Chemical Speciation using Advanced Spectroscopic Methods

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Metal ions are extensively used in industry with applications in agriculture, catalysis, batteries, etc. They also have diverse biomedical applications with anticancer, radiopharmaceutical or antibacterial activities. Since the discovery of cis-platin (cis-[Pt(NH3)2Cl2]) in the 1970s as the first metal-based anticancer chemotherapeutic agent, many research activities have focused on developing new metal complexes with anticancer properties. The goal has been to identify chemical reagents that have a higher selectivity toward cancerous cells and less toxic side effects compared with cis-platin. Bimetallic complexes of rhodium(2+), ruthenium(2+/3+) and rhenium(3+) ions, with (O,O) or (O,N)-donor species bridging between the two metal ions and a (semi) paddle wheel structure, are promising metal-based antitumor active compounds, with DNA as their primary target. However, these are not clinically in use mainly because their interactions with other biomolecules are not fully understood. We will therefore investigate the reaction products of these bimetallic complexes with selected amino acids, including histidine, methionine, cysteine and its derivatives, as well as the tri-peptide glutathione, as models for interactions of these bimetallic compounds with proteins and enzymes. For this purpose, we will use the X-ray region of synchrotron light, which is more than a million times brighter than the sun and is produced at synchrotron facilities around the world, including the Canadian Light Source (CLS). A state-of-the-art microscopy technique with a synchrotron light source will be used to monitor the cellular uptake of these antitumor active complexes and map the intracellular distribution of elements, such as rhodium, rhenium, ruthenium, sulfur and phosphorus, in each cell. This knowledge will help to understand the fate of this class of antitumor-active compounds as they enter the cell. We are also interested in a new generation of lithium ion batteries, in which ionic liquids (ILs) are used as non-flammable electrolytes and lithium (Li) metal as the anode. Due to the highly reactive surface of Li, the IL is decomposed at its surface and a solid electrolyte interphase (SEI) is formed. Depending on the type of IL used, the SEI can be “beneficial”, allowing extended cycling of the battery, or “detrimental”, impending the battery performance. We will use state-of-the-art synchrotron-based techniques to identify the chemical species formed in the SEI on the surface of Li electrodes. During this research program, several graduate and undergraduate students will gain experience in using a wide range of spectroscopic techniques, as applied to both biomedical and clean energy applications. Another important purpose of this research is to promote synchrotron science in Canada and to train future users of the CLS facility in Saskatoon.