The aim of this project was to synthesise and characterise pillararenes, macrocycles comprised of 1,4-dialkoxybenzene moieties linked in the 1,5-positions by methylene bridges, and to incorporate them in a range of sensors. Pillararene-based ion-selective electrodes (ISEs) were used to detect protons, alkali metal cations and biogenic amines to investigate sensing properties resulting in the fabrication of a low pH sensor. Composite sensors incorporating 1,4-dimethoxypillararene were able to detect Na+ concentrations in the physiological range, whereas K+ concentrations were well above those encountered in vivo. The composite electrodes did not show significant differences in capacitance for biogenic amines making them suitable to detect Na+ and K+ over alkali metal ions and unaffected by the presence of biogenic amines. A novel thiolated copillar[4+1]arene was synthesised and attached to gold electrodes. It was tested against alkali metals and biogenic amines and was most selective to Li+ over other alkali metal cations. Copillar[4+1]arene-capped gold nanoparticles were synthesised and assessed for biogenic amine selectivity. Complexation occurred strongly with spermidine and spermine compared to pentylamine and putrescine. Overall, the common purpose of the research presented in this thesis was to assess the pillararene macrocycle for its selectivity of small molecules and ions, specifically alkali metals and biogenic amines of biological importance. The difference in the nature of ion selectivity by the same macrocyclic binding motif appears to be due to its arrangement and conformational freedom in the different types of electrodes. In the ISE, the crystalline macrocycle integrates with polyvinyl chloride (PVC) which makes the upper and lower rim functional groups available for complex formation. In composite sensors, the alignment of the macrocycles is very rigid making complex formation reliant on the guest fitting into the rigid macrocyclic cavity. On gold electrodes, one of the aromatic rings is involved in surface attachment with the remaining four free to change their conformations and bind guest species.
|Date of Award
|Peter Cragg (Supervisor), Bhavik Patel (Supervisor) & Ian Cooper (Supervisor)