Anion and Cation Binding Studies of Calix[4]pyrrole Receptors, Detailed Thermodynamic Studies and Environmental Applications.

Following an introduction on the history of Supramolecular Chemistry, the nomenclature, the functionalization of the calix[4]pyrrole ligand, and the selective interaction of calix[4]pyrroles with anions in non aqueous solvents are discussed in Chapter I. The factors that control the selectivity of calixpyrrole receptors toward anions are also incorporated in this Chapter. This thesis concerns an investigation on calix[4]pyrrole derivatives which are able to discriminate between anions in solution. It also aimed to investigate the ability of sulphur containing calixpyrrole ligands to selectively interact with the Hg(II) cation. The interaction of calix[4]pyrrole ligands with ionic species in a variety of solvents (acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide and propylene carbonate) was discussed through 1H NMR, conductance, titration calorimetry and UV-Visible spectroscopy. Information regarding the sites of interaction of calixpyrrole receptors with anions and metal cations was obtained from 1H NMR. Conductance measurements were used to (i) gain semi-quantitative information about the strength of anion / cation complexation (ii) establish the composition of the complexes examined. Solubility data for calixpyrrole ligands in various organic solvents at 298.15 K were determined. These data were used to calculate the standard Gibbs energies of solution and subsequently the transfer Gibbs energies of these ligands to various solvents taking acetonitrile as a reference solvent. Titration calorimetry was used to determine the thermodynamic parameters of complexation of calix[4]pyrrole receptors in non-aqueous solvents. The affinity of the ligands for the fluoride anion relative to other anions was quantitatively evaluated through the calculation of the selectivity factors making use of stability constant data. The crucial role played by the solvent on the ability of calix[4]pyrrole derivatives to host anions is demonstrated through the thermodynamics of transfer of product and reactants from one medium to another. Finally the synthesis and extraction properties of chelating resins containing calixpyrrole derivatives as monomers as well as by anchoring sulphur containing pendent arms into a silica backbone for the efficient removal of anions (H2PO4- and H2ASO4-) and Hg(II) cation are discussed. Final conclusions and suggestions for further research in this area are given