Inorganic, organometallic and materials chemistry
My primary research activities involve the syntheses of new coordination and organometallic complexes, and determining their structure and chemical properties. The focus of much of this work is on understanding new coordination and bonding modes for main group and transition metals. As well as advances in fundamental knowledge, there are potential applications in new materials and drug discovery.
Porphyrin and corrole complexes: designing new materials
Metalloporphyrin complexes occur naturally in hemoglobin, myoglobin and cytochromes. Synthetic porphyrin complexes are used widely as catalysts, in new materials, and as potential therapeutic agents. These applications are possible because the porphyrin ligand imparts interesting and unusual properties to the chemistry of the central atom. Corroles are relatives of porphyrins but have a slightly different framework, closely related to naturally occurring vitamin B12. Our research group is the first in the world to prepare complexes containing boron coordinated to the porphyrin ligand. They are very unusual in that they contain two boron atoms coordinated in the porphyrin cavity, in contrast to almost every other porphyrin complex which contains only one coordinated atom. We have achieved similar results with diboron corroles. The boron porphyrin and corrole complexes show unexpected types of chemical reactivity resulting from the proximity of two boron atoms within a tight cavity. Other potential applications of boron porphyrins and corroles are as sugar sensors and as fluorescence sensors, which will involve studying the photophysical properties of the boron porphyrins and corroles.
Lighting up sugars: fluorescent probes for saccharides
We have developed a method of attaching a fluorescent BODIPY label directly to glucose through B-O-C links. This allows for highly targeted, sensitive, fluorescent labelling of sugars which could be applied to the detection of specific sugar disease markers on cell surfaces, the labelling of saccharide capsules coating pathogenic bacteria, and the determination of polysaccharide fine structure in biology and materials science.
New materials: molecular Penrose tiling
Like a bathroom wall, a tiled plane is covered with no gaps or overlaps. This is easy to achieve using regular tiles like triangles, squares or hexagons but impossible using only shapes with 5-fold symmetry. In the 1960s Roger Penrose approached this intriguing mathematical problem by using tiles of more than one shape, either rhombic or pentagonal, and the resulting patterns are called Penrose tilings. Similar tilings have been observed in ancient Islamic architecture. Penrose tiling on a surface has never been achieved using molecules and we are interested in pursuing this goal using 5-fold symmetric molecules as the pentagonal tiles and either metal coordination or supramolecular chemistry to control the interactions between the edges of the tiles. A range of possible “molecular tiles” have been identified based on cyclopentadienyl, expanded porphyrin, calixarene and curcurbituril motifs. This project involves synthesis of the molecular tiles and their deposition on a surface in a controlled fashion so as to design molecular materials with particular properties such as the Penrose tiling pattern.
New types of gas sensor based on semiconducting oxides
We are exploring the interaction between suitably formulated metal complexes and semiconducting oxides. The aim is to create states on the surface of the oxide whose interaction with a gas can be detected though a change in electrical conductivity of the oxide.