Ratiometric Signaling of Hypochlorite by the Oxidative Cleavage of Sulfonhydrazide-Based Rhodamine-Dansyl Dyad

Article abstract of DOI:10.1021/acs.inorgchem.5b01284

(Figure Presented). A reaction-based probe 1 for hypochlorite signaling was designed by the conjugation of two fluorophores, rhodamine and dansyl moieties, by the reaction of rhodamine B base with dansylhydrazine. Probe 1 exhibited pronounced hypochlorite-selective chromogenic and fluorescent signaling behavior over other oxidants used in practical applications, such as hydrogen peroxide, peracetic acid, and ammonium persulfate, as well as commonly encountered metal ions and anions. Signaling was attributed to the hypochlorite-induced oxidative cleavage of the sulfonhydrazide linkage of the probe. In particular, favorable ratiometric fluorescence signaling was possible by utilizing the emissions of the two fluorophores. A detection limit of 1.13 × 10^-6 M (0.058 ppm) was estimated for the determination of hypochlorite. A paper-based test strip was prepared and was used as a semiquantitative indicator for the presence of hypochlorite in aqueous solutions. The probe was also successfully applied for the determination of hypochlorite in practical tap water samples.

Full text of DOI:10.1021/acs.inorgchem.5b01284

Article
pubs.acs.org/IC
Ratiometric Signaling of Hypochlorite by the Oxidative Cleavage of
Sulfonhydrazide-Based Rhodamine−Dansyl Dyad
Hyo Jin Lee, Min Jeoung Cho, and Suk-Kyu Chang*
Department of Chemistry, Chung-Ang University, Seoul 156-756, Republic of Korea
*
S Supporting Information
ABSTRACT: A reaction-based probe 1 for hypochlorite signaling was designed by the conjugation of two fluorophores,
rhodamine and dansyl moieties, by the reaction of rhodamine B base with dansylhydrazine. Probe 1 exhibited pronounced
hypochlorite-selective chromogenic and fluorescent signaling behavior over other oxidants used in practical applications, such as
hydrogen peroxide, peracetic acid, and ammonium persulfate, as well as commonly encountered metal ions and anions. Signaling
was attributed to the hypochlorite-induced oxidative cleavage of the sulfonhydrazide linkage of the probe. In particular, favorable
ratiometric fluorescence signaling was possible by utilizing the emissions of the two fluorophores. A detection limit of 1.13 ×
−6
10
M (0.058 ppm) was estimated for the determination of hypochlorite. A paper-based test strip was prepared and was used as
a semiquantitative indicator for the presence of hypochlorite in aqueous solutions. The probe was also successfully applied for the
determination of hypochlorite in practical tap water samples.
INTRODUCTION
For the selective signaling of HOCl, a number of
chromogenic and luminescent chemodosimeters have been
developed. These designed probes are principally based on its
strong oxidative property. Representative examples of the
sensors developed include the well-controlled HOCl-induced
■
Hypochlorous acid (HOCl) is an important reactive oxygen
species in biology; it plays several fundamental roles in living
systems, such as antimicrobial activity in the natural defense
system as well as protein unfolding and aggregation. In
addition, it has been widely employed in various industrial
5
1
oxidation of oximes of hydroxycoumarin and fluorescein to
8
aldehydes, oxidation of boron dipyrromethene (BODIPY)-
applications, such as in the paper and textile industries fo2r
based diphenyl selenide and diphenyl telluride into selenoxide
bleaching and to control slime and algae in piping and tubes.
9
,10
and telluroxide, respectively, and the oxidative conversion of
Furthermore, HOCl has also been applied as a safe sanitizer for
the treatment of drinking water and sanitization of swimming
BODIPY-appended p-methoxyphenol into its quinone deriva-
11
3
tive. On the other hand, the ring-opening and oxidation of
pools. In the guideline of the World Health Organization, the
12
rhodamine-based thioether as well as the cleavage of the ether
moiety having photoelectron transfer quenching of the 4-amino
or 4-hydroxylphenyl ether moiety of rhodamine derivatives
minimum residual concentration of free chlorine in drinking-
water at the point of delivery should be 0.2 mg/L to ensure safe
water supply by sanitizing certain bacteria and other microbes
13
4
have been utilized for the imaging of HOCl in various cells. In
in tap water. Because of its biological and environmental
14
addition, rhodamine-based thiospirolactone and hydroxamic
importance, it is imperative to develop highly sensitive and
selective optical signaling probes for HOCl or hypochlorite, its
ionized form. In recent years, various fluorescent probes have
been devised for the signaling of HOCl. However, most of the
sensors and probes are targeting for the imaging of HOCl in
15
acid have also been successfully used for the detection of
HOCl in various chemical and biological systems, such as in
living human neutrophil cells and zebrafish. In particular, a
5
5
number of rhodamine hydrazide-based HOCl probes,
1
6
6
designed from rhodamine hydrazide itself to simple
derivatives functionalized with the phenylhydrazo and
biological media, such as in live-cell imaging. On the contrary,
17
only a few studies on the optical sensing of HOCl using
functional dyes for real applications, such as for the analysis of
tap and swimming pool water, have recently attracted research
Received: June 8, 2015
7
interest.
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.5b01284
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Article
1
8
naphthoylhydrazo groups, have been reported. The trans-
used for practical applications was investigated by UV−vis and
fluorescence measurements. As shown in Figure 1, in a 90%
formations of rhodamine−thiosemicarbazide into rhodamine-
1
,3,4-oxadiazole as well as benzoylhydrazide of rhodamine−
coumarin conjugates were also successfully used for the
19,20
ratiometric signaling of HOCl.
The sulfonhydrazide functionality, which is utilized as a
useful protecting group for carbonyl-containing compounds in
synthetic organic chemistry, is known to be readily cleaved by
2
1
HOCl. However, to the best of our knowledge, this valuable
reaction or processes related to the hydrolysis of sulfonhy-
drazide have not been used for the design of any probe for
HOCl. In this study, we designed a hypochlorite-selective
reaction-based probe based on a rhodamine−dansyl dyad by
utilizing the selective oxidative cleavage of the sulfonhydrazide
2
2
linkage group. We used the rhodamine−dansyl dyad as the
signal transducer and the sulfonhydrazide linkage as the
triggering switch, which responds to the presence of
hypochlorite. The designed probe exhibited prominent
chromogenic and ratiometric fluorogenic signaling behavior
toward hypochlorite.
Figure 1. UV−vis spectra of 1 in the presence of oxidants typically
used for practical applications. (inset) Photograph of 1 in the absence
−
−6
−5
and presence of OCl . [1] = 5.0 × 10 M, [oxidant] = 5.0 × 10
in a 90% aqueous acetonitrile solution buffered at pH 8.0 (phosphate,
0 mM). PAA = peracetic acid, TBHP = tert-butyl hydroperoxide, and
M
1
RESULTS AND DISCUSSION
■
APS = ammonium persulfate.
Synthesis of Rhodamine−Dansyl Dyad 1. Sulfonhy-
drazide probe 1 based on a rhodamine−dansyl dyad was
prepared by the reaction of rhodamine B base with
dansylhydrazine 2 (Scheme 1). Dansylhydrazine was obtained
aqueous acetonitrile solution buffered at pH 8.0 with a
phosphate buffer (final concentration = 10 mM), probe 1
exhibited no significant absorption above 450 nm. However,
after treatment with 10 equiv of various oxidants, only OCl−
exhibited a prominent absorption band at 555 nm (Figures 1
and S1, Supporting Information). The color of the solution
concomitantly changed from colorless to pink, which was
readily detected without any device. Other oxidants used for
practical applications, such as H O , peracetic acid (PAA), tert-
Scheme 1. Preparation of Rhodamine−Dansyl Dyad-Based
Sulfonhydrazide Probe 1
2
2
−
butyl hydroperoxide (TBHP), O , Oxone, persulfate, percar-
2
bonate, and perborate, did not induce any noticeable response.
−
The OCl -selective signaling of 1 could be illustrated by the
enhancement in absorbance, expressed by A/A at 555 nm,
0
where A and A denote the absorbance in the presence and
0
absence of analytes, respectively. Hypochlorite induced a 31-
fold enhancement in absorbance at 555 nm, while other
oxidants exhibited negligible changes (Figure S1, Supporting
Information).
However, probe 1 revealed a moderate-intensity emission
centered at 494 nm, mainly attributed to the dansyl
fluorophore. As expected, the rhodamine moiety did not
exhibit any emission, attributed to the ring-closed lactam
structure of 1. However, in the presence of 10 equiv of oxidants
typically used for practical applications, the emission profile
by treating dansyl chloride with hydrazine following a literature
procedure for the preparation of 4-nitrobenzenesulfonhydra-
2
3
−
zide. Attempts to synthesize probe 1 by treating rhodamine B
hydrazide with dansyl chloride were unsuccessful. The
rhodamine and dansyl moieties were used for designing a
reaction-based probe with the aim of constructing a more
versatile ratiometric system for the selective signaling of
hypochlorite using two fluorophores. Similar signaling could
be realized by the use of other simple sulfonhydrazides such as
p-toluenesulfonyl hydrazide-based dyad; however, the resulting
signal obtained is a simple off−on-type fluorescence change.
With the probe currently designed, the changes in the
characteristic emissions of both rhodamine and dansyl
fluorophores could be utilized to obtain more desirable
ratiometric signaling behavior.
dramatically changed exclusively with OCl (Figures 2 and S2,
Supporting Information). In fact, the isosbestic point of probe 1
was 460 nm. However, when probe 1 was excited at 460 nm,
dansyl fluorophore did not exhibit any emission signaling
(Figure S3, Supporting Information). To realize ratiometric
signaling using both dansyl and rhodamine fluorophores of 1,
the probe was excited at 400 nm instead of its isosbestic point.
Under illumination with a UV lamp, the solution color changed
from green to orange. The emission band of probe 1 at 494 nm
completely disappeared, and a new strong band was observed at
578 nm, attributed to the ring-opened form of the rhodamine
fluorophore. With this change, the emission intensity ratio at
two characteristic wavelengths 578 and 494 nm I578/I494
dramatically increased (130-fold) from 0.32 to 42.1. To obtain
more efficient signaling conditions, we surveyed the signaling
Colorimetric and Fluorescence Signaling Behavior of
. The signaling behavior of probe 1 toward oxidants typically
1
B
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Inorganic Chemistry
Article
spectrum, a diagnostic peak was observed at m/z = 442.2 for
rhodamine B base (C H N O ).
28
30
2
3
−
Probe 1 showed satisfactory selectivity toward OCl over
other common metal ions and anions (Figures 4, S8 (for metal
ions), and S9 (for anions), Supporting Information). The
surveyed metal ions of alkali, alkaline earth, and transition metal
ions did not exhibit any response. Notably, probe 1 did not
exhibit any response toward Cu2+ and Hg under the signaling
conditions. Typically, rhodamine hydrazide-based sensors and
2+
25
probes exhibit significant responses to these two ions. In fact,
the p-toluenesulfonyl hydrazide analogue of 1 is known to
2+
exhibit Cu -selective signaling behavior in aqueous acetoni-
26
trile. Anions also did not exhibit significant responses to 1−
(
inset of Figure 4). This prominent selectivity of 1 for OCl
was also confirmed by the plot of the fluorescence intensity
ratio at 578 and 494 nm (I578/I494): it varied between 0.28 (for
Figure 2. Changes in the fluorescence spectra of 1 in the presence of
oxidants typically used for practical applications. (inset) UV-
−
2+
2+
illuminated photograph of 1 in the absence and presence of OCl .
Ca ) and 0.33 (for Hg ) for the tested metal ions and
−6
−5
−
−
[
1] = 5.0 × 10 M, [oxidant] = 5.0 × 10 M in a 90% aqueous
between 0.30 (for ClO ) and 0.34 (for Br ) for the surveyed
4
acetonitrile solution buffered at pH 8.0 (phosphate, 10 mM). λ = 400
ex
anions.
nm.
−
For the selective determination of OCl in practical samples,
it is imperative to investigate the OCl signaling of 1 in the
−
−
behavior of 1 toward OCl in various solvents with different
presence of common metal ions or anions as background. With
the tested metal ions, the changes in the fluorescence intensity
ratio I(1+metal ion+OCl−)/I(1+OCl−) at 578 nm varied in a narrow
water percentages (Figures S4−S6, Supporting Information).
Among the tested solvents, signaling in dimethyl sulfoxide
2+
2+
(
DMSO) was not possible due to the scavenging effect of
range between 0.96 (for Pb ) and 1.01 (for Cd ) (Figure 5).
With the surveyed anions, the fluorescence signaling of OCl−
was also not affected by the presence of anions: the ratio
24
DMSO for hypochlorite. After systematic survey, we found
that probe 1 exhibited relatively optimized OCl -selective
−
signaling behavior in terms of selectivity and ratiometrically
analyzable behavior in 90% aqueous acetonitrile buffered at pH
I(1+anion+OCl−)/I(1+OCl−) at 578 nm marginally fluctuated between
−
−
0.99 (for Br ) and 1.03 (for NO ) (Figure S10, Supporting
3
8
.0 with a phosphate buffer.
Selective signaling for OCl is attributed to the oxidative
Information). These observations clearly imply that probe 1
could be applied for the determination of OCl in chemical and
−
−
−
hydrolysis of sulfonhydrazide 1 (Scheme 2). In fact, the OCl -
induced hydrolysis of sulfonyl hydrazone as a protecting group
has already been reported in synthetic organic chemistry.
However, we could not find any study on a similar OCl -
induced reaction used for sulfonhydrazides. Upon reaction with
OCl , probe 1 first decomposed to rhodamine B base and
dansyl acid. The rhodamine B base thus generated was found to
be stable under the experimental conditions. However, dansyl
acid was found to decompose further, caused by the strong
oxidation property of OCl (Figure S7, Supporting Informa-
tion). The proposed signaling process of 1 toward OCl was
confirmed by H NMR and mass measurements. Figure 3
shows the H NMR spectrum of the purified signaling product
of 1 after treatment with OCl ; the characteristic resonances of
rhodamine B base were clearly observed. As previously
described, after signaling with OCl , the relatively stable
environmental analytes, where various metal ions and anions
are frequently present as coexisting ions.
21
−
The signaling of OCl was completed within 1 min after
−
sample preparation, as evidenced by the time-dependent
absorption changes at 555 nm (Figure S11, Supporting
Information). In addition, to test the applicability of the
−
−
probe for the determination of OCl in tap water under various
circumstances that are expected for the water supply systems of
different regions and seasonal changes, temperature-dependent
signaling behavior of 1 toward OCl− was investigated. As
shown in Figure S12 (Supporting Information), there was no
−
−
1
−
discernible variation in the signaling rate of probe 1 for OCl in
1
the measured temperature range (10−50 °C). Furthermore, the
stability of probe 1 was satisfactory: probe 1 exhibited no
noticeable responses after 5 h of sample preparation. Effects of
−
−
−
pH on the OCl signaling of 1 were also verified by monitoring
rhodamine B base could be recovered, while dansyl acid was
the changes in absorbance of 1 at 555 nm as a function of the
decomposed further and could not be identified. In the mass
pH of the measuring solution. As shown in Figure S13
−
Scheme 2. Signaling Process for OCl of Rhodamine−Dansyl Dyad 1
C
DOI: 10.1021/acs.inorgchem.5b01284
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Inorganic Chemistry
Article
1
−
Figure 3. Partial H NMR spectrum of 1 alone, 1 in the presence of OCl , and rhodamine B base. [1] = [rhodamine B base] = 5.0 mM in CDCl .
3
−
The spectrum of 1 + OCl was obtained after the purification of the signaling product by passing it through a short silica plug.
followed by slow decrease as the pH increased to 10. From this
plot, we confirmed that the OCl− signaling of probe 1 is
optimized in a 90% aqueous acetonitrile solution phosphate
buffered at pH 8.0.
The quantitative signaling behavior of OCl− by 1 was
investigated by fluorescence titration. The fluorescence
intensity measured at 494 nm decreased, while the emission
−
at 578 nm steadily increased with increase in [OCl ] (Figure
6
). Ratiometry using the fluorescence intensity ratio at 578 and
Figure 4. Changes in the fluorescence intensity ratio (I578/I494) of 1 in
−6
the presence of common metal ions or anions. [1] = 5.0 × 10 M,
−
n+
n−
−5
[
OCl ] = [M ] = [A ] = 5.0 × 10 M in a 90% aqueous acetonitrile
solution buffered at pH 8.0 (phosphate, 10 mM). λex = 400 nm.
−
Figure 6. Concentration-dependent ratiometric signaling of OCl by
−
6
−
−5
1
. [1] = 5.0 × 10 M, [OCl ] = 0−5.0 × 10 M in a 90% aqueous
acetonitrile solution buffered at pH 8.0 (phosphate). λ = 400 nm.
ex
4
94 nm (I578/I494) was useful for the construction of a
calibration plot. From concentration-dependent signaling
measurements, a detection limit of 1.13 × 10− M (0.058
6
−
ppm) was estimated for the determination of OCl in a 90%
aqueous acetonitrile.
27
Figure 5. Competitive fluorescence signaling of OCl− by 1 in the
−
Signaling of OCl in Practical Samples. Probe 1 was
−6
−
presence of various metal ions as background. [1] = 5.0 × 10 M,
applied for the signaling of OCl in real tap water samples.
First, the possibility of visualizing OCl in distilled water was
−
n+
−5
[
OCl ] = [M ] = 5.0 × 10 M in a 90% aqueous acetonitrile
−
solution buffered at pH 8.0 (phosphate). λex = 400 nm.
tested using a test strip (Figure 7). For this purpose, a filter
paper was impregnated with an acetonitrile solution of probe 1,
affording a filter-paper-based test strip for the sensing of OCl .
−
(Supporting Information), signaling became more efficient as
the pH of the measuring solution increased from pH 4.5 to 8.0,
When this test strip was treated with distilled water containing
D
DOI: 10.1021/acs.inorgchem.5b01284
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Inorganic Chemistry
Article
ions and anions. In addition, the probe exhibited pronounced
selectivity toward hypochlorite over other oxidants typically
used for practical applications, such as hydrogen peroxide,
peracetic acid, and ammonium persulfate. The designed probe
could be used as a selective signaling tool for the detection of
hypochlorite at micromolar concentrations. In addition, the
practical application for the monitoring of hypochlorite in tap
water using a test strip and solution color change was
investigated.
Figure 7. Photographs of the test strip image under (a) daylight and
−
(
b) UV illumination of 1 in the presence of varying amounts of OCl .
−
−3
[
OCl ] varied from 0 to 1.0 × 10 M in distilled water.
EXPERIMENTAL SECTION
■
−
General. Rhodamine B base, dansyl chloride, phosphorus oxy-
chloride, hydrazine monohydrate, and sodium hypochlorite were
purchased from Aldrich Chemical Co. All other chemicals and solvents
varied amounts of OCl , spots of pronounced colors were
observed, which can be easily discernible by the naked eye as
well as under UV illumination. This observation implies that
probe 1 could be useful as a preliminary, convenient sensing kit
for measuring the concentration of hypochlorite in practical
1
were obtained from commercial sources and used as received. H
13
NMR (300 and 600 MHz) and C NMR (75 and 150 MHz) spectra
were recorded on Varian Gemini 2000 and Varian VNS NMR
spectrometers using residual solvent signals as reference. UV−vis
spectra were recorded on a Scinco S-3100 spectrophotometer
equipped with a Peltier temperature controller. Fluorescence spectra
were obtained on a PTI QuantaMaster steady-state spectrofluor-
ometer. Mass spectra were recorded on a Micromass Autospec mass
spectrometer. Elemental analysis data were obtained using a Thermo
Electron Corporation Flash EA 1112 analyzer. Column chromatog-
raphy was performed with silica gel (Merck, 240 mesh).
−
samples. Next, the signaling of OCl in tap water using the
probe 1 was examined. As shown in Figure 8, only tap water
Preparation of Dansylhydrazine 2. Dansylhydrazine 2 was
obtained by treating dansyl chloride with hydrazine following a
literature procedure for the preparation of 4-nitrobenzenesulfonhy-
drazide. A solution of dansyl chloride (0.27 g, 1.0 mmol) in
tetrahydrofuran (10 mL) was added to an aqueous hydrazine
monohydrate solution (0.23 mL, 5.0 mmol). The progress of the
reaction was monitored by thin-layer chromatography, and after the
completion of the reaction, 20 mL of ethyl acetate was added to the
reaction mixture. The resulting solution was washed three times using
Figure 8. Photographs of the solution under (a) daylight and (b) UV
2
3
illumination of 1 in the varying practical samples. [1] = 5.0 × 10−6 M,
in a 90% aqueous acetonitrile solution buffered at pH 8.0 (phosphate).
(
#.1) distilled water, (#.2) tap water, (#.3) commercial mineral water
(
Sam Da Soo, Jeju, Korea), (#.4) purified water (from a water purifier,
CHP-570L, WoongJin, Korea).
1
0 mL of distilled water. The organic part was separated and
evaporated under reduced pressure. The crude product was purified by
sample exhibited prominent chromogenic and fluorogenic
signaling behavior. Other practical samples, such as commercial
mineral water (Sam Da Soo, Jeju, Korea) and purified water
column chromatography (silica gel, CH Cl ) to yield dansylhydrazine
2
2
1
2
(0.25 g, 95%) as a yellowish white powder. H NMR (600 MHz,
CDCl ) δ 8.60 (d, J = 8.5 Hz, 1H), 8.30 (dd, J = 7.3, 1.1 Hz, 1H), 8.28
3
(from a water purifier, CHP-570L, WoongJin, Korea), did not
(
1
d, J = 8.5 Hz, 1H), 7.56 (m, 2H), 7.20 (d, J = 7.4 Hz, 1H), 6.01 (s,
induce any noticeable response. By the simple addition of a
stock solution of the probe 1 to tap water analytes, changes
discernible by the naked eye were observed in the analytes
containing residual hypochlorites under measurement con-
ditions. In addition, we conducted the standard addition
method to determine the concentration of hypochlorite in tap
water (Figure S14, Supporting Information). The concentration
13
H), 2.89 (s, 6H). C NMR (150 MHz, CDCl ) δ 152.1, 131.9.
3
131.5, 130.7, 130.0, 129.9, 128.8, 123.1, 118.7, 115.5, 45.4. HRMS:
+
+
+
(FAB ); m/z calcd for C H N O S [M] : 265.0885, found
1
2
15
3
2
265.0880.
Preparation of Rhodamine−Dansyl Dyad 1. First, rhodamine B
base (0.44 g, 1.0 mmol) was added to a solution of POCl (15 mL),
3
and the solution was refluxed for 6 h. After the completion of the
reaction, the mixture was evaporated under reduced pressure, and the
residue was dissolved in dichloromethane. Next, dansylhydrazine 2
of hypochlorite in tap water was found to be 2.15 × 10−6
M
(
0.11 ppm), which is in good agreement with the result
(0.27 g, 1.0 mmol) and triethylamine (1 mL) were added to the above
obtained by using the standard N,N-diethyl-p-phenylenedi-
dichloromethane solution, and the resulting mixture was stirred for 12
h. Then, the reaction mixture was washed three times using 10 mL of
distilled water. Finally, the organic part was separated and evaporated
under reduced pressure, and the crude product was purified by column
chromatography (silica gel, CH Cl /CH OH = 29:1, v/v) to yield
28
amine (DPD) method (0.12 ± 0.01 ppm). On the basis of
this observation, we believe that using the designed probe 1, the
presence and semiquantitative determination of hypochlorite in
tap water as well as possibly in other drinking water supply
systems could be rapidly achieved.
2
2
3
1
rhodamine−dansyl dyad (1) (0.37 g, 54%) as a pale white powder. H
NMR (600 MHz, CDCl ) δ 8.34 (d, J = 8.4 Hz, 1H), 7.94−7.85 (m,
3
CONCLUSION
2H), 7.64 (dd, J = 7.3, 1.3 Hz, 1H), 7.47−7.40 (m, 2H), 7.31 (dd, J =
■
8
1
2
.6, 7.5 Hz, 1H), 7.15−7.09 (m, 2H), 6.97−6.92 (m, 1H), 6.70 (s,
H), 6.36 (d, J = 8.6 Hz, 2H), 6.19 (dd, J = 8.8, 2.6 Hz, 2H), 5.73 (s,
H), 3.30 (q, J = 7.2 Hz, 8H), 2.90 (s, 6H), 1.18 (t, J = 7.1 Hz, 12H).
A new hypochlorite-selective reaction-based dual-signaling
probe by the conjugation of rhodamine B base with
dansylhydrazine was developed. Rhodamine−dansyl dyad was
used as the ratiometric signal transducer, and the sulfonhy-
drazide linkage was used as the reaction-based switch, which
responds to the presence of hypochlorite. The probe exhibited
highly selective hypochlorite-induced chromogenic and fluo-
rescent responses in the presence of coexisting common metal
13
C NMR (150 MHz, CDCl ) δ 168.3, 153.0, 152.2, 151.4, 148.6,
3
1
1
1
34.1, 133.7, 130.0, 129.4, 129.4, 129.3, 128.6, 128.3, 128.0, 127.3,
24.4, 123.4, 122.9, 119.6, 114.6, 107.6, 104.3, 97.6, 66.6, 45.6, 44.2,
+
+
+
2.7. HRMS: (FAB ); m/z calcd for C H N O S [M + H] :
40
44
5
4
690.3114, found 690.3119. Anal. Calcd for C H N O S: C, 69.64; H,
40
43
5
4
6.28; N, 10.15. Found: C, 69.32; H, 6.36; N, 10.22%.
E
DOI: 10.1021/acs.inorgchem.5b01284
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Competitive Signaling Experiments for Metal Ions and
Anions. The competitive signaling behavior of probe 1 was measured
in a mixture of phosphate buffer (pH 8.0) and acetonitrile (1:9, v/v).
Test solutions were prepared by placing the stock solution of metal ion
or anion (0.01 mM, 15 μL), the stock solution of 1 in acetonitrile (0.5
(5) (a) Chen, X.; Tian, X.; Shin, I.; Yoon, J. Chem. Soc. Rev. 2011, 40,
4783−4804. (b) Yang, Y.; Zhao, Q.; Feng, W.; Li, F. Chem. Rev. 2013,
113, 192−270.
(6) Chan, J.; Dodani, S. C.; Chang, C. J. Nat. Chem. 2012, 4, 973−
984.
−
mM, 30 μL), and OCl solution (0.01 mM, 15 μL) consecutively in a
(7) (a) Lou, X.; Zhang, Y.; Li, Q.; Qin, J.; Li, Z. Chem. Commun.
n+
vial. The final concentrations of 1, buffer, metal ion or anion (M or
2
011, 47, 3189−3191. (b) Wang, Q.; Liu, C.; Chang, J.; Lu, Y.; He, S.;
n−
−
−6
−2
−5
A ), and OCl were 5.0 × 10 M, 1.0 × 10 M, 5.0 × 10 M, and
Zhao, L.; Zeng, X. Dyes Pigm. 2013, 99, 733−739. (c) Hwang, J.; Choi,
−5
5
.0 × 10 M, respectively. For fluorescence measurements, an
M. G.; Bae, J.; Chang, S.-K. Org. Biomol. Chem. 2011, 9, 7011−7015.
excitation wavelength of 400 nm was used.
(
8) (a) Yu, S.-Y.; Hsu, C.-Y.; Chen, W.-C.; Wei, L.-F.; Wu, S.-P. Sens.
1
H NMR Measurement of the Signaling Product. To obtain
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1
hypochlorite, the H NMR spectrum of the purified signaling product
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for a mixture of 1 and hypochlorite was recorded. The H NMR
−
3
−3
spectra of 1 (5.0 × 10 M) and rhodamine B base (5.0 × 10 M)
1
were obtained in chloroform-d (0.6 mL). The H NMR spectrum of
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the signaling product was obtained after the purification by a short
silica plug of the signaling product of probe 1 (22 mg, 0.05 mmol)
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aqueous acetonitrile solution.
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Application of Test Strip for Hypochlorite Determination. A
laboratory filter-paper-based test strip was prepared for the
determination of hypochlorite. First, filter paper (Whatman #.3) was
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dried in atmosphere. Then, solutions with varied concentrations of
hypochlorite (0−5.0 mM) were dropped on the prepared test paper.
After these dots of solution dried for few minutes in air, pink colored
and strongly fluorescent orange colored spots were developed. Images
of the test paper under daylight and UV-lamp light were taken using a
digital camera. To indicate the presence and semiquantitatively
determine hypochlorite in tap water, a stock solution of probe 1 (10
μL, 1.0 mM, acetonitrile) in phosphate buffer (0.1 mL, pH 8.0, 10
mM) was added to tap water analytes, and tap water was further added
to adjust the final volume to 10 mL. The absorption and fluorescence
data of the resulting solutions were measured.
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ASSOCIATED CONTENT
■
(20) Zhang, Y.-R.; Chen, X.-P.; Zhang, J.-Y.; Yuan, Q.; Miao, J.-Y.;
*
S
Supporting Information
Zhao, B.-X.; Shao, J. Chem. Commun. 2014, 50, 14241−14244.
(
(
21) Ho, T.-L.; Wong, C. M. J. Org. Chem. 1974, 39, 3453−3454.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.5b01284.
22) In this paper, we used hypochlorite instead of hypochlorous acid
for HOCl because more predominant form of hypochlorous acid in
pH 8.0 is hypochlorite ion (pK of HOCl = 7.53).
a
UV−vis absorbance ratio (A/A ), fluorescence spectra,
time course plot, and pH dependency of probe 1 as well
as NMR spectra of 1 and 2. (PDF)
0
(23) Backes, G. L.; Neumann, D. M.; Jursic, B. S. Bioorg. Med. Chem.
2014, 22, 4629−4636.
(24) Lopez, F. C.; Shankar, A.; Thompson, M.; Shealy, B.; Locklear,
D.; Rawalpally, T.; Cleary, T.; Gagliardi, C. Org. Process Res. Dev. 2005,
9
, 1003−1008.
AUTHOR INFORMATION
Corresponding Author
E-mail: skchang@cau.ac.kr.
■
(25) Kim, H. N.; Lee, M. H.; Kim, H. J.; Kim, J. S.; Yoon, J. Chem.
Soc. Rev. 2008, 37, 1465−1472.
*
(26) Hu, Z.-Q.; Wang, X.-M.; Feng, Y.-C.; Ding, L.; Lu, H.-Y. Dyes
Pigm. 2011, 88, 257−261.
Notes
(
27) Shortreed, M.; Kopelman, R.; Kuhn, M.; Hoyland, B. Anal.
The authors declare no competing financial interest.
Chem. 1996, 68, 1414−1418.
(
Standard Methods for the Examination of Water and Wastewater, 21st
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ACKNOWLEDGMENTS
This study was supported by the Korea Research Foundation of
the Korean Government (NRF-2013R1A1A2A10004615).
■
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DOI: 10.1021/acs.inorgchem.5b01284
Inorg. Chem. XXXX, XXX, XXX−XXX