dC(100.7 MHz, CDCl3) 31.07, 35.89, 48.52, 125.08, 126.63, 127.25,
127.68, 128.04, 128.96, 129.07, 129.17, 129.37, 131.80, 133.08, 133.16,
167.85; FAB-MS, m/z 321[M 2 PF6]+; Anal. Calc. for C20H21N2SPF6: C,
51.50; H, 4.54; N, 6.01. Found: C, 51.66; H, 4.53; N, 5.98%.
‡ The NH resonances were observed at d 9.22–9.85 as a broad signal in d6-
DMSO.
§ The result of the titration by adding H2PO42 did not fit to curve based on
a 1+1 host–guest stoichiometry complex, which may be due to a phosphate–
phosphate dimerization.7d,10
¶ The Ka values were estimated by three individual fluorescent intensity
titrations: lmax(ex) = 270 nm, lmax(em) = 336 nm in MeCN at 25 °C. The
estimated error for the titration with (BuO)2P(O)O2 is < 3%.
∑ The response was too low to determine the Ka value.
1 J. March, Advanced Organic Chemistry, John Wiley & Sons, New York,
1985, p. 360.
2 J. J. Donleavy, J. Am. Chem. Soc., 1936, 58, 1004; B. T. Dewey and
R. B. Sperry, J. Am. Chem. Soc., 1939, 61, 3251.
Fig. 2 Fluorescent intensity at 336 nm of 1 (20 mM) in MeCN at 25 °C
excited at 270 nm as a function of anion concentration: (5) NBu4OAc, (2)
NEt4OP(O)(OBu)2, (D) NBu4Cl.
3 Supramolecular Chemistry of Anions, ed. A. Bianchi, K. Bowman-
James and E. García-España, Wiley-VCH, New York, 1997.
4 For recent examples of anion receptors with thiourea units, see: S.
Nishizawa, H. Kaneda, T. Uchida and N. Teramae, J. Chem. Soc.,
Perkin Trans. 2, 1998, 2325; Y. Tobe, S. Sasaki, M. Mizuno and K.
Naemura, Chem. Lett., 1998, 835; H. Boerrigter, L. Grave, J. W. M.
Nissink, L. A. J. Chrisstoffels, J. H. van der Maas, W. Verboom, F. de
Jong and D. N. Reinhoudt, J. Org. Chem., 1998, 63, 4174; T. Shioya, S.
Nishizawa and N. Teramae, J. Am. Chem. Soc., 1998, 120, 11 534; H.
Xie, S. Yi and S. Wu, J. Chem. Soc., Perkin Trans. 2, 1999, 2751.
5 W.-S. Yeo and J.-I. Hong, Tetrahedron Lett., 1998, 39, 3769.
6 W.-S. Yeo and J.-I. Hong, Tetrahedron Lett., 1998, 39, 8137.
7 (a) A. W. Czanik, Acc. Chem. Res., 1994, 27, 302; (b) A. P. de Silva,
H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M. Huxley, C. P. McCoy,
J. T. Rademacher and T. E. Rice, Chem. Rev., 1997, 87, 1515; (c) P. D.
Beer, Acc. Chem. Res., 1998, 31, 71; For recent topics, see: (d) H.
Miyaji, P. Anzenbacher Jr, J. L. Sessler, E. R. Bleasdale and P. A. Gale,
Chem. Commun., 1999, 1723; (e) P. D. Beer, V. Timoshenko, M.
Maestri, P. Passaniti and V. Balzani, Chem. Commun., 1999, 1755; (f)
S. Nishizawa, Y. Kato and N. Teramae, J. Am. Chem. Soc., 1999, 121,
9463; (g) C. B. Black, B. Andrioletti, A. C. Try, C. Ruiperez and J. L.
Sessler, J. Am. Chem. Soc., 1999, 121, 10 438; (h) H. Xie, S. Yi, X. Yang
and S. Wu, New J. Chem., 1999, 1105.
discernible binding towards oxo-anions. Taken together, it
could allow us to analyze AcO2 quantitatively9 using an easy-
to-detect fluorescent signal response. This would be most
welcome to applications involving medical diagnostics.
As a control experiment, the interaction of AcO2 with
2-methylnaphthalene was investigated in the fluorescent spectra
for which no change was observed. This insight supports the
argument that the fluorescent enhancement of 1 induced by
anions could be based on the significant change on the
photoinduced charge transfer characteristics in system 1 where
the anion binding event decreases the interaction between the
naphthalene and thiouronium moieties.
We conclude that system 1 represents a simple, easy-to-make
and hitherto unexplored class of luminescent chemosensors of
anions. Owing to the unique sensing properties based on the
naphthalene–thiouronium conjugate, the development of highly
functional derivatives will represent an important synthetic
challenge. Indeed, we are currently preparing more elaborate
systems incorporating binaphthalene units.
This work is partly supported by a TORAY Award in
Synthetic Organic Chemistry, Japan.
8 K. A. Conners, in Binding Constants, The Measurement of Molecular
Complex Stability, Wiley, New York, 1987, pp. 24–28
9 For a review on receptors for carboxylates and other organic anions, see:
C. Seel, A. Galán and J. de Mendoza, Top. Curr. Chem., 1995, 175,
102.
Notes and references
† dH(400 MHz, CDCl3, TMS) 3.07 (s, 3H), 4.32 (s, 2H), 4.69 (s, 2H),
7.25–7.27 (m, 6H), 7.46–7.49 (m, 2H), 7.67 (br d, 1H), 7.76–7.80 (m, 3H);
10 V. Král, H. Furuta, K. Shreder, V. Lynch and J. L. Sessler, J. Am. Chem.
Soc., 1996, 118, 1595.
654
Chem. Commun., 2000, 653–654