The Macromolecular, Supramolecular, and Nanochemistry Program of the Chemistry Division supports the work of Prof. C. Scott Hartley in the Department of Chemistry & Biochemistry at Miami University. In nature, the structural complexity of large molecules (e.g., proteins), and ultimately their function, is generated by the folding of smaller molecular pieces (oligomers and polymers). This fact has inspired many efforts to study non-biological "foldamers" smaller molecular pieces that fold in well-defined ways. Research in the Hartley group focuses on the ortho-phenylenes, a simple class of foldamers formed from directly connected aromatic rings. In this project, the Harley group develops methods to control the folding of o-phenylenes and incorporates the rings into more complex structures. The project involves graduate students, undergraduates, and high-school teachers working to understand fundamental concepts of molecular folding, self-assembly, and molecular recognition, using the techniques of organic synthesis, computational chemistry, and various characterization methods.
The ortho-phenylenes combine several features that make them attractive as "next-generation" foldamers. They are straightforward to synthesize. Their folding behavior is easily modeled using simple, inexpensive methods. Their exact, solution-phase folding state can be characterized by NMR spectroscopy. This project has three specific aims that take advantage of these features. First, the twist-sense of o-phenylene folding is controlled using chiral end groups. While this sort of control over oligomer folding has been demonstrated in other systems, it is critical for more advanced uses of o-phenylenes. If successful, may be used to test o-phenylenes for spin-selective electron transport. Second, o-phenylene subunits are linked together into macrocycles. This simple system represents a first step toward incorporating o-phenylene secondary structures (i.e., helices) into higher-order structures, and provides a framework to test the conformational interaction between bridged foldamer subunits. Finally, o-phenylenes are functionalized with macrocycles to create binding sites along their sides. The architectures represents a first step toward o-phenylene-based molecular recognition.