A colorimetric and fluorescence sensor based on biphenolic-dansyl derivative for specific fluoride ion detection

Article abstract of DOI:10.1080/10610278.2021.1950720

2?-(2-((4-(methylthio)phenyl)amino)-2-oxoethoxy)-[1,1?-biphenyl]-2-yl 5(dimethyl amino)naphthalene-1-sulphonate (1) was synthesised and used as a F^? ion sensor. The selectivity of sensor 1 with various anions (F^?, Cl^?, Br<

Full text of DOI:10.1080/10610278.2021.1950720

Supramolecular Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gsch20
A colorimetric and fluorescence sensor based on
biphenolic-dansyl derivative for specific fluoride
ion detection
Sitthichok Mongkholkaew, Apisit Songsasen, Weekit Sirisaksoontorn &
Boontana Wannalerse
To cite this article: Sitthichok Mongkholkaew, Apisit Songsasen, Weekit Sirisaksoontorn &
Boontana Wannalerse (2021): A colorimetric and fluorescence sensor based on biphenolic-
dansyl derivative for specific fluoride ion detection, Supramolecular Chemistry, DOI:
10.1080/10610278.2021.1950720
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SUPRAMOLECULAR CHEMISTRY
https://doi.org/10.1080/10610278.2021.1950720
A colorimetric and fluorescence sensor based on biphenolic-dansyl derivative for
specific fluoride ion detection
Sitthichok Mongkholkaew, Apisit Songsasen, Weekit Sirisaksoontorn and Boontana Wannalerse
Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok,
10900, Thailand
ABSTRACT
ARTICLE HISTORY
Received 4 February 2021
Accepted 27 June 2021
2
ʹ-(2-((4-(methylthio)phenyl)amino)-2-oxoethoxy)-[1,1ʹ-biphenyl]-2-yl 5(dimethyl amino)naphtha-
−
lene-1-sulphonate (1) was synthesised and used as a F ion sensor. The selectivity of sensor 1
−
−
−
−
−
−
3 6 5 2 4
with various anions (F , Cl , Br , CH COO , C H COO and H PO ) in DMSO was evaluated by
1
KEYWORDS
1
H NMR, UV-visible and fluorescence study. For H NMR, an amide proton of sensor 1 disappeared
Anion sensor; deprotonation
−
−
due to the deprotonation reaction upon addition of F ion. On the contrary, the proton signal of
HF
reaction; F ion detection
−
−
2
emerged at 16.11 ppm. Upon addition of F ion, sensor 1 showed a new absorption band at
3
00 nm and the solution turned colourless. For fluorescence response, sensor 1 exhibited the
−
enhancement of emission intensity at 434 nm with slight blue shift when titrated with F ion. These
−
results suggest that sensor 1 possessed high sensitivity and selectivity towards F ion detection. In
addition, the sensor 1 test strip coated on TLC plates and filter papers were demonstrated for
−
specific detection F ion.
1
. Introduction
Nowadays, anions play an important roles in many
applications, such as catalytic, biological, environmen-
tal and industrial processes. The selectivity and sensi-
tivity of anion sensors depend on the size, shape,
charge and basicity strength of the anions [1–5].
The molecule sensors for anion detection were devel-
oped with different functional groups, including
amide, urea, thiourea and guanidinium. The interac-
tions between sensors and anions are hydrogen
bonding, anion-pi and electrostatic forces. Among
various anions, fluoride ion is one of the most neces-
sary anions because of its role in the dental care and
treatment for osteoporosis [6–8]. On the other hand,
the excessive accumulation of fluoride ion in the
human body can lead to severe disorders and dis-
eases [9–11]. Hence, numerous methods, such as
chromatography and electrophoresis, have been
developed to monitor fluoride ion in biological and
environmental samples [2,10]. However, these
CONTACT Boontana Wannalerse
fscibnw@ku.ac.th
Kasetsart University, Chatuchak, Bangkok 10900, Thailand
Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science,
Supplemental data for this article can be accessed here.
©
2021 Informa UK Limited, trading as Taylor & Francis Group

2
S. MONGKHOLKAEW ET AL.
instrumental techniques are quite complicated, time-
consuming and require expensive tools.
FT-IR and elemental analysis. In addition, the complexa-
−
tion study of sensor 1 with F ion was investigated by
1
In the challenge to fluoride ion detection, the fluor-
escence sensor has been widely used as an alternative
tool for anion recognition. Many conditions for fluoride
ion sensing modulate through UV-visible absorption and
fluorescence spectral change due to molecular aggrega-
tion, transformation and translocation [7–10]. The dansyl
fluorophore could provide high fluorescent and quan-
tum yield with high sensitivity when responding to the
specific anion [11]. Recently, several studies have
reported on the synthesis of novel fluorescent dansyl-
based sensors for anion detection. Miao et al. [11] pre-
pared a sensor based on a C-linked peptidocalix-4 arene
functionalised with four l-alanine and dansyl units,
which possessed high selectivity to fluoride ion. Chen
et al. [12] reported a new fluorescent chemosensor of
tetra-sulphonamide derivative bearing two dansyl
groups that exhibited strong binding interaction with
fluoride ion through the deprotonation complexation.
Herein, we report the synthesis of a new sensor, 2ʹ-
H- NMR, UV–visible and fluorescence spectroscopy.
Moreover, the sensor 1 coated on TLC (Thin Layer
Chromatography) plate and filter paper for F ion detec-
tion was also investigated.
−
2. Materials and methods
2
.1 General
1
13
H- and C-NMR spectra were collected on a Bruker
Avance 3 HD 400 MHz Nuclear Magnetic Resonance
(NMR) spectrometer. Elemental analysis (CHNS/O) was
TM
performed on a Thermo Scientific FLASH 2000.
Fluorescence spectra were recorded using an Agilent
8000 spectrophotometer. Mass spectra were obtained
on an Agilent 1100 Series LC/MSD Trap spectrometer.
All reagents were purchased from Sigma-Aldrich and
used without further purification.
(
2-((4-(methylthio)phenyl)
amino)-2-oxoethoxy)-[1,1ʹ-
biphenyl]-2-yl 5-(dimethylamino)naphthalene-1-sulpho-
nate (1), containing a 4-(methylthio) aniline derivative as
a binding site and dansyl moiety as a fluorophore. The
2.2 Synthesis of sensor 1
The synthesis of sensor 1 is shown in Scheme 1.
2
-chloro-N-(4-(methylthio) phenyl)acetamide (com-
1
13
sensor 1 was characterised by H NMR, C-NMR, ESI-MS,
pound S1) was prepared by following the literature [13].
Scheme 1. Synthesis pathway of sensor 1.

SUPRAMOLECULAR CHEMISTRY
3
2
.2.1. 2-((2ʹ-hydroxy-[1,1ʹ-biphenyl]-2-yl)oxy)-
N-(4-(metylthio)phenyl)acetamide (compound S2)
,2-biphenol (1.07 g; 5.75 mmol) and potassium car-
3. Results and discussion
.1 Design of the sensor 1 structure
3
2
bonate (1.19 g; 8.61 mmol) were mixed and stirred in
The structure of sensor 1 mainly consisting of
a biphenolic skeleton connecting with dansyl and
2-chloro-N-(4-(methylthio)phenyl)acetamide derivatives
was a rigid one that yielded a good optical signal change
upon binding to anions. For the purpose of binding
mechanism, an acidic proton of the –NH amide group
was deprotonated by strong basic anion. Deprotonating
of sensor 1 may induce the delocalised electrons within
the molecules, resulting in a significant change of colori-
metric and fluorescence emission signals.
CH CN (20 mL). The compound S1 (1.86 g;
3
7
.81 mmol) in CH CN was slowly added to the solu-
3
tion. The mixture was stirred and refluxed at 150°C
under N atmosphere for 10 h. The reaction mixture
2
was poured into water and extracted with CH Cl2
2
(
three times). The organic layer was purified by col-
umn chromatography using 9:1 CH Cl /EtOAc as an
2
2
eluent, affording a light yellow solid (0.30 g, 15%). M.
1
p. 174–176°C. H NMR (400 MHz, CDCl ): δ 2.10 (s,
3
3
1
1
1
1
6
H), 4.64 (s, 2 H), 6.93 (m, 2 H), 7.02 (m, 2 H), 7.10 (m,
H), 7.20 (m, 3H), 7.31 (m, 4 H), 8.10 (d, 1H), 9.02 (s,
For the synthesis of sensor 1, there were three main
steps as shown in Scheme 1. 4-thiomethyl aniline and
chloroacetyl chloride were used as starting com-
pounds. The mechanism of compound S1 is
nucleophilic substitution. It was found that the com-
pound S1 has a sharp singlet proton peak of CH2
group as a characteristic peak. Then, compound S2
was obtained by the condensation reaction of com-
pound S1 and biphenol by using K CO as a base.
1
3
H). C NMR (100 MHz, CDCl ): δ 166.5, 154.5, 153.3,
3
37.0, 132.8, 132.2, 131.3, 130.0, 129.6, 128.5, 127.2,
27.0, 125.4, 123.3, 121.7, 123.0, 116.9, 116.6, 113.0,
−
1
8.2, 18.7. FT-IR (KBr, cm ) ν = 3314 (N-H), 3160
(
(
O-H), 2926 (C-H), 1653 (C = O), 1530 (C = C), 1276
C-O) Element Analysis for C H NO S (%): C 69.02,
2
1
19
3
H 5.24, N 3.83 found C 69.11, H 5.18, N 3.84. MS: m/z
calculated for C H NO S+Na ([M+ Na ]), 388.10;
found, 388.0961.
2
3
+
+
The percent yield was quite low because the com-
2
1
19
3
1
pound S2 was a minor product. For H NMR spectrum,
the methylene proton peak shifted to 4.64 ppm and
aromatic protons shited towards downfield, indicating
a compound S2 formation. Lastly, the coupling reac-
tion of compound S2 with dansyl chloride was
2
.2.2 Sensor 1
Compound S2 (0.30 g; 0.77 mmol), dansyl chloride
0.17 g; 0.63 mmol) and potassium carbonate (0.14 g;
.01 mmol) were combined and refluxed at 150°C in
CH CN (15 mL). After refluxing under N atmosphere
(
1
refluxed at 150°C in CH CN solvent to obtain sensor
3
1
as a major product. The asymmetric structure of
3
2
sensor 1 consists of 4-methythio aniline as a binding
site of anion and dansyl moiety as a signalling unit.
for 8 h, the reaction mixture was poured into water
and extracted with CH Cl (three times). The organic
2
2
layer was dried with anhydrous Na SO . The resulting
2
4
product was purified by column chromatography
using 9:1 CH Cl /EtOAc as an eluent, affording
3
.2 Anion sensing properties of sensor 1 using
2
2
1
H NMR studies
1
a yellow solid of sensor 1 (0.10 g, 21.28%). H NMR,
1
3
1
−3
C NMR and ESI-MS spectra are shown in Figure S1,
H NMR spectra of sensor 1 (5 × 10 M) with different
1
−
−
−
−
−
−
S2 and S3. M.p. 138–140°C H NMR (400 MHz, DMSO-
anions (F , Cl , Br , H PO , CH COO and C H COO )
2 4 3 6 5
d6): δ 2.44 (s, 3H), 2.84 (s, 6 H), 4.45 (s, 2 H), 6.62 (t,
were studied in DMSO-d as shown in Figure 1. In the
6
2
7
H), 6.80 (d, 1H), 7.00 (t, 1H), 7.22 (m, 4 H), 7.42 (m,
H), 7.86 (t, 2 H), 8.46 (d, 1H), 9.38 (s, 1H). C NMR
case of fluoride ion, the NH peak of sensor 1 disappeared
1
3
via deprotonation reaction [14–16]. Meanwhile, the tri-
−
(
100 MHz, DMSO): δ 165.9, 153.5, 147.5, 134.9, 134.0,
plet peak of HF2 species was found at 16.11 ppm as
1
1
1
2
32.5, 132.4, 132.0, 131.7, 131.4, 130.3, 129.8, 129.6,
29.2, 128.8, 128.0, 127.5, 125.8, 123.7, 123.1, 121.7,
20.3, 119.7, 115.7, 113.2, 111.4, 67.2, 60.5, 45.7, 29.8,
shown in Figure S4. In addition, the CH proton peak
2
shifted towards downfield from 4.45 to 4.59 ppm due to
a decrease in electron density. The aromatic protons of
sensor 1 also shifted upfield and downfield due to the
−
1
1.1, 16.8, 14.2 FT-IR (KBr, cm ) ν 3395 (N-H), 2917
−
−
(
(
(
C-H), 1693 (C = O), 1530 (C = C), 1368 (S = O), 1286
C-O), 858 (S-O). Element analysis for C H N O S
%): C 66.22, H 5.34, N 4.44 found C 66.34, H 5.07,
anisotropic effect. In the case of other anions (Cl , Br , H
2
−
−
−
PO , CH COO and C H COO ), the NH peak of sensor 1
3
3
30
2
5 2
4
3
6 5
was moved slightly downfield due to weak hydrogen
bonding. The chemical shifts of aromatic protons
remained unchanged due to the weak interaction
+
+
N 4.66. MS: m/z calcd for C H N O S -H ([M-H ]),
5
3
3 30 2 5 2
99.17; found, 599.1632.

4
S. MONGKHOLKAEW ET AL.
1
−3
−
−
−
−
Figure 1. H NMR spectra of sensor 1 (A) in DMSO-d (5 × 10 M) upon addition of 0.02 M of F (B), Cl (C), Br (D), H PO (E), CH3
6
2
4
−
−
COO (F), C H COO (G).
6
5
−4
−
Figure 2. UV-visible absorption spectra of sensor 1 (1 × 10 M) in DMSO upon addition of F ion in the range of 0–0.13 M.
between sensor 1 and other anions. These results sug-
gest that sensor 1 had high selectivity towards fluoride
ion, which is ascribed to a small, strong basicity and high
3.3 Anion sensing properties of sensor 1 using
UV-visible studies
The sensing performance of sensor 1 towards anions
was investigated by monitoring the spectral changes in
−
charge density of the F ion compared to other anions.

SUPRAMOLECULAR CHEMISTRY
5
dimethyl sulfoxide (DMSO). As seen in Figure 2, two
absorption bands were observed at 270 and 360 nm,
respectively, for sensor 1. Upon incremental addition of
F ion, the absorbance at 270 and 360 nm was decreased
and at the same time a new shoulder peak at 300 nm
gradually evolved. This result suggests the presence of
a deprotonated form of sensor 1 [17–19] due to the
binding interaction of sensor 1 against fluoride ion. For
−
−
−
−
−
other anions (Cl , Br , H PO , CH COO and C H COO ),
2
4
3
6 5
−
the absorbance at 270 and 360 nm was slightly
decreased and no shoulder peak was observed because
of the weak hydrogen bonding interaction between
−4
−
−
−
−
4
Figure 3. UV-visible absorption spectra of sensor 1 (1 × 10 M) in the presence of 0.13 M of various anions (F , Cl , Br , H PO , CH
3
2
−
−
COO , C H COO ) in DMSO.
6
5
Figure 4. The absorbance at 300 nm for sensor 1 with various anions.

6
S. MONGKHOLKAEW ET AL.
−
3
−
−
−
Figure 5. Colour change of sensor 1 (5 × 10 M) in DMSO-d upon addition of 0.02 M of various anions: sensor 1 (A), F (B), Cl (C), Br
6
−
,
−
−
(
D), H PO4 (E), CH COO (F) and C H COO (G).
2 3 6 5
treated with fluoride ion and other competing anions. It
is clearly seen that sensor 1 possessed high selectivity
towards fluoride ion and its sensing performance was
not interfered by other anions.
sensor 1 and the anions. Figure 3 and Figure 4 show that
sensor 1 gave a significant enhancement in absorbance
at 300 nm upon addition of F ion, but sensor 1 with
−
other anions exhibited the similar range in absorbance
compared to pure sensor 1 in DMSO. Moreover, sensor 1
displayed a colour change from yellow to colourless with
3.4 Anion sensing properties of sensor 1 using
fluorescence studies
−
the presence of F ion as shown in Figure 5. On the
contrary, the solution colour of sensor 1 remained yel-
The sensing performance of sensor 1 against anions in
DMSO were evaluated by fluorescence titration. The two
fluorescence emissions of sensor 1 were observed at 440
and 564 nm. In the titration with F ion, the emission
band at around 434 nm was enhanced with a notable
blue shift; meanwhile, an emission band at 564 nm was
low upon addition of other anions.
−
The selectivity study of sensor 1 to F ion under the
competitive condition was further investigated. The
result in Figure 6 shows that there was no significant
change in absorbance at 300 nm when sensor 1 was
−
−4
−
Figure 6. The absorbance at 300 nm of sensor 1(1 × 10 M) in the presence of F and other competing anions in DMSO.

SUPRAMOLECULAR CHEMISTRY
7
as shown in Figure S6. The detection limit of sensors 1
−
with F ion measured by fluorescence titration at 564 nm
as previously reported [23] was found to be 18 μM. These
−
results demonstrate that sensors 1 could detect F ion at
low concentration level. Moreover, the sensing perfor-
−
mance of sensor 1 in detecting F ion was compared to
other molecular sensors summarised in Table 1.
3
.5 Application for visual detection of fluoride ion
on TLC plate
For the extensive applicability of sensor 1, test strips
−
4
were prepared by immersing sensor 1 (5 × 10 M) on
the TLC plate and filter paper in DMSO. In Figure 9, it was
found that sensor 1 gave the colorimetric response to F
−
5
Figure 7. Fluorescence emission spectra of sensor 1 (1 × 10
−
−
M) in DMSO upon addition of F ion in the range of 0–
−
4
ion at the concentration of 0.05 M. The sensor 1 dis-
played a distinct change in colour on the TLC plate from
green to blue and on the filter paper from brown to blue.
The sensor 1-coated on the TLC plate and filter paper
can be used as an efficient and convenient tool for rapid
2
.67 × 10 M.
−
decreased (Figure 7), suggesting the presence of
a deprotonated form of sensor 1 [12,20,21]. Under UV
light at 365 nm, sensor 1 with the presence of F ion
displayed the colour change from orange-yellow to blue.
In the case of other anions, the emission band at 440 nm
slightly changed and, at 564 nm, was decreased in
Figure S5. There was no colour change observed upon
addition of other anions in Figure 8.
detection of F ion.
−
4. Conclusion
The new sensor 1 based on a biphenolic-dansyl deriva-
tive has been achievably synthesised. The binding beha-
−
viour of sensor 1 in detecting F ion was predominantly
1
evidenced by UV-visible, fluorescence and H NMR tech-
The association constant obtained from the non-
linear fitting was calculated to be 6.86 × 10 M [22]
niques. For the visual detection, sensor 1 displayed the
colour change from yellow to colourless under the
5
−1
−
3
Figure 8. Fluorescence change of sensor 1 (5 × 10 M) in DMSO-d upon addition of 0.02 M of various anions on excitation at 365 nm
6
−
−
−
−
−
−
using UV lamp: blank (A), F (B), Cl (C), Br (D), H PO (E), CH COO (F) and C H COO (G).
2
4
3
6 5
−
Table 1. Comparison of selected molecular sensors with sensor 1 for F ion detection.
Detection limit
(µM)
No.
Name of sensors
Solvent medium
Ref.
[24]
[25]
[26]
This work
1
2
3
4
1-(4-fluorophenyl)-3-((1-(2-hydroxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)urea
N-(2-(benzothiazole-2-yl)phenyl)-4-nitrobenzamide
6,12-Diphenyl-5, 11-dihydroindolo[3,2-b]carbazole
sensor 1
DMSO
DMSO
65.8
58.0
23.3
18.0
3
CH CN
DMSO

8
S. MONGKHOLKAEW ET AL.
−4
Figure 9. Fluorescence image (under 365 nm UV light) of sensor 1 (5 × 10 M) adsorbed on a TLC plate (a) and filter paper (b) with
−
−3
−
−
a spot of F ion solution on sensor 1: sensor 1(A), sensor 1 with 2.50 × 10 M of F (B), sensor 1 with 0.005 M of F (C), sensor 1 with
−
−
−
−
0
.0075 M of F (D), sensor 1 with 0.01 M of F (E), sensor 1 with 0.025 M of F (F), sensor 1 with 0.05 M of F (G), sensor 1 with 0.10 M of
F (H), sensor 1 with 0.25 M of F (I) and sensor 1 with 0.50 M of F (J).
−
−
−
naked eye and from orange-yellow to blue under UV
light 365 nm upon addition of F ion. Moreover, the
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