Abstract
This thesis consists of three chapters.
Chapter 1 introduces metallosupramolecular chemistry and the current methods used to generate metallosupramolecular architectures. The molecular recognition properties of these structures are discussed, along with their response to certain stimuli. Heterometallic architectures and their methods of synthesis are then presented. The difference in lability between platinum(II) and palladium(II) is then investigated, and the aims of the project are laid out; the first being the synthesis of a more water stable low-symmetry platinum(II)-palladium(II) heterometallic cage through a selective metallation approach, and the second the generation of a paddlewheel containing heterometallic cage by building upon the subcomponent self-assembly approach previously utilised in the Crowley group.
Chapter 2 discusses the construction of a low-symmetry heterometallic platinum(II)-palladium(II) cage using reduced-symmetry ligands appended with pyridyl and imidazole donors. By building on the imine- and hydrazone-based platinum(II)-palladium(II) heterometallic cages formed by the Crowley group using subcomponent self-assembly, the new selective metallation approach is detailed along with initial model studies. The synthetic method of generating this new low-symmetry heterometallic cage is then examined, and its’ molecular recognition and stimuli responsiveness properties are explored. The heterometallic cage showed no affinity for any of the neutral guests screened, but it did show affinity for a number of anions. A range of affinities were observed for sulfonates, organoborates and phosphates, along with differences in their host:guest ratios. The cage was shown to open upon the addition of 4-dimethylaminopyridine, and close upon the addition of either methanesulfonic acid or p-toluenesulfonic acid. Carrying out this procedure on a host-guest adduct was seen to trigger reversible uptake and release of the guest. The stability of the cage in water was also examined - it was shown to be water stable for at least three weeks.
Chapter 3 details efforts to incorporate paddlewheels into heterometallic cages. The paddlewheel motif is introduced, as well as its common uses in large metal organic polyhedra and as secondary building units in metal organic frameworks. Recent examples of M4L4 lantern-type cages formed using paddlewheels and their amenability to post-assembly modification are discussed. Model compounds and the initial covalent approach are examined, then the more promising subcomponent self-assembly approach with aldehyde appended paddlewheel complexes are explored, as well as early attempts at performing imine condensation reactions on these complexes. Methods towards the synthesis of both homo- and heterometallic cages using these aldehyde paddlewheel complexes are proposed.