An investigation into the molecular recognition and sensing of anions, especially of alkylcarbamates and related species

Abstract

This thesis reports the synthesis and study of the anion recognition properties of a variety of synthetic organic and inorganic receptors. A series of known anion receptors containing a common urea and varying alkyl and aryl substituents have been investigated for their ability to bind the alkylcarbamate portion of two alkylammonium-alkylcarbamate salts and the CO2 adduct of a cyclic amidine, in an investigation into novel CO2 fixation strategies. Chemical shift changes were used to observe relative binding strengths for interactions between the alkylcarbamate and the receptors in DMSO-d6. The results show that it is possible to bind the alkylcarbamate anion in the presence of the primary alkylammonium cation, when a receptor of sufficient strength is employed. The strength of this interaction was increased when 18-crown-6 was added, which acts as a receptor for the alkylammonium cation. The CO2 adduct of the cyclic amidine, (1,4,5,6, tetrahydropyrimidine) was shown to have the strongest interactions with the receptor series. Several Schiff-base and urea containing receptors have been synthesised and assessed for anion complexation properties in solution using 1H NMR in DMSO-d6 : water mixtures. These are selective for acetate, benzoate and dihydrogen phosphate over chloride and hydrogen sulfate, and exhibit a mixture of 1:1 and 2:1, (guest:host), binding stoichiometries in several cases. Zinc(II) and cobalt(II) chloride complexes of one of this series were synthesised. The cobalt(II)chloride complex was observed to be a stark colorimetric indicator for chloride and dihydrogen phosphate. A number of isophthalamide derivatives containing activated NH and / or CH protons have been synthesised and assessed for anion complexation solution using 1H NMR in DMSOd6. Their interactions with fluoride, chloride and bromide were investigated, which demonstrate a significant contribution from the activated CH protons

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ORCID for M.C. Grossel: orcid.org/0000-0001-7469-6854

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