A new fluorescent as well as chromogenic chemosensor for anions based on an anthracene carbamate derivative

Article abstract of DOI:10.1016/j.tetlet.2004.06.135

A new fluorescent as well as chromogenic anion sensor, 1,8-anthradiol bis(N-phenylcarbamate) 2, was synthesized. It exhibits new selective red-shifted absorption and fluorescence bands with F^- and AcO^-, which could be attributed to the anthracene moiety directly involved in the bonding interaction with the anions.

Full text of DOI:10.1016/j.tetlet.2004.06.135

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 6493–6496
A new fluorescent as well as chromogenic chemosensor for
anions based on an anthracene carbamate derivative
Qi-Yin Chen and Chuan-Feng Chen*
Laboratory of Chemical Biology, Center for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences,
Beijing 100080, China
Received 19 April 2004; revised 21 June 2004; accepted 24 June 2004
Available online 19 July 2004
Abstract—A new fluorescent as well as chromogenic anion sensor, 1,8-anthradiol bis(N-phenylcarbamate) 2, was synthesized. It
exhibits new selective red-shifted absorption and fluorescence bands with FÀ and AcOÀ, which could be attributed to the anthracene
moiety directly involved in the bonding interaction with the anions.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Anion recognition and sensing via synthetic receptors
are of current interest in supramolecular chemistry1 be-
cause of the important roles of anions in a wide range of
chemical, biological, and environmental processes. Of
particular interest in this regard are fluorescent sensors
due to the high sensitivity and simplicity of fluores-
cence.2,3 In recent years, the development of colorimet-
ric anion sensing is also particularly challenging.4,5
synthesized as new fluorescent sensors for anions.3a Fur-
thermore, Gunnlaugsson et al. reported for the first time
the charge neutral anthracene based fluorescent PET
sensors for anions in 2001.10 Recently, Kim and Yoon
reported a fluorescent PET chemosensor for fluoride
ions based on a bis-urea anthracene derivative.3d Here,
we report a new fluorescent as well as chromogenic an-
ion sensor, 1,8-anthradiol bis(N-phenylcarbamate) 2,
which exhibits red-shifted fluorescent and absorption
bands in the presence of FÀ and AcOÀ. Although this
unique fluorescent and absorption behavior was recently
found in a naphthalene urea system used as a fluoride
selective chemosensor,3e to the best of our knowledge,
it has not been reported in the designed fluorescent
chemosensors for anions based on the anthracene.
Moreover, our system also displays a high selective rec-
ognition with FÀ and AcOÀ over other anions examined
Synthetic anion receptors6 are generally composed of
binding sites and co-valently linked signaling subunit.
Anion binding sites include not only positively charged
guanidinium or ammonium based on electrostatic inter-
actions, but also neutral H-bonding donor groups such
as (thio)ureas, calix[4]pyrroles, porphyrins, or activated
amides by formation of hydrogen bonds.7 In particular,
amide NH groups are well-known to be involved in the
anion binding of proteins8 and they have been widely
used in developing anion receptors and sensors.
À
as H2PO4À, ClÀ, BrÀ, IÀ, and HSO4
.
The chemosensor 2 was readily synthesized from the 1,8-
dimethoxylanthracene 1a.11 Thus, 1a was treated with
BBr3 in CH2Cl2 togive 1,8-anthradiol 1b, which was re-
acted with phenyl isocyanate in the presence of dibutyl
tin diacetate (DBTDA) to afford the product 2 in 81%
yield (Scheme 1).12
Since the first designed anion receptor containing an-
thracene was reported by Czarnik and co-workers9a in
1989, fluorescent chemosensors for anions based on an-
thracene derivatives have attracted considerable atten-
tion.2 In particular, anthrylpolyamines were used as
photoinduced electron transfer (PET) sensors for phos-
phate and pyrophosphate in aqueous solution.9 Some
anthracene-linked calix[4]pyrroles were designed and
As shown in Figure 1, the characteristic absorption
bands of 2 due to the anthracene moiety considerably
decrease while a new red-shifted band around 406nm
appears in the presence of fluoride ion. This indicates
the complex formation. AcOÀ induced almost same
spectral changes of 2 as FÀ did. In the case of
Keywords: Anions; Fluorescent chemosensor; Anthracene; Carbamate.
*
Corresponding author. Tel.: +86-10-62588936; fax: +86-10-
62554449; e-mail: cchen@iccas.ac.cn
0040-4039/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.06.135

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Q.-Y. Chen, C.-F. Chen / Tetrahedron Letters 45 (2004) 6493–6496
16
14
12
10
8
PhNCO, DBTDA,
Toluene, 81 %
a
f
O
O
120
80
40
0
O
O
6
NH
HN
4
OR
1a, R = Me
OR
f
a
2
0
0.2
0.4
0.6
0.8
1.0
BBr3, CH2Cl2, 84 %
2
1b, R = OH
Scheme 1. Synthesis of compound 2.
1.00
0.75
0.50
0.25
0.00
2 Only
400
450
500
550
2 + HSO-
4
Wavelength (nm)
2 + Cl-
2 + Br-
2 + I-
Figure 2. Fluorescent titrations of 2 (1lM) with Bu4N+FÀ in MeCN/
DMSO (98:2, v/v), kex =364nm. From a to f, [FÀ]: 0, 1, 2, 3, 4, 5lM;
Inset: the plot of I0/(IÀI0) versus 1/[FÀ].
2 + H2PO4-
2 + AcO-
2 + F-
18
16
a
f
14
12
10
8
f
120
80
40
0
300
350
400
450
500
6
Wavelength (nm)
4
a
2
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
2.2
1/[AcO](x106 M)
-
-
Figure 1. Absorption changes of 2 (100lM) upon the addition
of tetrabutylammonium anion salts (0.6equiv) in MeCN/DMSO
(98:2, v/v).
H2PO4À, however, only little changes in the absorption
spectrum of 2 took place. Furthermore, no obvious
spectral changes were observed even in the presence of
100equiv of ClÀ, BrÀ, IÀ, and HSO4À. It was notewor-
400
450
500
550
À
thy that FÀ, AcOÀ, and H2PO4 of 10equiv each could
Wavelength (nm)
induce significant color changes of the solutions of 2
(100lM) in MeCN/DMSO (98:2, v/v) from deep yellow
to yellow to light yellow, respectively. Meanwhile, other
Figure 3. Fluorescent titrations of 2 (1lM) with Bu4N+AcOÀ in
MeCN/DMSO (98:2, v/v), kex =364nm. From a to f, [AcOÀ]: 0, 0.5, 1,
1.5, 2, 2.5lM. Inset: the plot of I0/(IÀI0) versus 1/[AcOÀ].
anions including ClÀ, BrÀ, IÀ, and HSO4 caused no
À
color changes in the same conditions. Thus, 2 could be
considered as a potential ꢀnaked-eyeꢁ chemosensor for
FÀ, AcOÀ, and alsoH PO4
.
AcOÀ. In the cases of ClÀ, BrÀ, IÀ, and HSO4À, noobvi-
ous spectral changes of 2 were observed. Even in the
presence of large excess of the anions (up to 1000equiv
each), only very little fluorescence quenching of 2 ob-
served. Although no obvious selectivity between FÀ
and AcOÀ was found, 2 showed very high sensitivity
and selectivity toward FÀ and AcOÀ over other anions
examined. This selectivity may be due tohigh charge
density and small size of FÀ and AcOÀ, which enables
them to be strong hydrogen binding acceptor to interact
with the receptor 2.
À
2
Same tendency was observed in the fluorescence spectra
of 2. As shown in Figure 2, receptor 2 displayed a typical
anthracenic emission in the absence of fluoride ion,
which gradually decreased as the concentration of fluo-
ride ion increased. Particularly, a new red-shifted band
yielding the composite spectrum with kmax at ꢀ445nm
was observed upon addition of the fluoride. This unique
fluorescence behavior13 implied that anthracene moiety
could be directly involved in the bonding interaction
with the fluoride ion along with the formation of fluo-
rescing complex. In the case of AcOÀ, similar spectral
changes were observed (Fig. 3). However, when the con-
centration of AcOÀ increased toabout 2.5equiv, further
addition of AcOÀ induced only a nominal change in the
fluorescence intensity. From the fluorescence titration
experiments, the association constants14 for the fluoride
and acetate were calculated tobe 1.55 ·105 and
3.6·105 MÀ1, respectively.
To look into the anion binding properties of receptor 2,
NMR experiments in DMSO-d6 were performed. Figure
4 shows a partial 1H NMR spectrum of 2, each peak was
assigned according to its 1H–1H COSY spectrum. Upon
the addition of 1equiv FÀ, dramatic changes occurred in
1
the H NMR spectrum of 2. Firstly, the NH protons
broadened and shifted downfield signal to ꢀ11.2ppm.
Upon the addition of 2equiv FÀ, the NH signal was
not observed (Fig. 4c). Meanwhile, the Hh proton signal
at the 9-position of anthracene moiety shifted downfield
(Dd=+0.25ppm), which indicated that the fluoride ion
In the other anions examined, H2PO4À was found to in-
duce smaller spectral changes15 than those for FÀ and

Q.-Y. Chen, C.-F. Chen / Tetrahedron Letters 45 (2004) 6493–6496
6495
Acknowledgements
We thank the Chinese Academy of Sciences, the
National Natural Science Foundation of China and
the Ministry of Science and Technology of China (No.
2002CCA03100) for financial support.
References and notes
1. (a) Comprehensive Supramolecular Chemistry; Atwood, J.
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Figure 4. Partial 1H NMR (300MHz) of 2 (1mM) in DMSO-d6.
(a) Compound 2 only; (b) 2+1equiv of n-Bu4N+FÀ; (c) 2+2equiv of
n-Bu4N+FÀ; (d) 2+1equiv of n-Bu4N+AcOÀ. The numbering of
protons is given in Scheme 2.
3. Some fluorescent chemosensors for FÀ and AcOÀ:
(a) Miyaji, H.; Anzenbacher, P., Jr.; Sessler, J. L.;
Bleasdale, E. R.; Gale, P. A. Chem. Commun. 1999,
1723–1724; (b) Anzenbacher, P., Jr.; Jursikova, K.;
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Hg Hf
He
Hd
F-
O
AcO-
O
Hh
O
O
H
O
O
H
F-
O
AcO-
O
O
O
O
O
NH
HN
NH
HN
NH
HN
Hc
Hb
Ha
2
Scheme 2. Proposed binding mode of 2 with FÀ and AcOÀ.
has a strong hydrogen bonding interaction not only with
the protons of the amide, but also with the Hh proton
(Scheme 2). The interaction between Hh and the fluoride
ion may also be an example of Caromatic–H hydrogen
bonding. On the other hand, Hc and Hd protons at the
ortho position to carbamate group showed a significant
upfield shift (Dd=À0.95 and À0.71ppm, respectively)
upon the addition of FÀ. It implied that there is no
hydrogen bonding interaction between Hc/Hd and the
oxygen in the carbonyl groups, which would induce
the Hc/Hd proton signals to shift downfield. Moreover,
the other aromatic proton signals shifted moderate up-
field (Dd=À0.30 to À0.70ppm). These facts could be
the result of the enhanced resonance of anthracene
and phenyl electrons from anionic character of carba-
mate nitrogen and oxygen.3f In the case of the acetate,
the spectral changes of 2 and binding mode of 2 with
AcOÀ were similar to those for the fluoride, which is
consistent with the results of the above fluorescent and
chromogenic methods.
4. Suksai, C.; Tuntulani, T. Chem. Soc. Rev. 2003, 32,
192–202.
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77–99; (b) Amendola, V.; Fabbrizzi, L.; Mangano, C.;
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Commun., 2001, 2556–2557.
In summary, we have presented a new fluorescent as well
as chromogenic anion chemosensor 2, which showed
high sensitivity and selectivity toward FÀ and AcOÀ
over other anions including H2PO4À, ClÀ, BrÀ, IÀ, and
HSO4À. In particular, the appearance of new red-shifted
fluorescence and absorption bands in the presence of FÀ
and AcOÀ, which could be attributed to the anthracene
moiety directly involved in the hydrogen bonding inter-
action with the anions, providing a great advantage for
the detect of those anions.
11. Lu, L. G.; Chen, Q. Y.; Zhu, X. Z.; Chen, C. F. Synthesis
2003, 2464–2466.
12. Compound 2: 1H NMR (300MHz, DMSO-d6, ppm): d
10.62 (s, 2H, NH), 8.82 (s, 1H), 8.71 (s, 1H), 8.09 (d,
J=8.5Hz, 2H), 7.61 (dd, J=7.4, 8.5Hz, 2H), 7.45–7.50
(m, 6H), 7.29 (dd, J=7.4, 7.6Hz, 4H), 7.06 (t, J=7.4Hz,
2H); 13C NMR (75MHz, DMSO-d6, ppm): d 151.8, 146.1,

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Q.-Y. Chen, C.-F. Chen / Tetrahedron Letters 45 (2004) 6493–6496
Lee, J.; Han, K.; Yoon, I.; Chung, H.; Yoon, J. Org. Lett.
2001, 3, 3455–3457.
138.4, 132.3, 128.9, 128.8, 127.2, 126.0, 125.7, 123.1, 118.7,
118.4, 113.3; MALDI-TOF MS (m/z): 471 [M+Na]+;
Anal. Calcd for C28H20O4N2Æ1/3H2O: C, 74.00; H, 4.58;
N, 6.16. Found: C, 73.86; H, 4.51; N, 6.04.
14. (a) Schneider, H.-J.; Yatsimirsky, A. K. Principles and
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13. Similar fluorescence behavior was observed in chelatose-
lective fluorescence perturbation with Cd(II), which was
resulted from electrophilic aromatic cadmiation, see: (a)
Huston, M. E.; Akkaya, E. U.; Czarnik, A. W. J. Am.
Chem. Soc. 1990, 112, 7054–7056; (b) Choi, M.; Kim, M.;
15. Because the complex stoichiometry between
2 and
H2PO4À could not be determined, the association constant
for dihydrogen phosphate was not available.