A pillar[5]arene-based cyanide sensor bearing on a novel cyanide-induced self-assemble mechanism

Article abstract of DOI:10.1016/j.dyepig.2015.12.021

We have designed and synthesized a novel copillar[5]arene-based chemosensor, which employ 8-hydroxyquinoline group as a binding site and signal group. By a novel cyanide-induced self-assemble mechanism, the pillar[5]arene-based chemosensor shown high sens

Full text of DOI:10.1016/j.dyepig.2015.12.021

Dyes and Pigments 127 (2016) 59e66
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
A pillar[5]arene-based cyanide sensor bearing on a novel
cyanide-induced self-assemble mechanism
*
Xiaobin Cheng, Hui Li, Feng Zheng, Qi Lin, Youming Zhang, Hong Yao, Taibao Wei
Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of China, Key Laboratory of Polymer Materials of Gansu Province,
College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu, 730070, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 November 2015
Received in revised form
We have designed and synthesized a novel copillar[5]arene-based chemosensor, which employ 8-
hydroxyquinoline group as a binding site and signal group. By a novel cyanide-induced self-assemble
mechanism, the pillar[5]arene-based chemosensor shown high sensitivity and selectivity for cyanide in
aqueous media. When cyanide was added to the solution of the chemosensor, a strong chartreuse
fluorescence appeared. The detection limit of the fluorescent spectrum is 1.08 ꢀ 10 mol L for cyanide.
Moreover, test strips based on the sensor were fabricated, the chemosensor is a good cyanide test kits. In
addition, we made life applications of cyanide detected, the chemosensor is also could detect cyanide in
aqueous extracts from sprouting potatoes. It is worth mentioning that cyanide-induced self-assemble
mechanism is a novel strategy for the design of pillararene based chemosensor. Moreover, to the best of
our knowledge, it's the first example of pillararene based cyanide chemosensors.
21 December 2015
Accepted 24 December 2015
Available online 31 December 2015
ꢁ
8
ꢁ1
Keywords:
Pillararenes
Cyanide-induced
Self-assemble
Cyanide detection
Sprouting potatoes
Fluorescence
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
environmental processes [29e32]. Especially, cyanide is a virulent
anion causing poisoning in organism and the environment
Pillar[5]arenes [1], as a new type of macrocyclic hosts are linked
by methylene bridges at contrapuntal of 2, 5-dialkoxybenzene
rings, forming a distinctive rigidity pillar structure [2e6]. Func-
tional groups modified on pillararenes often gives rise to distinctive
properties that greatly stimulates the interest of chemists of this
area [7e10]. The idiographic structure and easy functionalization of
pillar[5]arenes carries them excellent capability to selectively bind
different types of guests and provide a beautiful terrace for the
construction of various receptors with different modifying groups
[33e35]. Industrially discharged cyanide are widespread in the
surroundings and do harm to biology by absorption through the
skin, gastrointestinal tract and lungs, bringing about loss of
awareness, vomiting, convulsion, and even death [36,37]. There-
fore, highly selective sensors for cyanide have been received
widespread attention for their applicability to circumstance and
the pathological imaging of the anions [38]. Among the less con-
ventional methods designed for sensing cyanide ions, those which
exploit chemical reactions that produce fluorometric and colori-
metric responses have considered to be the most ease and efficient
methods to sensing cyanide owing to their briefness, high sensi-
tivity and cherished nature [39e41].
[11,12]. Despite excessive reports on complexation of organic spe-
cies, the use of hostꢁguest interactions involving pillararenes and
inorganic anions remains very limited [13,14]. Given this, Cao re-
ported the design and preparation of a novel copillar[5]arene
Furthermore, processes like aggregation induced excitation or
aggregation induced excitation strengthen have been applied in the
development of specific fluorescent sensors [42,43]. The polymer-
ization course assisted such molecules to bind efficiently through
[15e18] and its application in anion-binding. So far, only a few
publications involve copillararene [19e24]. It is worth mentioning
that recognition of cyanide by pillararene as receptors has been
unexplored to date [25e28].
pep stacking interaction, which eventually discouraged the non-
The recognition of anions have received concern by many
chemists for their important roles in biological, industrial, and
radiative inactivation channel through stinted within the molecule
rotations [44,45]. This can explain the strengthened fluorescent
excitation in the polymerization, In view of this, we thought of the
quinoline compounds. As one of these, 8-hydroxyquinoline is one
of the most important complexing agent for ions in its fluorescence
upon ions binding [46e48]. Therefore, 8-hydroxyquinoline has
*
Corresponding author. Tel./fax: þ86 9317973191.
E-mail address: weitaibao@126.com (T. Wei).
http://dx.doi.org/10.1016/j.dyepig.2015.12.021
143-7208/© 2016 Elsevier Ltd. All rights reserved.
0

60
X. Cheng et al. / Dyes and Pigments 127 (2016) 59e66
been used to construct highly sensitive fluorescent sensors for ions
of important biological and environmental significance [49e51],
we envisaged that this shall be probable through introducing an
efficient enhancing pathway in the 8-hydroxyquinoline ethers that
can be raised its fluorescence characteristics upon anions complex
2 4
organic layer was dried over anhydrous Na SO and evaporated to
afford the crude product, which was isolated by flash column
chromatography using petroleum ether/ethyl acetate (50:1). The
fractions containing the product were combined and concentrated
under vacuum to give a kind of copillar[5]arene (1.5 g, 30%) as a
ꢂ
[52]. As a consequence, we envisaged that tethering quinoline
white solid, m.p. 116e119 C. The proton NMR spectrum of a
1
section, which are recognized as an excellent fluorophores for
anion sensors. With our continued interest in recognition of anions,
we report herein on the design and synthesis of a novel copillar[5]
arene, which showed a fluorescent sensing for cyanide and pro-
posed cyanide-induced self-assemble mechanism. Up until now,
pillararene-based fluorescent sensors have been developed only for
organic and neutral guests, and no literature on functionalized
pillararenes designed for fluorescent sensors towards cyanide has
been published and this is the first example of selective fluorescent
recognition towards cyanide in the field of pillararene chemistry.
copillar[5]arene. H NMR (600 MHz, CDCl
3
)
d
6.93e6.63 (m, 10H),
3.89 (d, J ¼ 6.5 Hz, 1H), 3.83 (t, J ¼ 6.0 Hz, 1H), 3.81e3.75 (m, 10H),
3.75e3.55 (s, 27H), 3.42 (d, J ¼ 130.4 Hz, 2H), 1.92 (s, 1H), 1.81 (s,
13
3
1H), 1.25 (s, 2H). C NMR (151 MHz, CDCl ) d 150.50 (s), 128.17 (d,
J ¼ 5.5 Hz), 113.59 (s), 67.19 (s), 55.63 (d, J ¼ 20.2 Hz), 39.58 (s),
33.45 (s), 31.77 (s), 30.74e30.25 (m), 29.42 (d, J ¼ 6.9 Hz), 28.39 (s).
2.2.3. Compound PQ5
A copillar[5]arene 1 (0.71 g, 1 mmol), and 8-hydroxyquinoline
(0.073 g, 1 mmol) was dissolved in THF (60 mL). KOH (0.056,
1
mmol) was added and the reaction mixture was stirred at room
temperature for 3 days. The solvent was evaporated and the residue
was dissolved in CH Cl . The resultant solution was washed with
O, after the solid was filtered afforded a white solid PQ5 (0.70 g,
2
. Experimental
2
2
2.1. Materials and instruments
H
2
9
ꢂ
1
0%), mp. 108e112 C. H NMR (600 MHz, DMSO-d
6
) d 8.94 (s, 1H),
All reagents for synthesis were of analytical grade, commercially
7.58 (s, 1H), 6.85e6.81 (m, 14H), 4.37 (d, J ¼ 48.6 Hz, 4H), 3.71 (s,
13
and were used without further purification. All the anions were
added in the form of tetrabutylammonium (TBA) salts. Which were
purchased from SigmaeAldrich Chemical, stored in a vacuum
desiccator. Melting points were measured on an X-4 digital melting
point apparatus and were uncorrected. UVevis spectra were
recorded on a Shimadzu UV-2550 spectrometer. Fluorescence
27H), 1.95 (d, J ¼ 82.4 Hz, 10H), 1.80 (s, 4H). C NMR (151 MHz,
CDCl 201.54, 150.52, 150.48, 150.46, 150.41, 150.37, 149.56,
3
) d
128.46, 128.30, 128.26, 128.19, 114.30, 113.59, 113.47, 113.44, 113.36,
98.41, 68.01, 67.37, 67.26, 55.75, 55.65, 55.61, 55.52, 55.50, 55.49,
þ
55.47, 55.45, 55.41, 28.45, 27.77. ESI-MS m/z: [M þ H] , calcd for
936; found 936.4.
1
spectra were recorded on a Shimadzu RF-5310. H NMR spectra
were recorded on a Mercury-600BB spectrometer at 600 MHz and
2.2.4. Compound 2
13
C NMR spectra were recorded on a Mercury-600BB spectrometer
at 150 MHz with DMSO-d as solvent. Chemical shifts are reported
in ppm downfield from tetramethylsilane (TMS, scale with solvent
1-(4-Bromobutoxyl)-4-methoxybenzene (1.32 g, 5 mmol), and
8-hydroxyquinoline (0.726 g, 5 mmol) was dissolved in THF
(80 mL). KOH (0.28, 5 mmol) was added and the reaction mixture
was stirred at room temperature for 2 days. After the solvent was
evaporated column chromatography (silica gel; petroleum ether:-
6
d
resonances as internal standards). Mass spectra were performed on
a Bruker Esquire 3000 plus mass spectrometer (Bruker-Franzen
Analytik GmbH Bremen, Germany) equipped with ESI interface and
ion trap analyzer.
1
ethyl acetate ¼ 20:1) afforded a white solid (1.68 g, 82%). H NMR
(400 MHz, CDCl
3
)
d
9.01e8.95 (m, 1H), 8.16 (d, J ¼ 8.3 Hz, 1H),
7
.51e7.39 (m, 3H), 7.11 (d, J ¼ 7.5 Hz, 1H), 6.89e6.83 (m, 4H), 4.37 (t,
2
2
2
.2. Synthesis
J ¼ 6.6 Hz, 2H), 4.07 (t, J ¼ 6.2 Hz, 2H), 3.80 (s, 3H), 2.27e2.21 (m,
13
3
2H), 2.11e2.04 (m, 2H). C NMR (151 MHz, CDCl ) d 154.74 (s),
.2.1. 1-(4-Bromobutoxyl)-4-methoxybenzene
In a 500 mL round-bottom flask, 4-methoxyphenol (2.48 g,
0 mmol), K CO (8.4 g, 60 mmol), KI (3.3 g, 20 mmol), 1, 4-
2 3
153.71 (s), 153.13 (s), 149.28 (s), 140.41 (s), 135.86 (s), 129.50 (s),
126.65 (s), 121.51 (s), 119.50 (s), 115.43 (s), 114.60 (s), 108.71 (s),
68.53 (s), 68.15 (s), 55.72 (s), 26.18 (s), 25.77 (s).
dibromobutane (17.3 g, 80 mmol) and acetone (400 mL) were
added. The reaction mixture was stirred at reflux for 2 days. After
the solid was filtered off, the solvent was evaporated and the
2.2.5. 1, 4-Bis (4-bromobutoxyl) benzene
2 3
Hydroquinone (2.3 g, 20.0 mmol), K CO (16.6 g, 120 mmol), KI
residue was dissolved in CH
2
Cl
2
. Column chromatography (silica
(6.6 g, 40 mmol), 1, 4-dibromobutane (34.6 g, 160 mmol) and
gel; petroleum ether:ethyl acetate ¼ 50:1) afforded a white solid
acetone (400.0 mL) were added in a 500 mL round-bottom flask
ꢂ
1
ꢂ
(
3.4 g, 65%), m.p.45 C. H NMR (600 MHz, CDCl
3
)
d
6.83 (s, 4H),
stirred at 60 C under N
2
. The reaction mixture was stirred at reflux
3
2
d
.94 (t, J ¼ 6.1 Hz, 2H), 3.83e3.69 (s, 3H), 3.48 (t, J ¼ 6.7 Hz, 2H),
for 2 days. After the solid was filtered off, the solvent was evapo-
13
.11e2.00 (m, 2H), 1.97e1.84 (m, 2H). C NMR (151 MHz, CDCl
3
)
rated and the residue was dissolved in CH
2
Cl
2
. Column chroma-
¼ 10:1) afforded a
6.83 (d,
J ¼ 0.8 Hz, 4H), 3.96 (t, J ¼ 6.0 Hz, 4H), 3.52e3.25 (m, 4H), 2.10e1.88
153.83 (s), 153.00 (s), 115.42 (d, J ¼ 4.8 Hz), 114.64 (d, J ¼ 2.5 Hz),
tography (silica gel; petroleum ether:CH Cl
white solid (3.0 g, 40%). H NMR (600 MHz, CDCl ) d
3
2
2
1
6
7.46 (s), 55.73 (s), 33.52 (s), 30.24 (d, J ¼ 7.2 Hz), 29.51 (s), 28.01
(
s), 26.11 (s), 6.49 (s).
13
(
3
m, 8H). C NMR (151 MHz, CDCl ) d 153.07 (s), 115.40 (s), 67.35 (d,
2
.2.2. Copillar[5]arene 1
-(4-Bromobutoxyl)-4-methoxybenzene (1.32 g, 5 mmol) and 1,
-dimethoxybenzene (2.76 g, 20 mmol) in 1, 2-dichloroethane
J ¼ 30.2 Hz), 33.52 (s), 30.25 (s), 30.21 (s), 29.50 (s), 28.00 (s).
1
4
2.2.6. Compound 3
(
80 mL), paraformaldehyde (0.75 g, 25 mmol) was added. Then,
1, 4-Bis (4-bromobutoxyl) benzene (1.9 g, 5 mmol), and 8-
hydroxyquinoline (1.452 g, 10 mmol) was dissolved in THF (80 mL).
KOH (0.56, 10 mmol) was added and the reaction mixture was stir-
red at room temperature for 3 days. After the solvent was evaporated
boron trifluoride diethyl etherate (3.2 mL, 25 mmol) was added to
the solution and the mixture was stirred at room temperature for
1
h. The solution was poured into methanol and the resulting
precipitate was collected by filtration. The solid was dissolved in
CHCl (150 mL) and the insoluble part was filtered off. The resulting
solid dissolved in CHCl and washed twice with H O (100 mL). The
column chromatography (silica gel; petroleum ether:ethyl acetate
1
3
¼ 10:1) afforded a white solid (1.0 g, 30%). H NMR (400 MHz, CDCl
3
)
3
2
d
8.95 (d, J ¼ 2.6 Hz, 2H), 8.13 (d, J ¼ 8.3 Hz, 2H), 7.42 (d, J ¼ 16.9,13.2,

X. Cheng et al. / Dyes and Pigments 127 (2016) 59e66
61
Scheme 1. Synthesis of the copillar[5]arene PQ5 linked 8-hydroxyquinoline and the chemical structure of the acyclic monomeric analog 2 and 3.
8
.0 Hz, 6H), 7.08 (d, J ¼ 7.5 Hz, 2H), 6.82 (s, 4H), 4.33 (t, J ¼ 6.7 Hz,
approximate 3.5-fold fluorescence enhancement was observed
13
4
H), 4.03 (t, J ¼ 6.2 Hz, 4H), 2.26e2.17 (m, 4H), 2.09e1.99 (m, 4H).
154.75 (s), 153.10 (s), 149.29 (s), 140.44 (s),
35.83 (s), 129.49 (s), 126.64 (s), 121.51 (s), 119.49 (s), 115.40 (s),
08.70 (s), 68.53 (s), 68.13 (s), 26.18 (s), 25.77 (s).
C
(Fig. 1). In addition, a strong chartreuse fluorescence appeared
(Fig. 1 Inset). From here, We are be easily detected cyanide ions
through the sensor PQ5, cyanide was added dropwise towards the
sensor PQ5, by color of the solution transformation from colorless
to yellowegreen under the UV lamp. The fluorescence spectral
3
NMR (151 MHz, CDCl ) d
1
1
ꢁ
properties of sensor PQ5 with CN were also carried out in the
3
. Results and discussion
solution of DMSO/H
Fig. S14), which we got the same experiment phenomenon with
the above situation.
To validate the selectivity of sensor PQ5, the same tests were
2
O (0.01 M HEPES buffer, pH ¼ 7.24, 80% DMSO)
(
3.1. Design, synthesis and characterization
In view of this, and as a part of our research interest in pillar-
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
applied using F , Cl , Br , I , AcO , H PO , HSO4 , ClO4 , CN and
2
4
arenes chemistry and molecular recognition [53e62], we designed
and synthesized a novel copillar[5]arene-based anion receptor PQ5
linked 8-hydroxyquinoline at one sites (Scheme 1). The key pre-
cursor 1 was achieved by only a one-step condensation reaction of
ꢁ
SCN anions, and only CN have significant changes in the fluo-
rescence spectrum of the sensor (Fig. 2), and none of those other
compound
1-(4-bromobutoxyl)-4-methoxybenzene,
1,
4-
dimethoxybenzene and para-formaldehyde under Lewis acid
catalyzed conditions to obtain. Subsequent etherification reaction
of the resulting 1 with 8-hydroxyquinoline in THF at room tem-
perature, which was further applied NaOH to obtain the desired
compound PQ5 in a 90% isolated yield (Scheme S1). The acyclic
monomeric pattern 2 and 3 were also prepared as a control for
comparison (Schemes S2 and S3). The target molecules and in-
termediates were characterized by 1H NMR spectrum, C NMR
spectrum and ESI-MS (Figs. S1eS13).
13
2
3.2. Fluorescence properties in DMSO/H O (8:2, v/v) solution
ꢁ
In order to investigate the CN recognition abilities of the sensor
2
PQ5 in DMSO/H O (8:2, v/v) solution, a series of hosteguest
recognition experiments were carried out. The recognition profiles
ꢁ
ꢁ
ꢁ ꢁ
of the sensor PQ5 toward various anions (including F , Cl , Br , I ,
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
ꢁ
AcO , H PO , HSO4 , ClO4 , CN and SCN ) were ready to
2
4
research using fluorescence spectroscopy. In the fluorescence
spectrum, the maximum emission of PQ5 appeared at 456 nm in
DMSO/H
2
O (8:2, v/v) while excited at
l
ex ¼ 360 nm. When
Fig. 1. Fluorescence spectral response of PQ5 (1.0 mM) in DMSO/H
2
O (8:2, v/v) upon
ex ¼ 360 nm). Inset: photograph of PQ5 (1.0 mM) upon
addition of 2.0 equiv. of CN , which was taken under a UVelamp (365 nm).
ꢁ
2
.0 equiv. of CN was added to the solution of the sensor PQ5, the
e
addition of 2.0 equiv. of CN
(l
e
fluorescence emission band was red-shifted to 518 nm, and an

62
X. Cheng et al. / Dyes and Pigments 127 (2016) 59e66
ꢁ
Fig. 4. The Job's plot examined between CN and PQ5, indicating the 1:2 stoichiom-
etry, which was carried out by fluorescence spectra (
ex ¼ 360 nm).
l
Fig. 2. Fluorescence emission data for PQ5 and each of the various anions as the
tetrabutylammonium salts, in the DMSO/H
2
O (v/v ¼ 8:2) solution. Inset: color changes
ꢁ
ꢁ ꢁ ꢁ ꢁ ꢁ ꢁ
ꢁ
observed for PQ5 upon the addition of F , Cl , Br , I , AcO , H2PO4 , HSO4 , ClO4
,
(
1
Fig. S15), which is far lower than the WHO guideline of
.9 mmol L cyanide. Besides, while the amount of CN ion is
ꢁ
ꢁ
CN and SCN in DMSO/H
2
O (v/v ¼ 8:2) solution on a spot plate. (For interpretation
ꢁ1
ꢁ
of the references to color in this figure legend, the reader is referred to the web version
beyond 2.0 equiv., the emission at 518 nm tends to saturation,
which reveals the possible formation of a 2:1 complex between
PQ5 and CN (Fig. S16).
of this article.)
ꢁ
anions induced any significant changes in the fluorescent spectrum
of the sensor. Upon addition of CN ions, the band was red-shifted
In order to quantify the complexation ratio between PQ5 and
CN , the fluorescence of Job's plot measurement (Fig. 4) was
ꢁ
ꢁ
accompanied with its absorption significantly enhanced at 518 nm.
The apparent color change from colorless to chartreuse could be
distinguished under the UV lamp.
conducted by varying the concentration of both the sensor and
ꢁ
the CN . The maximum point appears at the mole fraction of
ꢁ
0.33 which indicates that PQ5 and CN were formed a 2:1
So as to investigate the binding properties of the receptor PQ5
complex.
ꢁ
ꢁ
towards CN ion, we implemented of the fluorescence titration of
The selectivity of PQ5 to CN was also examined over a wide
range of pH values as shown in Fig. 5. The detection of CN can
work well in the pH range of 3.0e14.0 in DMSO/H O (8:2, v/v).
2
To explore the utility of sensor PQ5 as an ion-selective che-
mosensor for CN , competitive experiments were carried out in
the presence of 2.0 equiv. of CN and 2.0 equiv. of various other
ions (anions: F , Cl , Br , I , AcO , H PO , HSO , ClO4 , SCN
ꢁ
ꢁ
PQ5 with CN in DMSO/H
2
O (8:2, v/v) solution. The emission
ꢁ
spectral variation of PQ5 upon gradual addition of CN ion is shown
in Fig. 3. In the fluorescence spectrum, upon addition of increasing
ꢁ
ꢁ
amounts of CN ions (0e2.0 equiv.) to the solution of PQ5 in DMSO/
ꢁ
H
2
O (8:2, v/v), the fluorescence emission at 456 nm is gradually
red-shifted to 518 nm, directly leading to a strong chartreuse
ꢁ
3
ꢁ
ꢁ
ꢁ
þ
ꢁ
ꢁ
ꢁ
2þ
ꢁ
2þ
ꢁ
2 4 4
þ
2þ
2þ
2þ
2þ
2þ
2þ
emission. The detection limit of the fluorescent spectrum changes
and cations: Fe , Hg , Ag , Ca , Cu , Zn , Cd , Ni , Pb
,
/S is 1.08 ꢀ 10ꢁ mol L for CN
8
ꢁ1
ꢁ
2þ
3þ
calculated on the basis of 3
s
2
Co , Cr , Mg ) in DMSO/H O (8:2, v/v). The results of these
Fig. 3. Fluorescence spectra of PQ5 (0.4
m
M) in the presence of different concentration
ꢁ
of CN in DMSO/H
2
ꢁ
O (8:2, v/v) solution. Inset: color changes observed for PQ5 upon
ꢁ
the addition of CN . (For interpretation of the references to color in this figure legend,
Fig. 5. Influence of pH on the fluorescence of PQ5 (1.0 mM) in response to CN
(2.0 equiv.) in DMSOeH O (8:2, v/v) solution.
the reader is referred to the web version of this article.)
2

X. Cheng et al. / Dyes and Pigments 127 (2016) 59e66
63
ꢁ
CN as shown in Fig. 7, all the signals related to the protons on
PQ5 shifted downfield obviously except that related to H
b
, the
) showed obvious
pep stacking interactions
1
H NMR signals of quinoline ring protons (H
upfield shifts. Which indicate that
b
between two molecules of quinoline ring and quinoline ring
between pillar structures. When increasing the amount of cya-
nide, the chemical shift of all the protons are no longer changed
(
Fig. S17). Owing to sensor PQ5 could take place an intra-
molecular rotation, the sensor is in the twisted intramolecular
charge transfer state and show very weak fluorescence. Upon
ꢁ
the gradual addition of CN , the sensor PQ5 formed multiple
ꢁ
hydrogen bonds with CN , which confined the intramolecular
rotation of sensor PQ5, due to the intramolecular rotation was
astrict by the multiple hydrogen bonds, the sensor shown a
strong fluorescence emission at 518 nm.
The phenomenon that the conformation of PQ5 changed from
the columnar structure into the packing construction when PQ5
ꢁ
interacted with CN was further validated by NOESY NMR spec-
troscopy. The NOESY spectrum (Fig. 8): strong correlations were
Fig. 6. Fluorescence intensities of PQ5 (1.0 mM) in the presence of 2.0 equiv. of various
observed between the quinoline ring protons H
aliphatic hydrocarbons protons H as well as the bridging methy-
lene protons H of the pillar[5]arene unit, suggesting that the
a f
eH and the
ꢁ
ions containing 2.0 equiv. of CN in DMSO/H
2
O (v/v ¼ 8:2) solution ( ¼ 518 nm).
l
g
i
quinoline ring was portion penetrate into the cavity of the pillar[5]
arene. Furthermore, strong correlations were also observed be-
studies have revealed that these competing ions exerted little
influence on the fluorescence emission spectra of sensor PQ5 with
tween the H
h
of the alkyl chain protons and quinoline ring protons
ꢁ
CN , which further indicated that PQ5 has specific selectivity to
H
d
eH . Thus, the current measurements clearly pointed out that
f
ꢁ
CN (Fig. 6).
the formation of the alkyl chain rotational contraction, evidence
that quinoline ring and pillar structure have strong interactions.
Meanwhile, indicated that the distances between the quinoline ring
extreme closer on average, supporting their participation in a
common aggregate.
3.3. The sensing mechanism
The proposed mechanism was also confirmed by 1H NMR
1
spectrum measurements.
H
NMR spectrum displayed the
Meanwhile, the signal of the hydrogen atoms of quinoline ring
chemical shift changes of PQ5 upon the addition of 2.0 equiv.
protons (H
b
) showed a significant upfield shift and the signal of
Fig. 7. 1H NMR spectra (400 MHz, 0.4 mL CDCl
and 0.1 mL DMSO-d
(4:1 v/v).) of free PQ5 and in the presence of CN .
ꢁ
3
6

64
X. Cheng et al. / Dyes and Pigments 127 (2016) 59e66
ꢁ
3 6
Fig. 8. 2D NOESY spectrum of PQ5 in 0.4 mL CDCl and 0.1 mL DMSO-d (4:1 v/v) at 298 K after addition of 0.5 equiv. of CN .
alkyl chain protons (H
indicating that the electrostatic interaction between the two
molecules of PQ5 and the stacking between the quinoline
h
) showed a significant downfield shift,
of PQ5, but they both only shows very poor fluorescence under the
same conditions (Figs. 10 and 11), highlighting the importance of
the preorganization of the pillar[5]arene platform on the recog-
nition of CN via the cooperative coordination in the supramo-
lecular complex.
pep
ꢁ
ring of pillar structure. More importantly, sensor PQ5 is most
ꢁ
likely to band with CN via its N atoms on pyridine and alkyl chain
protons (H
and alkyl chain protons (H
rings and also two five-membered ring formed between cyanide
and alkyl chain protons (H ) as well as (H ) on PQ5 (Fig. S18), the
h
), and the hydrogen bond between pyridine N atoms
To further investigate the practical application of chemosensor
PQ5, test strips were fabricated by immersing filter papers into
h
) on PQ5 formed two six-membered
ꢁ
3
DMSO/H
2
O (v/v ¼ 8:2) solution of PQ5 (2 ꢀ 10 M) and then
h
a
drying them in air. The test strips containing PQ5 were utilized to
sense CN . As shown in Fig. 12, when CN were added on the test
ꢁ
ꢁ
molecules formed a supramolecular system by means of self-
ꢁ
ꢁ
ꢁ
assemble when CN is added (Fig. 9). In sharp contrast, acyclic
strips, an obvious color change was observed with CN solution
monomeric analog 2 and 3 even at a identical concentration with
the linked 8-hydroxyquinoline functionality being equal to that
Fig. 10. Fluorescence spectral response of 2 (1.0 mM) in DMSO/H
2
O (8:2, v/v) upon
ex ¼ 360 nm). Inset: photograph of 2 (1.0 mM) upon
addition of 2.0 equiv. of CN , which was taken under a UV-lamp (365 nm).
e
addition of 2.0 equiv. of CN
(l
ꢁ
e
Fig. 9. The proposed structures of PQ5 for CN anions.

X. Cheng et al. / Dyes and Pigments 127 (2016) 59e66
65
Fig. 13. Fluorescence emission data for the sensor PQ5 to detect cyanide in sprouting
potato. Inset: color changes observed for PQ5 upon the addition of cyanide-
containing under the UV lamp and photograph of sprouting potato. (For interpre-
tation of the references to color in this figure legend, the reader is referred to the web
version of this article.)
2
Fig. 11. Fluorescence spectral response of 3 (1.0 mM) in DMSO/H O (8:2, v/v) upon
e
addition of 2.0 equiv. of CN
(
l
ex ¼ 360 nm). Inset: photograph of 3 (1.0 mM) upon
e
addition of 2.0 equiv. of CN , which was taken under a UV-lamp (365 nm).
under a UV lamp. Therefore, the test strips could conveniently
detect CN in water solutions.
ꢁ
ꢁ
CN test kits and the sensor PQ5 is a good way to detect cyanide
We also investigated the practical utilities of the sense in our
daily life, we selected the sprouting potatoes to carry out the below
experiment. The sprouting potato (150 g) was first mashed before
being soaked in water (200 mL) for 4 days until the extract became
muddy. The mixture was filtered and the filtrate was washed with
aqueous extracts from sprouting potatoes. The work shown here
not only presents the fact of using recognition towards cyanide, but
more importantly, the cyanide-induced self-assemble mechanism
reported here is a novel strategy for the design of pillararene based
chemosensors.
100 mmol/L NaOH solution (100 mL) to get the cyanide-containing
solution. As shown in Fig. 13, upon the addition cyanide-containing
solution into PQ5, An obvious color change from colorless to yellow
was observed under the UV lamp.
Acknowledgment
This work was supported by the National Natural Science
Foundation of China (NSFC) (no. 21574104; 21161018; 21262032),
the Natural Science Foundation of Gansu Province (1308RJZA221)
and the Program for Changjiang Scholars and Innovative Research
Team in University of Ministry of Education of China (IRT1177).
4
. Conclusions
In conclusion, we have designed and synthesized a novel
copillar[5]arene PQ5. It can sense cyanide by a novel cyanide-
induced self-assemble mechanism with high selectivity and
sensitivity. The detection limit of the fluorescent spectrum is
Appendix A. Supplementary data
ꢁ
8
ꢁ1
ꢁ
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.dyepig.2015.12.021.
1.08 ꢀ 10 mol L for CN . Moreover, test strips based on the
sensor were fabricated, which served as convenient and efficient
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