F.-Y. Wu et al. / Tetrahedron Letters 47 (2006) 8851–8854
8853
results in less than 10% fluorescence intensity changes
of 1-Pb2+ 13 Zn2+ and Cd2+ show much weaker binding
Supplementary data
.
affinity to 1. Thus the apparent fluorescence intensity
does not change much upon addition of a 100-fold
Zn2+ and Cd2+. Also, the existence of a 1000-fold of
anions such as ClÀ, BrÀ, FÀ, NO3À, ClO4À, CO23À and
SO24À does not cause any interference. The interference
of Cu2+ and Hg2+ could be eliminated by KCN in the
pretreatment of the sample.
Supplementary data associated with this article can be
References and notes
´
1. (a) Metivier, R.; Leray, I.; Valeur, B. Chem. Commun.
It has been known that Pb2+ targets both Ca2+- and
Zn2+-binding sites in vivo14 and accurate Pb2+ analysis
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Chem. Soc. 2002, 124, 6246–6247.
2. Das, A. K.; de la Guardia, M.; Cervera, M. L. Talanta
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3. (a) de Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson,
T.; Huxley, A. J. M.; McCoy, C. P.; Rademacher, J. T.;
Rice, T. E. Chem. Rev. 1997, 97, 1515–1566; (b) Valeur, B.;
Leray, I. Coord. Chem. Rev. 2000, 205, 3–40; (c) Bakirci,
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5411–5413.
is often disturbed by the presence of Cd2+, Hg2+
,
Fe2+, and Mn2+
.
Therefore, the selective sensing abil-
1b
ity of 1 for Pb2+ over other metal ions such as Ca2+
,
Cd2+, Fe2+, Hg2+, Mn2+ and Zn2+ is particularly impor-
tant. The selectivity of 1 for Pb2+ over other metal ions
was investigated by the competition experiments. Figure
2 shows the fluorescence intensity of 1 in the presence of
10-fold excess of selected metal ions. It is obvious that 1
´
4. (a) Metivier, R.; Leray, I.; Valeur, B. Chem. Eur. J. 2004,
has a highly selective response to Pb2+
.
10, 4480–4490; (b) Matsushita, M.; Meijler, M. M.;
Wirsching, P.; Lerner, R. A.; Janda, K. D. Org. Lett.
2005, 7, 4943–4946; (c) Nolan, E. M.; Lippard, S. J.
J. Mater. Chem. 2005, 15, 2778–2783; (d) Zhang, H.; Han,
L. F.; Zachariasse, K. A.; Jiang, Y. B. Org. Lett. 2005, 7,
4217–4220.
Fluorescence titrations of 1, with Mg2+, Ca2+, Zn2+
,
Cd2+, and Pb2+ in acetonitrile, cause emission increases
along with blue shifts. The selectivity of 1 for Pb2+ over
other metal ions is much better in an aqueous solution
than in an organic solvent.
5. (a) McClure, D. S. J. Chem. Phys. 1952, 20, 682–686;
(b) Koike, T.; Watanabe, T.; Aoki, S.; Kimura, E.;
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The fluorescence titration of 3 with Pb2+ was also car-
ried out. Compound 3 exhibits smaller emission in-
creases upon cation binding in pH 7.0 aqueous
solution and Job’s plot shows a 1:2 (3:Pb2+) binding
ratio. A linear relationship exists between the concentra-
tion of Pb2+ and its fluorescence intensity in the range of
7. (a) Hayashita, T.; Qing, D.; Bartsch, R. A.; Elshani, S.;
Hanesjr, R. E.; Teramae, N. Supramol. Chem. 2005, 17,
141–146; (b) Kavallieratos, K.; Rosenberg, J. M.; Chen,
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0–8.8 · 10À6 M with
a
calibration equation, I =
(M). The detection limit
2+
28.9488 + 8.2607 · 106CPb
was determined to be 6.42 · 10À7 M. The lower sensitiv-
ity was ascribed to the fewer number of binding sites.
Similar fluorescence and absorption titration experi-
ments were also performed on 2 in DMSO and acetoni-
trile. Neither spectra profile nor fluorescence intensity
change was observed in the presence of metal ions such
as Pb2+, Zn2+, and Cd2+, because 2 does not combine
with metal ions owing to the absence of binding sites.
In summary, a highly selective fluorescent sensor (1) for
lead ions in aqueous solution was developed based on
the PET mechanism. Compound 1 provides a sensitive
(a detection limit of 3.9 lg LÀ1 in water) and single
agent fluorescence method for the assay of Pb2+ in pH
7.0 aqueous solution.
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Acknowledgments
10. Hancock, R. D.; Martell, A. E. Chem. Rev. 1989, 89,
1875–1914.
Financial support from the Basic Research Program of
the KOSEF (Grant No. R02-2003-000-10055-0) and
Seoul R&BD is gratefully acknowledged. F.-Y.W.
would like to thank the Ministry of Education for the
award of the BK 21 postdoctoral fellowship and also
appreciate support from Nanchang University in China.
1
11. Compound 1: H NMR (500 MHz, acetone-d6): d 3.87 (s,
8H), 3.91 (s, 16), 7.17 (s, 2H), 7.20 (s, 2H), 7.22–7.24 (m,
8H), 7.59 (d, 8H, J = 7.8 Hz), 7.64 (s, 4H), 7.71–7.74 (m,
8H), 8.54 (d, 8H, J = 4.6 Hz), 8.60 (s, 2H); 13C NMR
(500 MHz, acetone-d6): d 55.328, 60.373, 122.341, 123.034,
123.849, 125.769, 128.100, 129.572, 129.796, 134.841,