,
52, 1915−1927. (e) Liu, Y.; Zhao, W.; Chen, C. H.; Flood, A. H. Chloride Capture Using a
C-H Hydrogen-Bonding Cage. Science 2019, 365, 159−161.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(4) (a) Day, A. I.; Blanch, R. J.; Arnold, A. P.; Lorenzo, S.; Lewis, G. R.; Dance, I. A
Cucurbituril-Based Gyroscane: A New Supramolecular Form. Angew. Chem. Int. Ed. 2002, 41,
275−277. (b) Chiu, S.-H.; Pease, A. R.; Stoddart, J. F.; White, A. J. P.; Williams, D. J. A
Ring-in-Ring Complex. Angew. Chem. Int. Ed. 2002, 41, 270−274. (c)
Loren, J. C.;
Yoshizawa, M.; Haldimann, R. F.; Linden, A.; Siegel, J. S. Synthetic Approaches to a
Molecular Borromean Link: Two-Ring Threading with Polypyridine Templates. Angew. Chem.
Int. Ed. 2003, 42, 5702−5705. (d) Iwanaga, T.; Nakamoto, R.; Yasutake, M.; Takemura, H.;
Sako, K.; Shinmyozu, T. Cyclophanes within Cyclophanes: The Synthesis of a Pyromellitic
Diimide-Based Macrocycle as a Structural Unit in a Molecular Tube and Its Inclusion
Phenomena. Angew. Chem. Int. Ed. 2006, 45, 3643−3647. (e) Sun, B.; Wang, M.; Lou, Z.;
Huang, M.; Xu, C.; Li, X.; Chen, L. J.; Yu, Y.; Davis, G. L.; Xu, B.; Yang, H. B.; Li, X. From
Ring-in-Ring to Sphere-in-Sphere: Self-Assembly of Discrete 2D and 3D Architectures with
Increasing Stability. J. Am. Chem. Soc. 2015, 137, 1556−1564.
(5) (a) Kim, S.-Y.; Jung, I.-S.; Lee, E.; Kim, J.; Sakamoto, S.; Yamaguchi, K.; Kim, K.
Macrocycles within Macrocycles: Cyclen, Cyclam, and Their Transition Metal Complexes
Encapsulated in Cucurbit[8]uril. Angew. Chem. Int. Ed. 2001, 40, 2119−2121. (b) Dalgarno,
S. J.; Atwood, J. L.; Raston, C. L. Sulfonatocalixarenes: Molecular Capsule and 'Russian Doll'
Arrays to Structures Mimicking Viral Geometry. Chem. Commun. 2006, 4567−4574. (c)
Rousseaux, S. A.; Gong, J. Q.; Haver, R.; Odell, B.; Claridge, T. D.; Herz, L. M.; Anderson, H.
L. Self-Assembly of Russian Doll Concentric Porphyrin Nanorings. J. Am. Chem. Soc. 2015,
137, 12713−12718. (d) Zhiquan, L.; Polen, S.; Hadad, C. M.; RajanBabu, T. V.; Badjić, J. D.
Russian Nesting Doll Complexes of Molecular Baskets and Zinc Containing TPA Ligands. J.
Am. Chem. Soc. 2016, 138, 8253−8258. (e) Zhang, D.; Ronson, T. K.; Greenfield, J. L.; Brotin,
T.; Berthault, P.; Leonce, E.; Zhu, J. L.; Xu, L.; Nitschke, J. R. Enantiopure [Cs(+)/Xe
14
ACS Paragon Plus Environment

Page 15 of 31
Journal of the American Chemical Society
1
2
3
4
Cryptophane]FeII L4 Hierarchical Superstructures. J. Am. Chem. Soc. 2019, 141,
4
5
6
8339−8345.
(6) (a) Forgan, R. S.; Spruell, J. M.; Olsen, J.-C.; Stern, C., L.; Stoddart, J. F. Towards the
Stepwise Assembly of Molecular Borromean Rings. A Donor-Acceptor Ring-in-Ring Complex.
J. Mex. Chem. Soc. 2009, 53, 134−138. (b) Forgan, R. S.; Sauvage, J.-P.; Stoddart, J. F.
Chemical Topology: Complex Molecular Knots, Links, and Entanglements. Chem. Rev. 2011,
111, 5434−5464. (c) Forgan, R. S.; Wang, C.; Friedman, D. C.; Spruell, J. M.; Stern, C. L.;
Sarjeant, A. A.; Cao, D.; Stoddart, J. F. Donor-Acceptor Ring-in-Ring Complexes. Chem. Eur.
J. 2012, 18, 202−212. (d) Klosterman, J. K.; Veliks, J.; Frantz, D. K.; Yasui, Y.; Loepfe, M.;
Zysman-Colman, E.; Linden, A.; Siegel, J. S. Conformations of Large Macrocycles and Ring-
in-Ring Complexes. Org. Chem. Front. 2016, 3, 661−666. (e) Lu, Y.; Zhang, H. N.; Jin, G.
X. Molecular Borromean Rings Based on Half-Sandwich Organometallic Rectangles. Acc.
Chem. Res. 2018, 51, 2148−2158.
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(7) (a) Lipke, M. C.; Wu, Y.; Roy, I.; Wang, Y.; Wasielewski, M. R.; Stoddart, J. F. Shuttling
Rates, Electronic States, and Hysteresis in a Ring-in-Ring Rotaxane. ACS Cent. Sci. 2018, 4,
362−371. (b) Zhu, K.; Baggi, G.; Loeb, S. J. Ring-through-Ring Molecular Shuttling in a
Saturated [3]Rotaxane. Nat. Chem. 2018, 10, 625−630.
(8) (a) Zhu, L.; Li, X.; Zhang, Q.; Ma, X.; Li, M.; Zhang, H.; Luo, Z.; Agren, H.; Zhao, Y.
Unimolecular Photoconversion of Multicolor Luminescence on Hierarchical Self-Assemblies.
J. Am. Chem. Soc. 2013, 135, 5175−5182. (b) Mei, J.; Leung, N. L.; Kwok, R. T.; Lam, J.
W.; Tang, B. Z. Aggregation-Induced Emission: Together We Shine, United We Soar! Chem.
Rev. 2015, 115, 11718−11940. (c) Su, Y.; Phua, S. Z. F.; Li, Y.; Zhou, X.; Jana, D.; Liu, G.;
Lim, W. Q.; Ong, W. K.; Yang, C.; Zhao, Y. Ultralong Room Temperature Phosphorescence
from Amorphous Organic Materials toward Confidential Information Encryption and
Decryption. Sci. Adv. 2018, 4, eaas9732. (d) Su, Y.; Zhang, Y.; Wang, Z.; Gao, W.; Jia, P.;
Zhang, D.; Yang, C.; Li, Y.; Zhao, Y. Excitation-Dependent Long-Life Luminescent Polymeric
Systems under Ambient Conditions. Angew. Chem. Int. Ed. 2020, 59, 9967−9971.
(9) Lukinavicius, G.; Reymond, L.; Umezawa, K.; Sallin, O.; D'Este, E.; Gottfert, F.; Ta, H.;
Hell, S. W.; Urano, Y.; Johnsson, K. Fluorogenic Probes for Multicolor Imaging in Living Cells.
J. Am. Chem. Soc. 2016, 138, 9365−9368.
(10) (a) Qi, Q.; Li, C.; Liu, X.; Jiang, S.; Xu, Z.; Lee, R.; Zhu, M.; Xu, B.; Tian, W. Solid-
State Photoinduced Luminescence Switch for Advanced Anticounterfeiting and Super-
Resolution Imaging Applications. J. Am. Chem. Soc. 2017, 139, 16036−16039. (b) Wu, H.;
Chen, Y.; Liu, Y. Reversibly Photoswitchable Supramolecular Assembly and Its Application
15
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 16 of 31
1
2
3
4
5
6
7
8
9
as a Photoerasable Fluorescent Ink. Adv. Mater. 2017, 29, 1605271. (c) Gu, L.; Shi, H.; Bian,
L.; Gu, M.; Ling, K.; Wang, X.; Ma, H.; Cai, S.; Ning, W.; Fu, L.; Wang, H.; Wang, S.; Gao,
Y.; Yao, W.; Huo, F.; Tao, Y.; An, Z.; Liu, X.; Huang, W. Colour-Tunable Ultra-Long Organic
Phosphorescence of a Single-Component Molecular Crystal. Nat. Photonics. 2019, 13,
406−411.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(11) Li, S.; Peele, B. N.; Larson, C. M.; Zhao, H.; Shepherd, R. F. A Stretchable Multicolor
Display and Touch Interface Using Photopatterning and Transfer Printing. Adv. Mater. 2016,
28, 9770−9775.
(12) Kim, E.; Lee, Y.; Lee, S.; Park, S. B. Discovery, Understanding, and Bioapplication of
Organic Fluorophore: A Case Study with an Indolizine-Based Novel Fluorophore, Seoul-Fluor.
Acc. Chem. Res. 2015, 48, 538−547.
(13) (a) Ni, X. L.; Chen, S.; Yang, Y.; Tao, Z. Facile Cucurbit[8]uril-Based Supramolecular
Approach to Fabricate Tunable Luminescent Materials in Aqueous Solution. J. Am. Chem. Soc.
2016, 138, 6177−6183. (b) Wu, H.; Chen, Y.; Dai, X.; Li, P.; Stoddart, J. F.; Liu, Y. In Situ
Photoconversion of Multicolor Luminescence and Pure White Light Emission Based on Carbon
Dot-Supported Supramolecular Assembly. J. Am. Chem. Soc. 2019, 141, 6583−6591. (c)
Chen, W.; Guo, C.; He, Q.; Chi, X.; Lynch, V. M.; Zhang, Z.; Su, J.; Tian, H.; Sessler, J. L.
Molecular Cursor Caliper: A Fluorescent Sensor for Dicarboxylate Dianions. J. Am. Chem. Soc.
2019, 141, 14798−14806. (d) Chang, X.; Zhou, Z.; Shang, C.; Wang, G.; Wang, Z.; Qi, Y.;
Li, Z. Y.; Wang, H.; Cao, L.; Li, X.; Fang, Y.; Stang, P. J. Coordination-Driven Self-Assembled
Metallacycles Incorporating Pyrene: Fluorescence Mutability, Tunability, and Aromatic Amine
Sensing. J. Am. Chem. Soc. 2019, 141, 1757−1765. (e) Zhou, Z.; Chen, D. G.; Saha, M. L.;
Wang, H.; Li, X.; Chou, P. T.; Stang, P. J. Designed Conformation and Fluorescence Properties
of Self-Assembled Phenazine-Cored Platinum(II) Metallacycles. J. Am. Chem. Soc. 2019, 141,
5535−5543. (f) Wei, P.; Zhang, X.; Liu, J.; Shan, G. G.; Zhang, H.; Qi, J.; Zhao, W.; Sung,
H. H.; Williams, I. D.; Lam, J. W. Y.; Tang, B. Z. New Wine in Old Bottles: Prolonging Room-
Temperature Phosphorescence of Crown Ethers by Supramolecular Interactions. Angew. Chem.
Int. Ed. 2020, 59, 9293−9298.
(14) (a) Zhang, Q. W.; Li, D.; Li, X.; White, P. B.; Mecinovic, J.; Ma, X.; Agren, H.; Nolte,
R. J. M.; Tian, H. Multicolor Photoluminescence Including White-Light Emission by a Single
Host-Guest Complex. J. Am. Chem. Soc. 2016, 138, 13541−13550. (b) Wang, Q.; Zhang, Q.;
Zhang, Q. W.; Li, X.; Zhao, C. X.; Xu, T. Y.; Qu, D. H.; Tian, H. Color-Tunable Single-
Fluorophore Supramolecular System with Assembly-Encoded Emission. Nat. Commun. 2020,
11, 158.
16
ACS Paragon Plus Environment

Page 17 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
(15) (a) Odell, B.; Reddington, M. V.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Williams,
D. J. Cyclobis(paraquat-p-phenylene). A Tetracationic Multipurpose Receptor. Angew. Chem.,
Int. Ed. Engl. 1988, 27, 1547−1550. (b) Ashton, P. R.; Odell, B.; Reddington, M. V.; Slawin,
A. M. Z.; Stoddart, J. F.; Williams, D. J. Isostructural, Alternately-Charged Receptor Stacks.
The Inclusion Complexes of Hydroquinone and Catechol Dimethyl Ethers with
Cyclobis(paraquat-p-phenylene). Angew. Chem., Int. Ed. Engl. 1988, 27, 1550−1553.
(16) Ashton, P. R.; Brown, C. L.; Chrystal, E. J. T.; Goodnow, T. T.; Kaifer, A. E.; Parry, K.
P.; Philp, D.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Williams, D. J. The Self-Assembly
of a Highly Ordered [2]Catenane. J. Chem. Soc., Chem. Commun. 1991, 634−639.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(17)
Philp, D.; Slawin, A. M. Z.; Spencer, N.; Stoddart, J. F.; Williams, D. J. The
Complexation of Tetrathiafulvalene by Cyclobis(paraquat-p-phenylene). J. Chem. Soc., Chem.
Commun. 1991, 1584−1586.
(18) (a) Amabilino, D. B.; Ashton, P. R.; Boyd, S. E.; Lee, J. Y.; Menzer, S.; Stoddart, J. F.;
Williams, D. J. The Five-Stage Self-Assembly of a Branched Heptacatenane. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 2070−2072. (b) Stoddart, J. F. The Chemistry of the Mechanical Bond.
Chem. Soc. Rev. 2009, 38, 1802−1820.
(19) (a) Spruell, J. M.; Coskun, A.; Friedman, D. C.; Forgan, R. S.; Sarjeant, A. A.; Trabolsi,
A.; Fahrenbach, A. C.; Barin, G.; Paxton, W. F.; Dey, S. K.; Olson, M. A.; Benitez, D.;
Tkatchouk, E.; Colvin, M. T.; Carmielli, R.; Caldwell, S. T.; Rosair, G. M.; Hewage, S. G.;
Duclairoir, F.; Seymour, J. L.; Slawin, A. M.; Goddard, W. A., III; Wasielewski, M. R.; Cooke,
G.; Stoddart, J. F. Highly Stable Tetrathiafulvalene Radical Dimers in [3]Catenanes. Nat. Chem.
2010, 2, 870−879. (b) Dale, E. J.; Vermeulen, N. A.; Thomas, A. A.; Barnes, J. C.; Juríček,
M.; Blackburn, A. K.; Strutt, N. L.; Sarjeant, A. A.; Stern, C. L.; Denmark, S. E.; Stoddart, J.
F. Excage. J. Am. Chem. Soc. 2014, 136, 10669−10682. (c) Wu, H.; Chen, Y.; Zhang, L.;
Anamimoghadam, O.; Shen, D.; Liu, Z.; Cai, K.; Pezzato, C.; Stern, C. L.; Liu, Y.; Stoddart, J.
F. A Dynamic Tetracationic Macrocycle Exhibiting Photoswitchable Molecular Encapsulation.
J. Am. Chem. Soc. 2019, 141, 1280−1289.
(20) Dale, E. J.; Vermeulen, N. A.; Juríček, M.; Barnes, J. C.; Young, R. M.; Wasielewski,
M. R.; Stoddart, J. F. Supramolecular Explorations: Exhibiting the Extent of Extended Cationic
Cyclophanes. Acc. Chem. Res. 2016, 49, 262−273.
(21) (a) Lipke, M. C.; Cheng, T.; Wu, Y.; Arslan, H.; Xiao, H.; Wasielewski, M. R.; Goddard,
W. A., III; Stoddart, J. F. Size-Matched Radical Multivalency. J. Am. Chem. Soc. 2017, 139,
3986−3998. (b) Dumartin, M.; Lipke, M. C.; Stoddart, J. F. A Redox-Switchable Molecular
Zipper. J. Am. Chem. Soc. 2019, 141, 18308−18317.
17
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 18 of 31
1
2
3
4
5
6
(22) Cai, K.; Lipke, M. C.; Liu, Z.; Nelson, J.; Cheng, T.; Shi, Y.; Cheng, C.; Shen, D.; Han,
J. M.; Vemuri, S.; Feng, Y.; Stern, C. L.; Goddard, W. A., III; Wasielewski, M. R.; Stoddart, J.
F. Molecular Russian Dolls. Nat. Commun. 2018, 9, 5275.
7
8
9
(23) (a) Freeman, W. A.; Mock, W. L.; Shih, N. Y. Cucurbituril. J. Am. Chem. Soc. 1981,
103, 7367−7368. (b) Mock, W. L.; Shih, N. Y. Host-Guest Binding Capacity of Cucurbituril.
J. Org. Chem. 1983, 48, 3618−3619. (c) Liu, S.; Zavalij, P. Y.; Isaacs, L. Cucurbit[10]uril. J.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Am. Chem. Soc. 2005, 127, 16798−16799. (d)
Isaacs, L. Stimuli Responsive Systems
Constructed Using Cucurbit[n]uril-Type Molecular Containers. Acc. Chem. Res. 2014, 47,
2052−2062. (e) Barrow, S. J.; Kasera, S.; Rowland, M. J.; del Barrio, J.; Scherman, O. A.
Cucurbituril-Based Molecular Recognition. Chem. Rev. 2015, 115, 12320−12406. (f) Das, D.;
Assaf, K. I.; Nau, W. M. Applications of Cucurbiturils in Medicinal Chemistry and Chemical
Biology. Front. Chem. 2019, 7, 619.
(24) (a) Kim, H. J.; Jeon, W. S.; Ko, Y. H.; Kim, K. Inclusion of Methylviologen in
Cucurbit[7]uril. Proc. Natl. Acad. Sci. U. S. A. 2002, 99, 5007−5011. (b) Ong, W.; Kaifer, A.
E. Salt Effects on the Apparent Stability of the Cucurbit[7]uril-Methyl Viologen Inclusion
Complex. J. Org. Chem. 2004, 69, 1383−1385. (c) Liu, S.; Ruspic, C.; Mukhopadhyay, P.;
Chakrabarti, S.; Zavalij, P. Y.; Isaacs, L. The Cucurbit[n]uril Family: Prime Components for
Self-Sorting Systems. J. Am. Chem. Soc. 2005, 127, 15959−15967.
(25) Gong, W.; Yang, X.; Zavalij, P. Y.; Isaacs, L.; Zhao, Z.; Liu, S. From Packed “Sandwich”
to “Russian Doll”: Assembly by Charge-Transfer Interactions in Cucurbit[10]uril. Chem. Eur.
J. 2016, 22, 17612−17618.
(26) (a) Kim, J.; Jung, I.-S.; Kim, S.-Y.; Lee, E.; Kang, J.-K.; Sakamoto, S.; Yamaguchi, K.;
Kim, K. New Cucurbituril Homologues: Syntheses, Isolation, Characterization, and X-Ray
Crystal Structures of Cucurbit[n]uril (n = 5, 7, and 8). J. Am. Chem. Soc. 2000, 122, 540−541.
(b) All the distances defining the size of CB[8] in the current research were measured from
atom to atom according to the single crystal of CB[8] in reference 26a.
(27) (a) Kim, H.-J.; Heo, J.; Jeon, W. S.; Lee, E.; Kim, J.; Sakamoto, S.; Yamaguchi, K.; Kim,
K. Selective Inclusion of a Hetero-Guest Pair in a Molecular Host: Formation of Stable Charge-
Transfer Complexes in Cucurbit[8]uril. Angew. Chem. Int. Ed. 2001, 40, 1526−1529. (b)
Bush, M. E.; Bouley, N. D.; Urbach, A. R. Charge-Mediated Recognition of N-Terminal
Tryptophan in Aqueous Solution by a Synthetic Host. J. Am. Chem. Soc. 2005, 127,
14511−14517. (c) Biedermann, F.; Rauwald, U.; Cziferszky, M.; Williams, K. A.; Gann, L.
D.; Guo, B. Y.; Urbach, A. R.; Bielawski, C. W.; Scherman, O. A. Benzobis(imidazolium)-
Cucurbit[8]uril Complexes for Binding and Sensing Aromatic Compounds in Aqueous Solution.
18
ACS Paragon Plus Environment

Page 19 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
Chem. Eur. J. 2010, 16, 13716−13722. (d) Yang, X.; Wang, R.; Kermagoret, A.; Bardelang,
D. Oligomeric Cucurbituril Complexes: From Peculiar Assemblies to Emerging Applications.
Angew. Chem. Int. Ed. 2020, DOI: 10.1002/anie.202004622.
7
8
9
(28) (a) Huang, Z.; Yang, L.; Liu, Y.; Wang, Z.; Scherman, O. A.; Zhang, X. Supramolecular
Polymerization Promoted and Controlled through Self-Sorting. Angew. Chem. Int. Ed. 2014,
53, 5351−5355. (b) Yang, H.; Ma, Z.; Yuan, B.; Wang, Z.; Zhang, X. Supramolecular
Polymerization at the Interface: Layer-by-Layer Assembly Driven by Host-Enhanced π-π
Interaction. Chem. Commun. 2014, 50, 11173−11176.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(29) (a) Zhang, K. D.; Tian, J.; Hanifi, D.; Zhang, Y.; Sue, A. C.; Zhou, T. Y.; Zhang, L.;
Zhao, X.; Liu, Y.; Li, Z. T. Toward a Single-Layer Two-Dimensional Honeycomb
Supramolecular Organic Framework in Water. J. Am. Chem. Soc. 2013, 135, 17913−17918. (b)
Tian, J.; Zhou, T. Y.; Zhang, S. C.; Aloni, S.; Altoe, M. V.; Xie, S. H.; Wang, H.; Zhang, D.
W.; Zhao, X.; Liu, Y.; Li, Z. T. Three-Dimensional Periodic Supramolecular Organic
Framework Ion Sponge in Water and Microcrystals. Nat. Commun. 2014, 5, 5574.
(30) (a) Jeon, W. S.; Kim, H. J.; Lee, C.; Kim, K. Control of the Stoichiometry in Host-Guest
Complexation by Redox Chemistry of Guests: Inclusion of Methylviologen in Cucurbit[8]uril.
Chem. Commun. 2002, 1828−1829. (b) Carvalho, C. P.; Dominguez, Z.; Da Silva, J. P.;
Pischel, U. A Supramolecular Keypad Lock. Chem. Commun. 2015, 51, 2698−2701. (c) Tang,
X.; Huang, Z.; Chen, H.; Kang, Y.; Xu, J. F.; Zhang, X. Supramolecularly Catalyzed
Polymerization: From Consecutive Dimerization to Polymerization. Angew. Chem. Int. Ed.
2018, 57, 8545−8549. (d) Olesinska, M.; Wu, G.; Gomez-Coca, S.; Anton-Garcia, D.; Szabo,
I.; Rosta, E.; Scherman, O. A. Modular Supramolecular Dimerization of Optically Tunable
Extended Aryl Viologens. Chem. Sci. 2019, 10, 8806−8811. (e) Wu, G.; Szabo, I.; Rosta, E.;
Scherman, O. A. Cucurbit[8]uril-Mediated Pseudo[2,3]rotaxanes. Chem. Commun. 2019, 55,
13227−13230. (f) Wu, G.; Bae, Y. J.; Olesińska, M.; Antón-García, D.; Szabó, I.; Rosta, E.;
Wasielewski, M. R.; Scherman, O. A. Controlling the Structure and Photophysics of
Fluorophore Dimers Using Multiple Cucurbit[8]uril Clampings. Chem. Sci. 2020, 11, 812−825.
(31) (a) Koshland, D. E. Application of a Theory of Enzyme Specificity to Protein Synthesis.
Proc. Natl. Acad. Sci. U. S. A. 1958, 44, 98−104. (b) Koshland, D. E. The Key–Lock Theory
and the Induced Fit Theory. Angew. Chem., Int. Ed. Engl. 1995, 33, 2375−2378. (c) Sawada,
T.; Hisada, H.; Fujita, M. Mutual Induced Fit in a Synthetic Host-Guest System. J. Am. Chem.
Soc. 2014, 136, 4449−4451.
19
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 20 of 31
1
2
3
4
5
6
(32) Peck, E. M.; Liu, W.; Spence, G. T.; Shaw, S. K.; Davis, A. P.; Destecroix, H.; Smith,
B. D. Rapid Macrocycle Threading by a Fluorescent Dye-Polymer Conjugate in Water with
Nanomolar Affinity. J. Am. Chem. Soc. 2015, 137, 8668−8671.
7
8
9
(33) (a) Ihde, J. Le Châtelier and Chemical Equilibrium. J. Chem. Educ. 1989, 66, 238. (b)
Dhara, A.; Flood, A. H. Cages Driven Away from Equilibrium Binding by Electric Fields.
Chem 2019, 5, 1017−1019.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(34) Sinn, S.; Spuling, E.; Brase, S.; Biedermann, F. Rational Design and Implementation of
a Cucurbit[8]uril-Based Indicator-Displacement Assay for Application in Blood Serum. Chem.
Sci. 2019, 10, 6584−6593.
(35) (a) Hua, Y.; Flood, A. H. Click Chemistry Generates Privileged CH Hydrogen-Bonding
Triazoles: The Latest Addition to Anion Supramolecular Chemistry. Chem. Soc. Rev. 2010, 39,
1262−1271. (b) Xia, D.; Wang, P.; Ji, X.; Khashab, N. M.; Sessler, J. L.; Huang, F. Functional
Supramolecular Polymeric Networks: The Marriage of Covalent Polymers and Macrocycle-
Based Host-Guest Interactions. Chem. Rev. 2020, 120, 6070−6123.
(36) (a) Raymo, F. M.; Stoddart, J. F. Interlocked Macromolecules. Chem. Rev. 1999, 99,
1643−1664. (b) Fang, L.; Olson, M. A.; Benitez, D.; Tkatchouk, E.; Goddard, W. A., III;
Stoddart, J. F. Mechanically Bonded Macromolecules. Chem. Soc. Rev. 2010, 39, 17−29. (c)
Mena-Hernando, S.; Perez, E. M. Mechanically Interlocked Materials. Rotaxanes and
Catenanes Beyond the Small Molecule. Chem. Soc. Rev. 2019, 48, 5016−5032.
20
ACS Paragon Plus Environment

Page 21 of 31
Journal of the American Chemical Society
1
2
3
4
5
Captions to Scheme and Figures
6
7
8
9
Scheme 1. Structural formulas and schematic illustrations of the different binding behaviors of
(a) CBPQT4+ and (b) OPVEBox4+ with CB[8], respectively
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. Solid-state (super)structure of OPVEBox4+ obtained by X-ray crystallography on
single crystals of OPVEBox•4Cl. (a) Space-filling representation, showing the box-like
geometry of OPVEBox4+. (b−c) Capped-stick representations of plan and side-on views,
showing the distances defining the box-like geometry of OPVEBox4+. (d) Ball-and-stick
representations of different side-on views, showing how OPVEBox4+ interacts with 16 Cl−
anions by [CHCl] hydrogen bonding. (e) Solid-state superstructure of OPVEBox•4Cl,
revealing how OPVEBox4+ and the Cl− anions adopt an alternating arrangement. Solvent
molecules have been omitted for the sake of clarity. H gray, C skyblue, N blue, Cl green.
Figure 2. 1H NMR Spectra (600 MHz, D2O, 298 K) of (a) CBPQT•4Cl, and (b) CBPQT•4Cl
with an equimolar amount of CB[8]. (c) OPVEBox•4Cl. (d) The binary OPVEBox4+CB[8],
and (e) the ternary OPVEBox4+2CB[8] ring-in-ring(s) complexes.
Figure 3. 2D DOSY Spectra (600 MHz, D2O, 298 K) of (a) binary OPVEBox4+CB[8] and
(b) ternary OPVEBox4+2CB[8] ring-in-ring(s) complexes. Electrospray ionization-mass
spectra (ESI-MS) of (c) binary OPVEBox4+CB[8] and (d) ternary OPVEBox4+2CB[8]
ring-in-ring(s) complexes. The inset in ESI-MS represents the theoretical and experimental
isotope patterns for the 4+ charge states of the binary and ternary ring-in-ring(s) complexes.
The brown “4+” represents the four positively charged state of the OPVEBox4+CB[8]
complex, while the blue “4+, 5+, 6+” represent the four, five, six positively charged states of
the OPVEBox4+2CB[8] complex, accompanied by additions of differing numbers of Na+ ions.
Figure 4. (ab) Capped-stick and space-filling representations of the optimized superstructure
of the binary OPVEBox4+CB[8] complex determined by DFT calculations. (cd) The
structures of individual OPVEBox4+ and CB[8] in the binary complex, showing the
characteristic distances defining their geometries. (ef) Capped-stick and space-filling
representations of the optimized superstructure of the ternary OPVEBox4+2CB[8] complex
determined by DFT calculations. (gh) The structures of individual OPVEBox4+ and CB[8] in
the ternary complex, showing the characteristic distances defining their geometries. (il)
Electrostatic potential maps of the ternary OPVEBox4+2CB[8] and binary
OPVEBox4+CB[8] ring-in-ring(s) complexes, as well as the free OPVEBox4+ and CB[8],
21
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 22 of 31
1
2
3
4
5
6
respectively. Red and deep-blue colors in the maps represent negative and positive electrostatic
potentials, respectively.
7
8
9
Figure 5. (a) UV-Vis Absorption spectra ([OPVEBox•4Cl] = 4 M, [CB[8]] = 0− 20 M, H2O,
298 K) and (b) absorbance intensity changes at 415 nm of OPVEBox•4Cl upon gradual
addition of CB[8] in an aqueous solution.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. (a) Fluorometric titration and (b) Fluorescence intensity changes at 482 and 575 nm,
when continuing to add CB[8] to an aqueous solution of OPVEBox•4Cl ([OPVEBox•4Cl] =
2 M, [CB[8]] = 0−11.6 M, λex = 392 nm, H2O, 298 K). (c) The 1931 CIE chromaticity
diagram illustrating the luminescent color changes of OPVEBox•4Cl with the continuous
addition of CB[8], corresponding to (a). (d) Emission spectra recording the spectral changes
for OPVEBox•4Cl ([OPVEBox•4Cl] = 2 M, [CB[8]] = 0−3 equiv., λex = 392 nm, H2O, 298
K) upon addition of different equiv of CB[8] in an aqueous solution. (e) Fluorescent
photographs showing the visual changes in luminescent color of OPVEBox•4Cl with addition
of increasing equivalents of CB[8] in aqueous solution.
22
ACS Paragon Plus Environment

Page 23 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Scheme 1
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 24 of 31
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Figure 1
ACS Paragon Plus Environment

Page 25 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Figure 2
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 26 of 31
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Figure 3
ACS Paragon Plus Environment

Page 27 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Figure 4
ACS Paragon Plus Environment

Journal of the American Chemical Society
Page 28 of 31
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 5
ACS Paragon Plus Environment

Page 29 of 31
Journal of the American Chemical Society
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
Figure 6
ACS Paragon Plus Environment