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New lower rim calix[4]arene derivatives containing mixed donor atoms, synthesis, characterisation and binding properties.

Hutcherson, Robert George. (1997) New lower rim calix[4]arene derivatives containing mixed donor atoms, synthesis, characterisation and binding properties. Doctoral thesis, University of Surrey (United Kingdom)..

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Novel P-tert-butylcalix[4]arene derivatives (L-3-10) containing mixed donor atoms (O, N, S) have been synthesised in a two stage reaction, the first part of which involves the preparation of L-2 using 18-crown-6 as a phase transfer catalyst and K2CO3 as a weak base. These conditions lead to the removal of two distal protons from the lower rim, allowing the 1,3-bis-niethylethylthio ether derivative (L-2) to be synthesised in a reduced reaction time with greater yield and purity than previously published. The final two protons were removed using NaH, sites to which a variety of amine, amide and thiophene moieties were introduced. This thesis reports investigations on these new compounds detailed as follows, i) 1H and 13C NMR characterisation of these derivatives. In two cases, X-ray crystallograpliic structures have been determined, showing distortions from the symmetrical cone conformation of p-tert-butylcalix[4]arene caused by steric interactions of the lower rim substituents. ii) Solubility and derived Gibbs energies of these ligands in various solvents at 298.15 K. Using acetonitrile and methanol as reference solvents, Gibbs energy of transfer are calculated. iii)The acid-base properties of ligands L-3,4,6-8 were investigated by potentiometry. Equilibrium constants for the dissociation processes reveal relative proton affinities in methanol at 298.15 K. Data of individual species present as a function of pH are presented in diagrams. iv) Conductimetric measurements. These data are used to derive the stoichiometry of metal cation complexes of L-4 in methanol. v) 1H NMR studies of the complexation of L-4 with metal cations in CD3OD at 298 K. These reveal conformational change in the macrocycle cyclic structure as the substituents' arrangements are altered to accommodate the guests cations. vi) Determination of Gibbs energy of complexation for ligand L-4 and Ag+, Pb+2, Cd2+ and Cu2+ metal cations in methanol at 298.15 K, using a competitive potentiometric method. Cation selectivities are discussed.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors :
Hutcherson, Robert George.
Date : 1997
Contributors :
Depositing User : EPrints Services
Date Deposited : 09 Nov 2017 12:11
Last Modified : 16 Mar 2018 18:53

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