7172019 c5cc04720j Tpe Pillar 2

httpslidepdfcomreaderfullc5cc04720j-tpe-pillar-2 15

This is an Accepted Manuscript which has been through the

Royal Society of Chemistry peer review process and has been

accepted for publication

Accepted Manuscripts are published online shortly after

acceptance before technical editing formatting and proof reading

Using this free service authors can make their results available

to the community in citable form before we publish the edited

article We will replace this Accepted Manuscript with the edited

and formatted Advance Article as soon as it is available

You can find more information about Accepted Manuscripts in the

Information for Authors

Please note that technical editing may introduce minor changes

to the text andor graphics which may alter content The journalrsquos

standard Terms amp Conditions and the Ethical guidelines still

apply In no event shall the Royal Society of Chemistry be held

responsible for any errors or omissions in this Accepted Manuscript

or any consequences arising from the use of any information it

contains

Accepted ManuscriptChemComm

wwwrscorgchemcomm

View Article OnlineView Journal

This article can be cited before page numbers have been issued to do this please use Q Zhou R Chen

H Jiang H Gu J Wu D Chen and J Zhang Chem Commun 2015 DOI 101039C5CC04720J

7172019 c5cc04720j Tpe Pillar 2

httpslidepdfcomreaderfullc5cc04720j-tpe-pillar-2 25

ChemComm

Cite this DOI 101039c0xx00000x

wwwrscorgxxxxxx

Dynamic Article Links

COMMUNICATION

This journal is copy The Royal Society of Chemistry [year] [journal] [year] [vol] 00ndash00 | 1

A pH-responsive fluorescent [5]Pseudorotaxane formed by self-assembly

of cationic water-soluble pillar[5]arenes and a tetraphenylethenederivative

Rener Chen1 Huajiang Jiang1 Haining Gu2 Qizhong Zhou1 Jiashou Wu1 Dingben Chen1 and Jie Zhang1

Received (in XXX XXX) Xth XXXXXXXXX 20XX Accepted Xth XXXXXXXXX 20XX5

DOI 101039c0xx00000x

A pH-responsive fluorescent [5]Pseudorotaxane formed by

self-assembly of cationic water-soluble pillar[5]arenes and a

tetraphenylethene derivative was reported

The design and preparation of interlocked threaded structures1 10

such as pseudorotaxanes rotaxanes catenanespolypseudorotaxanes polyrotaxanes and polycatenanes are hot

topics in chemistry due to not only their topological importance

but also their potential applications including molecular machines

and drug delivery materials Chemists have paid attention to15

making interlocked threaded structures for more than 50 years

not only because of their aesthetic beauty but also due to their

unique applications1 As one type of threaded structures the

pseudorotaxanes architecture is considered as a versatile platform

to construct functional artificial nanomachines Up to now the20

main hostndashguest recognition motifs used for fabrication of the

threaded structures are crown etherparaquat2 crown

ethersecondary ammonium salts3 cryptandparaquat4

cyclodextrinshydrophobic compounds5

calixareneparaquat6

and cucurbiturilparaquat or secondary ammonium salts7 These25

recognition motifs are mainly based on hydrogen bonding πndashπ

stacking charge transfer and hydrophilicndashhydrophobic

interactions Pillararenes are a new generation of macrocyclic

hosts for supramolecular chemistry after crown ethers

cyclodextrins calixarenes and cucurbiturils8 therefore the30

threaded structures formed by pillararene-based hostndashguest

recognition motifs are relatively less reported

Pseudorotaxanes may be viewed as prototypes of molecular

machines because of their reversible assemblydisassembly and

shuttling movement under external stimuli In some cases their35

photophysical properties are influenced along with the kinetic

process making them sensitive analytical tools in many areas

9

They can be used as chemical sensors when fluorescent signaling

elements are involved In 2001 a phenomenon of aggregation-

induced emission (AIE) was observed by Tang et al in some40

propeller-like molecules10 such as tetraphenylethene (TPE) and

hexaphenylsilole These luminogens are nonemissive in good

solvents but become highly luminescent in the aggregated state

Restriction of intramolecular rotation (RIR) in the aggregates has

been identified as the main cause for the AIE effect 10 In solution45

the active intramolecular rotation of the phenyl rings of AIE

molecules consumes energy However in the aggregated state

such motion is restricted which blocks the nonradiative pathway

and activates radiative decay10 Hostndashguest inclusion has attracted

considerable attention in recent years for its wide applications in50

nano-machines smart materials and so on11 The guest molecules

are accommodated inside the cavity of the host driven by physical

interactions Hence the hostndashguest inclusion can be used torestrict the motions of AIE molecules giving birth to fluorescent

pseudorotaxanes55

983123983141983148983142983085983105983155983155983141983149983138983148983161

983110983148983157983151983154983141983155983139983141983150983156 983118983151983150983142983148983157983151983154983141983155983139983141983150983156 Scheme 1 Chemical structures of 1 2 and 3 and cartoon representation of

the pH-controlled complexation between 1 and 3

Based on the above knowledge the utilization of the

recognition of cationic water-soluble pillar[5]arene 1 to TPE60

derivatives 2 can be a good method to prepare a fluorescent

pseudorotaxane (Scheme 1) Herein we report a simple strategy

based on the hostndashguest complexation between 1 and a TPE

derivative 2 to tune the emission behaviour of 2 in dilute aqueous

solution The spontaneously formed [5]pseudorotaxane units65

efficiently restricted the intramolecular rotation and the non-

radiative relaxation channel thereby resulting in the strong

emission of 2 in dilute solution10 Furthermore due to the pH-

responsiveness of the water-soluble pillar[5]arene-based hostndash

guest interactions the complex can be disassembled by adding70

acid releasing the captured TPE derivative and decreasing the

fluorescence intensity The complex can reassembled through the

addition of base recapturing TPE derivative and increasing the

fluorescence intensity

ge 1 of 4 ChemCommView Article Online

DOI 101039C5CC04720J

7172019 c5cc04720j Tpe Pillar 2

httpslidepdfcomreaderfullc5cc04720j-tpe-pillar-2 35

2 | Journal Name [year] [vol] 00ndash00 This journal is copy The Royal Society of Chemistry [year]

Fig 1 Partial 1H NMR spectra (500 MHz D2O 298 K) a) 300 mM 2 (b)

120 mM 1 and 300 mM 2 (c) 120 mM 1

1 and 2 were prepared according to the previous work12 Firstly1H NMR experiments were carried out to investigate the hostndash5

guest complexation between1 and

2 (Fig 1) The proton NMRspectra of 1 2 and a mixture of 120 mM 1 and 300 mM 2

showed that this complexation system is fast exchanged on the

proton NMR time scale Significant chemical shift changes were

observed for some protons on 1 and 2 after complexation (Fig 1)10

Upfield shifts were observed for H6ndashH8 of 2 Downfield shifts of

the protons H3 of 1 were observed From the 2D NOESY

spectrum (Fig 2) of a mixture of 120 mM 1 and 30 mM 2 in

D2O correlations were observed between protons H5 of 1 and

protons H6 and H7 of 2 suggesting the hostndashguest complexation15

between 1 and 2 Therefore we concluded the formation of the

inclusion complex between 1 and 2 in water

Fig 2 Partial NOESY spectrum (500 MHz D2O 298 K) of a mixture of

120 mM 1 and 300 mM 220

The proton NMR spectrum of an equimolar (300 mM) D2O

solution of 1 with 3 was also investigated and similar

complexation-induced chemical shift changes were observed (Fig

S1 ESIdagger) The ability of 1 to form a 1 1 complex with 3 was

assessed by 1H NMR titration of 3 into 1 in water and the25

association constant (K a) of 1sup3 was calculated to be in water

using a nonlinear curve-fitting analysis (Fig S2ndashS3 ESIdagger)

The DOSY NMR spectrum of an equimolar mixture of 1 and 2

in D2O at 298 K provides further evidence for the formation of

the threaded structure (Figure 3) It is evident from the spectrum30

that all the peaks correlated to the signals in the chemical shift

dimensions are in a horizontal line Thus all proton signals due to

the 1 and 2 displayed the same diffusion co-efficient supporting

their participation in a common aggregate

35

Fig 3 Partial DOSY spectrum (500 MHz D2O 298 K) of a mixture of

120 mM 1 and 300 mM 2

Furthermore we envisioned that 2 might exhibit very strong

emission upon addition of 1 because the intramolecular rotation

of the phenyl rings of 2 will be inhibited by the formation of the40

pseudorotaxane units The fluorescence properties of 200 microM 2

in the absence or presence of 1 in water were investigated (Fig

4a) The intramolecular rotation of phenyl rings of 2 may induce

the efficient nonradiative annihilation process and thus 2 is nearly

nonemissive in water However upon the addition of 1 the45

rotation of phenyl rings of 2 is restricted Therefore thefluorescence intensity increased remarkably The change of the

emission intensities nearly became constant when 320 microM 1 was

added and an approximate 15-fold fluorescence enhancement

was observed In addition when 2 was excited at 365 nm using a50

UV lamp in the presence of 320 microM 1 a strong cyan

fluorescence appeared further supporting the proposed

mechanism (Fig 4a)

It is well-known that anionic carboxylate groups and neutral

carboxylic groups can be interconverted by changing the55

solution pH thus the assembly and disassembly of the

complex 1sup2 can be controlled by acidbase treatment The

carboxylate groups of 2 can be changed to carboxylic groups

by adding aqueous HCl solution making 2 precipitate in

water and leading to the disassembly of the complex 1sup260

This was easily observed by naked eyes since white

precipitate appeared after aqueous HCl solution was added

(Fig 4b) Moreover the fluorescence of the aqueous solution

vanished and the precipitate showed strong fluorescence due

to the aggregation of neutralized 2 (Fig 4b) However after65

the addition of NaOH the white precipitate disappeared (Fig

4b) indicating the recovery of the complex Under this

condition the rotation of phenyl rings of 2 was restricted

PageChemCommView Article Online

DOI 101039C5CC04720J

7172019 c5cc04720j Tpe Pillar 2

httpslidepdfcomreaderfullc5cc04720j-tpe-pillar-2 45

This journal is copy The Royal Society of Chemistry [year] Journal Name [year] [vol] 00ndash00 | 3

again and the solution showed strong fluorescence (Fig 4b)

This process was also evidenced by the chemical shift changes

in the proton NMR spectra (Fig S4 ESIdagger)

Fig 4 a) Fluorescence spectral changes of 2 (200 microM) upon addition of 1 5

(000ndash160 equiv) in water (λ ex = 330 nm λ em = 490 nm slits 5 nm5

nm) b) Fluorescence spectral changes of the mixture of 200 microM 2 and

320 microM 1 upon the addition of aqueous HCl solution (600 microM) and

subsequent addition of NaOH (600 microM) The inset photographs show the

corresponding fluorescence changes upon excitation at 365 nm using a10

UV lamp at 298 K

In summary we prepared a fluorescent pseudorotaxane formed

by self-assembly of cationic water-soluble pillar[5]arenes and a

tetraphenylethene derivative The intramolecular rotation of the15

phenyl rings of 2 was hampered upon the addition of 1 so the

complex emits strong fluorescence in dilute solution Because of

the pH-responsiveness of the pillararene-based hostndashguest

interactions in water the fluorescence of the pseudorotaxane can

be tuned by changing the solution pH making it sensitive20

analytical tool in many areas We will also employ this strategy

of hostndashguest complexation induced emission in the constructionof responsive fluorescent materials in the future

This work was supported by the Natural Science25

Foundation of China (21172166 21402137 and 21302135)

Natural Science Foundation of Zhejiang Province

(LY14B020012 and LQ13B010001) China Postdoctoral

Science Foundation (No 2013M541456)

Notes and references30

1 Department of Chemistry Taizhou University Taizhou 318000 P R

China 2 Depatment of Chemistry Zhejiang University Hangzhou

310027 P R China

E-mail qizhongchoutzceducn (Q Zhou)

Fax +86-576-8866-0177 Tel +86-576-8866-0177 35

dagger Electronic Supplementary Information (ESI) available Synthetic

procedures characterizations Job plot and UV-vis data See DOI

101039c0xx00000x

1 (a) J E Green J W Choi A Boukai Y Bunimovich E Johnston-40

Halperin E Delonno Y Luo B A Sheriff K Xu Y S Shin H-R Tseng J F Stoddart and J R Heath Nature 2007 445 414 (b)M R Panman R Bodis D J Shaw B H Bakker A C NewtonE R Kay A M Brouwer W J Buma D A Leigh and SWoutersen Science 2010 328 1255 (c) Z-J Zhang H-Y Zhang45

H Wang and Y Liu Angew Chem Int Ed 2011 50 108342 Z Niu and H W Gibson Chem Rev 2009 109 60243 M Zhang D Xu X Yan J Chen S Dong B Zheng and F Huang

AngewChem Int Ed 2012 51 70114 F Huang H W Gibson W S Bryant D S Nagvekar and F R50

Fronczek J Am Chem Soc 2003 125 93675 H Ogino J Am Chem Soc 1981 103 13036 A Arduini R Ferdani A Pochini A Secchi and F Ugozzoli

Angew Chem Int Ed 2000 39 3453

7 H-J Kim W S Jeon Y H Ko and K Kim Proc Natl Acad Sci55

USA 2002 99 5007

8 (a) T Ogoshi S Kanai S Fujinami T A Yamagishi and Y

Nakamoto J Am Chem Soc 2008 130 5022 (b) D Cao Y KouJ Liang Z Chen L Wang and H Meier Angew Chem Int Ed

2009 48 9721 (c) Z Zhang Y Luo J Chen S Dong Y Yu Z60

Ma and F Huang Angew Chem Int Ed 2011 50 1397 (d) Q

Zhou H Jiang R Chen F Qiu G Dai and D Han Chem

Commun 2014 50 10658 (e) W Si L Chen X-B Hu G Tang

Z Chen J-L Hou and Z-T Li Angew Chem Int Ed 2011 50

12564 (f) M Xue Y Yang X Chi Z Zhang and F Huang Acc65

Chem Res 2012 45 1294 (g) G Yu C Han Z Zhang J Chen

X Yan B Zheng S Liu F Huang J Am Chem Soc 2012 134

8711 (h) C Li K Han J Li H Zhang J Ma X Shu Z Chen L

Weng and X Jia Org Lett 2012 14 42 (i) X-B Hu Z Chen G

Tang J-L Hou and Z-T Li J Am Chem Soc 2012 134 8384 (j)70

Y Yao M Xue J Chen M Zhang and F Huang J Am Chem

Soc 2012 134 15712 (k) C Li X Shu J Li J Fan Z Chen L

Weng and X Jia Org Lett 2012 14 4126 (l) G Yu Y Ma C

Han Y Yao G Tang Z Mao C Gao and F Huang J Am ChemSoc 2013 135 10310 (m) J-F Xu Y-Z Chen L-Z Wu C-H75

Tung and Q-Z Yang Org Lett 2013 15 6148 (n) L Chen W Si

L Zhang G Tang Z-T Li and J-L Hou J Am Chem Soc 2013

135 2152 (o) C Li Chem Commun 2014 50 12420 (p) Q

Zhou B Zhang D Han R Chen F Qiu J Wu and H Jiang Chem

Commun 2015 51 3124 (q) S Wang Y Wang Z Chen Y Lin80

L Weng K Han J Li X Jia and C Li Chem Commun 2015 51

3434 (r) H Chen J Fan X Hu J Ma S Wang J Li Y Yu X

Jia and C Li Chem Sci 2015 6 197

9 (a) Z-J Ding Y-M Zhang X Teng and Y Liu J Org Chem

2011 76 1910 (b) K-R Wang D-S Guo B-P Jiang and Y Liu85

Chem Commun 2012 48 3644

10 (a) 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 (b) Y Hong J W Y Lam and B Z Tang Chem

Commun 2009 433290

11 (a) C Li L Zhao J Li X Xia S Chen Q Zhang Y Yu and X

Jia Chem Commun 2010 46 9016 (b) M Ni X-Y Hu J Jiang

and L Wang Chem Commun 2010 50 1317 (c) T Ogoshi M

Hashizume T Yamagishi Y Nakamoto Chem Commun 2010

46 3708 (d) C Han Z Zhang G Yu and F Huang Chem95

Commun 2012 48 9876 (e) G Yu M Xue Z Zhang J Li C

Han and F Huang J Am Chem Soc 2012 134 13248 (f) G Yu

X Zhou Z Zhang C Han Z Mao C Gao and F Huang J Am

Chem Soc 2012 134 19489 (g) H Li D-X Chen Y-L Sun Y

B Zheng L-L Tan P S Weiss and Y-W Yang J Am Chem100

Soc 2013 135 1570 (l) S Dong B Zheng Y Yao C Han J

Yuan M Antonietti and F Huang Adv Mater 2013 25 6864

ge 3 of 4 ChemCommView Article Online

DOI 101039C5CC04720J

7172019 c5cc04720j Tpe Pillar 2

httpslidepdfcomreaderfullc5cc04720j-tpe-pillar-2 55

4 | Journal Name [year] [vol] 00ndash00 This journal is copy The Royal Society of Chemistry [year]

12 (a) Y Ma X Ji F Xiang X Chi C Han J He Z Abliz W Chen

and F Huang Chem Commun 2011 47 12340 (b) C Li T Wu

C Hong G Zhang and S Liu Angew Chem Int Ed 2012 51

455

5

Colour Graphic

983123983141983148983142983085983105983155983155983141983149983138983148983161

983110983148983157983151983154983141983155983139983141983150983156 983118983151983150983142983148983157983151983154983141983155983139983141983150983156

Text10

A pH-responsive fluorescent [5]Pseudorotaxane formed by self-

assembly of cationic water-soluble pillar[5]arenes and a

tetraphenylethene derivative was reported

PageChemCommView Article Online

DOI 101039C5CC04720J