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Molecular recognition using highly charged podands

Ng, Yiu-Fai; (1999) Molecular recognition using highly charged podands. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis describes the syntheses and host-guest properties of some anion receptors. These have been designed as mimics for the initial interactions of peptides with small molecules which mainly involves electrostatic binding. Treatment of substituted bromomethyl benzenes and naphthalenes with 1,4-diazabicyclo[2.2.2]octane (DABCO) gave a series of polycations with different substitution patterns. These patterns ensured different degrees of conformational freedom and restricted molecules were compared with non-restricted analogues. Nuclear Magnetic Resonance techniques were extensively used to investigate the behaviour of these polycations with simple anionic guests. Association constants and stoichiometries of the complexes were determined using NMR titrations and Jobs plots, respectively. Specific recognition of ferricyanide over ferrocyanide was observed with these polycations. X-ray crystal structure analysis on some of the resulting complexes revealed interesting information regarding the conformation adopted by these polycations. The crystal structure also indicated that structured water molecules were involved in cation-anion binding. The syntheses of polycationic thiols and their electrochemical behaviour attached to a gold electrode are described. Treatment of bromoundecanethiol with DABCO gave the corresponding N-mono-thioundecanyl DABCO precursor. On treatment of this precursor with substituted bromomethyl benzenes, a series of polycationic thiol derivatives was obtained. The kinetics of electrode processes were studied by cyclic voltammetry, in which the current is monitored as the potential of the electrode is changed. The redox potentials of potassium ferrocyanide and sodium bromide in phosphate buffer were examined. Such self-assembled monolayers (SAMs) are permeable to electrolytes but show some inhibition of redox processes at the electrode. Inhibition of oxidation of ferrocyanide and enhancement of oxidation of bromide were observed, the extent of these effects varying with the structure of the attached species. A model to explain these results is advanced.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Molecular recognition using highly charged podands
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10099819
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