Novel rotaxanes for the enantioselective binding of chiral anions

Gell, Charlie (2019) Novel rotaxanes for the enantioselective binding of chiral anions. PhD thesis, UNSPECIFIED.

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Abstract

This thesis reports upon investigations towards the synthesis and study of enantiopure interlocked molecules for the application of enantioselective recognition of chiral guest species. Chapter One introduces the field of enantioselective recognition of chiral guest species and the synthesis of interlocked molecules. The review focuses upon enantioselective recognition of chiral anions, before taking an overview of the strategies employed to synthesise rotaxanes. The chapter concludes with how chirality can be introduced into rotaxanes and applications where the chirality of such rotaxanes has been explored. Chapter Two charts the development and synthesis of a family of enantiopure chloride templated rotaxanes, incorporating enantiopure amino acid moieties as the chiral element. The enantioselective properties of these rotaxanes are then elucidated by NMR titrations using enantiopure chiral anions. Chapter Three details the synthesis of a racemic chloride templated chiral rotaxane and behaviour of the diastereomers formed when the templating chloride anion is replaced with various enantiopure chiral anions. The separation of the diastereomeric salts of the rotaxane is reported. Chapter Four investigates efforts towards a chiral sensing palladium (II) templated rotaxane. Both 3,5- and 2,6-substituted pyridine axle motifs are discussed. Chapter Five describes the synthesis of a hydrogen bond templated chiral rotaxane. Following observation of diastereotopic effects on the axle due to the influence of the rotationally directional macrocycle, the effect of solvent, pH and presence of alkali metal cations on this expression of chirality by the rotaxane are disclosed. Chapter Six further investigates the shuttling motion reported in Chapter Five. It commences with a short survey of developments to date regarding hydrogen bond templated rotaxanes demonstrating molecular motion and responding to changes in pH or addition of alkali metal cations. Chapter Seven details the synthetic procedures and characterisation of compounds reported in this thesis, as well as titration protocols and x-ray crystal structures.