Bis-crown Fluoroionophore of the Diphenylpentadienone Series
J. Phys. Chem. A, Vol. 103, No. 17, 1999 3169
The association constants were calculated to allow the
interaction strength between ligands and cations to be measured.
Evidence was given for the occurrence of three stoichiom-
etries: AM, A2M, and AM2.
Molecule II is the first probe of a series designed with the
purpose to measure cation concentration at the surface of
biological membranes. The interactions with membranes will
be the topic of further investigations, as will the behavior of
the probe in solid matrices for optode preparation.
The most stable AM complex was formed with calcium, as
42
expected for an aza-15-crown-5. In effect, the calcium ion
43
11,42
diameter (1.98 Å) closely fits the crown-ether cavity,
which
Acknowledgment. This work was financially supported by
INTAS (Project No. 96-1225). We are also indebted to Dr. J.
C. Mialocq and his team for fruitful discussions.
is 1.7-2.2 Å and its double charge increases the strength of
the interaction.
The most stable A2M complex is the barium one, whereas
this type of complex was not observed with the small ions
Supporting Information Available: Table 4 displays the
calculated molar extinction coefficients at the wavelengths used
for data fitting, for complexes AM, A2M, and AM2 formed with
each salt. This material is available free of charge via the Internet
at http://pubs.acs.org.
43
lithium and magnesium. The barium ion size (2.68 Å), which
by far exceeds that of the crown cavity, favors complexation
between the metal and two molecules of ligand whereas the
43
lithium and magnesium cations (1.36 and 1.32 Å, respectively )
only partially fill one crown-ether cavity and do not allow such
sandwich type interactions. Quite high values of the association
constants K2 were found for sodium and calcium ions, which
have intermediate diameters.
References and Notes
(
1) Prasanna de Silva, A.; Gunaratne, H. Q. N.; Gunnlaugsson, T.;
Huxley, A. J. M.; McCoy, C. P.; Rademacher, J. T.; Rice T. E. Chem. ReV.
1997, 97, 1515.
As far as the AM2 complexes are considered, it must be
emphasized that the corresponding association constants K3 are
low. Complexation is very unlikely to occur in both crowns at
the same time due to the symmetrical structure of the ligand.
In fact, when one of the crowns is complexed by a cation, its
electron-donating effect is strongly reduced. So, the electron-
withdrawing effect of the carbonyl group now mainly applies
to the second crown, which is consequently deactivated with
respect to complexation. Logically, in AM2 complexes, one
cation is accommodated by the crown while the second cation
interacts with the unsaturated ligand core.
Actually, the model used to calculate the association constants
does not make any distinction between the two sites of
interaction, crown-ether and unsaturated ligand system. How-
ever, comparing the value of the association constants obtained
for I with those obtained for II allows an estimation to be made
of the competition which takes place between the two sites of
interaction. In the case of magnesium, the association constant
K1 obtained with ligand II is only 5 times higher than constant
K′1 obtained with ligand I. Therefore, cation interaction on the
unsaturated ligand core strongly competes with complexation
on the crown ether and both phenomena are simultaneously
visible in the absorption spectra. The high affinity of magnesium
for the unsaturated system could be explained by the high charge
density of this cation. In contrast, for calcium, constant K1 is
(2) Prasanna de Silva, A.; Gunnlaugsson, T.; McCoy, C. P. J. Chem.
Educ. 1997, 74, 53.
(3) Czarnik, A. W. Fluorescent Chemosensors for Ion and Molecule
Recognition; ACS Symposium Ser. 538; American Chemical Society:
Washington, DC, 1993.
(4) Valeur, B. p 21.
(5) Rettig, W.; Lapouyade, R. In Topics in Fluorescence Spectroscopy,
Vol. 4: Probe Design and Chemical Sensing; Lakowicz J. R., Plenum
Press: New York, 1994; p 109.
(6) Gromov, S. P.; Alfimov, M. V. Russ. Chem. Bull. 1997, 46, 611.
(
7) Fabbrizzi, L.; Poggi, A. Chem. Soc. ReV. 1995, 197.
(8) Yamamoto, K.; Yumioka, H.; Okamoto, Y.; Chikamatsu, H. J.
Chem. Soc., Chem. Commun. 1987, 168.
9) L o¨ hr, H. G.; V o¨ gtle, F. Acc. Chem. Res. 1985, 18, 65.
(
(10) Herrmann, U.; T u¨ mmler, B.; Maass, G.; Koo Tze Mew, P.; V o¨ gtle,
F. Biochemistry 1984, 23, 4059.
(
11) Pedersen, C. J.; Frensdorff, H. K. Angew. Chem., Int. Ed. Engl.
972, 11, 16.
12) Lindsten, G.; Wennerstr o¨ m, O.; Thulin, B. Acta Chem. Scand. 1986,
B40, 545
1
(
(
13) Shinkai, S.; Ogawa, T.; Nakaji, T.; Manabe, O. J. Chem. Soc.,
Chem. Commun. 1980, 375.
(14) Kimura, K.; Mizutani, R.; Yokoyama, M.; Arakawa, R.; Matsuba-
yashi, G.; Okamoto, M.; Doe, H. J. Am. Chem. Soc. 1997, 119, 2062.
(15) Schmittel, M.; Ammon, H. J. Chem. Soc., Chem. Commun.1995,
6
87.
16) Das, S.; Thomas, K. G.; Thomas, K. J.; Kamat, P. V.; George, M.
V. J. Phys. Chem. 1994, 98, 9296.
17) Akkaya, E. U. In Chemosensors of Ion and Molecule Recognition,
(
(
Vol. 492; Desvergne, J. P., Czarnik, A. W., Eds.; NATO ASI Ser., Ser. C;
Kluwer Academic Publishers: Dordrecht, 1996; p 177.
1
00 times higher than constant K′1, suggesting the preferential
(
18) Kiprianov, A. I.; Nikolaenko, T. K. Ukr. Khim. Zh. 1970, 36, 813;
Chem. Abstr. 1971, 74, 55112w.
19) Kornilov, M. Yu.; Ruban, E. M. Ukr. Khim. Zh. 1969, 35, 824;
Chem. Abstr. 1970, 72, 55310t.
complexation of the crown ether. This explains that, with
calcium, the crown ether is almost totally complexed before
the interaction with the carbonyl group is observable in the
spectra.
(
(20) Eisenhart, J. M.; Ellis, A. B. J. Org. Chem. 1985, 50, 4108.
(21) De Voe, R. J.; Sahyun, M. R. V.; Schmidt, E.; Sadrai, M.; Serpone,
N.; Sharma, D. K. Can. J. Chem. 1989, 67, 1565.
22) Venkateshwarlu, G.; Subrahmanyam, B. Proc. Indian Acad. Sci.
(Chem. Sci.) 1987, 99, 419.
5
. Conclusion
(
It was shown in this work that probe II is sensitive to the
presence of cations. The spectroscopic properties of this dye
are in good agreement with the theory of interaction of
chromophores in symmetrical bis-chromophoric molecules:
upon complexation with an alkali or alkaline-earth cation, the
symmetry of crown dye II is broken resulting in substantial
changes in the absorption and emission spectra. It seems that
these variations are stronger than in the case of the squaraine
dye reported by Das16 and Akkaya although the experimental
conditions are different and therefore not comparable. The
response of compound II is useful both in absorption and
emission spectroscopy: the strong wavelength shifts observed
in the presence of cations make the dye suitable for dual-
wavelength analysis in self-calibrating measurements.
(23) Hoshi, T.; Kawashima, T.; Okubo, J.; Yamamoto, M.; Inoue, H. J.
Chem. Soc., Perkin Trans 2 1986, 1147.
(
24) Tanaka, H.; Yamada, K.; Kawazura, H. J. Chem. Soc., Perkin Trans
2
1978, 231.
(25) Doroshenko, A. O.; Grigorovich, A. V.; Posokhov, E. A.; Pivo-
varenko, V. G.; Demchenko, A. P. Submitted to publication.
(
(
(
(
26) Olomucki, M.; Le Gall, J. Y. Bull. Soc. Chim. Fr. 1976, 1467.
27) Dix, J. P.; V o¨ gtle, F. Chem. Ber. 1980, 113, 457.
28) Reynolds, G. A.; Drexhage, K. H. Opt. Commun. 1975, 13, 222.
29) Fery-Forgues, S.; Lavabre, D.; Rochal, A. New J. Chem. 1998, 22,
17
1531.
(
30) Khalaf, A. A.; Etaiw, S. H.; Issa, R. M.; El-Shafei, A. K. ReV.
Roum. Chim. 1977, 22, 1251.
(
(
31) V o¨ gtle, F. Supramolecular Chemistry; Wiley: New York, 1991.
32) Moseley, K.; Maitlis, P. M. J. Chem. Soc, Chem. Commun. 1971,
982.