A functional applied material on recognition of metal ion zinc based on the double azine compound

Article abstract of DOI:10.1016/j.tet.2017.04.001

A colorimetric and fluorescent probe L has been designed and synthesized, which bearing the double azine moiety and showing a detection limit of 2.725?×?10^?7?M towards Zn²⁺. Based on the basic recognition mechanism of ESIPT and CHEF effect, the L has high selectivity and sensitivity to only Zn²⁺ (not Fe³⁺, Hg²⁺, Ag⁺, Ca²⁺, Co²⁺, Ni²⁺, Cd²⁺, Pb²⁺, Cr³⁺, and Mg²⁺) within the physiological pH range (pH?=?7.0–8.4) and showed a fluorescence switch. Moreover, this detection progress occured in the DMSO/H₂O?～?HEPES buffer (80/20, v/v; pH 7.23) solution which can conveniently used on test strip.

Full text of DOI:10.1016/j.tet.2017.04.001

Accepted Manuscript
A functional applied material on recognition of metal ion zinc based on the double
azine compound
Taibao Wei, Guoyan Liang, Xiaopeng Chen, Jin Qi, Qi Lin, Youming Zhang, Hong
Yao
PII:
S0040-4020(17)30364-2
10.1016/j.tet.2017.04.001
TET 28602
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 11 December 2016
Revised Date: 28 March 2017
Accepted Date: 1 April 2017
Please cite this article as: Wei T, Liang G, Chen X, Qi J, Lin Q, Zhang Y, Yao H, A functional applied
material on recognition of metal ion zinc based on the double azine compound, Tetrahedron (2017), doi:
10.1016/j.tet.2017.04.001.
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ACCEPTED MANUSCRIPT
Graphical Abstract
A Functional Applied Material on Recognition of Metal Ion Zinc Based on the
Double Azine Compound
Taibao Wei*, Guoyan Liang, Xiaopeng Chen, Jin Qi, Qi Lin, Youming Zhang, Hong Yao
Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education , Gansu 730070, PR
China
A colorimetric and fluorescent probe L has been designed and synthesized, bearing the double azine
moiety and showing a detection limit of 2.725 × 10-7 M towards Zn2+. Based on the basic recognition
mechanism of ESIPT and CHEF effect, the probe owes high selectivity and sensitivity to only Zn2+ (not
Fe3+, Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+, Pb2+, Cr3+, and Mg2+) within the physiological pH range (pH =
7.0 – 8.4) and showed a fluorescence switch. Moreover, this detection progress occur in the DMSO/H2O
~ HEPES buffer (80/20, v/v; pH 7.23) solution which can conveniently used on test strip, and it can anti
interference of others.

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
A Functional Applied Material on Recognition of Metal Ion Zinc Based on the Double
Azine Compound
Taibao Weia,*, Guoyan Lianga, Xiaopeng Chena,Jin Qia, Qi Lina, Youming Zhanga, Hong Yaoa
a Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education , Gansu 730070, PR China
b Key Laboratory of Polymer Materials, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou, Gansu 730070, PR China
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
A colorimetric and fluorescent probe L has been designed and synthesized, which bearing
the double azine moiety and showing a detection limit of 2.725 × 10-7 M towards Zn2+.
Based on the basic recognition mechanism of ESIPT and CHEF effect, the L has high
selectivity and sensitivity to only Zn2+ (not Fe3+, Hg2+, Ag+, Ca2+, Co2+, Ni2+, Cd2+, Pb2+,
Cr3+, and Mg2+) within the physiological pH range (pH = 7.0 – 8.4) and showed a
fluorescence switch. Moreover, this detection progress occured in the DMSO/H2O ~
HEPES buffer (80/20, v/v; pH 7.23) solution which can conveniently used on test strip.
Available online
Keywords:
fluorescent probe;
double azine;
fluorescence switch;
test strip.
1. Introduction
Due to the effects of metal ions in the environment and human
health, there are many selective chemo probes for these metal
ions have been developed1. Living system and natural human
health need quantitative intakes of most of the metal ions
including heavy metal ions2-4. Zinc is one of the essential trace
metal elements in the human body like ferrum5 and copper6,
which occupies an important position in various chemical,
environmental and physiological systems. Although the majority
of the biological zinc ions are tightly sequestered by proteins,
free Zn2+ pools containing large amounts of Zn2+ exist in certain
tissues, for example, high concentrations up to 0.1 - 0.5 mM of
Zn2+ have been reported in brain tissues7. Moreover, the
unregulated zinc level in the body may lead to a number of
severe neurological diseases (e.g. Alzheimer’s disease and
epilepsy)8-11. Thus, the detection and recognition for the metal
ion zinc are necessary, and we need various convenient methods
or chemical molecules to realize it. For example, Yang Wei and
his coworkers12 synthesised a Europium-based luminescent
chemo probes for Zn2+ with quinoxaline; and Ajay Misra’s group
constructed a hydrazine to detect Zn2+13. And it is imperative to
search for more practical fluorescent probes for selective
detection of zinc.
emission spectrometry15 and electrochemical methods16. This
techniques employ convenient approaches to realize more
accurate detection. And several methods require tedious sample
preparation procedures, sophisticated instrumentation and trained
operators. Fluorescence technology provides a convenient and
ordinary method in the context of sensing of environmentally
and biologically pertinent metal ions17. The literature reported
one kind of fluorescent probes is composed of azine compounds.
Azine is a special kind of conjugate schiff base, which is a
general term for unsaturated six membered heterocyclic or
heteroatom compounds containing one or more nitrogen atoms.
There are many kinds of compounds which process some
structural similarity to the Azine compounds, such as pyridine,
pyrimidine, triazine and thiophene, have being attached
attentions in recent years18.
The structures of nitrogen atoms which contain lone pair
electrons, can lead to the formation of coordination effect with
many metals owing their outer space orbits. Supplemented by the
ortho-oxygen and sulfur atoms on this kind of compounds, the
research on it complied in the field of fluorescence detection
becomes more and more active19. Azine, as a kind of
fluorescence probe, contains great opportunity of sensitivity,
selectivity, real-time and in situ detection effect20. On the other
hand, Azine compounds as a kind of organic molecules, process
great advantages in the fields of molecular design and structural
characterization. And can employ its own distinctive chemical
bonds, coordination bonds and unique spatial molecular
Field application requires the techniques which process
wonderful selectivity, speedy sensitivity, consistency, and
exclusively easy operation. Various methods have been reported
to detect both the metal ions and anions such as atomic
absorption spectroscopy14, inductively coupled plasma atomic

2
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ACCEPTED MANUSCRIPT
conformation to selectively bind with specific metal ions,
which shows high recognition ability and have attracted great
interest of researchers21. According to these researches have been
made, we synthesised a dialdehyde azine compound (L), which
showed great opportunity of sensitivity and selectivity in the
progress of detecting the metal ion Zn2+.
2. Results and discussion
The synthesis course of chemical probe L was depicted in
Scheme S1 and operation details were described in experimental
section in the supporting information. It was fully characterized
by spectroscopic analysis and mass-spectrography. The 1H NMR
and 13C NMR (Figure S1-S6) spectra were used to confirm the
structure and the purity of the probe. The ESI−MS (Figure S7)
spectrum showed the major peak at m/z 385.1021 [M − H]-,
which perfectly matched the estimated molecular weight of
[C22H17N4O3 - H]-. IR (Figure S8) spectrum for the molecule L
showed a vibration band at 1654 cm−1 assigned to stretching
vibrational mode of imine (−CH=N−) groups and a broad peak at
3469 cm−1 assigned to stretching vibrational mode of hydroxyl
(−OH) groups.
In the fluorescence experiments of the probe L responsing to
Zn2+, we selected the DMSO/H2O ~ HEPES buffer (80/20, v/v;
pH 7.23) as solution for the target of excluding the possibility in
fluence of pH fluctuation. As shown in Fig. 1, the L had no
fluorescent nature with the excitation wavelength was at 425 nm,
but an unique and new emission peak appeared at 520 nm when
added 20 equiv. of Zn2+ into the solution of L, and the color of
this complex shew fluorescently green.
Fig. 2 Fluorescence spectra of probe L (2 × 10-5 mol •L-1) with
various cations (Fe3+, Hg2+, Ag+, Ca2+, Cu2+, Co2+, Ni2+, Cd2+,
Pb2+, Zn2+, Cr3+ and Mg2+) in DMSO/H2O ~ HEPES buffer
(80/20, v/v; pH = 7.23) solutions. Inset: color changes of L with
various anions.
The probe L could act as a functional material for the detection
of Zn2+ in DMSO/H2O ~ HEPES buffer (80/20, v/v; pH = 7.23)
solutions. For instance, only Zn2+ (4.0 ×10-4 mol •L-1) could open
the fluorescence emission of L, not other various ions when
adding them into 2 × 10-5 mol •L-1 solutions of L. Moreover, as
shown in Fig. 3, the fluorescence emission at 520 nm increased
when gradually added the Zn2+ into this solution of probe . The
detection limit of L to Zn2+ is estimated to be 2.725 × 10-7 M.
Meanwhile, the fluorimetric detection limit of Zn2+ by the naked
eye for probe L was also tested. As shown in Fig. 4, under an
UV lamp at 360 nmthe minimum concentration of Zn2+ for the
fluorescence color change, observed by the naked eye was 2.0×
10-5 M.
800
42.8 equiv.
600
Zn2+
400
200
0.0 equiv.
0
500
600
Fig. 1 Fluorescence spectra of the probe L (2 × 10-5 mol• L-1)
Wavelength (nm)
with adding Zn2+ in DMSO/H2O ~ HEPES buffer (8/2, v/v; pH =
Fig. 3 Fluorescence spectral changes of L (c = 2 × 10-5 M) in the
presence of different concentrations of Zn2+ ions in DMSO/H2O~
HEPES buffer (80/20, v/v; pH = 7.23) solutions.
7.23) solution. Inset: color changes of L and with Zn2+
.
To find the response property of the probe L to other various
cations, such as Fe3+, Hg2+, Ag+, Ca2+, Cu2+, Co2+, Ni2+, Cd2+,
Pb2+, Cr3+ and Mg2+, we added these cations according to the
priority to DMSO/H2O ~ HEPES buffer (80/20, v/v; pH 7.23)
solutions of probe L no significant color or spectrum changes
were observed ( Fig. 2). Which Suggested that the probe L was a
special recognition subject for Zn2+
.
Fig. 4 Naked-eye detection limit under an UV lamp at 365 nm.
From left to right, the concentration of Zn2+ were 0; 2.0 ×10-6
mol•L-1; 2.0 × 10-5 mol • L-1, 2.0 × 10-4 mol • L-1, and 2.0 × 10-3
mol •L-1.

3
Although the probe L exhibited the single colorimetric and
ACCEPTED MANUSCRIPT
fluorescent recognition ability for Zn2+, the ability of detecting
metal cations selectively over other competing metal cations was
an essential aspect for many prospective chemical probes. In
order to utilize compound L as a Zn2+ ion-selective fluorescence
probe, competition experiments were made at the presence of
Zn2+ (10 ꢀM) mixed with 10 ꢀM of another cations. As shown in
Fig. 5, there was no significant interference when we used the
probe L to detect Zn2+ at the presence of many competitive metal
cations and all of the solutions containing Zn2+ shew green
under an UV lamp at 360 nm. The results showed that the
complex state of the probe L with Zn2+ was almost unaffected by
the exists of other cations.
Fig. 6 PH value affected the charge distribution of receptor L
and L + Zn2+.
Fig. 5 Fluorescence intensity changes of the L (20 ꢀM) to Zn2+
(20 equiv.) in the presence of various test cations (20 equiv.) in
DMSO/H2O~ HEPES buffer (80/20, v/v; pH = 7.23) solutions.
Key: left to right, (1) only L, L + Zn2+, (2) L + Fe3+, L + Zn2++
Fe3+ ; (3) L + Hg2+, L + Zn2+ + Hg2+; (4) L + Ag+, L + Zn2+
+
Ag+; (5) L + Ca2+,L + Zn2+ + Ca2+; (6) L + Cu2+, L + Zn2+
Cu2+ ; (7) L + Co2+, L + Zn2+ + Co2+; (8) L + Ni2+, L + Zn2+
+
+
+
Ni2+; (9) L + Cd2+, L + Zn2+ + Cd2+; (10) L + Pb2+, L + Zn2+
Fig. 7 Fluorescence intensity absorption switching cycles of L (2
× 10-5 mol ꢁ L-1) controlled by alternating addition of EDTA and
Zn2+ in DMSO/H2O (v/v, 80/20).
Pb2+; (11) L + Cr3+, L + Zn2+ + Cr3+ and (12) L + Mg2+, L+ Zn2+
+ Mg2+.
On account of this, it was notable that the probe L not only
could be treated as a ‘‘turn-on’’ probe for Zn2+ but successfully
differentiated Zn2+ from Cd2+, which had always been a difficult
problem to solve in the past23, 24. In order to accurately study the
specific reasons for the opening of fluorescence of the probe L ,
Since the charge distribution of the probe L could be influenced
by pH value and its inherent fluorescence properties could be
changed within a range of pH fluctuation. The response property
of probe L were discussed by adding a certain volume HEPES
buffered solutions with various pH values into the DMSO
solution of L, respectively (pH ranged from 2.0 to 13.0, the step-
size was 1.0 pH unit). As clearly showed in Fig. 6, the complex
of L-Zn2+ demonstrated a significant fluorescence response
between pH 7 and 11, including the physiologically relevant
range of pH 7.0–8.4. These results suggested that Zn2+ could be
clearly detected by the fluorescence spectral measurement using
L within the physiological pH range (pH = 7.0–8.4)22 and this
properties made L act as a pH controlled alkalescent fluorescent
switch.
1
the H NMR titration experiments were carried out in the d6-
DMSO at the concentration of 15 mM when encountered the ion
Zn2+. As specially marked and showed in the Fig. S9, the
chemical peaks for protons lacated at the phenolic hydroxyl
gradually shift upfield on NMR time scale when the Zn2+ were
added quantificationally, and the chemical peaks of protons on
the hydrazone slightly shifted downfield simultaneously. These
result suggested that the cloud density around the phenolic
hydroxyl proton changed from relatively small to large because
of the weakening of N-H hydrogen bonds, and this weakening
was caused by the coordination effect between the outer lone
pair electrons on nitrogen atoms and the space orbits on zinc
cations. And it was correlative with the preferential fluorescence
enhancement for Zn2+ which might be caused by the formation of
a chelate complex (rigid system) between L and the Zn2+ because
of the chelation-enhanced fluorescence (CHEF) effect25.
Additionally, compound L was originally poor fluorescent due to
the two possible effects: (Ι) the isomerization of –HC=N– double
bonds occur in the excited state26 and (Π) excited-state
intramolecular proton transfer (ESIPT)27-32. And the ESI-MS
Better applicability needed kinds of methods to be confirmed.
The addition of EDTA to the probe L showed that the process of
titrating probe L with EDTA was reversible, and the reversible
process could be repeated at least five times (Fig.7).

4
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ACCEPTED MANUSCRIPT
spectrum for the strong florescent complex also shown an
Fig. 9 Fluorescence change of the test strips of L (a. Only L (1 ×
obvious peak at m/z 452.3257 assignable to [L + Zn2+ + H+](Fig.
S10).
10-3 M ); (b. after immersion into DMSO/H2O ~ HEPES buffer
(80/20, v/v; pH = 7.23) solutions with Zn2+; (c. after immersion into
DMSO/H2O~ HEPES buffer (80/20, v/v; pH = 7.23) solutions with
Cd2+; (d. after immersion into DMSO/H2O~ HEPES buffer (80/20,
v/v; pH = 7.23) solutions with Zn2+ and Cd2+ under irradiation at 254
nm. Among them: test strips selectively fluorimetric and
colorimetric detect.
Besides, in order to obtain the fluorescence quantum yields for both
L and L with Zn2+, we used Rhodamine-B (c = 2 × 10 -6M) as a
reference standard sample to figure out these values. Finally, the
fluorescence quantum yields for L and L with Zn2+ were concluded
to be 8.94% and 83.6% respectively.
In summary, herein we have synthesized and characterized a
new simple and inexpensive fluorescent probe L which
contained double azine moiety. It always exhibited swift and
wonderful sensitivity toward Zn2+ through
a
palpable
colorimetric and turn-on fluorescence response with the
detection limit towards Zn2+ was 2.725 × 10-7 M. The novel
chemical probe L not only had a very good practicality in the
living body, but also had a significant fluorescent open
repeatability with EDTA. The further study for fluorescent probe
needs correlative support such as this kind of azine derivatives
and we wish great development on it would be made.
Fig. 8 A possible sensing mechanism of the the probe L to Zn2+
.
Based on the favorable features of the probe L in solution, the
test strips were prepared by immersing filter papers into the
solutions of probe L (c = 1 × 10 -3M) and then drying them in air
to determine the practicability of a ‘dip-stick’ method for the
detection of Zn2+.
4. Experimental section
4.1. Materials and methods
Fresh doubly distilled water was used throughout the
experiment. All other reagents and solvents were commercially
available at analytical grade and were used without further
When the test strips coated with the probe L were immersed
into the DMSO/H2O ~ HEPES buffer (80/20, v/v; pH = 7.23)
solutions of Zn2+, obvious fluorescent enhancement appeared
(Fig. 9, a and b). Similarly to detection of metal cations
selectively over other competing metal cations, we prepared the
test strips of the probe L with Cd2+ in the DMSO/H2O ~ HEPES
buffer (80/20, v/v; pH = 7.23) solution to compare with the test
strips of L with Zn2+ and Cd2+. The test result demonstrated the
preference of the L toward Zn2+ over the Cd2+ as shown in Fig.
9 (c and d). It was imperative to note that the chemical probe L
for Zn2+ did not have any interference from the Cd2+. Moreover,
fluorescence titration spectra of L (c = 2 × 10-5 M) in the
presence of different concentrations of Cd2+ ions was made (Fig.
S11). It can be clearly find that although the quantity of Cd2+
reached 20 equiv. to L, the intensities of solutions almost had no
change, and the highest intensity was only 20 (a.u.). Generally,
it was difficult to distinguish Zn2+ from Cd2+ in common solution
owing to the Cd2+ and Zn2+ had analogous possessions and
caused a strong interference33. Therefore, the chemosensor L
demonstrated a noteworthy propensity to discriminate Zn2+ from
Cd2+ in a given solution. The development of such a ‘dip-stick’
method was extremely attractive for ‘in-the-field’ measurements
that did not require any additional equipment. Therefore, the test
strips of L had excellent application value in the detection of
Zn2+.
1
purification. H NMR and 13C NMR spectra were recorded on a
1
Mercury-400BB spectrometer at 400 MHz for H. The chemical
shifts, reported in ppm downfield from tetra spectra, were
recorded with a Mercury-400BB spectrometer at 400 MHz
(TMS, d scale with the solvent resonances as internal standards).
Electrospray ionization mass spectra (ESI-MS) were measured
on an Agilent 1100 LC-MSD-Trap-VL system. UV-visible
spectra were recorded on a Shimadzu UV-2550 spectrometer.
The photoluminescence spectra were performed on a Shimadzu
RF-5301 fluorescence spectrophotometer. The melting points
were measured on an X-4 digital melting-point apparatus
(uncorrected). The infrared spectra were performed on a Digilab
FTS-3000 FT-IR spectrophotometer.
4.2. General procedure for spectroscopy
Fluorescence spectroscopy was carried out in a DMSO/H2O~
HEPES buffer (80/20, v/v; pH 7.23) solution on a Shimadzu RF-
5301 spectrometer. Any changes in the fluorescence spectra of
the synthesized compound were recorded upon the addition of
perchlorate salts while keeping the ligand concentration constant
(2.0 × 10-5 M) in all experiments. The perchlorate salts of the
ions (Fe3+, Hg2+, Ca2+, Cu2+, Co2+, Ni2+, Cd2+, Pb2+, Zn2+, Cr3+,
and Mg2+) were used for the fluorescence experiments.
1
For H NMR titrations, the solution of L and Zn2+ were
prepared in DMSO-d6. Aliquots of the solutions were mixed
directly in the NMR tubes.
Acknowledgments
This work was supported by the National Natural Science
Foundation of China (NSFC) (Nos. 21662031; 21661028;
21574104; 21262032) and the Program for Changjiang Scholars
and Innovative Research Team in University of Ministry of

5
Education of China (IRT 15R56).
ACCEPTED MANUSCRIPT
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Supporting Information
Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education of China; Key
Laboratory of Polymer Materials of Gansu Province; College of Chemistry and Chemical Engineering,
Northwest Normal University, Lanzhou, Gansu, 730070, P. R. China
1. Synthetic procedure of chemical probe L.
OH
OH
Hexamethylenetetramine
HCl
O
O
O
C
C
+
H CH
H
H
CH3COOH (50%)
HCl 1h
reflux
20oC
Cl
a
b
HO
OH
O
CH
H
C
N
NH2
CH
N
N
C
H
CH3CH2OH
CH3COOH
80oC
N N
C
CH
O
H
HO
HO
CH
HO
c
Scheme S1. Synthetic routes to L.
b A solution of salicylaldehyde (5.0 ml, 47.0 mmol), 37% aqueous solution of formaldehyde (3.6 ml, 50.0
mmol) and concentrated hydrochloric acid (50 mL) stirred in a dry and packaged round flask at the room
temperature until a large number of white solids separated out. Then the ether solution of these solid needed
to be washed by 10% NaOH solution to made the pH be 7~8 and then filtered out the water in this mixture.
After that, the ether solution was evaporated under reduced pressure and we gained white solid powder
which was then recrystallized by petroleum ether and the white needle crystal 5-chloromethyl
salicylaldehyde b was gained. m.p = 84-86ꢂ.1H NMR (600 MHz, d6-DMSO) δ 10.89 (s, 1H), 10.24 (s,
13
1H), 7.69 (d, J = 2.4 Hz, 1H), 7.57 – 7.52 (m, 1H), 6.99 (d, J = 8.5 Hz, 1H), 4.73 (s, 2H). C NMR (151
MHz, d6-DMSO), 191.22 , 161.17 , 137.34 , 129.60 , 122.59 , 118.18 , 46.15 .

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Fig. S1 1H NMR spectrum (600 MHz, d6-DMSO, 293 K) of b.
Fig. S2 13C NMR spectrum (151 MHz, d6-DMSO, 293 K) of b.
c A solution of acetic acid (22 ml, 50%) and hexamethylenetetramine (4.0 g) was reflexed at the progress
of heating until the solid in these mixture completely dissolved and then recovered to room temperature.
Added b (3.80g, 22mmol) and concentrated hydrochloric acid (50 mL) to the solution and refluxed it about
2 hours. Stop this reaction and put the reaction flask in refrigerator to gain pale yellow precipitate. These
1
precipitate needed to be washed by water and finally dried and we gained c (4.41g).m.p = 106-108 . H
NMR (600 MHz, d6-DMSO) δ 11.76 (s, 1H), 10.32 (s, 1H), 9.87 (s, 1H), 8.19 (d, J = 2.2 Hz, 1H), 8.00 (dd,
J = 8.6, 2.2 Hz, 1H), 7.15 (d, J = 8.6 Hz, 1H). 13C NMR (151 MHz, d6-DMSO) δ 191.49 , 190.48 , 165.87 ,

8
Tetrahedron
ACCEPTED MANUSCRIPT
136.11 , 132.43 , 128.81 , 122.99 .
Fig. S3 1H NMR spectrum (600 MHz, d6-DMSO, 293 K) of c.
Fig. S4 13C NMR spectrum (151 MHz, d6-DMSO, 293 K) of c.
L Added 4-hydroxyisophthalaldehyde (2.94g, 20 mmol), 2-(hydrazonomethyl)phenol (5.71g, 42mmol)
and several drops of acetic acid to ethanol as a reaction mixture. Stirred this mixture at 80 for 12 hours in
a dry flask. After the reaction was complete, the reaction solution was evaporated under reduced pressure
and extracted with ethyl acetate.The residue was purified by column chromatography on silica gel using
progressively more polar 50:1 to 30:1 petroleum ether/ethyl acetate as the mobile phase to give compound
L as a buff powder (3.09 g, m.p 270 ~ 273ꢂ ). 1H NMR (600 MHz, d6-DMSO) δ 11.52 (s, 1H), 11.34 (s,

9
ACCEPTED MANUSCRIPT
1H), 11.10 (s, 2H), 9.03 (d, J = 4.8 Hz, 1H), 8.93 (s, 1H), 8.76 (s, 1H), 8.29 (s, 1H), 7.95 (d, J = 7.7 Hz,
1H), 7.90 (d, J = 8.6 Hz, 1H), 7.73 (d, J = 2.6 Hz, 2H),7.67 (d, J = 3.2 Hz, 1H), 7.66 (s, 1H), 7.39 (d, J = 7.2
Hz, 2H), 7.10 (d, J = 8.4 Hz, 1H), 6.97 (s, 4H).13C NMR (151 MHz, d6-DMSO) δ 163.44 , 162.97 , 161.94 ,
161.36 , 159.09 , 133.58 , 133.27 , 131.68 , 131.27 , 120.04 , 119.56 , 118.69 , 116.87 . The [L - H+]- peak
appeared at 385.1021. which is coinciding well with that for the species [C22H17N4O3 - H]- (m/z =
385.1345).
Fig. S5 1H NMR spectrum (600 MHz, d6-DMSO, 293 K) of L.
Fig. S6 13C NMR spectrum (151 MHz, d6-DMSO, 293 K) of L.

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Tetrahedron
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Fig. S7 ESI-MS spectrum of compound L.
Fig. S8: IR spectra of L showing sharp peak at 1654 cm-1 for C=N bond and the broad peak at 3469 cm-1for
-OH.

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Fig. S9 Partial 1H NMR titration spectra (d6-DMSO, 298 K, 400 MHz) of L (15mM) upon addition of Zn2+.
Fig. S10 ESI-MS spectrum of compound L and Zn2+.

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Tetrahedron
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100
0
500
600
Wavelength(nm)
Fig. S11 fluorescence titration spectra of L (c = 2 × 10-5 M) in the presence of different concentrations of
Cd2+ ions in DMSO/H2O ~ HEPES buffer (80/20, v/v; pH = 7.23) solutions.
Equation
y = a + b*
Adj. R-Squar 0.85915
800
700
600
500
400
300
200
100
Value
Intercept 294.7036
Slope 12.92747
Standard Err
22.9049
B
B
1.30192
0
10
20
30
40
50
Equivalents
Fig. S12 Fluorescence intensity at 524 nm of L versus the number of equiv. of Zn2+ added.