Thioether and Selenoether-functionalized Metal-carboxylate Frameworks as Asymmetric Solid State Catalysts
- Zhengtao XU (Principal Investigator / Project Coordinator)Department of Chemistry
DescriptionThe researchers pursue functionalized porous crystalline networks for highly efficient metal-mediated catalysis in the solid state. In comparison to the conventional solution-based metal-mediated catalysts, these solid state systems are to provide convenient separation of the products and easy recycling of the catalysts. Specifically, the researchers aim for structurally well-defined homochiral networks that provide accurate control over the enantioselectivity of the reactions, such that the right-handed or the left-handed (but not both) pathway can be selectively activated—a selectivity that is widely important for pharmaceutical synthesis and other syntheses. For this, they take a cross-cutting approach that draws on advances from the two fertile fields of metal-mediated catalysis and coordination solid state chemistry.The strong enantioselectivity of metal-mediated catalysts is primarily derived from the associated chiral organic molecule that bonds to the metal center (e.g., Rh or Pd) through ligating sites such as the P or S atoms. To transplant these solution-based catalytic behaviors into the solid state, the researchers will assemble a porous framework that is equipped with similar chiral ligating sites, which can then take up catalytic metal species (e.g., Rh or Pd) to generate the catalytic structure. The assembly of such a functionalized framework, in fact, poses a central challenge for the field.To take on this challenge, the researchers propose to construct the framework from a class of rigid and symmetrical organic molecules containing two distinct sets of functional groups. One set is the chemically hard carboxylate groups at the terminal sites of the molecule; the other is the thioether groups (-SR, with the soft S atom) at the central portion of the molecule. The crux here is that chemically hard metal ions (such as Ln3+) will link up exclusively the carboxylate groups to form a robust metal-organic framework, while leaving the soft thioether groups as free standing groups inside the established framework. By using a chiral thioether group, they will be able to impose homochiral features on the framework, and provide chiral bonding pockets for the incoming the catalytic metal centers such as Rh or Pd.
|Effective start/end date||1/09/08 → 28/11/12|