Synthesis and Characterisation of Iron(III) and Manganese(III) Spin Switches

The synthesis, measurements, and applications of 33 spin labile Fe(III) and Mn(III) Schiff base complexes are reported herein. The thesis is divided into four chapters, Chapter 1 being an introduction overviewing fundamentals of bonding in Fe(III) and Mn(III), how spin state changes are induced and probed as well as a brief look at the literature and how the field has progressed over the last century since the discovery of spin crossover with a particular focus on movement toward potential applications over the last 15 years. The chapter includes an explanation of measurements used and defines parameters for certain analyses. Chapter 2 is divided in two sections which detail two distinct projects both based around Fe(III) complexes. The first project looks at a family of 10 Fe(III) complexes with structural characterisation using SCXRD. In combination with magnetic measurements, it is determined that 9 of these complexes are in the high spin state while the last is locked in the low spin state up to 300 K. Formal structure-function analysis between spin state and structural motifs is also carried out. The second project explores the potential of using Fe(III) Schiff base complexes as cheap, easily produced photosensitisers in dye sensitised solar cells. 10 Fe(III) complexes are combined with four semiconductors to explore a proof of concept. Newly discovered complexes are also structurally characterised in this section. Chapter 3 examines two smaller projects all involving Mn(III) complexes. The first details a series of Mn(III) spin labile complexes which contain a hitherto unseen allyl functional group. The complexes are characterised structurally, magnetically, and optically with some discussion on the structure-function attributes of the allyl substituent. The second project details a Mn(III) complex which shows two distinct spin states so far unseen with a ligand of the same design. Variable temperature SCXRD and formal structural analysis is described. While broadening the synthetic scope of this ligand system a number of Mn(III) complexes with unusual ligands and geometry were discovered and are reported and structurally characterised here. Chapter 4 details some discussion and concludes the work outlined in the thesis.