CONICET | Buscador de Institutos y Recursos Humanos

The final objective of our studies is to develop new and enhanced analytical methods based on supramolecular interactions for analytes of biological implications in human health. Macrocyclic compounds are building blocks in supramolecular systems, acting as receptors of inorganic and organic analytes. The interactions involved are of different kind and magnitude as van der Walls forces, hydrogen bond and electrostatic interactions. Calixarenes (CA), thiacalixarenes (TCA) and resorcarenes (RA) are macrocyclic compounds of phenol from the family of cyclophanes. These macrocycles have different solubility and polyprotic acid-base properties in aqueous or aqueous/ organic media, depending of their subtituents. These characteristics make possible the study of the same host with different electronic charge establishing different interactions with others compounds depending on pH. In this report we present the results obtained in our lab for the determinations of the pKai (i = 1; 2; n) of p-t-butylcalix[4]arene, p-t-butylcalix[6]arene, p-t-butylthiacalix[4]arene and n-butyl[4]resorcarene in the appropriate aqueous medium of solubilization (75% ethanol:water for CA and TCA; or 2% methanol:water for RA) by potentiometric and spectrophotometric methods. Also we discuss the ability of these macrocycles as receptor for inorganic and organic molecules. In all cases, an enhanced acidity (7-2 pKa units) was observed compared with that of the corresponding phenol monomer as in the case of p-sulphonato-calix[n]arenes in water;1 but some particular effect with the metallic ion (Li+, Na+,K+) of the tritan base is observed, mainly in the case of CA. These findings indicate some particular interaction between the receptor and the inorganic cation that can not be explained only by the size of the ion. The ability of these macrocycles as container for organic compounds was explored in the following cases: a) n-butyl[4]resorcarene for Promecarb (pesticide), b) TCA for Cafeic Acid (natural product and dietary supplement) and c) p-sulphonato-calix[n]arene for Carbazol (contaminant) at different pH values by spectrophotometric and spectrofluorimetric methods. These results will be interpreted in base of the possible interactions produced by the electronic characteristic of the macrocycle and the analyte at the pH and the medium employed. 1 J.P. Scharff, M. Mahjoubi, New. J. Chem., 15 (1991) 883.