Investigating Steric versus Equatorial Contributions in Lanthanide Single-Molecule Magnets

The work presented in this thesis investigates the influence of steric versus equatorial contributions on the performance of lanthanide single-molecule magnets (SMMs) by exploring alternative bulky ligand systems in lanthanide complexes, and investigating the effects on magnetic behaviour of different equatorial ligands with lesser explored lanthanide(III) ions. The first part of this thesis outlines the optimised synthesis and characterisation of useful starting materials for use in coordination reactions. The improved synthesis of bulky cyclopentadienyl ligands which were obtained as pure materials in high yields is discussed. Furthermore, an improved safe and reliable synthetic route to solvent-free salts of the tetrakis(pentafluorophenyl)borate anion is reported, as well as the implementation of this method to prepare other tetraarylborate anions. Additionally, a superior synthetic route to lanthanide triiodide salts as pyridine solvates is discussed. The second part of this thesis explores lanthanide coordination reactions with the bulky pentaphenylcyclopentadienyl ligand. Synthetic challenges that were encountered when performing transmetallation reactions are discussed. Moreover, an alternative synthetic route to coordinate the pentaphenylcyclopentadienyl ligand to a dysprosium(III) ion that exploits the basic nature of Dy{N(SiMe3)2}3 is reported. The final part of this thesis details the synthesis and solid-state characterisation of lanthanide mono-scorpionate complexes employing various equatorial solvent ligands, including the serendipitous discovery of lanthanide fluoride-bridged dimers. Magnetic susceptibility studies were performed on selected equatorial lanthanide complexes to probe their magnetic behaviour, and whilst these did not exhibit slow magnetic relaxation in zero-field, the complexes revealed frequency and temperature dependence under an applied field. Three ytterbium complexes presented Orbach and Raman relaxation, with the effective energy barriers being amongst the highest observed for applied field ytterbium SMMs. Overall, the work presented in this thesis has led to improved synthetic methods for preparing useful compounds, increased understanding of lanthanide coordination chemistry involving bulky cyclopentadienyl ligands, and has enhanced knowledge of equatorial lanthanide SMMs. Furthermore, future directions of SMM research have been revealed to ultimately assist in the realisation of SMMs in technological applications.