The controlled synthesis of interlocked architectures
An area of great current interest is the synthesis and characterisation of molecules possessing moving parts, with the goal that they can function as "nanoscopic machines" carrying out tasks that molecules with flxed conventional architectures cannot do. Rotaxanes and catenanes (mechanically interlocked architectures) represent one approach towards achieving these aims as their component wheels and lor threads are connected together but can still move in certain, controlled, directions. This thesis focuses on the problem that many of the reactions (clipping and capping) that lead to interlocked architectures are carried out under kinetic control and as a result if clipping or capping does not occur via an already threaded precursor, "mistakes"- non-interlocked molecules- are produced that cannot be "corrected" leading to lower yields. Chapter One gives a brief outline of the common synthetic approaches to interlocked architectures and the thermodynamically controlled routes that are now being developed to address the problems outlined above. Chapters Two and Three are concerned with probing the mechanism of hydrogen bond-assembled rotaxane formation and gaining insight into the requirements of a thermodynamically controlled synthesis of interlocked architectures. Chapter Four outlines the remarkable binding properties of the component macrocycle of a hydrogen bond-assembled catenane. Chapter Five uses the results of chapter four to synthesise a rotaxane under thermodynamic control using slippage illustrating exactly why this approach to synthesis is a poor one. Chapter Six describes the true thermodynamically controlled synthesis of hydrogen bond-assembled rotaxanes employing the results of chapter four and olefm metathesis. Chapter Seven describes an efficient synthesis of catenates using octahedral metal templates. These catenates complement structurally analogous hydrogen bond assembled catenanes as they provide a way of fixing the conformational preference of the component rings. In addition there are elements of thermodynamic control built into the synthesis.