Magnetic Ionic Liquids: Design, Properties and Application

Abstract

Magnetic ionic liquids are a class of ionic liquids which are intrinsically paramagnetic due to the incorporation of transition metals, lanthanides, or actinides in either the anionic or cationic structure. Such incorporation leads to interesting magnetic, optical, and catalytic properties, depending on the metal incorporated. Owing to their intrinsic paramagnetic behaviour, manipulation of the transport properties of magnetic ionic liquids can be achieved by means of external stimuli. This research has aimed to design and synthesise novel magnetic ionic liquids and to gain a more in-depth understanding of their physical properties, to explore the stimuli-responsive nature of magnetic ionic liquids and to look into the possibility of designing magnetic ionic liquids for particular applications. This took the form of three main chapters. In Chapter 2, our interest lies in developing magnetic ionic liquids containing transition metals. The ability of a cobalt salt in an ionic liquid reservoir to change coordination upon cooling was taken as a case study to explore the stimuli-responsive nature of transition-metal based ionic liquids. By using dielectric measurements, we were able to investigate the effects of temperature and, importantly, pressure on the coordination behaviour of a cobalt thiocyanate-based system over very wide frequency, temperature and pressure ranges, meaning the dynamic behaviour could be monitored over the liquid, supercooled and glassy region. In Chapter 3, we looked at the design of a series of lanthanide(III)-containing ionic complexes which were dimeric in nature. Starting from the design of dimeric solids, we demonstrate that by tuning of anion and cation structures we can lower the melting points below room temperature, while maintaining the dimeric structure. Magnetic measurements were able to establish the spin-spin interactions of the neighbouring lanthanide(III) ions in the liquid state at low temperatures and matched the interactions of the analogous crystalline solid compounds. viii Finally, in Chapter 4, we combine the ability of a functionalised ionic liquid to selectively coordinate to a metal cation in solution and the magnetic properties of an ionic liquid, which is expected to lead to easier separation of the organic phase from an aqueous phase. In this context, we explore the development of a task-specific magnetic ionic liquid for the extraction of uranyl nitrate. We show that by incorporating specific features into the cation and anion structures, we can impart properties such as, hydrophobicity, extracting ability and magnetic functionality to the ionic liquid.

Date of Award	2019
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Peter Nockemann (Supervisor), Johan Jacquemin (Supervisor) & Haresh Manyar (Supervisor)