Emission enhancement of cationic tetraphenylethylene derivatives by encapsulation in a cucurbit[10]uril host in water

Article abstract of DOI:10.1039/c9nj06209b

Binding of a series of cationic tetraphenylethylene (TPE) derivatives with a cucurbit[10]uril (CB[10]) host has been investigated. Compared to the free forms, all guests exhibit fluorescence enhancement upon encapsulation by CB[10]. Thus, by restricting i

Full text of DOI:10.1039/c9nj06209b

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Emission enhancement of cationic tetraphenylethylene
derivatives by encapsulation in cucurbit[10]uril host in water
Chang Liu,a Yong Wu,a Xie Hana and Simin Liu*a,b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Binding of a series of cationic tetraphenylethylene (TPE) derivatives Wang and co-workers synthesized a TPE- functionalized
with cucurbit[10]uril (CB[10]) host has been investigated. pillar[5]arene which exhibits the ‘‘turn-on’’ of fluorescence
Compared to the free forms, all guests exhibit fluorescence emission based on host–guest recognition-mediated cross-
enhancement upon encapsulation by CB[10]. Thus, by restricting linking.18 Yang et al. demonstrated that TPE decorated
intramolecular rotation through host-guest encapsulation instead pillar[5]arene units could be used to construct AIE
of aggregation, fluorescence enhancement of TPE derivatives can supramolecular polymer gels with multiple stimuli-responsive
be realized in water.
behaviours.19
Luminescent molecules have attracted considerable research
interests, owing to their broad applications in
photoluminescent probes, biological applications, light-
harvesting systems, white-light emission systems, and so on.1-5
However, most of the luminophores are weakly emissive or
non-emissive in the aggregated and solid states because of
aggregation-caused quenching (ACQ) effect.6 In 2001, Tang’s
group defined the aggregation-induced emission (AIE) effect
and disclosed the mechanism called restriction of
intramolecular rotation (RIR).7 Tetraphenylethylene (TPE)
molecules, a typical aggregation-induced emission luminogens
(AIEgens), has been widely used in many fields such as chemical
sensors, biological probes, cell Imaging and so on.8-11 Therefore,
activating the RIR process of TPE is a key factor to realize the
strong fluorescence of TPE derivatives.12 Up to now, many
efficient methods such as intermolecular network13,14 and rigid
metal–organic framework,15 have been used to achieve this goal.
Recently, host–guest complexation has attracted
considerable attention for its wide applications in modulating
the photophysical properties of fluorescent molecules.16 What’s
more, host-guest interactions can be used as physical processes
to restrict the intramolecular rotation of TPE unit, and construct
functional TPE supramolecular assemblies.17 For examples,
Fig. 1 Structures of host and guest compounds (a, b), and schematic
illustration of the formation of two plausible inclusion complexes between
TPE guest and CB[10] (c).
a. The State Key Laboratory of Refractories and Metallurgy, School of Chemistry and
Chemical Engineering, Wuhan University of Science and Technology, Wuhan
430081, China. E-mail: liusimin@wust.edu.cn.
b. Institute of Advanced Materials and Nanotechnology, Wuhan University of Science
and Technology, Wuhan 430081, China.
Cucurbit[n]uril (CB[n], n = 5–8, 10) is a kind of rigid
macrocyclic host with various sized hydrophobic cavity, and has
been found many applications.20-22 Recently, CB[n] was also
Electronic Supplementary Information (ESI) available: synthesis and
characterization of TPE guests, binding data of guests with CB[10]. See
DOI: 10.1039/x0xx00000x
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used as “linker” to fabricate supramolecular functional AIE corresponding proton resonances.39 UnfortunVaietwelAyr,ticlewOhnleinne
materials containing TPE units.23-29 In these cases, substituted further studying the fluorescence chanDgOeI: 1o0f.10g3u9e/Cs9tN1J06u2p0o9nB
groups on TPE cores bind internally or externally to CB[n] to addition of CB[10], we found that the fluorescence intensity of
limit the intramolecular rotation, causing the assembling- complex CB[10]· is not enhanced as expected (Fig. S5, ESI†). It
induced emission enhancement.30
seems that CB[10] could not efficiently limit the intramolecular
Among the CB[n] family, CB[10] possesses the largest cavity rotation of guest . Another possibility is that high pH may not
with a volume of ~870 Å3 and the portal diameter of ~10 Å.31 be good for the fluorescence of guest
. So we synthesized
Therefore, bigger or multiple guests, such as Blue Box, metal– other two molecules and
By taking advantage of good solubilities of 2 and 3 in neutral
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terpyridyl complexes, could be selectively encapsulated by
CB[10].32-38 Herein, we report another supramolecular host– pH, we investigated the binding interactions between them and
guest strategy to activate the RIR process of TPE units through CB[10] via 1H NMR spectroscopy in D2O. As seen in Fig. 2a and
encapsulation of TPE core in CB[10]. The results show all 2b, the signals for Ha and Hb proton on the aromatic rings of
2
selected TPE guests can form 1:1 inclusion complexes with significantly shifted upfield. And overlapping signals for Ha and
CB[10] in aqueous solution, arousing an increased molecular Hb proton (Fig. 2a) can be differentiated in the presence of
emission enhancement. Two binding modes of host–guest CB[10] (Fig. 2b), which is because Ha proton is located deeper in
complexation in which the vinyl group of TPE is perpendicular the cavity of CB[10] than Hb proton. Although the binding
1
or parallel to the port of CB[10] were observed.
between
2
and CB[10] exhibits slow exchange kinetics on H
CB[10] is extremely insoluble in aqueous solution unlike other NMR time scale, observation of broadening of all proton signals
CB[n]s, but it could be dissolved in water phase after forming implies that interesting kinetic binding happened. Like guest
inclusion complexes with a water-soluble guest.32 So we relied the binding of
with CB[10] also shows slow exchange kinetics
2,
3
on water-soluble cationic TPE derivatives as much as possible. (Fig. 2d-2f). Difference is that more host and guest peaks were
And binding studies of TPE derivatives with CB[10] were observed. Integration for host and guest protons (Fig. S6) and
investigated according to 1H NMR titration which has been COSY NMR (Fig. S7) show: 1) the binding ratio of host-guest is
utilized to characterize host-guest binding behaviours.39
1:1; the ratio of two bound methyl group (& and # at 3.01 and
2.80 ppm in Fig 2f) is ~ 1:2 (same ratio for bound CB[10] peaks
at 5.82 and 5.71 ppm). All results suggest that two binding
modes exist in the complex CB[10]·
Considering all results and the structure of
that the vinyl group of TPE is parallel to the port of CB[10] in one
mode (mode in Fig 1c) and perpendicular in the other (mode
in Fig 1c). So broadening of signals for all protons of CB[10]·
3
and the ratio of them is 1:2.
3, we highly believe
A
B
2
in Fig. 2c could be the results of fast switching between mode
and
complexation of CB[10] and
A
B
. Additionally, the ESI-MS test further proves the 1:1
3
(m/z = 787.29) (Fig. S8, ESI†).
Fig. 3 UV/vis spectra (a) and fluorescence spectra (b) of 2 with addition of
Fig. 2 1H NMR spectra (600 MHz, D2O, 298K) of: a) free 2 (1.0 mM); b) 2:1
mixture of 2 and CB[10]; c) CB[10]·2 (1.0 mM); d) free 3 (1.0 mM); e) 2:1
mixture of 3 and CB[10]; f) CB[10]·3 (1.0 mM) (resonances of free 2 and 3 are
marked with *; resonances representing two binding modes for CB[10]·3 are
marked with # and &).
Dissolution of CB[10] was observed when it was added to an
acidic aqueous solution of TPE guest
1, implying the
1
complexation of
1
with CB[10]. H NMR titration in D2O/DCl
CB[10] (0, 0.5 equiv., 1.0 equiv.) ([
(c) and fluorescence spectra (d) of
λex = 310 nm, slit = 5 Χ 5 nm).
2
] = 10 μM, λex =320 nm); UV/vis spectra
with addition of CB[10] ([ ] = 10 μM,
showed that all signals of aromatic proton shifted upfield,
suggesting the encapsulation of whole TPE core inside the cavity
of CB[10] (Fig. S4, ESI†). Slow exchange kinetics on the 1H NMR
time scale allowed us to calculate the binding ratio between
host and guest as 1:1, based on the integrals of the
3
3
UV/vis and fluorescence spectroscopies were employed to
further investigate the complexation of CB[10] with and the
2/3
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influence of CB[10] on the emission property of guest
illustrated in Fig. 3a, the characteristic absorption peak of TPE attributed to that the benzene ring without substituent binding
moiety at about 320 nm decreased with addition of CB[10] to sites can rotate freely in the cavity of CB[10]. Meanwhile, when
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DOI: 10.1039/C9NJ06209B
the aqueous solution of guest
showed that free guest exhibits weak fluorescence emission dissolved first then precipitate formed. Peaks representing
at 480 nm. However with addition of CB[10], the increase of guest
and CB[10] can not be observed in the 1H NMR spectra
emission intensity with 7 times stronger than that of free was (Fig. S10, ESI†), implying the formation of insoluble complex
observed when 1 equivalent of CB[10] was added (Fig. 3b). And CB[10]·
for the CB[10]· complex, the UV/vis spectrum showed similar In conclusion, based on the host-guest interaction, we
tendency of the decreased absorptions due to the host-guest reported for the first time that cationic TPE derivatives showed
complexaion (Fig. 3c). Similar to guest , emission intensity of an enhanced molecular emission when they were encapsulated
increased 8 times in the presence of CB[10], compared to the in the cavity of CB[10] in an aqueous solution. Guests and
free in water (Fig. 3d). Interestingly, in this case about 60 nm exhibit fluorescence enhancement when 1 equivalent of CB[10]
blue-shift was observed with addition of 1 equivalent of CB[10], existed. As the binding sites decrease, the time of emission
which could be caused by the enhancement of conformational enhancement of guests are less than the former. All results
planarization.41 Both of the UV/vis and fluorescence spectra prove that encapsulation in host CB[10] dramatically limit the
titration clearly demonstrated the complexation of with intramolecular rotation of TPE guests. Our strategy does not
CB[10]. Although all guests can be encapsulated by CB[10], request the aggregation of TPE molecules, suggesting that much
emission intensity of increased more than . This lower concentration might be adopted for AIEgens broad
2. Fluorescence spectroscopy CB[10] was added into the aqueous solution of 5, we saw CB[10]
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fluorescence turn-on phenomenon could be explained by application.
efficient restriction of intramolecular rotation resulted from the
formation of CB[10]·
factors.16
2 and CB[10]·3 complexes, as well as other
Conflicts of interest
There are no conflicts to declare.
With above results in hand, we wondered whether two-
substituted TPE derivatives ( and in Fig. 1b) show the similar
4
5
emission enhancement, since these guests could be further
used in designing functional materials with CB[10]. Instead, if
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (21871216, 21901194, 21472143) and the
Thousand Youth Talents Program of China.
four big (or long) groups attached on phenyl groups of guest
or , we doubt CB[10] could cover the TPE core.
2
3
Notes and references
1
H. Kobayashi, M. Ogawa, R. Alford, P. L. Choyke and Y. Urano,
Chem. Rev., 2010, 110, 2620-2640.
2
3
4
J. Liu, Z. Cao and Y. Lu, Chem. Rev., 2009, 109, 1948-1998.
X. Li, S. Lee and J. Yoon, Chem. Soc. Rev., 2018, 47, 1174-1188.
D. Gust, T. A. Moore and A. L. Moore, Acc. Chem. Res., 2001,
34, 40-48.
5
6
7
G. M. Farinola and R. Ragni, Chem. Soc. Rev., 2011, 40, 3467-
3482.
J. B. Birks, Photophysics of Aromatic Molecules, Wiley, London,
1970.
J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, H. Chen, C. Qiu, H. S. Kwok,
X. Zhan, Y. Liu, D. Zhu and B. Z. Tang, Chem. Commun., 2001,
1740-1741.
Fig. 4 1H NMR spectra (600 MHz, D2O, 298K) of: a) free 4 (1.0 mM); b) 2:1
mixture of 4 and CB[10]; c) CB[10]·4 (1.0 mM) (resonances of free 4 are
marked with *).
8
9
J. Mei, N. L. C. Leung, R. T. K. Kwok, J. W. Y. Lam and B. Z. Tang,
Chem. Rev., 2015, 115, 11718-11940.
M. Gao and B. Z. Tang, ACS Sensors, 2017, 2, 1382-1399.
10 D. D. La, S. V. Bhosale, L. A. Jones and S. V. Bhosale, ACS Appl.
Mater. Interfaces, 2018, 10, 12189-12216.
From Fig. 4, we can see that the binding between guest 4 and
CB[10] exhibits fast exchange kinetics on NMR time scale,
possibly resulting from the less binding sites compared to
11 R. Hu, E. Lager, A. Aguilar-Aguilar, J. Liu, J. W. Y. Lam, H. H. Y.
Sung, I. D. Williams, Y. Zhong, K. S. Wong, E. Peña-Cabrera and
B. Z. Tang, J. Phys. Chem. C., 2009, 113, 15845-15853.
12 Y. Chen, J. W. Y. Lam, R. T. K. Kwok, B. Liu and B. Z. Tang, Mater.
guests
1-
3. Integration suggests the formation of 1:1 complex
CB[10]·4. Furthermore, the complexation could also be
confirmed by UV/vis spectroscopy (Fig. S9, ESI†). The average
decrease of absorption intensity implies the 1:1 complexation.
Horiz., 2019, 6, 428-433.
13 Y. Xu, L. Chen, Z. Guo, A. Nagai and D. Jiang, J. Am. Chem. Soc.,
2011, 133, 17622-17625.
14 X. Li, Z. Li and Y.-W. Yang, Adv. Mater., 2018, 30, 1800177.
As expected, the fluorescence intensity of
4 was increased in
the presence of CB[10] (Fig. S9, ESI†) but with up to 3 times
This journal is © The Royal Society of Chemistry 20xx
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Journal Name
1
2
3
4
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6
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9
15 N. B. Shustova, T.-C. Ong, A. F. Cozzolino, V. K. Michaelis, R. G.
Griffin and M. Dincă, J. Am. Chem. Soc., 2012, 134, 15061-
15070.
View Article Online
DOI: 10.1039/C9NJ06209B
16 R. N. Dsouza, U. Pischel and W. M. Nau, Chem. Rev., 2011, 111
,
7941-7980.
17 X.-Y. Lou and Y.-W. Yang, Adv. Optical Mater., 2018,
6,
1800668.
18 J. Wu, S. Sun, X. Feng, J. Shi, X.-Y. Hu and L. Wang, Chem.
Commun., 2014, 50, 9122-9125.
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
19 C.-W. Zhang, B. Ou, S.-T. Jiang, G.-Q. Yin, L.-J. Chen, L. Xu, X. Li
and H.-B. Yang, Polym. Chem., 2018, 9, 2021-2030.
20 J. Lagona, P. Mukhopadhyay, S. Chakrabarti and L. Isaacs,
Angew. Chem., Int. Ed., 2005, 44, 4844-4870.
21 E. Masson, X. Ling, R. Joseph, L. Kyeremeh-Mensah and X. Lu,
RSC Adv., 2012, 2, 1213-1247.
22 S. J. Barrow, S. Kasera, M. J. Rowland, J. del Barrio and O. A.
Scherman, Chem. Rev., 2015, 115, 12320-12406.
23 S.-Q. Xu, X. Zhang, C.-B. Nie, Z.-F. Pang, X.-N. Xu and X. Zhao,
Chem. Commun., 2015, 51, 16417-16420.
24 F. Qiao, Z. Yuan, Z. Lian, C.-Y. Yan, S. Zhuo, Z.-Y. Zhou and L.-B.
Xing, Dyes Pigments, 2017, 146, 392-397.
25 X.-M. Chen, Y.-M. Zhang and Y. Liu, Supramol. Chem., 2016, 28
817-824.
26 G. Jiang, W. Zhu, Q. Chen, X. Li, G. Zhang, Y. Li, X. Fan and J.
Wang, Sensor. Actuat. B-Chem., 2018, 261, 602-607.
27 Y. Li, Y. Dong, X. Miao, Y. Ren, B. Zhang, P. Wang, Y. Yu, B. Li,
L. Isaacs and L. Cao, Angew. Chem., Int. Ed., 2018, 57, 729-733.
28 Y. Wu, H. Hua and Q. Wang, New J. Chem., 2018, 42, 8320-
8324.
29 H. Zhang, F. Liang and Y.-W. Yang, Chem. Eur. J., 2019, 25, DOI:
10.1002/chem.201904443.
30 X. Ma, J. Wang and H. Tian, Acc. Chem. Res., 2019, 52, 738-
748.
,
31 S. Liu, P. Y. Zavalij and L. Isaacs, J. Am. Chem. Soc., 2005, 127
,
16798-16799.
32 X. Yang, F. Liu, Z. Zhao, F. Liang, H. Zhang and S. Liu, Chin. Chem.
Lett., 2018, 29, 1560-1566.
33 X. Yang, Z. Zhao, X. Zhang and S. Liu, Sci. China Chem., 2018,
61, 787-791.
34 X. Zhao, F. Liu, Z. Zhao, H. Karoui, D. Bardelang, O. Ouari and
S. Liu, Org. Biomol. Chem., 2018, 16, 3809-3815.
35 S. Kuang, Z. Hu, H. Zhang, X. Zhang, F. Liang, Z. Zhao and S. Liu,
Chem. Commun., 2018, 54, 2169-2172.
36 W. Xu, M. Liu, M. C. Escaño, C. Redshaw, B. Bian, Y. Fan, Z. Tao
and X. Xiao, New J. Chem., 2019, 43, 7028-7034.
37 T. Du, W. Yuan, Z. Zhao and S. Liu, Chem. Commun., 2019, 55
,
3658-3661.
38 Y. Zhang, K. Lu, M. Liu, I. Karatchevtseva, Z. Tao and G. Wei,
Dalton Trans., 2020, 49, 404-410.
39 W. Gong, X. Yang, P. Y. Zavalij, L. Isaacs, Z. Zhao and S. Liu,
Chem. Eur. J., 2016, 22, 17612-17618.
40 G. Parvari, O. Reany and E. Keinan, Isr. J. Chem., 2011, 51, 646-
663.
41 H. Yuan, K. Wang, K. Yang, B. Liu and B. Zou, J. Phys. Chem.
Lett., 2014, 5, 2968-2973.
4 | J. Name., 2012, 00, 1-3
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Emission enhancement of cationic tetraphenylethylene derivativDeOsI: 10.1b03y9/C9NJ06209B
encapsulation in cucurbit[10]uril host in water
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Chang Liu, Yong Wu, Xie Han and Simin Liu*
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Encapsulation of cationic tetraphenylethylene guests in cucurbit[10]uril host in water results in
strong emission enhancement of these guests due to the host-guest interaction caused restriction
of intramolecular rotation.
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