Discrete metal clusters for photocatalysis

"This is a PhD research project in Chemistry.
TiO2 is an effective, heterogeneous photocatalyst but its inherent insolubility places restrictions on the scope of applications it can be
used for. It is possible to sequentially build up a variety of multimetallic Ti complexes (TixOy, where x,y > 2) through controlled
hydrolysis of monometallic Ti complexes. These complexes have already been shown to be active catalysts for the ring-opening
polymerization of lactide whilst remaining tolerant to air and moisture. We now aim to expand their utility by exploring the application of
these complexes as soluble photocatalysts and discrete models of TiO2. The complexes are supported by amine bis(phenolate)
ligands which are cheap to produce and simple to modify, providing the ability to functionalise the ligand in many different ways. This
allows us to modify the (electronic) properties of the core, vary solubility or incorporate the complexes in polymeric materials. By doing
so, we will be able to apply our photocatalysts to reactions in a range of different environments, which are not accessible for TiO2.
Furthermore, TiO2 doped with a second transition metal has broad application in photocatalysis, photovoltaics and photosensors but
such species are challenging to synthesise in a controlled and predictable manner. A major advantage of the hydrolysis method, we
have developed for the synthesis of TixOy species, is the ability to adapt this flexible synthetic route to create multimetallic complexes.
This methodology allows us to create mixed-metal complexes (e.g. Mn/Ti) whilst retaining the additional benefit of the solubility (in
common solvents) afforded by the supporting ligand. Specifically, we will focus on transition metals with known application, when
doped on TiO2 surfaces, for reactions that are relevant to sustainable chemistry."

Initially the student will create several amine bis(phenol) pro-ligands using literature procedures (or minor modifications thereof). Once coordinated to Ti complexes these will allow us to examine if the modifying the ligand can allow us to alter the UV-vis absorption specra of the complexes (with the aim of creating complexes that, more efficiently, absorb light in the visible region). To synthesis the target Ti complexes the student will be following existing protocols (or minor modifications thereof) developed within the research group. The complexes will be characterised by the student using spectroscopic methods (NMR, IR, UV-vis), mass spectrometry, elemental analysis and single crystal x-ray diffraction. Once the complexes have been made we will trial these in photochemical reactions to ascertain their activity. Initially we will benchmark these against reactions where TiO2 is already a known photocatalyst. We have identified C-C bond forming reactions as a potential candidate and will follow existing literature procedures in the first instance.