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Title: Lower rim calix[4]arene derivatives and their complexes with univalent cations : solution, complexation and X-ray diffraction studies
Author: Salazar, Lupe E. Pulcha
ISNI:       0000 0001 3546 2713
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2001
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Following an introoduction on calixarene chemistry and their metal-ion complexes including some of their applications, the aims of the work are described. Thus, the first part of this thesis concerns the detemination of the standard enthalpies of solution, sH°, of new lithium and sodiimi 1:1 electrolytes based on eth p=tert-butycalix[4]arene tetraethanoate containing various anions in acetonitrile at 298.15 K. Using these data in conjunction with previously reported sH° values for the free metal-ion salts and the ligand and standard enthalpies of complexation, cH°H° of allcali-metal cations (Li+ and Na+) and the calix[4]arene ester in the same solvent, standard enthalpies of coordination, coordH° referred to the process in which the reactants and the product are in the solid stated were calculated. The anion effect on the coordination process was determined. The second part of this thesis is related to an investigation on the solution properties of pyridinocalix[4]arenes and their metal-ion complexes. Transfer Gibbs energies of geometrical isomers of pyridinocalix[4]arenes from acetonitrile to various solvents reflect that these ligands undergo selective solvation in the various solvents but these cannot be correlated with any single solvent property. The complexing ability of 5,11,17,23 - tetra - tert - butyl[25,26,27,28 - tetrakis (2-pyridyhnethyl) oxy]- calix[4]arene for metal cations was investigated by a variety of techniques. Thus 1H NMR studies were performed to obtain information about the active sites of the ligand in its interaction with metal cations. Conductance measurements were used to establish the composition of the metal-ion complexes in dipolar aprotic media. Potentiometric and calorimetric measurements were performed to derive the thermodynamics associated with the complexation process in acetonitrile and benzonitrile. Based on stability constant data, two metal-ion complexes were isolated. The crystal structure of the sodium and acetonitrile complex of 5,11,17,23- tetra- tert- butyl[25,26,27,28 - tetrakis (2-pyiidylmethyl)oxy] calix[4] arene solved by X-ray diffraction studies shows three different complexes in the lattice, two sited on a fourfold axis and a third one on a twofold axis where all ligands exhibit a 'cone' conformation and the sodium ion is encapsulated in their hydrophilic pockets with their hydrophobic cavities filled with an acetonitrile molecule. The crystal structure of the 1:1 monoacetonitrile and silver complex of the 2-pyridyl derivative with the perchlorate ion as the counter ion shows the macrocycle sited on a fourfold symmetry axis. The presence of acetonitrile in the hydrophobic cavity of the ligand is also found. The silver cation is encapsulated in the hydrophilic cavity through the ethereal oxygens and the pyridinic nitrogens. Conclusions and suggestions for furthur research in this area are given.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Calixarene; Metal-ion; Crystal structure