Research
The Grapperhaus Research Group is an inorganic chemistry group focused on the synthesis, characterization, and reactivity of metal complexes for applications in catalysis, renewable energy, and metal-containing therapeutics. The group works on interdisciplinary projects involving researchers with interests in Organic Synthesis, Computation, Biochemistry, and Engineering. We collaborate closely with colleagues in the Department of Chemistry, the Conn Center for Renewable Energy Research, and the Medical School. There are several ongoing projects.
Activation of Small Molecules
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With increasing concern over climate change and the mounting demands for fuel, a need for renewable energy is ever present. A part of the potential solution is the production of hydrogen from renewable and clean resources as an energy carrier. However, the hydrogen evolution reaction (HER) requires a catalyst to overcome the kinetic barrier. The most effective catalyst for HER is platinum, however platinum is a precious metal and scarce resource. The Grapperhaus group exploits the non-innocence ligands, such as bis(thiosemicarbazones), to confer nobility onto abundant, first row metals such as Zn and Ni, to reduce protons to hydrogen. The complexes are evaluated in non-aqueous solution as homogeneous electrocatalysts and as films deposited on carbon electrodes in aqueous environments.
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The group is also exploring metal-ligand cooperativity for the binding and activation of small molecules such as carbon dioxide. Modified thiosemicarbazone ligands capture CO2 by using the Lewis basicity of a non-coordinating nitrogen in conjunction with and Lewis acidity of the metal allowing for the capture of CO2 from gaseous streams and air. The cooperativity is currently being studied to note the trends in Lewis acidity and basicity, as well as modifying the parent system to increase activity. This project is currently funded by the National Science Foundation (1955268) in collaboration with Dr. Joshua Spurgeon, the Solar Fuels team leader in the Conn Center for Renewable Energy Research at UofL.
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Roll-to-roll Manufacturing of Continuous Perovskite Modules
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Perovskite solar cell research focuses on making the material that absorbs photons, called the absorber, more durable and efficient. This project will investigate the applicability of low-cost roll-to-roll manufacturing techniques for perovskite modules. The team will employ rapid deposition and annealing techniques, which are the processes used to deposit the absorber layer onto a substrate and then heating and cooling it to toughen the absorber. The team will then study the performance of the absorber layer and use the same techniques on the remainder of the device layers. The team aims to use these techniques to create a high throughput manufacturing process for perovskite modules in a commercial roll-to-roll facility. This project is currently funded by the Department of Energy.
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Electrochemical Reduction of Flue Gas CO2
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This project is a collaboration between the Grapperhaus Group and Dr. Joshua Spurgeon, theme leader for Solar Fuels at the Conn Center for Renewable Energy Research, in conjunction with the University of North Dakota’s Institute for Energy Studies. This project will pursue the development of a stable and efficient method to convert the CO2 directly from a power plant exhaust stream, which would aid in making the overall process more cost-effective. These contaminants can degrade the performance of an electrolysis reactor, making the direct electrochemical conversion of flue gas CO2 a challenging prospect. The team is working on novel molecular catalysts to guide the selectivity of the reaction within a new high-performance reactor designed for use with both water and organic solvent. This research is funded by the Department of Energy (DOE) National Energy Technology Laboratory (NETL).
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Design and Synthesis of Copper Complexes with Cancer Selective Antiproliferation Activity
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The Grapperhaus/ Buchanan laboratories have developed a library of >20 compounds that display selective anti-proliferation activity against the lung adenocarcinoma cell line (A549) with GI50 values less than 0.1 μM and greater than 20x selectivity relative to the nonmalignant lung fibroblast cell line (IMR-90) controls. The lead candidates are square planar Cu(II) complexes based on N2S2 hybrid thiosemicarbazone-alkylthiocarbamate ligands (H2TSTC). The ligands are modular and initial studies show that variation of substituent groups on the N2S2 ligand backbone influences the electronic structure (Cu(II) reduction potentials) of the molecule that has a direct effect on their anti-proliferation activity. The modification of substituents may also alter the physical structure of the molecule that could influence their cellular uptake and intracellular target binding. To assess the importance of physical structure, the group is currently working on the synthesis of coordination isomers that either have similar electronic structure and different antiproliferation activity or in spite of different electronic structures show no correlation with their antiproliferation activity.
