A highly selective and sensitive dual-channel chemosensor for cyanide based on sulfahydrazone derivative

Article abstract of DOI:10.1080/10426507.2016.1192623

A colorimetric and fluorescent cyanide probe bearing naphthol and sulfahydrazone groups has been designed and synthesized. This structurally simple probe displays a rapid response and high selectivity for cyanide in DMSO/EtOH (v/v = 2:8) solution. The addition of CN^? to the sensor p-toluenesulfonyl-2-hydroxy-1-naphthylhydrazone (L3) induced a remarkable color change from pale-yellow to yellow, and green fluorescence changed to yellow. The ¹H NMR titration and DFT calculations suggested that the selective sensing process is based on a nucleophilic addition reaction of cyanide to imine. Test strips based on sensor L3 were fabricated, which could act as a convenient and efficient test kit to detect CN^? for “in-the-field” measurements.

Full text of DOI:10.1080/10426507.2016.1192623

Phosphorus, Sulfur, and Silicon and the Related Elements
ISSN: 1042-6507 (Print) 1563-5325 (Online) Journal homepage: http://www.tandfonline.com/loi/gpss20
A highly selective and sensitive dual-channel
chemosensor for cyanide based on sulfahydrazone
derivative
Yan-Li Leng, Jian-Hui Zhang, Qiao Li, You-Ming Zhang, Qi Lin, Hong Yao & Tai-
Bao Wei
To cite this article: Yan-Li Leng, Jian-Hui Zhang, Qiao Li, You-Ming Zhang, Qi Lin, Hong Yao &
Tai-Bao Wei (2016): A highly selective and sensitive dual-channel chemosensor for cyanide
based on sulfahydrazone derivative, Phosphorus, Sulfur, and Silicon and the Related Elements,
DOI: 10.1080/10426507.2016.1192623
To link to this article: http://dx.doi.org/10.1080/10426507.2016.1192623
Accepted author version posted online: 25
May 2016.
Published online: 25 May 2016.
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Date: 04 June 2016, At: 10:55

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A highly selective and sensitive dual-channel chemosensor for cyanide based on
sulfahydrazone derivative
Yan-Li Leng a,b , Jian-Hui Zhang b, Qiao Li a, You-Ming Zhang a, Qi Lin a, Hong Yao a, Tai-
Bao Weia,*
a
Key Laboratory of Eco-Environment-Related Polymer Materials of Ministry of Education,
Gansu Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering,
Northwest Normal University, Lanzhou, 730070, China
b Department of Applied Chemical Engineering, Lanzhou Resources & Environment Voc-Tech
College, Lanzhou, Gansu, 730021, China
*Email: weitaibao@126.com
Abstract
A colorimetric and fluorescent cyanide probe bearing naphthol and sulfahydrazone groups has
been designed and synthesized. This structurally simple probe displays a rapid response and high
selectivity for cyanide in DMSO/EtOH (v/v=2:8) solution. The addition of CN- to the sensor p-
toluenesulfonyl -2- hydroxy -1- naphthyl hydrazone (L3) induced a remarkable color changed
from pale-yellow to yellow and the green fluorescence changed to yellow. The 1H NMR titration
and DFT calculations suggested that the selective sensing process is based on a nucleophilic
addition reaction of cyanide to the imine. Test strips based on sensor L3 were fabricated, which
could act as a convenient and efficient test kit to detect CN- for “in-the-field” measurements.
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Keywords
Cyanide(CN-); Chemosensor; Nucleophilic addition; DFT.
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Introduction
The specific detection of anions is an ever-active field due to their crucial roles in industrial,
biological, and environmental processes.1-6 Among all anions, cyanide is commonly used in
industries such as precious metal mining, metal plating shops, steel mills, and plastic and
fertilizer plants，but is of particular interest as it is highly toxic when absorbed through the
lungs, skin, and gastrointestinal tract, leading to vomiting, loss of consciousness, and eventual
death.7,8 Given its acute toxicity, wide availability in massive amounts, and in light of increasing
terrorist activity, there is a pressing need for fast, accurate detection of cyanide. 9-11
Recently, colorimetric and fluorescent sensing techniques enabling the determination of
cyanide are of tremendous significance, due to their high sensitivity, simplicity, and real-time
detection. The cyanide ion is nucleophilic enough to form stable complexes with various
molecules and materials, and thus many detection methods using this complex formation have
been reported.12-15
In view of these and as a part of our research interests in the molecular recognition,16-21 we
report a simple to synthesize, yet sensitive, and selective cyanide anion sensor L3, which was
synthesized as shown in Scheme 1. The strategy employed in the design of this sensor is as
follows: firstly, we introduced hydroxyl and imine group to the sensor molecule as binding sites
to detect CN- by hydrogen-bonding interactions and nucleophilic addition. Secondly, in order to
achieve high sensitivity for CN-, the fluorescent signal report mode has been adopted, because
the fluorescent sensors often provide higher sensitivity than other optic sensors. Therefore, 2-
hydroxy-1-naphthaldehyde was selected as the fluorescent signal reporting unit in light of its
high photo stability, large stokes shift, and emission in the visible region. Furthermore, we
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employed the sulfonyl group as electron withdrawing group in sensor L3 to increase the
nucleophilicity of the imine group. The DFT calculations of the reaction process further
conformed that the mechanism is nucleophilic addition of CN- to the imine group of the sensor
L3.
Results and discussion
The ability of L3 to act as a highly selective cyanide anion sensor was first investigated by
UV-vis spectroscopy. As shown in Figure 1(a), free L3 shows low and high energy absorption
bands at 331 (ε = 1.7×104 M-1 cm-1) and 408 nm (ε = 4.0×104 M-1 cm-1) respectively, when 50
equiv. of CN- was added to the DMSO/EtOH (v/v=2:8) solution of sensor L3, the strong band at
408 nm is red-shifted to 458 nm (ε = 3.3×104 M-1 cm-1). To validate the selectivity of sensor L3,
-
-
-
the same tests were applied using F-, Cl-, Br-, I-, AcO-, H2PO4 , HSO4 , ClO4 , SCN- anions, and
none of these anions induced any significant changes in the UV-vis spectra of the sensor. The
calculation of the difference at λmax (458 nm) before and after adding of these anions (Figure 1(b))
confirmed that only the addition of CN- can lead to notable color change from pale-yellow to
yellow (Figure 1(a), insert). The selective florescence response of L3 to cyanide anion was also
investigated (Figure 2(a)). The emission of L3 appeared at the maximum emission wavelength
was 510 nm in DMSO/EtOH (2:8, v/v) solution when excited at λex= 450 nm. When 50 equiv. of
CN- was added to the solution of sensor L3, the strong fluorescence emission band at 510 nm is
red-shifted to 560 nm. To validate the selectivity of sensor L3, the same tests were also applied
-
-
-
using F-, Cl-, Br-, I-, AcO-, H2PO4 , HSO4 , ClO4 , SCN- anions, and none of these anions induced
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any significant changes in the fluorescent spectrum of the sensor. The calculation of the emission
intensity ratio (F560/F510) before and after adding of these anions (Figure 2(b)) confirmed that
only the addition of CN- can lead to notable color change from green to yellow (Figure 2a, insert).
The binding affinities of L3 and CN- have been examined through the titration experiments.
As shown in Figure 3, upon gradual addition of CN- (0-186.4 equiv.) the strong absorption band
of L3 centered at 408 nm gradually decreased with a red shift of 50 nm to appear at 458 nm.
Notably, two isosbestic points appeared at 370 nm and 434 nm indicate the existence of more
than one species in the medium. Similarly, in the florescence titration spectrum (Figure 4), while
the concentration of CN- was increased (0-10.56 equiv.), the emission maximum at 510 nm
gradually decreased with a red shift of 50 nm to appear at 562 nm. Meanwhile, an isosbestic
point appeared at 553 nm. The Job plot between L3 and CN- was implemented, demonstrating a
1:1 stoichiometry for the L3 and CN-, as shown in Figure 5.22
1
To explore the sensing mechanism of sensor L3 to CN-, the H NMR titration were
investigated, which illustrated the characteristic structural changes occurring upon interaction
1
with CN-. As shown in Figure 8, before the addition of cyanide anion, the H NMR chemical
shifts of the N-H (Hb), O-H (Ha) and -(Hc) HC=N- protons on L3 were at δ 10.04, 12.92, 9.62
ppm, respectively. Upon the addition of 0.1 equiv. of cyanide anion, the new signal (Hc) was
found at δ 7.10 ppm and shifted to upfield with gradual addition CN-. Simultaneously, the
resonance for O-H (Ha) and -(Hc) HC=N- protons disappeared, and aromatic protons H shifted to
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upfield to different extent, while the signal at δ 8.69-8.71 (d, J=8.0) ppm (aromatic proton Hd)
shifted to downfield. Meanwhile, the protons Hb show a large upfield shift from δ 10.04 to δ 9.68
ppm. These observations obviously indicate that the cyanide anion is added to the imine group in
sensor L3. A plausible mechanism for the formation of L3-CN- has been proposed in Scheme 2.
Further to support our assumptions, geometry optimization were performed for the probe L3
and L3-CN- adduct with B3LYP/6-311+G (2d, p) level using a suite of Gaussian 03 programs.23
The optimized structures of L3 and L3-CN- are shown in Figure 9. L3 has a conjugated bridge (-
C=N-) between naphthalene group, and the dihedral angle of -N-N=C-Ar is 175.8º. The reaction
product L3-CN- has a saturated bridge (-N-C-), and the dihedral angle of -N-N-C-Ar is -173.4º.
This structural difference leads to a significant difference in π-conjunction between L3 and L3-
CN-. The reaction proceed channel is exothermic by 129.9 kJ·mol-1 on the ground potential
energy surface, which shows that the nucleophilic addition of probe L3 with CN- is easy to carry
out. Thus, both the theoretical and experimental observations corroborate the possible mode of
interaction between probe and cyanide anion.
Conclusion
In summary, we have presented a facile, low-cost, and efficient sulfahydrazone derivate of a
highly selective chemosensor for CN-. The sensor gives an immediate response to the cyanide
anion both by visible and fluorescence color changes. Cyanide anion is detectable by its
nucleophilic attack toward the imine group and the mechanism of the reaction was investigated
1
by various methods (such as H NMR spectroscopic titration, ESI-MS and DFT calculations).
Moreover, test strips based on sensor L3 were fabricated, which could serve as practical
colorimetric to detect CN- for “in-the-field” measurements and did not require any additional
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equipment but just by virtue of “dip-sticks” approach. We believe the test strips could act as a
convenient and efficient CN- test kit. More applications of this efficient strategy might be found
in extended occasions of this concept, such as with combinations of anion-neutral molecules.
Experimental section
Materials and physical methods
Fresh double distilled water was used throughout the experiments. All other reagents and
solvents were commercially available at analytical grade and were used without further
1
purification. H NMR spectra were recorded on a Bruker AvanceIII 400 MHz spectrometer at
400 MHz. Chemical shifts are reported in parts per milliom (ppm) downfield from
tetramethylsilane (TMS, δ scale with solvent resonances as internal standards). UV-vis spectra
were recorded on a Shimadzu UV-2550 spectrometer. Photoluminescence spectra were
performed on a Shimadzu RF-5301 fluorescence spectrophotometer. Melting points were
measured on an X-4 digital melting-point apparatus (uncorrected). Elemental analyses were
performed by Thermo Scientific Flash 2000 organic elemental analyzer. The Supplemental
Materials contains sample characterization data of L3 and computational details (Figures S 1 – S
5)
Synthesis of sensor L3
p-Toluenesulfonohydrazide was prepared following the reported procedure.24
Synthesis of Compound L3:
p-Toluenesulfonohydrazide (0.37 g, 2 mmol) and 2-Hydroxy-1-naphthaldehyde (0.34 g, 2
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mmol) were combined in absolute ethanol (15 mL). The solution was stirred under reflux
conditions for 4 hours, after cooling to room temperature, the yellow precipitate was filtrated,
washed with absolute ethanol three times, then recrystallized from DMF-EtOH to obtain a
yellow powdery product.
L3: yield: 68% (m.p. >300℃), 1H-NMR (DMSO-d6, 400 MHz) δ 12.92 (s 1H, OH), δ 10.04 (s
1H, NH), 9.62 (s 1H, =CH), 8.69-8.71 (d, 1H, J=8.0, ArH), 8.08-8.10 (d, 1H, J=8.0, ArH) 7.97-
7.99 (d, 1H, J=8.0, ArH), 7.33-7.68 (m, 5H, ArH), 2.56 (s 3H, CH3). ESI-MS m/z: (M+H)+ Calcd
for C18H16N2O3S: 340.09; Found 339.05. Anal. Calcd. For C18H16N2O3S: C, 63.51; H, 4.74; N,
8.23; Found C, 63.42; H, 4.66, N, 8.29.
General procedure for UV-vis experiments
All the UV-vis experiments were carried out in DMSO/EtOH (v/v=2:8) solution on a
Shimadzu UV-2550 spectrometer. Any changes in the UV-vis spectra of the synthesized
compound were recorded on addition of tetrabutylammonium salts while keeping the ligand
concentration constant (2.0×10-5 M) in all experiments. Tetrabutylammonium salt of anions (F-,
-
-
-
Cl-, Br-, I-, AcO-, H2PO4 , HSO4 , ClO4 , SCN- and CN- using their sodium salts water solution as
the sources) were used for the UV-vis experiments.
General procedure for Fluorescence spectra experiments
All the fluorescence spectroscopy was carried out in DMSO/EtOH (v/v=2:8) solution on a
Shimadzu RF-5301 spectrometer. Any changes in the fluorescence spectra of the synthesized
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compound were recorded on addition of tetrabutylammonium salts while keeping the ligand
concentration constant (2.0×10-5 M) in all experiments. Tetrabutylammonium salt of anions (F-,
-
-
-
Cl-, Br-, I-, AcO-, H2PO4 , HSO4 , ClO4 , SCN- and CN- using their sodium salts water solution as
the sources) were used for the fluorescence experiments.
General procedure for 1H NMR experiments
1
For H NMR titrations, the solution of L3 was prepared in DMSO-d6 and the appropriate
concentrated solution of guest was prepared in double distilled water. Aliquots of the two
solutions were mixed directly in NMR tubes.
Funding
This work was supported by the National Natural Science Foundation of China (No.
21262032, 21161018 and 21574104). The Program for Chang jiang Scholars and Innovative
Research Team in University of Ministry of Education of China (No. IRT1177), the Natural
Science Foundation of Gansu Province (No. 1010RJZA018), the Youth Foundation of Gansu
Province (No. 2011GS04735) and NWNU-LKQN-11-32.
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Figure 1 (a) Absorbance emission data for probe L3 and each of the various anions in the
DMSO/EtOH (v/v=2:8) solution. Inset: Color changes observed for L3 upon the addition of F-,
-
-
-
Cl-, Br-, I-, AcO-, H2PO4 , HSO4 , ClO4 , CN-, SCN- (50 equiv., respectively) in DMSO/EtOH
(v/v=2:8). (b) Normalized of UV-vis absorbance spectra of L3 (c=2×10-5 M) upon addition of
different anions.
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Figure 2 (a) Fluorescence spectra (λex=450 nm) of L3 (c=2×10-5 M) after addition of 50 equiv.
various anions. Inset: Visual fluorescence emissions of L3 upon the addition of F-, Cl-, Br-, I-,
-
-
-
AcO-, H2PO4 , HSO4 , ClO4 , CN-, SCN- (50 equiv., respectively) in DMSO/EtOH (v/v=2:8) on
excitation at 365 nm using UV lamp at rt. (b) Normalized change in fluorescence intensity
(λex=450 nm) of L3 (c=2×10-5 M) after addition of 50 equiv. various anions. All date represent
the fluorescence intensity ratio F560/F510.
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Figure 3 Absorbance spectra of L3 in the presence of different concentration of CN- in
DMSO/EtOH (v/v=2:8). Inset: A plot of absorbance depending on the concentration of CN- in
the range from 0 to 186.4 equiv. The detection wavelength was 458 nm.
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Figure 4 Fluorescence spectra of L3 in the presence of different concentration of CN- in
DMSO/EtOH (v/v=2:8). Inset: A plot of fluorescence intensity depending on the concentration of
CN- in the range from 0 to 10.56 equiv. The detection wavelength was F562nm/F510nm
.
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Figure 5 The Job’s plot examined between CN- and L3, indicating the 1:1 stoichiometry for L3
and CN- clearly.
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Figure 6 Effect of pH on the absorbance spectra (410 nm) of L3+CN- (50 equiv.) from 2 to 13 in
DMSO/EtOH/H2O (v/v/v=2:7:1) solution.
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Figure 7 Effect of pH on the fluoresence spectra (510 nm) of L3+CN- (50 equiv.) from 2 to 13 in
DMSO/EtOH/H2O (v/v/v=2:7:1) solution.
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1
Figure 8 Partial H NMR spectra of L3 (0.01mol/L, DMSO-d6) and in the presence of varying
amounts of CN-.
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Figure 9 Optimized structures of L3 and L3-CN-.
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Figure 10 Photographs of L3 on test papers (a) left: only L3, right: after immersion into
DMSO/EtOH (v/v=2:8) solutions with CN-, (b) left: only L3, right after immersion into
DMSO/EtOH (v/v=2:8) solutions with CN- under irradiation at 365 nm.
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O
O
O
S
O
S
.
H2NNH2 H2O
S
NHNH2
Cl
HO
NH N CH
Benzene, 60-70oC
O
O
EtOH, reflux
O
HO
L3
Scheme1 Synthesis of L3.
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O
CN-
O
H
N
O
S NH
O
C
S NH
N
CH
Hc
HO
Ha
nucleophilic addition
Hb
NC
O
H
Hd
r
e
f
s
n
a
r
t
n
o
t
-O
C
o
r
O
p
H
N
S NH
O
NC
H
Scheme 2 A possible sensing mechanism of the sensor L3 to CN-.
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