Assoc Prof Gregory Smith
The use of transition metals in the fields of catalysis and medicine is a fast-growing area of interest, particularly linked to the improvement of the economy, especially for a developing country such as South Africa. South Africa has access to a range of transition metals, especially the Platinum group metals, essential in both fields of catalysis and medicine.
Catalysis is one of the most important technologies in modern times and is continuing to make great impact on industrial economies. In the South African context, there are large quantities of organic feedstocks, such as alkanes and alkenes that can be selectively transformed into value-added chemicals. To effect these transformations, new catalysts are required.
Our research interests are aimed at the development and synthesis of new transition metal complexes and an investigation into their applications in catalysis and as new materials. In these projects, various transition metal complexes are based on imine and phosphorus-containing ligands that will be investigated initially as mononuclear catalysts. We have previously prepared multinuclear imine-based catalysts for olefin oligomerisation/polymerization reactions and for Heck cross-coupling reactions, and will use our current understanding of these systems to develop more efficient systems. Catalytic reactions that we primarily focus on include polymerization, oligomerisation and hydroformylation of alkenes and carbon-carbon cross-coupling reactions.
Another question we seek to address is the synthesis of environmentally friendly catalysts. This stems from studies on linear polynuclear and dendritic catalysts that maintain high activity and selectivity and can be easily separated from reaction mixtures. The immobilization of transition metal catalysts on polymeric or dendritic supports offers a number of advantages. The supported complexes can be readily separated from reaction mixtures, facilitating recycling of the catalysts to avoid environmental toxicity and makes purification of products easier. This area bridges the gap between homogeneous and heterogeneous catalysis. The rationale for this study is to synthesize alternative, cheaper, more efficient catalysts that will be of interest to the South African industry.
Transition metal complexes are an important resource for the generation of chemical diversity in the search for novel therapeutic and diagnostic agents. Cisplatin represents one of the most active and clinically useful metal complexes in the treatment of cancer. However, cisplatin induces normal tissue toxicity, particularly to the kidney, and the development of acquired drug resistance can occur in initially responsive disease types. The field of bioorganometallic chemistry stemmed from the discovery if titanocene dichloride, the first organo-transition metal compound to be studied as an alternative to cisplatin, which underwent numerous clinical evaluations. Despite the successes of cisplatin and related platinum antitumour agents, research into non-platinum anticancer agents has evolved due to problems associated with platinum-based chemotherapies.
The use of metallomacromolecules as biological and therapeutic agents is a prolific area of research, due to their multivalency, which lead to increased interaction between a dendrimer-drug conjugate and target bearing multiple receptors, further improving the selectivity to cancer cells. Tumours can be specifically targeted by exploiting the ‘enhanced permeability and retention’ (EPR) effect, a phenomenon in which macromolecules can accumulate at the tumour site due to an increase in blood vessel permeability within diseased tissues compared to normal tissues.
In order to exploit size selective uptake of drugs into tumour cells effectively, macromolecular large compounds are required. Our current interest focuses on the investigation of metallomacromolecules as molecular tools in biological applications, especially as chemotherapeutics and as diagnostic agents. These projects therefore intend to combine the cytotoxicity of certain PGM complexes with dendrimers, as either potential therapeutic and/or imaging agents, in view to obtain a synergistic effect of the multibranched system.
- Heterometallic Half-sandwich Complexes Containing a Ferrocenyl Motif: Synthesis, Molecular Structure, Electrochemistry and Antiplasmodial EvaluationWinnie Nkoana, Dubekile Nyoni, Prinessa Chellan, Tameryn Stringer, Dale Taylor, Peter J. Smith, Alan T. Hutton and Gregory S. Smith*. Journal of Organometallic Chemistry, 2014, 752, 67-75.
- Synthesis and evaluation of new polynuclear organometallic Ru(II), Rh(III) and Ir(III) pyridyl ester complexes as in vitro Antiparasitic and Antitumor Agents. Prinessa Chellan, Kirkwood M. Land, Ajit Shokar, Aaron Au, Seung Hwan An, Dale Taylor, Peter J. Smith, Tina Riedel, Paul J. Dyson, Kelly Chibale and Gregory S. Smith*. Dalton Transactions, 2014, 43, 513-526.
- Neutral and Cationic Osmium(II)-Arene Metallodendrimers: Synthesis, Characterisation and Anticancer Activity Preshendren Govender, Fabio Edafe, Banothile Makhubela, Paul J. Dyson, Bruno Therrien, and Gregory S. Smith*. Inorganica Chimica Acta, 2014, 409, 112-120.
- Di- and Trinuclear Ruthenium-, Rhodium-, and Iridium-Functionalised Pyridyl Aromatic Ethers: A New Class of Antiparasitic Agents. Prinessa Chellan, Kirkwood M. Land, Ajit Shokar, Aaron Au, Seung Hwan An, Dale Taylor, Peter J. Smith, Kelly Chibale and Gregory S. Smith*. Organometallics, 2013, 32, 4793-4804.
- Synthesis, Characterisation, antiparasitic and cytotoxic evaluation of thioureas conjugated to polyamine scaffolds Tameryn Stringer, Dale Taylor, Carmen de Kock, Hajira Guzgay, Aaron Au, Seung Hwan An, Benjamin Sanchez, Raquel O-Connor, Neal Patel, Kirkwood M. Land, Peter J. Smith, Denver T. Hendricks, Timothy J. Egan and Gregory S. Smith*. European Journal of Medicinal Chemistry, 2013, 69, 90-98.
- Water-Soluble Half-Sandwich Ru-Arene complexes: Synthesis, Structure, Electrochemistry, DFT Studies, and Aqueous Phase Hydroformylation of 1-Octene. Leah C. Matsinha, Peter Malatji, Alan T. Hutton, Gerhard A. Venter, Selwyn F. Mapolie and Gregory S. Smith*. European Journal of Inorganic Chemistry, 2013, 4318-4328.
- Synthesis, characterisation and preliminary in vitro cellular uptake studies of 67Ga(III) thiosemicarbazones. Tawfeeq Ismail, Daniel D. Rossouw, Philip Beukes, Jacobus P. Slabbert and Gregory S. Smith*. Inorganic Chemistry Communications, 2013, 33, 154-157.
- Heterobimetallic Ferrocenylthiosemicarbazone palladium(II) Complexes: Synthesis, Electrochemistry and Antiplasmodial Evaluation. Muneebah Adams, Carmen de Kock, Peter J. Smith, Peter Malatji, Alan T. Hutton, Kelly Chibale and Gregory S. Smith*. Journal of Organometallic Chemistry, 2013, 739, 15-20.
- Next Generation PhotoCORMs: Polynuclear Tricarbonylmanganese(I)-Functionalized Polypyridyl Metallodendrimers. Preshendren Govender, Sandesh Pai, Ulrich Schatzschneider and Gregory S. Smith*. Inorganic Chemistry, 2013, 52, 5470-5478.
- Synthesis, characterisation and antiplasmodial evaluation of cyclopalladated thiosemicarbazone complexes. Muneebah Adams, Carmen de Kock, Peter J. Smith, Kelly Chibale and Gregory S. Smith*. Journal of Organometallic Chemistry, 2013, 736, 19-26.
- The synthesis and antiparasitic activity of aryl- and ferrocenyl-derived thiosemicarbazone ruthenium(II)-arene complexes. Muneebah Adams, Yiqun Li, Heena Khot, Carmen de Kock, Peter J. Smith, Kirkwood Land, Kelly Chibale and Gregory S. Smith*. Dalton Transactions, 2013, 42, 4677-4685.
- Synthesis and characterisation of mono- and binuclear iminopyridyl and salicylaldimine Ru(II)-arene complexes. Leah C. Matsinha, Selwyn F. Mapolie and Gregory S. Smith. Polyhedron, 2013, 53, 56-61.
- Neutral and cationic multinuclear half-sandwich rhodium and iridium complexes coordinated to poly(propyleneimine) dendritic scaffolds: Synthesis and cytotoxicity. Richard Payne, Preshendren Govender, Bruno Therrien, Catherine M. Clavel, Paul J. Dyson, and Gregory S. Smith*. Journal of Organometallic Chemistry, 2013, 729, 20-27.
- Synthesis, Characterization and Pharmacological Evaluation of Silicon-Containing Aminoquiniline Organometallic Complexes As Antiplasmodial, Antitumor and Antimycobacterial Agents . Yiqun Li, Carmen de Kock, Peter J. Smith, Hajira Guzgay, Denver T. Hendricks, Krupa Naran, Valerie Miztahi, Digby F. warner, Kelly Chibale, and Gregory S. Smith*. Organometallics, 2013, 32, 141-150.
- The influence of RAPTA moieties on the antiproliferative activity of peripheral-functionalised poly(salicylaldiminato)metallodendrimers. Preshendren Govender, Lara C. Sudding, Catherine M. Clavel, Paul J. Dyson, Bruno Therrien, and Gregory S. Smith*. Dalton Transactions, 2013, 42, 1267-1277.
- Cyclometallated Pd(II) thiosemicarbazone complexes: new catalyst precursors for Suzuki-coupling reactions. Hong yan, Prinessa Chellan, Tingyi Li, Jincheng Mao, Kelly Chibale and Gregory Smith* . Tetrahedron Letters, 2013, 54, 154-157.
- Aqueous-phase Hydroformylation of 1-octene using hydrophilic sulfonate salicylaldimine dendrimers. Emma B. Hager, Banothile C.E. Makhubela and Gregory S. Smith*. Dalton Transactions, 2012, 41, 13927-13935.
- Exploring the Versatility of Cycloplatinated Thoisemicarbazones as Antitumor and Antiparasitic Agents. Prinessa Chellan, Kirkwood M. Land, Ajit Shokar, Aaron Au, Seung Hwan An, Catherine M. Clavel, Paul J. Dyson, Carmen de Kock, Peter J. Smith, Kelly Chibale, and Gregory S. Smith*. Organometallics, 2012, 31, 5791-5799.
- Hydroformylation of 1-octene using low-generation Rh(I) Metallodendritic Catalysts based on a Tris-2-(2-pyridyliminoehtyl)amine Scaffold. Banothile C.E. Makhubela, Anwar M. Jardine, Gunnar Westman and Gregory S. Smith*. Dalton Transactions, 2012, 41, 10715-10723.
- Bio-Metallodendrimers – Emerging Strategies in Metal-Based Drug Design. Preshendren Govender, Bruno Therrien and Gregory S. Smith*. European Journal of Inorganic Chemistry, 2012, 2853-2862.
- Rh(I) Complexes Supported on a Biopolymer as Recyclable and Selective Hydroformylation Catalysts. Banothile C.E. Makhubela, Anwar Jardine and Gregory S. Smith*. Green Chemistry, 2012, 14, 338-347.
- Synthesis and characterisation of multimeric salicylaldimine thiosemicarbazones and their Pd(II) and Pt(II) complexes. Tameryn Stringer,DenverT. Hendricks, Hajira Guzgay and Gregory S. Smith*. Polyhedron, 2012, 31, 486-493.
- Synthesis and in vitro Evaluation of Palladium(II) Salicylaldiminato Thiosemicarbazone Complexes against Trichomonas Vaginalis. Prinessa Chellan, Tameryn Stringer, Ajit Shokar, Padraick J. Dornbush, Guillermo Vazquez-Anaya, Kirkwood M. Land, Kelly Chibale and Gregory S. Smith. Journal of Inorganic Biochemistry, 2011, 105, 1562-1568.
- Ferrocenylthiosemicarbazones Conjugated to a Poly(propyleneimine)Dendrimer Scaffold: Synthesis and In Vitro Antimalarial Activity. Setshaba D. Khanye, Jiri Gut, Philip J. Rosenthal, Kelly Chibale and Gregory S. Smith*. Journal of Organometallic Chemistry, 2011, 696, 3296-3300.
- Targeted and multifunctional arene ruthenium chemotherapeutics. Gregory S. Smith and Bruno Therrien. DaltonTransactions, 2011, 40, 10793-10800.
- Hydroformylation activity of multinuclear rhodium complexes coordinated to dendritic iminopyridyl and iminophosphine scaffolds. Nathan C. Antonels, John R. Moss and Gregory S. Smith. Journal of Organometallic Chemistry, 2011, 696, 2003-2007.
- Pd Nanosized Particles Supported on Chitosan and 6-Deoxy-6-Amino Chitosan as Recyclable Catalysts for Suzuki-Miyaura and Heck Cross-coupling Reactions. Banothile C.E. Makhubela, Anwar Jardine and Gregory S. Smith. Applied Catalysis A: General, 2011, 393, 231-241.
- Antiproliferative activity of chelating N,O- and N,N-ruthenium(II) arene functionalised poly(propyleneimine) dendrimers scaffolds. Preshendren Govender, Anna K. Renfrew, Catherine M. Clavel, Paul J. Dyson, Bruno Therrien, and Gregory S. Smith. DaltonTransactions, 2011, 40, 1158-1167.
- Synthesis, Structure and in Vitro Biological Screening of Palladium(II) Complexes of Functionalsed Salicylaldimine Thiosemicarbazones as Antimalarial and Anticancer Agents. Prinessa Chellan, Nelusha Shunmoogam-Gounden, Denver T. Hendricks, Jiri Gut, Philip J. Rosenthal, Carmen Lategan, Peter J.Smith, Kelly Chibale and Gregory S. Smith. European Journal of Inorganic Chemistry, 2010, 3520-3528.
- Gold(I) derived thiosemicarbazone complexes with rare halogen-halogen interaction-reduction of [Au(damp-C1,N)Cl2]Setshaba D. Khanye, Nikoletta B. Bathori, Gregory S. Smith and Kelly Chibale. DaltonTransactions, 2010, 39, 2697-2700.
- Photocontrolled Living Anionic Polymerisation of Silicon-Bridged Ferrocenophanes with Fluorinated Substitutents: Synthesis and Characterisation of Fluorinated Polyferrocenylsilane (PFS) Homopolymers and Block Copolymers. Gregory S. Smith, Sanjib K. Patra,LawrenceVanderark, Saowanit Saithong, Jonathan Charmant and Ian Manners. Macromolecular Chemistry and Physics, 2010, 211, 303-312.