New hydrogen bonding motifs for anion and neutral guest complexation

Abstract

This thesis presents three different areas of anion or neutral molecule recognition chemistry. There is an extensive study of homoleptic and heteroleptic platinum(II) based receptors for anion recognition. The homoleptic receptor study revealed that urea ligands are more effective than amido-pyrrole based ligands for binding anions in DMSO solution. Also, isoquinoline based ligands form more stable complexes than pyridine based ligands and their extra rigidity preorganises the receptor for increased anion affinities. The heteroleptic receptor (trans-[Pt(isoquinoline-urea)2(pyridine)2](BF4)2) exhibited either an up-down or up-up conformation in DMSO solution and the solid state, depending on the type and concentration of anion. Two different crystal structures with sulfate revealed formation of both the conformations.
The properties of a simple benzimidazole cleft receptor for barbiturates and ureas are reported. Compared to various control analogues, the receptor binds barbital or urea in highly competitive DMSO/MeNO2 solutions. A crystal structure with barbital revealed binding through six hydrogen bonds. The synthesis of a more soluble version of the receptor was attempted. The synthesis of a neutral guest templated catenane was also attempted in an effort to expand on the simple cleft work.
Finally, a new triazole strapped calix[4]pyrrole synthesised by ‘click’ chemistry is reported. The receptor shows a high affinity for chloride and bicarbonate in MeCN and DCM solutions. It also exhibits strong lipid bilayer chloride transport properties when compared to the parent meso-octamethylcalix[4]pyrrole. A brief investigation into the use of triptycenes as potential scaffolds for appending hydrogen bond donor groups for anion recognition is also reported.

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

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