Abstract
This thesis is concerned with an investigation of the thermodynamic parameters of complexation of calix[4]pyrrole derivatives with anions and metal cations, as well as the use of calix[4]pyrrole oligomers and silica based materials aiming at the removal of polluting ions from aqueous solutions. The synthesis of meso-tetramethyl tetrakis-(4-phenyl methyl ester) calix[4]pyrrole, CP(I) and meso-tetramethyl tetrakis-(4-phenoxy acetone) calix[4]pyrrole, CP(II) and their characterisation by different techniques such as NMR and elemental analysis were accomplished. The second ligand was chosen to assess the effect of introducing a methylene group on the complexation process. Solubility data for calix[4]pyrrole derivatives in various 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. The 1H NMR technique was used for identifying the active sites of complexation between the ligands and ionic species in different solvents (acetonitrile, dimethyl sulfoxide) at 298 K. From the 1H NMR in deuterated dimethyl sulfoxide, it can be inferred that CP(I) is selective for the fluoride anion while in deuterated acetonitrile, this ligand shows interaction with fluoride and mercury ions. As far as CP(II) is concerned, the results showed interaction with F-, Cl-, Br- and Hg2+ . Conductance measurements were performed with the aim of i) determining the composition of the ligand-anion/cation interaction, and ii) gaining information regarding the strength of anion/cation complexation with the ligands in acetonitrile, dimethyl sulfoxide and propylene carbonate. Direct titration calorimetry was used to determine the thermodynamic parameters of complexation of calix[4]pyrrole derivatives and ions in non-aqueous media. The essential role played by the solvent was assessed through the thermodynamics of transfer of the product and reactants from one medium to another. Finally, the synthesis and extraction properties of calix[4]pyrrole oligomers and silica based materials for the removal of anions (fluoride, dihydrogen phosphate and dihydrogen arsenate) and the Hg(II) cation from aqueous solutions are discussed. Final conclusions and suggestions for further work in the area are given.