Novel fluorescent sensor for silver (I) based on the 3,4-bis-triazole Bodipy via dual-click chemistry

Article abstract of DOI:10.1016/j.molstruc.2017.01.003

This investigation paper relates with a novel dual-Bodipy derivative obtained by using ‘click’ chemistry. The synthesized compounds were characterized by some techniques as ¹H NMR, ¹³C NMR, ¹¹B-NMR, ¹⁹F NMR, FT-

Full text of DOI:10.1016/j.molstruc.2017.01.003

Journal of Molecular Structure 1134 (2017) 345e349
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Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Novel fluorescent sensor for silver (I) based on the 3,4-bis-triazole
Bodipy via dual-click chemistry
Ahmed Nuri Kursunlu*, Ersin Güler
Department of Chemistry, University of Selcuk, Campus, 42075, Konya, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
This investigation paper relates with a novel dual-Bodipy derivative obtained by using ‘click’ chemistry.
The synthesized compounds were characterized by some techniques as 1H NMR, 13C NMR, 11B-NMR, 19
F
Received 11 November 2016
Received in revised form
30 December 2016
Accepted 1 January 2017
Available online 2 January 2017
NMR, FT-IR, Uvevis, spectrofluorimetry, mass, elemental analysis, melting point. The photophysical
measurements were conducted on 4,4-difluoro-8-(4-(3-{8-{3,4-Bis{1,2,3 triazolomethoxy}benzalde-
hyde)}propoxy))phenyl-4-bora-3a,4a, diaza-s-indacene (Bodipy-T) in presence of different metal ions.
General trends were performed for emission, absorption, excitation, complex stoichiometry, different
concentrations, competing ion, binding constants etc. in methanolic medium. Bodipy-T can be potentially
served as a sensitive and selective ratiometric sensor for Ag (I) ion, moreover, it includes a modifiable
group (aldehyde) for the preparing of its new derivatives.
Keywords:
Bodipy
Silver
Fluorescent sensor
Click
© 2017 Elsevier B.V. All rights reserved.
Emission
Excitation
1. Introduction
click-triazole rings had been rarely reported [9e18]. Click reaction
was also performed for Bodipy derivatives used as fluorescent
Silver compounds have been useful for the inhibiting of repro-
ductive or the killing of harmful cells while it have directly not
toxicity to metabolisms. However, the large doses of silver ions
cause to some negative results as argyria, a blue-grayish pigmen-
tation of the skin, eye [1e3] that they can coordinate with the
sulfhydryl terminals in food chains owing to soft-soft acid-base
interaction. Literatures emphasized on the detection difficulty of Ag
(I) ion depending on its low coordination ability. So, the sensor
researchers have to take into account a lot of parameters in the
design principles for the specific detection of Ag (I) [4,5]. Although
most sensors based on metal-ligand complexation for heavy metal
ions detection have been designed, there are only a few effective
reports on Ag (I) ion sensors owing to difficulty to be selected from
other metal ions [6e8]. To aim, ‘Click chemistry’ (cycloaddition
with copper(I)-catalyzed) is one of the most effective methods due
to high yield, synthetic simplicity and practice purification [9e13].
A lot of papers had been submitted on the complexation between
heavy metal ions and triazoles rings depending on sensitivity,
selectivity [14e17] while the fluorescent Ag (I) sensor based on
sensors. Because, the analyte causes in either enhancement or
quenching effects in the emission of Bodipy dyes that can easily be
observed on spectrometers, in so much as, with naked eyes. In
there, Bodipy unit behaves as an antenna capable of light harvest-
ing while other organic groups are serving as a ligand-terminal. The
Bodipy dyes are preferred in sensors and biological imaging ap-
plications owing to their sharp absorption and high emission
combined with a perfect photostability [19e24].
In this study, we designed a new fluorescent sensor (Bodipy-T)
for Ag (I) ions via click reaction. The emission intensity of Bodipy-T
only changed in presence Ag (I) ion by a quenching mechanism that
silver ion encapsulated among two triazole moieties.
2. Experimental section
2.1. Instruments and materials
The dichloromethane was dried by calcium hydride depending
on a knowing procedure. The Bodipy with azido terminals was
prepared by the azide-processing of an alkyl bromide [25] and
purify by column chromatography. 3,4-dihydroxybenzaldhyde,
propargyl bromide, 1,3-dibromopropane, sodium azide, 4-
* Corresponding author.
E-mail address: ankursunlu@gmail.com (A.N. Kursunlu).
hydroxybenzaldeyde,
pyrrole,
borontrifluorideetherate,
http://dx.doi.org/10.1016/j.molstruc.2017.01.003
0022-2860/© 2017 Elsevier B.V. All rights reserved.

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A.N. Kursunlu, E. Güler / Journal of Molecular Structure 1134 (2017) 345e349
Scheme 1. The synthesis route of Bodipy-T.
trifluoroaceticacid (TFA), triethylamine, silica gel (32e70), 2,3-
Dichloro-5,6-dicyano-p-benzoquinone (DDQ), sodium sulfate, so-
dium ascorbate, copper sulfate, potassium carbonate were supplied
from different companies as Merck, Sigma-Aldrich, Acros, Fisher.
The solvents were used for column or synthesis. The UVevis
measurements were carried out by a Perkin Elmer Lambda 25
spectrophotometer and the emission recordings were taken from a
Perkin Elmer LS 55 fluorescence spectrometer. The synthesized
compounds were conditionally characterized by a combination of
1H NMR, 13C NMR, 11B-NMR, 19F NMR and elemental analysis etc.
2.3. Preparation of Bodipy-T
3,4-bis(prop-2-ynyloxy)benzaldehyde (0.107 g, 0.5 mmol) and
4,4-Difluoro-8-[4-(3-azidopropyloxy)phenyl)]-4-bora-3a,4a-dia-
zaindacene (0.367 g, 1 mmol) were stirred in 100 mL of ethanol at
room temperature. Then, 1.5 equiv. of sodium ascorbate and 0.2
equiv. of CuSO4 were poured to this mixture and stirred vigorously
for 96 h (TLC analysis monitored until the consumption of the re-
actants). After the reaction completed, the ethanol was evaporated
and the residue was extracted with CH2Cl2-water for three times.
The target material was taken form column (Ethylacetate, as an
eluent). Yield 15%. 1H NMR (CDCl3):
d (ppm) 9.85 (s, 1 H, HC]O),
7.96 (bs, 4H, pyrrole-H), 7.75 (d, 1H, ArH), 7.55 (m, 7.14, 7H), 7.22
(d,1H, ArH), 7. 02 (d, 4H, ArH), 6.96 (d, 4H, pyrrole-H), 6.55 (d, 4H,
pyrrole-H), 5.37 ve 5.30 (s, 4H, CH2), 4.80e4.65 (t, 4H, CH2), 4.05
(m-t, 4H, CH2), 2.51 (m, 4H, CH2). 13C NMR [100 MHz, CDCl3]:
2.2. Preparation of starting materials
All synthetic details and the spectral data for the starting com-
pounds used in the preparing of the target sensor were given in the
supplementary data.
d
(ppm); 191.15, 162.21, 161.23, 157.21, 153.23, 146.12, 143.12, 142.70,
139.34, 133.37, 132.93, 131.32, 126.87, 126.11, 118.37, 117.53, 115.49,

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347
Fig. 3. The excitation spectra of Bodipy-T (1.10ꢀ6 M) in the presence of different metal
ions (Zn (II), Cu (II), Ga (III), Cr (III), Ag (I), Hg (II), Co (II), Ni (II), Mn (II), Cd (II) (20
equiv.)) in methanol, lem ¼ 520 nm, slit:5.
Fig. 1. The fluorescence intensities of Bodipy-T (1.10ꢀ6 M) in the presence of different
metal ions (Zn (II), Cu (II), Ga (III), Cr (III), Ag (I), Hg (II), Co (II), Ni (II), Mn (II), Cd (II) (20
equiv.)) in methanol, lex ¼ 470 nm, slit:5.
Fig. 4. The complex stoichiometry by Job's plot for the complexation between Bodipy-T
(1.10ꢀ6 M) and Ag (I) in methanol (494 nm).
Fig. 2. The absorption spectra of Bodipy-T (1.10ꢀ6 M) in the presence of different metal
ions (Zn (II), Cu (II), Ga (III), Cr (III), Ag (I), Hg (II), Co (II), Ni (II), Mn (II), Cd (II) (20
equiv.)) in methanol.
113.31, 111.87, 110.13, 73.88, 65.43, 48.32, 28.32. Anal. Cald. (%)
C
49H42N10O5B2F4: C, 62.05; H, 4.46; N, 14.77; Found: C, 61.74; H,
4.91; N, 14.35. ESI-TOF-MS [þHþ]; m/z: 948.3.
3. Result and discussions
The synthesis route of Bodipy-T was displayed on Scheme 1. The
compound with di-alkyne was obtained from the propargylation of
the phenolic OH's in presence of potassium carbonate. Azido-
Bodipy was synthesized with a classical method of the boron-
dipyrrins. The target compound, Bodipy-T, was prepared by the
click reaction between di-alkyne terminals and azido terminal.
To spectroscopic properties, the selective fluoroionophoric
properties of Bodipy-T were initially investigated toward some
transition metal ions as Zn (II), Cu (II), Ga (III), Cr (III), Ag (I), Hg (II),
Co (II), Ni (II), Mn (II), Cd (II). All emission spectra were performed at
470 nm excitation in MeOH:H2O (9:1,v/v) and metal-ligand ratio
was determinate as 1/20 in the mixtures (Fig. 1). Except of Ag (I),
Fig. 5. The fluorescence spectra of Bodipy-T (1.10ꢀ6 M) upon addition of Ag (I), Inset the
titration curve of silver sensor as increasing concentration of Ag (I), ʎex ¼ 470 nm.

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A.N. Kursunlu, E. Güler / Journal of Molecular Structure 1134 (2017) 345e349
Fig. 6. The fluorescence changes of Bodipy-T (1.10ꢀ6 M) in the presence of both Ag (I) and the competing metal ion (20.0 equiv) (lem:510 nm).
free Bodipy-T and Bodipy-T/metal ion solutions gave to a rather
sharp band around 510 nm. The fluorescence peak of Bodipy-T
bathochromically shifted to red after the addition of Ag (I) ions. The
remarkable changes of the emission wavelength and intensity can
be attributed to the reverse ICT (internal charge transfer) [9] from
the Bodipy units to the nitrogen atoms of triazole rings and Ag (I)
ion [18].
Although the quenching or increasing effect of Ag(I) ion re-
ported for the change in the fluorescence intensity, the perfor-
mance of Bodipy-T as a Ag (I) sensor can compete with the most
effective sensors. While the I0/I ratio, namely, the quenching effect
in presence of Ag (I) is almost two-fold, the ratio of the fluorescence
intensities in presence-absence of silver ion increased toward
three-fold [18,26]. So, a effective fluorescent sensor for Ag (I) with a
high sensitivity and a Stokes shift has been improved by taking
advantage of the high fluorescent character of Bodipy derivatives.
The changes of the absorption curves parallel with the emission
curves. The Uvevis studies of Bodipy-T exhibited to three different
absorption transitions at 270, 400 and 495 nm (Fig. 2). The band at
495 nm assigned to an absorption characteristic of Bodipy unit and
Furthermore, the complex stoichiometry was studied by Job plot
method in the various concentrations of Bodipy-T and Ag (I) ion
(Fig. 4). The maximum point appeared around 0.5 in the mole
fraction of Ag (I) that the stoichiometric ratio between Bodipy-T and
Ag (I) was 1:1. This result approved that Ag (I) ion encapsulated
among two triazole rings [27]. This complexation mechanism can
be explained to soft-acid-soft base pairs, the chelating effect and
the ring diameter of Bodipy-T depending on donor atoms.
Moreover, we studied a sensing response of the sensor toward
various concentrations of Ag (I) (0e50 equiv.). In Fig. 5, two bands
appeared which are shifted towards different wavelengths just as
the absorption and emission spectra. The fluorescence intensity
was quenched following the addition of the silver ions, and the
emission peak was slightly shifted from 510 nm to 525 nm (Fig. 5).
Both the fluorescence intensities of Bodipy-T band at 510 nm and
the new band shifted to red were linearly quenched depending on
the increasing concentration of Ag (I). When 0e50 equivalents of
Ag (I) were added into the solution of Bodipy-T, the emission spectra
gradually gave a clear fluorescence change with three-fold, which
quenched the fluorescence owing to the metal-to-ligand charge
transfer (MLCT) or the effective affinity for silver ion between tri-
azole units. The observed bathochromic shift and change approved
to the using of Bodipy-T as a potential ratiometric sensor for Ag (I).
The binding constants was calculated by Stern-Volmer equation.
I0/I and the different concentrations of Bodipy-T displayed to a
linear relation and KSV was calculated as 8.3 ꢁ 106 Mꢀ1 (510 nm
emission). The detection limit (LOD) for Ag (I) ions was found from
the standard deviation of the blank and some parameters and the
LOD was performed from the emission data. To aim, the solutions of
Ag (I) were prepared in different concentrations. The LOD of Bod-
the other two band can be depended on n /p and p/p* transi-
tions of aromatic fragments of Bodipy-T. By the addition of metal
ions, the absorption spectrum of Bodipy-T given only the pro-
nounced band shifting and changes in presence of Ag (I) ion. So, the
characteristic band of Bodipy at 495 nm shifted and decreased.
Moreover, the broad transition around 400 nm disappeared. Simi-
larly, all changes assigned to the complexing effect between Bodipy-
T eAg(I). Although the imidazole and azide groups are considered a
borderline base, the triazole ring is a softer base than these nitrogen
clusters due to their circulated
p-electrons on more atoms with
electropositivity. As known, the interaction between hard bases
and hard acids are considered as ionic bonding, while soft bases
prefer a covalent interaction towards soft acids [27e31].
ipy-T towards Ag(I) was defined as 1.5 mM.
To the practical applicability of Bodipy-T as a selective fluores-
cent sensor toward Ag (I) ion, the competing ion studies were
To the better illumination of the bing properties, the excitaition
studies were carried out (the fixed emission at 520 nm). Fig. 3
displayed that the solutions of Bodipy-T and Bodipy-T/metal
mixture gave to three bands just as the absorption curves. The
important change of the excitation bands was not recorded except
of Ag (I). Some shifts was detected in the excitaition curve in
presence of Ag (I) ion that this shifts was attributed to a classical ICT
on-off type ratiometric chemosensors occurred upon the interac-
tion of Bodipy-T and Ag (I).
carried out in the presence of Ag (I) ion (20
Cu (II), Ga (III), Cr (III), Ag (I), Hg (II), Co (II), Ni (II), Mn (II), Cd (II) at
20 M concentration (Fig. 6).
The competing ions have not a significant effect on the fluo-
rescence property of Bodipy-T coordinated with Ag (I) ions.
Accordingly, these results approved that Bodipy-T can behave as a
selective fluorescent sensors towards Ag (I) ion in the presence of
most competing metal ions, too.
mM) mixed with Zn (II),
m

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349
[12] M.A. Tasdelen, Y. Yagci, Light-induced copper(I)-catalyzed click chemistry,
Tetrahedron Let. 51 (2010) 6945e6947.
4. Conclusion
[13] F. Giuntini, F. Bryden, R.W. Boyle, R. Daly, E.M. Scanlan, Huisgen-based
conjugation of water-soluble porphyrins to deprotected sugars: towards mild
strategies for the labelling of glycans, Org. Biomol. Chem. 12 (2014)
1203e1206.
[14] S. Erdemir, S. Malkondu, A simple triazole-based “turn on” fluorescent sensor
for Al3þ ion in MeCN-H2O and Fꢀ ion in MeCN, J. Lumin. 158 (2015) 401e406.
[15] S. Erdemir, O. Kocyigit, S. Malkondu, Detection of Hg2þ ion in aqueous media
by new fluorometric and colorimetric sensor based on triazole-rhodamine,
J. Photochem. Photobio. A Chem. 309 (2015) 15e21.
[16] J. Liu, X. Meng, H. Duan, T. Xu, Z. Ding, Y. Liu, L. Lucia, Two Schiff-base fluo-
rescence probes based on triazole and benzotriazole for selective detection of
Zn2þ, Sensors Actuat. B Chem. 227 (2016) 296e303.
[17] Y.-B. Ruan, S. Maisonneuve, J. Xie, Highly selective fluorescent and colori-
metric sensor for Hg2þ based on triazole-linked NBD, Dyes Pigments 90
(2011) 239e244.
In conclusion, a novel Ag (I) sensor incorporating Bodipy and
triazole units was effectively reported via click reaction. Bodipy-T
demonstrates to a specific ratiometric behavior towards Ag (I) ions
that it have a good LOD (1.5
m
M) and a valuable binding constant
(8.3 ꢁ 106
M
ꢀ1). By all data in the spectroscopic measurements,
Bodipy-T can be used as a fluorescent sensor for Ag(I) ion and this
will be guide to the forthcoming investigations.
Acknowledgements
We grateful to Selçuk University (SUBAP-Grant Number
[18] X. Liu, X. Yang, Y. Fu, C. Zhu, Y. Cheng, Novel fluorescent sensor for Agþ and
Hg2þ based on the BINOL-pyrene derivative via click reaction, Tetrahedron 67
(2011) 3181e3186.
[19] S. Çetindere, B. Cosut, S. Yes¸ ilot, M. Durmus¸ , A. Kılıç, Synthesis and properties
of axially-BODIPY conjugated subphthalocyanine dyads, Dyes Pigments 101
(2014) 234e239.
[20] M. Bayrakcı, A.N. Kursunlu, E. Güler, S¸ . Ertul, A new calix[4]azacrown ether
based boradiazaindacene (Bodipy): selective fluorescence changes towards
trivalent lanthanide ions, Dyes Pigments. 99 (2013) 268e274.
[21] A.N. Kursunlu, E. Guler, H.I. Ucan, R.W. Boyle, A novel Bodipy-Dipyrrin fluo-
rescent probe: synthesis and recognition behaviour towards Fe (II) and Zn (II),
Dyes Pigments 94 (2012) 496e502.
11101003) for the financial support of this paper.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2017.01.003.
References
[1] M. Yamanaka, K. Hara, J. Kudo, Bactericidal actions of a silver ion solution on
Escherichia coli, studied by energy-filtering transmission electron microscopy
and proteomic analysis, Appl. Environmen. Microbiol. 71 (2005) 7589e7593.
[2] C.R. Hammond, The Elements, in Handbook of Chemistry and Physics, 81st ed.,
CRC press, 2004. ISBN 0-8493-0485-7.
[3] C.M. Litwin, S.A. Boyko, S.B. Calderwood, Cloning, sequencing, and transcrip-
tional regulation of the Vibrio cholerae for gene, J. Bacteriol. 174 (1992)
1897e1903.
[22] A.N.
Kursunlu,
P.
Deveci,
E.
Guler,
Synthesis
and
spec-
troscopiceelectrochemical properties of novel ratiometric Hg (II) chemo-
sensor containing Bodipy and the N-phenylaza-15-crown-5 moiety, J. Lumin.
136 (2013) 430e436.
[23] A.N. Kursunlu, Z.E. Koc, A.Y. Obalı, E. Güler, A symmetric and selective fluo-
rescent Cu (II) sensor based on bodipy and s-triazine, J. Lumin. 149 (2014)
215e220.
[24] A.N. Kursunlu, Synthesis and photophysical properties of modifiable sin-
gle,dual, and triple-boron dipyrromethene (Bodipy) complexes, Tetrahedron
Lett. 56 (2015) 1873e1877.
[4] N.-J. Wang, C.-M. Sun, W.-S. Chung, A highly selective fluorescent chemo-
sensor for Ag
þ
based on calix[4]arene with, lower-rim proximal tri-
azolylpyrenes, Sensors Actuators B 171e172 (2012) 984e993.
[5] J.F. Zhang, Y. Zhou, J. Yoon, J.S. Kim, Recent progress in fluorescent and
colorimetric chemosensors for detection of precious metal ions (silver, gold
and platinum ions), Chem. Soc. Rev. 40 (2011) 3416e3429.
[25] A.N. Kursunlu, E. Guler, The sensitivity and selectivity properties of a fluo-
rescence sensor based on quinoline-Bodipy, J. Lumin. 145 (2014) 608e614.
[26] X.-P. He, Z. Song, Z.-Z. Wang, X.-X. Shi, K. Chen, G.-R. Chen, Creation of 3,4-bis-
triazolocoumarinesugar conjugates via flourogenic dual click, chemistry and
their quenching specificity with silver(I) in aqueous media, Tetrahedron 67
(2011) 3343e3347.
[6] L.-Q. Li, L.-J. Gao, A novel rosamine based fluorescent sensor for Ag þ recog-
nition, spectrochim, Acta Part A 152 (2016) 426e430.
[7] N.-J. Wang, C.-M. Sun, W.-S. Chung, A highly selective fluorescent chemo-
sensor for Agþ based on calix[4]arene with lower-rim proximal tri-
azolylpyrenes, Sensors Actuat. B 171e172 (2012) 984e993.
[8] A.D. Arulraj, R. Devasenathipathy, S.-M. Chen, V.S. Vasantha, S.-F. Wang,
Highly selective and sensitivefluorescent chemosensor for femtomolar
detection of silver ion in aqueous medium, Sens. Bio Sens. Res. 6 (2015)
19e24.
[9] X. Liu, X. Yang, H. Peng, C. Zhu, Y. Cheng, A fluorescent sensor for Hg2þ and
Agþ functions as a molecular switch based on click-generated triazole moiety,
Tetrahedron Let. 52 (2011) 2295e2298.
[10] O. Karagollu, M. Gorur, F. Gode, B. Sennik, F. Yilmaz, Phosphate ion sensors
based on triazole connected ferrocene moieties, Sensors Actuat. B 193 (2014)
788e798.
ꢀ
[27] M.A. Trojer, A. Movahedi, H. Blanck, M. Nyden, Imidazole and triazole coor-
dination chemistry for antifouling coatings, Hindawi Pub. Cor. J. Chem. (2013)
23, http://dx.doi.org/10.1155/2013/946739. Article ID 946739.
ꢁ
[28] F. Güllü, M. Bayrakcı, A.N. Kursunlu, S¸ . Yigiter, S¸ . Ertul, Synthesis and trivalent
lanthanide ion complexation studies of new macrocyclic receptors based
lactam ionophores, J. Incl. Phen. Mac. Chem. 80 (2014) 303e312.
[29] A. Ceylan, S.Z. Bas, M. Bayrakci, S. Ertul, A. Uysal, Synthesis and spectroscopic
studies of novel rhodanine azo dyes: an excellent selective chemosensor for
naked-eye detecting of Cu2þ ion, Acta Chim. Slov. 59 (3) (2012) 656e663.
[30] A.Y. Obali, H.I. Ucan, Novel dipodal Schiff base compounds: synthesis, char-
acterization and spectroscopic studies, J. Mol. Struct. 1081 (2015) 74e78.
[31] S. Malkondu, S. Erdemir, A novel perylene-bisimide dye as “turn on” fluo-
rescent sensor for Hg2þ ion found in DMF/H2O, Dyes Pigments 113 (2015)
763e769.
[11] P. Yazgan-Birgi, N. Alemdar, A.T. Erciyes, Styrenated urethane oil synthesis via
CuAAC click” chemistry approach, Prog. Org. Coat. 84 (2015) 107e114.