Hg2+ mediated quinazoline ensemble for highly selective recognition of Cysteine

Article abstract of DOI:10.1016/j.saa.2013.12.054

A fluorimetric sensor for Hg²⁺ ion and Cysteine based on quinazoline platform was designed and synthesized by one step reaction and characterized by using common spectroscopic methods. Time Dependent Density Functional Theory calculations shows that probe behaves as "ON-OFF" fluorescent quenching sensor via electron transfer/heavy atom effect. Receptor was found to exhibit selective fluorescence quenching behavior over the other competitive metal ions, and also the receptor-Hg²⁺ ensemble act as an efficient "OFF-ON" sensor for Cysteine. Moreover this sensor has also been successfully applied to detection of Hg²⁺ in natural water samples with good recovery.

Full text of DOI:10.1016/j.saa.2013.12.054

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Hg2+ mediated quinazoline ensemble for highly selective recognition of
Cysteine
⇑
Thangaraj Anand, Gandhi Sivaraman, Duraisamy Chellappa
School of Chemistry, Madurai Kamaraj University, Madurai 625021, India
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
ꢀ
A quinazoline A1 derived was
synthesized and used to recognize
Hg2+
.
ꢀ
ꢀ
The Hg2+ detection limit
(3.5 ꢁ 10ꢂ7 mol Lꢂ1) is reported.
This fluorescence change was further
supported by DFT/TD-DFT
calculations.
ꢀ
ꢀ
The probe A1 + Hg2+ ensemble is also
further successfully utilized for
detection of the Cysteine.
This system can also be applied in
real samples.
a r t i c l e i n f o
a b s t r a c t
A fluorimetric sensor for Hg2+ ion and Cysteine based on quinazoline platform was designed and synthe-
sized by one step reaction and characterized by using common spectroscopic methods. Time Dependent
Density Functional Theory calculations shows that probe behaves as ‘‘ON–OFF’’ fluorescent quenching
sensor via electron transfer/heavy atom effect. Receptor was found to exhibit selective fluorescence
quenching behavior over the other competitive metal ions, and also the receptor-Hg2+ ensemble act as
an efficient ‘‘OFF–ON’’ sensor for Cysteine. Moreover this sensor has also been successfully applied to
detection of Hg2+ in natural water samples with good recovery.
Article history:
Received 12 October 2013
Received in revised form 28 November 2013
Accepted 4 December 2013
Available online 18 December 2013
Keywords:
Quinazoline
Hg2+
Ó 2013 Elsevier B.V. All rights reserved.
Cysteine
Quenching
ON–OFF
Real sample analysis
Introduction
derived from ionic/elemental mercury by bacteria affects a preg-
nant woman that reflects development delays in child [8,9]. The
In recent years the recognition and monitoring of the heavy me-
tal ions such as Hg2+, Pb2+, Cd2+ and Cu2+ is one of the most chal-
lenging field [1–4]. Design and synthesis of selective sensor for
Hg2+ is particularly important, since Hg2+ is hazardous metal and
can cause detrimental effects on the environment even at very
low concentration [5]. Mercury can easily penetrate through the
skin and respiratory cell membranes and create difficulty in
thyroid and adrenal hormone system [6]. Methyl mercury [7]
US Environmental Protection Agency (EPA) recommended a limit
of 2 ppb of Hg2+ in potable water [10]. Due to these harmful effects,
designing new chromophore for analysis of Hg2+ becomes signifi-
cant. Various techniques such as atomic absorption spectroscopy
[11], atomic emission spectroscopy [12], electro chemical methods
[13,14] and photophysical methods have been used to detect the
transition/heavy metal ions. Among these, photophysical methods
are widely used due to its high selectivity, sensitivity and simple
way of sample preparation. On the other hand intracellular thiol
containing amino acids play vital role in biosynthesis and they
are functional compounds of many proteins and enzymes
⇑
Corresponding author. Tel.: +91 452 2456614; fax: +91 452 2459181.
E-mail address: dcmku123@gmail.com (D. Chellappa).
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.12.054

T. Anand et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
19
[15–17]. Cysteine (Cys) and Homo Cysteine (Hcy) are biologically
essential molecules required for the growth of cells and tissues
in living systems. Especially the Cysteine levels are linked to many
diseases such as Alzheimer, AIDS and cancer. Deficiency of Cysteine
can cause delayed growth, liver damage, oedema, lethargy, fat loss,
skin lesions and Psoriasis etc., [18,19].
Synthesis of 3-amino-2-thioxo-2,3-dihydroquinazolin-4(1H)-one (A1)
Ethanolic solution containing 2-aminobenzohydrazide (0.483 g,
3.2 mmol), sodium hydroxide (0.13 g, 3.2 mmol) and carbon disul-
phide (0.25 g, 3.2 mmol) was refluxed for 15 h. The excess solvent
was distilled off under reduced pressure. The residue was washed
with water and treated with 1:1 HCl and subsequently washed
several times with water. Recrystallized from ethanol to get a
white solid (Scheme 1). Yield: 65%. Melting point: 205–207 °C.
1H NMR (300 MHz, DMSO) ppm d 14.72 (s, 1H), 7.53 (dd, J = 8.0,
1.4 Hz, 1H), 7.29–7.23 (m, 1H), 6.90–6.85 (m, 1H), 6.65 (dd,
Numerous fluorescent chemosensors designed for sensing
Hg2+ based on coumarin derivatives [20,21], Hydroxyquinoline
[22], Podants [23,24], Rhodamines [25], Pyrene derivatives [26],
quinazoline [27] and heterocyclic based moieties [28] culminated
in either large fluorescence enhancement or quenching phenom-
ena. Huang et al. [29] reported anthraquinone containing thio-
urea subunit as a colorimetric sensor for Hg2+. 2-Aminopyridine
unit has been utilized for the fluorescent detection of Hg2+ by
Ghosh et al. [30]. However most of the reported sensors have dif-
ficulty in distinguishing Hg2+ from Ag+ or Fe3+, which compete
with Hg2+ for the binding sites of the sensor molecule. Mecha-
nisms such as photo induced electron transfer (PET) [31], intra-
molecular charge transfer (ICT) [32], twisted intramolecular
charge transfer (TICT) [33], metal–ligand charge transfer (MLCT)
[34] and fluorescence resonance energy transfer (FRET) [35] have
been invoked to explain the observed enhancement or quenching
of fluorescence. In many of the fluorescent chemosensors for Hg2+
there may be a large fluorescence quenching because of PET
property and heavy atom effect [36,37]. Hitherto reported Hg2+
recognizing target compounds experienced multistep synthesis
and tedious work-up. Therefore the design of sensors that can
be easily synthesized for Hg2+ binding is of particular interest.
The receptor containing nitrogen/oxygen and sulfur atom prefers
the coordination of Hg2+ [38] over the competing transition metal
ions. Besides Hg2+ various fluorescent chemosensors has been de-
signed for the recognition of biological thiols based on different
mechanism [39–43]. Due to the strong affinity of thiols towards
Hg2+, the thiol containing amino acids easily binds with the
Hg2+ ions. Recently, Fu et al. [44] and Li et al. [45] proposed a
squarine and thiacalixarene-Hg2+ ensemble fluorescence assay
for thiol containing amino acids, which involves enervating syn-
thetic procedures.
J = 11.1, 4.0 Hz, 1H), 6.17 (s, 2H).13
C NMR (75 MHz, CDCl3):
181.107, 165.899, 152.385, 137.796, 132.192, 121.264, 120.873,
108.351. ESI–MS: observed: 192.06 (M–H)ꢂ. Calculated: 193.12.
(Figs. S1–S3). Anal. Found: C: 56.25, H: 6.2, N: 27.8, Cal. for: C:
56.01, H: 5.99, N: 28.0%.
Calculation of binding constant
The association constant of Hg2+ was calculated from the fluo-
rescence titration data using the following equation:
ln½ðF ꢂ F0Þ=ðF1 ꢂ FÞꢃ ¼ n ln½Hg2þꢃ þ n ln ðKasscnÞ
In above equation, n refers to the number of Mercury ions asso-
ciating with each molecule of A1, Kasscn refers to the association
constant, F0, F and F1 refers to the fluorescence intensities solution
of chemosensor A1 alone, A1 with any concentration of Hg2+, and
at high concentration of Hg2+ ion.
Calculation of detection limit
LOD was calculated based on the standard deviation of the re-
sponse (SD) and the slope of the calibration curve (S) at levels
approximating the LOD according to the formula:
LOD ¼ 3ðSD=SÞ
In the present study, we have synthesized the probe A1 from
2-aminobenzohydrazide with CS2 in single step process
Results and discussions
according to
a
literature procedure [46,47]. Recently, Thar
To get an insight into the selectivity, UV–Visible measurements
of the probe A1 were carried out with the addition of various metal
ions. The UV–Visible spectrum of probe A1 shows two peaks at
284 nm and 334 nm. Upon incremental addition of chloride salt
of Hg2+ (0–2.0 eq) absorption maximum of probe at 284 nm shifted
rapidly and the band at 334 nm decreased. In the presence of Hg2+
the band at 284 nm is blue shifted to 276 nm. This blue shift along
with hypochromism may be attributable to the binding of Hg2+
with the probe A1 (Fig. S4). Only Hg2+ ion addition show changes
in the absorption spectra, while the addition of other metal ions
et al. reported the same probe as an electrochemical sensor
for silver by employing stripping voltammetry method [48].
A1 is highly selective and sensitive turn-off fluorescent sensor
for Hg2+ which could be utilized to quantify Hg2+ levels for
health care and environmental monitoring. Further we applied
the A1 + Hg2+ ensemble as a turn-on fluorescence sensor for
Cysteine.
Materials and methods
such as Cu2+, Co2+, Fe3+, Ni2+, Mn2+, Zn2+, Cd2+, Ag+, Ba2+, Al3+
,
Ca2+, Cr3+, K+ and Na+ did not show any shift in the band wave-
lengths (Fig. 1). So the receptor A1 was a selective and sensitive
sensor probe for Hg2+ ions.
General
2-Aminobenzohydrazide, amino acids was purchased from
Sigma–Aldrich. Carbon disulphide and metal chloride salts were
obtained from Merck. All the solvents were of analytical grade.
1H and 13C NMR was measured on BRUKER (Advance) 300 MHz
instrument. UV–Visible spectra were recorded on a JASCO V-
550 spectrophotometer, fluorescence analysis were done by
using JASCO-spectrofluorimeter. Electro spray ionization mass
spectrometer studies were carried out by using LCQ fleet ther-
mo fisher instruments limited, US. The pH measurements were
made with a Model PHS-25B meter. DFT calculations were car-
ried out at the B3LYP/LANL2DZ level by using the Gaussian 03
program.
The probe A1 exhibits a strong emission when excited at
350 nm. The photonics of the A1 was further explored with the
addition of other metal ions such as Cu2+, Co2+, Fe3+, Ni2+, Mn2+
Zn2+, Cd2+, Ag+, Ba2+, Al3+, Ca2+, Cr3+, K+ and Na+ including Hg2+
,
.
Among the metal ions investigated only Hg2+ selectively quenches
the fluorescence intensity of A1 (Fig. 2). While the other alkali such
as Na+ and K+, alkaline such as Ca2+ and Mg2+ and transition metal
ions Cu2+, Co2+, Fe3+, Ni2+, Mn2+, Zn2+, Cd2+ and Ag+ exhibit no fluo-
rescence quenching response under the same spectroscopic condi-
tion used for the Hg2+
.
Upon addition of Hg2+ from 0 to 2.0 eq the fluorescence inten-
sity started quenching steadily (Fig. 3). The fluorescence quenching

20
T. Anand et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
Scheme 1. Synthesis of probe (A1).
Fig. 1. UV–Visible spectra of (A1) 3-amino-2-thioxo-2,3-dihydroquinazolin-4(1H)-
one upon addition of Hg2+ ion and other transition metal ions such as Cu2+, Co2+
,
Fig. 3. Fluorescence emission spectra of (A1) 3-amino-2-thioxo-2,3-dihydroqui-
nazolin-4(1H)-one upon addition of Hg2+ ion (0–2 equiv.) in DMSO:H2O (1:9, V/V),
(kex = 350 nm, kem = 401 nm, slit:5 nm/5 nm).
Fe3+, Ni2+, Mn2+, Zn2+, Cd2+, Ag+, Ba2+, Al3+, Ca2+, Cr3+, K+ and Na+ (0–2 equiv.) in
DMSO:H2O (1:9, V/V).
Fig. 4. The Job’s plot mole fraction of probe vs fluorescence intensity at
kem = 401 nm.
Fig. 2. Fluorescence emission spectra of (A1) 3-amino-2-thioxo-2,3-dihydroqui-
nazolin-4(1H)-one (1 ꢁ 10ꢂ5 M) upon addition of Hg2+ ion and other transition
metal ions such as Cu2+, Co2+, Fe3+, Ni2+, Mn2+, Zn2+, Cd2+, Ag+, Ba2+, Al3+, Ca2+, Cr3+
,
K+ and Na+ (0–2 equiv.) in DMSO:H2O (1:9, V/V), (kex = 350 nm, kem = 401 nm,
slit:5 nm/5 nm).
fluorescence titration data (Fig. 4), suggested the 2:1 binding
between probe and Hg2+. It was further supported by ESI–MS
wherein the molecular ion peak at m/z = 609 corresponds to
[(A1)2 + Hg2+ + Na]+ (Figs. S6 and S7). The fluorimetric titration
profile shows a steady quenching of fluorescence with increase in
concentration of Hg2+. The binding constant [49] between probe
of probe upon complexation with Hg2+ may be attributable to the
heavy atom effect followed by the electron transfer. Therefore A1 is
selective towards Hg2+ over various metal ions (Fig. S5).
In order to understand the binding mode of Hg2+ with A1 job’s
plot measurements was carried out. Job’s plot constructed from

T. Anand et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
21
A1 and Hg2+ was 4.54 ꢁ 102 Mꢂ2 (Fig. S8). The detection limit
[50,51] calculated by reported methods was found to be
3.5 ꢁ 10ꢂ7 M.
The influence of various metal ions conducted in the presence of
Hg2+ (0.5 eq) with the addition of Cu2+, Co2+, Fe3+, Ni2+, Mn2+, Zn2+
,
Cd2+, Ag+, Ba2+, Al3+, Ca2+, Cr3+, K+ and Na+ (1 eq) show no signifi-
cant change in the fluorescence quenching in comparison with that
observed by the addition of Hg2+ without the other transition me-
tal ions. This result shows that probe has good sensitivity and
selectivity towards Hg2+ over the other competitive metal ions
(Fig. 5).
The influence of pH on fluorescence intensity of A1 was inves-
tigated in the presence of acidic and basic medium (Fig. 6). The
fluorescence intensity of A1 completely vanished in the presence
of higher pH (2–4 pH) values. Under 4–6 pH the intensity was
quenched gradually along with the addition of acid and no new
band was obtained. Quenching of fluorescence could be attribut-
able to the protonation of primary amine and secondary amine
of quinazoline moiety. However in lower pH range (9–12 pH), fluo-
rescence intensity at 401 nm was shifted. When the medium
became basic, a new emission band at 490 nm was appeared,
which corresponds to the deprotonation of ANH attached with
C@S and it can be stabilized by keto-thiol tautomerism. Besides
the CASꢂ ion forms hydrogen bond with the amine group, and this
bond formation is the main criteria for the fluorescence shift and
color change. More importantly A1 exhibits blue to cyan fluores-
cence under basic medium and that can be visually detected. Thus,
pH of 7 was selected as working range for their studies. 1H NMR
spectra of probe in DMSO-d6 before and after the addition of
hydrochloric acid and sodium hydroxide have been recorded
(Fig. 7). Upon addition of 0.5 eq of hydrochloric acid, the signal of
amine proton at 6.5 ppm became broad and NAH peak at
14.5 ppm disappeared due to the protonation of NH and NH2.
Whereas NAH peak at 14.55 ppm was slowly suppressed with
incremental concentration of NaOH. At the same time, NH2 proton
peak at 6.55 ppm disappeared immediately. This clearly indicates
that the NH and NH2 peak was deprotonated in the presence of
base.
Fig. 6. pH Effect on the fluorescence intensity (at 401 nm) of solution A1 (10
DMSO/H2O (9:1, v/v). Inset shows the corresponding titration plot at 490 nm.
l
M) in
Real sample analysis of Hg2+
In order to examine the practical applicability of the sensor
developed herein, it was preliminarily applied to the determina-
tion of Hg2+ in natural water samples from River water, drinking
water and tap water. Each recovery of Hg2+ was determined by
comparing the results obtained before and after the addition of 0,
50, 100 l
g of Hg2+ to the diluted water samples, the results ob-
tained before and after the addition of Hg2+ to the water samples
were listed in Table 1. The observed results show that A1 is able
to measure the concentrations of spiked Hg2+ with good recovery.
The recoveries of Hg2+ in these three were 97–98.9%, which vali-
dated the reliability and practicality of this method.
Detection of Cysteine
Cu2+ and Hg2+ are highly attractive for the thiol based amino
acids, because these metal ions have high affinity towards the thi-
ols [52–54]. The reversible nature of A1 + Hg2+ ensemble was ver-
ified in the presence of different amino acids such as Aspartic acid
(Asp), Cysteine (Cys), Glutamic acid (Glu), Glycine (Gly), Glutathi-
one (GSH), Serine (Ser), Glutamine (Gln), Tyrosine (Tyr), Arginine
(Arg), Lysine (Lys), Histidine (His), Alanine (Ala) and Valine (Val).
Addition of Cysteine to the solution of A1 + Hg2+ emission band
at 401 nm was greatly increased; addition of other amino acids
did not induce obvious change (Fig. 8). Upon addition of increasing
concentration of Cysteine into the solution of A1 + Hg2+ the fluo-
rescence was restored by the removal of Hg2+ indicating that
receptor A1 is a reversible chemosensor (Fig. S9). The binding con-
stant between Hg2+ and Cysteine was 6.41 ꢁ 102 Mꢂ2 (Fig. S10).
The binding constant for the Hg2+–Cysteine complex is higher
[55] than that of A1 + Hg2+, hence the dissociation of A1 + Hg2+
leads to the enhancement of fluorescence.
DFT calculations
In order to understand the fluorescence quenching process of
A1 with Hg2+, DFT/TDDFT calculations were carried out with
Gaussian 03 program [56]. The geometries of A1, (A1)2Hg2+ were
optimized by B3LYP/631G and B3LYP/LanL2DZ methods respec-
tively. The TD-DFT calculations of probe A1 shows a transition at
348.29 (0.368). In probe HOMO resides on the receptor sulfur atom
Fig. 5. Bar chart illustrating the selectivity in fluorescence response of probe A1 for
Hg2+ ion in the presence of other metal ions. The cyan bars represent the
fluorescence intensity of A1 in the presence of one equivalent of the other metal
ions. The magenta bars represent the change in fluorescence intensity that occurs
upon subsequent addition of one equivalent of Hg2+ to the solution containing
probe A1 and the other metal ions in DMSO/H2O(1:9,v/v) 10 mM, (kex = 350 nm,
kem = 401 nm, slit:5 nm/5 nm).

22
T. Anand et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
Fig. 7. 1H NMR spectral changes of A1 in DMSO-d6 in the presence of acid (a) base (b).
whereas LUMO spreads on the whole molecule and this HOMO–
LUMO energy gap (kcal = 352 nm) corresponds to that of n–p* tran-
Table 1
Determination of Hg2+ in drinking water, tap water and river water samples with A1.
sitions (Fig. 9).
Sample
Hg2+ added (
l
g Lꢂ1
)
Hg2+ found (
l
g Lꢂ1
)
Recovery (%)
Similar calculations for A1 + Hg2+ show two transitions with
wavelength at 372.48 (0.0410), 322.46 (0.00881). After binding of
Hg2+ with probe the LUMO has more metal character whereas
the HOMO is essentially localized on the sulfur atom with little
spread on fluorophore moiety and virtually not having metal char-
acter (Fig. 10).
Drinking water
A
B
C
0
50
100
–
–
98.9
99.0
50.06a 0.01b
a
100.09
0.03b
Tap water
A
B
C
0
50
100
–
–
50.02a 0.05b
99.7
99.56
Upon excitation with wavelength at 350 nm, it is expected that
HOMO to LUMO transitions can occur while HOMO-1 to LUMO
transitions may not occur due to very small oscillator strength.
The HOMO to LUMO transitions leads to an electron transfer from
fluorophore to Hg2+ metal center similar to the earlier reports of
Fabbrizzi and Bergonzi et al. [57,58]. This results in reducing
Hg2+ to Hg+. Hg+ ion by virtue of being paramagnetic and heavy
atom causes quenching of fluorescence.
a
100.00
0.07b
River water
A
B
C
0
50
100
–
–
a
50.09
100.04
0.015b
97.8
97.91
a
0.06b
a
Average of 3 measurements.
Standard deviation.
b

T. Anand et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
23
Conclusion
We have shown that the fluorescent probe (3-amino-2-thioxo-
2, 3-dihydroquinazolin-4(1H)-one) A1 is selective and sensitive for
detection of Hg2+ chloride in aqueous medium. Addition of Hg2+ to
the probe A1 shows large fluorescence quenching and it is highly
selective towards Hg2+ over the other competing metal ions and
however the quenching of fluorescence was reversible by using
Cysteine. The probe A1 binds with Hg2+ in 2:1 stoichiometry as
confirmed by job’s plot and ESI–MS studies. From TD-DFT calcula-
tion, the fluorescence quenching of A1 with Hg2+ was ascertained,
heavy atom effect followed by electron transfer mechanism. Fur-
thermore, practical applications are carried out. The probe exhib-
ited high selectivity toward Hg2+ in natural water samples with
satisfactory recovery.
Fig. 8. Fluorescence emission spectra of A1 + Hg2+ upon addition of increasing
concentration of Cysteine and other amino acids such as Asp, Glu, Gly, GSH, Ser, Gln,
Tyr, Arg, Lys, His, Ala and Val in DMSO:H2O(1:9, v/v) (kex = 350 nm, kem = 401 nm,
slit:5 nm/5 nm).
Acknowledgement
T.A, G.S. thanks DST-PURSE and UGC for research fellowship
respectively. T.A., G.S. and D.C. also acknowledge DST-IRHPA, FIST
and PURSE for funding and instrumental facilities. We thank Prof.
S. Krishnaswamy, School of Biotechnology, for providing access to
the spectrofluorimeter facility.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2013.12.054.
References
[1] M.F. Wolfe, S. Schwarbach, R.A. Sulaiman, Environ. Toxicol. Chem. 17 (1998)
146–148.
[2] P. De Silva, H.Q.N. Gunarantne, T. Gunnlaugsson, A.J.M. Huxely, C.P. Mc Coy, J.T.
Raemacher, T.E. Rice, Chem. Rev. 97 (1997) 1515–1566.
[3] E.M. Nolan, S.J. Lippard, Chem. Rev. 108 (2008) 3443–3480.
[4] H.N. Kim, W.X. Ren, J.S. Kim, J. Yoon, Chem. Soc. Rev. 41 (2012) 3210–3244.
[5] J. Wang, X. Qian, Chem. Commun. 7 (2006) 109–111.
[6] P.B. Tchounwou, W.K. Ayensu, N. Ninashvili, D. Sutton, Environ. Toxicol. 18
(2003) 149–175.
Fig. 9. Calculated electronic transitions of probe A1.
[7] H.H. Haris, I.J. Pickering, G.N. George, Science 301 (2003) 1203.
[8] P. Grandejan, P. Weihe, R.F. White, F. Debes, Environ. Res. 77 (1998) 165–172.
[9] H. Matsumoto, G. Koya, T. Takeuchi, J. Neuropathol. Exp. Neurol. 24 (1965)
563–564.
[10] Mercury Update: Impact on Fish Advisories; EPA Fact Sheet EPA-823-F-01-
001; Environmental Protection Agency, Office of Water: Washington, DC,
2001.
[11] C.M. Tseng, A.D. Diego, F.M. Martin, D. Amouroux, X. Donard, J. Anal. Atom.
Spectrom. 12 (1997) 743–750.
[12] A.N. Anthemidis, G.A. Zachariadis, C.E. Michos, J.A. Stratis, Anal. Bioanal. Chem.
379 (2004) 764–769.
[13] W. Yantasee, Y.H. Lin, T.S. Zemanian, G.E. Fryxell, Analyst 128 (2003) 467–472.
[14] A. Caballero, V. Lloveras, D. Curiel, A. Tarrage, A. Espinosa, R. Garcia, J. Vidal-
Gancedo, C. Rovira, K. Wurst, P. Molina, J. Veciana, Inorg. Chem. 46 (2007) 825–
838.
[15] J.B. Schulz, J. Lindenau, J. Seyfried, J. Dichgans, Eur. J. Biochem. 267 (2000)
4904–4911.
[16] Z.A. Wood, E. Schroder, J.R. Harris, L.B. Poole, Trends Biochem. Sci. 28 (2003)
32–40.
[17] H.S. Jung, X. Chen, J.S. Kim, J. Yoon, Chem. Soc. Rev. 42 (2013) 6019–6031.
[18] H. Refsum, P.M. Ueland, O. Nygard, S.E. Vollset, Ann. Rev. of Med. 49 (1998)
31–62.
[19] S. Shahrokhian, Anal. Chem. 73 (2001) 5972–5978.
[20] S. Voutsadaki, G.K. Tsikalas, E. Klontzas, G.E. Froudakis, E. Haralambos, E.
Katerinopoulos, Chem. Commun. 46 (2010) 3292–3294.
[21] J.H. Kim, H.J. Kim, S.H. Kim, J.H. Lee, J.H. Do, H.J. Kim, J.H. Lee, J. S. Kim
Tetrahedron Lett. 50 (2009) 5958–5961.
[22] H. Zhang, L.F. Han, K.A. Zachariasse, Y.B. Jiang, Org. Lett. 7 (2005) 4217–4220.
[23] J.S. Kim, M.G. Choi, K.C. Song, K.T. No, S. Ahn, S. Khang, Org. Lett. 9 (2007)
1129–1132.
[24] K.H. Chen, C.Y. Lu, H.J. Cheng, S.J. Chen, C.H. Hu, A.T. Wu, Carbohydr. Res. 345
(2010) 2557–2561.
[25] X.F. Yang, Y. Lia, Q. Bai, Anal. Chim. Acta. 584 (2007) 95–100.
[26] G. Sivaraman, T. Anand, D. Chellappa, RSC Adv. 2 (2012) 10605–10609.
[27] Q. Mei, L. Wang, B. Tian, F. Yan, B. Zhang, W. Huang, B. Tong, New J. Chem. 36
(2012) 1879–1883.
Fig. 10. Calculated electronic transitions of A1 + Hg2+
.

24
T. Anand et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 123 (2014) 18–24
[28] H. Yang, Z. Zhou, F. Li, T. Yi, C. Huang, Inorg. Chem. Commun. 10 (2007) 1136–
1139.
[48] A. Mohadesi, M. Ali Taher, Talanta 71 (2007) 615–619.
[49] K.A. Connors, Binding Constants, Wiley, New York, 1987.
[29] H. Lu, L. Xiong, H. Liu, M. Yu, Z. Shen, F. Li, X. You, Org. Biomol. Chem. 7 (2009)
2554–2558.
[30] R.R. Koner, S. Sinha, S. Kumar, C.K. Nandi, S. Ghosh, Tetrahedron Lett. 53 (2012)
2302–2307.
[50] X.F. Yang, L.P. Wang, H.M. Xu, M.L. Zhao, Anal. Chim. Acta. 631 (2009) 91–95.
[51] Y. Yang, J.H. Jiang, G.L. Shen, R.Q. Yu, Anal. Chim. Acta. 636 (2009) 83–88.
[52] Y. Fu, H. Li, W. Hu, D. Zhu, Chem. Commun. (2005) 3189–3191.
[53] N. Shao, J.Y. Jin, S.M. Cheung, R.H. Yang, W.H. Chan, T. Mo, Angew. Chem. Int.
45 (2006) 4944–4948.
[31] P. De Silva, T.S. Moody, G.D. Wright, Analyst 134 (2009) 2385–2393.
[32] V. Tharmaraj, S. Devi, K. Pitchumani, Analyst 137 (2012) 5320–5324.
[33] V. Tharmaraj, K. Pitchumani, Anal. Chim. Acta. 751 (2012) 171–175.
[34] S.K. Chung, Y.R. Tseng, C.Y. Chen, S.S. Sun, Inorg. Chem. 50 (2011) 2711–2713.
[35] G. He, X. Zhang, C. He, X. Zhao, C. Duan, Tetrahedron 66 (2010) 9762–9768.
[36] S.Y. Moon, N.J. Youn, S.M. Park, S.K. Chang, J. Org. Chem. 70 (2005) 2394–2397.
[37] Z. Wu, Y. Zhang, J. Ma, G. Yang, Inorg. Chem. 45 (2006) 3140–3142.
[38] Q. Zhao, F.Y. Li, C.H. Huang, Chem. Soc. Rev. 39 (2010) 3007–3030.
[39] X. Chen, Y. Zhou, X. Peng, J. Yoon, Chem. Soc. Rev. 39 (2010) 2120–2135.
[40] C.C. Huang, W.L. Tseng, Anal. Chem. 80 (2008) 6345–6350.
[41] N. Shao, J. Jin, H. Wang, J. Zhang, R. Yang, W. Chan, Z. Abliz, J. Am. Chem. Soc.
132 (2010) 725–736.
[42] K.S. Lee, T.K. Kim, J.H. Lee, H.J. Kim, J.I. Hong, Chem. Commun. (2008) 6173–
6175.
[43] H. Maeda, H. Matsuno, M. Ushida, K. Katayama, K. Saekiand, N. Itoh, Angew.
Chem., Int. Ed. 44 (2005) 2922–2925.
[44] Q. Lin, Y. Huang, J. Fan, R. Wang, N. Fu, Talanta 114 (2013) 66–72.
[45] F. Miao, J. Zhan, J. Zhan, Z. Zou, D. Tian, H. Li, Tetrahedron 68 (2012) 2409–
2413.
[54] Z. Guo, S. Nam, S. Park, J. Yoon, Chem. Sci. 3 (2012) 2760–2765.
[55] W. Huang, C. Song, C. He, C. Duan, Inorg. Chem. 48 (2009) 5061–5072.
[56] Gaussian 03, Revision C.02, M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E.
Scuseria, M.A. Robb, J.R. Cheeseman, J.A. Montgomery Jr., T. Vreven, K.N. Kudin,
J.C. Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M.
CossiG. Scalmani, N. Rega, G.A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K.
Toyota, R. Fukuda, J Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H.
Nakai, M. Klene, X. Li, J.E. Knox, H.P.Hratchian, J.B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador, J.J.
Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas,
D.K. Malick, A.D. Rabuck, K.Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G.
Baboul, S. Clifford, J. Cioslowski, S.B.B. Tefanov, G. Liu, A. Liashenko, P. Piskorz,
I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. AlLaham, C.Y. Peng, A.
Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong,
C. Gonzalez, J.A. Pople, Gaussian Inc, Wallingford CT, 2004.
[57] R. Bergonzi, L. Fabbrizzi, M. Licchelli, C. Mangano, Coord. Chem. Rev. 170
(1998) 31–46.
[46] A.K. Singh, R.P. Singh, J. Inorg. Nucl. Chem. 42 (1980) 286–288.
[47] E. Cherbuliez, B. Willhalm, S. Jaccard, J. Rabinowitz, Helv. Chim. Acta. 50 (1967)
2563–2569.
[58] L. Fabbrizzi, M. Licchelli, P. Pallavicini, D. Sacchi, A. Taglietti, Analyst 121
(1996) 1763–1768.