Exploring the effects of secondary interactions for magnetic applications : a thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry, School of Food Technology and Natural Sciences, Massey University

Abstract

The field of molecular magnetism has had a surge of interest in recent years due to the discovery of single molecule magnets (SMMs), which are species that possess magnetic properties that are entirely molecular in origin. Despite this research interest, SMMs are not yet at the stage where they can be implemented in modern technology. A key area requiring further insight is magneto-structural correlation, how the structural feature of the molecule effects the magnetic properties. In this regard, how secondary interactions can affect the magneto-structural properties of an SMM is worthy of further development in this field. Herein, trinuclear heterometallic 3d/4f complexes are reported, which provide a framework for the manipulation of secondary interactions. A series of four-coordinate Niᴵᴵ complexes provides a necessary reference, possessing an absence of controllable second sphere interactions. A series of five-coordinate Cuᴵᴵ complexes allows control of the axially bound species to effectively manipulate the secondary interactions. Our investigation into axially bound chloride, bromide, and nitrate anions are reported with the halide complexes being magnetically characterised. Two Cu₂Tb complexes possess ferromagnetic exchange between Cu and Ln ions as well as zero-field AC magnetic susceptibility, indicative of SMM behaviour. Analogous Cu₂Gd and Cu₂Er possess ferromagnetic and antiferromagnetic exchange respectively. Further analysis revealed that secondary interactions had a significant effect on the magneto-structural properties of these complexes, with the supramolecular architecture dominated by secondary interactions. Attempts to develop a series with a six-coordinate 3d ion capable of exhibiting a greater array of secondary interactions were unsuccessful, with the hydrolysis of the ligand by a MnCl₂ catalysed reaction being the net result. Finally, a tetranuclear Cu₃La complex is reported which provides an avenue for the comparison of a trinuclear and tetranuclear series