Two new isomerous fluorescent chemosensors for Al3+ based on photoinduced electron transfer

Article abstract of DOI:10.1016/j.saa.2013.06.006

Two new isomerous PET fluorescent chemosensors (L and L') for Al ³⁺ have been designed, synthesized and characterized. The two chemosensors exhibited fluorescence enhancement upon binding Al³⁺ in CH₃-CN by PET inhibition processes from both the sulfur and the nitrogen donors to anthracene. The job's plot, Benesi-Hildebrand plot and ¹H NMR titration experiments indicate that both chemosensors form a 1: 1 complex with Al³⁺. The binding constants were calculated to be (1.432 ±0.186) × 10⁵ and (1.427 ± 0.970) × 10⁵, respectively. Furthermore, the lowest detection limit for Al³⁺ in CH₃CN was determined to be 4.8 × 10 ⁷ M and 2.2 × 10 ⁷ M, respectively.

Full text of DOI:10.1016/j.saa.2013.06.006

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 26–32
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Two new isomerous fluorescent chemosensors for Al3+ based
on photoinduced electron transfer
a
a,b
Xiu-Juan Jiang a, Hao Tang a, Xiao-Yuan Li a, Shuang-Quan Zang a, , Hong-Wei Hou , Thomas C.W. Mak
⇑
a College of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou 450001, PR China
b Department of Chemistry and Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong Special Administrative Region
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
ꢀ
Two new isomerous PET fluorescent
chemosensors (L and L0) has been
developed.
ꢀ
ꢀ
Both chemosensors exhibited ‘‘turn-
on’’ for Al3+ in CH3CN.
The selectivity of L0 for Al3+ was
improved compared to L.
a r t i c l e i n f o
a b s t r a c t
Two new isomerous PET fluorescent chemosensors (L and L0) for Al3+ have been designed, synthesized
and characterized. The two chemosensors exhibited fluorescence enhancement upon binding Al3+ in CH3-
CN by PET inhibition processes from both the sulfur and the nitrogen donors to anthracene. The job’s plot,
Benesi–Hildebrand plot and 1H NMR titration experiments indicate that both chemosensors form a 1:1
Article history:
Received 1 January 2013
Received in revised form 30 May 2013
Accepted 3 June 2013
Available online 15 June 2013
complex with Al3+
.
The binding constants were calculated to be (1.432 0.186) ꢁ 105 and
(1.427 0.970) ꢁ 105, respectively. Furthermore, the lowest detection limit for Al3+ in CH3CN was deter-
Keywords:
Isomerous
mined to be 4.8 ꢁ 10ꢂ7 M and 2.2 ꢁ 10ꢂ7 M, respectively.
Ó 2013 Elsevier B.V. All rights reserved.
Fluorescent chemosensors
Al3+
PET
Introduction
human body may damage the central nervous system to cause hu-
man illnesses like dementia, Parkinson’s disease, and Alzheimer’s
In recent years, fluorescent chemosensors for the detection of
various biologically and environmentally relevant ions have at-
tracted significant interest due to their potential applications in a
wide variety of fields [1]. But most of these chemosensors were
developed for the detection of transition and heavy metal ions such
as Zn2+, Cd2+, Cu2+, Hg2+ and Cr3+ [2]. It is well-known that alumi-
num is the most abundant metallic element in the earth’s crust and
widely used in industrial materials, food additives, water purifica-
tion, and cooking utensils [3]. However, excessive aluminum to
disease [4]. Thus, the development of chemosensors for the facile
detection of Al3+ in biologically and environmentally important
samples is still in high demand.
In the last decade, many methods such as atomic absorption
spectrometry, atomic emission spectrometry, inductively coupled
plasma atomic emission spectrometry and electrochemical meth-
ods have been used for aluminum detection [5]. But these methods
are relatively complex and need expensive instruments. Compara-
tively, fluorescent chemosensors are widely used because of their
advantages such as high sensitivity, selectivity, versatility, rapid re-
sponse time and relatively simple handling [1]. However, com-
pared to transition metal ions, the detection of Al3+ has been
⇑
Corresponding author. Tel./fax: +86 371 67780136.
E-mail address: zangsqzg@zzu.edu.cn (S.-Q. Zang).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.06.006

X.-J. Jiang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 26–32
27
greatly limited due to its weak coordination and strong hydration
ability [6]. So far, only a few of fluorescent chemosensors for Al3+
have been designed with moderate success [7]. Therefore, it is a
challenging work to develop some high selective and sensitive
chemosensors for Al3+ in environmental monitoring and biological
assays.
chloride (0.274 g, 1.55 mmol), intermediate compound 2 (0.600 g,
3.1 mmol), anhydrous sodium carbonate (0.494 g, 4.66 mmol)
and DMF (25 mL) were added into a 100 mL three-necked flask.
The reaction mixture was stirred at 120 °C under nitrogen atmo-
sphere for 4 h. After cooling to room temperature, the reaction
mixture was poured into distilled water (20 mL), and filtered off.
The residue was dissolved in dichloromethane (15 mL) and washed
with water (15 mL ꢁ 3). The organic phase was separated and
dried with anhydrous MgSO4. The organic solvent was removed
under reduced pressure. The crude product was purified by column
chromatography (SiO2, chloroform/methanol, 60:1, v/v). The prod-
uct was obtained as gray yellow solid in 81% yield (0.571 g). m.p.:
193197 °C. 1H NMR (300 MHz, CDCl3, ppm) d: 7.70 (m, 6H
J = 28.8 Hz), 3.22 (t, 4H, J = 13.2 Hz), 3.16 (t, 6H, J = 15.6 Hz), 3.01
(m, 4H, J = 22.2 Hz). 13C NMR (400 MHz, CDCl3, cmꢂ1): d 167.79,
137.40, 133.97, 133.60, 130.26, 127.40, 119.30, 47.49, 31.32,
23.89. IR (KBr plate, cmꢂ1): 3402, 2927, 1759, 1704, 1643, 1601,
1581, 1531, 1434, 1379, 1360, 1358, 1176, 1261, 1143, 1174,
1004, 863, 816, 800, 788, 778, 733, 702, 666, 620, 564, 500. Anal.
Calcd. for C22H21N3O4S2: C, 58.00, H, 4.65, N, 9.22, S, 14.08; found:
C, 58.21, H, 4.59, N, 9.28, S, 14.13. EI-MS: 456.1 [M + H]+.
Recently, Zeng and co-workers reported
a successful PET
chemosensor by using 1,2-dihydroxyanthraquinone as the fluoro-
phore and S2N podand moiety together with the hydroxyl of 1,2-
dihydroxyanthraquinone as binding sites [7m]. In this paper, we
have designed and synthesized two new isomerous PET chemosen-
sors L and L0 for the detection of Al3+ using anthracene as the fluo-
rophore and only S2N podand moiety as the chelating unit. Studies
show that the two chemosensors L and L0 had selectivity for Al3+
.
Experimental
Materials, instruments and methods
Materials
All the materials for the synthesis were purchased from com-
mercial suppliers and used without further purification. All of the
solvents used were of analytical reagent grade. Fresh anhydrous
CH3CN was distilled. Double distilled water was used for spectral
detection.
Synthesis of the intermediate compound 30
This compound was prepared from N,N-bis(2-chloro-
ethyl)amine hydrogench-loride and intermediate compound 20
through the similar procedure to 3. The product was obtained as
light yellow solid in 78% yield (0.550 g). m.p.: 120123 °C. 1H
NMR (300 MHz, CDCl3, ppm) d: 7.70 (d, 4H J = 7.8 Hz), 7.56 (t, 2H,
J = 9.6 Hz), 3.21 (t, 10H, J = 12.6 Hz), 2.98 (t, 4H, J = 12.6 Hz). 13C
NMR (400 MHz, CDCl3, cmꢂ1): d 168.07, 145.69, 133.10, 131.77,
128.60, 123.37, 120.84, 47.40, 32.89, 23.99. IR (KBr plate, cmꢂ1):
3301, 2920, 2803, 2751, 1767, 1697, 1603, 1487, 1436, 1380,
1335, 1322, 1291, 1254, 1193, 1178, 1161, 1125, 1050, 1007,
975, 886, 829, 736, 669, 614, 600, 510. Anal. Calcd. for C22H21N3O4-
S2: C, 58.00, H, 4.65, N, 9.22, S, 14.08; found: C, 58.14, H, 4.62, N,
9.54, S, 14.15. EI-MS: 456.1 [M + H]+.
Instruments
1H NMR and 1H NMR titrations experiments were obtained on a
Bruker 300 spectrometer with TMS as internal standard at room
temperature. 13C NMR were carried out on a Bruker 400 spectrom-
eter. Mass spectra were recorded on a LC-MSD-Trap-XCT instru-
ment by electrospray ionization (ESI). UV–vis absorption spectra
were recorded on a TU-1900 double-beam UV–vis spectrophotom-
eter. Fluorescence emission spectra were recorded on a FluoroMax-
4 spectrofluorometer with 5 nm slit for both excitation and emis-
sion. The Fourier transform infrared (FT-IR) spectra were obtained
in the range of 400–4000 cmꢂ1 as KBr pellets on a Bruker VECTOR
22 spectrometer. Microanalysis (C, H, N, S) was performed on a
Perkin–Elmer 240 elemental analyzer. Melting points were deter-
mined on an X-4 microscope electron thermal apparatus.
Synthesis of L
9-Bromomethylanthracene (A) (0.108 g, 0.4 mmol), intermedi-
ate compound 3 (0.182 g, 0.4 mmol), anhydrous K2CO3 (0.116 g,
0.8 mmol) were added in CH3CN (8 mL). The reaction mixture
was allowed to reflux for 12 h. After cooling to room temperature,
K2CO3 was removed by filtration. The yellow filtrate was evapo-
rated to dryness under reduced pressure. The resulting solid was
purified by column chromatography (petroleum ether/ethyl ace-
tate, 7:3, v/v). The product was obtained as light yellow solid in
85.8% yield (136 mg). m.p.: 203–206 °C. 1H NMR (300 MHz, CDCl3,
ppm) d: 8.51 (d, 2H, J = 9.0 Hz), 8.363 (s, 1H), 7.97 (d, 2H,
J = 7.8 Hz), 7.49 (m, 6H, J = 43.2 Hz), 7.15 (t, 2H, J = 9.6 Hz), 6.88
(d, 2H, J = 8.4 Hz), 4.70 (s, 2H), 3.11 (d, 6H, J = 5.1 Hz), 3.05 (m,
4H, J = 24.3 Hz), 2.99 (t, 4H, J = 7.2 Hz). 13C NMR (400 MHz, CDCl3,
cmꢂ1): d 167.94, 167.76, 137.67, 133.53, 133.33, 131.26, 131.22,
129.49, 129.03, 128.64, 128.04, 126.87, 126.15, 125.03, 124.79,
118.77, 52.60, 51.17, 29.30, 23.81. IR (KBr plate, cmꢂ1): 3451,
3049, 2933, 2864, 2808, 1765, 1706, 1599, 1580, 1457, 1439,
1380, 1340, 1261, 1179, 1114, 1098, 1055, 1007, 887, 864, 800,
733, 669, 634, 555, 526, 501. Anal. Calcd. for C37H31N3O4S2: C,
68.81, H, 4.84, N, 6.51, S, 9.93; found: C, 68.79, H, 4.81, N, 6.48, S,
9.96. EI-MS: 646.2 [M + H]+.
Methods
Stock solutions of metal ions were prepared from their chloride
or nitrate salts in distilled water. High concentration of the stock
solutions of L and L0 (200
l
M) were prepared in freshly distilled
CH3CN, respectively. When studying the fluorescence sensing
behaviors of L or L0 to metal ions, 75 L stock solution of L or L0
was put into a 3 mL quartz cuvette, then 60 L one of the stock
l
l
solutions of the metal salts was added to the above solution and
mixed. Fluorescence quantum yields of complexes Al-L and Al-L0
were determined by comparison of the integrated area of the emis-
sion spectrum in CH3CN. The optically matching solution of anthra-
cene (ethanol, U = 0.27) was used as standard, the concentration of
the reference was adjusted to match the absorbance of the test
sample at the wavelength of excitation [8].
Syntheses
Synthesis of compounds A, 1(10) and 2(20)
Compounds A [9], 1(10) [10] and 2(20) [10] were synthesized
according to the literature procedure.
Synthesis of L0
This compound was prepared from 9-bromomethylanthracene
(A), intermediate compound 30 through similar procedure to L.
The product was obtained as yellow solid in 80.2% yield
(0.118 g). m.p.: 7375 °C. 1H NMR (300 MHz, CDCl3, ppm) d: 8.43
(d, 2H, J = 9.0 Hz), 8.33 (s, 1H), 7.95 (d, 2H, J = 7.8 Hz), 7.47 (m,
Synthesis of the intermediate compound 3
Compound 3 was synthesized by an improved method accord-
ing to the literature [11]. N,N-bis(2-chloroethyl)amine hydrogen-

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X.-J. Jiang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 26–32
8H, J = 43.2 Hz), 7.07 (m, 2H, J = 9.6 Hz), 4.63 (s, 2H), 3.17 (s, 6H),
3.08 (d, 4H, J = 6.9 Hz), 2.98 (d, 4H, J = 6.9 Hz). 13C NMR
UV–vis and fluorescence spectral changes of L induced by Al3+
(400 MHz, CDCl3, cmꢂ1):
d
168.01, 167.94, 145.48, 132.65,
The UV–vis spectra of the chemosensor L in CH3CN exhibited
three obvious absorption peaks at 255, 367 and 387 nm. To inves-
tigate the binding property of L toward Al3+, titration experiments
were carried out as shown in Fig. 1A. Upon addition of Al3+, the
absorption peaks at 367 and 387 nm gradually decreased and the
absorption peak at 233 nm gradually increased while the absorp-
tion peak at 255 nm remained constant along with the increase
of the Al3+ concentration. Meanwhile, a high energy (LE) shoulder
developed at 280 nm. Moreover, three clear isobestic points at
269, 358 and 392 nm were observed. Furthermore, the changes
of this absorption peaks were likely due to the coordination of L
with Al3+ [12]. According to the linear Benesi–Hildebrand expres-
sion [13], the linear relationship assumed a 1:1 binding model with
the Ka of (1.432 0.186) ꢁ 105 from the titration experiments
(Supplementary Fig. 11).
131.20, 131.25, 128.99, 128.39, 128.18, 128.03, 126.02, 124.96,
124.64, 123.04, 120.85, 52.34, 50.97, 30.92, 23.94. IR (KBr plate,
cmꢂ1): 3459, 3050, 2941, 1771, 1704, 1610, 1523, 1436, 1378,
1294, 1252, 1436, 1378, 1294, 1177, 1108, 1051, 1007, 978, 886,
840, 736, 670, 611, 590, 511. Anal. Calcd. for C37H31N3O4S2: C,
68.81, H, 4.84, N, 6.51, S, 9.93; found: C, 68.85, H, 4.80, N, 6.53, S,
9.89. EI-MS: 646.2 [M + H]+.
Result and discussion
Our research involves the design, synthesis, and evaluation of
the two isomerous fluorescent chemosensors L and L0. The detailed
experimental procedures were shown in Scheme 1 and all new
compounds were characterized by NMR, IR, ESI/MS and elemental
analysis. The single crystals of L and L0 were obtained by solvent
evaporation method in dichloromethane and acetone, respectively
(Scheme 1, Supplementary Figs. 9 and 10).
The chemosensor L exhibited a weak fluorescence at 413 nm in
CH3CN (U = 0.006) as shown in Fig. 1B, which could be attributed to
the two PET processes from the nitrogen donor and the sulfur do-
nors to the anthracene fluorophore. Upon binding Al3+, a significant
Scheme 1. (a and b) Synthesis of L and L0 and (c) X-ray single crystal structures for L and L0.

X.-J. Jiang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 26–32
29
Fig. 1. (A) UV–vis spectra and (B) fluorescence spectra of L (5 l
M) in CH3CN upon the addition of Al3+. Inset: (A) the photos of the solution of L before and after addition of 10
equiv of Al3+ under visible light. (B) (a) the plot of the fluorescence intensity (413 nm) vs the concentration of Al3+; (b) the photos of the solution of L before and after addition
of 10 equiv Al3+ under 365 nm UV light.
increase of fluorescence intensity at 413 nm was observed by the
inhibition of PET processes ( = 0.013). The inset in Fig. 1a showed
The fluorescence spectral changes of L0 (5 M) induced by Al3+
l
U
were conducted in CH3CN as shown in Fig. 2B. Upon addition of dif-
ferent concentrations of Al3+, a significant enhancement of the
fluorescence intensity at 395, 416 and 443 nm was observed by
the inhibition of PET processes. The quantum yield of the complex
in CH3CN was calculated to be 0.021, which was higher than that of
the dependence of the fluorescence intensity at 413 nm on the Al3+
concentration, which suggested the chemosensor L exhibited an
efficient fluorescence response. The 1:1 stoichiometry between L
and Al3+ was also obtained from Job’s plot (Supplementary
Fig. 12). The corresponding detection limit was found to be
4.8 ꢁ 10ꢂ7 M by plotting the fluorescence intensity at 413 nm
versus the concentration of Al3+ (Supplementary Fig. 13) [14].
the free ligand (
U = 0.009). The inset in Fig. 2a also suggested that
the chemosensor L0 (416 nm) exhibited an efficient fluorescence
response toward Al3+. To further confirm the stoichiometry be-
tween Al3+ and L0, a Job’s plot obtained from emission data also
showed a 1:1 complex (Supplementary Fig. 15). The detection limit
of the chemosensor L0 for Al3+ was about 2.2 ꢁ 10ꢂ7 M (Supple-
mentary Fig. 16) [14].
UV–vis and fluorescence spectral changes of L0 induced by Al3+
The UV–vis spectra of the chemosensor L0 exhibited a typical
anthracene absorption peak at 255 nm in CH3CN as shown in
Fig. 2A. Upon addition of Al3+, the absorption band at 205 nm grad-
ually increased while the absorption peak at 255 nm remained
constant. These changes were likely attributed to the coordination
of L0 with Al3+ [12]. According to the linear Benesi–Hildebrand
expression [13], the linear relationship suggested a 1:1 binding
model with the Ka of (1.427 0.970) ꢁ 105 from the titration
experiments (Supplementary Fig. 14).
1H NMR titration experiments
To further investigate the binding model between L and L0 with
Al3+ 1H NMR titration experiments were carried out in CDCl3/CD3-
,
OH (17:3, v/v). As shown in Fig. 3A, upon adding 1 equiv of Al3+ to L
solution, the peaks of the protons Ha, Hb, Hc, Hd and He around
binding sites were obviously shifted downfield by 0.75, 0.48,
0.30, 0.20, 0.14 ppm from d 4.71, 2.66, 3.10, 6.91, 7.17 to 5.46,
Fig. 2. (A) UV–vis spectra and (B) fluorescence spectra of L0 (5 M) in CH3CN upon the addition of Al3+. Inset: (A) the photos of the solution of L0 before and after addition of 10
l
equiv of Al3+ under visible light. (B) (a) the plot of the fluorescence intensity (416 nm) vs the concentration of Al3+; (b) the photos of the solution of L0 before and after addition
of 10 equiv of Al3+ under 365 nm UV light.

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X.-J. Jiang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 26–32
1
Fig. 3. H NMR spectra of L (A) and L0 (B) with and without Al(NO3)3 in CDCl3:CD3OD = 17:3 (v/v).
3.14, 3.40, 7.11, 7.31 ppm, respectively. Upon adding 1 equiv of
Al3+ to L0 solution (Fig. 3B), the peaks of the protons Ha, Hb, Hc,
Hd and He around binding sites were also obviously shifted down-
field by 0.53, 0.20, 0.13, 0.08, 0.03 ppm from d 4.63, 2.98, 3.14, 7.09,
7.38 to 5.16, 3.18, 3.27, 7.17, 7.41 ppm, respectively. When adding
more than 1 equiv of Al3+, the chemical shift of the protons of L and
L0 stopped changing, which confirmed again that L and L0 toward
Al3+ ions formed a 1:1 complex, respectively.
Cr3+, Cu2+, Hg2+ had no obvious effect on the fluorescence emission
of L except that Pb2+, Ag+ and Fe3+ showed little enhancement.
Compared to L, Cu2+, Cr3+, Fe3+ and Fe2+ had a slight increase in
the fluorescence intensity positioned at 443 nm of L0. In stark con-
trast, the addition of Al3+ caused
a significant fluorescence
enhancement of L and L0. Moreover, L0 had better selectivity for
Al3+ than L due to a more efficient PET mechanism. These results
suggested that both L and L0 had good selectivity for Al3+ over other
metal ions with little interference in CH3CN.
To further evaluate the selectivity of L and L0 as the fluorescent
Selection and competition experiments
chemosensor for Al3+ in practice, competition experiments were
carried out by adding 10 equiv of Na+, K+, Ca2+, Mg2+, Cd2+, Zn2+
,
To evaluate the selectivity of the chemosensors L and L0 toward
Al3+ ions in CH3CN, fluorescence spectra changes were recorded
after 3 min when 10 equiv of each of these metal ions such as
Fe2+, Fe3+, Mn2+, Co2+, Ni2+, Cu2+, Hg2+, Pb2+, Ag+ in the presence
of 10 equiv of Al3+ under the above conditions. As shown in
Fig. 5, competitive metal ions had no obvious interference with
the detection of Al3+ ions. In addition, the fluorescence behaviour
of the two chemosensors L and L0 in different ratios of CH3CN/
Na+, K+, Ca2+, Mg2+, Al3+, Cd2+, Zn2+, Fe2+, Fe3+, Mn2+, Co2+, Ni2+
,
In3+, Cr3+, Cu2+, Hg2+, Pb2+, and Ag+ were added. As can be seen from
Fig. 4, Na+, K+, Ca2+, Mg2+, Cd2+, Zn2+, Fe2+, Mn2+, Co2+, Ni2+, In3+
,
Fig. 4. Fluorescence spectra of L (A) and L0 (B) (5
lM) upon addition of 10 equiv of various metal ions in CH3CN (kex = 367 nm).

X.-J. Jiang et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 115 (2013) 26–32
31
Fig. 5. Metal-ion response for L (A) and L0 (B) (5
lM) in the absence (F0) and presence (F) of 10 equiv of various metal ions in CH3CN. Bars represent the fluorescence intensity
changes (F–F0). The gray bars represent the changes of the fluorescence intensity after the addition of various metal ions, the black bars represent the changes of the
fluorescence intensity that occurs upon the subsequent addition of 10 equiv of Al3+ to the above solution.
H2O solution was investigated under the same measurement con-
ditions (Supplementary Fig. 17). Moreover, the selectivity of L and
L0 toward Al3+ was also studied in CH3CN/H2O (9/1) solution (Sup-
plementary Fig. 18). These data indicated that the chemosensors L
and L0 displayed excellent selectivity toward Al3+ in CH3CN and
CH3CN/H2O (9/1) solution.
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In addition to cation binding properties, the selectivity of
the chemosensors L ꢂ and L0 toward various anions
(Fꢂ; Clꢂ; Brꢂ; Iꢂ; AcOꢂ; ClO ; H2POꢂ and HSOꢂ4 ) was also conducted
4
4
in the presence of 10 equiv of Al3+ in CH3CN under the above condi-
tions (Supplementary Fig. 19). Among the various anions, only Fꢂ
and ClOꢂ4 had little effect on the fluorescence emission of Al-L. But
in Al-L0 solution, these anions remained practically unchanged. Be-
sides, the selectivity of the chemosensors L and L0 toward various an-
ions was also studied in CH3CN/H2O (9/1) solution (Supplementary
Fig. 20). All the results suggested that L and L0 could be used as selec-
tive fluorescent chemosensors for Al3+ with little interference of the
environmentally relevant anions.
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Conclusions
In conclusion, we have successfully developed two new isomer-
ous turn-on fluorescent chemosensors for Al3+ based on PET pro-
cesses. Moreover, the two chemosensors (L and L0) exhibited
good selectivity for Al3+ over other metal ions with little interfer-
ence. More importantly, the fluorescence intensity of L0 was im-
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Appendix A. Supplementary material
Characterization data including 1H and 13C NMR, MS, UVꢂvis,
fluorescence spectra and X-ray crystallographic data in CIF format
of L (CCDC 907002) and L0 (CCDC 902859). Supplementary data
associated with this article can be found, in the online version, at
http://dx.doi.org/10.1016/j.saa.2013.06.006.

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