Fluorescent chemodosimeter for selective detection of cyanide in water

Article abstract of DOI:10.1021/ol7025763

A coumarin-based fluorescent chemodosimeter with a salicylaldehyde functionality as a binding site has been developed for selective detection of cyanide anions over other anions in water at biological pH.

Full text of DOI:10.1021/ol7025763

ORGANIC
LETTERS
2
008
Vol. 10, No. 1
9-51
Fluorescent Chemodosimeter for
Selective Detection of Cyanide in Water
4
Kyung-Sik Lee, Hae-Jo Kim,*,‡ Gun-Hee Kim, Injae Shin, and Jong-In Hong*
†
§
§
,†
Department of Chemistry, College of Natural Sciences, Seoul National UniVersity,
Seoul 151-747, Korea, Department of Chemistry, Kyonggi UniVersity, Suwon 443-760,
Korea, and Department of Chemistry, Yonsei UniVersity, Seoul 120-749, Korea
jihong@snu.ac.kr; haejkim@kgu.ac.kr
Received October 23, 2007
ABSTRACT
A coumarin-based fluorescent chemodosimeter with a salicylaldehyde functionality as a binding site has been developed for selective detection
of cyanide anions over other anions in water at biological pH.
The cyanide ion is an extremely hazardous material that
damages by absorption through the lungs, gastrointestinal
track, and skin and can kill mammals upon binding to a heme
interest in sensing the presence of the toxic cyanide anion
by coordination or covalent bonds.
4
5
Among the various chemosensors, fluorescent chemosen-
sors present many advantages, including high sensitivity, low
cost, easy detection, and suitability as a diagnostic tool for
1
unit. The process of cellular respiration in mammals is
inhibited by the cyanide anion, which interacts strongly with
2
6,7
a heme unit in the active site of cytochrome a
3
. Although
biological concern. Unfortunately, few, if any, fluorescent
cyanides have been found in many foods and plants, most
environmental cyanides are released by industries involved
in gold mining, electroplating, and metallurgy. Humans may
be exposed to cyanides from dietary, industrial, environ-
mental, and other sources. Consequently, there is a growing
cyanide anion sensors are capable of displaying high
selectivity over other anions in pure water.
Salicylaldehyde is a popular reaction counterpart for
nucleophilic addition reactions owing to its activated carbonyl
5
e,8
3
(3) Young, C.; Tidwell, L.; Anderson, C. Cyanide: Social, Industrial,
and Economic Aspects; Minerals, Metals, and Materials Society: Warren-
dale, 2001.
(4) (a) Kim, Y. H.; Hong, J.-I. Chem. Commun. 2002, 512. (b)
Anzenbacher, P., Jr.; Tyson, D. S.; Jurs ´ı kov a´ , K.; Castellano, F. N. J. Am.
Chem. Soc. 2002, 124, 6232.
†
Seoul National University.
Kyonggi University.
Yonsei University.
‡
§
(1) Baskin, S. I.; Brewer, T. G. In Medical Aspects of Chemical and
Biological Warfare; Sidell, F., Takafuji, E. T., Franz, D. R., Eds.; TMM
Publications: Washington, DC, 1997; Chapter 10, pp 271-286.
(5) (a) Chung, Y.; Lee, H.; Ahn, K. H. J. Org. Chem. 2006, 71, 9470.
(b) Chung, Y. M.; Raman, B.; Kim, D.-S.; Ahn, K. H. Chem. Commun.
2006, 186. (c) Yang, Y.-K.; Tae, J. Org. Lett. 2006, 8, 5721. (d) Chen,
C.-L.; Chen, Y.-H.; Chen, C.-Y.; Sun, S.-S. Org. Lett. 2006, 8, 5053. (e)
Tomasulo, M.; Sortino, S.; White, A. J. P.; Raymo, F. M. J. Org. Chem.
2006, 71, 744.
(
2) (a) Warburg, O. Hoppe-Seyler’s Z. Physiol. Chem. 1911, 76, 331-
3
46. (b) Kellin, D. Proc. R. Soc. London, Ser. B 1929, 104, 206-251. (c)
Vennesland, B.; Comm, E. E.; Knownles, C. J.; Westly, J.; Wissing, F.
Cyanide in Biology; Academic Press: London, 1981.
1
0.1021/ol7025763 CCC: $40.75
© 2008 American Chemical Society
Published on Web 12/05/2007

by a phenolic hydrogen through an intramolecular hydrogen
thereby inducing the hyperchromic effect and fluorescence
enhancement.
We investigated the H NMR spectra of the dosimeter 1
9
10
bond. Resonance-assisted hydrogen bonding (RAHB) is
one of the driving forces for the reactions, as observed in
pyridoxal phosphate.11
1
in the presence of cyanide anions and compared it with that
Herein, we report a selective fluorescent chemodosimeter
a
of the sensor itself (Figure 1). The aldehyde proton (H ) at
1
for cyanide ion detection (Scheme 1). The dosimeter 1
Scheme 1. Structure of the Dosimeter and Its Proposed
Cyanide-Sensing Mechanism
Figure 1. 1H NMR spectral change of the dosimeter upon addition
of cyanide anions: (a) sensor only and (b) sensor and 10 equiv of
NaCN ([1] ) 10 mM in D O at 25 °C).
2
has a coumarin group as a fluorescent signal unit and a
salicylaldehyde functionality as a recognition or reaction unit.
around δ 10.1 ppm was dramatically shifted upfield toward
δ 6.1 ppm (H ) upon cyanide addition at room temperature.
This chemical shift of H was consistent with a cyanohydrin
b
For this aim, the dosimeter 1 was synthesized according to
the literature procedure.12
b
form due to the nucleophilic attack of the cyanide anion
Cyanide is expected to be detectable by a nucleophilic
attack toward a carbonyl functional group, which has been
activated by the phenol proton of the dosimeter 1 through
the intramolecular hydrogen bonding. Fast proton transfer
of the phenol hydrogen to the developing alkoxide anion
causes the strong fluorescence of the sensor (Scheme 1), as
previously studied by a chromogenic cyanide dosimeter based
on salicylaldehyde. It has been shown that the deprotonation
of the phenol proton upon the addition of cyanides created
a color change due to the bathochromic shift in the azo-
based dosimeter.13 However, with the present dosimeter,
cyanide anions operate as a nucleophile toward the sensor,
1
toward the dosimeter’s carbonyl group. H NMR analysis
indicated that the cyanide anion functions as a nucleophile
in water.
These cyanide-sensing phenomena were monitored by
fluorescence titration in an aqueous solvent (HEPES buffer
at pH 7.4). Fluorescence monitoring of the cyanide addition
reaction was performed by using a 10 µM solution of the
dosimeter 1 in water under biological pH at room temper-
ature. Upon addition of cyanide anions, the fluorescence
emission intensity of the dosimeter at λem ) 450 nm was
increased 190-fold and was saturated at 1500 equiv of
cyanide (Figure 2, Figure S1). Job analysis for the complex-
(6) (a) Brz o´ zka, Z. In ComprehensiVe Supramolecular Chemistry;
Atwood, J. L., Davies, J. E. D., MacNicol, D. D., V o¨ gtle, F., Suslick, K.
S., Eds.; Pergamon: Oxford, 1996; Vol. 1, pp 187-212. (b) Desvergne,
J.-P.; Czarnik, A. W. Chemosensors of Ion and Molecular Recognition;
Kluwer: Dordrecht, The Netherlands, 1997; Vol. 492. (c) Schmidtchen, F.
P.; Berger, M. Chem. ReV. 1997, 97, 1609-1646. (d) Beer, P. D. Acc. Chem.
Res. 1998, 31, 71-80. (e) Binachi, K.; Bowman-James, K.; Garc ´ı a-Espa n˜ a,
E. Supramolecular Chemistry for Anions; Wiley-VCH: New York, 1997.
(
f) Lehn, J.-M. Supramolecular Chemistry, Concepts and PerspectiVes;
VCH: Weinheim, Germany, 1995. (g) Mart ´ı nez-M a´ n˜ ez, R.; Sancenon, F.
Chem. ReV. 2003, 103, 4419-4476. (h) Beer, P. D.; Gale, P. A. Angew.
Chem. 2001, 113, 502-532; Angew. Chem., Int. Ed. 2001, 40, 486-516.
(7) (a) Fabbrizzi, L.; Poggi, A. Chem. Soc. ReV. 1995, 24, 197-202. (b)
Valeur, B.; Leray, I. Coord. Chem. ReV. 2000, 205, 3-40. (c) Anslyn, E.
V. Curr. Opin. Chem. Biol. 1999, 3, 740. (d) Fabbrizzi, L.; Licchelli, M.;
Pallavicini, P.; Parodi, L.; Taglietti, A. Transition Metals in Supramolecular
Chemistry; John Wiley & Sons Ltd.: New York, 1999; p 93. (e) Lakowicz,
J. R. Principles of Fluorescence Spectroscopy; Plenum Publishers Corpora-
tion: New York, 1999.
(
8) (a) Badugu, R.; Lacowikcz, J. R.; Geddes, C. D. Anal. Biochem. 2004,
27, 82-90. (b) Badugu, R.; Lacowikcz, J. R.; Geddes, C. D. J. Am. Chem.
Soc. 2005, 127, 3635-3641. (c) Tomasulo, M.; Raymo, F. M. Org. Lett.
005, 7, 4633-4636.
9) Albayrak, C.; Odabasoglu, M.; B u¨ y u¨ kg u¨ ng o¨ r, O.; L o¨ nnecke, P. Acta
Crystallogr. 2004, C60, o318.
3
Figure 2. Fluorescence titration spectra of the dosimeter upon
2
addition of cyanide anion. Inset: Fluorescence change of the sensor
(
-
against [CN ]/[1] ([1] ) 10 µM, λex ) 360 nm, λem ) 450 nm).
(
(
10) Gust, R.; Sch o¨ nenberger, H. Eur. J. Med. Chem. 1993, 28, 103.
11) Dugas, H. Bioorganic Chemistry: A Chemical Approach to Enzyme
Action, 3rd ed.; Springer: New York, 1996; pp 520-542.
ation of the sensor and cyanide also corroborated the 1:1
binding stoichiometry (Figure S4).
To evaluate the selectivity of the dosimeter 1 for cyanide,
we monitored the fluorescence intensities for various anions
(
12) (a) Sp a¨ th, E.; Pailer, M. Chem. Ber. 1935, 68, 940-943. (b)
Ramasay, S. L.; Freeman, C.; Grace, P. B.; Redmond, J. W.; MacLeod, J.
K. Carbohydr. Res. 2001, 333, 59-71.
(
13) Lee, K.-S.; Lee, J. T.; Hong, J.-I.; Kim, H.-J. Chem. Lett. 2007, 36,
8
16-817.
50
Org. Lett., Vol. 10, No. 1, 2008

upon addition of excess guests in HEPES buffer solution at
pH 7.4.
blue fluorescence response was selectively observed only in
the presence of cyanide in the solution of 10 µM of the sensor
(Figure 4).
The dosimeter’s fluorescence intensity was highly en-
-
hanced by cyanide. However, other anions such as F ,
-
-
-
-
-
-
-
-
2 4 4 3 3
H PO , AcO , ClO , Br , Cl , I , NO , and N did not
cause any significant changes in the fluorescence emission
intensity, even at a concentration of 1500 equiv of guests
(Figure 3a). The fluorescence profiles at 450 nm of the
Figure 4. Fluorescence responses of the dosimeter (10 µM) in
the presence of 1500 equiv of different anions: (a) only the sensor,
-
-
-
-
-
-
(
b) CN , (c) F , (d) H
2
PO
4
, (e) AcO , (f) ClO
3
4
, (g) Br , (h)
-
-
-
-
Cl , (i) I , (j) NO
3
, and (k) N
(sodium salts).
The in vivo selectivity of the dosimeter 1 for cyanide was
also examined with living cells by using a fluorescence
microplate reader. After P19 cells were incubated with 100
µM of the sensor for 1 h at 37 °C, the fluorescence images
in the cells were monitored with increasing amounts of
cyanide and compared with those in the cells without
cyanide. Only the P19 cells treated with 1 mM cyanide
showed a significant fluorescence intensity in the living cells
(Figures S5 and S6).
In summary, a chemodosimeter having a salicylaldehyde
moiety as a binding unit and a coumarin skeleton as a
signaling unit was synthesized, and its fluorescence properties
in the presence of anions were evaluated. The chemodosim-
eter displayed a dramatic change in fluorescence intensity
selectively for cyanide anions over other anions in water at
biological pH. This significantly enhanced fluorescence
intensity was probably caused by the nucleophilicity of the
cyanide anion and the carbonyl activation by the phenol
proton of the salicyl functional group in the dosimeter
through an intramolecular hydrogen bond.
Figure 3. (a) Fluorescence spectra of the dosimeter (10 µM) in
HEPES upon addition of 1500 equiv of various anions (from left
-
-
-
-
-
-
to right: only the sensor, CN , F , H
2
PO
4 4
, AcO , ClO , Br ,
-
-
-
-
Cl , I , NO
intensities.
3 3
, N ) (sodium salts). (b) Its relative fluorescence
chemodosimeter showed a remarkably higher selectivity for
cyanide over the other anions in water (Figure 3b). We
assume the cyanide selectivity of the dosimeter 1 is due to
the nucleophilicity of cyanide in water. The nucleophilicity
of cyanide in water seems to be the major contributor to the
high selectivity of the dosimeter 1 for cyanide, while in
DMSO, not only the nucleophilicity but also the basicity of
Acknowledgment. Support for this work from the Korea
Research Foundation (KRF-2006-312-C00592) and Seoul
R&BD is gratefully acknowledged. K.S.L. and G.H.K. thank
the Ministry of Education for the BK 21 fellowship.
Supporting Information Available: Synthetic details,
Job plot, cyanide selectivity over other anions, fluorescence
response of the dosimeter to various anions in P19 cells, and
fluorescence microplate reader images of living P19 cells in
-
-
-
2 4
anions (F , H PO , AcO ) may cause large changes in the
UV-vis spectra of the chromogenic chemodosimeter and
therefore result in less selectivity for cyanide.1 A large
increase in the fluorescence intensity could be applied to the
detection of cyanide anions by the naked eye. When the
chemodosimeter was excited at 365 nm in the presence 1500
equiv of other anions in HEPES buffer at pH 7.4, a bright
3
-
the presence of the chemodosimeter treated with CN . This
material is available free of charge via the Internet at
http://pubs.acs.org.
OL7025763
Org. Lett., Vol. 10, No. 1, 2008
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