The synthesis and properties of asymmetric organic-inorganic hybrid polyoxometalates

The development of accessible synthetic procedures in the preparation of multifunctional hybrid materials which allow fine control in the tuning of their structure and properties is an ongoing challenge. Access to asymmetrically organofunctionalised hybrid polyoxometalates (POMs) could lead to new molecular materials with multiple or modular functionality which can be tailored towards highly specific or advanced applications. Herein, an effective design strategy to the preparation of new asymmetric bi-functionalised hybrid polyoxometalates is presented and the characterisation of the structures and properties of the new multifunctional hybrid compounds is discussed. A simple, inexpensive and high-yielding one‐pot synthetic approach to the isolation of a new asymmetric hybrid POM based on the Wells–Dawson anion is presented in Chapter 3. The development of the synthetic methodology and the characterisation of the unique asymmetric structure of the hybrid molecule is described. The unique multifunctionality of the modular system, derived from the redox-active Wells-Dawson polyanion and the two, distinct appended organophosphonate moieties with contrasting physical properties, is investigated in Chapter 4. The combined metal-coordinating and self-assembling functions are effectively demonstrated by the solvent‐dependent self‐assembly into redox‐active supramolecular aggregates. The incorporation of transition metal functionality into the asymmetric hybrid POM at the appended chelating group is explored in more detail in Chapter 5 in which two synthetic approaches are presented. First, a straightforward postfunctionalisation approach of metal coordination directly to the chelating ligand is demonstrated by the coordination of a platinum(II) ion. A modified one-pot synthesis is presented as a second approach, in which a ruthenium(II) polypyridyl complex is prepared as organophosphonate ligand that can be directly grafted to the cluster anion to isolate a new asymmetric hybrid derivative. The new Pt(II) and Ru(II) functionalised asymmetric hybrid POMs are shown to exhibit rich electro- and photo-chemical properties, in addition to solvent-dependent self-assembly, and display promise in the development of new catalytically-active soft nanomaterials. The final chapter explores the introduction of further complexity into the asymmetric hybrid POM structure through the addition of a terminal functionality which enables its covalent immobilisation. A new one-pot synthesis is presented to prepare an asymmetric hybrid POM which comprises a thiol-terminated aliphatic chain moiety, and the direct grafting of the hybrid POM onto the surfaces of gold materials is demonstrated through electrochemical studies on the redox-active self-assembled layer and the characterisation of composite gold nanoparticles. This work ultimately provides an accessible modular approach that is promising for the creative design and development of new multifunctional POM-based hybrid molecules, supramolecular systems and soft‐nanomaterials