Binding anions using simple neutral molecules

Abstract

This thesis reports a number of novel neutral, hydrogen bond donating anion receptors and describes their anion coordination properties in both the solution and solid states. A set of ten urea/thiourea linked indole/carbazole groups were found to have high affinities for a variety of oxo-anions in highly competitive DMSO solutions. Of these receptors, the diindolylurea motif was found to be excellent for the binding of dihydrogen phosphate. This group of receptors were found to form 1:1 complexes in solution with various anions but more complex 2:1 and 3:1 receptor:anion complexes were observed in the solid state. Deprotonation of the bound protonated oxo-anion was observed with these 2:1 and 3:1 complexes. The basic diindolylurea motif was then extended by the incorporation of further NH bond donor groups from amide, indole and carbazole functionalities. This group of receptors were found to form 1:1 complexes in both the solution and solid states, with the binding mode dependent of the geometry of the anion. These compounds also showed spontaneous crystallisation with sulfate in as little as 20 minutes. These receptors showed high affinities for the oxo-anions and gave the first examples of solution state deprotonation of bound protonated oxo-anions. A set of three dimensional indole-based receptors was also synthesised, utilising the TREN and pin-wheel scaffolds. These receptors contain between six and fifteen NH bond donor groups that give a range of anion binding modes, some too complex to be defined, that generally show a preference for the oxo-anions. Again, an example of deprotonation of the bound protonated oxo-anion was observed

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ORCID for Philip A. Gale: orcid.org/0000-0001-9751-4910

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