Perylenebisimide-based colorimetric and fluorescent sensors for selective detection of anions

Article abstract of DOI:10.2174/157017810791824928

A new type of perylenebisimide-based imidazolium chemosensor was synthesized for selective recognition of anions. Imidazolium-anchored receptor PBI-1 showed high binding affinity to F-due to the role of the phenolic hydroxyl group as an additional binding site. The hydroxyl-protected receptor PBI-2 could serve as highly selective and sensitive colorimetric and fluorometric sensor for H2PO4 -. The study indicated that the C2-H of the imidazolium ring played an essential role in the anion recognition via synergistic effects of multiple hydrogen-bonding and electrostatic interactions. In addition, it was noteworthy that the phenolic hydroxy of the receptor was not indispensable for binding H2PO4 -, but very pivotal for binding F-.

Full text of DOI:10.2174/157017810791824928

Letters in Organic Chemistry, 2010, 7, 495-501
495
Perylenebisimide-Based Colorimetric and Fluorescent Sensors for
Selective Detection of Anions
Peng Guo, Xiaoyu Su and Jingbo Lan*
Key Laboratory of Green Chemistry and Technology of Ministry of Education, College of Chemistry, Sichuan
University, Chengdu 610064, People’s Republic of China
Received April 08, 2010: Revised May 10, 2010: Accepted May 12, 2010
Abstract: A new type of perylenebisimide-based imidazolium chemosensor was synthesized for selective recognition of
anions. Imidazolium-anchored receptor PBI-1 showed high binding affinity to F- due to the role of the phenolic hydroxyl
group as an additional binding site. The hydroxyl-protected receptor PBI-2 could serve as highly selective and sensitive
-
colorimetric and fluorometric sensor for H2PO4 . The study indicated that the C2-H of the imidazolium ring played an
essential role in the anion recognition via synergistic effects of multiple hydrogen-bonding and electrostatic interactions.
-
In addition, it was noteworthy that the phenolic hydroxy of the receptor was not indispensable for binding H2PO4 , but
very pivotal for binding F-.
Keywords: Anion recognition, colorimetric and fluorometric detection, hydrogen bonds, imidazolium chemosensor,
perylenebisimide, phenolic hydroxyl.
INTRODUCTION
colorimetric probes for the recognition of anions [7].
Perylene-3,4:9,10-tetracarboxylic acid bisimide (PBI) is a
particularly promising class of organic dyes that exhibit
unique photophysical and photochemical properties [8].
Because their fluorescence spectra between 500~650 nm are
very suitable for both colorimetric and fluorimetric detection
[9], PBI-based chemosensors have been designed and widely
applied for the optical detection of anions, cations and
biological molecules in recent years [10]. However, there are
no PBI-attached chemosensors by incorporating the
imidazolium units designed for the anion recognition so far.
On the basis of the above considerations and in continuation
of our ongoing interest in the development of imidazolium-
based supramolecular chemistry [11], we herein present the
synthesis of PBI-based imidazolium chemosensors PBI-1
and PBI-2 and the spectroscopic investigations toward
different anions. To further illustrate the importance of the
phenolic hydroxy of the receptor for binding F-, an analogue
without imidazolium group PBI-3 was synthesized for the
comparative experiment.
The development of synthetic receptors capable of
recognizing anions has gained extensive interest in the past
few decades due to their practical importance in many
chemical, biological, medical, and environmental processes
[1]. It is well known that the positively charged imidazolium
group is a good binding subunit for anions through
synergistic effects of unconventional hydrogen bonds and
cation–anion interactions [2]. As a new class of promising
building blocks to create supramolecular systems,
imidazolium group has been utilized for the design and
synthesis of receptors for anion recognition by forming (C–
H)+···X- hydrogen bonds between the imidazolium ring and
the guest anion [3]. Lots of X-Ray data and NMR study
results have also unequivocally proved the existence of the
unconventional (C–H)+···X- type hydrogen bonds [4].
Among imidazolium-based sensors reported for anion
recognition, the selective chemosensors for H2PO4 or F-
-
have attracted more interests [3,5]. Even though great
achievement in the field of anion chemosensors has been
obtained, there is still a demand to develop new indicators
with improved properties, especially colorimetric and
fluorescent sensors with specific selectivity toward F- or
RESULTS AND DISCUSSION
-
Perylenebisimide compounds PBI-1 and PBI-2 function-
alized with imidazolium units were successfully synthesized
by a two-step reaction using N-octadecyl-1,6,7,12-tetra(4-
H2PO4 over other competitive anions. However, to the best
of our knowledge, there were only a few examples using
imidazolium-based colorimetric sensors for F- or H2PO4 [6].
-
tert-butylphenoxy)
perylene-3,4:9,10-tetracarboxylic-3,4-
Therefore, the design and construction of colorimetric and
fluorescent sensors based on imidazolium for highly
anhydride-9,10-imide (7) as starting material. As demon-
strated in Scheme 1, 7 reacted with 2,6-bis(imidazolyl-
methyl)-4-aminophenol (2) and 3,5-bis(imidazolylmethyl)-4-
methoxyaniline (6) in toluene afforded PBI-based
intermediates 8 and 9, respectively. Quaternization reactions
of 8 and 9 with MeI were easy to accomplish in solvent-free
conditions, and then followed by anion exchange of I- with
selective recognizing F- or H2PO4 is very significant.
-
Colorimetric methods can be convenient in practical
applications without the aid of any advanced instruments.
Recently, considerable efforts have been made to develop
-
PF6 affording the corresponding imidazolium receptors PBI-
*Address correspondence to this author at the College of Chemistry,
Sichuan University, Chengdu 610064, P. R. China; Tel: 86-28-85412285;
Fax: 86-28-85412203; E-mail: jingbolan@scu.edu.cn
1 and PBI-2. PBI-3 was synthesized by a straightforward
reaction of 7 with 4-aminophenol.
1570-1786/10 $55.00+.00
© 2010 Bentham Science Publishers Ltd.

496 Letters in Organic Chemistry, 2010, Vol. 7, No. 6
Guo et al.
N
N
N
N
N
OH
N
N
OH
N
H2, Pd/C
MeOH
Imidazole
1,4-dixoane
NO2
NH2
OH
OH
OH
1
2
N
N
N
N
NO2
Cl
O
Cl
N
O
N
OH
O
OH
N
O
N
DMF
SOCl2
Imidazole
NaH, THF
H2, Pd/C
MeOH
MeI, K2CO3
NO2
NO2
NO2
NH2
4
3
5
6
N
N
R
O
N
NH2
R' R'
N
N
O
N
O
O
N
O
N
N
2, R = H
6, R = CH3
R
N
O
Imidazole, Toluene
16
R' R'
1) MeI
2) NH4PF6
R' R'
8, R = H
9, R = CH3
O
N
O
O
O
R' R'
N
O
N
O
N
O
N
O
N
N
16
R' =
O
R
O
16
R' R'
O
R' R'
7
R' R'
O
N
O
O
N
O
2 PF6
PBI-1, R = H
4-Aminophenol
PBI-2, R = CH3
HO
Imidazole, Toluene
16
R' R'
PBI-3
Scheme 1. Synthesis of perylenebisimide-based receptors PBI-1, PBI-2 and PBI-3.
The fluorescence response of PBI-1 to anions was
investigated in CH3CN. As displayed in Fig. (1), the
fluorescence emission spectra of PBI-1 consist of a strong
band at 604 nm upon excitated at 568 nm. Among the anions
due to the photoinduced electron transfer (PET) and/or
intramolecular electron transfer (IET). Imidazolium ring is
the electron-deficient unit, which is usually less quenching
effect on the fluorophore. However, the formation of (C–
H)+···X- hydrogen bonds between the C-2 hydrogen atom of
the imidazolium ring and the guest anion resulted in an
increase in electron density of the ring, which could give rise
to quenching effect on the perylene-fluorophore [12].
Furthermore, phenolic hydroxy was electron rich in itself,
and the formation of O–H···X- hydrogen bond between the
phenolic hydroxy and the guest anion could strengthen the
quenching effect by an IET principle.
selected for fluorescence experiments, F- and H2PO4 resulted
-
in almost complete quenching of fluorescence, AcO-
quenched nearly 50 percent fluorescent intensity, but no
significant changes of fluorescence signal were observed
upon addition of Cl-, Br-, I-, ClO4 and HSO4 anions. In
investigating the fluorescent spectra of PBI-1, we observed
that anions could induce visible color changes of PBI-1 (Fig.
S1 in Supplementary Material). Addition of 2 equiv of
-
-
tetrabutylammonium salts of F- or H2PO4 resulted in a
-
To evaluate the essential role of the C-2 hydrogen atom
perceived color changes from red to purple, which indicated
1
of the imidazolium ring in the anion recognition, the H
that the receptor PBI-1 could serve as a colorimetric and
NMR spectroscopic study of PBI-1 was undertaken in
fluorescent sensor for selective detection of F- and H2PO4 in
-
CDCl3. As shown in Fig. (2), before and after F- or H2PO4
-
acetonitrile. We speculated that imidazolium units and
phenolic hydroxy of the receptor could serve as the hydrogen
bond donor and played an important role in recognition
process, respectively. The fluorescence quenching might be
were added, significant 1H NMR spectral changes of C2-H of
the imidazolium rings were observed, indicating that one of
interactions between receptor and guest happened through
the hydrogen bonds between the C2-H and guest anions.

Perylenebisimide-Based Colorimetric and Fluorescent Sensors
Letters in Organic Chemistry, 2010, Vol. 7, No. 6
497
of PBI-2 to various anions were investigated under the same
condition as PBI-1. We were delighted to find that only
-
H2PO4 resulted in dramatic color change of PBI-2 from red
to blue purple among a series of individual anions (Fig. S2 in
Supplementary Material). We further investigated the
fluorescent spectra of PBI-2 in the presence of various
-
anions. As shown in Fig. (3), H2PO4 quenched nearly 90
percent fluorescent intensity of PBI-2, while other anions did
not induce any obvious changes of emission intensities. The
-
high selectivity and sensitivity of PBI-2 to H2PO4 could be
potentially applicable in physiological and environmental
studies. From the above experimental results, we could also
draw a possible conclusion that the phenolic hydroxy of the
receptor was very pivotal for binding F-, but not
-
indispensable for binding H2PO4 .
Fig. (1). Changes in fluorescence intensity of PBI-1 (10 μM) (ꢀex
=
568 nm, slit
= 1.5 nm) upon addition of 2 equiv of
-
-
tetrabutylammonium salts of F-, Cl-, Br-, I-, AcO-, H2PO4 , ClO4
-
and HSO4 in CH3CN.
Upon addition of an equimolar amount of F- into the CDCl3
solution of PBI-1, the imidazolium C2-H peaks underwent
downfield shifts by 0.67 ppm (from 8.51 to 9.18). In
-
contrast, H2PO4 resulted in a larger downfield shifts by 0.78
ppm (from 8.51 to 9.29), which indicated that the hydrogen
-
bonding interaction between the C2-H and H2PO4 was
stronger than that between the C2-H and F-. In addition,
almost all protons of the aromatic rings, including the
protons of perylene-scaffold also gave rise to slight upfield
shifts. The reason might be an increase in electron density of
the aromatic rings via the interaction of hydrogen bonds
between the host and guest molecules, which rendered an
increasing shielding effect.
Fig. (3). Changes in fluorescence intensity of PBI-2 (10 μM) (ꢀex
=
568 nm, slit
= 1.5 nm) upon addition of 2 equiv of
tetrabutylammonium salts of F-, Cl-, Br-, I-, AcO-, H2PO4 , ClO4 and
-
-
-
HSO4 in CH3CN.
The fluorescence titration experiments of PBI-1 and PBI-
2 were carried out with various anions including F-, Cl-, Br-,
-
-
-
I-, ACO-, H2PO4 , ClO4 and HSO4 as shown in Fig. (4) and
Figs. (S3-S10). Taking F- anion as a representative example,
the fluorescence emission intensity of PBI-1 at 604 nm
gradually decreased with concentration increase of F- from 0
to 5 equiv (Fig. 4). Job's plot analysis for the complexation
of PBI-1 and F- corroborated the 1:1 binding stoichiometry
(Fig. 4, Inset). The association constants of the supramol-
ecular complexes were calculated by using nonlinear curve
fitting. The association constant K values of PBI-1 and PBI-2
for F- were calculated to be 4.74ꢁ105 and 1.72ꢁ104,
respectively (Table 1). The data provided a clear indication
that PBI-1 bound F- with approximately 28-fold stronger
affinity than PBI-2, which further revealed the importance of
the phenolic hydroxyl group for binding F- anion. However,
the two receptors PBI-1 and PBI-2 showed an approximate
-
association constant toward H2PO4 anion, suggesting that
the effect of phenolic hydroxyl group of the receptor for
binding H2PO4 was negligible.
Fig. (2). Partial 1H NMR spectra of PBI-1 (a), PBI-1 + 1.0 equiv of
-
-
F- (b) and PBI-1 + 1.0 equiv of H2PO4 (c) at 25 ºC in CDCl3.
In addition, the receptor PBI-3 without imidazolium
group was synthesized to further shed light on the
importance of the phenolic hydroxy for binding F- anion.
Chloroform was selected as the solvent due to the poor
solubility of PBI-3 in CH3CN. Fig. (5) showed the changes
in fluorescence intensity of PBI-3 upon addition of F-, Cl-,
We wondered whether the phenolic hydroxyl group of
the receptor was necessary for anions recognition. Thus, the
imidazolium-anchored receptor PBI-2, of which the phenolic
hydroxyl group was protected by methyl group was designed
and synthesized for comparative experiments. The responses

498 Letters in Organic Chemistry, 2010, Vol. 7, No. 6
Guo et al.
acetonitrile. The receptor PBI-1 exhibited higher binding
affinity to F- than other anions. For the phenolic hydroxyl
-
group protected receptor PBI-2, only H2PO4 resulted in a
dramatic color change from red to blue purple. These results
highlighted that imidazolium units were very important to
-
recognize both F- and H2PO4 anions, and the phenolic
hydroxyl group acted as an additional binding site for F-
anion. We believed that these results and the design strategy
were helpful to the development novel anion sensors.
EEXPERIMENTAL SECTIONS
1H NMR and 13C NMR spectra were recorded on a
Bruker AV-400 (1H: 400 MHz; 13C: 100 MHz) or a Varian
INOVA-400 (1H: 400 MHz; 13C: 100 MHz). 1H NMR
experiments were measured relative to the signals for
residual solvent signal at 7.26, 2.50, and 3.31 ppm for
CDCl3, DMSO-d6, and CD3OD, respectively. 13C NMR
experiments were measured relative to the signals for
residual solvent signal at 77.2, 39.5, and 49.0 ppm for
CDCl3, DMSO-d6, and CD3OD, respectively. Mass spectra
(MS) were obtained on a Waters Quattro Premier XE Mass
Spectrometer. High-resolution mass spectra (HR-MS) were
obtained by ESI-TOF (Waters-Q-TOF-Premier). Melting
points were determined with XRC-1 and were uncorrected.
Unless otherwise noted, materials were obtained from
commercial suppliers and were used without further
Fig. (4). Fluorescent titrations of PBI-1 (10 μM) with
tetrabutylammonium fluoride (0-5 equiv) in CH3CN (ꢀex = 568 nm,
slit = 1.5 nm). Inset: the Job’s plot.
-
-
-
Br-, I-, AcO-, H2PO4 , ClO4 and HSO4 anions in CHCl3.
Only the F- anion could modulate the fluorescence of PBI-3,
while other anions did not show obvious fluorescence
response. However, it was worth noting that F- anion only
quenched nearly 50 percent fluorescent intensity of PBI-3
even though 50 equiv of F- anion was added, which provided
Table 1. Association Constants Ka (M-1) for the Complexes of PBI-1 and PBI-2 with Various Anionsb in CH3CN at 25 ºC
K (F-)
K (H2PO4 )
K (Cl-)
K (Br-)
K (HSO4 )
-
-
Receptor
PBI-1
PBI-2
4.74ꢁ105
1.72ꢁ104
3.03ꢁ105
2.27ꢁ105
418
-
806
-
-
4.76ꢁ103
aErrors were estimated to be <15%. bAll anions were used as tetrabutylammonium salts, and the correlation coefficient (R) of nonlinear curve fitting is over 0.99.
directed evidence that the phenolic hydroxy of PBI-1 acted
purification. All of the solvents were either HPLC or
spectroscopic grade in the optical spectroscopic studies. The
stock solutions of fluorophores and anions were freshly
prepared and used for each measurement. Each time a 3 mL
of solution of receptor was filled in a quartz cell of 1 cm of
optical path length, and the stock solution of anion was
added into a quartz cell dropwise using a micro-syringe. The
volume of anion stock solution added was less than 100 μL
to remain the concentration of receptor unchanged.
Fluorescent emission spectra were collected on a Horiba
Jobin Yvon-Edison Fluoromax-4 fluorescence spectrometer.
as an auxiliary binding site for F- anion.
Experimental Procedure for 1
2,6-Bis(hydroxymethyl)-4-nitrophenol (0.63 g, 3.2
mmol), imidazole (0.81 g, 12.0 mmol) were added to 1, 4-
dioxane (10 mL) and stirred under reflux for 2 hours. After
the solvent was evaporated, the reaction was continued at
130-140 °C for 5 hours. After cooling, the agglomerating
mixture was dissolved in ethanol, then water was added,
filtered and the solid was recrystallized in ethanol, afforded
product as a yellow solid (0.67 g, yield 71%). mp: 168-170
Fig. (5). Changes in fluorescence intensity of PBI-3 (10 μM) (ꢀex
=
570 nm, slit
= 1.5 nm) upon addition of 50 equiv of
-
-
tetrabutylammonium salts of F-, Cl-, Br-, I-, AcO-, H2PO4 , ClO4 and
HSO4- in CHCl3.
1
ºC; H NMR (400 MHz, DMSO-d6): ꢀ 5.06 (s, 4H), 7.17 (s,
2H), 7.43 (s, 2H), 7.88 (s, 2H), 8.33 (s, 2H) ppm; 13C NMR
(100 MHz, DMSO-d6): ꢀ 47.1, 120.9, 124.3, 124.8, 126.5,
128.8, 136.7, 173.8; MS (ESI): calcd for C14H12N5O3 [M-H]-
298.09, found 298.02.
In conclusion, perylenebisimide-based imidazolium
receptors were synthesized and served as colorimetric and
-
fluorescent sensors for selective binding of F- or H2PO4 in

Perylenebisimide-Based Colorimetric and Fluorescent Sensors
Letters in Organic Chemistry, 2010, Vol. 7, No. 6
499
Experimental Procedure for 2
removed under the reduced pressure. The solid were
recrystallized in ethanol, afforded product as a white solid.
(0.29 g, yield 64%). mp > 190 °C (decomposition); 1H NMR
(400 MHz, DMSO-d6): ꢀ 3.61 (s, 3H), 3.97 (s, 2H), 4.96 (s,
2H), 5.10 (s, 4H), 6.08 (s, 2H), 6.91 (s, 2H), 7.11 (s, 2H),
7.68 (s, 2H); 13C NMR (100 MHz, DMSO-d6): ꢀ 44.7, 61.5,
113.1, 119.8, 128.5, 131.0, 137.7, 145.2, 145.5; MS (ESI):
calcd for C15H17N5O [M-H]- 282.14, found 282.19.
Pd/C (5%, 52 mg) and 1 (0.5 g, 1.7 mmol) were added to
methanol (30 mL), and stirred under H2 (0.7 Mpa) at 55 C
o
for 3.5 h. After cooling, Pd/C was filtered off and solvent
was removed under the reduced pressure. The solid was
recrystallized in ethanol, afforded product as a pale solid (0.3
g, yield 66%). mp > 150 ºC (decomposition); 1H NMR (400
MHz, DMSO-d6): ꢀ 5.07 (s, 4H), 6.16 (s, 2H), 6.88 (s, 2H),
7.10 (s, 2H), 7.65 (s, 2H); 13C NMR (100 MHz, DMSO-d6):
ꢀ 45.3, 114.1, 119.7, 127.1, 128.3, 137.5, 142.0, 142.4; MS
(ESI): calcd for C14H14N5O [M-H]- 268.12, found 268.04.
Experimental Procedure for 7
7 was prepared according to the referrence [13]. mp: 238-
1
240 °C; H NMR (400 MHz, CDCl3): ꢀ 0.87 (t, J = 8.0 Hz,
Experimental Procedure for 3
3H), 1.22-1.29 (m, 66H), 1.62-1.69 (m, 2H), 4.09 (t, J = 8.0
Hz, 2H), 6.81-6.84 (m, 8H), 7.23-7.26 (m, 8H), 8.22 (s, 2H),
8.21 (s, 2H); 13C NMR (100 MHz, CDCl3): ꢀ 14.2, 22.8,
27.2, 28.2, 29.4, 29.5, 29.6, 29.8, 31.6, 32.0, 34.5, 40.9,
118.1, 119.4, 119.5, 119.8, 121.7, 121.8, 122.3, 123.2, 126.8,
126.9, 133.1, 133.4, 147.7, 147.8, 152.7, 155.9, 156.7, 160.1,
163.4; MS (ESI): calcd for C82H93NO9 [M+K-H]+ 1273.64,
found 1273.70.
A mixture of 2,6-Bis(hydroxymethyl)-4-nitrophenol (2 g,
10 mmol), MeI (0.51 mL, 10 mmol), K2CO3 (1.38g, 10 mmol
) and DMF (4 mL) was stirred at room temperature for 20 h.
The solvent was removed under reduced pressure, and the
residue was purified by column chromatography on silica gel
using ethyl acetate/petroleum ether as the eluent, afforded
product as a faint yellow solid (0.54 g, yield 25%). mp:
1
137.5-138.5 ºC; H NMR (400 MHz, CD3OD): ꢀ 3.86 (s,
3H), 4.72 (s, 4H), 8.27 (s, 2H) ppm; 13C NMR (100 MHz,
CD3OD): ꢀ 59.3, 62.5, 123.6, 137.7, 145.5, 161.3; MS (ESI):
calcd for C9H11NO5 [M-H]- 212.06, found 212.02.
Experimental Procedure for 8
A mixture of 7 (1.4 g, 1.13 mmol), 2 (0.4 g, 1.49 mmol)
and imidazole (2.0 g, 29.4 mmol) in toluene (20 mL) was
refluxed under N2 for 4 h. After the solvent was evaporated,
the residue was dissolved in chloroform and washed with
water to remove the imidazole. The chloroform was then
removed, and the residue was purified by column
chromatography on silica gel using CH2Cl2/EtOH as the
eluent, afforded product as a red solid (0.89 g, yield 53%).
Experimental Procedure for 4
A mixture of 3 (1.1 g, 5.16 mmol) and SOCl2 (4 mL) was
stirred at room temperature for 12 h. Then SOCl2 was
removed and the residue was purified by column
chromatography on silica gel using ethyl acetate/petroleum
ether as the eluent, afforded product as a faint yellow solid
1
mp > 300 °C; H NMR (400 MHz, CDCl3): ꢀ 0.87 (s, 3H),
1.25-1.28 (m, 66H), 1.68 (s, 2H), 4.11 (s, 2H), 5.16 (s, 4H),
6.79-6.83 (m, 12H), 6.93 (s, 2H), 7.17-7.26 (m, 8H), 7.42 (s,
2H), 8.19 (s, 4H); 13C NMR (100 MHz, CDCl3): ꢀ 14.2, 22.8,
27.3, 28.3, 29.5, 29.7, 29.8, 31.6, 32.0, 34.4, 34.5, 40.8, 46.9,
119.3, 119.5, 119.6, 119.8, 119.9, 120.3, 120.4, 121.3, 122.1,
122.8, 126.7, 126.8, 127.1, 127.4, 128.2, 130.1, 133.0, 133.1,
137.4, 147.4, 147.4, 152.9, 153.0, 154.5, 155.8, 156.3, 163.5,
163.7; MS (ESI): calcd for C96H106N6O9 [M-H]- 1486.80,
found 1486.67.
1
(0.67 g, yield 52%). mp: 32-34 °C; H NMR (400 MHz,
CDCl3): ꢀ 4.03 (s, 3H), 4.67 (s, 4H), 8.29 (s, 2H); 13C NMR
(100 MHz, CDCl3): ꢀ 39.7, 63.5, 126.7, 133.1, 144.0, 161.5;
MS (ESI): calcd for C9H9Cl2NO3 [M+Cl]- 283.96, found
283.21.
Experimental Procedure for 5
Imidazole (0.53 g, 7.79 mmol), sodium hydride (0.19 g,
7.91 mmol) in THF (15 mL) were stirred at RT for 15 min
and solution of 4 (0.67 g, 2.68 mmol) in THF (1 mL) was
added drop wise. The mixture was stirred at room
temparature for 12 h. The solution was filtered and
evaporated to dryness, residue was purified by column
chromatography on silica gel using methanol/dichloro-
methane/ethyl acetate as the eluent, afforded product as a
Experimental Procedure for PBI-1
A solution of 8 (0.32 g, 0.21 mmol) and MeI (4 mL) was
stirred at room temperature for 72 h. Then remaining MeI
was evaporated to dryness under reduced pressure, the
residue was dissolved in methanol (10 mL) at RT and
solution of NH4PF6 (88 mg, 0.54 mmol) in water (1 mL) was
added drop wise. The solution was allowed to stir for 24 h.
The separated black solid was filtered and washed with water
and hexane to afford PBI-1 (0.19 g, yield 50%). mp > 300
1
yellow solid (0.17 g, yield 20%). mp: 218-220 °C. H NMR
(400 MHz, CDCl3): ꢀ 3.70 (s, 3H), 5.23 (s, 4H), 6.93 (s, 2H),
7.13 (s, 2H), 7.59 (s, 2H), 7.89 (s, 2H); 13C NMR (100 MHz,
CD3OD): ꢀ 46.3, 62.8, 121.1, 125.5, 129.7, 134.1, 139.1,
145.8, 162.2; MS (ESI): calcd for C15H15N5O3 [M+H]+
314.12, found 314.11.
1
°C; H NMR (400 MHz, CDCl3): ꢀ 0.87 (t, J = 8 Hz, 3H),
1.22-1.27 (m, 66H), 1.65 (s, 2H), 3.66 (s, 6H), 4.09 (s, 2H),
5.21 (s, 4H), 6.72-6.80 (m, 8H), 7.00 (s, 2H), 7.10-7.21 (m,
12H), 8.11 (s, 2H), 8.14 (s, 2H), 8.56 (s, 2H); 13C NMR (100
MHz, CDCl3): ꢀ 14.2, 22.8, 27.3, 28.3, 29.5, 29.7, 29.8, 31.6,
32.1, 34.3, 34.5, 36.3, 40.9, 48.8, 119.0, 119.4, 119.7, 119.9,
120.1, 120.8, 120.8, 121.8, 121.4, 122.9, 123.6, 124.6, 124.6,
126.7, 126.7, 132.2, 132.2, 132.9, 133.2, 136.6, 147.2, 147.7,
152.7, 153.3, 155.3, 156.6, 163.4, 163.7; HR-MS: m/z calcd
Experimental Procedure for 6
Pd/C (5%, 58 mg) and 5 (0.5 g, 1.60 mmol) were added
to methanol (15 mL), and stirred under H2 (0.7 Mpa) at 55 oC
for 3.5 h. After cooling, Pd/C was filtered and solvent was

500 Letters in Organic Chemistry, 2010, Vol. 7, No. 6
Guo et al.
- 2+
for C98H112F12N6O9P2 [M-2PF6 ] /2 758.4245, found
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9 was prepared in the same way as 8 (yield 44%). mp >
1
300 °C; H NMR (400 MHz, CDCl3): ꢀ 0.87 (t, J = 8 Hz,
3H), 1.22-1.29 (m, 66H), 1.65-1.68 (m, 2H), 3.65 (s, 3H),
4.10 (t, J = 8.0 Hz, 2H), 5.21 (s, 4H), 6.81-6.84 (m, 10H),
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8.16 (s, 2H), 8.22 (s, 2H); 13C NMR (100 MHz, CDCl3): ꢀ
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40.8, 45.6, 61.7, 119.4, 119.4, 119.8, 119.9, 120.3, 120.4,
121.3, 122.0, 122.8 ,126.7, 126.8, 129.6, 130.1, 131.4, 132.3,
133.0, 133.1, 137.7, 147.5, 152.9, 155.6, 155.9, 156.3, 163.4;
MS (ESI): calcd for C97H108N6O9 [M]+ 1501.82, found
1501.26.
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55%). mp: 267-269 °C. 1H NMR (400 MHz, CDCl3): ꢀ 0.87
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8H), 7.00-7.21 (m, 14H), 7.61(s, 2H), 7.98 (s, 4H), 8.52 (s,
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163.4; HR-MS: m/z calcd for C99H114F12N6O9P2 [M-2PF6
]2+/2 765.9363, found 765.9356.
Experimental Procedure for PBI-3
PBI-3 was prepared in the same way as 8 (yield 50%).
mp > 300 °C. 1H NMR (400 MHz, CDCl3): ꢀ 0.87 (t, J =
8Hz, 3H), 1.23-1.29 (m, 66H), 1.65-1.69 (m, 2H), 4.10 (t, J
= 8Hz, 2H), 6.81-6.85 (m, 10H), 7.04 (s, 2H), 7.21-7.25 (m,
8H), 8.23 (s, 4H); 13C NMR (100 MHz, CDCl3): ꢀ 14.2,
22.8, 27.3, 28.3, 29.5, 29.8, 31.6, 31.6, 32.1, 34.5, 40.9,
116.5, 119.4, 119.5, 119.9, 120.0, 120.5, 121.1, 122.5, 122.8,
126.8, 129.2, 133.2, 147.5, 153.0, 156.1, 156.2, 156.3, 163.6,
164.1; HR-MS: m/z calcd for C88H98N2O9 [M+H]+
1327.7351, found 1327.7333.
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ACKNOWLEDGEMENTS
This work was supported by grants from the National
Natural Science Foundation of China (Grant Nos. 20872101
& 20702035). We thank the Centre of Testing & Analysis,
Sichuan University for NMR measurements.
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SUPPLEMENTARY MATERIAL
Supplementary material is available on the publishers
Web site along with the published article.
Graph for anions induced color change and fluorescence
titrations of sensors PBI-1 and PBI-2 are available.

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