Towards Novel Sensitised Lanthanide Rotaxane Architectures : A Thesis for the Degree of Master's by Research

Bidder, Abigail and Evans, Nicholas (2023) Towards Novel Sensitised Lanthanide Rotaxane Architectures : A Thesis for the Degree of Master's by Research. Masters thesis, Lancaster University.

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Abstract

The overall aim of this work is to explore new lanthanide-appended supramolecular architectures and their luminescent capabilities. It will investigate various methodologies for the preparation of molecularly interlocked molecules, taking inspiration from existing literature in the field, with the end goal of analysing how different structures may affect lanthanide luminescent emission. Lanthanide emission spectra typically contain very sharp and defined bands which can change intensity dependent on factors in the cations’ immediate environment; this gives lanthanide-appended supramolecular architectures great potential for use as sensors for pH changes or ion concentration. To allow luminescence to occur in these systems, sensitising chromophores – typically conjugated π electron systems like aromatic phenyl or pyridyl functionalities – must be present and in close proximity to the lanthanide cation within the structure. These functionalities absorb energy from photons of certain wavelengths (typically UV) and the π electrons are consequently excited to a state of higher energy before the transfer of that energy to the ground state lanthanide cation via a non-radiative process. The energy transfer’s efficiency will vary proportionately with the distance from the lanthanide cation to the chromophore, which thus could allow the measurement of conformational changes within the supramolecular structure that may occur in response to changes in the molecule’s environment. One example of this would be the movement of a macrocycle from one axle ‘station’ to another as moieties are protonated or deprotonated as a result of changes in pH. It is hoped that this work will contribute to the eventual introduction of lanthanide-appended supramolecular architectures as sensors and imaging agents in a biological context, with the potential for use in medical settings alongside laboratories.