Lin et al.
6
amides and metal complexes on nanoparticles have shown
improved sensitivity toward anions.
The pyrrole-based anion probes, developed by several
7
research groups, show excellent stability over a wide range of
pH 3-10. To raise the detection sensitivity, the pyrrole units
can be incorporated into a conjugated system for colorimetric
detection or linked to fluorophores8 such as naphthalene,
anthracene, pyrene, dansyl, fluorescein, and rhodamine that can
involve various sensing mechanisms for signal transduction. We
demonstrate herein the intrinsic type anion sensors, pyreno[2,1-
b]pyrrole (1) and 2,2-bis(pyreno[2,1-b]pyrrole) (2), which
contain the pyrrol recognition unit fused with the aromatic
fluorophore.9
7
FIGURE 1. (a) Color change induced upon addition of anion (100
+
-4
equiv as the Bu
4
N
salt) to receptor 1 (2 × 10 M in DMSO). From
-
-
-
-
-
left to right: (1) no anion, (2) F , (3) Cl , (4) Br , (5) I , (6) AcO ,
-
-
-
-
-
(7) H PO
2 4
, (8) HSO
4
, (9) ClO
4
, (10) NO
3
, and (11) SCN . (b)
Results and Discussion
-6
Absorption spectral changes of receptor 1 (5 × 10 M) in DMSO in
the presence of various anions (100 equiv).
Compounds 1 and 2 with Fluoride Ion in DMSO. The idea
to render the in-built pyrene moiety is in that the eventual charge
transfer would exhibit signal output in the visible region due to
the elongation of the π electron conjugation. We had earlier
explored that 1 and 2 are indeed highly fluorescent compounds,
having quantum yields, ΦF, of 0.95 and 0.50, respectively, in
9
EtOAc. We thus prepared a stock solution of 1 in DMSO (2
-
4
×
10 M), and carefully screened its binding ability with
(4) For reviews, see: (a) Sessler, J. L.; Camiolo, S.; Gale, P. A. Coord.
Chem. ReV. 2003, 240, 17-55. (b) V a´ zquez, M.; Fabbrizzi, L.; Taglietti,
A.; Pedrido, R. M.; Gonz a´ lez-Noya, A. M.; Bermejo, M. R. Angew. Chem.,
Int. Ed. 2004, 43, 1962-1965. (c) Bondy, C. R.; Loeb, S. J. Coord. Chem.
ReV. 2003, 240, 77-99. (d) Choi, K.; Hamilton, A. D. Coord. Chem. ReV.
2
003, 240, 101-110. (e) Kubo, Y.; Yamamoto, M.; Ikeda, M.; Takeuchi,
M.; Shinkai, S.; Yamaguchi, S.; Tamao, K. Angew. Chem., Int. Ed. 2003,
4
2, 2036-2040. For recent examples, see: (f) Kim, S. K.; Bok, J. H.;
FIGURE 2. Color change induced upon addition of anions (100 equiv
Bartsch, R. A.; Lee, J. Y.; Kim, J. S. Org. Lett. 2005, 7, 4839-4842. (g)
Koskela, S. J. M.; Fyles, T. M.; James, T. D. Chem. Commun. 2005, 945-
+
-4
as the Bu
4
N
salt) to receptor 2 (1 × 10 M in DMSO): (top series)
under irradiation with 364-nm light and (bottom series) under daylight.
947. (h) Wu, J.-S.; Zhou, J.-H.; Wang, P.-F.; Zhang, X.-H.; Wu, S.-K. Org.
-
-
-
-
From left to right: (1) no anion, (2) F , (3) Cl , (4) Br , (5) I , (6)
Lett. 2005, 7, 2133-2136. (i) Ren, J.; Zhao, X.-L.; Wang, Q.-C.; Ku, C.-
F.; Qu, D.-H.; Chang, C.-P.; Tian, H. Dyes Pigm. 2005, 64, 193-200. (j)
Cho, E. J.; Ryu, B. J.; Lee, Y. J.; Nam, K. C. Org. Lett. 2005, 7, 2607-
-
- - - -
-
AcO , (7) H
12) benzoate ion.
2 4 4 4 3
PO , (8) HSO , (9) ClO , (10) NO , (11) SCN , and
(
2
609. (k) Badugua, R.; Lakowicz, J. R.; Geddes, C. D. Sens. Actuators, B
2
005, 104, 103-110. (l) Ilioudis, C. A.; Tocher, D. A.; Steed, J. W. J. Am.
various anions (as the tetrabutylammonium salts). This system
portrayed an excellent optical response toward fluoride ion
(Figure 1a). The colorless solution of 1 turned grass-green upon
addition of F , whereas no naked-eye sensible color change
occurred upon addition of other anions, including chloride,
bromide, iodide, acetate, dihydrogen phosphate, hydrogen
Chem. Soc. 2004, 126, 12395-12402. (m) Wen, Z.-C.; Jiang, Y.-B.
Tetrahedron 2004, 60, 11109-11115. (n) Arimori, S.; Davidson, M. G.;
Fyles, T. M.; Hibbert, T. G.; James, T. D.; Kociok-Koehn, G. I. Chem.
Commun. 2004, 1640-1641. (o) Xu, G.; Tarr, M. A. Chem. Commun. 2004,
-
1
050-1051. (p) Jimenez, D.; Martinez-Manez, R.; Sancenon, F.; Soto, J.
Tetrahedron Lett. 2002, 43, 2823-2825. (q) DiCesare, N.; Lakowicz, J. R.
Anal. Biochem. 2002, 301, 111-116. (r) Aldridge, S.; Bresner, C.; Fallis,
I. A.; Coles, S. J.; Hursthouse, M. B. Chem. Commun. 2002, 740-741. (s)
Miyaji, H.; Sessler, J. L. Angew. Chem., Int. Ed. 2001, 40, 154-157.
sulfate, perchlorate, nitrate, and thiocyanate ions.
-6
The corresponding absorption spectra with a 5 × 10
M
(5) For reviews, see: (a) Best, M. D.; Tobey, S. L.; Anslyn, E. V. Coord.
solution of 1 in DMSO confirmed that only fluoride ion caused
a distinct spectral change (Figure 1b). A characteristic new band
appearing in the visible region with λmax ) 472 nm can be
Chem. ReV. 2003, 240, 3-15. (b) Llinares, J. M.; Powell, D.; Bowman-
James, K. Coord. Chem. ReV. 2003, 240, 57-75. For recent examples,
see: (c) Badugu, R.; Lakowicz, J. R.; Geddes, C. D. Sens. Actuators, B
2
005, 104, 103-110. (d) Melaimi, M.; Gabbaie, F. P. J. Am. Chem. Soc.
-
attributed to the formation of anion [1] , and the occurrence of
2
005, 127, 9680-9681. (e) Amendola, V.; Fabbrizzi, L.; Monzani, E. Chem.
-
Eur. J. 2004, 10, 76-82. (f) Badugu, R.; Lakowicz, J. R.; Geddes, C. D.
J. Fluoresc. 2004, 14, 693-703. (g) Zhang, B.-g.; Cai, P.; Duan, C.-y.;
Miao, R.; Zhu, L.-g.; Niitsu, T.; Inoue, H. Chem. Commun. 2004, 2206-
proton transfer from 1 to F is dictated by the extended
π-conjugation, resulting in visible spectral changes.
In another approach, we anticipated that bispyrenopyrrole 2
2
207. (h) Mizukami, S.; Nagano, T.; Urano, Y.; Odani, A.; Kikuchi, K. J.
-
Am. Chem. Soc. 2002, 124, 3920-3925. (i) Han, M. S.; Kim, D. H. Angew.
Chem., Int. Ed. 2002, 41, 3809-3811.
would exhibit a higher affinity toward F ion because the two
pyrrole units might participate in the cooperative hydrogen
bonding. Likewise, addition of fluoride to the DMSO solution
of 2 caused a dramatic color change from greenish yellow to
bright red, whereas other examined anions showed no apparent
(6) (a) Beer, P. D.; Cormode, D. P.; Davis, J. J. Chem. Commun. 2004,
4
14-415. (b) Labande, A.; Ruiz, J.; Astruc, D. J. Am. Chem. Soc. 2002,
1
24, 1782-1789. (c) Watanabe, S.; Sonobe, M.; Arai, M.; Tazume, Y.;
Matsuo, T.; Nakamura, T.; Yoshida, K. Chem. Commun. 2002, 2866-2867.
3538 J. Org. Chem., Vol. 72, No. 9, 2007