Russian Chemical Bulletin, International Edition, Vol. 50, No. 3, pp. 1, March, 2001 1
1066-5285/00/5003-1$25.00 ©2001 Plenum Publishing Corporation
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 386394, March, 2001.
Complex formation between azacrown derivatives
of dibenzylidenecyclopentanone and alkali-earth metal ions
À. Î. Doroshenko,
a«
À. V. Grigorovich,
a
Å. A. Posokhov,
a
V. G. Pivovarenko,
b
À. P. Demchenko,
c,d
and A. D. Sheiko
b
a
Kharkov V. N. Karazin National University,
4 pl. Svobody, 61077 Kharkov, Ukraine.
Fax: (38 057 2) 45 7130. E-mail: andrey.o.doroshenko@univer.kharkov.ua
b
Taras Shevchenko National University,
64 ul. Volodimirskaya, 02033 Kiev, Ukraine.
Fax: (38 044) 224 6166. E-mail: pvg@mail.univ.kiev.ua
c
A. V. Paladin Institute of Biochemistry,
9 ul. Leontovicha, 02030 Kiev, Ukraine
d
TUBITAK Marmara Research Center, P.O. Box 21, 41470 Gebze-Kocaeli, Turkey.
Fax: (90 262) 641 2309. E-mail: dem@rigeb.tubitak.gov.tr, adem@paladin.biochem.kiev.ua
The complex formation of 2,5-bis[4-(1,7,10,13-tetraoxa-4-azacyclopentadec-4-yl)benzyl-
idene]cyclopentanone and several model compounds, prospective metal-sensitive fluorescent
probes, with Mg
2+
, Ca
2+
, and Ba
2+
ions in acetonitrile was studied. The azacrown derivatives
of dibenzylidenecyclopentanone have two complex formation centers, azacrown cycle and
carbonyl group. The sequence of binding to these sites is different for different ions. The
efficient ejection of the Ca
2+
and Ba
2+
ions from their complexes with azacoronands was
observed in the excited state, whereas in the case of the Mg
2+
ion, this process occurred only
partially.
Key words: bis(azacrown) derivatives of dibenzylidenecyclopentanone, ketocyanine dyes,
electronic spectra, sequence of complex formation, fluorescent probes, carbonyl group, crown
ethers, Kiprianov effect.
The problem of development of ion-selective fluores-
cent sensors for medical biological research has become
urgent due to an increasing need for studying processes
related to a change in the concentration of alkali and
alkali-earth metal ions in biological objects.
1,2
Crown-
containing organic luminophores are promising in this
respect, and their spectral parameters change substan-
tially when a metal binds to the macrocycle.
35
The
related probes sensitive to the ion concentration allow
monitoring of the microparameters of a biological object
associated with the polarity of the microenvironment of
the probe and also the microelectric parameters (for
example, the surface potential of biomembranes related
to the concentration of ions in the near-surface layer).
6
Organic aminocarbonyl compounds have long ago
and widely been used as fluorescent probes. Since their
molecules contain the electron-donating (alkyl)amino
group and electron-withdrawing carbonyl group, the
electron density redistribution between these groups dur-
ing electron excitation results in a considerable increase
in the dipole moment in the S
1
state. This determines
the observed substantial solvatochromic and solvato-
fluorochromic properties
7
of similar molecules.
We assumed that symmetric dyes with two similar
interacting chromophores and two complex formation
centers can provide somewhat higher spectral sensitivity
to metal ions. According to the Kiprianov theory,
8
when
the chromophoric fragments are cleaved, the long-wave
absorption band of similar compounds is split to a
doublet, whose components are arranged at both sides
from the position of this band in the initial mono-
chromophoric compound. Binding of one ion should
decompose the symmetry of the dye molecule. Accord-
ing to the theory of interaction of chromophores, this
should result in a noticeable hypsochromic shift of the
absorption band. Symmetric bis(azacrown)ketocyanine
dyes based on dibenzylidenecyclopentanone are appro-
priate objects to check this hypothesis. The nitrogen
atoms of the azacrown fragments in these compounds
participate in conjugation with the π-electron system of
the molecule, which suggests a noticeable dependence of
the spectral parameters on the coordination of the metal
ions with the crown ether groups.
The following compounds were chosen as objects
for the study: 2,5-bis[4-(1,7,10,13-tetraoxa-4-aza-
cyclopentadec-4-yl)benzylidene]cyclopentan-1-one (1),
2-[4-(1,7,10,13-tetraoxa-4-azacyclopentadec-4-yl)ben-
zylidene]-5-(4-diethylaminobenzylidene)cyclopentan-1-
one (2), 2,5-bis[(4-dimethylamino)benzylidene]cyclo-
pentan-1-one (3), 1,5-bis(4-dimethylaminophenyl)penta-