Halogen bonding fluorescent receptors for sensing hydrosulfide and other anions

This thesis describes the preparation and study of fluorescent iodotriazole containing host molecules exploiting halogen bonding for the selective molecular recognition and sensing of hydrosulfide and other anions. Chapter One introduces the field of anion supramolecular chemistry, highlighting the areas of relevance to this thesis, including the non-covalent interaction halogen bonding (XB), and reviews artificial molecular receptors for the selective recognition and sensing of anion guest species, in particular hydrosulfide. Chapter Two describes the development of a series of halogen bonding coumarin based receptors, including acyclic, macrocyclic and mechanically interlocked systems. The synthetic procedures and characterisation of each receptor are described. The capability of each receptor to recognise anions in organic solvent media, coupled with the coumarin fluorophore's ability to relay and sense the binding event via changes in fluorescence, is explored using ¹H NMR and fluorescence emission spectroscopy titration experiments. Chapter Three builds on the results of Chapter 2, detailing the synthesis and characterisation of two generations of acyclic water-soluble halogen bonding coumarin receptors. The receptors, each employing water solubilising TEG groups, are investigated for their ability to recognise and sense hydrosulfide and other anions in pure and buffered water. Computational Density Functional Theory (DFT) and Molecular Dynamics simulations are used to corroborate the experimental anion binding observations. Chapter Four investigates the use of BODIPY as a fluorescent reporter group in anion receptor design. A variety of BODIPY-iodotriazole containing receptors are prepared, including acyclic receptors, mechanically interlocked molecules, and porphyrin-BODIPY [2]rotaxanes. The anion recognition and fluorescence emission sensing properties of each receptor are investigated in organic and organic-aqueous solvent mixtures. Chapter Five provides a summary of the main conclusions of this thesis. Chapter Six details the experimental procedures employed in this work, including synthetic protocols and characterisation data for novel compounds.