Investigations of structure and magnetism in a family of dinuclear triple helicate materials

Abstract

The engineering of metallosupramolecular materials incorporating multifunctional properties has emerged as a compelling goal to synthetic chemists and materials scientists. These systems can exhibit hugely diverse structural features, and the interplay between the supramolecular structure and constituent chemical units gives rise to a broad spectrum of physical properties. These structurally diverse systems have potential uses in the broadly useful areas of catalysis, drug delivery, and molecular sensing and recognition. This thesis focuses specifically on multifunctional materials like data storage and advanced signalling components by the incorporation of the spin crossover (SCO) property into metallosupramolecular architectures. SCO compounds act as molecular switches, and the multifunctionality afforded by their differentiable and controllable high spin (HS) and low spin (LS) states allows for control over nano-scale processes. Currently, the design of metallosupramolecular architectures exhibiting targeted physical behaviours is unreliable, due not only to the difficulty in predicting the supramolecular topology, but also the complex interplay between structural features and manifest properties. In the endeavour of functional materials design, the metalloligand approach has shown promise, which allows complex architectures to be generated from relatively simple coordination complexes. By incorporating metalloligands of known physical properties into more complex materials, it is feasible to impart the properties of simple individual coordination units into a larger architecture, which further modulates the expressed properties. This project aims to develop a system of analogous dinuclear triple helicate architectures of the form [M2L3]4+ using a new semi-rigid ligand bearing two a-diimine donor groups, and investigate their physical properties – in particular spin crossover of an Fe(II) helicate in this thesis. The designed helicates bear secondary coordination sites, affording them the potential for use as metalloligands. The structural features associated with spin transition (ST), as well as the substitution of various primary metal ions are investigated in detail to assess the suitability of these units for the building of larger supramolecular architectures. To this end, a set of unconventional structural parameters has been developed to assist in the quantification of subtle structural variations in the dinuclear triple helicate archetype. The methodology applied in this project can be readily extended to the analysis of a vast range of coordination complexes, thus assisting in the investigation of microstructural variations, and assisting in the design of metallosupramolecular architectures bearing targeted properties.

Date of Award	2023
Original language	English