The main research thrust in the Department of Chemistry at the University of Johannesburg is in the area of catalysis. All the research staff, are involved in research into various aspects of this study field. In addition to this focus area all researchers also have other areas of expertise which they are actively building, ensuring a vibrant and dynamic environment in the Department. The industrial focus of various projects has ensured excellent cooperation with industrial partners as well as the creation of a Centre of Excellence in Catalysis by the University Research Committee, which is funded by the University.
Research Groups in the Department
Muller Research Group
The research of Prof (Fanie) Alfred Muller is
primarily focussed on the coordination chemistry of the lanthanide series of
elements. The group interests for application of these materials
primarily on catalysis, luminescence and medicinal. Collaborations have been
established with Necsa (Drs Sonopo and Jansen) and University of Technology Sydney,
Australia (Prof Williams).
Arderne Research Group
Research that is carried out at the Honours level involves the crystallographic study of long-chained materials. Particular focus is on the structural characteristics and physical properties of long-chained n-alkyl diammonium salts as they are precursors to layered inorganic-organic perovskite-type hybrids; they are bidentate ligands in transition metal complexes that have applications in propellants, explosives and pyrotechnic compositions; they have structure directing properties in the synthesis of a number of zeolites and a number of new novel nanomaterials; and many have biological applications. Currently, there is one student working on this project – Gerhard Roodt
Primary research projects are:
- Metal induced cleavage of peptide and amide bonds using Co(III) amine and Co(III) amino acid complexes and their investigation as urease mimics.
This project is an experimental study of the synthesis, analysis and reaction of cobalt(III) amine and cobalt(III) amino acids complexes with urea-based materials to establish if cleavage of the amide and peptide bonds is successful. Also the research is undertaken in an attempt to determine and understand the mechanistic steps of these reactions and to conclusively determine if the cleavage occurs hydrolytically or by oxidative means and to establish if the metal complexes will function effectively as urease mimics. The broader scope of this project is in the field of biocatalysis. This project is currently being performed in collaboration with Professor Ivan Bernal, retired Emeritus Professor of the University of Houston, Texas, USA, Professor Ilia Guzei, visiting Professor UJ and director of Crystallography at the University of Madison, Wisconsin and Professor Demetrius Levendis, Professor of Chemistry at the University of the Witwatersrand, Johannesburg. I currently have one MSc student working on this project – Siphamandla “Spha” Nyathi.
- Structural investigation of natural products and their application in the field of medicinal chemistry.
This project is a structural study of a number of natural and synthetic materials that are being tested for medicinal properties. The research undertaken involves the structural characterization using X-ray crystallography of a large number of active ingredients that have been extracted from medicinal plants. Their structural characteristics are being investigated in an effort to understand their medicinal activity. This project is a collaboration with the Department of Applied Chemistry at the University of Johannesburg’s Doornfontein campus (DFC), in particular with my colleague, Dr Derek Ndinteh.
Chromatography and Atomic Spectrometry Research Group
The Chromatography and Atomic Spectrometry Research Group is committed to play a unique role in solving problems of academic, environmental, and industrial interest germane to the field of analytical chemistry. In particular, we explore complex matrices such as food, petrochemical and environmental systems using chromatography and atomic spectrometry including High Resolution Continuum Source AAS, ICP-OES and ICP-MS to gain a broader understanding of the chemical systems based on elemental and speciation data. The first thrust area focuses on authentication of food products using multi-elemental data and stable isotope ratio measurement. Our emphasis here is to determine elemental fingerprints to track the origin of food products. The treatment of mine drainage and the sustainable use of recovered treatment by-products has attracted a growing interest in recent years. Here, we explore the desalination and heavy metals’ removal efficiency of high performance hybrid materials and mesoporous polymers. We are also actively engaged in quantification of metals in synthetic compounds and correlating their concentrations with coordination numbers. Elemental speciation, i.e., the analysis of distribution of an element among defined chemical species, is an active and highly interdisciplinary research topic and becomes necessary when the biological or biogeochemical cycles of essential or toxic elements have to be understood. We explore point and non-point sources of pollution via speciation of metallic and metalloidal species, particularly arsenic, chromium, mercury, lead, and selenium.
Carbohydrate and Medicinal Chemistry research group
The Carbohydrate and Medicinal Chemistry research group focuses on the discovery and development of new compounds which can be used as anti-infective agents of the neglected diseases (TB, Malaria and HIV/AIDS). The research program is divided into three broad areas:
- Reaction methodology development toward the synthesis of biologically active compounds
- Synthesis of medicinally important carbohydrate based compounds
- Synthesis and characterization of metal complexes and nanoparticles as anti-infective agents
Carbohydrates are the most prominently exposed class of molecules that decorate the surfaces of all living cells. These carbohydrates having flexible chains and many potential binding sites are involved in intercellular communications of biological systems such as cell-cell recognition. Such interactions play important roles in biological processes such as fertilization, embryogenesis, immune responses, nervous system development, hormone activities, maintenance and pathogenesis of tissues, viral and bacterial infections and cancer metastasis. If success in the utilization of the potential of carbohydrates in the biological systems is to be achieved, the issue of ease of obtaining the building blocks, development of new reaction methodologies and synthetic strategies have to be addressed. Even though a number of methodologies are reported in the literature, the subject still remains challenging as more and more new functions and needs for carbohydrates emerge from time to time. With the worldwide drive towards a greener chemistry and the trend in organic chemistry, among the numerous types of carbohydrate transformations our group focuses on the development of catalytic and environmentally friendly reaction protocols for the transformation of glycals and 1,2-cyclopropanated sugars into useful derivatives. Glycals are C1-2 unsaturated sugar derivatives which have found wide application as building blocks in the synthesis of complex carbohydrate compounds. The research group has developed a number of simple and novel methods for the transformation glycals and the analogues cyclopropanated sugars into 2-deoxy glycosides, suitably activated glycosyl donors, thiochromans, thiochromenes, benzothiophenes, chromenes etc. The methodologies so developed are being applied as catalysts for Corey-Chaykovsky Reaction and in the synthesis of medicinally valuable carbohydrate constructs of interest such as anti-malarial, anti-cancer, and anti-diabetics agents.
Carbonylation reactions represent a powerful approach to generate a variety of functional groups from C-C unsaturation, using carbon monoxide and other ancillary reagents. The importance of the carbonyl group derives not only from its own inherent reactivity, being susceptible to both nucleophilic attack at carbon and electrophilic attack on oxygen, but also from its particular ability to stabilize an adjacent carbanion by charge delocalization into the carbonyl double bond. Carbonylation reactions are quite diverse and include, but are not limited to, the synthesis of aldehydes (hydroformylation), carboxylic acids (hydrocarboxylation) and esters (methoxycarbonylation).
Our research is focussed on the hydroformylation and the methoxycarbonylation reaction. The critical aspects that ligand architecture impact on the rate and selectivity of the reactions are investigated. Ultimately, to gain a fundamental understanding of reaction mechanisms toward the development of chemical methodologies that will allow the application of new transition metal catalyzed carbonylation reactions in both fine chemical synthesis (hydroformylation; typically for industrial scale synthesis) and industrial scale synthesis (methoxycarbonylation; typically for fine chemical synthesis).
Research Group of James Darkwa
Transition Metal Complexes as Homogeneous Catalysts and as Potential Metallodrugs
My research group has two focus areas namely, using transition metal complexes as homogeneous catalysts and investigation the potential of precious metal complexes as anticancer, anti-HIV and anti-malarial agents.
Over the past 15 years the group has investigated nitrogen donor chromium, iron, cobalt, nickel and palladium complexes in olefin transformation reactions such as ethylene oligomerization and polymerization catalysts. This led to inadvertently discovering in 2007 that a combination pyrazolyl nickel and palladium pre-catalysts with ethylaluminium dichloride as co-catalysts produced tandem catalytic systems that oligomerize ethylene and subsequently used the ethylene oligomers to alkylate toluene through a Friedel-Crafts process. This has led to several publications on this subject, the most prominent ones are: Ojwach et al., Organometallics, 2009, 28, 2127; and Bhudai et al., Catal. Sci. Technol., 2013, 3, 3130, which was selected as an inside cover article. We have extended the use of nitrogen donor transition metal catalysts to co-polymerization of carbon monoxide (Obuah et al., Organometallics, 2013, 32, 980) and carbon dioxide and epoxide co-polymerization and ring opening polymerization of cyclic esters like D,L-lactide and ε-caprolcatones (Appavoo et al., Polyhedron, 2014, 69, 55), the latter ring opening polymerization provides access to green polymers.
The second area of focus involves the synthesis of palladium, platinum and gold complexes that are potential metallodrugs. In particular, a number of phosphinegold(I) complexes have been tested for their anticancer, anti-HIV and anti-malarial activity and have been found to be active (Keter et al., Inorg. Chem., 2014, 53, 2058; Adokoh et al., Biomacromolecules, 2014, 15, 3802; Bjelosevic et al., J. Organomet. Chem., 2012, 720, 52.
We are continuing with several projects in these two focus areas to find better catalysts and processes; and also to find better metallodrugs.
Selected recent publications
Phenoxysalicylaldimine supported chromium(III) pre-catalysts for ethylene polymerization. M. Yankey, C. Obuah J. Darkwa. Macromol. Chem. Phys. 2014, 215, 1767.
(Phenoxyimidazollyl-salicylaldimine)iron complexes: synthesis, properties and iron catalysed ethylene reactions. M. Yankey, C. Obuah, I. A. Guzei, E. Osei-Twum, G. Hearne, J. Darkwa, Dalton Trans. 2014, 43, 13913.
Ferrocenylpyrazolyl palladium complexes as catalysts for the polymerization of 1-heptene and 1-octene to branched polyolefins. C. Obuah, A. Munyaneza, I. A. Guzei, J. Darkwa, Dalton Trans. 2014, 43, 8940.
Phosphinogold(I) dithiocarbamate complexes: effect of the nature of phosphine ligand on anticancer properties. F. K. Keter, I. A. Guzei, M. Nell, W. E. van Zyl, J. Darkwa, Inorg. Chem. 2014, 53, 2058.
Bis(3,5-dimethylpyrazole) copper(II) and zinc(II) complexes as efficient initiators for the ring opening polymerization of ε-caprolactone and D,L-lactide. D. Appavoo, B. Omondi, I. A. Guzei, J. van Wyk, O. Zinyemba, J. Darkwa, Polyhedron, 2014, 69, 55.
Solvent and co-catalyst dependent pyrazolyl nickel(II) catalyzed ethylene oligomerization and polymerization reactions. C. Obuah, B. Omondi, K. Nozaki, J. Darkwa, J. Mol. Catal. A: Chem. 2014, 382, 31.
Tandem ethylene oligomerization and Friedel-Crafts alkylation of toluene catalyzed by bis-(3,5-dimethylpyrazol-1-ylmethyl)benzene nickel(II) complexes and ethylaluminum dichloride. A. Budhai, B. Omondi, S. O. Ojwach, C. Obuah, E. Y. Osei-Twum, J. Darkwa, Cat. Sci. Tech. 2013, 3, 3130.
Synthesis and evaluation of polymeric gold glycol-conjugates as anti-cancer agents. M. Ahmed, S. Mamba, X-H. Yang, J. Darkwa, P. Kumar, R. Narain. Bioconjugate Chem. 2013, 24, 979.
Pyrazolylimine iron and cobalt, and pyrazolylamine nickel complexes: synthesis and evaluation of nickel complexes as ethylene oligomerization catalysts. M. K. Ainooson, I. A. Guzei, L. C. Spencer, J. Darkwa, Polyhedron, 2013, 53, 295.
Ethylene and styrene carbon monoxide copolymerization catalyzed by pyrazolyl palladium(II) complexes. C. Obuah, M. K. Ainooson, S. Boltina, I. A. Guzei, K. Nozaki, J. Darkwa, Organometallics, 2013, 32, 980.
Platinum(II) and gold(I) complexes based on 1,1’-bis(diphenylphosphino)metallocene derivatives: Synthesis, characterization and biological activity of the gold complexes. H. Bjelosevic, I. A. Guzei, L. C. Spencer, T. Persson, F. H. Kriel, R. Hewer, M. J. Nell, J. Gut, C. E. J. van Rensburg, P. J. Rosenthal, J. Coates, J. Darkwa, S. K. C. Elmroth, J. Organomet. Chem. 2012, 720, 52.
Palladium(II), platinum(II) and gold(I) complexes containing chiral diphosphines of the Josiphos and Walphos families - synthesis and evaluation as anticancer agents Polyhedron. T. V. Segapelo, S. Lillywhite, E. Nordlander, M. Haukka, J. Darkwa, Polyhedron 2012, 36, 97.
Material Science and Technology Laboratory (Mallick Group)
Proton coupled electron transfer reaction
Proton-coupled electron transfer (PCET) reactions are those in which an electron and a proton are transferred together. The particularity of such reactions is that the electron and the proton are transferred to different canters. Sequential transfer of electron and proton pathways is lower in energy than concerted pathways. The multiple site electron-proton transfer reaction is another class of the PCET reaction in which (a) an ‘electron-proton donor’ transfers electrons and protons to spatially separated acceptors or (b), an ‘electron-proton acceptor’ accepts electrons and protons from spatially separated donors. During the process of polymerization of aniline, the released electron and proton initiate the reduction process of the 4-nitrophenol through a sequential electron transfer proton transfer (ETPT) mechanism. While each step of polymerization involves the release of two electrons, the residual electrons, which do not take part in the ETPT process, are used to reduce the silver ions to form silver atoms. The coalescence of these silver atoms ultimately forms silver nanoparticles, which catalyze the reduction of 4-nitrophenol.
Polymer supported metal nanoparticles or metal ion catalyzed coupling reaction
Fabrication of polymer supported metal nanoparticles or metal ion composites and its catalytic application on CC, CS and CN bond formation organic reactions for the synthesis of biologically important intermediates.