Topological Properties of Molecular Knots

Abstract

At the macroscopic level, knots play a critical role in modern society such as in manufacturing tools, securing ropes in sailing and sewing to fabricate clothing. At the nanoscale, access to molecular knots has been restricted because of the paucity of synthetic approaches available and it has only been thirty years ago or so that the preparation of the first artificial knot was achieved. As a consequence of this, investigation of the properties and prospective applications of knots in areas such as catalysis, materials and nanotherapeutics is nascent. The research presented in this thesis examines the topological properties of molecular knots through the exploration of novel synthetic methods to generate them, including the social self-sorting of different ligand building blocks, the use of the 'sergeants-and-soldiers' effect as a valuable strategy to influence topological chirality and the kinetic resolution of racemic entanglements with an enzyme. Chapter One introduces the field of chemical topology and topological chirality in knot theory, with an emphasis on the properties of molecular knots and applications derived from the topological chirality of molecular knots. Synthetic methods for preparing molecular trefoil knots are also discussed. Chapter Two demonstrates the use of entropically-driven social self-sorting of ligands of different topicity and stereochemistry in the synthesis of molecular prime and composite knots. Chapter Three considers the employment of the 'sergeants-and-soldiers' effect as an important synthetic strategy to control the higher-order chirality expression of molecular trefoil knots. Chapter Four details the synthesis towards topologically chiral knot enantiomers without any Euclidean point chirality via kinetic resolution using an enzyme. This aims to illustrate that chiral information can be transferred from asymmetric catalysts to topologically chiral objects as a potential new method to access chiral knots. Chapter One and Chapter Four have been written as standard chapters for this thesis. Chapter Two has been published as a peer-reviewed article and has been edited only to ensure consistency within this thesis. Chapter Three has been prepared as a manuscript intended for publication in a peer-reviewed journal and is presented as such. The author's contribution to each project is described at the start of each chapter.

Date of Award	1 Aug 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Leigh (Supervisor), Daniel Tetlow (Supervisor) & Michael Greaney (Supervisor)