Ion-binding properties of molecular receptors based on a thioresorcarene and calixarene platform in solution.

This thesis is concerned with an investigation of the thermodynamic parameters of complexation of calix[4]resorcarene and calix[4]arene with metal cations and with anions, aiming at the removal of polluting ions from contaminated sources (such as the re-use of processed water) and for the extraction of heavy metals from aqueous solutions. Synthesis of 5, 11, 17, 23 ethylthiomethylated calix[4]resorcarene (L2), 5, 17 ethylthiomethylated calix[4]resorcarene (L3) and 25, 27-bis[N-(2-hydroxy-1,1 bis-hydroxymethyl-ethyl)aminocarbonylmethoxy] calix[4]arene-26, 28-diol (L4) and their characterisation by different techniques such as NMR and elemental analysis was accomplished. Partition experiments were carried out to determine that L2 and L3 are predominantly in their monomeric state in the solvents in interest. NMR technique was used for the characterisation of the ligands based on calixarene and resorcarene and for the investigation of the active site of complexation between the ligand and metal cations or anions in different solvents at 298 K. From the 1H NMR in MeCN, it can be inferred that the resorcarene ligand (L2) is interacting with Hg2+, Pb2+ and Ag+ while L3 showed interaction with Hg2+. In MeOH, both L2 and L3 showed interaction with Hg2+ and Ag+. As far as L4 is concerned, it was inferred that L4 interacts with alkaline-earth metal cations, Zn2+ and Pb2+ between the cations and with fluoride and dihydrogen phosphate in acetonitrile. Conductometric titrations in solution were carried out to determine the composition of the chemical species formed. Thermodynamic parameters of complexation of L2 and L3 with the appropriate cations reveal that L2 is selective for Ag+ and L3 possesses high stability with Hg2+. X-ray crystallography of the L2-Hg2+ complex reflects the decomposition of the ligand and the formation of polymers containing mercury and sulphur chains. Thermodynamic parameters of complexation of L4 with metal cations and anions of interest reveal the following selectivity trends at 298.15 K. L4: Mg2+ > Zn2+ > Ca2+ > Sr2+ > Pb2+ > Ba2+ (MeCN) L4: F-> H2PO4- (MeCN, DMF) Finally, conclusions and suggestions for further work in the area are given