INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Binding and sensing of fluorescent probes by p-sulphonatocalix(8)arene.
Autor/es:
VALERIA N. SUELDO OCCELLO; GUADALUPE G. MIÑAMBRES; GRACIELA FORTUNATO; MARCIO LAZZAROTTO; ALICIA V. VEGLIA
Lugar:
Florianópolis, SC, Brazil
Reunión:
Conferencia; 10th Latin American Conference on Physical Organic Chemistry.; 2009
Institución organizadora:
Universidad Federal de Santa Catarina, Brasil
Resumen:
BINDING AND SENSING OF FLUORESCENT PROBES BY
p-SULPHONATOCALIX(8)ARENE
Valeria N. Sueldo Occelloa, Guadalupe G. Miñambresa, Graciela Fortunatob, Marcio Lazzarottoc
and Alicia V. Vegliaa
a Instituto de Investigaciones en Fisicoquímica de Córdoba (INFIQC) - Dpto. de Química Orgánica,
Facultad de Ciencia Químicas, Universidad Nacional Córdoba, Ciudad Universitaria, Córdoba,
X5000HUA, Argentina. b Área de Química Orgánica, Dpto. de Química Orgánica, Facultad de
Ingeniería Química, Universidad Nacional del Litoral, Santa Fe, S3000AOM, Argentina. c Instituto de
Química, Dpto. de Química Orgánica, Universidad Federal de Rio Grande del Sur,15003, Porto
Alegre, R.S., Brasil. e-mail: aveglia@dqo.fcq.unc.edu.ar
.
In recent years molecular containers have attracted considerable attention owing to their
potential application in catalysis, stabilization of reactive intermediates, and binding, separation, and
sensing of small molecules and ions. Among them, a system of current interest is that formed by
calixarenes (CA) as a result of their intrinsic shape, with makes them versatile receptors for neutral
and charged molecules. The CA are basket-shaped metacyclophanes synthesized by condensation
of p-alkyl-substituted phenols and formaldehyde in the presence of alkalis. Furthermore, they can be
functionalized by substitution of R by groups such as HSO3
-, increasing their water solubility.
The CA constituted by eight monomers of 4-hydroxybenzene sulphonic acid is the psulphonatocalix[
8]arene (C8S). In this report we evaluate the binding and sensor ability of C8S with
organic compounds with different electronic and structural characteristics such as the fluorescent
probes, methyl orange (MO) and 1-anilino-8-naphtalene sulphonate (ANS), and the benzoimidazolic
pesticides, benomyl (BY) and carbendazim (CZ).
The spectrophotometric and spectrofluorimetric determinations were carried out at pH= 1.00 and
25 ºC in water. The Uv-vis spectra of all substrates did not change in the presence of C8S. A similar
behaviour was observed on the fluorescence of ANS.
In the case of MO, fluorescence quenching was produced on the increase of C8S. This effect
was rationalized by Stern-Volmer equation given an association constant (KA / M-1) with a value of
(32 ± 4) 102, indicating the formation of a 1:1 complex less fluorescent than the free substrate.
A similar tendency was found for BY at concentrations of C8S higher than 8 _M. However, in
this case, fluorescence enhancement was produced when C8S concentration changes increased
from 0 to 8 _M. In this region, from the exponential fitting of the data of fluorescence vs [C8S] it was
possible determine a value of KA = (4 ± 2) 104 M-1 and a fluorescence quantum yield ratio between
the complex and the free substrate (öc/öf) of 3.1 ± 0.7, indicating the ability of C8S as nanosensor. In
addition, the 1:1 stoichiometry was confirmed with a molar ratio plot. Similar results were found for
CZ.
We will discuss the differences observed on the basis of the nature of the interactions produced
between each substrates and C8S and we will compare them with previous results with C6S.