Abstract
This thesis concerns the thermodynamics of macrocycles and their metal cation complexes in non-aqueous media and these are discussed under two main headings, i) Thermodynamics of Alkali-Metal Cations and Macrocycles in Solution and in the Solid State. Thermodynamic parameters of complexation for alkali-metal cations and macrocycles (18-crown-6 and ethyl p-tert-butylcalix(6)arene hexanoate) in benzo-nitrile at 298.15 K are first reported. These data are compared with those previously reported for cryptand 222 and these cations in this solvent. A 'peak' selectivity for potassium is observed for the complexation of the calix(6)arene ester with alkali metal cations. The process is enthalpy controlled with an exothermic maximum for the potassium cation. Thermodynamic data of complexation are characterised by a lower enthalpic stability and a more favourable entropy (except for K+) than corresponding data involving cryptand 222 or indeed 18-crown-6. Standard enthalpies of solution, DeltasH0, of macrocycles and their sodium and potassium salts in benzonitrile measured calorimetrically are discussed in relation to (i) data for the uncomplexed salts and (ii) previously reported data for sodium and potassium cryptate salts in various solvents. Enthalpies of coordination, DeltacoordH0, for eighteen systems involving sodium and potassium coronates, cryptates and calix(6)arenates are derived and whenever possible these are discussed on the basis of (i) available X-ray crystallographic data and (ii) the anion effect on the coordination process. ii) Thermodynamics of Lower Rim Calix(4)arene Derivatives with the Silver Cation in Different Media at 298.15 K. The DeltasH0 values of p-tert-butyl(bis-diethylamine-bis-methysulphanyl) calix(4)arene (EATCalix4) in various solvents at 298.15 K are reported. Transfer parameters from acetonitrile to other solvents are calculated. The interaction of EATCalix4 and the silver cation was investigated by 1H NMR in deuterated acetonitrile at 298 K showing that the ligand hosts the metal cation through interaction with the different donor atoms (O, N, S). Conductimetric titrations indicate that the stoichiometry of the complex is 1:1. The thermodynamics of complexation of EATCalix4 and silver in six solvents at 298.15 K is reported. The DeltasH0 values of the free and the complex silver perchlorate salts have been also measured in various solvents and these have been combined with DeltacH0 data to derive the DeltacoordH0 of this system. A few representative examples about the use of coordination data are given. The medium effect on the complexation process is assessed in terms of DeltatG0, DeltatH0 and DeltatS0 of the reactants and the product from acetonitrile to the appropriate solvent. The relevance of analysing the solvation changes that these species undergo upon complexation is emphasised.