A. Azam et al. / Tetrahedron Letters 51 (2010) 4710–4711
4711
50
40
30
20
10
0
Fig. S3) revealed that the dan-H signal shifts upfield while those
of N–CH2 protons shift downfield on the addition of Ag+ to the host
1 in CDCl3 indicating the close proximity of Ag+ to the dansyl aro-
0.04
0.02
matic framework through a plausible cation p-type interaction. It
appears that the Ag+ imparts certain rigidity to the dansyl moieties
on the glycoluril framework. Apparently, the interaction of Ag+
with the dansyl moiety decreases the rate of non-radiative deacti-
vation pathways by facilitating the twisted intra-molecular charge
transfer (TICT) process to result in the fluorescence intensity
enhancement.
0.00
-0.02
-0.04
-0.06
In conclusion, we have achieved a novel ‘turn on’ type glycolu-
ril-based fluorescence sensor for silver ions. Further work to under-
stand the exact sensing mechanism is in progress.
0
1
2
3
4
5
6
Host/Guest
Acknowledgment
400
450
500
550
600
650
S.P. thanks Council of Scientific and Industrial Research (CSIR),
India for a Senior Research Fellowship.
Wavelength (nm)
Figure 1. Fluorescence enhancement of 1 in the presence of increasing [Ag+] in
Supplementary data
acetonitrile at ambient conditions ([1] = 20
l
M, kexcitation = 350 nm). Inset of the
figure represents F ꢀF versus the mole ratio of the host-to-guest clearly showing the
0
F
stoichiometry of the complexation to be 1:1. ([1] = 20 lM, kexcitation = 350 nm).
Supplementary data (Figs. S1–S3 and calculation for equilib-
rium constant) associated with this article can be found, in the on-
80
60
References and notes
1. (a) Cram, D. J. Science 1983, 219, 1177–1183; (b)Chemosensors for Ion and
Molecule Recognition; Desvergne, J. P., Czarnik, A. W., Eds.; Kluwer Academic:
Boston, 1997.
2. Nolan, E. M.; Lippard, S. J. J. Am. Chem. Soc. 2003, 125, 14270–14271.
3. (a) Kumar, S.; Kurur, N. D.; Chawla, H. M.; Varadarajan, R. Synth. Commun. 2001,
32, 775–779; (b) Chawla, H. M.; Singh, S. P. Tetrahedron 2008, 64, 741–748; (c)
Aoki, I.; Sakaki, T.; Shinkai, S. J. Chem. Soc., Chem. Commun. 1992, 730–732.
4. (a) Smeets, J. W. H.; Sijbesma, R. P.; Niele, F. G. M.; Spek, A. L.; Smeets, W. J. J.;
Nolte, R. J. M. J. Am. Chem. Soc. 1987, 109, 928–929; (b) Day, A. I.; Arnold, A. P.;
Blanch, R. J. Molecules 2003, 8, 74–84.
40
20
0
-20
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-60
-80
-100
5. Niele, F. G. M.; Zwikker, J. W.; Nolte, R. J. M. Tetrahedron Lett. 1986, 27, 243–246.
6. Nematollahi, J.; Ketcham, R. J. Org. Chem. 1963, 28, 2378–2380.
7. Creaven, B. S.; Gallagher, J. F.; McDonagh, J. P.; McGinley, J.; Murray, B. A.;
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8. Kang, J.; Kim, J. Tetrahedron Lett. 2005, 46, 1759–1762.
9. (a) Wosnick, J. H.; Swager, T. M. Chem. Commun. 2004, 2744–2745; (b) Lee, J. Y.;
Sung, K. K.; Jung, J. H.; Kim, J. S. J. Org. Chem. 2005, 70, 1463–1466.
10. (a)Applied Fluorescence in Chemistry, Biology, and Medicine; Rettig, W., Strehmel,
B., Schrader, S., Seifert, H., Eds.; Springer: Berlin, Heidelberg, New York, 1999;
(b)Practical Fluorescence; Guilbault, G. G., Ed.; Marcel Dekker: New York, 1990.
11. Nolan, E. M.; Lippard, S. J. Chem. Rev. 2008, 108, 3443–3480. and references
therein.
Metal
Figure 2. Percent change in fluorescence intensities of 1 (20
lM) in the presence of
12. (a) Liu, L.; Zhang, G.; Xiang, J.; Zhang, D.; Zhu, D. Org. Lett. 2008, 10, 4581–4584;
(b) Que, E. L.; Domaille, D. W.; Chang, C. J. Chem. Rev. 2008, 108, 1517–1549; (c)
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13. Compound 1: Pale yellow solid, yield: 70%, mp 260–262 °C; UV (kmax, CH3CN):
256, 350 nm. IR (KBr pellet, cmꢀ1): 1575, 1366, 1310, 1184, 1133, 1061. 1H
NMR (300 MHz, CDCl3, d in ppm): 8.56 (4H, d, dan-H), 8.55 (4H, d, dan-H), 7.97
(4H, d, dan-H), 7.60 and 7.45 (8H, t, dan-H), 7.18 (4H, d, dan-H), 7.16-6.94 (m,
10H, Ph-H), 6.09 (s, 4H, Ar-H), 5.39 (d, 4H, ArCH2Ar), 3.72 (d, 4H, ArCH2Ar), 2.85
(s, 24H, N(CH3)2). 13C NMR (75 MHz, CDCl3, d in ppm): 156.7, 151.7, 145.3,
133.9, 132.6, 131.0, 129.8, 129.6, 129.3, 122.8, 119.6, 115.8, 99.9, 84.7, 45.4,
38.2, 29.7; HRMS (ESI-TOF) m/z: calcd 1495.3900, found 1495.3552 [M++1]; 1a:
light brown solid, yield: 80%, mp 222–225 °C; UV (kmax, CH3CN): 274 nm. IR
(KBr pellet, cmꢀ1): 1596, 1461.6, 1377.9, 1261.8, 1192.9, 1091.1; 1H NMR
(300 MHz, CDCl3, d in ppm): 7.68 (8H, d, tosyl-H), 7.25 (8H, d, tosyl-H), 7.06–
6.89 (m, 10H, Ph-H), 6.62 (s, 4H, Ar-H), 5.19 (d, 4H, ArCH2Ar), 3.59 (d, 4H,
ArCH2Ar), 2.34 (s, 12H, CH3); HRMS (ESI-TOF) m/z: calcd 1179.3212, found
1179.3646 [M+].
67 M of various metal ions in acetonitrile (perchlorate salts are used).
l
concentration of Cu2+, Hg2+, and Pb2+ led to the quenching of fluo-
rescence intensity of 1 (Fig. 2). Control experiments with dansyl
chloride revealed that severe quenching of 1 in the presence of
Cu2+ was due to the heavy metal effect through collisional
quenching.14
0ꢀF
A plot of F
versus the mole ratio of [1]-to-[Ag+] revealed that
F
they interact in a 1:1 stoichiometric manner (where F0 and F are
the fluorescence intensities in the absence and the presence of
[Ag+], respectively (inset of Fig. 1)) with an equilibrium constant
of 224( 15) Mꢀ1 (for 1 þ Agþ ꢀ 1 ꢁ Agþ) (calculations are provided
in Supplementary data). Reference compound 1a was also synthe-
sized. It was observed that there was an insignificant enhancement
in the fluorescence intensity of 1a in the presence of varying con-
centrations of Ag+ (Supplementary data, Fig. S2). Again when the
same experiments were repeated with dansyl chloride alone, a
small decrease in the fluorescence intensity was observed (data
not shown). NMR titration experiments (Supplementary data,
14. Lakowicz, J. R. Principles of Fluorescence Spectroscopy, 3rd ed.; Kluwer
Academics/Plenum: New York, 2006.
15. Acree, W. E., Jr. Absorption and Luminescence Probes. In Encyclopedia of
Analytical Chemistry: Theory and Instrumentation; Meyer, R. A., Ed.; John Wiley &
Sons, Ltd: Chichester, 2000. and references cited therein.