Exploring the behaviour of lanthanide-appended metallocenes and d-f hybrid complexes

• Main Author: Lim, Hyun-Min
• Format: Dissertation
• Language: English
• Published: University of Oxford 2022
• Subjects: Bioinorganic chemistry; Electrochemistry; Inorganic compounds; Luminescence; Physical inorganic chemistry; Synthesis

The lanthanides are widely used in a variety of applications ranging from the materials science of magnets to the development of imaging agents for biomedical diagnosis and drug discovery assay. These exploit the fundamental properties of the lanthanides and focus on the behaviour of lanthanide (III) species with partly filled f-orbitals. Gadolinium complexes have become the contrast agents of choice for magnetic resonance imaging, while luminescent complexes of other lanthanides (particularly europium and terbium) play a key role in display technologies and ultrasensitive bioassay. Early work on such systems focused on simple mononuclear complexes, but the last twenty-five years have witnessed rapidly increasing interest in the behaviour and exploitation of multi-nuclear and multi-metallic complexes, both f-f and d-f heterometallic systems can be prepared by using kinetically stable building blocks to access more complicated architectures. This thesis explores how d-f hybrid complexes can be prepared and how their properties can be exploited. The research targets on identifying three redox active systems which are ferrocene derivatives and bridging ligands that can incorporate d-metals such as ruthenium chromophores. Chapter 1 discusses the fundamental principles of the chemistry and photophysics of lanthanides including the sensitisation mechanisms for lanthanide luminescence and the physical and chemical properties that can be derived from spectroscopic analysis. Previously reported d-f heterometallic systems are discussed in this chapter, with a particular focus on metallocene, rhenium and ruthenium. Chapter 2 discusses the effect of direct and indirect electronic communication between ferrocene and lanthanide centres on the sensitisation of luminescence. This chapter explores studying the kinetic stability of metal centres through electrochemically induced redox cycles using CV, UV-Vis, and luminescence emission measurements. This chapter exploits earlier work on ferrocene derivatives but extends the possibilities for electron transfer and electronic communication by using bridging ligands that provide a path for exchange interactions between the two metal centres. Chapter 3 discusses d-f compatible phenanthroline ligand and explains their potential as a bridging ligand for ruthenium and osmium incorporation, as well as the observations made during the attempted synthesis of phenanthroline bridging ligand. Chapter 4 discusses the pH sensitivity of hydroxyphenacyl-DO3A and its potential as a bridging ligand for the incorporation of zirconocene chromophore. This chapter consists of an investigation in the effect of pH change on the physical properties of hydroxyphenacyl-DO3A and describes its suitability for use in biological systems and in pH sensing. Chapter 5 draws general conclusions which describe the redox activity or pH sensitivity of lanthanide complexes incorporating different ligands and their feasibility to be used in biological media, while Chapter 6 provides experimental detail.