Development of a sensitive and selective fluorescent probe for Zn2+ based on naphthyridine Schiff base

Article abstract of DOI:10.1016/j.jphotochem.2019.02.024

In this study, bearing 4-methyl-7-acetamide-1,8-naphthyridyl group as the fluorophore and the receptor, we designed and synthesized a new-type Schiff-base ligand 1 which was identified as a Zn²⁺ fluorescent probe. The excellent selectivity and high sensitivity of this as-synthesized fluorescent probe 1 towards Zn²⁺ over other various biogenic metal ions were observed, for that only Zn²⁺ induced a drastic enhancement by about 63-fold in intensity of fluorescence emission at 504 nm, and the limit of detection (LOD) could reach 7.52 nM. Moreover, the formation of a 2:1 complex between this probe 1 and Zn²⁺ was determined, and the perfect invertibility and renewability of this probe 1 for sensing Zn²⁺ were also demonstrated. As a result, the practical applications of 1 were broadened for sensing and monitoring Zn²⁺ environmentally and biologically.

Full text of DOI:10.1016/j.jphotochem.2019.02.024

JournalofPhotochemistry&PhotobiologyA:Chemistry375(2019)231–236
Contents lists available at ScienceDirect
Journal of Photochemistry & Photobiology A: Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Development of a sensitive and selective fluorescent probe for Zn2+ based
on naphthyridine Schiff base
Chao-rui Lia, Guan-qun Wanga, Long Fana,b, Si-liang Lic, Jing-can Qina, Zheng-yin Yanga,⁎
a State Key Laboratory of Applied Organic Chemistry and Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province and College of
Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR China
b Quality and Technical Supervision and Inspection of Jin Chang, Jin Chang, 737100, PR China
c School of Petrochemical Engineering, Lanzhou University of Technology, Lanzhou 730050, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
In this study, bearing 4-methyl-7-acetamide-1,8-naphthyridyl group as the fluorophore and the receptor, we
designed and synthesized a new-type Schiff-base ligand 1 which was identified as a Zn2+ fluorescent probe. The
excellent selectivity and high sensitivity of this as-synthesized fluorescent probe 1 towards Zn2+ over other
various biogenic metal ions were observed, for that only Zn2+ induced a drastic enhancement by about 63-fold
in intensity of fluorescence emission at 504 nm, and the limit of detection (LOD) could reach 7.52 nM. Moreover,
the formation of a 2:1 complex between this probe 1 and Zn2+ was determined, and the perfect invertibility and
renewability of this probe 1 for sensing Zn2+ were also demonstrated. As a result, the practical applications of 1
were broadened for sensing and monitoring Zn2+ environmentally and biologically.
Fluorescent probe
Schiff-base
Zinc ion
Synthesis
Selectivity
1. Introduction
inspection with rapid responses [18–20], which makes the applications
of these fluorescent probes broad in various fields of ecology, biology
More and more attention has been attracted for tracking the con-
centration levels of transition metals by utilizing fluorescent probes to
date because of their crucial roles in various biological processes [1,2].
Among those transition metals, zinc is an element of the secondary
content in the human body. Owing to its rich coordination chemistry
[3–5], the structure and functionality of diverse proteins were ex-
pressed in the gene by utilizing required zinc ion as a cofactor, and zinc
ion also exists in many organelles like cytoblast, plastosome and cyto-
lysosome, etc [6–8]. However, when the amount of zinc ion in the
human body exceeds the limitation of its maximum level, many severe
diseases including Alzheimer’s disease, Friedreich’s dystaxia and Par-
kinson’s disease can be caused [9–11]. On the other side, impaired
cognitive disorders, immune dysfunction, durchfall and death can be
induced by the lack of micronutrient zinc ion particularly in under 5-
year-old children [12,13]. Thus, Zn2+-based compounds have found
wide repertoire in the fields of radiation protection, tumor sensitizing,
antidiabetic activity, and anti-microbial or anti-tumor agents [14–17].
Therefore, the detection of Zn2+ is a significant research topic for ex-
ploring its roles in various biological processes.
and clinical medicine [21–23]. The design and synthesis of highly se-
lective and sensitive fluorescent probes have been a promising research
field in chemistry due to their practicability and utility [24]. To date, a
series of Zn2+ fluorescent probes with excellent selectivity and high
sensitivity have been designed and synthesized on a basis of various
fluorophores, including macrocycle, heterocyclic ring, rhodamine,
coumarin and quinoline [25–31], but the reports about naphthyridine
derived fluorescent probes are extremely few [32]. Moreover, the ma-
jority of reported Zn2+ fluorescent probes encounter hardness in dif-
ferentiating Zn2+ from Cd2+ due to their similar chemical properties
and comparable fluorescence responses [33–35]. Therefore, it is still a
tremendous challenge for designing highly selective (differentiated
from Cd2+), temperate and efficient Zn2+ fluorescent probes based on
naphthyridine derivatives among scientists in the prospects of analy-
tical chemistry, biological chemistry and pharmaceutical science.
In our previous works, we reported the design and synthesis of novel
Schiff-base compounds with different fluorophore units and explored
their effects on the sensing of metal ions. Generally, the parts of re-
cognition moiety and fluorophore are two units of a fluorescent probe.
The building blocks of 8-naphthyridine and its derivatives always form
short distances of metallic bonds, thereby applying them widely as bi-
dentate ligands [36,37]. Additionally, an organic structure which
The development of fluorescent probes have drawn more concerns
than other optical probes among scientists due to their intrinsic ad-
vantages of high sensitivity, simplicity of operation, and real-time
⁎ Corresponding author.
E-mail address: yangzy@lzu.edu.cn (Z.-y. Yang).
https://doi.org/10.1016/j.jphotochem.2019.02.024
Received 6 December 2018; Received in revised form 19 February 2019; Accepted 20 February 2019
Availableonline20February2019
1010-6030/©2019PublishedbyElsevierB.V.

C.-r. Li, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry375(2019)231–236
Scheme 1. Synthetic route of compound 1.
contains a rigid and conjugate moiety is an ideal choice for the unit of
fluorophore. Based on this mechanism, compound 1 called 7-acet-
amidyl-4-methyl-2-formyl-1,8-naphthyridine trihydroxybenzoyl hy-
drazone was designed and synthesized, bearing 4-methyl-7-acetamide-
1,8-naphthyridyl group as the fluorophore and the receptor for sensing
Zn2+ (Scheme 1). A C]N bond was linked between 4-methyl-7-acet-
amide-1,8-naphthyridyl moiety and trihydroxybenzoyl hydrazine unit,
leading to the formation of a fluorescent-sensing molecule for sensing
metal cations potentially. From the experimental processes, we could
observe that this compound 1 showed significant fluorescence emission
enhancement with addition of Zn2+, and could be recognized as an
efficient probe for zinc ion detection. In addition, excellent selectivity
of 1 towards Zn2+ over other metal cations, especially Cd2+, was
confirmed.
another 30 mL of ethanolic solution containing 7-acetamidyl-4-methyl-
1,8-naphthyridine-2-aldehyde (4) (0.229 g, 1.00 mmol). Then the mix-
ture was heated to refluxing under agitation for 12 h in the atmosphere
of liquid nitrogen. After completing the reaction and cooling the reac-
tion mixture to 0 °C, the sediment was isolated by filtration, washing
with absolute ethanol (3 × 5 mL) to afford compound 1 as a gray white
solid (Scheme 1). Yield: 0.44 g (66.17%). m.p.: at least 300 °C. 1H NMR
(400 MHz, DMSO-d6) (Fig. S1): δ 10.18 (s, 1H, eNHe), 9.41 (s, 1H,
eNHe), 7.37 (s, 1H, H8), 7.35 (s, 1H, H9), 7.22 (d, J = 7.2 Hz, 1H, H7),
6.86 (d, J = 7.2 Hz, 1H, eCH]Ne), 6.51 (d, J = 5.7 Hz, 2H, H6), 6.47-
6.30 (m, 15H, H1,
5), 4.68 (s, 6H, eOCH2e), 2.69 (s, 3H,
2, 3, 4,
+
eCOCH3), 2.24 (s, 3H, eCH3). MS (ESI) (Fig. S2): m/z [M + H+
]
calcd 666.7043, found 666.0867; [M + Na+
]
calcd 688.6862, found
+
688.0592; [M + K+
]
calcd 704.7947, found 704.0249. FT-IR (KBr
+
pellet, cm−1) (Fig. S3): 3435 (s), 3065 (w), 2924 (w), 1699 (w), 1653
(m), 1612 (m), 1585 (m), 1501 (w), 1425 (w), 1404 (w), 1371 (w),
1344 (m), 1329 (m), 1240 (w), 1153 (w), 1117 (m), 1078 (w), 999 (w),
804 (w), 750 (w), 696 (w). Anal. Calcd. for C40H35N5O5 (%): C, 72.17;
H, 5.30; N, 10.52; O, 12.01. found: C, 71.11; H, 5.08; N, 10.32; O,
13.49.
2. Experimental
2.1. Materials and instrumentation
All reagents and raw materials were of analytically pure quality,
originated from chemcats, and utilized as received with no further
depuration needed. A microscopic melting point apparatus labeled as
Beijing XT4-100x was utilized for determining melting points with no
correction. Utilizing TMS (tetramethylsilane) as an interior label and
DMSO-d6 as a solvent, we utilized JNM-ECS 400 MHz instruments
spectrometers for recording 1H NMR spectra. A Bruker Esquire 6000
spectrometer was used to record mass spectra of the final product in
ethanol solution. A VERTEX-70 spectrometer with KBr disks was uti-
lized for acquiring FT-IR spectra (4000-400 cm−1). A VarioEL Cube
V1.2.1 analyzer was used to perform elemental analyses. A spectro-
photometer labeled as Shimadzu UV-240 equipped with a 1 cm length
quartz cells of optical path was utilized to obtain UV-vis absorption
spectra. A Hitachi RF-5301 fluorimeter was used for measuring fluor-
escence emission spectra at 298 K.
3. Results and discussion
3.1. UV–vis analysis
Firstly, the spectroscopic methods of UV–vis absorption and fluor-
escence emission were utilized for investigating the coordinative
properties of compound 1 towards cations in ethanol. For UV–vis ab-
sorption method shown in Fig. 1, two strong absorption bands of
compound 1 originally appeared at 353 nm and 367 nm in ethanol,
which were probably assigned to п-п* transitions [40–42]. However,
upon incremental addition of Zn2+, these two absorption bands de-
creased gradually with an appearance of a novel characteristic ab-
sorption band of n-п* transition which was centered at 431 nm [40–42],
inducing a clearly observed well-defined isosbestic point at 376 nm
(Fig. 1), which indicated that a stable complex bearing a certain ratio of
stoichiometry between compound 1 and Zn2+ ion was formed.
2.2. Synthesis
Synthesis of 7-amidyl-2,4-dimethyl-1,8-naphthyridine (2), 7-acet-
amidyl-2,4-dimethyl-1,8-naphthyridine (3) and 7-acetamidyl-4-methyl-
1,8-naphthyridine-2-aldehyde (4) was reported according to the pre-
vious method [38]. Synthetic route of the probe 1 was outlined in
Scheme 1.
3.2. Fluorescence study
Accompanying with these UV-vis absorption changes, the changes
in fluorescence emission of compound 1 upon addition of a series of
metal cations were also conducted in ethanol, and the corresponding
spectra were depicted in Fig. 2 (a). Almost no fluorescence emission
emerged in compound 1 alone when it was excited at 431 nm, but an
appearance of a new emission band centered at 504 nm accompanied
by a sharp enhancement (ca. 63-fold) in its intensity was obtained with
the addition of Zn2+. Nevertheless, no obvious changes in the emission
2.2.1. Synthesis of compound
1 (7-Acetamidyl-4-methyl-2-formyl-1,8-
naphthyridine trihydroxybenzoyl hydrazone)
Trihydroxybenzoyl hydrazine was synthesized on a basis of the
method reported previously [39]. An 10 mL of ethanolic solution of
trihydroxybenzoyl hydrazine (0.454 g, 1.00 mmol) was introduced into
232

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JournalofPhotochemistry&PhotobiologyA:Chemistry375(2019)231–236
Fig. 1. UV-vis absorption spectra of 1 (10 μM) in the presence of increasing
amounts of Zn2+ (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 equiv., respec-
tively) in ethanol.
Fig. 3. Change in fluorescence emission spectra of 1 (10 μM) upon addition of
various amounts of Zn2+ (0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45,
0.50, 0.60, 0.70, 0.80, 0.90, 1.00 equiv., respectively) in ethanol with an ex-
citation at 431 nm.
spectra were produced in the cases of other metal cations like Al3+
Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe2+, Hg2+, K+, Li+, Mg2+
,
,
it was nearly detectable (Fig. 2 (b) and Fig. S4). These results indicated
that most of other metal ions and counter-anions did not affect the
detection of Zn2+ by compound 1, and excellent selectivity of 1 to-
wards Zn2+ over most of other environmentally and biologically im-
portant metal cations and counter-anions was confirmed, which pro-
vided the utility of this compound 1 for practical applications.
Mn2+, Na+, Ni2+ and Pb2+ under the identical conditions (Fig. 2 (a)),
which suggested that the significant enhancement in fluorescence
emission was only caused by Zn2+, thereby providing the method of
sensing Zn2+ by compound 1 with excellent selectivity.
To study the influences of other various metal ions and counter-
anions on the binding property of compound 1 with Zn2+, 1 equiv. of
Zn2+ mixing with 5 equiv. of other metal cations or counter-anions was
introduced into the ethanolic solution of 1. As illustrated in Fig. 2 (b)
and Fig. S4, emission quenching of fluorescence was observed upon
mixing of Zn2+ with Co2+, Cr3+, Cu2+ and Fe2+, and the fluorescence
emission intensity at 504 nm also decreased to a certain degree in 1-
Zn2+ solution in the existence of Mg2+, Mn2+ and Al3+. Nevertheless,
the intensity of fluorescence emission at 504 nm of 1-Zn2+ in the ex-
istence of other metal cations and counter-anions was nearly identical
Subsequently, we carried out the fluorescence titration experiments
for binding compound 1 with Zn2+ in ethanol. As illustrated in Fig. 3,
negligible emission band of fluorescence was observed in compound 1
alone with excited at 431 nm. However, the gradual addition of Zn2+ to
compound 1 solution led to an appearance of a new band of emission
centered at 504 nm accompanied by the enhancive intensity. Moreover,
a plateau was reached in intensity of fluorescence emission at 504 nm
with addition of 0.5 equiv. of Zn2+ (Fig. 3), giving a solid evidence for a
2:1 coordinative stoichiometry of compound 1 with Zn2+. The above
fluorescence titration experiments gave an excellent linear dependence
between the intensity of fluorescence emission at 504 nm and Zn2+
concentration over its range from 0.5 nM to 5.0 nM (R2 = 0.9762), from
which we calculated the LOD value of 1 for the analysis of Zn2+ to be
7.52 nM (Fig. S5), and it was sufficiently below the mutable Zn2+
amount in human bodies [45]. From the results above, the extremely
to that of 1-Zn2+ alone. As for as Co2+, Cr3+, Cu2+, Fe2+ and Mn2+
,
these five metal cations bearing the paramagnetic properties have
pronounced quenching effects on fluorophores due to the mechanism
about the electron or energy transfer from photoinduced metal cation to
fluorophore [43,44]. However, another two metal cations (Mg2+ and
Al3+) slightly interfered with the detection of Zn2+ by compound 1, but
Fig. 2. (a) Changes in fluorescence emission spectra of 1 (10 μM) upon addition of Zn2+ (1 equiv.) and other respective metal ions (5 equiv.) in ethanol with an
excitation at 431 nm. (b) Fluorescence responses at 504 nm of 1 (10 μM) to Zn2+ (1 equiv.) and other various interfering metal ions (5 equiv.) under identical
conditions in ethanol. Black bar: 1 + other metal ions (50 μM), red bar: 1 + other metal ions (50 μM) + Zn2+ (10 μM). (λex = 431 nm, slit: 5.0/5.0 nm).
233

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JournalofPhotochemistry&PhotobiologyA:Chemistry375(2019)231–236
Fig. 5. Change in fluorescence emission spectra of compound 1 (10 μM) upon
incremental addition of Zn2+ (1 equiv.) and EDTANa2 (1 equiv.) in ethanol with
an excitation at 431 nm.
Fig. 4. A Job’s plot for determining the binding stoichiometry between 1 and
Zn2+ in ethanol (XZn = [Zn2+]/([Zn2+] + [1]), the total concentration of 1
and Zn2+ was 20 μM).
observed in the spectra (Fig. S7). From the results above, it was con-
cluded that two nitrogen atoms from the naphthyridine unit in com-
pound 1 participated in the coordination with Zn2+, forming a stable
high sensitivity of compound 1 towards Zn2+ was concluded for sensing
and monitoring Zn2+ environmentally and biologically.
complex 1-Zn2+
.
A Job’s plot method was further utilized for demonstrating the co-
ordinative stoichiometry of compound 1 with Zn2+ by keeping the total
concentration of 1 and Zn2+ homeostasis at 20 μM and changing the
Zn2+ molar number ratio in complex 1-Zn2+, and the intensity of
fluorescence emission at 504 nm was plotted as a function of Zn2+
molar number ratio. As shown in Fig. 4, the maximum was reached in
the intensity of fluorescence emission at 504 nm at Zn2+ molar number
ratio of 0.33, proving a 2:1 coordinative stoichiometry of compound 1
with Zn2+ in ethanol. The 2:1 binding stoichiometry encouraged us to
calculate the association constant (K) between 1 and Zn2+ on a basis of
nonlinear Benesi-Hildebrand expression from the fluorescence titration
experiments, giving the result as 1.14 × 105 M−1 (Fig. S6), which was
within the range 103 - 109 M-1 of other Zn2+ fluorescent probes re-
ported previously in the literature and suggested good selective nature
of compound 1 with Zn2+ [46–49].
On a basis of the investigations above, the proposed binding me-
chanism of compound 1 with Zn2+ was deduced in detail. As depicted
in Scheme 2, owing to the 2:1 coordinative stoichiometry of compound
1 with Zn2+, 1 formed a stable complex by coordinating four nitrogen
atoms from the naphthyridine units in two molecules of 1 with Zn2+
,
which enhanced the rigidity and coplanarity of this system forming the
chelation-enhanced fluorescence (CHEF) effect. Furthermore, the pho-
toinduced electron-transfer (PET) phenomenon from the lone pair
electron of nitrogen atom to the naphthyridine unit was inhibited upon
complexation of compound 1 with Zn2+ (Scheme 2). As a result, sig-
nificant enhancement in the band of fluorescence emission centered at
504 nm was observed.
4. Conclusion
Invertibility and renewability are important characters for broad-
ening a fluorescent probe for actual applicability. So as to explore if
good invertibility and renewability of our as-synthesized compound 1
for sensing Zn2+ were confirmed, EDTANa2, which was a perfect che-
lating agent for binding Zn2+, was introduced into the ethanolic solu-
tion of 1 in the existence of Zn2+. From the spectra of fluorescence
emission of compound 1 in the existence of Zn2+ followed by the ad-
dition of EDTANa2 shown in Fig. 5, we could clearly observe that the
fluorescence emission of complex 1-Zn2+ quenched significantly with
addition of EDTANa2, which was attributed to the stronger coordina-
tion ability of Zn2+ with EDTANa2 than with compound 1, making
EDTANa2 coordinated with Zn2+ from complex 1-Zn2+ and releasing
the free 1. From the results above, we could conclude that perfect in-
vertibility and renewability of our as-synthesized compound 1 for
sensing Zn2+ were confirmed, which developed 1 for practical appli-
cations.
In conclusion, we designed and synthesized a new-type Schiff-base
ligand 1 with 4-methyl-7-acetamide-1,8-naphthyridyl group as the
fluorophore and the receptor for sensing Zn2+. This compound 1
showed excellent selectivity towards Zn2+ over most of other en-
vironmentally and biologically important metal cations, which was
because that the remarkable enhancement in fluorescence emission
centered at 504 nm was only caused by Zn2+, increasing by about 63-
fold in its intensity, and most of other metal cations did not affect the
detection of Zn2+ by compound 1. Moreover, the extremely high sen-
sitivity of compound 1 towards Zn2+ was concluded, for the LOD value
reaching 7.52 nM, and a 2:1 coordinative stoichiometry of compound 1
with Zn2+ was ascertained by the experiments of fluorescence titration
and a Job’s plot method. Additionally, perfect invertibility and re-
newability of our as-synthesized compound 1 for sensing Zn2+ were
confirmed, which developed 1 for practical applications. Therefore, the
development of novel fluorescent probes might be accelerated by the
design and synthesis of compound 1 for detecting various analytes in
environmental and biological systems.
3.3. Binding mode of compound 1 with Zn2+
So as to investigate the binding mode of compound 1 with Zn2+
,
Fourier Transform Infrared (FT-IR) spectra of compound 1 and complex
1-Zn2+ were carried out. As can be seen from Fig. S7, the free com-
pound 1 exhibited a characteristic stretching vibration band of C =
centered at 1612 cm−1, which was red-shifted to 1585 cm−1 upon
complexation of 1 with Zn2+. Additionally, a new absorption band
centered at 419 cm−1 emerged, which was probably assigned to Zn-N
absorption band, but negligible changes in other absorption bands were
Acknowledgments
This work was supported by the National Natural Science
Foundation of China (21761019) and the Young Foundation of
Jinchang (jrc201811).
234

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JournalofPhotochemistry&PhotobiologyA:Chemistry375(2019)231–236
Scheme 2. Proposed binding mechanism for the response of 1 to Zn2+
.
Appendix A. Supplementary data
oxyimine-based macrocyclic dinuclear zinc(II) complexes enhances phosphate ester
hydrolysis, DNA binding, DNA hydrolysis, and lactate dehydrogenase inhibition
and induces apoptosis, Inorg. Chem. 51 (2012) 5580–5592.
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jphotochem.2019.02.
024.
[18] L.Z. Gai, H.C. Chen, B. Zou, H. Lu, G.Q. Lai, Z.F. Li, Z. Shen, Ratiometric fluores-
cence chemodosimeters for fluoride anion based on pyrene excimer/monomer
transformation, Chem. Commun. 48 (2012) 10721–10723.
[19] V.K. Gupta, A.K. Singh, M.R. Ganjali, P. Norouzi, F. Faridbod, N. Mergu,
Comparative study of colorimetric sensors based on newly synthesized Schiff bases,
Sensor. Actuators B-Chem. 182 (2013) 642–651.
References
[20] P.S. Hariharan, A. Sivasubramanian, S.P. Anthony, Off-on fluorescent sensor from
on-off sensor: exploiting silver nanoparticles influence on the organic fluorophore
fluorescence, J. Fluoresc. 24 (2014) 319–327.
[21] S.F. Sousa, P.A. Fernandes, M.J. Ramos, The carboxylate shift in zinc enzymes: a
computational study, J. Am. Chem. Soc. 129 (2007) 1378–1385.
[22] K. Komatsu, Y. Urano, H. Kojima, T. Nagano, Development of an iminocoumarin-
based zinc sensor suitable for ratiometric fluorescence imaging of neuronal zinc, J.
Am. Chem. Soc. 129 (2007) 13447–13454.
[23] Y. Zhang, X.F. Guo, W.X. Si, L.H. Jia, X.H. Qian, Ratiometric and water-soluble
fluorescent zinc sensor of carboxamidoquinoline with an alkoxyethylamino chain as
receptor, Org. Lett. 10 (2008) 473–476.
[24] R.C.H. Wong, P.C. Lo, D.K.P. Ng, Stimuli responsive phthalocyanine-based fluor-
escent probes and photosensitizers, Coord. Chem. Rev. 379 (2019) 30–46.
[25] J.K.H. Wong, M.H. Todd, P.J. Rutledge, Recent advances in macrocyclic fluorescent
probes for ion sensing, Molecules 22 (2017) 200.
[26] S.L. Shen, X.Q. Huang, H.L. Jiang, X.H. Lin, X.Q. Cao, A rhodamine B-based probe
for the detection of HOCl in lysosomes, Anal. Chim. Acta 1046 (2019) 185–191.
[27] P. Qu, X.H. Ma, W.S. Chen, D.D. Zhu, H.F. Bai, X.H. Wei, S. Chen, M.T. Xu, A
coumarin-based fluorescent probe for ratiometric detection of hydrazine and its
application in living cells, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 210
(2019) 381–386.
[28] T. Mistri, M. Dolai, D. Chakraborty, A.R. Khuda-Bukhsh, K.K. Das, M. Ali, A highly
selective and sensitive in vivo fluorosensor for zinc(II) without cytotoxicity, Org.
Biomol. Chem. 10 (2012) 2380–2384.
[29] M. Taki, J.L. Wolford, T.V. O’Halloran, Emission ratiometric imaging of in-
tracellular zinc: design of a benzoxazole fluorescent sensor and its application in
two-photon microscopy, J. Am. Chem. Soc. 126 (2004) 712–713.
[30] Y.L. Cai, X.M. Meng, S.X. Wang, M.Z. Zhu, Z.W. Pan, Q.X. Guo, A quinoline based
fluorescent probe that can distinguish zinc(II) from cadmium(II) in water,
Tetrahedron. Lett. 54 (2013) 1125–1128.
[31] J.S. Wu, W.M. Liu, J.C. Ge, H.Y. Zhang, P.F. Wang, New sensing mechanisms for
design of fluorescent chemosensors emerging in recent years, Chem. Soc. Rev. 40
(2011) 3483–3495.
[1] X. Xie, T.G. Smart, A physiological role for endogenous zinc in rat hippocampal
synaptic neurotransmission, Nature 349 (1991) 521–524.
[2] J.M. Berg, Y. Shi, The galvanization of biology: a growing appreciation for the roles
of zinc, Science 271 (1996) 1081–1085.
[3] R.K. Pathak, V.K. Hinge, A. Rai, D. Panda, C.P. Rao, Imino-phenolic-pyridyl con-
jugates of calix[4]arene (L1 and L2) as primary fluorescence switch-on sensors for
Zn2+ in solution and in HeLa cells and the recognition of pyrophosphate and ATP
by [ZnL2], Inorg. Chem. 51 (2012) 4994–5005.
[4] M. Hagimori, T. Uto, N. Mizuyama, T. Temma, Y. Yamaguchi, Y. Tominaga, H. Saji,
Fluorescence ON/OFF switching Zn2+ sensor based on pyridine–pyridone scaffold,
Sensor. Actuators B-Chem. 181 (2013) 823–828.
[5] J.H. Kim, I.H. Hwang, S.P. Jang, J. Kang, S. Kim, I. Noh, Y. Kim, C. Kim,
R.G. Harrison, Zinc sensors with lower binding affinities for cellular imaging,
Dalton Trans. 42 (2013) 5500–5507.
[6] D.J. Eide, Zinc transporters and the cellular trafficking of zinc, BBA-Mol. Cell. Res.
1763 (2006) 711–722.
[7] M. Murakami, T. Hirano, Intracellular zinc homeostasis and zinc signaling, Cancer.
Sci. 99 (2008) 1515–1522.
[8] T.E. Kehl-Fie, E.P. Skaar, Nutritional immunity beyond iron: a role for manganese
and zinc, Curr. Opin. Chem. Biol. 14 (2010) 218–224.
[9] M.Z. Khan, A possible significant role of zinc and GPR39 zinc sensing receptor in
Alzheimer disease and epilepsy, Biomed. Pharmacother. 79 (2016) 263–272.
[10] K.B. Kim, H. Kim, E.J. Song, S. Kim, I. Noh, C. Kim, A cap-type Schiff base acting as
a fluorescence sensor for zinc(II) and a colorimetric sensor for iron(II), copper(II),
and zinc(II) in aqueous media, Dalton Trans. 42 (2013) 16569–16577.
[11] H.G. Lee, J.H. Lee, S.P. Jang, I.H. Hwang, S.J. Kim, Y. Kim, C. Kim, R.G. Harrison,
Zinc selective chemosensors based on the flexible dipicolylamine and quinoline,
Inorg. Chim. Acta. 394 (2013) 542–551.
[12] K.M. Hambidge, Zinc and diarrhea, Acta. Paediatr. 81 (1992) 82–86.
[13] M. Hambidge, Human zinc deficiency, J. Nutr. 130 (2000) 1344S–1349S.
[14] A. Nakayama, M. Hiromura, Y. Adachi, H. Sakurai, Molecular mechanism of anti-
diabetic zinc-allixin complexes: regulations of glucose utilization and lipid meta-
bolism, J. Biol. Inorg. Chem. 13 (2008) 675–684.
[15] H. Sakurai, Y. Yoshikawa, H. Yasui, Current state for the development of metallo-
pharmaceutics and anti-diabetic metal complexes, Chem. Soc. Rev. 37 (2008)
2383–2392.
[16] M.T. Kaczmarek, R. Jastrzab, E. Hołderna-Kedzia, W. Radecka-Paryzek, Self-as-
sembled synthesis, characterization and antimicrobial activity of zinc(II) salicy-
laldimine complexes, Inorg. Chim. Acta. 362 (2009) 3127–3133.
[17] S. Anbu, S. Kamalraj, B. Varghese, J. Muthumary, M. Kandaswamy, A series of
[32] Y.T. Wu, J.L. Zhao, L. Mu, X. Zeng, G. Wei, C. Redshaw, Z.W. Jin, A 2-styryl-1,8-
naphthyridine derivative as a versatile fluorescent probe for the selective recogni-
tion of Hg2+, Ag+ and F− ions by tuning the solvent, Sensor. Actuators B-Chem.
252 (2017) 1089–1097.
[33] M. Li, H.Y. Lu, R.L. Liu, J.D. Chen, C.F. Chen, Turn-on fluorescent sensor for se-
lective detection of Zn2+, Cd2+, and Hg2+ in water, J. Org. Chem. 77 (2012)
3670–3673.
[34] Q.Q. Zhang, B.X. Yang, R. Sun, J.F. Ge, Y.J. Xu, N.J. Li, J.M. Lu, A near-infrared
phenoxazinium-based fluorescent probe for zinc ions and its imaging in living cells,
235

C.-r. Li, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry375(2019)231–236
imaging, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 205 (2018) 410–418.
[42] J. Nie, N. Li, Z.H. Ni, Y. Zhao, L.F. Zhang, A sensitive tetraphenylethene-based
fluorescent probe for Zn2+ ion involving ESIPT and CHEF processes, Tetrahedron
Lett. 58 (2017) 1980–1984.
[43] J.M. An, M.H. Yan, Z.Y. Yang, T.R. Li, Q.X. Zhou, A turn-on fluorescent sensor for
Zn(II) based on fluorescein-coumarin conjugate, Dyes Pigments 99 (2013) 1–5.
[44] D. Maity, T. Govindaraju, Conformationally constrained (coumarin-triazolyl-bi-
pyridyl) click fluoroionophore as a selective Al3+ sensor, Inorg. Chem. 49 (2010)
7229–7231.
Sens. Actuators B-Chem. 171–172 (2012) 1001–1006.
[35] Y. Zhou, Z.X. Li, S.Q. Zang, Y.Y. Zhu, H.Y. Zhang, H.W. Hou, T.C.W. Mak, A novel
sensitive turn-on fluorescent Zn2+ chemosensor based on an easy to prepare C3-
symmetric Schiff-base derivative in 100% aqueous solution, Org. Lett. 14 (2012)
1214–1217.
[36] S. Djurdjevic, D.A. Leigh, H. McNab, S. Parsons, G. Teobaldi, F. Zerbetto, Extremely
strong and readily accessible AAA-DDD triple hydrogen bond complexes, J. Am.
Chem. Soc. 129 (2007) 476–477.
[37] J.L. Katz, B.J. Geller, P.D. Foster, Oxacalixarenes and oxacyclophanes containing
1,8-naphthyridines: a new class of molecular tweezers with concave-surface func-
tionality, Chem. Commun. (2007) 1026–1028.
[38] Z.X. Li, W.Y. Zhao, X.Y. Li, Y.Y. Zhu, C.M. Liu, L.N. Wang, M.M. Yu, L.H. Wei,
M.S. Tang, H.Y. Zhang, 1,8-Naphthyridine-derived Ni2+/Cu2+-selective fluorescent
chemosensor with different charge transfer processes, Inorg. Chem. 51 (2012)
12444–12449.
[45] S. Tajik, M.A. Taher, A new sorbent of modified MWCNTs for column pre-
concentration of ultra trace amounts of zinc in biological and water samples,
Desalination 278 (2011) 57–64.
[46] S.A. Yoon, J. Lee, M.H. Lee, A ratiometric fluorescent probe for Zn2+ based on
pyrene-appended naphthalimide-dipicolylamine, Sensor. Actuators B-Chem. 258
(2018) 50–55.
[39] P. Rajamalli, E. Prasad, Luminescent micro and nanogel formation from AB3 type
poly(aryl ether) dendron derivatives without conventional multi-interactive gela-
tion motifs, New J. Chem. 35 (2011) 1541–1548.
[40] H. Zhang, T. Sun, Q. Ruan, J.L. Zhao, L. Mu, X. Zeng, Z.W. Jin, S.B. Su, Q.Y. Luo,
Y.Y. Yan, C. Redshaw, A multifunctional tripodal fluorescent probe for the re-
cognition of Cr3+, Al3+, Zn2+ and F− with controllable ESIPT processes, Dyes.
Pigments. 162 (2019) 257–265.
[47] K. Yao, J.X. Fu, Y.X. Chang, B. Li, L. Yang, K.X. Xu, A selective fluorescent probe for
relay detection of Zn2+ and tartrate: Application to logic circuit and living cell
imaging, Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 205 (2018) 410–418.
[48] G.F. Wu, Q. Gao, M.X. Li, X. Tang, K.W.C. Lai, Q.X. Tong, A ratiometric probe based
on coumarin-quinoline for highly selective and sensitive detection of Zn2+ ions in
living cells, J. Photochem. Photobiol. A-Chem. 355 (2018) 487–495.
[49] J. Nie, N. Li, Z.H. Ni, Y. Zhao, L.F. Zhang, A sensitive tetraphenylethene-based
fluorescent probe for Zn2+ ion involving ESIPT and CHEF processes, Tetrahedron
Lett. 58 (2017) 1980–1984.
[41] K. Yao, J.X. Fu, Y.X. Chang, B. Li, L. Yang, K.X. Xu, A selective fluorescent probe for
relay detection of Zn2+ and tartrate: Application to logic circuit and living cell
236