Abstract:

Calixarenes are macrocyclic compounds composed by phenolic units, connected by methylene bridges, to form a hydrophobic cavity capable of generating inclusion complexes with a variety of molecules. Calixarenes are particularly attractive scaffolds for receptor development, through the incorporation of numerous ligands for co-operative binding of anions. Since their discovery calixarenes have been widely used in the last two decades as building blocks for the synthesis of receptors for cations and neutral molecules. The development of synthetic anion receptors has been slow in comparison to cation receptors. Anions play a number of fundamental roles in biological and chemical processes and the development of selective synthetic anion receptors is an area of current importance. Calixarenes bearing urea and thiourea moieties have also been prepared offering the advantages of increased proton acidity and additional proton interactions with the same directionality which can act co-operatively in binding an anion. On the basis of the precedent information, we have synthesized and characterized new functionalized calixarenes with thiourea in the lower rim. Also, some known molecules were incorporated as fluorophores, and their binding properties with various anions, including fluoride, chloride, acetate, among others are being investigated by fluorescent titrations, Job plot experiments and 1H NMR spectroscopy.