Biologically Relevant Triply- and Quadruply-Stranded Metallosupramolecular Architectures

Abstract

This thesis consists of three chapters. Chapter 1 provides a brief introduction to why better cancer treatments and new antibacterial drugs are a necessity for the future. Some of the interesting and functional metallosupramolecular architectures have been showcased and discussed.

Chapter 2 details the generation of a new family of triply-stranded dicobalt(III) helicates and mesocates, their stability under a variety of conditions and a study of their biological activity. Building upon previous work in the Crowley group, these cylinders were designed to be stable enough to withstand attack from biological nucleophiles and show activity against both Gram-positive and Gram-negative bacteria. The helicates and mesocates were observed to be stable in DMSO and D2¬O, and did not break down readily in the presence of common biological nucleophiles such as histidine and chloride. While this was a success, the cylinders showed no activity against either strain of bacteria, most likely due to the high 3+ charge on each metal centre preventing the molecule from crossing the bacterial wall. Chapter 3 discusses the progress towards synthesising low-symmetry, quadruply-stranded dipalladium(II) cages, and their ability to bind cisplatin. The basic tripyridyl ligand system, previously employed by the Crowley group, has been appended with varying lengths of terminal alkyl and polyethylene glycol (PEG) chains to create new low-symmetry ligands. The postulate surrounding this idea was for the ligands to self-organise around two palladium(II) ions such that the PEG chains will be aggregated on one side of the cage and the alkyl chains at the other. The driving force behind this was thought to be the hydrophobic effect, and so would only self-organise in polar solvents. The reason behind having low-symmetry cages was that under the right conditions, micelles would be able to form, thus forming a large robust drug delivery vector. Full self-organisation was observed for cages with both alkyl chains and PEG chains, while a seemingly statistical mixture of isomers was displayed by the cages with only alkyl chains or only PEG chains. One of the disubstituted cages was then shown to be able to bind cisplatin within the cavity. Unfortunately, time constraints meant that only preliminary studies on micelle formation were undertaken.