New Strategies for the Synthesis of Complex Molecular Knots

Abstract

Knots and entanglements are a ubiquitous feature of life on the macroscale, where thousands of years of innovation have led to a huge variety of knots for specific and precise purposes, in addition to featuring in exquisite and intricate artistry. However, it is only in recent years that synthetic methods to access molecular knots have allowed for a start to their systematic exploration on the nanoscale. We have only scratched the surface of investigating potential functions and applications of knots on the molecular level, hindered significantly by the synthetic effort required to realise their synthesis. Here we demonstrate new strategies for accessing complex molecular entanglements, such as Vernier template synthesis, and the social self-sorting of ligand components, facilitating access to the most complex synthetic molecular composite knots to date. Chapter One introduces the most common synthetic techniques for accessing molecular knots and describes the emerging properties and functions of entangled structures. Chapter Two details an investigation into the effects of the nature and length of ligand linker units on the properties of the resulting molecular overhand knots, and subsequently presents a metallopeptide overhand knot incorporating a beta-hairpin turn motif. Chapter Three demonstrates the use of coordinative mismatch between ligand groups and lanthanide ions in the synthesis of 6- and 12-crossing molecular composite knots by a Vernier template approach. Chapter Four describes the entropically-driven social self-sorting behaviour of ligands of different topicity in the synthesis of prime and composite knots, allowing for the synthesis of a molecular square knot of notably low symmetry. This thesis is presented in journal format. Chapter One has been submitted to a peer-reviewed journal and is under review, and is presented as submitted. Chapter Four has been prepared as a manuscript intended for publication in a peer-reviewed journal and is presented as such. Chapter Two and Chapter Three have been published as peer-reviewed articles and have been edited only to ensure consistency within this thesis. The author’s contribution to each project is detailed at the beginning of each chapter.

Date of Award	31 Dec 2022
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David August (Supervisor) & David Leigh (Supervisor)