The Use of Coordination Chemistry Principles to Control Aggregation Processes of Metal Ions

Abstract

The research presented in this thesis is based on the use coordination chemistry principles to control aggregation process of metal ions. Two important areas, which are currently being intensely researched, were chosen. Firstly, controlled aggregation of paramagnetic metal ions to produce cooperatively coupled molecule-based magnets was studied. In Chapter 3, the potential ways of producing single-molecule magnets (SMMs) using polyols as ligands and manganese and iron ions as the paramagnetic centers were investigated. SMMs are molecules which can store magnetic information, which requires both uniaxial anisotropy and non-zero overall spin. In contrast to most Mn and Fe clusters reported in the literature, it was found that the polyols tend to favor the formation of regular polyhedral arrangements of the metal ions. In Chapter 4 one polyol was chosen in order to survey the properties of a family of lanthanide chain compounds. Here the aim was to discover whether single-chain magnets, SCMs, based on 4f metals could be produced. In order to produce the chains, benzoate was employed to provide bridges. The 4f metal ions were chosen because of their inherent spins and anisotropies. As is becoming increasingly clear from the literature, DyIII seems to be the most promising choice for attaining exotic magnetic properties. The second area of study chosen aimed to investigate the utility of using the sort of small ligand molecules usually employed in constructing coordination compounds to mimic biomineralization processes. Biominerals are minerals utilized by biological systems to fulfill a variety of functions, and thus can be described as functional materials. Their specific shapes, phases and functions result in the majority of cases through the interaction of complicated, templating biomolecules, such as polysaccharides or proteins, with the growing surfaces of the minerals. Most research aiming to reproduce the fascinating shapes and properties of such materials in vitro uses correspondingly complicated templating molecules and systems, such as block copolymers, Langmuir-Blodgett films and inverse micelles. Previous research in our group using a simple polycarboxylate demonstrated that highly complex calcium carbonate structure could be produced such as micro-trumpets constructed from bundles of high-aspect ratio nanocrystallites. In Chapter 5 the formation of these structures was investigated further as well as the influence of some rigid polycarboxylates on calcium carbonate structures. In all cases, these additives appear to stabilize an initial phase of amorphous calcium carbonate which then evolves into one of the three crystalline phases of calcium carbonate in a range of topologies.