Preparing multimetallic architectures to control the behaviour of multiple excited states

Thesis

Multimetallic lanthanide complexes offer properties not afforded by their monometallic analogues e.g. multimodal imaging agents, or qubit gates. Exploiting these properties offers new opportunities in bio-medical imaging, luminescent sensors, and quantum information science.

The preparation of multimetallic lanthanide complexes, with long-term solution stability, remains challenging. The chemical similarity of the lanthanide series precludes chemoselective syntheses. The lanthanide contraction remains the most significant physical difference between the lanthanide ions; size-selective chelators have been reported in the literature. Where multimetallic complexes have been prepared, the inherent lability of most lanthanide-chelator bonds results in a ‘scrambling’ of ions in solution. The use of kinetically inert substituted DO3A derivatives can afford access to multimetallic lanthanide complexes with long-term solution stability.

Chapter 1 provides background information on general lanthanide chemistry and describes the current literature on multimetallic lanthanide complexes.

Chapter 2 describes the preparation of dicopper(II) and multimetallic copper(II)-zinc(II) complexes of a bis-cyclen ligand, and the EPR study of their magnetic properties. These complexes act as model systems for analogous lanthanide complexes.

Chapter 3 describes the preparation of multimetallic lanthanide complexes from a ligand containing two kinetically inert chelators, derived from DO3A. Bis-europium(III) and bis-terbium(III) complexes are prepared, and the hydrolysis of a pendant acetyl ester allows for comparison of phenolate-bridged and non-bridged species, investigating the effects of intermetallic communication. The multimetallic europium(III)-terbium(III) and lutetium(III)-gadolinium(III) complexes are investigated for their luminescence and magnetic properties respectively.

Chapter 4 describes the preparation of a kinetically inert lanthanide chelators, derived from DO3A, with a pendant salicylate motif. Self-assembly of the lanthanide(III) complexes thereof with lanthanide acetylacetonates enables access to multimetallic complexes. The luminescence properties and energy transfer mechanics are investigated for the europium(III) and terbium(III) derivatives.

Chapter 5 describes the preparation of tetranuclear europium(III) and lutetium(III) complexes of 5-Me-HXTA, a lanthanide chelator, and a novel benzophenone-octaacetic acid derivative. The photophysics of these complexes are explored. Preparation of larger architectures with different ratios of lanthanide(III) ion and a novel benzophenone-octaacetic acid derivative is explored.

Chapter 6 contains a summary of the conclusions of this thesis.

Chapter 7 contains the experimental procedures and relevant characterisation data to support structural determination are appended in chapter 8.

Authors: Gray, CRA

• DOI: 10.5287/ora-9rpmyz4jq
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English