8
hydrazine by Tl(III) to produce fluorescent Tl(I) and
reaction with arenedicarboxaldehydes to produce fluores-
Levulinate 1 was prepared by the reaction of 3-cyano-
7-hydroxycoumarin 2 with levulinyl chloride (65%, CH Cl )
(Scheme 1).
2
2
9
cent derivatives have been reported. Fluorescence signal-
ing with disruption of the internal hydrogen bonding by
10
hydrazine in a carbazolopyridinophane was also reported.
Swager et al. reported interesting trace hydrazine detec-
tion results using a turn-on type fluorescent conjugated
Scheme 1. Preparation of Levulinate Probe 1
11
polymer film.
Among the many sophisticated optical signaling sys-
tems, reactive chemical probes have received much interest
1
2
due to their specificity and cumulative signaling effects.
There are many smart reactive probe systems for the
analysis of metal ions, anions, and neutral molecules
The chromogenic signaling behavior of 3-cyano-
-hydroxycoumarin levulinate 1 was investigated in a
0% aqueous DMSO solution at pH 4.5 (acetate buffer,
0 mM). Levulinate 1 revealed moderate UVꢀvis absorp-
1
3
7
3
1
utilizing unique chemical transformations. Particularly,
deprotection of specific protecting groups has been used as
a versatile signaling tool, for example the silyl ether for
1
4
15
tion at 307 and 336 nm. Upon the interaction of 1 with
hydrazine, a prominent absorption band centered at 426 nm
developed (Figure 1). Concomitantly, a greenish yellow
color, which is a characteristic of 2, developed that allowed
a colorimetric detection of hydrazine by the naked eye. The
changes in absorption bands by the hydrazine-induced
deprotection process were remarkable and provided ratio-
metric analysisfor the transformation ofprobe1 to 2. With
fluoride, the boronate for hydrogen peroxide, the
1
benzenesulfonyl group for superoxide, the hydrazone
6
2
þ 17
2þ 18
for Cu
,
Levulinoyl ester, a versatile protecting group often
and the thioacetals for Hg
.
1
9
applied in synthetic organic chemistry, can be removed
2
0
selectively by treatment with hydrazine. Interestingly,
levulinated triphenol has been used as a hydrazine cleava-
ble chromogenic protecting group for hydroxyl groups.
Recently, we reported that levulinated resorufin could be
used as a selective chromogenic probe for the determination
2
1
100 equiv of hydrazine, the absorbance ratio A426/A336 at
the two characteristic wavelengths of 426 and 336 nm
increased over 500-fold (from 0.014 to 7.14). Other com-
mon cations and anions were relatively nonresponsive,
2
2
of sulfites. With this background for levulinates, we
devised a new hydrazine-selective signaling system. A levuli-
nate of 3-cyano-7-hydroxycoumarin was successfully
deprotected under mild conditions and acted as a selective
with A426/A values varying in a limited range between
336
2
þ 3þ
0
(
(
.019 (for Pb ) and 0.078 (for Fe ) for metal ions, 0.014
ꢀ
ꢀ
2
3
for Br ) and 0.16 (for N ) for anions, respectively
3
Figures S1 and S2, Supporting Information).
chromogenic and fluorogenic probe for hydrazine.
(
10) Brown, A. B.; Gibson, T. L.; Baum, J. C.; Ren, T.; Smith, T. M.
Sens. Actuators, B 2005, 110, 8–12.
11) Thomas, S. W., III; Swager, T. M. Adv. Mater. 2006, 18, 1047–
050.
(
1
(12) Jun, M. E.; Roy, B.; Ahn, K. H. Chem. Commun. 2011, 47, 7583–
601.
7
(
13) (a) Mohr, G. J. Anal. Bioanal. Chem. 2006, 386, 1201–1214. (b)
Cho, D.-G.; Sessler, J. L. Chem. Soc. Rev. 2009, 38, 1647–1662.
14) (a) Kim, S. Y.; Hong, J.-I. Org. Lett. 2007, 9, 3109–3112. (b)
Bhalla, V.; Singh, H.; Kumar, M. Org. Lett. 2010, 12, 628–631.
15) (a) Chang, M. C. Y.; Pralle, A.; Isacoff, E. Y.; Chang, C. J. J.
(
(
Am. Chem. Soc. 2004, 126, 15392–15393. (b) Dickinson, B. C.; Chang,
C. J. J. Am. Chem. Soc. 2008, 130, 9638–9639.
(
16) Maeda, H.; Yamamoto, K.; Kohno, I.; Hafsi, L.; Itoh, N.;
Nakagawa, S.; Kanagawa, N.; Suzuki, K.; Uno, T. Chem.;Eur. J.
007, 13, 1946–1954.
17) Kim, M. H.; Jang, H. H.; Yi, S.; Chang, S.-K.; Han, M. S. Chem.
Commun. 2009, 4838–4840.
18) Cheng, X.; Li, Q.; Qin, J.; Li, Z. ACS Appl. Mater. Interfaces
010, 2, 1066–1072.
19) Greene, T. W.; Wuts, P. G. M. Protective Groups in Organic
Synthesis, 3rd ed.; John Wiley & Sons: New York, 1999; pp 168 and 278.
20) Geurink, P. P.; Florea, B. I.; Li, N.; Witte, M. D.; Verasdonck,
2
(
(
2
(
Figure 1. UVꢀvis spectra of probe 1 in the presence of hydra-
(
ꢀ5
zine, representative metal ions, and anions. [1] = 1.0 ꢁ 10 M,
J.; Kuo, C.-L.; van der Marel, G. A.; Overkleeft, H. S. Angew. Chem.,
Int. Ed. 2010, 49, 6802–6805.
nþ
nꢀ
ꢀ3
[
hydrazine] = [M ] = [A ] = 1.0 ꢁ 10 M in a mixture of
(21) Leikauf, E.; K
o€ ster, H. Tetrahedron 1995, 51, 5557–5562.
acetate buffer (pH 4.5, 10 mM) and DMSO (3:7, v/v). Measured
after 15 min of mixing.
(22) Choi, M. G.; Hwang, J.; Eor, S.; Chang, S.-K. Org. Lett. 2010,
1
2, 5624–5627.
(
23) We tried to apply this approach to another widely used phenolic
dye resorufin. The resorufin derivative also exhibited satisfactory sig-
naling behavior toward hydrazine; however, the interference from azide
ions was significant (Figure S11, Supporting Information). On the other
hand, the 7-hydroxycoumarin derivative revealed only turn-on type
fluorescence signaling without any chromogenic behavior, which is
inferior to the present system. Zhou, Z.; Li, N.; Tong, A. Anal. Chim.
Acta 2011, 702, 82–86.
The fluorogenic signaling behavior of 1 toward hydra-
zine was measured. Probe 1 demonstrated very weak fluo-
rescence emission at 458 nm (Figure 2). Upon interaction
with hydrazine, the fluorescence intensity at 458 nm in-
creased 250-fold and the solution color, under illumination
Org. Lett., Vol. 13, No. 19, 2011
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