Synthesis and characterization of Benz-X-azole based dye chemosensor

Article abstract of DOI:10.1080/15421401003609103

Concerns over heavy and transition metal ions such as copper, zinc and mercury are of topical interests because they are considered as highly toxic environmental pollutants. In this study, we have designed and synthesized new benz-X-azole derivatives as d

Full text of DOI:10.1080/15421401003609103

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Synthesis and Characterization of Benz-
X-azole Based Dye Chemosensor
a
a
a b
Young-A Son , Young-Sung Kim , Byung-Soon Kim
& Sung-Hoon
c
Kim
a
School of Chemical and Biological Engineering, Chungnam National
University , Daejeon, South Korea
b
Department of Environmental Sciences , Faculty of Education
and Human Sciences, Yokohama National University , Hodogaya-ku,
Yokohama, Japan
c
Department of Textile System Engineering , Kyungpook National
University , Daegu, South Korea
Published online: 19 Apr 2010.
To cite this article: Young-A Son , Young-Sung Kim , Byung-Soon Kim & Sung-Hoon Kim (2010) Synthesis
and Characterization of Benz-X-azole Based Dye Chemosensor, Molecular Crystals and Liquid Crystals,
519:1, 99-107, DOI: 10.1080/15421401003609103
To link to this article: http://dx.doi.org/10.1080/15421401003609103
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Mol. Cryst. Liq. Cryst., Vol. 519: pp. 99–107, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421401003609103
Synthesis and Characterization of Benz-X-azole
Based Dye Chemosensor
1
YOUNG-A SON, YOUNG-SUNG KIM,
1
1
BYUNG-SOON KIM, AND SUNG-HOON KIM
,2
3
1
School of Chemical and Biological Engineering, Chungnam
National University, Daejeon, South Korea
2
Department of Environmental Sciences, Faculty of Education and
Human Sciences, Yokohama National University, Hodogaya-ku,
Yokohama, Japan
3
Department of Textile System Engineering, Kyungpook National
University, Daegu, South Korea
Concerns over heavy and transition metal ions such as copper, zinc and mercury are
of topical interests because they are considered as highly toxic environmental pollu-
tants. In this study, we have designed and synthesized new benz-X-azole derivatives
as dye chemosensor and their selective and sensitive complex functions for heavy
metal ion detection were investigated. Electron density distributions and HOMO=
LUMO energy levels were computationally optimized. In addition, the formation
type of metal binding complex was determined by Job’s plot measurements and cyclic
voltammetry were conducted to determine comparison of the energy level potentials.
Keywords Absorption; benz-X-azole; complex function; computational
simulation; dye chemosensor; emission; heavy metal ion; HOMO=LUMO
Introduction
Since the first studies of the chemosensor reported on metal complex ligands such as
crown ether, cryptand and spherand in the structures, many interesting works have
been focused on the heavy and transition metal ions sensing [1–3]. Heavy and
transition metal ions such as calcium, copper, zinc and mercury are considered to
be highly dangerous metal ions in the human body and play an important role in
various biologic processes and systems [4–9]. Copper and zinc are significant metal
pollutants with higher concentrations in environmental systems. As well known, it
is connected to serious etiology of Alzheimer’s, Menke’s, and Wilson’s diseases [9].
Mercury is also considered to be highly toxic heavy metal ion in the biological
Address correspondence to Young-A Son, School of Chemical and Biological Engineer-
ing, Chungnam National University, Daejeon 305-764, South Korea. Tel.: þ82-42-821-6620;
Fax: þ82-42-823-3736; E-mail: yason@cnu.ac.kr and Sung-Hoon Kim, Department of Textile
System Engineering, Kyungpook National University, Daegu 702-701, South Korea. Tel.:
þ82-53-950-5641; Fax: þ83-53-950-6617; E-mail: shokim@knu.ac.kr
99

1
00
Y.-A. Son et al.
systems and plays a role in the physiologic process because it can be accumulated in
the organs [10–12]. Thus, the design of selective, sensitive and effective chemosensors
[13] and their measurement utilizations over heavy metal cations are of great
importance for chemical, biological, and environmental research areas.
In this study, we have designed and prepared of new benz-X-azole derivatives as
a dye chemosensor and their heavy metal ions complex functions were examined and
determined. Structures of the synthesized dye sensors 3 and 4 were identified. Metal
ions detection behaviors were discussed with UV-Vis absorption and fluorescent
emission optical measurements in details. Furthermore, electron density distribu-
tions and HOMO=LUMO energy levels of dye sensors 3 and 4 were computationally
optimized using the density function theory (DFT) with exchange correction
functional of local density approximation (LDA) based on the Perdew-Wang
(PWC) set. Cyclic voltammetry measurements were carried out to examine the
experimental HOMO=LUMO energy potentials.
Experimental
2
.1. Analysis
Absorption spectra were examined on Agilent 8453 UV-Vis spectrophotometer.
1
Fluorescence spectra measurements were performed on a Shimadzu RF-5301. H
NMR spectra were recorded on a JNM-AL400 MHz NMR instrument with TMS
as internal standard and elemental analyses were recorded on a Carlo Elba Model
1
106 analyzer. Electron distributions and energy potentials were calculated with
Material Studio 4.3. Cyclic voltammograms were examined with a VersSTAT3 using
three-electrode conventional electro chemical cell. Cyclic voltammetry experiment
was run in an acetonitrile solution containing tetrabutlyammonium hexafluoropho-
þ
sphate elelctrolyte. The reference electrode, Ag=Ag was directly immersed in the
reaction cell. The working electrode was a glassy carbon. The counter electrode
was a platinum wire. The scan rate was commonly 100 mV=s.
2
.2. Synthesis
Metal cation receptors 1 and 2 were prepared by condensing p-aminosalicylic acid,
.52 mmole (0.998 g), with o-aminophenol and o-aminothiophenol 6.52 mmole
6
(
0.711 g, 0.816 g) in 20 g of polyphosphoric acid (85% phophorus pentoxide) for
h at 200 C. After 3 h, the reaction was quenched into ice water and stirred for
4 h. The formed precipitate solution was adjusted to the neutral pH condition using
% sodium carbonate solution. After 3 h, the mixture was filtrated with distilled
ꢀ
ꢀ
3
2
1
water at several times and dried in oven at 40 C. The general procedures were
followed by the indicated references [14–16].
ꢀ
Dye 1, Yield: 23.03% (0.340 g); mp: 226.5–226.7 C. Anal. Calcd for C H N O :
1
3
10
2
2
1
C, 69.02; H, 4.46; N, 12.38: found; C, 69.16; H, 4.16; N, 12.81. H NMR (400 MHz,
CDCl ): d 4.00 (s, 2H), d 6.24 (d, 1H), d 6.28 (d, 1H), d 7.18–7.32 (m, 2H), d 7.42–7.50
3
(
m, 1H), d 7.52–7.62 (m, 1H), d 7.30 (d, 1H), d 11.47 (s, 1H).
ꢀ
Dye 2, Yield: 38.84% (0.614 g); mp: 211–213 C. Anal. Calcd for C H N OS: C,
10
13
2
1
4.44; H, 4.16; N, 11.56; S, 13.23: found; C, 64.55; H, 4.03; N, 11.52; S, 12.62. H NMR
6
(
400 MHz, DMSO-d ): d 5.95 (s, 2H), d 6.18 (d, 1H), d 6.28 (d, 1H), d 7.34 (t, 1H), d 7.48
6
(t, 1H), d 7.64 (d, 1H), d 7.90 (d, 1H), d 8.04 (d, 1H), d 11.80 (s, 1H).

Benz-X-azole Dye Chemosensor
101
Dye chemosensors 3 and 4 were obtained using the prepared metal ion receptor
dyes 1 and 2. The general procedures were described in the reported references [14–
1
6]. Terephthalaldehyde (0.1 mmole, 0.013 g) and metal ion receptor dyes 1 and 2
(
0.2 mmole, 0.045 g, 0.048 g) were stirred in 5 ml of benzene. 5 ꢁ 6 drops of piperidine
was added during the reaction. Reflux was continued for 2 days. The reaction was
cooled to room temperature and the reaction product was filtrated using benzene
at several times and dried in vacuum [17].
ꢀ
Dye 3, Yield: 34.80% (0.019 g); mp: 226.5–226.7 C. Anal. Calcd for C H N O :
3
4
22
4
4
1
C, 74.17; H, 4.03; N, 10.18: found; C, 73.69; H, 4.10; N, 9.45. H NMR (400 MHz,
CDCl ): d 4.29 (s, 4H), d 6.89 (s, 6H), d 7.51 (s, 6H), d 8.05 (s, 4H), d 10.14 (s, 2H).
3
ꢀ
Dye 4, Yield: 33.98% (0.020 g); mp: 211–213 C. Anal. Calcd for C H N O S :
3
4
22
4
2 2
1
C, 70.08; H, 3.81; N, 9.62; S, 11.01: found; C, 70.09; H, 4.04; N, 9.18; S, 10.95. H
NMR (400 MHz, CDCl ): d 5.29 (s, 4H), d 6.99 (s, 6H), d 7.51 (s, 6H), d 8.05 (s, 4H),
3
d 10.11–10.14 (d, 2H).
2
.3. Absorption and Fluorescence Emission
Absorption and fluorescence measurements were performed by the addition from 0
2
to 2 equiv. of different metal cations (Cu , Zn , and Hg ) in 3 ml of dye sensor (3
þ
2þ
2þ
ꢃ4
and 4) solutions (1.0 ꢂ 10 M). After being well mixed for 30 sec using Vortex
mixer, the absorption and fluorescence spectra were examined and determined.
For Job’s plot measurements, equimolar solution of dyes and metal ions
ꢃ4
(
1.0 ꢂ 10 M in acetonitrile) was prepared. And the dye sensors and metal ions were
then mixed in different volume ratios (1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, 10:0).
The maximum absorption of these mixtures was monitored.
Results and Dicussion
In this work, p-aminosalicylic acid and o-aminophenol (and o-aminothiophenol)
were used to synthesize the benz-X-azole dye derivatives as metal cation receptors.
After this reaction, the synthesized benz-X-azole dye intermediates 1 and 2 were
reacted with terephthalaldehyde to produce dyes 3 and 4 as a dye chemosensor for
the use of metal ion detections. Using these dyes, characterization studies and metal
ion detection properties were investigated to examine the feasibility for the use of dye
chemosensor purposes. These dyes 3 and 4 show promising chemical structures to be
used for metal binding reactions, namely dye chemosensing complex, where electron
rich groups or atoms such as nitrogen, sulfur and hydroxyl groups can be utilized to
be binding sites for this detection purpose. The structures of prepared dyes 3 and 4
are shown in Figure 1.
The metal cation complex ability and optical property of dye chemosensors 3
ꢃ4
2þ
2þ
2þ
and 4 (1.0 ꢂ 10 M) with different metal ions (Cu , Zn , and Hg ) were investi-
gated by UV-Vis absorption measurements. The changes in UV-Vis absorption spec-
tra of dye sensors 3 and 4 upon the addition of different metal ions in the chloroform
are shown in Figure 2(a) and (b), respectively. Figure 2 displays that the optical
absorption behaviors of dye 3 were changed by the addition of three metal cations,
2
þ
but dye 4 had selectively responded to Cu ions. The complex sensing ability of
2
these dye sensors 3 and 4 specially showed the recognition function to Cu ions
þ
2
among other metal. With increasing concentration of Cu to the solution of dye
þ
sensor 3, the absorption intensity peak at 390 nm gradually decreased, and a new

1
02
Y.-A. Son et al.
Figure 1. Synthetic routes for dye chemosensor.
ꢃ4
Figure 2. UV-Vis absorption spectra changes of dye sensors 3 (a) and 4 (b) (1.0 ꢂ 10 M) in
2þ
3
the presence of 2 equiv. molar of metal cations and more detailed titration with Cu in CHCl .

Benz-X-azole Dye Chemosensor
103
peak at 330 nm sharply increased with an isobestic point at 360 nm. In the case of dye
sensor 4, the isobestic point at 380 nm was clearly observed. The absorption intensity
of a new peak at 350 nm increased dramatically and a peak at 390 nm decreased with
2
þ
increasing concentration of Cu
Figure 3(a) and (b) show that the fluorescence emission changes of dye sensors 3
.
2
and 4 upon the addition of Cu ions. Similar to absorption changes, dye sensors 3
þ
2
and 4 were recognized with Cu , the fluorescence emission gradually increased.
þ
2
þ
With increasing with concentration of Cu to the solution of dye sensors 3 and
, the intensity of fluorescence emission band at 460 nm and 520 nm greatly
increased, respectively. The prepared dye sensors 3 and 4 were effectively and
4
ꢃ4
2þ
Figure 3. Fluorescence spectra of dye sensors 3 (a) and 4 (b) (1.0 ꢂ 10 M) titrated with Cu
3
in CHCl .

1
04
Y.-A. Son et al.
Figure 4. Job’s plots for dye sensors 3 (a) and 4 (b).
Figure 5. Electron density distributions and HOMO=LUMO energy levels of dye sensors 3 (a)
and 4 (b).

Benz-X-azole Dye Chemosensor
105
2
þ
selectively complexed with Cu ions, where the functions of dye chemosensor were
promisingly observed and confirmed.
To estimate and judge the complex formation type of dye sensor-metal cation,
Job’s plot [18] was used. In Job’s plot, the ratio of maximum absorption peak versus
mole fraction of the metal ions was 0.6 to 0.7, which was concluded to be 1:2
complex type of binding. The job’s plot findings showed these characteristics in
Figure 4. As previously shown in the Figure 1, metal ions might be bound to nitrogen
(
or sulfur) and hydroxyl group in metal ion receptor sites of dye sensor molecules.
Electron density distributions and molecular energy potential levels of dye sensors
and 4 were computationally simulated by Material studio 4.3 and the corresponding
3
results were illustrated in Figure 5. Figure 5 shows that the electron density distribu-
tions are mainly localized in benz-X-azole moieties in HOMO and the electrons are
densely distributed in terephthalaldehyde moiety in LUMO. Metal cations, namely
Figure 6. Cyclic voltammetry diagrams of dye sensors 3 (a) and 4 (b) in acetonitrile.

1
06
Y.-A. Son et al.
Table 1. Summary of HOMO=LUMO values of dye sensors 3 and 4
Computationally
calculated values
Cyclic voltammetry
obtained values
Dye sensors
HOMO
LUMO
DE
HOMO
LUMO
DE
3
4
ꢃ5.18
ꢃ5.28
ꢃ3.43
ꢃ3.55
1.75
1.73
ꢃ5.03
ꢃ5.13
ꢃ2.33
ꢃ2.40
2.70
2.73
electrophiles, may attack to the electron rich HOMO states, where the complexes
between dye sensors and metal cations can be coordinated. In other words, dye sensing
functions can be utilized in electron rich HOMO levels. This theory also well matched
with the electron density distributions in Figure 5. In HOMO levels, rich electron
distributions were localized in benz-X-azole binding sites having nitrogen (or sulfur)
and hydroxyl group, where the complexes were proceeded.
Figure 6 shows that the cyclic voltammograms of the dye sensors 3 and 4 in
ꢃ3
acetonitrile solution containing a dye concentration of 1.0 ꢂ 10 M with 0.05 M
TBAPF . Using the maximum peak potentials, HOMO energy levels were calculated
6
[19]. The LUMO energy levels were also calculated by the band-gap energy from
UV-Vis absorption fit curve.
HOMOðorLUMOÞðeVÞ ¼ ꢃ4:8 ꢃ ðEpeakpotential ꢃ E1=2ðFerroceneÞÞ
Where Epeakpotential and E1=2(Ferrocene) is the maximum (minimum) peak
potential of dyes and the half-wave potential of Ferrocene (0.42 V), respectively.
The obtained electrochemical results were in agreement with observed theoretical
calculation values. The summaries are listed in Table 1.
Conclusions
We have designed and synthesized the new dye chemosensors 3, 4 and even though dye
3 and 4 showed metal recognition, especially selective and sensitive complex properties
of dye 4 for harmful metal cations were interested. The dye sensors 3 and 4 showing
2þ
complex ability can be effectively recognized with Cu , where UV-Vis absorption
and fluorescence emission spectra were sharply changed. These dye sensors 3 and 4
formed 1:2 complexes with metal ions because dye sensors 3 and 4 have two metal
complex legands in the molecular structures. The results were also confirmed by Job’s
plot measurements. Electron density distribution and HOMO=LUMO energy levels
were computationally simulated and the corresponding results were considered to
estimate the metal binding positions in dye sensor molecules. In addition, calculated
and experimented HOMO=LUMO energy levels were compared and the results were
well matched. Thus, the synthesized new dye sensors can be utilized as chemosensors
for the detection of metal cations in environmental and biological research areas.
Acknowledgments
This research was supported by the Program for the Training of Graduate Students
in Regional Innovation which was conducted by the Ministry of Commerce Industry

Benz-X-azole Dye Chemosensor
107
and Energy of the Korean Government. This work was supported by the Korean
Science and Engineering Foundation (KOSEF) grant funded by the Korea govern-
ment (MEST) (No. 2009-0063408).
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