Dual-signaling fluorescent chemosensor based on bisthiazole derivatives

Article abstract of DOI:10.1016/j.tetlet.2010.04.126

A new bisthiazole chemosensor (3) with phenolic substituents at the position 2 of the thiazole rings was prepared. The chemosensor 3 acts as a potential dual-function fluorescence chemosensor with Cu²⁺ and Zn²⁺ ions causing complete quenching and ratiometric change of fluorescence, respectively. The mechanism of fluorescence was based on the cation-induced inhibition of excited-state intramolecular proton transfer (ESIPT).

Full text of DOI:10.1016/j.tetlet.2010.04.126

Tetrahedron Letters 51 (2010) 3531–3535
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Dual-signaling fluorescent chemosensor based on bisthiazole derivatives
Aasif Helal a, Sang Hoon Lee a, Sung Hong Kim b, Hong-Seok Kim a,
*
a Department of Applied Chemistry, Kyungpook National University, Daegu 702-701, Republic of Korea
b Analysis Research Division, Daegu Center, Korea Basic Science Institute, Daegu 702-701, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
A new bisthiazole chemosensor (3) with phenolic substituents at the position 2 of the thiazole rings was
prepared. The chemosensor 3 acts as a potential dual-function fluorescence chemosensor with Cu2+ and
Zn2+ ions causing complete quenching and ratiometric change of fluorescence, respectively. The mecha-
nism of fluorescence was based on the cation-induced inhibition of excited-state intramolecular proton
transfer (ESIPT).
Received 23 February 2010
Revised 16 April 2010
Accepted 28 April 2010
Available online 20 May 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Bisthiazole
Fluorescence
ESIPT
Ratiometric sensing
Quenching
Fluorescent chemosensors provide a powerful optical method
for spying on molecular recognition events. As a result, they have
found practical application in cellular imaging, environmental
monitoring, and biological assays.1 Chemosensors that allow the
measurement of two different emission bands have the important
feature of permitting signal rationing, which can increase the dy-
namic range and provide built-in correction for environmental ef-
fects.2 Copper plays an important role in various biological
processes. It is a vital trace element, the third most abundant in hu-
mans, and is present at low levels in a variety of cells and tissues,
with its highest concentration in the liver. The average concentra-
a fluorescent chemosensor selective to zinc is of considerable
interest.10
Excited-state intramolecular proton transfer (ESIPT) is one of
the most common photophysical processes that occur in benzaz-
oles and used to develop ratiometric probes. Inhibition of the ESIPT
process by cation binding yields a significant hypsochromic shift of
the fluorescence emission maximum.11,12 In chemosensors a selec-
tive binding motif is attached to a fluorophore for signal transduc-
tion. However intrinsic fluorescent probes whose fluorescent unit
is directly involved in the interaction with metal ions help in quick,
sensitive, and selective detection.13
tion of blood copper in the normal group is 100–150
l
g/dL (15.7–
It is known that chelating groups such as C@N and C@O exhibit
a high affinity to transition and post-transition metal cations but a
less binding affinity toward alkali metal and alkaline earth metal
cations.14 Recently we have reported thiazole-based chemosensors
1 and 2 for use as anions and ratiometric fluorescence sensing of
zinc15,16 as illustrated in Figure 1. In both compounds the thiazole
ring is substituted by a phenol at the position 2 and phenyl (1) or
pyridine (2) at the position 4. Both exhibit the same mechanism for
fluorescence based on the anion or cation-induced inhibition of the
ESIPT. Thus a heteroaromatic ring system such as a bisthiazole
with phenolic groups at the position 2 can act as a –ONNO– donor
receptor with functionality highly selective to transitional metal
cations.17
Crown ethers that contain thiazole moieties have been reported
to exhibit high ammonium,18 silver,19 and mercury ion selectiv-
ity.20 Introduction of soft heteroatoms such as N and S, as an elec-
tron donor to metal cations can improve the binding selectivity
and along with a hydrogen-bonding donar (O–H) can produce
some photophysical properties. Our choice of bisthiazole with
23.6
l
M).3 Its high concentration in the neuronal cytoplasm may
contribute to the etiology of Alzheimer’s or Parkinson’s disease.4,5
Due to industrial applications as a pollutant and an essential trace
element in biological systems, much attention has been drawn to
the chemosensors for copper(II) based on the chromogenic and
fluorogenic probes which are expected to detect copper ions
quickly, nondestructively, and sensitively.6 Zinc(II) is the second
most abundant transition metal cation in the biological system.7
Approximately 300 enzymes contain zinc(II) as an essential com-
ponent, either for a structural purpose or as a part of a catalytic
site. For example, zinc is essential for the regulation of DNA syn-
thesis during the proliferation and differentiation of cells.8 Zinc is
also known to have a role in neurological disorders, such as Parkin-
son’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis,
and epileptic seizures.9 Therefore, the design and development of
* Corresponding author. Tel.: +82 53 950 5588; fax: +82 53 950 6594.
E-mail address: kimhs@knu.ac.kr (H.-S. Kim).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.04.126

3532
A. Helal et al. / Tetrahedron Letters 51 (2010) 3531–3535
S
N
S
N
S
S
S
N
N
N
Z
OH
OH
HO
OH
HO
1: Z = C
2: Z = N
3
4
Figure 1. Structures of chemosensors.
1.0
the phenolic group at the position 2 is based on the fact that it
would not only produce a thiazole-based heterocyclic podand but
the phenol and the thiazole rings together can act as a binding as
well as a fluorophore resulting in an intrinsic chemosensor.
Although a number of chemosensors for different transition me-
tal ions have been described, dual-function chemosensors21 which
can be used to detect two analytes remain rare. In this paper, we
describe the design and the development of a novel bisthiazole-
based dual-function fluorescent chemosensor in aq DMSO (1/9, v/
v), buffered at pH 7.4, with phenolic substituents at the position
2 of the thiazole rings for copper and zinc ions detection based
on ESIPT. It exhibits a complete quenching on the addition of a cop-
per ion and a ratiometric fluorescent response upon addition of a
zinc ion. Due to the low solubility of sensors 3 and 4 in water or
any other organic solvents we used 100% DMSO and 10% water
in DMSO system.
1.0
0.8
0-10 eq
325 nm
(a)
380 nm
0.6
0.4
0.2
0.8
0.6
0.4
0.2
0.0
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
0-10 eq
380 nm
325 nm
0.0
0.5
2.0
Mole fra1c.0tion of1C.5 u2+
350 nm
350
300
400
450
Wavelength (nm)
In order to understand the crucial role of phenol at the position
2 of the thiazole rings we prepared 4,4’-bisthiazole (3) and its iso-
meric form 2,2’-bisthiazole (4). The chemosensor 3 was obtained in
a good yield by Hantzsch condensation reaction of 2-hydrox-
ythiobenzamide with 1,4-dibromo-2,3-butanedione in refluxing
ethanol and the chemosensor 4 was synthesized in a good yield
by a reaction between dithioxamide and 2-bromo-2’-methoxyace-
tophenone in ethanol followed by deprotection of the methoxy
group with boron tribromide as shown in Scheme 1. The structures
of 3 and 4 were confirmed by 1H NMR, 13C NMR and elemental
analysis (SI).
1.0
0.8
0.6
0.4
0.2
0.0
1.0
0.8
0-10 eq
325 nm
(b)
373 nm
0.6
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
325 nm
0.0
0.5
1.0
1.5
2.0
Mole fraction of Zn2+
0-10 eq
373 nm
The initial UV–vis study of 3 was carried out in DMSO (Figs. S-1
and S-2), and the sensing property of 3 confirmed in a more phys-
iologically acceptable condition of 10% water in DMSO (1:9, v/v)
buffered by 10 mM HEPES at pH 7.4. Chemosensor 3 displayed an
350 nm
350
300
400
Wavelength (nm)
450
obvious absorption band at 325 nm (log
*
uted to a p–p transition; this is favored by the planar orientation
e = 4.1). This can be attrib-
enforced by the intramolecular hydrogen-bonding.15,22 New
Figure 2. Changes in UV–vis spectra of 3 (30 lM) upon addition of (a) Cu(ClO4)2
and (b) Zn(ClO4)2 in aq DMSO (1/9, v/v) containing HEPES buffer (10 mM, pH 7.4).
Inset: mol ratio plots of absorbance at (a) 325 and 380 nm, (b) 325 and 373 nm.
absorption bands at 380 nm (log
e = 3.0) and 373 nm (log e = 2.7)
for Cu2+ and Zn2+, respectively, increase gradually in intensity
S
S
S
O
Br
N
N
NH2
EtOH
80%
Br
+
+
O
S
3
5
OH
OH
HO
S
S
N
O
S
Br
OCH3
NH2
N
EtOH
84%
H2N
OCH3 H3CO
BBr3
S
80%
S
N
N
OH
Scheme 1. Synthesis of chemosensors 3 and 4.
HO
4

A. Helal et al. / Tetrahedron Letters 51 (2010) 3531–3535
3533
Table 1
450
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
Photophysical properties of 3 and 4 in aq DMSO (1/9, v/v)
400
Sensor
Absorption max.
nm (log
Emission
Max (nm)
Quantum
e)
yielda
(U)
0-10 eq
382 nm
350
300
250
200
150
100
50
3
325 (4.1)
380 (3.0)
373 (2.7)
365 (3.8)
354 (3.9)
365 (3.8)
382, 509
0
462
435
435
0.07
0
0.10
0.03
0.08
0.03
3 + Cu2+
3 + Zn2+
4
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
Mole fraction of Cu2+
4 + Cu2+
4 + Zn2+
435
a
Quantum yields were obtained using quinine sulfate in 0.5 M H2SO4 as a
0-10 eq
509 nm
standard.
1.0
Host, Na+, K+, Ni2, Co2+,
Ag+, Pb2+, Cd2+, Ca2+
0
400
450
500
550
600
0.8
0.6
0.4
0.2
0.0
Wavelength (nm)
Hg2+
Cu2+
Figure 4. Changes in fluorescence spectra of 3 (30 lM) upon addition of Cu(ClO4)2
in aq DMSO (1/9, v/v) containing HEPES buffer (10 mM, pH 7.4) (kex = 350 nm).
Inset: mol ratio plot of emission at 382 nm.
1000
Zn2+
1.0
0-10 eq
462 nm
0.8
462 nm
0.6
0.4
0.2
800
0.0
Fe2+
-0.2
-0.4
-0.6
-0.8
382 nm
-1.0
0.0
0.5
1.5
2.0
Mole fra1c.0tion of Zn2+
600
400
200
0
300
350
400
450
Wavelength (nm)
0-10 eq
382 nm
Figure 3. UV–vis spectra of 3 (30 lM) with various cations (10 equiv) in aq DMSO
(1/9, v/v) containing HEPES buffer (10 mM, pH 7.4).
while one at 325 nm decreases synchronously with an isosbestic
point at 350 nm as shown in Figure 2a and b (also see Table 1).
The ratios of increase and decrease in absorption at 325 nm and
380 nm (or 373 nm) are linear up to 1 equiv of metal ion as dem-
onstrated by Figure 2a and b (insets). These observations confirm
the formation of an 1:1 complex in both cases.
421 nm
400
450
500
550
600
Wavelength (nm)
Figure 5. Changes in fluorescence spectra of 3 (30 lM) upon addition of Zn(ClO4)2
in aq DMSO (1/9, v/v) containing HEPES buffer (10 mM, pH 7.4) (kex = 350 nm).
The absorption spectrum of 3 was also measured in the pres-
Inset: mol ratio plots of emission at 382 nm and 462 nm (kex = 350 nm).
ence of transition metal ions and other ions such as Fe2+, Cd2+
,
Co2+, Ni2+, Ca2+, Cu2+, Zn2+, Hg2+, Pb2+, Ag+, Na+ and K+. Large red
shifts in absorption spectra were observed after addition of Cu2+
and Zn2+ ions (Fig. 3) with the development of a very faint yellow
Like other benzothiazole derivatives,11,12 3 contains an intramo-
lecular hydrogen bond between the phenolic O–H and the nitrogen
of the thiazole ring that undergoes ESIPT and yields a normal emis-
color with Cu2+
.
S
S
S
S
S
S
M(ClO4)2
N
H
N
H
N
N
H
N
N
M2+
H
O
O
O
O
O
O
3-M2+ complex
3: Enol
3: Keto
3-Cu2+: λmax = 380 nm, λem = 0 nm
3-Zn2+: λmax = 462 nm
λmax = 325 nm
λem = 509 nm
λmax = 325 nm
λem = 382 nm
S
S
S
N
S
N
N
H
N
H
x
O
O
OH
HO
4
λem = 435 nm
Scheme 2. Inhibition of ESIPT of 3 on coordination with metal ion and absence of ESIPT in 4.

3534
A. Helal et al. / Tetrahedron Letters 51 (2010) 3531–3535
sion at 382 nm and a tautomer emission at 509 nm from the proton
transfer tautomer (Scheme 2).23–25 Coordination 3 to the paramag-
netic Cu2+ disrupts the ESIPT and completely quenches the fluores-
cence emission (Fig. 4). The quenching as a result of the addition of
Cu2+ suggests that an excitation energy or charge transfer may
have occurred from 3 to the open-shell d-orbitals of Cu2+ exhibiting
a very fast and efficient nonradiative decay of the excited states of
the sensor 3.6e,26 Fluorescence titration of 3 with Cu2+ was carried
out in aq DMSO (1:9, v/v) buffered by 10 mM HEPES at pH 7.4 at a
caused a complete quenching of fluorescent emissions when
excited at 350 nm (Fig. 4). The binding mode of 3 with Cu2+ was
demonstrated to be 1:1 with a binding constant 5.3 Â 104 MÀ1 (er-
ror limit 6 10%), as evidenced by the fluorescence titration spectra
(Fig. 4, inset) and Job’s plot (Fig. S-3)
Similarly, Zn2+ has closed-shell d-orbitals so that energy or
charge transfer processes cannot take place. Thus, coordination of
Zn2+ removes the phenolic proton and disrupts the ESIPT causing
emission with a normal Stokes’ shift (Scheme 2).11,12 Fluorescence
titration of 3 with Zn2+ was carried out in aq DMSO (1:9, v/v) buf-
concentration level of 30
l
M. Addition of Cu2+ to the solution of 3
fered by 10 mM HEPES at pH 7.4 at a concentration level of 30 lM.
Addition of Zn2+ to the solution of 3 caused development of a new
peak at 462 nm, while the peak at 382 nm gradually diminished
with an isoemission point at 421 nm (Fig. 5). The fluorescence
titration spectra (Fig. 5, inset) and the Job’s plot of 3 with Zn2+ indi-
cated the formation of an 1:1 complex (Fig. S-4). From fluorescence
titration the binding constant of 3 with Zn2+ was calculated to be
1.8 Â 104 MÀ1 (error limit 6 10%).
1000
800
Zn2+
The fluorescence selectivity and tolerance of 3 for Cu2+ and Zn2+
over other metal cations were investigated by adding 10 equiv of
600
different metal cations to the 30 lM solutions of 3. In the case of
Host, Na+, K+, Ag+,
400
Cu2+, the molecular fluorescence was completely quenched to a
minimum level. No other metal ions produced such a complete
quenching though some paramagnetic ions such as Fe2+, Co2+ and
Ni2+ produced little to partial quenching. The binding constants
Pb2+, Cd2+, Hg2+,
Ca2+
Co2+
Fe2+
Ni2+
200
0
of Fe2+, Co2+ and Ni2+ are 7.5 Â 102, 1.1 Â 102 and 1.3 Â 102 MÀ1
,
Cu2+
respectively, as obtained from fluorescence titration curves in Fig-
ures S-5, S-6, and S-7. In the case of Zn2+, there occurred a ratio-
400
450
500
550
600
metric change, and
a new peak arose at 462 nm. Such a
Wave length (nm)
ratiometric change was absent in other metal ions (Fig. 6).
In addition, as illustrated in Figure S-8, no metal ions show any
Figure 6. Fluorescence spectra of 3 (30 lM) with various cations (10 equiv) in aq
DMSO (1:9, v/v) containing HEPES buffer (10 mM, pH 7.4) (kex = 350 nm).
interference to the sensing of Cu2+ by 3, while the ratiometric sens-
1.0
(a)
(b)
325 nm
0.8
380 nm
354 nm
0.6
365 nm
0.4
365 nm
373 nm
0.2
0.0
300
350
400
450
300
350
400
450
1000
900
800
700
600
500
400
300
200
100
0
462 nm
(d)
(c)
382 nm
435 nm
435 nm
509 nm
400
450
500
550
600
400
450
500
550
600
Wavelength (nm)
Figure 7. UV–vis spectra of 3( ) and 4( ) (a) itself, (b) in presence of 10 equiv of Cu(ClO4)2
(
) and Zn(ClO4)2
(
) in aq DMSO (1/9, v/v) containing HEPES buffer
(10 mM, pH 7.4). Fluorescence spectra of 3( ) and 4( ) (c) itself, (d) in presence of 10 equiv of Cu(ClO4)2
buffer (10 mM, pH 7.4) (kex = 350 nm).
(
) and Zn(ClO4)2 ( ) in aq DMSO (1/9, v/v) containing HEPES

A. Helal et al. / Tetrahedron Letters 51 (2010) 3531–3535
3535
ing of Zn2+ is not interfered by other cations except Cu2+ (Fig. S-9).
The quantum yield ( ) calculated for 3 was 0.07 while that of
3-Zn2+ complex was 0.1. We found that the detection limit of 3
for Cu2+ and Zn2+ were 40 and 60
M, respectively. The photophys-
Gornitzka, H.; Vendier, L.; Pitie, M.; Meunier, B. Chem. Eur. J. 2008, 14, 682; (c)
Lee, J. C.; Gray, H. B.; Winkler, J. R. J. Am. Chem. Soc. 2008, 130, 6898.
6. (a) Kim, H. J.; Hong, J.; Hong, A.; Ham, S.; Lee, J. H.; Kim, J. S. Org. Lett. 2008, 10,
1963; (b) Zheng, Y.; Cao, X.; Orbulescu, J.; Konka, V.; Andreopoulos, F. M.;
Pham, S. M.; Leblanc, R. M. Anal. Chem. 2003, 75, 1706; (c) Gunnlaugsson, T.;
Leonard, J. P.; Murray, N. S. Org. Lett. 2004, 6, 1557; (d) Kumar, S.; Kaur, N.
Supramol. Chem. 2006, 18, 137; (e) Jung, H. S.; Kwon, P. S.; Lee, J. W.; Kim, J.;
Hong, C. S.; Kim, J. W.; Yan, S.; Lee, J. Y.; Lee, J. H.; Joo, T.; Kim, J. S. J. Am. Chem.
Soc. 2009, 131, 2008; (f) Dhir, A.; Bhalla, V.; Kumar, M. Tetrahedron Lett. 2008,
49, 4227; (g) Kim, H. J.; Park, S. Y.; Yoon, S.; Kim, J. S. Tetrahedron 2008, 64,
1294; (h) Kim, H. J.; Bok, J. H.; Vicens, J.; Suh, I.-H.; Ko, J.; Kim, J. S. Tetrahedron
Lett. 2005, 46, 8765; (i) Sheng, R.; Wang, P.; Gao, Y.; Wu, Y.; Liu, W.; Ma, J.; Li,
H.; Wu, S. Org. Lett. 2008, 10, 5015.
7. de Silva, J. J. R. F.; Williams, R. J. P. Zinc: Lewis acid catalysis and regulation. In The
Biological Chemistry of Elements: The Inorganic Chemistry of Life, 2nd ed.; Oxford
UP: New York, 2001.
8. Beyersmann, D.; Haase, H. Biometals 2001, 14, 331.
9. (a) Cuajungco, M. P.; Lees, G. J. Brain Res. 1997, 23, 219; (b) Takeda, A. Biometals
2001, 14, 343.
10. (a) Mikata, Y.; Yamanaka, A.; Yamashita, A.; Yano, S. Inorg. Chem. 2008, 47,
7295; (b) Hirano, T.; Kikuchi, K.; Urano, Y.; Nagano, T. J. Am. Chem. Soc. 2002,
124, 6555; (c) Gee, K. R.; Zhou, Z. L.; Qian, W. J.; Kennedy, R. J. Am. Chem. Soc.
2002, 124, 776; (d) Lim, N. C.; Bruckner, C. Chem. Commun. 2004, 1094; (e)
Komatsu, K.; Urano, Y.; Kojima, H.; Nagano, T. J. Am. Chem. Soc. 2007, 129,
13447; (f) Hanaoka, K.; Kikuchi, K.; Kojima, H.; Urano, Y.; Nagano, T. J. Am.
Chem. Soc. 2004, 126, 12470; (g) Taki, M.; Watanabe, Y.; Yukio, Y. Tetrahedron
Lett. 2009, 50, 1345; (h) Van Dongen, E.; Dekkers, L. M.; Spijker, K.; Meijer, E.
W.; Klomp, L. W. J.; Merk, M. J. Am. Chem. Soc. 2006, 128, 10754; (i) Bozym, R.
A.; Thompson, R. B.; Stoddard, A. K.; Fierke, C. A. ACS Chem. Biol. 2006, 1, 103; (j)
Evers, T. H.; Appelhof, M. A. M.; de Graaf-Heuvelmans, P.; Meijer, E. W.; Merk,
M. J. Mol. Biol. 2007, 374, 411; (k) Evers, T. H.; Appelhof, M. A. M.; Meijer, E. W.;
Merk, M. Protein Eng. Des. Sel. 2008, 21, 529.
11. Henary, M. M.; Fahrni, C. J. J. Phys. Chem. A 2002, 106, 5210.
12. (a) Taki, M.; Wolford, J. L.; O’Halloran, T. V. J. Am. Chem. Soc. 2004, 126, 712; (b)
Henary, M. M.; Wu, Y. G.; Fahrni, C. J. Chem. Eur. J. 2004, 10, 3015.
13. (a) Zheng, Y.; Gattás-Asfura, K. M.; Konka, V.; Leblanc, R. M. Chem. Commun.
2002, 2350; (b) Yao, J.; Dou, W.; Qin, W.; Liu, W. Inorg. Chem. Commun. 2009,
12, 116; (c) Sheng, R.; Wang, P.; Liu, W.; Wu, X.; Wu, S. Sens. Actuator, B 2008,
128, 507.
U
l
ical properties of sensors 3 and 4 are summarized in Table 1.
Due to magnetic-silent nature,27 originating from the d10 elec-
tronic configuration of Zn2+ and paramagnetic property of Cu2+
,
the NMR study for complexation with 3 was not possible. In order
to study the binding mode we prepared the complex of 3 with Cu2+
and Zn2+ in DMSO and characterized by HR-FAB Mass (Figs. S-10
and S-11). The HR mass spectra of both 3-Cu2+ and 3-Zn2+ show
an 1:1 stoichiometry with the molecular ion peaks at m/z
413.9554 and 415.0321, respectively.
To understand the crucial role of the position of phenol on the thi-
azole ring in 3 we also prepared 4. As shown in Figure 7a and b, unlike
3, in the case of 4 there is a little blue shift of 11 nm in absorbance on
the addition of Cu2+ while there are no absorption spectral changes
upon addition of Zn2+. In the case of fluorescence spectrum there is
an emission peak at 435 nm (Fig. 7c) due to intramolecular charge
transfer (ICT) between the phenol and thiazole moiety (Table 1).28
But ESIPT is not possible due to the absence of conjugation between
the nitrogen of the thiazole and O–H of the phenolic ring as shown in
Scheme 2. Thus the binding of
4
with Cu2+ is very weak
(Ka = 4.2 Â 102 MÀ1, Fig. S-12) which results in partial quenching of
the emission peak of 4 (Fig. 7d). But there is no ratiometric change
(Fig. 7d) on addition of Zn2+ as ESIPT is absent in 4.
In conclusion, we have prepared bisthiazole-based dual-func-
tion fluorescence chemosensors for Cu2+ and Zn2+ ions based on
ESIPT. The binding of paramagnetic open-shell d-orbital of Cu2+
produces a complete quenching of fluorescence due to the inhibi-
tion of ESIPT and charge or energy transfers between the Cu2+
and 3. While the closed-shell d-orbital of Zn2+ causes inhibition
of the ESIPT producing a ratiometric change in emission. We also
studied that the dual-function behavior is destroyed in the iso-
meric form 4 due to absence of the ESIPT.
14. Yoon, S.; Albers, A. E.; Wong, A. P.; Chang, C. J. J. Am. Chem. Soc. 2005, 127,
16030.
15. Helal, A.; Thao, N. T. T.; Lee, S.; Kim, H.-S. J. Inclusion Phenom. Macrocycl. Chem.
2010, 66, 87.
16. Helal, A.; Kim, H.-S. Tetrahedron Lett. 2009, 50, 5510.
17. (a) Krämer, R. Angew. Chem., Int. Ed. 1998, 37, 772; (b) Xiang, Y.; Tong, A.; Jin, P.;
Ju, Y. Org. Lett. 2006, 8, 2863; (c) Chen, X.; Li, Z.; Xiang, Y.; Tong, A. Tetrahedron
Lett. 2008, 49, 4697.
18. (a) Kim, H.-S.; Koh, Y. K.; Choi, J. H. J. Heterocycl. Chem. 1998, 35, 177; (b) Kim,
H.-S.; Park, H. J.; Oh, H. J.; Koh, Y. K.; Choi, J. H.; Lee, D. H.; Cha, G. S.; Nam, H.
Anal. Chem. 2000, 72, 4683; (c) Kariuki, B. M.; Lee, S.-O.; Harris, K. D. M.; Kim,
H.-S.; Do, K.-S.; Kim, K.-I. Cryst. Growth. Des. 2002, 2, 309; (d) Kim, H.-S.; Do, K.
S.; Kim, K. S.; Shim, J. H.; Cha, G. S.; Nam, H. Bull. Korean Chem. Soc. 2004, 25,
1465.
Acknowledgment
This work was supported by the Kyungpook National University
Research Fund, 2009.
19. Kwon, O. S.; Kim, H.-S. Supramol. Chem. 2007, 19, 277.
20. Lee, S. H.; Helal, A.; Kim, H.-S. Bull. Korean Chem. Soc. 2010, 31, 615.
21. (a) Collado, D.; Perez-Inestrosa, E.; Suau, R.; Desvergne, J.-P.; Bouas-Laurent, H.
Org. Lett. 2002, 4, 855; (b) Mello, J. V.; Finney, N. S. Angew. Chem., Int. Ed. 2001,
40, 1536; (c) El-Safty, S. A.; Ismail, A. A.; Matsunaga, H.; Hanaoka, T.; Mizukami,
F. Adv. Funct. Mater. 2008, 18, 1485.
22. Keck, J.; Kramer, H. E. A.; Port, H.; Hirsch, T.; Fischer, P.; Rytz, G. J. Phys. Chem.
1996, 100, 14468.
23. (a) Tsai, H.-H. G.; Sun, H.-L. S.; Tan, C.-J. J. Phys. Chem. A. 2010, 114, 4065; (b)
Das, K.; Sarkar, N.; Majumdar, D.; Bhattacharyya, K. Chem. Phys. Lett. 1992, 198,
443.
24. Mosquera, M.; Penedo, J. C.; Rios Rodriguez, M. C.; Rodriguez-Prieto, F. J. Phys.
Chem. 1996, 100, 5398.
25. (a) Han, D. Y.; Kim, J. M.; Kim, J.; Jung, H. S.; Lee, Y. H.; Zhang, J. F.; Kim, J. S.
Tetrahedron Lett. 2010, 51, 1947; (b) Santra, S.; Krishnamoorthy, G.; Dogra, S. K.
J. Phys. Chem. A. 2000, 104, 476.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.04.126.
References and notes
1. (a) de Silva, A. P.; Fox, D. B.; Huxley, A. J. M.; Moody, T. S. Coord. Chem. Rev.
2000, 205, 41; (b) Prodi, L.; Bolletta, F.; Montalti, M.; Zaccheroni, N. Coord.
Chem. Rev. 2000, 205, 59; (c) Amendola, V.; Fabbrizzi, L.; Licchelli, M.; Mangano,
C.; Pallavicini, P.; Parodi, L.; Poggi, A. Coord. Chem. Rev. 2000, 192, 649; (d) de
Silva, A. P.; Fox, D. B.; Huxley, A. J. M.; McClenaghan, N. D.; Roiron, J. Coord.
Chem. Rev. 1999, 186, 297.
2. (a) Kawanishi, Y.; Kikuchi, K.; Takakusa, H.; Mizukami, S.; Urano, Y.; Higuchi, T.;
Nagano, T. Angew. Chem., Int. Ed. 2000, 39, 3438; (b) Deo, S.; Godwin, H. A. J. Am.
Chem. Soc. 2000, 122, 174; (c) de Silva, A. P.; Eilers, J.; Zlokarnik, G. Proc. Natl.
Acad. Sci. U.S.A. 1999, 96, 8336.
26. (a) Ressalan, S.; Iyer, C. S. P. J. Lumin. 2005, 111, 121; (b) Choi, M.-Y.; Chan, M.
C.-W.; Zhang, S.; Cheung, K.-K.; Che, C.-M.; Wong, K.-Y. Organometallics 1999,
18, 2074; (c) Villata, L. S.; Wolcan, E.; Feliz, M. R.; Capparelli, A. L. J. Phys. Chem.
A 1999, 103, 5661.
3. Tak, W. T.; Yoon, S. C. KSN 2001, 20, 863.
27. (a) Xue, L.; Wang, H. –H.; Wang, X. –J.; Jiang, H. Inorg. Chem. 2008, 47, 4310; (b)
Lim, N. C.; Freake, H. C.; Bruckner, C. Chem. Eur. J. 2005, 11, 38.
28. (a) Wong, W.-Y.; Choi, K.-H.; Lu, G.-L. Organometallics 2002, 21, 4475; (b)
Politis, J. K.; Curtis, M. D.; Gonzalez, L.; Martin, D. C.; He, Y.; Kanicki, J. Chem.
Mater. 1998, 10, 1713; (c) Park, J.-W.; Lee, J.-H.; Ko, S.; Kim, T.-W.; Uemura, T.;
Chujo, Y. Synth. Met. 2001, 121, 1689.
4. (a) Barceloux, D. G. J. Toxicol. Clin. Toxicol. 1999, 37, 217; (b) Mathie, A.; Sutton,
G. L.; Clarke, C. E.; Veale, E. L. Pharmacol. Ther. 2006, 111, 567; (c) Kim, B.-E.;
Nevitt, T.; Thiele, D. J. Nat. Chem. Biol. 2008, 4, 176.
5. (a) Mare, S.; Penugonda, S.; Robinson, S. M.; Dohgu, S.; Banks, W. A.; Ercal, N.
Peptides 2007, 28, 1424; (b) Deraeve, C.; Boldron, C.; Maraval, A.; Mazarguil, H.;