Tris-triazole based chemosensors for selective sensing of Pb2+ ions

Article abstract of DOI:10.14233/ajchem.2019.22076

A series of novel tris-trizole based neutral chemosensors (4a-c) have been synthesized via click reaction and characterized by various spectral techniques. All the synthesized triazoles were evaluated for their ion binding properties towards various catio

Full text of DOI:10.14233/ajchem.2019.22076

Asian Journal of Chemistry; Vol. 31, No. 11 (2019), 2443-2447
A
SIAN
J
OURNAL OF HEMISTRY
C
https://doi.org/10.14233/ajchem.2019.22076
2+
Tris-Triazole Based Chemosensors for Selective Sensing of Pb Ions
1
1,*
2
POONAM RANI , KASHMIRI LAL and RAHUL SHRIVASTAVA
1
2
Department of Chemistry, Guru Jambheshwar University of Science & Technology, Hisar-125001, India
Department of Chemistry, Manipal University Jaipur, V.P.O. Dehmi Kalan, Jaipur-Ajmer Expressway, Jaipur-303007, India
*
Corresponding author: Fax: +91 1662 276240; Tel.: +91 1662 263152; E-mail address: klal_iitd@yahoo.com
Received: 14 March 2019; Accepted: 24 April 2019; Published online: 28 September 2019;
AJC-19566
A series of novel tris-trizole based neutral chemosensors (4a-c) have been synthesized via click reaction and characterized by various
2+
2+
2+
spectral techniques. All the synthesized triazoles were evaluated for their ion binding properties towards various cations (Cu , Zn , Ca ,
2
+
2+
2+
2+
2+
2+
Co , Cd , Hg , Pb and Ni ) by UV-visible titration experiments. It was observed that the addition of Pb ions to compound 4a led to
significant changes in UV-visible spectrum and a new UV band was observed at 262 nm. Further, the Job′s plot confirmed the formation
2+
2+
of 1:1 complex between compound 4a and Pb . The synthesized chemosensor selectively sense Pb ions in preference to other cations
like Cu , Zn , Ca , Co , Cd , Hg , Pb and Ni .
2
+
2+
2+
2+
2+
2+
2+
2+
Keywords: 1,2,3-Triazoles, Click reaction, Chemosensors, Lead ions.
techniques not easily accessible. In view of these, there is an
urgent need to develop a sensitive, economical and easy to
use monitoring technique for the detection of lead at low
concentration.
INTRODUCTION
Lead is known as the highly toxic metal ion present in
soil, water bodies and air due to its frequent uses in our daily
life in various forms like in storage batteries, cosmetics, paints,
insulation, ceramics, electronic devices, plastics, construction
materials and utilization in petroleum refining like sulfonation,
halogenation, extraction, condensation, metallurgy [1-4]. Due
to its non-biodegradable nature, trace of lead remains in soil,
water system and food items [5], which causes serious health
problems like infertility, increased blood pressure, nerve disorders,
muscle and joint pain, irritability, memory or concentration
loss, kidney disorders and mental retardation in humans [6-10].
Every year 143000 deaths and 0.6 % of the illnesses have been
estimated due to lead poisoning [11]. In view of these hazardous
health effects, monitoring and detection of lead ions is an area
of intense research activity. Although, various methods are
available for quantitative analysis of Pb(II) ions including atomic
absorption spectrometry [12], inductively coupled plasma mass
spectroscopy [13], inductively coupled plasma atomic emission
spectroscopy [14] and anodic stripping voltammetry [15]. Most
of these techniques involve difficult and long-lasting sample
preparation, large amount of expendable materials, high initial
cost, requirement of skilled operators which make these
In recent years, significant efforts have been made for the
development of highly selective and sensitive fluorescent/colori-
metric chemosensor molecules for the detection of Pb(II) ions
in chemical and biological systems with advantages of reusability,
high selectivity and sensitivity, real-time measurement and cost
effectiveness [16-20]. In this context, triazole moiety is an
attractive scaffold for designing and development of chemo-
sensor molecules due to its ability to participate in hydrogen
bonding and dipole-dipole interaction which can be used for
sensing of metal ions. 1,2,3-Trizole have been used for stabi-
lizing silver nanoparticles or used as capping agents for silver
nanoparticles. These stabilized or capped silver nanoparticles
are utilized for sensing and quantification of mercury ions either
through mercury induced aggregation of silver nanoparticles
or by the formation of Ag-Hg amalgam [21-23]. The litera-
ture survey revealed the use of 1,2,3-triazole derivatives for
designing of sensing materials for sensing of toxic metal ions
other than mercury are still rare despite their unique structural
features [24-28]. In continuation of our research efforts devoted
to ionic recognition [29-31], we are reporting herein, synthesis
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2
444 Rani et al.
Asian J. Chem.
1
3
of novel triazole derivatives (4a-c) via copper(I)-catalyzed
H). C NMR (CDCl
3
, 100 MHz): δ 58.80 (OCH ), 121.24 (C-
2
alkyne-azide cycloaddition reaction which exhibited high
5), 124.29, 125.98, 131.27, 134.44, 141.14, 143.71 (C-4),
147.26, 164.22 (C=O). HRMS: m/z (M+H) cacld. for
2+
+
selectivity and sensitivity towards Pb ions compared to other
metal ions.
C
36
H
24
N
12
O
12: 817.1715, found: 817.1651.
Tris((1-(p-tolyl)-1H-1,2,3-triazol-4-yl)methyl)benzene-
,3,5-tricarboxylate (4b): Off white solid, yield: 71 %, m.p.:
EXPERIMENTAL
1
2
(
-1
19-221 ºC. IR (KBr, νmax, cm ): 3136 (C-H str, triazole), 1730
C=O str., ester), 1614, 1559, 1520 (C-O str., ester), 1447, 1379,
319, 1234 (C-O str., ester), 1144, 1109, 1043, 984, 818, 741,
Propargyl alcohol, benzene-1,3,5-tricarbonyl trichloride,
benzyl halides, 4-dimethylaminopyridine, cuprous iodide,
microcrystalline cellulose were procured from Sigma Aldrich
and used as received. All the melting points were recorded in an
open capillary using LABCO melting point apparatus. IR
spectra were recorded on SHIMAZDU IR AFFINITY-I FT-IR
1
6
1
94, 662, 523. H NMR (CDCl
), 5.61 (s, 6H, OCH ), 7.33 (d, 6H, Ar-H, J = 8 Hz), 7.63
d, 6H, Ar-H, J = 8 Hz), 8.12 (s, 3H, triazolyl-H), 8.91 (s, 3H,
3
, 400 MHz): δ 2.44 (s, 9H,
CH
3
2
(
13
1
13
Ar-H). C NMR (CDCl , 100 MHz): δ 21.10 (CH ), 58.67
3
3
spectrophotometer. The H NMR (400 MHz) and C NMR
100 MHz) spectra were recorded using BrukerAvance-III 400
(
OCH
39.16, 142.84 (C-4), 164.76 (C=O). HRMS: m/z (M+H)
cacld. for C39 : 724.2632, found: 724.2502.
2
), 120.64 (C-5), 122.52, 130.28, 130.97, 134.54, 135.22,
(
+
1
nano bay spectrometer. The high-resolution mass spectra (HRMS)
were recorded using Micromass LC-MS/MS QTOF SCIEX-
QTOF spectrometer.
H
33
9
N O
6
Tris((1-phenyl-1H-1,2,3-triazol-4-yl)methyl)benzene-
,3,5-tricarboxylate (4c): Off white solid, yield: 71 %, m.p.:
88-190 ºC. IR (KBr, νmax, cm ): 3140 (C-H str., triazole), 1728
C=O str., ester), 1599 (C=N str.), 1562, 1504, 1445, 1383,
1
1
(
1
Procedure for the synthesis of tri(prop-2-yn-1-yl)benzene-
-1
1
,3,5-tricarboxylate (2): To a stirred solution of propargyl
alcohol (3.3 mmol) and 4-dimethylaminopyridine (3.3 mmol)
in 30 mL of dichloromethane, benzene-1,3,5-tricarbonyl
trichloride (1 mmol; dissolved in dichloromethane) was added
drop wise at 0 ºC. The stirring of reaction mixture was conti-
nued till the completion of reaction, as monitored by TLC.
After completion of the reaction, the reaction mixture was
diluted with dichloromethane and the organic layer was washed
with 2 N sulphuric acid (2 × 10 mL), water (2 × 10 mL) and
brine (10 mL) and dried over anhydrous sodium sulphate.
Dichloromethane was evaporated in vacuum to obtain the
product.
325, 1234 (C-O str., ester), 1148, 1107 (C-O str, ester), 1043,
1
9
72, 833, 760, 694, 525. H NMR (CDCl
), 7.47 (t, 3H, Ar-H, J = 8 Hz), 7.55 (t, 6H, Ar-H,
J = 7.7 Hz), 7.76 (d, 6H,Ar-H, J = 8 Hz), 8.17 (s, 3H, triazolyl-
3
, 400 MHz): δ 5.62
(
s, 6H, OCH
2
13
H), 8.91 (s, 3H, Ar-H). C NMR (CDCl
OCH
3
, 100 MHz): δ 58.67
(
2
), 120.82, 122.61 (C-5), 129.01, 129.79, 130.98, 135.20,
+
1
36.89, 142.95 (C-4), 164.69 (C=O). HRMS: m/z (M+H)
: 682.2163, found: 682.2026.
cacld. for C36
H
27
9
N O
6
RESULTS AND DISCUSSION
Tri(prop-2-yn-1-yl)benzene-1,3,5-tricarboxylate (2):
The synthesis of 1,2,3-tris-triazoles (4a-c) was achieved
by synthetic protocol as depicted in Scheme-I. In the first step,
tri(prop-2-yn-1-yl)benzene-1,3,5-tricarboxylate (2) was synthe-
sized from benzene-1,3,5-tricarbonyl trichloride (1) and propargyl
alcohol using N,N-dimethylaminopyridine in dichloromethane
[32]. The other precursor 4-substituted phenyl azides (3a-c)
were prepared by classical diazotization-azidation of unsubs-
tituted aniline. The synthesized 4-substituted phenyl azides
(3a-c) were subsequently reacted with tri(prop-2-yn-1-yl)benzene-
1,3,5-tricarboxylate (2) using cellulose supported cuprous iodide
nanoparticles [33] in water to furnish desired 1,2,3-tris-triazoles
(4a-c) in good yield at 80 ºC.
Off white solid, yield: 91 %, m.p.: 198-200 ºC. IR (KBr, νmax
,
-1
cm ): 3287, 3084 (str.), 2126 (C=C str), 1736 (C=O str., ester),
655, 1609 (C=O str., ester), 1441, 1371, 1325, 1271, 1233
C-O str., ester), 1152, 1107 (C-O str., ester), 999, 959, 932,
1
(
7
1
37, 689, 646). H NMR (CDCl
alkyne CH), 5.01 (d, 6H, OCH ), 8.98 (s, 3H,Ar-H). C NMR
, 100 MHz): δ 53.15 (OCH ), 75.64 (CH acetylene),
7.11 (C acetylene), 130.78 (Ar-C), 135.30, (Ar-C), 164.00
3
, 400 MHz): δ 2.58 (t, 3H,
13
2
(
7
(
CDCl
3
2
+
C=O). HRMS: m/z (M+H) cacld. for C18
H
12
6
O : 325.0712,
found: 325.0757.
General procedure for the synthesis of 1,2,3-tris-triazoles
(
4a-c): A mixture of alkyne 2 (1mmol), 4-substituted phenyl
The structures of synthesized tris-triazoles (4a-c) were
confirmed on the basis of their FTIR, H NMR, C NMR and
1
13
azides (3a-c) (3.6 mmol) and catalyst (100 mg) in 10 mL
of water was stirred at 80 ºC until TLC analysis shows that
the reaction is complete. The reaction mixture was cooled to
room temperature, filtered and residues thus obtained were
washed with ethyl acetate. Solvent was evaporated under high
vacuum to get corresponding 1,2,3-tris-triazoles (4a-c) in good
yield.
Tris((1-(4-nitrophenyl)-1H-1,2,3-triazol-4-yl)methyl)
benzene-1,3,5-tricarboxylate (4a): Off white solid, yield: 71
%
triazole), 1732 (C=O str., ester), 1601, 1524, 1443, 1412, 1342,
1
9
δ 5.61 (s, 6H, OCH
6
HRMS data. For example, FTIR spectrum of compound 4a,
-1
displayed bands at 1732 and 3125 cm assigned for carbonyl
stretching band and C-H stretching of triazole, respectively.
1
The H NMR spectrum of compound 4a exhibited two singlets
at δ 5.70 and δ 8.0 which were assigned to methylene group
13
and triazolyl protons, respectively. In C NMR spectrum of
compound 4a, appearance of peaks at δ 58.80, δ 143.71 and δ
121.24 due to methylene carbons, C-4 and C-5 carbon atoms
of the triazole ring further corroborated the assigned structure.
The mass spectrum of compound 4a showed a peak at 817.1651
-1
, m.p.: 138-140 ºC. IR (KBr, νmax, cm ): 3125 (C-H str.,
+
248 (C-O str., ester), 1179, 1152 (C-O str., ester) 1111, 1005,
(M+H) is in good agreement with the molecular formula of
1
62, 880, 820, 768, 741, 691, 629. H NMR (CDCl
), 8.23 (d, 6H, Ar-H, J = 12 Hz), 8.44 (d,
H, Ar-H, J = 8 Hz), 8.71 (s, 3H, triazolyl-H), 9.17 (s, 3H, Ar-
3
, 400 MHz):
the synthesized compound. Similarly, analytical and spectral
data of compounds (4b and 4c) was laid in agreement to the
assigned structure.
2

2+
Vol. 31, No. 11 (2019)
Tris-Triazole Based Chemosensors for Selective Sensing of Pb Ions 2445
R
R
Cl
O
O
O
R
N
N
O
O
(i)
N
(
ii)
Cl
Cl
O
O
N
N
3a-3c
N
N
O
O
O
O
O
O
2
N
N
1
O
O
4a; R = NO2
4b; R = CH3
4c; R = H
4a-c
Scheme-I: Synthesis of target compounds 4a-c: Reagents and conditions: (i) propargyl alcohol, N,N-dimethyl amino pyridine. (ii) Phenyl
azides (3a-3c), cuprous iodide nanoparticles catalyst and water (10 mL), 80 °C
2
+
The ion recognition properties of synthesized receptor (4a)
were investigated by UV-visible studies in DMSO/CH CN (1:9
v/v) solvent system. The binding interactions of receptor 4a
visible titration experiments show upon addition of Pb ions
to 12.0 µM solution of receptor 4a leads to step-wise decrease
of 310 nm peak with appearance of new peak at 262 nm which
3
2+
were investigated upon addition of perchlorates of different
reached its limiting value on addition of 1.0 equivalent of Pb
2+
2+
2+
2+
2+
2+
2+
2+
ions such as Cu , Zn , Ca , Co , Cd , Hg , Pb and Ni to
standard solution of receptor 4a. However, a marked shift in
absorption spectrum of receptor 4a was observed upon addition
of lead perchlorate as shown in Fig. 1. The absorption spectrum of
ions as shown in Fig. 2. In addition to this, appearance of a
well defined isosbestic point at 344 nm in UV-visible spectrum
attributed the formation of single reactive intermediate between
2+
the receptor 4a and Pb ion in equilibrium and thus formation
2+
2+
receptor 4a in the presence of Pb ions was almost unaffected
of 1:1 complex between receptor 4a and Pb ion.
by the presence of other competing metal ions. The addition
of Pb ions to a solution of receptor 4a led to gradually decrease
2+
262 nm
1.5
in the intensity at 310 nm and appearance of new absorption
2+
band at 262 nm. The observed blue shift indicated that Pb
ion interact with carbonyl oxygen atom and nitrogen atom of
trizole moiety of receptor 4a. These results were consistent with
the observation from the various triazole based chemosensors
reported in literature [34-36].
1.2
310 nm
0.9
1.5
4a + Pb(II)
0
.6
.3
0
1.2
0
4a + other metal ions
0.9
2
40
280
320
Wavelength (nm)
Fig. 2. Absorption titration spectra of 4a (12 µM) with gradual addition of
360
400
440
0.6
2
+
3
Pb ions in DMSO-CH CN(1.0:9.0 v/v) solution
0
.3
To find out stoichiometry of the complex between receptor
a and Pb ion, an isomolar concentration of receptor 4a and
2+
4
2+
Pb ion was made and the absorbance change at 262 nm was
monitored spectrophotometrically (Job′s continuous variation
plots) as shown in Fig. 3. Quantitative analysis through Job′s
0
2
40
280
320
Wavelength (nm)
Fig. 1. Absorption spectra of 4a (12 µM) upon addition of various ions as
360
400
440
2+
continuous variation plot exhibit a inflection point for Pb ion
at the mole fraction of 0.5, thereby suggesting the formation
2
+
2+
2+
2+
2+
2+
2+
2+
Cu , Zn , Ca , Co , Cd , Hg , Pb , Ni in DMSO/CH
1.0:9.0 v/v)
3
CN
2+
(
of 1:1 complex between receptor 4a and Pb ion.
As indicated from the Benesi-Hildebrand plot of measured
2
+
The UV-visible binding interaction of receptor 4a and Pb
2+
2
absorbance [1/(A-A
o
)] versus 1/[Pb ] a linear correlation (R
)]
ions were investigated by monitoring absorption changes upon
gradual addition of lead perchlorate to a solution of receptor
=
0.99457) exists between measured absorbance [1/(A-A
o
2+
versus 1/[Pb ]. These results are also consistent with a 1:1
4
a in DMSO-CH
3
CN (1.0:9.0 v/v) solvent system. The UV-
2+
association stoichiometry between host 4a and guest Pb ion

2
446 Rani et al.
Asian J. Chem.
0.10
0.08
0.06
0.04
0.02
0
O
O
O
N
O
O
O
N
N
N
N
N
N
N
N
R
R
= Pb2+ ion
R
2
+
Scheme-II: Possible binding model of 4a with Pb ion
Conclusion
0
0.2
0.4
0.6
0.8
1.0
In conclusion, we have synthesized some triazole based
chemosensor molecules (4a-c) via copper(I)-catalyzed alkyne-
azide cycloadditon reaction. The UV-visible titration studies
Mole fraction of 4a
2
+
Fig. 3. Job’s plot of 4a with Pb ion at 262 nm determined by UV-visible
experiments in DMSO-CH CN (1.0:9.0 v/v) solvent system
2+
3
revealed that compound 4a selectively sense Pb ions in pref-
2
+
2+
2+
2+
2+
2+
2+
2+
erence to Cu , Zn , Ca , Co , Cd , Hg , Pb and Ni ions.
The Job′s cotinuous variation plots and Benesi-Hildebrand plot
suggested 1:1 binding stoichiometry between compound 4a
2
+
(
Fig. 4). Moreover, the binding constant (K
determined from increasing intensity at 262 nm was found to
be 5.5 × 10 M using Benesi-Hildebrand plot. Furthermore,
detection limit of triazole 4a for the detection of Pb ions was
found to be 2.89 × 10 M. The detection limit was calculated
from the equation LOD = 3α/S. Here, α means the standard
deviation of blank measurements and S means the slope of
calibration curve of UV-visible titrations.
f
) of 4a-Pb ,
5
-1
2+
-6
and Pb ion with a detection limit of 2.89 × 10 M.
2+
-6
ACKNOWLEDGEMENTS
The authors are thankful to Central Instrumentation Labo-
ratory, Guru Jambheshwar University of Science & Technology,
Hisar and Manipal University Jaipur, Jaipur, India for NMR
and UV-visible analyses. One of the authors, Poonam Rani,
thanks University Grants Commission (UGC), New Delhi, India
for the award of Junior Research Fellowship, respectively. Other
author, Rahul Shrivastava, also acknowledges to Department
of Science & Technology, Government of Rajasthan, India
(P.7(3)S.T./R & D/2016/4871) for financial assistance.
4
3
CONFLICT OF INTEREST
The authors declare that there is no conflict of interests
regarding the publication of this article.
2
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Y = 0.00003x + 0.81932
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0
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methods.
9
.

2+
Vol. 31, No. 11 (2019)
Tris-Triazole Based Chemosensors for Selective Sensing of Pb Ions 2447
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