Dr Graeme Hogarth

Work in the Hogarth group centres on the chemistry of the transition metals. We are interested in a range of different aspects of these and tackle problems of both a fundamental and applied nature. In general we approach things from a molecular aspect and the first port of call is the synthesis of new transition metal complexes. We make extensive use of NMR spectroscopy and X-ray crystallography and encourage a hand on approach by students and post-docs. Increasingly our work also involves a significant amount of electrochemistry since we are interested in understanding and utilising electron-transfer events especially in relation to catalytic transformations. We are also interested in the design of new ligand types and using molecules as precursors to nanomaterials. Many of our projects have an end-goal in the area of catalysis, especially homogeneous catalysis and catalysis by nanoparticles. We collaborate extensively and have active research partnerships with groups at University College London, Imperial College, Lund University (Sweden), University of North Texas (USA), Jahangirnagar University (Bangladesh) and Tikrit University (Iraq).   

Clean electrocatalytic hydrogen formation: Hydrogen has the potential to provide a transportable high density form of energy storage for use as a fuel, however, current hydrogen production is unsustainable being based on fossil-fuels. Thus there is a great need to find clean and sustainable sources of hydrogen and the electrocatalytic reduction of protons by cheap and sustainable base-metal catalysts is an attractive proposition. We take our inspiration from ancient enzymes named hydrogenases which are able to catalyse the reversible reduction of protons and oxidation of hydrogen (an impotent transformation for fuel cells). Importantly they use the sustainable metals iron and nickel. We have prepared a large number of biomimetics of one of these enzymes and have shown with extensive electrochemical studies (with Katherine Holt at UCL) that small changes to the structure of these can have a significant impact on their catalytic activity. We are currently focused mainly on the inclusion of redox-active ligands into these biomimetics in order to control electron-transfer and also are exploring the role of small iron clusters as potential proton reduction catalysts.

Selected references: (i) Hydrogenase biomimetics: Fe2(CO)4(m-dppf)(m-pdt) both a proton-reduction and hydrogen oxidation catalyst, S. Ghosh, G. Hogarth, N. Hollingsworth, K.B. Holt, S.E. Kabir and B.E. Sanchez, Chem. Commun., 2014, 50, 945-947. (ii) Fluorinated models of the iron-only hydrogenase: an electrochemical study of the influence of an electron-withdrawing bridge on the proton reduction overpotential and catalyst stability, F. Ridley, S. Ghosh, G. Hogarth, N. Hollingsworth, K.B. Holt and D.G. Unwin, J. Electroanal. Chem., 2013, 703, 14-22. (iii) Models of the iron-only hydrogenase: A comparison of chelate and bridge isomers of Fe2(CO)4{Ph2PN(R)PPh2}(m-pdt) as proton reduction catalysts, S. Ghosh, G.Hogarth, N. Hollingsworth, K. B. Holt, I. Richards, B. E. Sanchez and D. Unwin, Dalton Trans., 2013, 42, 6775-6792.

Nanoscale metal sulfides: Metal-sulfides (and selenides) are interesting materials which can adopt a range of different structural types which often allows for variable metal oxidation states since chalcogenides display a rich redox chemistry. Unlike the related metal-oxides, the novel chemical and physical properties of metal-sulfides are still underexplored and underutilised. Our main interest in this area surrounds the use of molecular metal-dithiocarbamate complexes as precursors to nanoparticulates metal-sulfides, especially iron- and nickel-sulfides but increasingly also towards sulfides of the heavier elements. We are interested in how variations in molecular precursors can be exploited to tailor-make nanosized metal-sulfides for applications in catalysis and have extensively studied decomposition mechanisms in order to gain control over the materials formed.  

Selected references:(i) Cu-doped CdSe/ZnS quantum dots: controllable photo-activated Cu+ storage and release vectors for catalysis, J.C. Bear, N. Hollingsworth, P.D. McNaughter, A.G. Mayes, M.B. Ward, T. Nann, G. Hogarth and I.P. Parkin, Angew. Chem., Int. Ed., 2014, 53, 1598-1601. (ii) In situ XAS of the solvothermal decomposition of dithiocarbamate complexes, H.-U. Islam, A. Roffey, N. Hollingsworth, R. Catlow, M. Wothers, N. De Leeuw, W. Bras, G. Sankar and G. Hogarth, Journal of Physics, Conf. Ser., 2013, 430, 012050.

Functionalised dithiocarbamates: Dithiocarbamates (S2CNR2) are cheap, readily available ligands whose complexes find use in areas as diverse as agriculture and medicine. These seemingly simple ligands are actually very smart, being able to stabilise metals in a wide-range of oxidation states (hard and soft) by making only very small geometric changes to the ligand backbone. Most work with dithiocarbamates centres on those with simple alkyl-substituents and the development of more interesting functionalised ligands is underexploited. In collaboration with James Wilton-Ely at Imperial College and Phil Blower at St. Thomas’ Hospital we are interested in the synthesis and exploitation of functionalised dithiocarbamates for applications in nanoparticle stabilisation, homogeneous catalysis and radiopharmaceuticals.

Selected references: (i) Ring-closing metathesis and nanoparticle formation based on diallyldithiocarbamate complexes of gold(I): Synthetic, structural and computational studies, S. Naeem, S.A. Serapian, A. Toscani, A.J.P. White, G. Hogarth and J.D.E.T. Wilton-Ely, Inorg. Chem., 2014, asap. (ii) Transition Metal Dithiocarbamates (1978-2003), G. Hogarth, Prog. Inorg. Chem., 2005, 53, 71-561. (iii) Metal-dithiocarbamate complexes: chemistry and biological activity, G. Hogarth, Mini Rev. Med. Chem., 2012, 12, 1202-1215.

Low valent cluster chemistry: Clusters are compounds that contain three or more metal ions and by judicious choice of synthetic pathway(s) is it possible to prepare such materials containing a diverse range of metal types. Our interest in cluster chemistry centres on low valent compounds especially those containing different metal ions such that cooperative effects between these can lead to the development of otherwise unattainable chemical and physical properties. Most of our work in the area is of a fundamental nature but we also seek use these compounds as precursors to metal nanoparticles for applications in catalysis. A recent highlight in this regard is the controlled synthesis of small gold nanoparticles from pre-formed gold-phosphine clusters. We also have an interest in the (artificial) interface between large low valent clusters and small metallic nanoparticles as a detailed understanding of the properties of the monodisperse clusters can lead to insight into those of nanoparticles.

Selected references: (i) Bimetallic osmium-tin complexes, J.C. Sarker, Kh.M Uddin, Md.S. Rahman, S. Ghosh, S.E. Kabir, D.A. Tocher, G. Hogarth, T.A. Siddiquee and M.G. Richmond, Inorg. Chim. Acta, 2014, 409, 320-329. (ii) Following the creation of active gold nano-catalysts using in situ X-ray absorption spectroscopy, J. Kilmartin, R. Sarip, R. Grau-Crespo, D. Di Tommaso, G. Hogarth, C. Prestipino, and G. Sankar, ACS Catalysis, 2012, 2, 957-963. (iii) Cluster chemistry in the Noughties: new developments and their relationship to nanoparticles, G. Hogarth, S.E. Kabir and E. Nordlander, Dalton Trans., 2010, 39, 6153-6174.

Dr Hogarth's Research Portal