Mechanically interlocked and redox switchable molecules at surfaces

Abstract

This thesis explores the surface assembly of mechanically interlocked molecular architectures at gold surfaces for potential applications in molecular switches, anion sensing and stimuli (redox and optical) responsive molecular films. Chapter One introduces the field of mechanically interlocked molecules focusing on rotaxane and catenane surface assemblies in the form of single molecule thick self-assembled monolayers. A review of the surface-attached characteristics of mechanically interlocked molecules is given before exploring specific anion template directed strategies for their construction. The potential to incorporate both redox-active and optically-active functional groups within these mechanically interlocked molecules is also discussed. Chapter Two provides the experimental details and procedures employed in this thesis to characterise the molecular systems under investigation. Chapter Three introduces several surface characterisation techniques such as; ellipsometry, contact angle, X-ray reflectivity and X-ray photoelectron spectroscopy, with a particular focus of applying these tools to probe the surface co-conformation of switchable and interlocked molecules at surfaces. Electroanalytical techniques such as cyclic voltammetry, chronoamperometry and electrical impedance spectroscopy are also introduced. Chapter Four details the surface assembly of a series of ferrocene containing anion templated catenane self-assembled monolayers on gold. Detailed electrochemical and angle resolved X- ray photoelectron spectroscopy characterisation elucidates the co-conformation upon surface attachment. Chapter Five details the anion templated surface assembly of a redox-active rotaxane self- assembled monolayer on gold. Subsequent electroanalysis and X-ray photoelectron spectroscopy characterisation confirms the structural integrity of the film and a possible co- conformation at the surface is discussed. Chapter Six describes efforts towards constructing optically responsive hybrid d-f lanthanide containing mechanically interlocked molecules. Initial work focuses on switching characteristics of a redox switchable antennae and its ability to modulate the luminescence of a series of lanthanide complexes in solution. Subsequent surface attachment of the lanthanide complexes in the form of emissive self-assembled monolayers is also investigated.