A new pyrazoline-based fluorescent sensor for Al3+ in aqueous solution

Article abstract of DOI:10.1016/j.saa.2014.10.005

A new pyrazoline-based fluorescent sensor was synthesized and the structure was confirmed by single crystal X-ray diffraction. The sensor responds to Al³⁺ with high selectivity among a series of cations in aqueous methanol. This sensor forms a

Full text of DOI:10.1016/j.saa.2014.10.005

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1188–1194
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
3+
A new pyrazoline-based fluorescent sensor for Al in aqueous solution
Shengli Hu a, , Jingjing Song , Gongying Wu , Cuixia Cheng , Qing Gao
⇑
a
a
a
b,
⇑
a
Hubei Collaborative Innovation Center for Rare Metal Chemistry, Department of Chemistry and Chemical Engineering, Hubei Normal University, Huangshi 435002, PR China
Faculty of Materials Science & Engineering, Hubei University, Wuhan 430062, PR China
b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
Pyrazoline derivate 1 for selective detection of Al3+ with fluorescence quenching
ꢀ
ꢀ
The pyrazoline derived sensor is
simple to synthesize.
The structure of the pyrazoline was
confirmed by single crystal X-ray
diffraction.
O
ꢀ
ꢀ
This sensor can be used to determine
3
+
Al ion with high selectivity.
It is the first example of Al3 ion
fluorescent chemosensor based on
pyrazoline chromophore.
O
O
+
N
N
S
N
1
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 June 2014
Received in revised form 12 September 2014
Accepted 4 October 2014
Available online 12 October 2014
A new pyrazoline-based fluorescent sensor was synthesized and the structure was confirmed by single
3+
crystal X-ray diffraction. The sensor responds to Al with high selectivity among a series of cations in
3+
aqueous methanol. This sensor forms a 1:1 complex with Al and displays fluorescent quenching.
Ó 2014 Elsevier B.V. All rights reserved.
Keywords:
Pyrazoline
Fluorescent sensor
Aluminum ion
Selective
Introduction
fish in acidified waters [3] but also damages the central nervous
system to cause human illnesses like dementia and encephalopa-
Aluminum is the most abundant element in the Earth’s crust
and its compounds are widely used in the water treatment, in food
additives, in medicines and in the production of light alloy, etc. [1].
thy [4], Parkinson’s disease [5], and Alzheimer’s disease [6]. Thus,
3
+
the detection of Al has attracted increasing interest in the areas
of chemical and biological sciences. Compared with some conven-
tional methods, fluorescent sensors for various metal ions have
attracted significant focus because of the advantages such as high
sensitivity, selectivity, rapid response time and versatility [7].
3
+
The toxicity of Al not only hampers plant performance [2], killing
3
+
However, the poor coordination ability of Al compared to the
⇑
Corresponding authors. Tel./fax: +86 0714 6515602 (S. Hu). Tel./fax: +86 027
8661729 (Q. Gao).
3+
transition metal ions [8] makes the development of an Al fluores-
8
3+
cent sensor difficult. Only a few Al selective fluorescent sensors
E-mail addresses: hushengli168@126.com (S. Hu), gaoqing1969@126.com
have so far been reported [9–16]. Most of them were operated in
(
Q. Gao).
http://dx.doi.org/10.1016/j.saa.2014.10.005
386-1425/Ó 2014 Elsevier B.V. All rights reserved.
1

S. Hu et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1188–1194
1189
N
O
O
CHO
NHNH2
S
KOH
3
+
OH
reflux
HAc,
OH
2
O
O
O
OH
O
Br
O
N
N
S
N
N
S
N
KI, K CO , acetone
N
2
3
reflux
4
1
Scheme 1. Synthesis of pyrazoline derivate 1.
Fig. 1. The molecular structure of compound 1, with displacement ellipsoids drawn at the 30% probability level.
organic solvent, which limited their applications. Therefore, the
Experimental
development of new efficient Al3 fluorescent chemosensors, espe-
cially those that are simple to synthesise, and can work in aqueous
solution with high selectivity and sensitivity is still a challenge.
+
Reagents
1
,3,5-Triaryl-2-pyrazolines, with their rigid but only partly
All the reagents were purchased from commercial suppliers and
used without further purification. The salts used in stock solutions
of metal ions were CoCl ꢁ6H O, ZnCl , MnCl ꢁ4H O, KCl, NaCl,
unsaturated central pyrazoline ring, are well-known fluorescent
compounds widely used in fluorescent dyes emitting blue fluores-
cence with high fluorescence quantum yield [17–21] and electrolu-
minescence fields [22–28], However, the pyrazoline-based
fluorescent sensor for metal ions is still rare [29–32]. Recently,
we had reported two selective pyrazoline-based fluorescent
chemosensor for Cu [33] and Fe [34]. In continuing our research
to develop new fluorescent chemosensors based on pyrazoline
chromophore, we design a new pyrazoline derivative 1. The pri-
2
2
2
2
2
CuCl ꢁ2H O, NiCl ꢁ6H O, CdCl ꢁ2H O, HgCl , FeCl ꢁ6H O, MgCl
2
2
2
2
2
2
2
3
2
2-
ꢁ6H O, CrCl ꢁ6H O, Pb(NO ) , Al (SO ) ꢁ18H O.
2
3
2
3 2
2
4 3
2
Apparatus
2
+
3+
NMR spectra were measured on a Varian Mercury 300 spec-
1
13
trometer operating at 300 MHz for H and 75 MHz for C relative
to tetramethylsilane as internal standard. MS spectra were
obtained on a Finnigan Trace MS spectrometer. Elemental analyses
were performed with a Vario EL-III instrument (Germany). IR
mary test showed that 1 possesses a highly selective response of
fluorescence quenching toward Al3 in MeOH /H
+
2
O (95:5, v/v)
solution.

1
190
S. Hu et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1188–1194
Table 1
Crystal structure data and structure refinement for 1.
literature [33]. A mixture of pyrazoline (4) (0.37 g, 1 mmol), ethyl
bromoacetate (0.20 g, 1.2 mmol), KI (0.17 g, 1 mmol), CO
K
2
3
Empirical formula
Formula weight
Temperature
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a
C
26
H
23
3
N O
3
S
(0.33 g, 2.4 mmol), and acetone (25 ml) was stirred at reflux for
2 h. After cooling, the mixture was filtered and the filtrate was
evaporated to afford residue. The residue was crystallized from
457.53
298(2) K
0.71073
Monoclinic
C2/c
24.516(4)
9.1979(13)
20.561(3)
90°
101.315(2) °
90°
3669.9(6)
8
ethanol to afford 1 (0.27 g) as a white solid, Yield: 60%; Mp:
ꢂ1
1
43–144 °C;IR (KBr, cm ): 3423, 2920, 2359, 1752, 1597, 1540,
1
1444, 1320, 1280, 1210, 1124, 1083, 809, 754; H NMR (300 MHz,
CDCl ): d8.07–8.10 (m, 1H), 7.61–7.63 (m, 1H), 7.49–7.51 (m, 1H),
.20–7.37 (m, 8H), 7.06–7.10 (m, 2H), 6.77–6.80 (m, 1H), 5.78
dd, 1H, J = 4.5, 4.5 Hz, pyrazoline-H), 1.23 (t, 3H, CH3-H); 4.62
(s, 2H); 4.18–4.29 (m, 3H), 3.58 (dd, 1H, J = 4.5, 4.5 Hz, pyrazoline-
3
7
(
b
c
3
13
V (Å )
H), 1.23 (t, 3H, CH3AH);
C NMR (75 MHz, CDCl
63.5,155.9, 152.6, 141.5, 131.7, 131.3, 129.6, 128.8, 127.6, 126.0,
25.6, 122.0, 119.9, 112.3, 65.5, 63.8, 61.5, 47.0, 14.1; ESI-MS: m/
3
): 168.2,
Z
1
1
3
Density (calculated)
Index ranges
F(000)
1.337 Mg/m
ꢂ35 6 h 6 35, ꢂ12 6 k 6 13, ꢂ29 6 l 6 29
+
z: 458.7 [M + H] . Anal. calcd for C26
9.18; found: C 68.22, H 5.04, N 9.14.
23 3 3
H N O S: C 68.25, H 5.07, N
1616
Crystal size
0.15 ꢃ 0.12 ꢃ 0.10 mm
1.69–30.99°
24263
7184 [R(int) = 0.1222]
0.9826 and 0.9740
7184/0/300
h range for data collection
Reflections collected
Independent reflections
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
Absorption correction
Final R indices (I > 2
R indices (all data)
Largest diff. peak and hole
X-ray crystallography of compound 1
Suitable single crystals of 1 for X-ray structural analysis were
obtained by slow evaporation of a solution of 1 in CHCl ACH OH
20:1, v/v) mixture at room temperature. The diffraction data
was collected with a Bruker SMART CCD diffractometer using a
graphite monochromated MoK radiation (k = 0.71073 Å) at
96(2)K. The structures were solved by direct methods with SHEL-
0.842
None
3
3
(
r(I))
R1 = 0.0519, wR2 = 0.1026
R1 = 0.1228, wR2 = 0.1270
0.245 and ꢂ0.369 e Å
ꢂ3
a
2
2
XS-97 program and refinements on F were performed with SHEL-
XL-97 program by full-matrix least-squares techniques with
anisotropic thermal parameters for the non-hydrogen atoms. All
H atoms were initially located in a difference Fourier map. All H
atoms were placed in geometrically idealized positions and con-
strained to ride on their parent atoms, with CAH = 0.93 Å and
spectra were recorded on a Perkin-Elmer PE-983 infrared spec-
trometer as KBr pellets with absorption reported in cm . Absorp-
tion spectra were determined on UV-2501 PC spectrophotometer.
Fluorescence spectra measurements were performed on a Fluoro-
Max-P spectrofluorimeter equipped with a xenon discharge lamp,
ꢂ1
Uiso(H) = 1.2 Ueq(C).
1
cm quartz cells at room temperature (about 298 K).
Synthesis of ethyl 2-(2-(1-(benzo[d]thiazol-2-yl)-4-phenyl-4,5-
Binding titration
dihydro-1H-pyrazol-3-yl)phenoxy)acetate (1)
ꢂ5
The stock solutions of 1 (1.0 ꢃ 10 M) were prepared by
dissolving in MeOH/water(95:5, v/v) containing HEPES
buffer(10 mM, pH = 7.0). The cationic stocks were all in MeOH with
The synthetic route of the compound 1 is shown in Scheme 1.
Starting material pyrazoline (4) was synthesized according to
1
Fig. 2. A packing diagram for 1, viewed along the c-axis.

S. Hu et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1188–1194
1191
0
0
0
0
0
.4
.3
.2
.1
.0
250
4
73 nm
1
3
+
0
Fe
3+
2
1
+Al
200
150
+
3+
1+Cd
Al
3+
2+
Al
1+Co
3+
2+
1+Cr
2 eq
Cu
2
+
1
+Cu3
+
1
+Fe
2+
+
1
+Hg2
1
+Mg
1
00
50
0
2
+
1
+Mn+
1
+Na
2
+
1
+Pb2
+Ni
2
+
1
+
1+Zn
+
1+K
400
450
500
550
600
650
250
300
350
400
450
500
wavelength (nm)
Wavelength (nm)
Fig. 5. Fluorescence emission spectra of 1 (10 M) was titrated with Al3+ (0–2
ꢂ5
ꢂ5
Fig. 3. UV–vis spectral changes of compound 1 (1 ꢃ 10 M) in MeOH/water (95:5,
equiv) in MeOH/water (95:5, v/v) containing HEPES buffer (10 mM, pH = 7.0).
v/v) containing HEPES buffer (10 mM, pH = 7.0) upon additions of various metal
ꢂ5
ions (1 ꢃ 10 M).
8
6
0
0
0
0
0
0
0
0
.5
.4
.3
.2
.1
.0
5
0
0
Y = 0.48065 + 4.9549X
R= 1.00
2
eq
4
3+
Al
30
0
20
10
0
0
2
4
6
8
10
40
3
+
-5
1/[Al ](10 M)
2
0
0
.0
0.2
0.4
0.6
0.8
1.0
2
50
300
350
400
450
500
550
600
3+
X=[1]/([1]+[Al ])
Wavelength (nm)
Fig. 6. Job’s plot for determining the stoichiometry for 1 and Al3+ in MeOH/water
ꢂ5
Fig. 4. UV absorbance spectra of 1 (1.0 ꢃ 10 M) upon the addition of various
(
1
95:5, v/v) containing HEPES buffer (10 mM, pH = 7.0). Total concentration =
3+
amounts of Al . The inset shows the absorbance intensity at kmax = 342 nm as a
.0 ꢃ 10ꢂ5 M.
function of Al3 concentration.
+
The structure of compound 1 is crystallized in Monoclinic space
ꢂ3
a concentration of 3.0 ꢃ 10 M for UV–vis absorption and fluores-
group C2/c. Two benzene moieties and a benzothiazole moiety are
bonded to the pyrazoline ring at the atoms of C8, C10 and N2,
respectively. Consistent with a pronounced electronic interaction,
the bond lengths of C10AC17, N2AC7 are significantly shorter as
would be expected for a single bond. Moreover, the bond lengths
of N2AN3, N3AC10, C8AC9 agree well with the equivalent ones
in similar structures [35]. In the crystal of 1, the torsion angle
cence spectra analysis. For metal ion absorption and fluorescence
titration experiments, each time 3 mL solution of 1 filled in a
quartz cell of 1 cm optical path length, and we increased concen-
trations of metal ions by stepwise addition of different equivalents
using a micro-syringe. After each addition of Al3 ion, the solution
was stirred for 3 min. The volume of cationic stock solution added
L with the purpose of keeping the total volume
of testing solution without obvious change. For all measurements
of fluorescence spectra of 1, the excitation was at 360 nm.
+
o
was less than 100
l
C7AN2AC8AC11 of ꢂ63.44(10) shows C7 in the benzothiazole
moiety adopts an antiperiplanar conformation with respect to
the C11 atom of the benzene ring. In the asymmetry unit, the pyr-
azoline ring and benzothiazole is almost coplanar, while the pyraz-
oline ring is not coplanar with benzene ring(C11-C16) and benzene
ring(C17-C22), the dihedral angle between pyrazoline and them is
Results and discussion
6
.86(11)° and 87.08(12)°, respectively.
The packing diagram of the compound 1 is shown in Fig. 2. The
Synthesis and structural characteristics of 1
molecules are connected by weak
interaction. C4–Cg4 3.559(2) Å C9–Cg5 3.501(2) Å C25–Cg3
.571(2) Å and C25–Cg5 3.616(2) Å.
p–p interactions and CAH–p
The sensor 1 was obtained by the reaction of pyrazoline deriv-
ative (4) with ethyl bromoacetate in acetone under reflux with
3
2 3
K CO as base and KI as catalyst,. The yield of 1 was 60%. The struc-
1
tures of 1 were identified by using H NMR, IR and MS. The struc-
ture of 1 was further confirmed by X-ray diffraction analysis.
The molecular view of 1 is shown in Fig. 1. A summary of crys-
tallographic data collection parameters and refinement parameters
for 1 are compiled in Table 1.
Spectral characteristics
The absorption spectrum of compound 1 exhibits a broad band
ꢂ5
at 342 nm at room temperature in (1 ꢃ 10 tM) in MeOH/water

1
192
S. Hu et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1188–1194
2
2
1
1
50
00
50
00
0
0
0
0
0
.025
.020
.015
.010
.005
y = 0.0035+ 0.0020x
R = 0.99105
5
-1
K
= 1.75×10 M
ass
5
0
0
0
2
4
6
8
10
3
+
3+
3+
3+
3+
3+
3+
3+
3+
3+
3+
3+
3+
3+
1
3
+
-5
Al
1
/[Al ](10 )
2+ +Al 2+ +Al 3+ +Al2+ +Al 3+ +Al 2+ +Al2+ +Al 2+ +Al
Fe
Hg
Mn
Na
+
+Al
+
+Al 2+ +Al2+ +Al 2+ +Al
K
Ni Pb
Zn
Cd
Co
Cr Cu
Mg
Fig. 7. Benesi–Hildebrand linear analysis plots of 1 at different Al3+ concentration.
3+
Fig. 9. Competitive experiments in the 1 + Al system with interfering metal ions.
ꢂ5
3+
ꢂ5
n+
ꢂ5
[
1] = 1 ꢃ 10 M, [Al ] = 2 ꢃ 10 M, and [M ] = 2 ꢃ 10 M. Excited at 360 nm
and emission collected at 473 nm.
ꢂ5
Fig. 8. Fluorescence spectra of 1 (1 ꢃ 10 M) in MeOH/water (95:5, v/v) containing
HEPES buffer (10 mM, pH = 7.0) in the presence of different metal ions (2 equiv).
Inset: Photos of 1 in MeOH/water (95:5, v/v) containing HEPES buffer (10 mM,
3
+
pH = 7.0) without and with addition of Al under the irradiation of UV light at
65 nm.
3
(
95:5, v/v) containing HEPES buffer (10 mM, pH = 7.0). Binding
+
3+
2+
affinities of compound 1 toward metal ions (Na , Cr , Mg
,
2
+
2+
2+
2+
2+
2+
2+
+
2+
3+
3+
Hg , Cd , Zn , Co , Ni , Pb , Mn , K , Cu , Al and Fe ions)
were evaluated by UV–vis spectroscopy measurements. Upon
addition of these metal ions, the absorption spectrum changes in
+
3+
different manner as shown in Fig. 3. In the case of Na , Cr
,
2
+
2+
2+
2+
2+
2+
2+
2+
+
Mg , Hg , Cd , Zn , Co , Ni , Pb , Mn , K absorption curve
did not change, whereas in the case of Fe , Cu2+ and Al ions,
3+
3+
the addition of metal ions caused a increase of absorption intensity
at 342 nm. Moreover, upon addition of Fe3 and Cu to a solution
+
2+
of 1, two new absorption peaks appeared obviously at 292 nm and
Fig. 10. Partial infrared spectra (KBr) of free 1 and 1 with Al3+ at room temperature.
2
88 nm, respectively.
The UV–vis absorption spectra of 1 (1 ꢃ 10ꢂ5 M) in MeOH/
The fluorescence titration spectra of 1 in MeOH/water (95:5, v/
3
+
water (95:5, v/v) containing HEPES buffer (10 mM, pH = 7.0) in
v) containing HEPES buffer (10 mM, pH = 7.0) with Al shows an
emission maximum peak at 473 nm (Fig. 5). The fluorescence
the presence of various concentrations of Al3 ion (0–2 ꢃ 10 M)
are shown in Fig. 4, and the inset shows the plots of changes as a
function of increasing concentrations of Al3 . As shown in Fig. 4,
the UV absorbance of 1 at 342 nm enhanced from 0.187 to 0.49
+
ꢂ5
3
+
quantum yield of compound 1 in the absence of Al was calculated
to be 0.33 with respect to quinine sulphate in 0.1 N H SO solution
= 0.54) [36]. As Al ion was gradually titrated, the fluorescence
intensity of compound 1 gradually decreased and when the
+
2
4
3
+
(U
s
when increasing concentration of Al3 from 0 to 2 ꢃ 10 M, which
+
ꢂ5
3
+
ꢂ5
indicates the formation of a new complex between compound 1
amount of Al ion added was about 2 ꢃ 10 M, the fluorescence
3
+
and Al . A satisfactory linear relationship between UV–vis absor-
intensity almost reached minimum. The quantum yield of 1 was
3
+
3+
ꢂ5
bance and Al concentration was observed with the correlation
coefficient as high as 1.00.
calculated to be 0.029 in the presence of Al ion (2 ꢃ 10 M)
and almost reduced to 8.7% of the initial one.

S. Hu et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 136 (2015) 1188–1194
1193
O
O
O
O
O
O
Al3+
Al3+
N
N
S
N
N
S
N
N
complex
1
Strong Fluorescence
Weak Fluorescence
3+
Scheme 2. The proposed 1:1 bonding model of the 1ꢂAl complex.
To determine the stoichiometry of compound 1 and Al3+ ion in
shift of proton NMR signals corresponding to the AOCH
COA was
2
the complex, Job’s method [37] was employed by using the emis-
shifted by 0.0004 ppm. Other obvious change in the chemical shifts
3
+
sion changes at 473 nm as a function of molar fraction of Al . A
maximum emission was observed when the molar fraction of
of proton of ArAH and pyrazoline-H are also can be observed
3
+
owing to the binding of the Al
.
Al reached 0.5 (Fig. 6), indicating that Al3+ ions form a 1:1 com-
3+
Based on above IR spectroscopy, NMR spectroscopy studies, and
3
+
plex with the sensing compound.
Using the adjusted equation of Benesi–Hildebrand [38] Eq. (1),
a
we made the calculation of stability constant (K ).
Job’s plot, the proposed binding model of Al with 1 was shown in
Scheme 2. The chemosensor 1 is the most likely to chelate Al3+ via
its oxygen on the ether, oxygen on the carbonyl group, as well as
3
+
nitrogen on the thiazole and pyrazoline. The capture of Al
1
=ðF ꢂ F
0
Þ ¼ 1=ðF
1
ꢂ F
0
ÞKa½Gꢄ þ 1=ðF
1
ꢂ F
0
Þ
ð1Þ
3+
resulted in the electron or energy transfer from 1 to Al ; thus, 1
showed quenching of the fluorescence for Al and provided a high
3
+
Applying the Eq. (1), graph obtained was illustrated in Fig. 7. Where
3
+
3
+
selectivity for Al over the other tested metal ions.
0
F represents the fluorescence intensity in the absence of Al ion, F
3+
is the fluorescence intensity with the Al ion and [G] represents the
concentration of guest Al3 ion. The stability constant (K
+
) value
(error
Conclusion
a
ꢂ1
5
obtained from the Benesi–Hildebrand was 1.75 ꢃ 10 M
limits 6 10%). The detection limit, based on the definition by IUPAC
In summary, a new selective fluorescent sensor based on a pyr-
azoline derivate was synthesized and used for the determination of
ꢂ7
(C
DL = 3 Sb/m) [39], was found to be 2.27 ꢃ 10 M from 10 blank
3
+
solutions.
The selectivity and tolerance of compound 1 for Al ion over
Al ion with high selectivity in MeOH/water(95:5, v/v) containing
HEPES buffer(10 mM, pH = 7.0). This sensor formed a 1:1 complex
3+
other metal cations such as K , Na , Cr , Mg , Hg , Cd2+, Zn
+
+
3+
2+
2+
2+
,
with Al and showed a fluorescent quenching.
3+
2
+
2+
2+
3+
2+
2+
Co , Ni , Pb , Fe , Mn , and Cu ions were investigated by add-
ꢂ5
ing metal cations (2 ꢃ 10 M) to the solution of compound 1
Acknowledgments
ꢂ5
3+
(
1 ꢃ 10 M). As depicted in Fig. 8, Al produced significant
quenching in the fluorescent emission of 1, the other tested metals
only show relatively insignificant changes, this means that sensor 1
has a high selectivity to Al3 ion.
This study was supported by the National Natural Science Foun-
dation of China (20872042), the Science Technology Foundation for
Creative Research Group of HBDE (T201311), and the Hubei Prov-
ince Education Ministry Foundation of China (D20112507).
+
3+
To further gauge selectivity for Al ion over other metal ions,
competition experiments of Al3 ion mixed with other metal ions
were carried out from fluorescence spectra and the results are
+
ꢂ5
Appendix A. Supplementary material
shown in Fig. 9. The fluorescence intensity of 1 (1 ꢃ 10 M) in
the presence of 2 equiv of the Al3 ion was almost unaffected by
+
2+
3+
2+
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2014.10.005.
the addition of 2 equiv of competing metal ions (Cd , Cr , Cu
,
2
+
2+
2+
2+
2+
2+
+
3+
+
Hg , Mg , Mn , Zn , Co , Ni , K , Fe , and Na ). These results
3+
suggested that molecule 1 could be used as Al selective fluores-
cent chemosensor.
References
To gain a clearer understanding of the structure of 1-Al3+ com-
plexes, we used IR spectroscopy to obtain structural information
[
1] Y. Zhao, Z. Lin, H. Liao, C. Duan, Q. Meng, Inorg. Chem. Commun. 9 (2006) 966–
68.
9
3
+
about Al binding in 1. For the free compound 1, the carbonyl
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