Sulfonamide and urea-based anions chemosensors

Article abstract of DOI:10.1016/j.dyepig.2015.03.036

The detection of anions has attracted considerable interest because of their importance in various physiological processes. In this study, two sulfonamide and urea-based compounds (1a and 1b) were successfully developed and their spectroscopic and anion recognition properties were fully investigated. These results showed that: (1) compounds showed high selectivity towards cyanide and fluoride ions in CH₃CN; (2) compounds only exhibited a large change in fluorescence in the presence of cyanide ions in CH₃CN-H₂O (95:5, v/v); and (3) compound 1b could act as a gel in dimethyl sulfoxide that transforms into a homogeneous solution upon exposure to cyanide ions. This research suggests that sulfonamide and urea can act as hydrogen-bond donors and provides an alternative approach to the design of novel anion chemosensors.

Full text of DOI:10.1016/j.dyepig.2015.03.036

Dyes and Pigments 119 (2015) 108e115
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Sulfonamide and urea-based anions chemosensors
Fang Hu, Meijiao Cao, Juanyun Huang, Zhao Chen, Di Wu, Zhiqiang Xu, Sheng Hua Liu*,
Jun Yin*
Key Laboratory of Pesticide and Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan 430079, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
The detection of anions has attracted considerable interest because of their importance in various
physiological processes. In this study, two sulfonamide and urea-based compounds (1a and 1b) were
successfully developed and their spectroscopic and anion recognition properties were fully investigated.
These results showed that: (1) compounds showed high selectivity towards cyanide and fluoride ions in
CH3CN; (2) compounds only exhibited a large change in fluorescence in the presence of cyanide ions in
CH3CNeH2O (95:5, v/v); and (3) compound 1b could act as a gel in dimethyl sulfoxide that transforms
into a homogeneous solution upon exposure to cyanide ions. This research suggests that sulfonamide
and urea can act as hydrogen-bond donors and provides an alternative approach to the design of novel
anion chemosensors.
Received 23 February 2015
Received in revised form
18 March 2015
Accepted 19 March 2015
Available online 7 April 2015
Keywords:
Sulfonamide
Urea
Hydrogen-bonding donor
Cyanide
© 2015 Elsevier Ltd. All rights reserved.
Gel
Chemosensors
1. Introduction
important to design anion chemosensors with novel topological
structures.
Biologically and environmentally important anions have played
a fundamental role in a wide range of organic and inorganic sys-
tems, and their application in sensing and anion transport has
gained considerable interest [1e21]. In addition to the develop-
ment of anion chemosensors, the binding between the chemo-
sensor and the anion involves three main types of interaction,
which include: 1) electrostatic interactions, 2) reaction-based
sensors, 3) hydrogen bonding and 4) metaleligand interactions
[22e24]. Recently, hydrogen bonding has become one of the most
frequently used interactions due to their relatively high energy, the
significant availability of H-bond donors and their strong and se-
lective binding with anions [25e27]. Among the various anion
chemosensors, amides, hydrazides, pyrroles, ureas and thioureas
are often used as hydrogen bond donors with both high affinity and
selectivity [28e30]. Sulfonamides, which are similar to amides,
have always served as a cation and thiol amino acid chemosensor
In this work, two anion chemosensors (1a and 1b), based on
both sulfonamide and urea were successfully developed and their
spectroscopic and anion recognition properties fully investigated.
Both of them show highly selective chemical signaling behavior
towards cyanide and fluoride ions in CH3CN. In particular, both
compounds only exhibited a large change in fluorescence in the
presence of cyanide ions in CH3CNeH2O (95:5, v/v). The signaling
process was confirmed using fluorescence spectroscopy and the
limit of detection for compounds 1a and 1b was 12 nM and 4 nM,
respectively. Significantly, compound 1b could act as a gel in
dimethyl sulfoxide that transforms into a homogeneous solution
upon exposure to cyanide ions. Density functional theory (DFT)
calculations and NMR titration studies suggest that both com-
pounds act as cyanide ion fluorescence chemosensors via hydrogen
bonding. Herein, we provide an alternative approach to the design
of novel anion chemosensors with high sensitivity and selectivity.
[31e34]. Currently,
a research towards anion chemosensors
combining sulfonamides has been reported. Therefore, a sulfon-
amide can also act as a hydrogen-bond donor and form intra-
molecular or intermolecular hydrogen bonds. It is therefore
2. Materials and methods
2.1. Experimental
All manipulations were carried out under an argon atmosphere
using standard Schlenk techniques, unless otherwise stated.
Tetrahydrofuran was dried with Na then distilled under vacuum. All
* Corresponding authors. Tel./fax: þ86 027 6786 7725.
E-mail addresses: chshliu@mail.ccnu.edu.cn (S.H. Liu), yinj@mail.ccnu.edu.cn
(J. Yin).
http://dx.doi.org/10.1016/j.dyepig.2015.03.036
0143-7208/© 2015 Elsevier Ltd. All rights reserved.

F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
109
reagents and starting materials were obtained from commercial
suppliers and were used without further purification. All anions for
binding experiments used tetrabutylammonium salts as sources.
Anions in CH3CN were obtained by dissolution of the anions in
CH3CN. Time course for the signaling of cyanide and fluoride ions
by compounds 1a and 1b was followed by monitoring the changes
in fluorescence intensity of the solutions at 531 nm. The concen-
trations of the probe 1a or 1b and cyanide or fluoride ion were
2.2.1.5. Synthesis of 1a. A solution of 8a (1 mmol) and Et3N
(1.5 mmol) in THF (50 mL) was cooled in an ice bath under an argon
atmosphere and 5-(dimethylamino) naphthalene-1-sulfonyl chlo-
ride was added dropwisely to the above solution. After the mixture
was stirred at room temperature, the mixture was diluted with
water and extracted with EtOAc. The organic layer was washed
with 2 N HCl, water, saturated NaHCO3 solution and brine. Then
dried over sodium sulfate, upon removed of solvent under reduced
pressure and purified on a silica gel column using dichloro-
methane/methanol (60:1) as the eluent to obtain the target com-
pound as a yellow solid in a yield of 60%, 307 mg. 1H NMR
10 mM and 10 mM, respectively, in DMSO or a mixture of DMSO and
water solution (95:5, v/v). Column chromatography was used on
silica gel (200e300 mesh). NMR spectra were analysed using an
American Varian Mercury Plus 400 spectrometer (400 MHz) and
their chemical shifts are relative to TMS. Elemental analyses (C, H,
N) were performed by the Microanalytical Services, College of
Chemistry, CCNU. Electrospray (EI) mass spectra were carried on
Firmigan Trace. UVeVis spectra were analysed using a U-3310 UV
Spectrophotometer. Fluorescence spectra were analysed using a
Fluoromax-P luminescence spectrometer (HORIBA JOBIN YVON
INC.).
(400 MHz, CDCl3):
d
ppm ¼ 2.85 (s, 6H, CH3), 3.76 (s, 6H, CH3), 3.79
(s, 3H, CH3), 6.57e6.63 (m, 4H, AreH), 6.75 (t, J ¼ 4 Hz, 1H, AreH),
7.03e7.14 (m, 3H, AreH), 7.37e7.41 (m, 2H, AreH), 7.48e7.56 (m,
2H, AreH), 8.04 (d, J ¼ 8 Hz, 1H, urea NeH), 8.39 (d, J ¼ 8 Hz, 1H,
urea NeH), 8.51 (d, J ¼ 8 Hz, 1H, amide NeH). 13C NMR (100 MHz,
CDCl3):
d
ppm ¼ 45.17, 55.78, 60.82, 97.24, 115.03, 118.26, 122.72,
122.88, 124.09, 126.76,127.24, 127.72,128.59,129.43, 129.96, 130.86,
133.31, 133.90, 134.43, 134.63, 151.77, 152.92, 153.56. Anal. calcd for
C28H30N4O6S: C, 61.08; H, 5.49; N, 10.18. Found: C, 61.00; H, 5.19; N,
2.2. Synthesis
10.28. EI MS m/z ¼ 550.43 [M]; calculated exact mass ¼ 550.19.
2.2.1. Synthesis of all new compounds
2.2.1.1. Synthesis of 3, 4a, 4b, 5a and 5b. Compounds 3, 4a, 4b, 5a
and 5b were prepared by literature methods [35].
2.2.1.6. Synthesis of 1b. A solution of 8b (1 mmol) and Et3N
(1.5 mmol) in THF (50 mL) was cooled in an ice bath under an argon
atmosphere and 5-(dimethylamino) naphthalene-1-sulfonyl chlo-
ride was added dropwisely to the above solution. After the mixture
was stirred at room temperature, the mixture was diluted with
water and extracted with EtOAc. The organic layer was washed
with 2 N HCl, water, saturated NaHCO3 solution and brine. Then
dried over sodium sulfate, upon removed of solvent under reduced
pressure and purified on a silica gel column using dichloro-
methane/methanol (90:1) as the eluent to obtain the target com-
pound as a pale yellow solid in a yield of 65%, 511 mg. 1H NMR
2.2.1.2. Synthesis of 6a, 6b, 7a and 7b. Compounds 6a, 6b, 7a and
7b were prepared by literature methods [36].
2.2.1.3. Synthesis of 8a. A solution of benzene-1, 2-diamine
(1.4 mmol) in acetone (50 mL) was cooled in an ice bath under an
argon atmosphere and 7a (0.53 mmol) in acetone (20 mL) was
added dropwisely to the above solution. This solution was stirred
for 2 h at room temperature. The formed precipitate was collected
and the crude product was washed with ice acetone, the dried solid
was recrystallized from methylene chloride to give a white solid 8a.
(400 MHz, CDCl3):
d
ppm ¼ 0.88 (t, J ¼ 4 Hz, 12H, CH2CH3), 1.44 (s,
21H, CH2CH3), 1.71e1.77 (m, 12H, CH2CH3), 2.84 (s, 6H, CH3), 3.89 (t,
J ¼ 4 Hz, 4H, CH2), 3.96 (t, J ¼ 4 Hz, 2H, CH2), 6.55 (t, J ¼ 8 Hz, 2H,
AreH), 6.68 (d, J ¼ 8 Hz, 1H, AreH), 6.68 (t, J ¼ 8 Hz, 1H, AreH),
7.03e7.09 (m, 2H, AreH), 7.11e7.13 (m, 1H, AreH), 7.21 (s, 1H,
AreH), 7.36e7.42 (m, 2H, AreH), 7.48e7.55 (m, 2H, AreH), 8.02 (d,
J ¼ 4 Hz, 1H, urea NeH), 8.38 (d, J ¼ 8 Hz, 1H, urea NeH), 8.48 (d,
Yield: 42 mg, 25%. 1H NMR (400 MHz, DMSO-d6):
d
ppm ¼ 3.60 (s,
3H, CH3), 3.74 (s, 6H, CH3), 4.77 (s, 2H, NH2), 6.57 (d, J ¼ 8 Hz, 1H,
AreH), 6.74 (d, J ¼ 8 Hz, 1H, AreH), 6.80 (s, 2H, AreH), 6.83 (d,
J ¼ 4 Hz, 1H, AreH), 7.32 (d, J ¼ 4 Hz, 1H, AreH), 7.69 (s, 1H, urea
NeH), 8.73 (s, 1H, urea NeH). 13C NMR (100 MHz, DMSO):
J
d
¼
8
Hz, 1H, amide NeH). 13C NMR (100 MHz, CDCl3):
ppm ¼ 14.07, 22.64, 26.09, 29.36, 30.25, 31.81, 45.27, 68.91, 73.50,
d
ppm ¼ 55.69, 60.21, 95.75, 115.96, 116.89, 124.01, 124.58, 124.69,
132.23, 136.34, 141.03, 152.91, 153.28. Anal. calcd for C16H19N3O4: C,
60.56; H, 6.03; N, 13.24. Found: C, 60.41; H, 5.99; N, 13.20. EI MS m/
z ¼ 317.26 [M]; calculated exact mass ¼ 317.14.
98.80, 114.90, 118.47, 122.64, 122.81, 122.99,124.04, 126.82, 127.24,
127.72, 128.65, 129.55, 130.14, 130.79, 133.89, 134.06, 134.51, 151.81,
153.12, 153.50. Anal. calcd for C49H72N4O6S: C, 69.63; H, 8.59; N,
6.63. Found: C, 69.35; H, 8.39; N, 6.60. EI MS m/z ¼ 844.97 [M];
calculated exact mass ¼ 844.52.
2.2.1.4. Synthesis of 8b. A solution of benzene-1, 2-diamine
(1.4 mmol) in acetone (50 mL) was cooled in an ice bath under an
argon atmosphere and 7b (0.53 mmol) in acetone (20 mL) was
added dropwisely to the above solution. This solution was stirred
for 2 h at room temperature. The formed precipitate was collected
and the crude product was washed with ice acetone, the dried solid
was recrystallized from methylene chloride to give a white solid 8b.
3. Results and discussion
3.1. Synthesis
Sulfonamides, which are similar to amides, serve as a hydrogen-
bond donor and can easily form intramolecular or intermolecular
hydrogen bonds. A dansyl unit was chosen as the fluorophore
because of its desirable spectroscopic properties as well as being
the smallest available fluorophore. Therefore, the signaling process
of the sulfonamide fluorescent dye could be confirmed by fluo-
rescence spectroscopy. Hence, compounds 1a and 1b bearing sul-
fonamide and urea functionality were synthesized as shown in
Scheme 1. The syntheses of compounds 1a and 1b are outlined in
Scheme 2. 5-Isocyanato-1, 2, 3-trimethoxybenzene 7a was pre-
pared using a Curtius rearrangement reaction [35]. The interme-
diate 3, 4, 5-trimethoxybenzoyl azide was unstable and easily
decomposed into its corresponding nitrene followed by rapid
Yield: 65 mg, 20%. 1H NMR (400 MHz, DMSO-d6):
d
ppm ¼ 0.84 (d,
J ¼ 8 Hz, 9H, CH3), 1.25 (s, 24H, CH2), 1.41 (d, J ¼ 4 Hz, 6H, CH2), 1.60
(t, J ¼ 4 Hz, 2H, CH2), 1.69 (t, J ¼ 4 Hz, 4H, CH2), 3.76 (t, J ¼ 8 Hz, 2H,
CH2), 3.87 (t, J ¼ 8 Hz, 4H, CH2), 4.73 (s, 2H, NH2), 6.56 (t, J ¼ 8 Hz,
1H, AreH), 6.72 (d, J ¼ 4 Hz, 3H, AreH), 6.83 (d, J ¼ 8 Hz, 1H, AreH),
7.30 (d, J ¼ 8 Hz, 1H, AreH), 7.62 (s, 1H, urea NeH), 8.60 (s 1H, urea
NeH). 13C NMR (100 MHz, DMSO):
d
ppm ¼ 13.87, 22.16, 25.68,
28.83, 29.85, 31.30, 31.38, 55.69, 68.10, 72.40, 96.80, 115.89, 116.79,
123.78, 124.36, 124.73, 131.98, 135.87, 140.85, 152.43, 153.14. Anal.
calcd for C37H61N3O4: C, 72.63; H, 10.05; N, 6.87. Found: C, 72.42; H,
9.99; N, 6.85. EI MS m/z
mass ¼ 611.47.
¼
611.71 [M]; calculated exact

110
F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
previously described method [37]. Dansyl chloride in THF was
added dropwise to a solution of 8a in the THF and NEt3 and the
resulting solution stirred at room temperature for 24 h. The pre-
cipitate formed was collected and purified using column chroma-
tography on a silica gel column to obtain the target compound as a
yellow solid in 70% yield. The synthesis procedure of 1b was similar
to that used to prepare 1a in an overall yield of 68%. All new
compounds were characterized by 1H NMR and 13C NMR spec-
troscopy, EI mass spectroscopy and elemental analysis.
Scheme 1. The structures of probe 1a and 1b.
3.2. Optical responses according to different solvent systems
migration of the aryl group in the nitrene to produce the desired
isocyanate product 7a. Compound 8a was synthesized using a
procedure based on a previously described method [27]. Iso-
cyanatobenzene 7a in acetone was added dropwise to an acetone
solution containing excess o-phenylenediamine and the resulting
solution was stirred at room temperature for 2 h. The precipitate
formed was collected, dried and recrystallized from methanol to
give compound 8a as a white solid in 60% yield. Probe 1a bearing
sulfonamide and urea functionality was synthesized using a
With probes 1a and 1b in hand, we first investigated their
spectroscopic behavior in CH3CN upon addition different anions
including CH3COꢀ2 , Fꢀ, Clꢀ, CNꢀ, NOꢀ3 , Brꢀ, Iꢀ, H2PO4ꢀ, ClOꢀ4 and
HSOꢀ4 . No obvious colorimetric change was observed by the naked
eye when the anions were added, as shown in Fig. S1. Subsequently,
we attempted to study their fluorescence properties. A selective
change in fluorescence was observed for compounds 1a and 1b in
the presence of Fe and CNe ions upon irradiation at an excitation
Scheme 2. The synthesis of probe 1a and 1b.
Fig. 1. (a), (b) Fluorescence changes and (c), (d) Photograph of the Fluorescence color changes of 1a, 1b (10
Slit: 5 nm/5 nm).
m
m) upon the addition of different anions (10 eq) in CH3CN (
l
¼ 380 nm,

F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
111
Fig. 2. (a), (b) Fluorescence changes and (c), (d) Photograph of the Fluorescence color changes of 1a, 1b (10
v) (
¼ 380 nm, Slit: 5 nm/5 nm).
mm) upon the addition of different anions (10 eq) in CH3CNeH2O (95:5, v/
l
wavelength of 380 nm. As shown in Fig. 1 and Fig. S2, when an
excess of Fe and CNe ions (10 eq) was added to 1a and 1b, obvious
fluorescence quenching was observed. Photographs showing the
changes in fluorescence color for 1a and 1b were in good agree-
ment with the spectroscopic changes. These results suggest that
compounds 1a and 1b show highly selective chemical signaling
behavior towards cyanide and fluoride ions in CH3CN.
When the solvent system was changed slightly upon the addi-
tion of 5% water, the changes in fluorescence were dramatically
different for the selectivity of 1a and 1b towards Fe and CNe ions.
As presented in Fig. 2 and Fig. S3, the significant enhancement in
fluorescence for Fe ions was observed, which could be attributed to
the favourable solvation effect of Fe ions with water. In other words,
obvious fluorescence quenching was observed with only CNe ions.
Fig. 3. (a), (b) Fluorescence titrations of 1a and 1b with different amounts of CNꢀ in CH3CNeH2O (95:5, v/v); (c), (d) Job's plot of 1a and 1b with CNꢀ ([probe] þ [CNꢀ] ¼ 10
mm) in
CH3CNeH2O (95:5, v/v) (
l
¼ 380 nm, Slit: 5 nm/5 nm).

112
F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
Fig. 4. (a) Single crystal structure of 1a; (b) The H-bond of intermolecular and intramolecular in complex 1a.
Fig. 5. 1H NMR spectra of 1a and 1b in CD3CNeD2O (95:5, v/v) upon addition of CNꢀ
.
Fig. 6. The possible binding mechanism of 1a and 1b with CNꢀ
.
Compounds 1a and 1b only exhibit a large change in fluorescence
with cyanide ions in CH3CNeH2O (95:5, v/v), which suggests that
the selectivity of 1a and 1b towards cyanide ions could be
controlled by changing the solvent.
in Fig. 3, upon the addition of CNe ions, the fluorescence intensity
decreased gradually, the association constant for CNe was calcu-
lated to be 1.25 ꢁ 105 L molꢀ1 and the limit of detection of 1a with
CNe ions calculated as 1.255 ꢁ 10ꢀ8 M. Significantly, the fluores-
cence quenching at 538 nm was linear with respect to the con-
centration of CNe ions at low concentrations (R2 ¼ 0.986) (in
Subsequently, the response of compounds 1a and 1b to CNe ions
in CH3CNeH2O (95:5, v/v) was investigated in detail. As presented

F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
113
Fig. 7. The optimized structures, LUMO, HOMO and their corresponding energy gaps of 1a and 1b with CNꢀ at B3LYP/6e31G* level, by using Gaussian 03 program.
Fig. S4). In order to understand the binding modes with CNe, Job
plot analyses were obtained. The results indicate that 1a formed a
1:1 stoichiometric complex with CNe. Similar fluorescence changes
were also obtained with a solution of 1b (in Fig. 3). Upon the
addition of CNe ions, the fluorescence intensity decreased gradu-
ally, the association constant for CNe was calculated to be
2.88 ꢁ 106 L molꢀ1 and the limit of detection of 1b with CNe ions
was calculated as 0.4 ꢁ 10ꢀ8 M. Job plot analyses were obtained and
the results indicate that 1b formed a 1:1 stoichiometric complex
with CNe. In comparison to 1a, the association constant of 1b for
CNe ions was greater with a lower limit of detection.
binding mechanism with CNe. Luckily, a single crystal of compound
1a, for X-ray diffraction analysis, was grown by slow diffusion of
hexane into a solution of 1a in dichloromethane. The solid-state
structure shown in Fig. 4 clearly suggests the presence of both
intermolecular and intramolecular H-bonds in 1a. The intra-
molecular hydrogen bond between the hydrogen atom of the sul-
fonamide group and the oxygen atom of the urea group possessed
an N … H distance of 2.324 Å. The intermolecular hydrogen bond
between the hydrogen atoms of the urea group and the oxygen
atoms of the methoxy groups has an N … H distance of 2.131 Å and
2.868 Å, respectively. The naphthalene ring and the trimethox-
ybenzene ring were nearly in a parallel position with a dihedral
angle between them of 6.91ꢂ. In addition, the dihedral angle be-
tween the naphthalene ring and benzene ring is 53.50ꢂ and the
dihedral angle between the trimethoxybenzene ring and benzene
ring is 53.36ꢂ. Subsequently, the partial 1H NMR spectra of 1a and
3.3. The sensing mechanism
Considering that stoichiometry of the hosteguest complex be-
tween 1a or 1b and CNe was 1:1, we tried to understand their
Fig. 8. The response of 1b (6 mg/mL) in DMSO under the cyanide anion.

114
F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
1b upon addition of CNe ions in CH3CNeH2O (95:5, v/v) were ac-
quired, as shown in Fig. 5. Upon addition of CNe ions, the resonance
of the protons in the urea group of 1a displayed a downfield shift
when compared to those for 1a in the absence of CNe ions as a
result of the formation of hydrogen bonding between NH groups
and CNe. Similarly, the resonance of the proton in the sulfonamide
group of 1a displayed a slight upfield shift. The resonance of the
protons in the naphthalene ring displayed both downfield and
upfield shifts, which were similar to those observed for protons on
the benzene rings. Similar proton resonance changes were also
obtained in the 1H NMR spectra of 1b in CH3CNeH2O (95:5, v/v) (in
Fig. 5). These results suggest that 1a and 1b act as cyanide fluo-
rescence sensors via hydrogen bonding. The possible binding
mechanism of both compounds with CNe ions is presented in Fig. 6.
In order to further investigate the binding mode of 1a or 1b with
CNe ions, DFT calculations at the B3LYP/6e31G* level using the
Gaussian 03 program were used. As presented in Fig. 7, when
compared with the optimized structure for 1a, upon the addition of
CNe the cavity becomes smaller after binding with CNe. The
hydrogen atoms in the urea and sulfonamide group interact with
the CNe ion, which was consistent with our experimental obser-
vations. The LUMO of 1a-CNe was distributed over the sulfonamide
group and the HOMO of 1a-CNe was distributed over the urea
group. The energy level gap was 3.57 eV. Similarly, when compared
with the optimized structure for 1b, upon the addition of CNe, the
cavity becomes smaller after binding with CNe. The hydrogen
atoms in the urea and sulfonamide groups interact with the CNe ion
due to the formation of hydrogen bonding between the cyanide ion
and NH groups on the urea and sulfonamide units. The LUMO
orbital of 1b-CNe was distributed over the sulfonamide group and
the HOMO orbital of 1b-CNe was distributed over the urea group.
The energy level gap was 3.64 eV. So, we propose that the binding
mode of the proton on the urea and sulfonamide groups of 1a and
1b with CNe was accomplished, which was consistent with the
observations from our 1H NMR spectroscopy studies.
Acknowledgments
We acknowledge financial support from the National Natural
Science Foundation of China (21272088, 21472059, 21402057), the
Program for Academic Leader in Wuhan Municipality
(201271130441), the Scientific Research Foundation for the
Returned Overseas Chinese Scholars, the Natural Science Founda-
tion of Hubei Province (2013CFB207) and the Central China Normal
University (CCNU14A05009, CCNU14F01003).
Appendix A. Supplementary material
Supplementary data related to this article can be found at doi:
10.1016/j.dyepig.2015.03.036.
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3.4. The gel properties of 1b
Compound 1b can act as a gel in DMSO. By placing a small
quantity (6.0 mg) of 1b in a vial, adding DMSO (1.0 mL), heating the
suspension until complete dissolution and then allowing the so-
lution to cool to room temperature, an obvious fluorescence
quenching of 1b was observed in DMSO upon the addition 10 eq
CNe (Fig. S5). More importantly, the response of gel 1b towards the
cyanide anions in DMSO led to easy-to-discern changes in the
fluorescence color. As shown in Fig. 8, the fluorescence color of gel
1b was green and when exposed to cyanide ions the gel of 1b
transformed into a homogeneous solution with obvious fluores-
cence quenching. These results suggest that 1b could serve as a
cyanide sensor not only in solution but also as a gel.
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4. Conclusion
In summary, two sulfonamide bearing compounds were suc-
cessfully developed and their spectroscopic and anion recognition
properties fully investigated. The results showed that both com-
pounds show high selectivity towards cyanide and fluoride ions in
CH3CN. In particular, they only exhibited a large change in fluo-
rescence with cyanide in CH3CNeH2O (95:5, v/v). More impor-
tantly, compound 1b can act as a gel in DMSO that can transform
into a homogeneous solution upon exposure to cyanide ions. This
research suggests that sulfonamide and urea can act as a hydrogen-
bond donor and provides an alternative approach to the design of
novel anion chemosensors. Further work will focus on anion che-
mosensors with novel topological structures.

F. Hu et al. / Dyes and Pigments 119 (2015) 108e115
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