Highly selective colorimetric sensing of cyanide based on formation of dipyrrin adducts

Article abstract of DOI:10.1039/c2ob25297j

Cyanide sensing has attracted increasing interest due to its toxicity and wide use in industrial activities. Herein, we developed three colorimetric cyanide sensors by the modification of the α-position of a dipyrrin chromophore with various carbonyl grou

Full text of DOI:10.1039/c2ob25297j

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PAPER
Highly selective colorimetric sensing of cyanide based on formation of
dipyrrin adducts†
Yubin Ding, Tong Li, Weihong Zhu* and Yongshu Xie*
Received 10th February 2012, Accepted 27th March 2012
DOI: 10.1039/c2ob25297j
Cyanide sensing has attracted increasing interest due to its toxicity and wide use in industrial activities.
Herein, we developed three colorimetric cyanide sensors by the modification of the α-position of a
dipyrrin chromophore with various carbonyl groups, namely, C6F5CO, C6H5CO and CHO for 1, 2 and 3,
respectively. In dichloromethane, these sensors respond to both CN− and F− with distinct colour changes.
UV-Vis, 1H NMR and HRMS measurements imply a two-process interaction between the sensors and
CN−. Initially, CN− forms a hydrogen bond with the NH moiety, and then it attacks the carbonyl group of
the sensors via a nucleophilic addition reaction. In contrast, in aqueous systems, only cyanide induced
vivid solution colour changes from light yellow to pink via nucleophilic addition reactions. The CN−
detection limits reach a micromolar level of 3.6 × 10−6 M, 4.2 × 10−6 M and 7.1 × 10−6 M for 1, 2 and 3,
respectively. In view of the easy synthesis and the highly selective recognition of CN− with vivid colour
changes, 1–3 may be developed as a novel and promising prototype of selective and sensitive colorimetric
cyanide sensors.
number of colorimetric cyanide sensors is still rather limited
Introduction
compared with those for many other anions.8 Furthermore, many
Development of anion sensors is of great interest in supramole-
cular chemistry due to their chemical and biological impor-
tance.1 Among various anions, cyanide is known to be extremely
toxic to living organisms.2 It has been reported that 0.5–3.5 mg
of cyanide in per kg of body weight is lethal for human beings.3
Nevertheless, cyanide is still widely used in gold mining, elec-
troplating, plastics production, and other industrial activities,4
therefore, accidental release of cyanide into the environment
happens occasionally. Thus, cyanide sensing has attracted
increasing interest from the areas of chemical and environmental
sciences. Recently, some cyanide sensors have been reported for
applications in aqueous solutions and biological systems.5
Among various sensing strategies, optical sensors that are
based on colour or fluorescence changes have been greatly devel-
oped in the past decade due to their convenient synthesis and
rapid implementation.6 In particular, colorimetric sensors that
can selectively recognize anion species through visible colour
changes are widely used owing to their convenient utilization,
low cost and no equipment requirements.7 In spite of this, the
of the reported cyanide sensors cannot be applied in aqueous
media or suffer from disturbance by anions such as F− and
AcO−. Therefore, it is desirable to develop more practical
sensors that show high selectivity and sensitivity to CN− in
aqueous systems.
Dipyrrins, well known for their boron complexes as BODIPY
dyes,9 are dipyrrolic compounds which were first popularized by
Fischer and Orth.10 Research on dipyrrins mainly focuses on
their metal and boron complexes due to their interesting lumines-
cent and coordination properties,9,11 whereas the use of dipyrrins
as cation or anion sensors has not attracted much attention.11b In
this respect, we designed and synthesized di- and tripyrrins that
selectively bind Zn2+ in both DMF and aqueous solutions with a
“turn on” type fluorescence and tunable emission colours.12 On
the other hand, the NH moiety in dipyrrins may be utilized to
bind anions.13 In this respect, we have reported two acyclic oli-
gopyrrole–hemiquinone compounds (Scheme 1) for selective
binding of fluoride anions.14
Key Laboratory for Advanced Materials and Institute of Fine
Chemicals, East China University of Science and Technology, Shanghai,
P.R. China. E-mail: yshxie@ecust.edu.cn; Fax: (+86) 21-6425-2758;
Tel: (+86) 21-6425-0772
†Electronic supplementary information (ESI) available: Characterization
spectra of sensor 1; Figures and photographs showing the sensing behav-
ior of 1–3; Fig. S1–S16. See DOI: 10.1039/c2ob25297j
Scheme 1 Chemical structures of the oligopyrrole–hemiquinone com-
pounds utilized for fluoride sensing.
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Scheme 2 Stabilization of the cyanide adduct via hydrogen bonding.
Fig. 1 A photograph showing the colour change of 1 (20 μM) upon
addition of 800 μM of various anions: (a) in CH2Cl2, (b) in DMSO–
H2O, 4 : 1, v/v.
observations, the colour changes can be employed to distinguish
fluoride and cyanide from other anions by the naked eye. On the
other hand, in a water-containing solvent such as DMSO–H2O
(4 : 1), the addition of F− did not induce any noticeable colour
change. Only the addition of cyanide induced a vivid colour
change from light yellow to pink (Fig. 1b). Hence, 1 shows a
highly selective sensing of CN− in aqueous solution. Similar
results were observed for 2 and 3 (Fig. S4–S5†). Inspired by
these rough observations, we continued to investigate the CN−
sensing behavior in detail.
Scheme 3 Synthesis of sensors 1–3.
Based on this background and in view of the bright colours of
dipyrrins, we continued to check the possibility of developing
colorimetric CN− sensors based on dipyrrin compounds. One of
the effective strategies for the design of CN− sensors is the com-
bination of a hydrogen bonding donor with an electron-with-
drawing group, such as a carbonyl group.8h,u,15 In such a way,
CN− may attack the carbon atom to afford a cyanohydrin con-
taining intermediate, which may be stabilized by the hydrogen
bonding as indicated in Scheme 2.15 Fortunately, it is convenient
to synthesize carbonyl-substituted dipyrrins, which meet the
structural requirements for CN− sensing. Thus, compounds 1–3
(Scheme 3) were synthesized and utilized for colorimetric CN−
sensing.
UV-Vis absorption measurements
UV-Vis titration experiments were first carried out in dichloro-
methane. Upon addition of CN− to a CH2Cl2 solution of sensor
1, two successive processes were observed. When 0–28 μM
CN− was added (Fig. 2a), the peak at 419 nm gradually
decreased, and meanwhile a new peak centered at 498 nm gradu-
ally developed. In addition the solution colour changed to
orange, which is similar to that observed for the addition of F−.
This process can be ascribed to the occurrence of hydrogen
bonding between CN− and the N–H moiety of the sensor.8v
When more equivalents of cyanide were added, the peak at
498 nm gradually decreased and a new peak developed at about
547 nm with an isosbestic point observed at 518 nm (Fig. 2b),
indicative of another interaction process. UV-Vis spectral
changes of sensors 2 and 3 in CH2Cl2 upon addition of CN−
exhibited two processes similar to those observed for sensor 1.
For sensor 2, the addition of 0–80 μM of CN− resulted in signifi-
cant absorbance changes, and further addition of 100–400 μM of
CN− leads to the development of a new absorption peak at about
544 nm (Fig. 3), while the addition of 100–420 μM of CN− to 3
leads to disappearance of the peak at 504 nm, and development
of a new broad peak at 534 nm (Fig. 4). More equivalents of
CN− were needed to complete the interaction processes of 2 and
3 compared to those of sensor 1, indicating that the interactions
for sensors 2 and 3 are weaker as compared with 1. The differ-
ence may result from the presence of an electron withdrawing
pentafluorobenzoyl group in compound 1, which enhances its
anion affinity.
In compound 1, a strongly electron-withdrawing C6F5 group
was incorporated with the purpose of enhancing the electron-
deficient character of the carbonyl C atom, thus promoting the
interaction with CN−, and improving the sensing sensitivity.
Results and discussion
Synthesis of cyanide sensors 1–3
Compounds 1–3 were conveniently synthesized by the oxidation
of the corresponding dipyrromethanes with DDQ (2,3-dichloro-
5,6-dicyano-1,4-benzoquinone) in moderate to high yields and
were fully characterized by 1H NMR, 13C NMR and HRMS
(Scheme 3, Fig. S1–S3†); 2 and 3 have been communicated in
our previous report.12 Starting from commercially available
materials, only three steps were involved to synthesize sensors
1–3 with moderate to high yields.
Naked eye detection of CN−
For the sake of brevity, we take compound 1 as an example.
Initially, we checked the colour changes of 1 in dichloromethane
upon addition of various anions. As shown in Fig. 1a, fluoride
induced a colour change from light yellow to orange, and
cyanide induced a vivid colour change to pink. In contrast, other
anions caused only negligible colour changes. Based on these
It is well known that CN− may attack the carbon atom of a
carbonyl group and this nucleophilic reaction has been exten-
sively utilized to design CN− sensors.15,16 Considering the fact
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Fig. 2 UV-Vis spectral changes of 1 (20 μM) observed upon the addition of CN− (TBA salt) in CH2Cl2: (a) 0–28 μM; (b) 32–76 μM.
Fig. 3 UV-Vis spectral changes of 2 (10 μM) observed upon the addition of CN− (TBA salt) in CH2Cl2: (a) 0–80 μM; (b) 100–400 μM.
Fig. 4 UV-Vis spectral changes of 3 (12 μM) observed upon the addition of CN− (TBA salt) in CH2Cl2: (a) 0–74 μM; (b) 100–420 μM.
that each of the sensors has a carbonyl group at the α-position of
the pyrrolic unit, we presume that the second process observed
in UV-Vis titration measurements corresponds to the occurrence
of a nucleophilic reaction at the carbonyl carbon atom to afford a
dipyrrin adduct, which may be stabilized by the formation of an
intramolecular hydrogen bond with the NH moiety of the pyrro-
lic unit (Scheme 4). CN− sensors involving similar nucleophilic
reactions and the stabilization of resulting adduct by O−⋯H
hydrogen bonds have also been reported.8n,15 The presence of
the dipyrrin–CN− adduct is evidenced by the HRMS spectra of
the cyanide adduct of 3, in which a peak corresponding to [3 +
CN]− was observed at an m/z value of 364.0511 (Fig. S6†).
For many practical purposes, the detection limit is one of the
most important parameters in anion sensing. Based on the
UV-Vis measurements, the detection limits17 of sensors 1–3
towards CN− are determined to be 3.6 × 10−6 M, 4.2 × 10−6
M
and 7.1 × 10−6 M respectively (Fig. 5, S7–S8†). Among these
sensors, 1 shows the best detection limit, indicative of the stron-
gest interaction with CN−, which may be ascribed to the pres-
ence of an electron-withdrawing C6F5 group in the molecule of
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Scheme 4 A nucleophilic mechanism proposed for cyanide sensing
by 1.
Fig. 7 UV-Vis spectral changes of 1 (20 μM) observed upon the
addition of various anions (TBA salts, 76 μM for CN−, 200 μM for F−,
4000 μM for Cl−, Br−, I−, AcO−, and H2PO4−) in CH2Cl2.
bonding interaction between F− and the N–H moiety of sensor
1.14
Compared with the pronounced UV-Vis spectral changes
caused by CN− and F−, the addition of Cl−, Br−, I−, AcO− and
−
H2PO4 did not induce obvious changes in the colour and the
Fig. 5 A plot of (A − Amin)/(Amax − Amin) vs. log([CN−]); the calcu-
lated detection limit of sensor 1 is 3.6 × 10−6 M according to the litera-
ture method.17 A is the absorbance at 498 nm. The linear regression
affords an R value of 0.991.
UV-Vis spectrum of sensor 1 (Fig. 7). These results indicate that
in CH2Cl2, sensor 1 can be used for selective sensing of CN−
and F− based on the distinct colour changes.
For sensors 2 and 3, the addition of F− leads to similar
UV-Vis spectral changes (Fig. S9–S10†), but more equivalents
of F− are required due to the lack of an electron withdrawing
group at the α-position. Similar to that observed for 1, even
−
excess of Cl−, Br−, I−, AcO− and H2PO4 cannot induce
obvious changes in the UV-Vis spectra of sensors 2 and 3
(Fig. S11–S12†), indicating that sensors 2 and 3 can also be
used for selective sensing of CN− and F− in CH2Cl2.
1H NMR titration study
Further insights into the proposed sensing mechanism were
1
investigated by H NMR titration measurements. For sensor 1,
the pyrrolic NH peak has a large chemical shift value of
13.01 ppm, indicating the presence of an intramolecular
N–H⋯N hydrogen bond. With the addition of 12 mM of CN−,
the NH peak is weakened with new peaks developing at 6.18,
6.13 and 6.07 ppm (Fig. 8), indicative of the generation of a
cyanide adduct, which is accompanied by interruption of the
original intramolecular hydrogen bonding and the formation of a
new H-bond between CN− and the NH group.8h,n,15 With the
addition of 40 mM of CN−, the pyrrolic α proton at 8.24 ppm is
shifted to 6.73, and the peaks for β-pyrrolic protons are also
shifted upfield, which may result from the shielding effect of the
more electron-rich cyanohydrin group as compared with the
original carbonyl group.
Fig. 6 UV-Vis spectral changes of 1 (20 μM) observed upon the
addition of 0–200 μM F− (TBA salt) in CH2Cl2.
1. These detection limit values lie below the safety limit of
7.8 μM set by the US Environmental Protection Agency,18 indi-
cating that these sensors may be sensitive enough for potential
applications.
In contrast to the two processes observed upon addition of
cyanide, addition of fluoride to a CH2Cl2 solution of 1 induced
simple UV-Vis spectral changes (Fig. 6), with the peak at
419 nm gradually decreased and a new peak developed at
498 nm. Three isosbestic points were observed at 306, 353 and
446 nm, indicative of a clean conversion throughout the titration
process. The spectral changes can be ascribed to an internal
charge transfer (ICT) process originating from the hydrogen
For sensor 2, a decrease of the NH signal was also observed
upon adding 12 mM of CN−, and phenyl and pyrrolic protons of
2 also showed an upfield shift to δ 7.83, 7.54, 7.47, 6.75, 6.13,
6.04, 5.99 ppm upon adding more equiv. of CN− (Fig. S13†).
1
Similar results were also observed during the H NMR titration
of 3 with CN− (Fig. S14†). The two interaction processes
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1
Fig. 8 Plots of H NMR spectra of 1 (20 mM) on addition of CN− in
CDCl3.
observed in the 1H NMR titration experiments are consistent with
those obtained from UV-Vis absorption measurements, and these
results support the proposed “nucleophilic addition” mechanism.
Highly selective sensing of CN− in aqueous solutions
For many practical purposes, it is important to detect CN− in
aqueous systems. To examine the practicability of these sensors,
we checked the sensing behavior in DMSO–H2O (4 : 1, v/v). To
our delight, sensors 1–3 can selectively sense CN− in the
aqueous media. With the addition of CN− to an aqueous solution
of sensor 1, the colour changed from light yellow to pink
(Fig. 1b) and a new absorption peak developed at 545 nm
(Fig. 9a). In contrast, other anions, such as F−, Cl−, Br−, I−,
AcO−, H2PO4− cannot induce obvious colour or UV-Vis absorp-
tion changes even with a large excess (Fig. 9a), which may be
ascribed to the suppression of hydrogen bonding interactions in
the aqueous solution. It is well known that cyanide sensing may
be detrimentally interfered with by some other anions, especially
F− and AcO−. Thus, we continued to perform competition
Fig. 9 Changes in the UV-Vis absorption spectrum of 1 (20 μM) in the
presence of the TBA salts of various anions (400 μM for CN−, 4000 μM
for F−, Cl−, Br−, I−, AcO−, H2PO4−) in DMSO–H2O, 4 : 1, v/v: (a) in
the presence of various anions. (b) White bars represent the addition of
anions. Black bars represent the addition of 4000 μM of indicated
anions, followed by 400 μM of CN− anions.
Hence, 1–3 can be utilized to selectively sense F− and CN−
based on distinct colour changes. The detection limits of sensing
CN− are 3.6 μM, 4.2 μM and 7.1 μM for 1, 2, and 3, respect-
ively. However in aqueous solution, due to the competition
effect of H2O, the hydrogen bonding interactions are suppressed
and sensors 1–3 no longer respond to F−. Fortunately, CN− may
attack the carbonyl group of these dipyrrins to afford an adduct,
which is accompanied by vivid colour changes, and this provides
a convenient approach for sensing CN− in aqueous solutions.
These results indicate that the incorporation of a carbonyl group
into the α-position of a dipyrrin unit is an effective strategy for
designing CN− sensors which can be utilized in both organic
solvent and aqueous systems, and the detection limit can be
easily modulated by the substituent attached to the carbonyl
group. In view of the easy synthesis and the highly selective rec-
ognition of CN− with vivid colour changes, 1–3 may be devel-
oped as a novel and promising prototype of selective and
sensitive colorimetric cyanide sensors.
experiments to further elucidate the selectivity of the sensors.
When various anions (F−, Cl−, Br−, I−, AcO− and H2PO4
)
−
were added at 4000 μM to the solutions of 1, no obvious absorp-
tion changes were observed, but when 400 μM CN− was added,
the solution colours vividly changed from light yellow to pink
and a new peak developed at about 545 nm (Fig. 9b). From
these results, we can conclude that in the solutions of these
sensors, the addition of competing anions did not interfere sig-
nificantly with CN− sensing. Similarly, selective sensing of CN−
was also observed for sensors 2 and 3. Corresponding spectra
are shown in the ESI (Fig. S15–16†). Accordingly, sensors 1–3
can be established as a novel and promising type of highly selec-
tive colorimetric cyanide sensor in aqueous media.
Conclusions
In conclusion, we synthesized three dipyrrin compounds 1–3.
Each of the molecules has a carbonyl group attached to the
α-position of the pyrrolic unit. Upon addition of F− to dichloro-
methane solutions of 1–3, the solution colours changed from
light yellow to orange, and the addition of CN− induced a vivid
colour change to pink. In contrast, the addition of Cl−, Br−, I−,
Experimental
General
Commercial available solvents and reagents were used as
received. Water was used after redistillation. Deuterated solvents
AcO− and H2PO4 did not induce obvious colour changes.
−
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for NMR measurements were available from Aldrich. UV-Vis
absorption spectra were recorded on a Varian Cary 100 spectro-
photometer, with a quartz cuvette (path length = 1 cm).
1H NMR and 13C NMR spectra were obtained using a Bruker
AM 400 spectrometer with tetramethylsilane (TMS) as the
internal standard. HRMS were performed using a Waters LCT
Premier XE spectrometer. Column chromatography was carried
out in air using silica gel (200–300 mesh) purchased from
Qingdao Haiyang Chemical Co., Ltd (China). Reactions were
monitored by thin-layer chromatography. P1, P2 and P3 were
prepared from the reaction of pyrrole with corresponding alde-
hydes according to reported methods.19 The preparation of 2 and
3 were communicated in our previous work.12
Ph-H), 7.5 (t, 2H, Ph-H), 6.8 (d, 1H, J = 4.0 Hz, pyrrolic), 6.71
(d, 1H, J = 4.4 Hz, pyrrolic), 6.64 (d, 1H, J = 4.8 Hz, pyrrolic),
6.27 (d, 1H, J = 4.0 Hz, pyrrolic). 13C NMR (CDCl3, Bruker
100 MHz, 298 K): δ 185.10, 163.39, 152.76, 138.49, 137.88,
135.28, 133.44, 132.38, 129.08, 128.47, 128.13, 122.36, 119.63,
119.23. HRMS: obsd 415.0874, calcd for C22H12F5N2O ([M +
H]+): 415.0870. Anal. Calcd for C22H11N2OF5 (%): C, 63.77, H,
2.68, N, 6.76. Found: C, 63.56, H, 2.67, N, 6.77%.
Synthesis of 3
P3 (340 mg, 1 mmol) was dissolved in 250 mL of CH2Cl2, then
DDQ (340 mg, 1.5 mmol) was added. The mixture was stirred at
room temperature for 30 min and then purified by a silica gel
column (eluent: CH2Cl2–PE = 1 : 1) to afford the crude product
3 which was recrystallized from CH2Cl2 and n-hexane (251 mg,
yield: 74.2%). Mp: 118–119 °C. UV-Vis (CH2Cl2) λmax (nm):
UV-Vis absorption spectra measurements
The absorption spectra of 1 (20 μM) were measured at 25 °C in
dichloromethane and aqueous solution (DMSO–H2O, 4 : 1, v/v).
The absorption spectra of 2 (10 μM) and 3 (12 μM) were
measured under the same conditions. Tested anions such as F−,
CN−, Cl−, Br−, I−, AcO−, H2PO4− were added as TBA salts dis-
solved in dichloromethane.
1
261, 417. H NMR (CDCl3, Bruker 400 MHz, 298 K): δ 12.76
(b, 1H, pyrrolic-NH), 9.72 (s, 1H, CHO-H), 8.16 (s, 1H, pyrro-
lic-αH), 6.90 (d, 1H, J = 4.4 Hz, pyrrolic), 6.71 (d, 1H, J = 4.8
Hz, pyrrolic), 6.65 (d, 1H, J = 4.8 Hz, pyrrolic), 6.26 (d, 1H, J =
4.0 Hz, pyrrolic). 13C NMR (CDCl3, Bruker 100 MHz, 298 K):
δ 180.49, 163.74, 153.16, 139.27, 136.07, 133.60, 128.51,
119.91, 119.65. HRMS: obsd 339.0562, calcd for C16H8F5N2O
([M + H]+): 339.0557. Anal. Calcd for C16H7N2OF5 (%): C,
56.82, H, 2.09, N, 8.28. Found: C, 56.72, H, 2.19, N, 8.18%.
1H NMR titration details
1H NMR titrations of 1–3 with anions were performed in CDCl3,
with 0.01 mmol of each sensor dissolved in 0.5 mL of CDCl3.
Tetrabutylammonium cyanide was dissolved in CDCl3, and
added to the NMR tube via a syringe.
Acknowledgements
This work was financially supported by NSFC/China, the
Program for Professor of Special Appointment (Eastern Scholar)
at Shanghai Institutions of Higher Learning, Program for
New Century Excellent Talents in University (NCET),
Innovation Program of Shanghai Municipal Education Commis-
sion, the Fundamental Research Funds for the Central Univer-
sities (WK1013002), and SRFDP (200802510011 and
20100074110015).
Synthesis of 1
P1 (253 mg, 0.5 mmol) was dissolved in 125 mL of CH2Cl2,
then DDQ (170 mg, 0.75 mmol) was added. The mixture was
stirred at room temperature for 2 h and then purified by a silica
gel column (eluent: CH2Cl2–PE = 1 : 2) to afford the crude
product 1 which was recrystallized from CH2Cl2 and n-hexane
(121 mg, yield: 48%). Mp: 108–109 °C. UV-Vis (CH2Cl2) λmax
1
(nm): 273, 419. H NMR (CDCl3, 400 MHz, 298 K): δ = 12.99
Notes and references
(s, 1H, pyrrolic-NH), 8.22 (s, 1H, pyrrolic-αH), 6.74 (d, J = 4.8
Hz, 1H, pyrrolic-βH), 6.70 (d, J = 4.8 Hz, 1H, pyrrolic-βH),
6.64 (d, J = 4.4 Hz, 1H, pyrrolic-βH), 6.24 (d, J = 4.0 Hz, 1H,
pyrrolic-βH). 13C NMR (CDCl3, Bruker 100 MHz, 298 K): δ
173.4, 165.0, 154.4, 137.4, 137.1, 134.0, 129.3, 121.7, 120.2,
119.3. HRMS: obsd 505.0392, calcd for C22H7N2OF10 ([M +
H]+): 505.0399. Anal. Calcd for C22H6N2OF10·0.2C6H14 (%): C,
53.43, H, 1.70, N, 5.37. Found: C, 53.31, H, 1.96, N, 5.27%.
1 (a) P. D. Beer and P. A. Gale, Angew. Chem., Int. Ed., 2001, 40, 486–
516; (b) Z. Xu, X. Chen, H. N. Kim and J. Yoon, Chem. Soc. Rev., 2010,
39, 127–137; (c) J. L. Sessler, P. A. Gale and W.-S. Cho, Anion Receptor
Chemistry, Royal Society of Chemistry, Cambridge, 2006;
(d) R. Martinez-Manez and F. Sancenon, Chem. Rev., 2003, 103, 4419–
4476.
2 (a) B. Vennesland, E. E. Comm, C. J. Knownles, J. Westly and
F. Wissing, Cyanide in Biology, Academic Press, London, 1981;
(b) R. Koenig, Science, 2000, 287, 1737–1738; (c) Y. C. Yang,
J. A. Baker and J. R. Ward, Chem. Rev., 1992, 92, 1729–1743.
3 (a) M. Tomasulo, S. Sortino, A. J. P. White and F. M. Raymo, J. Org.
Chem., 2006, 71, 744–753; (b) Guidelines for Drinking-Water Quality,
World Health Organization, Geneva, 1996.
Synthesis of 2
4 (a) H. Hachiya, S. Ito, Y. Fushinuki, T. Masadome, Y. Asano and
T. Imato, Talanta, 1999, 48, 997–1004; (b) S. I. Baskin and T. G. Brewer,
in Medical Aspects of Chemical and Biological Warfare, ed. F. Sidell,
E. T. Takafuji and D. R. Franz, TMM Publications, Washington, 1997.
5 (a) C. H. Lee, H. J. Yoon, J. S. Shim and W. D. Jang, Chem.–Eur. J.,
2012, 18, 4513–4516; (b) U. S. Schubert, M. Hager, A. Wild and
A. Winter, Analyst, 2012, 137, DOI: 10.1039/c2an35119f; (c) E. Z. Lee,
S. U. Lee, N. S. Heo, G. D. Stucky, Y. S. Jun and W. H. Hong, Chem.
Commun., 2012, 48, 3942–3944; (d) Y. Liu, X. Lv, Y. Zhao, J. Liu,
Y. Q. Sun, P. Wang and W. Guo, J. Mater. Chem., 2012, 22, 1747–1750.
P2 (500 mg, 1.2 mmol) was dissolved in 300 mL of CH2Cl2,
then DDQ (409 mg, 1.8 mmol) was added. The mixture was
stirred at room temperature for 1 h and then purified by a silica
gel column (eluent: CH2Cl2) to afford the crude product 2 which
was recrystallized from CH2Cl2 and n-hexane (205 mg, yield:
41.2%). Mp: 92–94 °C. UV-Vis (CH2Cl2) λmax (nm): 280, 429.
1H NMR (CDCl3, Bruker 400 MHz, 298 K): δ 12.89 (s, 1H, pyr-
rolic-NH), 8.16 (s, 1H, pyrrolic), 7.93 (t, 2H, Ph-H), 7.59 (t, 1H,
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6 (a) H. N. Kim, Z. Guo, W. Zhu, J. Yoon and H. Tian, Chem. Soc. Rev.,
2011, 40, 79–93; (b) A. P. de Silva, G. D. McClean and T. S. Moody,
Encyclopedia of Supramolecular Chemistry, 2004, 572–578;
(c) B. Valeur and I. Leray, Coord. Chem. Rev., 2000, 205, 3–40;
(d) S. Y. Chung, S. W. Nam, J. Lim, S. Park and J. Yoon, Chem.
Commun., 2009, 2866–2868; (e) L. Xue, Q. Liu and H. Jiang, Org. Lett.,
2009, 11, 3454–3457; (f) L. H. Peng, M. Wang, G. X. Zhang,
D. Q. Zhang and D. B. Zhu, Org. Lett., 2009, 11, 1943–1946;
(g) L. Fabbrizzi, M. Licchelli, F. Mancin, M. Pizzeghello, G. Rabaioli,
A. Taglietti, P. Tecilla and U. Tonellato, Chem.–Eur. J., 2002, 8, 94–101;
(h) X. J. Peng, J. Du, J. Fan, J. Wang, Y. Wu, J. Zhao, S. Sun and T. Xu,
J. Am. Chem.Soc., 2007, 129, 1500–1501; (i) A. Li, H. He, Y. Ruan,
Z. Wen, J. Zhao, Q. Jiang and Y. B. Jiang, Org. Biomol. Chem., 2009, 7,
193–200; ( j) K. Huang, H. Yang, M. Yu, X. Gao, Z. Zhou, F. Y. Li, T. Yi
and C. Huang, Org. Lett., 2008, 10, 2557–2560; (k) H. Zhang, L. Han,
K. Zachariasse and Y. B. Jiang, Org. Lett., 2005, 7, 4217–4220;
(l) L. Fabbrizzi, M. Licchelli, P. Pallavicini, A. Perotti, A. Taglietti and
D. Sacchi, Chem.–Eur. J., 1996, 2, 75–82; (m) H. Lu, L. Xiong, H. Liu,
M. Yu, Z. Shen, F. Y. Li and X. You, Org. Biomol. Chem., 2009, 7,
2554–2558.
Commun., 2008, 5848–5850; (s) E. Palomares, M. V. Martinez-Diaz,
T. Torres and E. Coronado, Adv. Funct. Mater., 2006, 16, 1166–1170;
(t) F. Garcia, J. M. Garcia, B. Garcia-Acosta, R. Martinez-Manez,
F. Sancenon and J. Soto, Chem. Commun., 2005, 2790–2792;
(u) D.-S. Kim, Y.-M. Chung, M. Jun and K. H. Ahn, J. Org. Chem.,
2009, 74, 4849–4854; (v) C. Denekamp, K. Suwinska, H. Salman,
Y. Abraham, Y. Eichen and J. Ben Ari, Chem.–Eur. J., 2007, 13, 657–
665.
9 (a) G. Ulrich, R. Ziessel and A. Harriman, Angew. Chem., Int. Ed., 2008,
47, 1184–1201; (b) A. Loudet and K. Burgess, Chem. Rev., 2007, 107,
4891–4932.
10 H. Fischer and H. Orth, Die Chemie des Pyrrols, Akademische Verlags-
gesellschaft, Leipzig, 1937.
11 (a) T. E. Wood and A. Thompson, Chem. Rev., 2007, 107, 1831–1861;
(b) M. A. Filatov, A. Y. Lebedev, S. N. Mukhin, S. A. Vinogradov and
A. V. Cheprakov, J. Am. Chem. Soc., 2010, 132, 9552–9554;
(c) I. V. Sazanovich, C. Kirmaier, E. Hindin, L. Yu, D. F. Bocian,
J. S. Lindsey and D. Holten, J. Am. Chem. Soc., 2004, 126, 2664–2665;
(d) J. Y. Shin, D. Dolphin and B. O. Patrick, Cryst. Growth Des., 2004, 4,
659–661; (e) Y. Zhang, A. Thompson, S. J. Rettig and D. Dolphin, J. Am.
Chem. Soc., 1998, 120, 13537–13538.
7 F. H. Zelder and C. Mannel-Croise, Chimia, 2009, 63, 58–62.
8 (a) H. Miyaji and J. L. Sessler, Angew. Chem., Int. Ed., 2001, 40, 154–
157; (b) N. Kumari, S. Jha and S. Bhattacharya, J. Org. Chem., 2011, 76,
8215–8222; (c) J. Isaad and F. Salaun, Sens. Actuators, B, 2011, 157, 26–
33; (d) Y. Shiraishi, M. Itoh and T. Hirai, Tetrahedron Lett., 2011, 52,
1515–1519; (e) M. O. Odago, D. M. Colabello and A. J. Lees, Tetrahe-
dron, 2010, 66, 7465–7471; (f) G. J. Kim and H. J. Kim, Tetrahedron
Lett., 2010, 51, 2914–2916; (g) M. Tomasulo and F. M. Raymo, Org.
Lett., 2005, 7, 4633–4636; (h) C.-L. Chen, Y.-H. Chen, C.-Y. Chen and
S.-S. Sun, Org. Lett., 2006, 8, 5053–5056; (i) S. Vallejos, P. Estevez, F.
C. Garcia, F. Serna, J. L. de la Pena and J. M. Garcia, Chem. Commun.,
2010, 46, 7951–7953; ( j) P. Kaur, S. Kaur and K. Singh, Inorg. Chem.
Commun., 2009, 12, 978–981; (k) Y. Sun, G. F. Wang and W. Guo, Tetra-
hedron, 2009, 65, 3480–3485; (l) G. Qian, X. Z. Li and Z. Y. Wang,
J. Mater. Chem., 2009, 19, 522–530; (m) C. Mannel-Croise and F. Zelder,
Inorg. Chem., 2009, 48, 1272–1274; (n) H. T. Niu, D. D. Su, X. L. Jiang,
W. Z. Yang, Z. M. Yin, J. Q. He and J. P. Cheng, Org. Biomol. Chem.,
2008, 6, 3038–3040; (o) X. H. Zhang, C. Li, X. X. Cheng, X. S. Wang
and B. W. Zhang, Sens. Actuators, B, 2008, 129, 152–157;
(p) Y. K. Yang and J. Tae, Org. Lett., 2006, 8, 5721–5723;
(q) Z. Ekmekci, M. D. Yilmaz and E. U. Akkaya, Org. Lett., 2008, 10,
461–464; (r) X. D. Lou, L. Y. Zhang, J. G. Qin and Z. Li, Chem.
12 Y. Ding, Y. Xie, X. Li, J. P. Hill, W. Zhang and W. Zhu, Chem. Commun.,
2011, 47, 5431–5433.
13 J. L. Sessler, S. Camiolo and P. A. Gale, Coord. Chem. Rev., 2003, 240,
17–55.
14 Q. G. Wang, Y. S. Xie, Y. B. Ding, X. Li and W. H. Zhu, Chem.
Commun., 2010, 46, 3669–3671.
15 (a) Y. M. Chung, B. Raman, D.-S. Kim and K. H. Ahn, Chem. Commun.,
2006, 186–188; (b) Y. K. Kim, Y.-H. Lee, H.-Y. Lee, M. K. Kim,
G. S. Cha and K. H. Ahn, Org. Lett., 2003, 5, 4003–4006; (c) H. B. Yu,
Q. Zhao, Z. X. Jiang, J. G. Qin and Z. Li, Sens. Actuators, B, 2010, 148,
110–116.
16 J. Isaad and A. El Achari, Tetrahedron, 2011, 67, 4196–4201.
17 M. Shortreed, R. Kopelman, M. Kuhn and B. Hoyland, Anal. Chem.,
1996, 68, 1414–1418.
18 Regulatory body: Enviornment Protection Agency, USA; Drinking water
quality legislation of the United States, 1974; Safe Drinking Water Act
PL 93-523, Subchapter 6A of Title 42.
19 (a) A. Lembo, P. Tagliatesta, D. Cicero, A. Leoni and A. Salvatori, Org.
Biomol. Chem., 2009, 7, 1093; (b) B. J. Littler, M. A. Miller,
C. H. Hung, R. W. Wagner, D. F. O’Shea, P. D. Boyle and J. S. Lindsey,
J. Org. Chem., 1999, 64, 1391–1396.
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