Synthesis towards Trefoil knots and Solomon Links of Single Handedness

Abstract

Molecular knots and links are found in circular DNA, proteins and synthetic materials. Numerous biological examples have demonstrated that topological complexity at the molecular level can have a significant effect on physical and chemical properties, such as improved strength, flexibility, stability, and dynamics. However, scientists will not be able to investigate how different topologies can play different functions in living systems until they are able to access a wide range of different types of molecular topologies. Moreover, most knots and links are topologically chiral, as the structure cannot be deformed to superimpose on its mirror image without bonds breaking or passing through each other. Molecular rigidity is not a requirment for topological enantiomers to remain distinct, which makes topological chirality distinguishable from Euclidean chirality. Thus, molecules without Euclidean chirality can still be topologically chiral. While chiral molecules are found to be fundamentally important in chemistry and nature, the role topologically chiral complexes plays remains less explored. Although this field has received increasing attention over the past few decades, only few types of knots and links have been synthesised out of over six million known prime knots. The limited access to different topologies hinders the investigation of their applications in materials, catalysis and other potential fields. Therefore, this thesis aims at developing high-efficiency syntheses of racemic and homochiral trefoil knots and Solomon links. A trimeric helicate and a 2×2 interwoven grid are ideal building blocks for constructing a trefoil knot and a Solomon link. Further incorporating stererogenic units into the ligands leads to the formation of homochiral knots and links. A Solomon link of solely topological chirality has been prepared via dynamic imine exchange. The topological chirality displayed by such molecules is also studied in this thesis.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	David Leigh (Supervisor) & Michael Greaney (Supervisor)