Ibbett, Ashley James; (1997) Synthesis and host-guest chemistry of organic polycations. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The field of host-guest chemistry has received much attention in recent years. The design of anion receptors is anticipated to provide materials with interesting biological applications. This thesis describes the synthesis and host-guest properties of some potential anion receptors. The synthesis of a variety of polycationic materials using simple nucleophilic substitution methodology is described. The reactions of 1,4-diazabicyclo[2.2.2]octane and related compounds with tri- and hexasubstituted benzenes is reported. These reactions give rise to a series of compounds containing three formal positive charges. A strategy employing the reaction of monocationic derivatives of 1,4-diazabicyclo[2.2.2]octane with tri- and hexasubstituted benzenes was employed in the synthesis of hexacationic materials. Characterisation and purification of the tri- and hexacationic materials is discussed. The synthesis of an optically active tricationic compound is reported. A variety of techniques have been employed in the investigation of the anion complexing properties of the polycationic materials synthesised. Specific recognition of ferricyanide over ferrocyanide was observed with one tricationic compound. A crystal structure analysis performed on the material thus formed revealed interesting information regarding the conformation adopted by the tricationic compound. Nuclear magnetic resonance techniques were extensively utilised to investigate the behaviour of the polycationic materials with simple anionic guests. NMR titration curves were analysed using non-linear regression and association constants derived. The stoichiometries of the complexes were determined using the method of continuous variation. The strength of association with anionic guests of differing charge was examined. The use of isothermal titration calorimetry in the determination of enthalpies of complexation and association constants is reported. The technique revealed aspects of complexation behaviour that could not be observed using NMR techniques. The association constants determined using calorimetric techniques differed from those obtained using NMR experiments.

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