1. Redox-Switchable N-Heterocyclic Carbenes and Their Corresponding
Homo- and Heterometallic complexes
Daniela Tapu, Kennesaw State University, Kennesaw, Ga, 30144
This project pursues the synthesis and characterization of a novel class of heterobidentate ligands derived from imidazol-2-ylidenes. Understanding the chemistry of these redox-active ligands will allow us to evaluate their potential role in applications, such as redox-switchable catalysts, that could allow for on-off switching of catalyst activity. In addition, this could provide a strategy for the separation of homogeneous catalysts from the products of a reaction. The chemical or electrochemical change in the oxidation state of the redox active moiety would result in drastic changes in polarity and, as a result, the possibility to exert high control over the solubility of the catalyst. Ideally, the catalyst would be precipitated by electrodeposition and recovered for reuse, thus increasing cost-efficiency and reducing contamination of the reaction products with heavy-metal impurities. This will also allow for a purer waste stream.
This first year we have developed a series of ligands that enable the incorporation of 2 or more metal centers into a complex using a combination of - and - bonding that is tightly coupled through the ligand. One of the ligands has two electroactive sites, one reversible and one quasi-reversible.
• Further work will be directed toward the incorporation of these new ligands in bi- and multi-metallic complexes and the study of their properties.
In addition we have developed the first fluorescent imidazole-2-thione based ligand. The coordination chemistry of this thione was explored and a series of main group and transition metal complexes derived from the thione were prepared and characterized. The X-ray structure of a Indium complex is shown above.