Jozef Hodyl PhD Thesis - Theses - Flinders University

ABSTRACTImmobilisation of functional entities, such as, enzymes, onto solid supports, as ameans of facilitating their removal from the surrounding environment andsubsequent regeneration has been in practice for many decades. This work focuseson the immobilisation and analysis of three-walled (pendant armed), cyclen basedreceptor complexes immobilised onto a silica surface for the purpose of sequesteringaromatic anions from aqueous solution: Si-GPS-[Cd(Trac)](ClO 4 ) 2 , Si-GPS-[Cd(DiPTrac)](ClO 4 ) 2 , and Si-GPS-[Cd(TriPTrac)](ClO 4 ) 2 were the immobilisedreceptors used.Initially, synthesis of a three-walled model receptor, [Cd(TracHP12)](ClO 4 ) 2 , thatis not bound to silica yet mimics the properties of the silica anchored receptorcomplexes with a hydroxypropyl pendant arm was effected. Aromatic anion bindingconstant measurements were made on the model receptor using 1 H NMR monitoredtitrations in DMSO-d 6 which showed that, in comparison to the first generation fourwalledreceptors, the removal of one of the pendant arms did not affect the bindingcapability of the receptor's cavity significantly. It was shown that the bindingstrength correlated well with the pK a of the particular anion with, for example, p-hydroxybenzoate > m-hydroxybenzoate > o-hydroxybenzoate. The precursor to thisreceptor was then immobilised onto a silica surface and subjected to metal ion uptakestudies to gauge its coordination properties with a number of divalent metal(II) ions:Cd(II), Pb(II), Zn(II), Cu(II) and Ca(II). The three Cd(II) coordinated receptorcomplexes mentioned above were then subjected to inclusion studies with a numberof aromatic anions in aqueous conditions whereupon a reversal of the previouslymentioned trend, i.e. o-hydroxybenzoate > m-hydroxybenzoate > p-hydroxybenzoatewas observed. This indicated that the presence of water in the system changes theii