Synthesis and characterization of 1,2,3-triazoles-linked urea hybrid sensor for selective sensing of fluoride ion

Article abstract of DOI:10.1016/j.molstruc.2019.127437

Two urea-linked 1,2,3-triazole based sensors (5a and 5b) have been synthesized by 1,3-dipolar cycloaddition between 1-(4-fluorophenyl)-3-(prop-2-yn-1-yl)urea (2) and phenyl azides (4a-4b) via copper(I)-catalyzed click reaction. The synthesized sensors 5a

Full text of DOI:10.1016/j.molstruc.2019.127437

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Synthesis and characterization of 1,2,3-triazoles-linked urea hybrid sensor for
selective sensing of fluoride ion
Poonam Rani, Kashmiri Lal, Aruna, Rahul Shrivastava, Vikas D. Ghule
PII:
S0022-2860(19)31546-7
DOI:
https://doi.org/10.1016/j.molstruc.2019.127437
MOLSTR 127437
Reference:
To appear in: Journal of Molecular Structure
Received Date: 1 June 2019
Revised Date: 4 October 2019
Accepted Date: 16 November 2019
Please cite this article as: P. Rani, K. Lal, Aruna, R. Shrivastava, V.D. Ghule, Synthesis and
characterization of 1,2,3-triazoles-linked urea hybrid sensor for selective sensing of fluoride ion, Journal
of Molecular Structure (2019), doi: https://doi.org/10.1016/j.molstruc.2019.127437.
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Synthesis and characterization of 1,2,3-triazoles-linked urea hybrid sensor for selective
sensing of fluoride ion
Poonam Rania, Kashmiri Lal a*, Arunab, Rahul Shrivastavab, and Vikas D. Ghulec
aDepartment of Chemistry, Guru Jambheshwar University of Science and Technology, Hisar-
125001, India
bDepartment of Chemistry, Manipal University Jaipur, VPO-Dehmi Kalan, Of Jaipur-Ajmer
Expressway, Jaipur, Rajasthan, India
cDepartment of Chemistry, National Institute of Technology, Kurukshetra, 136119, India
* Corresponding author. Tel.: +91 1662 263152; fax: +91 1662 276240
E-mail address: klal_iitd@yahoo.com (Kashmiri Lal)
Abstract
Two urea-linked 1,2,3-triazole based sensors (5a and 5b) have been synthesized by 1,3-dipolar
cycloaddition between 1-(4-fluorophenyl)-3-(prop-2-yn-1-yl)urea (2) and phenyl azides (4a-4b)
via copper(I)-catalyzed click reaction. The synthesized sensors 5a and 5b have been evaluated
-
for their sensing ability towards anions (F-, Br-, Cl-, I-, H2PO4 and AcO-) and cations (Cu2+, Zn2+,
Ca2+, Co2+, Cd2+, Hg2+, Pb2+ and Ni2+) through UV-Visible, fluorescence and NMR spectral
techniques. It was observed that sensor 5a exhibited selective sensing for F- ion with a
bathochromic shift in absorption spectrum and showed fluorescence “turn-on” behavior in the
emission spectroscopy. The UV-Visible experiments exhibited that 5a interact with F- ion with a
stability constant (K) of 2.058×104 M-1 and detection limit of 5a for F- ions was found to be
65.76±0.45µM. Furthermore, these results were also supported by density functional theory
(DFT) calculations.
Keywords: Urea, triazoles, receptor, anion, fluoride ion.
1. Introduction
Selective sensing of anions by designed chemosensors has gained considerable interest because
of their important role in various chemical [1], biological and industrial processes [2]. The design
and development of efficient colorimetric sensors for biologically important anions is an
important area of research [3]. In particular, development of artificial chemosensors capable of

selective fluoride sensing are of high significance [4] because it is an essential element for the
human body and is used to treat dental caries osteoporosis and enamel demineralization [5,6].
The excess ingestion of the fluoride ions in our body lead to chronic and acute toxicity like
skeletal or dental fluorosis, urolithiasis, stomach ulcers, etc [7-10]. Due to the physiological,
pathological, and toxicological effects of fluoride ion, much attention has been devoted for the
development of fluorescent/colorimetric chemosensors for sensing of fluoride ion in chemical
and biological systems with high selectivity, sensitivity, real-time measurement and cost
effectiveness [11-13]. A number of cyclic and acyclic sensors [14-17] containing precise
alignment of amides, urea, thiourea, pyrazole, triazole, etc. have been synthesized for the
recognition of fluoride ions [18-19]. These artificial chemosensors sense anions by triggering
photophysical properties of chromophores while interacting with anions which result in
significant changes either in colour or in fluorescence [20-22]. It is well known that fluoride ion
forms strong hydrogen bond with hydrogen bond donors at low concentration while high
concentration of fluoride ion induces deprotonation. In this context, urea derivatives are excellent
hydrogen bond donors thereby reported to exhibit various biological activities [23-25].
Moreover, numerous urea based chemosensor molecules have been reported as naked-eye
fluoride ion sensors [26-29].
On the other hand, 1,4-disubstituted 1,2,3-triazole derivatives were studied extensively in
supramolecular [30] and coordination chemistry [31] due to their ease of synthesis via click
reaction and exceptional abilities to exhibit various noncovalent interactions including hydrogen
bonding, π-π stacking and C-H···π interactions with guest molecules [32]. 1,2,3-Triazoles exhibit
high dipole moment value which allow them to form hydrogen bonding with the guest entity.
The C5-H group of triazole ring also shows weak hydrogen bond donating ability with anions.
Additionally, 1,2,3-triazole derivatives were also reported as potential chelating ligands for
flouride ion. On the basis of aforementioned, herein, we report synthesis of urea-triazole hybrids
(5a-5b) from urea linked terminal alkyne and phenyl azides. The binding studies revealed that 5a
act as chromofluorogenic sensor for F- ions in preference to Cu2+, Zn2+, Ca2+, Co2+, Cd2+, Hg2+,
-
Pb2+, Br-, Cl-, I-, H2PO4 and AcO- ions.
2. Results and Discussion
2.1 Synthesis and Characterization of 1,2,3-Triazole-Linked Urea Hybrid Sensors

The urea-linked 1,2,3-triazoles 5a and 5b were synthesized in three steps (scheme 1). Firstly, 1-
(4-fluorophenyl)-3-(prop-2-yn-1-yl)urea (2) was synthesized from 4-flouro phenyl isocyanate (1)
and propargyl amine using triethylamine in dichloromethane. The other precursors, phenyl
azides (4a-4b) were prepared from classical diazotization-azidation of aniline derivatives [33]. In
the final step, 1-(4-fluorophenyl)-3-(prop-2-yn-1-yl)urea (2) and phenyl azides (4a-4b) were
subjected to azide-alkyne 1,3-dipolar cycloaddition reaction in presence of catalytic amount of
copper sulphate and sodium ascorbate in water:DMF to furnish urea-linked 1,2,3-triazoles (5a
and 5b) in high yield.
O
HN
N
N C O
H
(i)
R1
N
N
F
F
N
5a: R1 = 2-OH
5b: R1 = H
(iii)
2
1
HN
HN
O
N3
NH2
(ii)
F
R1
R1
5a-5b
4a-4b
3a-3b
Scheme 1. Synthesis of 5a-5b: (i) Propargyl amine, triethylamine, DCM. (ii) HCl, NaNO2,
DCM, NaN3, 0 °C. (iii) Phenyl azides (4a-4b), CuSO4.5H2O, sodium ascorbate, DMF:H2O, rt.
1
13
The synthesized triazole derivatives 5a and 5b were characterized using FTIR, H NMR, C
NMR and HRMS techniques. For example, FTIR spectrum of compound 5a, displayed two
bands at 1669 cm-1 and 3158 cm-1 due to carbonyl stretching and C-H stretching of triazole ring,
1
respectively. The H NMR spectrum of compound 5a exhibited two singlets at δ 10.54 and δ
8.33 due to OH and triazolyl protons, respectively. The NH protons of urea moiety of 5a
13
resonated at δ 8.63 ppm and δ 6.65 ppm, respectively. In C NMR spectrum of 5a, carbonyl
carbon exhibited a peak at δ 158.60 ppm, while, signal of methylene carbon was observed at δ
35.28 ppm. The C-5 and C-4 carbons atoms of the triazole moiety were observed at δ 120.02
ppm and δ 145.71 ppm respectively. The HRMS analysis of 5a exhibited molecular ion peak at

328.1423 (M+H)+ which is consistent with molecular formula. Similarly, analytical and spectral
data of compound 5b was laid in agreement to the assigned structure.
2.2 Sensing Behaviour of Synthesized Compounds Using UV-Visible Spectroscopic Method
The sensing abilities of 5a-5b were investigated by absorption, emission and NMR studies
towards different cations and anions. The UV-Visible spectroscopic experiments were performed
-
with 5a by adding tetrabutylammonium salts of F-, Br-, Cl-, I-, H2PO4 and AcO- ions and
perchlorate salts of Cu2+, Zn2+, Ca2+, Co2+, Cd2+, Hg2+, Pb2+ and Ni2+ ions in DMSO. The UV-
Visible spectrum of 5a showed a band at 305 nm which was shifted to a new absorption band at
343 nm on addition of fluoride ions as shown in Fig. 1 whereas other ions including Br-, Cl-, I-,
-
H2PO4 and AcO- anions and Cu2+, Zn2+, Ca2+, Co2+, Cd2+, Hg2+, Pb2+ and Ni2+ metal ions did not
produce any change in absorption spectrum. The observed sensing ability of 5a towards fluoride
ion was examined in the presence of other tested anions and cations and no interference of other
ions was obtained in absorption studies.
1.0
5a and 5a with other ions
0.5
5a with F
-
0.0
250
300
350
400
450
Wavelength (nm)
-
Fig. 1. UV-Visible spectra of 5a (1×10-4 M in DMSO) upon addition of F- , Br- , Cl-, I-, H2PO4 ,
AcO-, Cu2+, Zn2+, Ca2+, Co2+, Cd2+, Hg2+, Pb2+ and Ni2+ ions (25×10-4 M in DMSO)
As shown in UV-Visible titration spectra in Fig. 2, upon gradual addition of fluoride ions (0.0-
6.0 equiv.) in solution of 5a, the intensity of absorption maxima of 5a at 305 nm was decreased
and a new band at 343 nm was started to become visible. These results indicated the interaction
between receptor and fluoride ion which led to deprotonation of acidic amide NH group of urea
of 5a thereby causing a red shift of 38 nm mainly because of intramolecular charge transfer
(ICT) phenomenon between anion-urea [34].

1.0
0.8
0.6
0.4
0.2
0.0
-
0.0eq to 6 eq F ions
300
400
500
600
700
800
Wavelength(nm)
Fig. 2. The absorption titration spectra of 5a (0.1 mM) with 0.0 to 6.0 equiv. of F- (2.5 mM) ions
in DMSO solution
Stability constant (K) between triazole-linked urea sensor (5a) and F- ion was calculated from
UV-Visible titration data (y = 6E-05x+1.235 9, R² = 0.996) using Benesi–Hildebrand equation
and found to be 2.058×104 M-1 (Fig. 3). Furthermore, the detection limit of 5a was calculated
from the equation LOD = 3α/S for the fluoride anion and was found to be 65.76±0.45 µM. Here,
α is the standard deviation of blank measurements (0.002517) and S is the slope of calibration
curve (Fig. 4) of the UV-Visible titrations.
3.5
y = 6E-05x + 1.2356
3
R² = 0.9969
2.5
2
1.5
1
0.5
5000
10000
15000
20000
25000
30000
1/[F-] (M-1)
Fig. 3.The Benesi–Hildebrand plot of measured absorbance [1/(A-A0)] at 343 nm versus 1/[F-]
(M-1)

0.54
0.53
0.52
0.51
0.5
y = 114.82x + 0.4553
R² = 0.9886
0.49
0.48
0.47
0.46
0.45
0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007
[F-] (M)
Fig. 4. Determination of detection limit for F- anion; Absorbance vs. F- concentration (M) plot
for 5a receptor (65.8 µM)
2.3 Sensing Behaviour of 5a Using Fluorescence Spectroscopic Method
The sensitivity of 5a for fluoride ion was also examined by exploring its fluorescence spectra in
DMSO:CH3CN (1:9, v/v) solution. The fluorescence experiments were performed from 350 nm
to 600 nm using silt width of 10 nm. The sensor 5a showed emission peak at 425 nm when
excited at 325 nm. A distinct change in the emission spectrum was obtained in presence of
fluoride ions while other tested metal ions and anions (Br-, Cl-, I-, H2PO4 , AcO-, Cu2+, Zn2+,
-
Ca2+, Co2+, Cd2+, Hg2+, Pb2+ and Ni2+) did not exhibit any noticeable changes in emission
spectrum under similar experimental conditions. It was found that continue addition of F- ion to a
solution of 5a, a steady increase in emission intensity was observed at 425 nm as shown in fig. 5.
These observations are consistent with the previous report [35-37] which advised that
fluorescence “turn-on” behaviour may be the result of hydrogen bonding in between 5a and F-
ion at initial addition of F- ions whereas further addition of F-ions led to deprotonation of amide
(–NH) protons which facilitated the π to π* transitions responsible for enhancement behaviour of
5a.

Fig.5. Fluorescence titration spectra of 5a in DMSO:CH3CN 1:9 v/v (10 mM) with 0.0–6.0
equiv. of F- ions at 25°C
1
2.4 Sensing Behaviour of Synthesized Compounds Using H Nuclear Magnetic Resonance
Spectroscopic Method
To get more details about interaction mechanism of receptor 5a with F- ions, proton NMR
titration of 5a with fluoride ions in DMSO-d6 were performed. The OH, NH protons of urea and
CH proton of trizole ring of 5a were observed at δ 10.54, 8.68, 6.66 and δ 8.34 ppm, respectively
which shifted to downfield on addition of tetrabutyl ammonium fluoride. It was interesting to
observe that addition of more than 3.0 equivalent of TBAF, the signals of OH and NH protons of
urea were disappeared, whereas CH proton of triazolyl moiety was continuously shifted to
downfield. Along with this, it was also observed that aromatic proton at δ 7.58, 7.30, 7.06 and
6.69 were shifted to upfield as shown in Fig.6. These observations indicated that initially F- ion
interacted with OH, NH protons of urea and CH proton of trizole ring through hydrogen bonding
while further addition of F- ions resulted in deprotonation of OH and NH protons of urea. The
existence of CH proton of triazolyl moiety in presence of excess of F- ion showed the
involvement CH of proton only in hydrogen bond interactions. The deprotonation of OH and NH
protons induces an upfield shift of aromatic protons due to through-bond propagation of electron
density.

5a+5.0 eq. F-
5a+4.0 eq. F-
5a+3.0 eq. F-
5a+2.0 eq. F-
5a
Fig.6. Proton NMR titration spectra of 5a upon addition of various equiv. of TBAF in DMSO-d6
Similarly, the sensing behavior of 5b was also investigated for different ions such as F-, Br-, Cl-,
-
I-, H2PO4 , AcO-, Cu2+, Zn2+, Ca2+, Co2+, Cd2+, Hg2+, Pb2+ and Ni2+ under similar experimental
condition by comparing their UV-Visible and NMR studies before and after addition of these
ions. The result of UV-visible experiment clearly revealed that 5b does not exhibit any
significant changes in absorption spectrum in presence of these ions as shown in Figure S13 and
S14 (Supporting information). On the other hand, it was interesting to observe that NMR titration
experiment of 5b with fluoride ion shows that only N-H protons of 5b at δ 8.63 and 6.64 ppm
were disappeared in presence of F- ion. These experiments suggested that interactions between
5b and F- are weaker in comparison to sensor 5a, thereby no significant changes were recorded in
UV spectra. Also, the presence of phenolic proton (-OH) and C-H proton of trizole moiety of 5a
play significant role in strong binding of F- ion
Density Functional Theory (DFT) Study
The interaction between receptor 5a with fluoride anion was theoretically investigated exploiting
the DFT. The geometries of chemosensor and fluoride anion were optimized without symmetry
constraints using Gaussian 09 program [38-39] at B3LYP/6-311G(d,p) level of theory (Fig.7-8).
Absorption properties of these compounds were predicted at the same level. In general, the bond
lengths of N–H and H–F bonds were reported around 0.98 and 0.92 Å, respectively. In the
optimized structure of chemosensor (Fig. 7), the N4-H26 and N2-H25 bond distances are 1.00

and 1.01 Å, respectively and comparable with the reported data. The optimized structures of
chemosensor and fluoride anion show that the N–H bond lengths vary from 1.00 Å to 1.56 Å
(N14-H33) and 1.01 Å to 2.99 Å (N16-H34) (see Fig. 8). Therefore, it can be realized from these
data that deprotonation of the acidic N–H protons of urea based chemosensor and the formation
of HF. The DFT studies revealed that the interaction mechanism mediated through abstraction of
proton from the host. The frontier molecular orbitals (FMOs) of the chemosensor and fluoride
anion were examined to understand the modifications in the electronic structure of deprotonated
chemosensor, as depicted in Fig. 9. It is observed that the HOMO and LUMO are localized on
different parts. It can be seen in Fig. 9 that the HOMO of chemosensor is mostly restricted on the
fluoropheny l-1,2,3-triazole-urea part whereas the LUMO is present on the contradictory site.
After adding two fluoride ions to chemosensor, main part of HOMO and LUMO reposition on
urea linkage which reveals more reactivity in host molecule. For chemosensor, the energy gap
between these two MOs is 5.15 eV and after the deprotonation with fluoride ions, the energy gap
decreased to 1.74 eV.
Fig. 7. Optimized structure of chemosensor with some bond lengths (Å) calculated using the
B3LYP/6-311G(d,p)method. Yellow: C; Pink: N; Blue: H; red: O; Light orange: F.

Fig. 8. Optimized structure of chemosensor–F- with some bond lengths (Å) calculated using the
B3LYP/6-311G(d,p)method. Yellow: C; Pink: N; Blue: H; red: O; Light orange: F.
LUMO
∆E = 5.15 eV
∆E = 1.74 eV
HOMO
5a- F-
5a
Fig. 9. Frontier orbitals of chemosensor and chemosensor–F- calculated using the B3LYP/6-
311G(d,p) method
3. Experimental
3.1 Instrumentation, Analysis and Starting Material

The melting points (°C) of derivatives were recorded in open capillary. IR spectra of all
1
compounds were obtained on SHIMAZDU IR AFFINITY-I FT-IR spectrophotometer. The H
13
NMR (400 MHz) and C NMR (100 MHz) spectra were recorded using TMS as an internal
standard on Bruker Avance-III 400 nano bay spectrometer. HRMS spectra were acquired on LC-
MS/MS QTOF SCIEX-QTOF spectrometer. All the reactants, metal perchlorates and
tetrabutylammonium salt were procured from sigma Aldrich and used without further
purification.
3.2 Procedure for the Synthesis of urea-linked terminal alkyne (2)
To a stirred solution of propargylamine (1.1 mmol) and triethylamine (1.1 mmol) in 30 mL of
dichloromethane (DCM), 4-flouro phenyl isocyanate (1) (1 mmol; in dichloromethane) was
added drop wise at 0 ºC and the reaction mixture was allowed to stir at room temperature. After
completion of the reaction (confirmed by TLC), the reaction mixture was diluted with
dichloromethane and the DCM layer was washed with 2N sulphuric acid, water, brine solution
and dried over anhydrous sodium sulphate. Further, DCM layer was concentrated to dryness to
yield terminal alkyne (2) in good yield.
1-(4-fluorophenyl)-3-(prop-2-yn-1-yl)urea (2): off white solid, 81% yield, Mp: 168-170◦C. IR
(KBr, νmax/cm-1): 3325 (C-H alkyne), 3177 (NH str), 3113, 3073, 3017, 2914, 2120 (C≡C str),
1886 (C=O str), 1638 (C=O str, amide), 1609, 1533 (C=C str), 1506, 1456, 1414, 1354, 1304,
1
1242 , 1217, 1157, 1126, 1098, 1057. H NMR (CDCl3, 400 MHz): δ 3.09 (t, J = 2.4 Hz, 1H,
alkyne CH), 3.86-3.88 (dd, 2H, CH2), 6.45 (t, J = 4.0 Hz, 1H, NH), 7.05-7.09 (m, 2H,Ar-H),
7.38-7.41 (m, 2H, Ar-H) 8.61 (s, 1H, NH). 13C NMR (CDCl3, 100 MHz): δ 29.71 (NCH2), 75.14
(CH-acetylene), 77.77 (C-acetylene), 115.64, 115.87, 133.36, 158.00 (C=O), 160.42 (C-F).
HRMS: m/z (M+H)+ calculated for C10H10FN2O 193.0777, found: 193.0810.
3.3 General procedure for the synthesis of phenyl azides (4a-4b)
The organic azides 4a and 4b were synthesized from anilines by classical diazotization-azidation
reaction as reported [33].
3.4 General Procedure for the synthesis of urea-linked 1,4-disubstitutesd 1,2,3-triazoles (5a-5b)

A mixture of phenyl azide (1mmol), alkyne 2 (1mmol), and copper sulphate (0.1 mmol) and
sodium ascorbate (0.2 mmol) in DMF:water (8:2) was stirred at room temperature. After
completion of the reaction (monitored by TLC), an ice cold aqueous solution of ammonia:
ammonium chloride (9:1) was added to the reaction mixture. The precipitates thus obtained were
filtered and dried to yield the desired 1,4-disubstituted 1,2,3-triazoles (5a-5b) in good yield.
1-(4-fluorophenyl)-3-((1-(2-hydroxyphenyl)-1H-1,2,3-triazol-4-yl)methyl)urea (5a): Light
brown solid, 87% yield, Mp: 210-212◦C. IR (KBr, νmax/cm-1): 3361 (OH str), 3290 (NH str),
3158 (C-H str, triazole), 1669 (C=O str), 1579 (C=O str, amide), 1511 (C=C str), 1475, 1313,
1
1277, 1230, 1090. H NMR (DMSO, 400 MHz): δ 4.43 (d, J = 5.6 Hz, 2H, NCH2), 6.66 (t, J =
4.0 Hz, 1H, NH), 6.99 (t, J = 7.2 Hz, 1H, Ar-H), 7.04-7.12 (m, 3H, Ar-H), 7.31-7.36 (m, 1H, Ar-
H), 7.39-7.43 (dd, J = 4.0 Hz, 1H, 2H, Ar-H), 7.59-7.60 (m, 1H, Ar-H), 8.33 (s, 1H, triazolyl-H),
13
8.63 (s, 1H, NH), 10.54 (s, 1H, OH). C NMR (DMSO, 100 MHz): δ 35.28 (CH2), 115.46,
115.68, 117.53, 119.78, 119.85, 120.02 (C-5), 124.59, 125.06, 125.48, 130.47, 137.21, 145.71
(C-4), 149.95, 155.63, 156.28, 158.60 (C=O). HRMS: m/z (M+H)+ calculated for C16H14FN5O2
328.1210, found: 328.1423.
1-(4-fluorophenyl)-3-((1-phenyl-1H-1,2,3-triazol-4-yl)methyl)urea (5b): Light yellow solid,
89% yield, Mp: 198-200◦C. IR (KBr, νmax/cm-1): 3312 (NH str), 3134 (C-H str, triazole), 1636
1
(C=O str), 1612 (C=O str, amide), 1571 (C=C str), 1509, 1467, 1306, 1219 , 1052. H NMR
(CDCl3, 400 MHz): δ 4.32 (d, J = 5.6 Hz, 2H, NCH2), 6.56 (t, J = 5.6 Hz, 1H, NH), 7.06 (t, J =
8.8 Hz, 2H, Ar-H), 7.31-7.40 (m, 7H, Ar-H), 8.00(s, 1H, triazolyl-H), 8.58 (s, 1H, NH). 13C
NMR (CDCl3, 100 MHz): δ 39.99 (CH2), 119.79, 120.01 (C-5), 124.70, 124.77, 125.14, 133.42,
134.46, 140.81, 141.77 (C-4), 160.74 (C=O), 161.54. HRMS: m/z (M+H)+calculated for
C16H14FN5O 312.1261, found: 312.1460.
4 Conclusion
In conclusion, urea-linked 1,2,3-triazoles (5a and 5b) have been synthesized via 1,3-dipolar
cycloaddition between 1-(4-fluorophenyl)-3-(prop-2-yn-1-yl)urea (2) and phenyl azides (4a-4b).
The sensor 5a exhibited significant selectivity for F- ion in presence of other competing anions
and cations as revealed by UV-Visible, fluorescence and NMR titration experiments. The
Benesi–Hildebrand plot revealed that sensor 5a interacts with F- with stability constant K of

2.058×104 M-1 and detection limit of 65.8 µM ranges. Further, fluorescence, NMR experiments
and density function theory calculations rationalized the experimental results.
5 Acknowledgement
Authors are thankful to Central instrumentation laboratory, Guru Jambheshwar University of
Science & Technology, Hisar for running NMR, HRMS and UV-Visible spectrum. Poonam Rani
thanks University Grants Commission (UGC), New Delhi, India for the award of Junior
Research Fellowship and Kashmiri Lal thanks Guru Jambheshwar University of Science &
Technology, Hisar for financial assistance (DAA 17B (ii) Research Activities (R & D) for 2018-
19) , respectively.
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Highlights
•
•
•
Synthesis of 1,2,3-Triazole-linked urea hybrids using click reaction.
Compound 5a exhibited selective sensing for F- ion in preference to different ions.
Binding properties were studied by UV-Visible, Fluorescence and NMR titration
experiments.
•
DFT studies also supported the experimental results.

Declaration of Interest Statement
Authors declare no conflict of interest