Synthetic Methods, Enantioselective Catalysis, Bioorganic Chemistry, Carbohydrate Chemistry

 

Our research program revolves around the theme of synthetic macromolecular and supramolecular organic chemistry. We are particularly interested in the design and synthesis of functional macromolecules that fold into a well-defined chiral secondary structure because these molecules have tremendous potential to function as enantioselective catalysts, chemical sensors and liquid crystals among many other applications in materials science and molecular recognition. Students involved in my research program will primarily learn techniques in synthetic organic chemistry; however, an appreciation for polymer synthesis and characterization, organometallic chemistry and catalysis; and supramolecular synthesis will also be developed.

The research goals of my group can be broadly classified into two categories: (a) developing molecules with well-defined conformational properties and (b) utilizing these materials in applications for which conformational order is crucial for function. Specifically, the following projects are underway in my laboratory.

1. Helically-folded, Intramolecularly Hydrogen-Bonded Dendrimers. The intramolecular self-organization necessary to induce a molecule to fold into a specific conformation is driven by the cooperative interplay of multiple molecular recognition processes such as hydrogen-bonding, van der Waals, electrostatic and solvophobic interactions. We are developing dendrimers that adopt a chiral propeller-like or helical conformation as a consequence of the cooperative action of intramolecular hydrogen-bonding and nonbonded packing interactions that develop at higher generations and in poor solvents. The chiral conformational preference of these materials is also being exploited in enantioselective catalysis.

 

 

2. Desymmetrized water-soluble amphiphilic dendrimers. We are also developing hydrophobic dendrimers with a hydrophilic periphery so that a favorable interaction with solvent (water) will occur only on the surface. This differential solvation compresses (or aggregates) the system in such a way to minimize the water-dendrimer interface and leads to a more compact and rigid structure. We are studying the effect of hydrophobic compression on the conformational properties of these materials. Such amphililic materials may find application as phase-transfer catalysts.

3. Supramolecularly Self-Organizing Dendrimers. Intramolecular hydrogen-bonding interactions in dendrimers can be used to induce a dendrimer to adopt a flat disc-like conformation. These “discotic” dendrimers self-assemble in columns resulting in the development of a hexagonally ordered columnar liquid crystalline mesophase in the bulk and in solution as characterized using electron diffraction, TEM and XRD techniques.