An effective mutli-wavelength emissive aluminum ion fluorescence chemosensor based on 3-[1'-(2'-hydroxy-α-methylbenzylidene-imino)]-2-(p-N, N-dimethylaminophenyl)-1,2-dihydroquinazolin-4-(3H)-one

Article abstract of DOI:10.1016/j.ica.2012.10.009

In the paper, a novel mutli-wavelength emissive aluminium ion chemosensor based on 3-[1'-(2'- hydroxy-α-methylbenzylidene-imino)]-2-(p-N,N-dimethyl aminophenyl)-1,2-dihydroquinazolin-4- (3H)-one is designed and synthesized. According to the fluorescence behavior toward several metal ions, it shows high selectivity to Al³⁺ over other commonly coexistent metal ions (N ^a+, Mg²⁺, Co²⁺, Ni²⁺, Cu ²⁺, Fe³⁺, Cr³⁺, Hg²⁺, Zn ²⁺, Cd²⁺) in aqueous environment (pH 7.40). Meanwhile the binding constant between Al³⁺ and chemosensor achieves 3.92 × 106 M^-1 in aqueous media. Moreover, according to the Job plot, 1:1 stoichiometry between Al³⁺ and the sensor was deduced in aqueous media (pH 7.4). The good selectivity and sensitivity in aqueous media effectively enhance the application value of the chemosensor for Al ³⁺.

Full text of DOI:10.1016/j.ica.2012.10.009

Inorganica Chimica Acta 395 (2013) 77–80
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Note
An effective mutli-wavelength emissive aluminum ion fluorescence
chemosensor based on 3-[10-(20-hydroxy-
-methylbenzylidene-imino)]-2-(p-N,
N-dimethylaminophenyl)-1,2-dihydroquinazolin-4-(3H)-one
a
Zengchen Liu a, , Zhengyin Yang b, Yanxia Li a, Tianrong Li b, Baodui Wang b, Yong Li b, Xiulong Jin b
⇑
a Department of Chemistry, Zhoukou Normal University, Zhoukou 466001, PR China
b State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, PR China
a r t i c l e i n f o
a b s t r a c t
In the paper, a novel mutli-wavelength emissive aluminium ion chemosensor based on 3-[10-(20-
Article history:
Received 28 July 2012
Received in revised form 23 September 2012
Accepted 20 October 2012
Available online 2 November 2012
hydroxy-
a-methylbenzylidene-imino)]-2-(p-N,N-dimethyl aminophenyl)-1,2-dihydroquinazolin-4-
(3H)-one is designed and synthesized. According to the fluorescence behavior toward several metal ions,
it shows high selectivity to Al3+ over other commonly coexistent metal ions (Na+, Mg2+, Co2+, Ni2+, Cu2+
,
Fe3+, Cr3+, Hg2+, Zn2+, Cd2+) in aqueous environment (pH 7.40). Meanwhile the binding constant between
Al3+ and chemosensor achieves 3.92 ꢀ 106 Mꢁ1 in aqueous media. Moreover, according to the Job plot, 1:1
stoichiometry between Al3+ and the sensor was deduced in aqueous media (pH 7.4). The good selectivity
Keywords:
Chemosensor
and sensitivity in aqueous media effectively enhance the application value of the chemosensor for Al3+
.
Al3+ selectivity
Heterocyclic compound
Binding constant
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
When aiming at the rational development of specific fluores-
cence chemosensors for targeting Al3+, the choice of binding motif
is a critical factor. Because in the cellar level, many transition metal
ions such as Hg2+ and Cd2+ can interfere with Al3+ binding. It is well
known that the chelating groups such as C@N, C–O and C@O exhi-
bit high affinity to such metal cations, but less binding affinity to-
ward alkali and alkaline earth metal cations [19,20]. Thus, in the
present investigation, novel heterocycle compound 3-[10-(20-hy-
The highly selective and sensitive chemosensors of metal ions
in aqueous environment are of great importance for studying and
tracking the chemical and physiological functions in the wide
range of chemical and biological processes [1–5]. Recently, consid-
erable efforts have been devoted to developing fluorescence
chemosensors based on nitrogen atom heterocyclic derivates due
to their simplicity, high selectivity and sensitivity toward corre-
sponding metal ions [6–10]. Aluminium is not a biologically essen-
tial element and exhibits considerable cytoxicity in living
organism. Recent study advances have some light on the biological
roles of aluminium, particularly on its functions related to neurobi-
ology. Moreover, in the physiological processes such as brain, pros-
tate and intestine locations, abnormal level of Al3+ even can cause
some relevant diseases like Parkinson’s disease. Additionally, high
Al3+ content in drinking water is very bad for human health [11–
16]. The incomplete understanding of the biological effects of
Al3+ remains active topics of research. Thus, there is a considerable
need to design highly selective chemosensors, which are capable of
detecting the presence of Al3+ in environmental and biological sys-
tem in aqueous media at a physiological pH value. To date, some
Al3+ selective chemosensors have been achieved [17,18]. However,
to the best of our knowledge very few fluorescent sensors for Al3+
in aqueous media have been designed.
droxy-
a
-methylbenzylidene-imino)]-2-(p-N,N-dimethylamin-
architecture is
ophenyl)-1,2-dihydroquinazolin-4-(3H)-one
designed to increase the selectivity and sensitivity for detecting
Al3+. According to the spectra analysis, the fluorescence sensor
exhibits high selectivity toward Al3+ over other metal ions in aque-
ous buffer media (pH 7.4).
2. Experimental
2.1. Characterization and materials
1H NMR and 13C NMR spectra were recorded on a Varian 400-
MHz spectrometer with TMS as an internal standard. The melting
point of the compounds were determined on a Beijing XT4-100X
microscopic melting point apparatus. ESI-MS was recorded on
the Esquire 6000 instrument. The UV–Vis spectra were recorded
on a Perkin-Elmer Lambda-35 UV–Vis spectrophotometer. Fluores-
cence spectra were obtained on a Shimadzu RF-5301 spectropho-
tometer at room temperature. Elemental analysis was tested on a
Elementar Vario EL Elemental Analyzers instrument.
⇑
Corresponding author. Tel.: +86 0394 8178252; fax: +86 0394 8178252.
E-mail address: liuzch07@lzu.edu.cn (Z. Liu).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.10.009

78
Z. Liu et al. / Inorganica Chimica Acta 395 (2013) 77–80
Stock solutions (1.0 ꢀ 10ꢁ3 M) of metal ions (metal nitrate)
6.84 (2H, m, –C21,22–H), d 6.74–6.77 (1H, m, –C8–H), d 6.66–6.68
(1H, d, –C8–H), d 6.14 (1H, s, –C2–H), d 2.85 (6H, s, –C26,27–H). d
2.27 (3H, s, –C18–H). 13C NMR (DMSO–d6 400 MHz): d 17.04. d
75.14. d 111.72. d 113.30. d 114.49. d 117.11. d 117.47. d 118.39.
d 118.62. d 126.07. d 127.99. d 128.25. d 129.60. d 132.42. d
133.88. d 147.49. d 150.66. d 159.25. d 160.52. d 173.24. ESI-MS
Calc. for C24H24N4O2 ([L]+H+): 401.19; Found for 401.3. The ele-
mental analysis data Anal. Calc. for C, 71.98; H, 6.04; N, 13.99.
Found: C, 71.55; H, 5.96; N, 14.06%.
were prepared using in two-distilled water. The stock solution of
L (5.0 ꢀ 10ꢁ3 M) was prepared in CH3CN–HEPES (9:1). In titration
experiments, each time a 20
l
L solution of L (5.0 ꢀ 10ꢁ3 M) was
filled in a quartz optical cell of 1 cm optical path length. Then equal
amount of Al3+ stock solution (10
lL) was added to the compound
solution with micro-pippet. Spectral data was recorded at 1 min
after the addition. In selectivity experiment, the test samples were
prepared by placing appropriate amounts of metal ion stock into
2 mL aqueous solution of L (5.0 ꢀ 10ꢁ5 M). For fluorescence mea-
surements, excitation wavelength is at 345 nm.
Compound 1 was prepared by the reported methods [21]. The
synthesis routine of 3-[1’-(2’-hydroxy-a-methylbenzylidene-imi-
3. Results and discussion
3.1. The fluorescence emission spectroscopy of L to Al3+
no)]-2-(p-N,N-dimethylaminophenyl)-1,2-dihydroquinazolin-4-
(3H)-one (L) were shown in Scheme 1. All the chemicals were of re-
agent grade and were used without further purification. All spec-
troscopic measurements were performed in CH3CN-HEPES (9:1)
buffer solution (pH 7.4).
To investigate the fluorescence selectivity toward special metal
ions, the fluorescence selectivity experiments of various metal
(Al3+, Na+, Mg2+, Co2+, Ni2+, Cu2+, Fe3+, Cr3+, Hg2+, Zn2+, Cd2+) were
carried out in CH3CN–HEPES (9:1) buffer solution at pH 7.4. As
Shown in Fig. 1a, in the absence of metal ions, the ligand exhibited
a single fluorescence signal peak in the range from 400 to 500 nm
in CH3CN-HEPES media (pH 7.4). However, with addition of equiv-
alent various metal ions, only the addition of Al3+ lead to interest-
ing multi-wavelength emssive fluorescence enhancement. Clearly,
the addition of Al3+ lead to the formation of Al3+–L with enhanced
2.2. Synthesis of 3-[10-(20-hydroxy-
a-methylbenzylidene-imino)]-2-
(p-N,N-dimethylaminophenyl)-1,2-dihydroquinazolin-4-(3H)-one (L)
An ethanol solution (20 mL) of compound 1 (1 mmol, 0.269 g)
was added to another ethanol (20 mL) containing 4-dimethyl-
amino benzaldehyde (1 mmol, 0.149 g), Then the solution was re-
flux for 1 h under stirring and some white precipitant appeared.
The mixture was filtered and dried under vacuum. Recrystalliza-
fluorescence intensity, which indicated 3-[10-(20-hydroxy-
a-meth-
ylbenzylidene-imino)]-2-(p-N,N-dimethylaminophenyl)-1,2-dihy-
droquinazolin-4-(3H)-one could act as an highly selective
fluorescence probe for Al3+ under physiological pH conditions. In
addition, according to the histogram (Fig. 1b), the high selectivity
of L for Al3+ over other metal ions were indicated obviously.
Fluorescence titration experiment (Fig. 2a) using L and Al3+ was
performed in aqueous buffer media (pH 7.4) at room temperature.
Upon addition of Al3+, A new fluorescence signal at 500 nm signif-
icantly appeared. It was explicit that the binding between L and
Al3+ induced the tranger of electron from L, which was responsible
tion from DMF H2O (V:V = 1:1) gave 3-[10-(20-hydroxy-
a-methylb-
enzylidene-imino)]-2-(p-N,N-dimethylaminophenyl)-1,2-dihydro-
quinazolin-4-(3H)-one (L), which was dried under vacuum. Yield,
75%. m.p: 283–285 °C. 1H NMR (Fig. S1), 13C NMR (Fig. S2) and
ESI-MS (Fig. S3) were listed in Supplementary materials. 1H NMR
(DMSO-d6 400 MHz): d 12.26 (1H, s, –C25–H), d 7.73–7.75 (1H, d,
–C6–H), d 7.59–7.61 (1H, d, –C9–H), d 7.43 (1H, s, –N1–H), d 7.29–
7.43 (4H, m, –C12,13,15,16–H), d 6.85–6.89 (2H, m, –C7–H), d 6.80–
Scheme 1. The sysnthesis line of fluoresence sensor L (3-[10-(20-hydroxy-
a-methylbenzylidene-imino)]-2-(p-N,N-dimethylaminophenyl)-1,2-dihydroquinazolin-4-(3H)-
one).

Z. Liu et al. / Inorganica Chimica Acta 395 (2013) 77–80
79
Fig. 1. (a) The changes in the fluorescence spectra (excitation at 345 nm) of L (5.0 ꢀ 10ꢁ5 M) in the presence of different metal ions (5.0 ꢀ 10ꢁ5 M) in CH3CN–HEPES buffer
solution (9:1, pH 7.4). (b) The histogram of selectivity for various metal ions.
Fig. 2. (a) Fluorescence spectrum of L (5.0 ꢀ 10ꢁ5 M) upon addition of Al3+ in CH3CN–HEPES solution (pH 7.4). Excitation at 345 nm, Red represents the ligand without the
addition of Al3+. (b) The association constant between L and Al3+ from Benesi–Hildebrand expression.
for the fluorescence change. It was also clear that the PET process,
which was switched on by Al3+ as the excitation at 345 nm, re-
sulted in the emission of L–Al3+ with a maximum wavelength at
500 nm. As shown in Fig. 2b, the association constant for Al3+
was estimated to be 3.92 ꢀ 106 Mꢁ1 in aqueous media (pH 7.4)
by fitting the data to the Benesi–Hildebrand expression (I0/(I–
.
I0) = I0/[L] + I0/[L].Ks [M]) with a good linear relationship [22,23]. I
is the change in the fluorescence intensity at 500 nm, Ks is the sta-
bility constant, [L] and [M] are the concentration of L and Al3+
,
respectively. I0 is the fluorescence intensity of L in the absence of
Al3+. On the basis of the plot of 1/[I] versus 1/Al3+, the binding con-
stant can be obtained. It demonstrated the there was a high bind-
ing tendency between L and Al3+
.
Additionally, by the Job plot shown in Fig. 3, the binding mode
between L and Al3+ was investigated systemically. We could deduce
that there was a 1:1 stoichiometry between them. Moreover, in
accordance with the 1:1 stoichiometry, the fluorescent turn-on
chemosenor was most likely to chelate with Al3+ via its carbonyl
O, imino N and 20-hydroxyacetophenone O atoms. And the coordina-
tion stoichiometry between L and Al3+ is in accordance with the data
from ESI-MS (Fig. S4).
Fig. 3. Job’s plot according to the method for continuous variations, indicating the
1:1 stoichiometry for L–Al3+ (the total concentration of L and Al3+ is 2.0 ꢀ 10ꢁ5 M)
(kex = 345 nm).

80
Z. Liu et al. / Inorganica Chimica Acta 395 (2013) 77–80
L. With addition of Al3+, the absorption spectrum changed signifi-
cantly with the solution turning from colorness to yellow, clearly
indicating the interaction of L with Al3+. A new absorption bands
appeared obviously at 450 nm upon addition of Al3+, which also
indicated the coordination between L and Al3+ lead to the mutli-
wavelength emissive fluorescence emission.
4. Conclusions
In summary, we have developed 3-[10-(20-hydroxy-
enzylidene-imino)]-2-(p-N,N-dimethylaminophenyl)-1,2-dihydro-
a-methylb-
quinazolin-4-(3H)-one
based
multi-wavelength
emissive
fluorescent chemosensor for Al3+. It exhibits high selectivity to-
ward Al3+ over other metal ions in aqueous media (pH 7.4). More-
over, according to the investigation, 1:1 stiochiometry between L
and Al3+ is formed. The excellent selectivity of chemosensor for
Al3+ in aqueous media (pH 7.4) indicates its potential application
value in the biological monitoring and tracking of Al3+
.
Fig. 4. The selectivity of L for Al3+ in the presence of other metal ions (Na+, Mg2+
,
Co2+, Ni2+, Cu2+, Fe3+, Cr3+, Hg2+, Zn2+, Cd2+) in CH3CN–HEPES (pH 7.4). Excitation at
345 nm. The response is normalized with respect to background fluorescence of the
free L (5.0 ꢀ 10ꢁ5 M). Al3+ (5.0 ꢀ 10ꢁ5 M) is added at first. Then other metal ions
were added (5.0 ꢀ 10ꢁ5 M).
Acknowledgment
This work is supported by the National Natural Science Founda-
tion of China (Nos. 20975046, 81171337).
Appendix A. Supplementary material
The 1H NMR, 13C NMR, ESI-MS of 3-[10-(20-hydroxy-
enzylidene-imino)]-2-(p-N,N-dimethylaminophenyl)-1,2-dihydro-
quinazolin-4-(3H)-one and ESI-MS of 3-[1’-(2’-hydroxy-
a-methylb-
a-
methylbenzylidene-imino)]-2-(p-N,N-dimethylaminophenyl)-1,2-
dihydroquinazolin-4-(3H)-one with Al3+ in aqueous media were
listed in supplementary materials. Supplementary data associated
with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.ica.2012.10.009.
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alent amount of other metal ions (Na+, Mg2+, Co2+, Ni2+, Cu2+, Fe3+
,
Cr3+, Hg2+, Zn2+, Cd2+) were also added into the solution. Their fluo-
rescence intensities were recorded, respectively. The histogram of
fluorescence changes were listed in Fig. 4. As shown in Fig. 4, no
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sults indicated that the high selectivity of L toward Al3+ over other
co-existent metal ions in aqueous media (pH 7.4).
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3.2. The UV–Vis absorption spectroscopy response of L to Al3+
As shown in Fig. 5, the absorption spectrum of L (5.0 ꢀ 10ꢁ5 M)
in aqueous media (pH 7.4) exhibited a strong peak at 260 nm,
which was ascribed to the characteristic band of sensor molecule