Fundamental Studies of the Hydrogen Bond Enhanced Halogen Bond (HBeXB) for Molecular Folding and Anion Transport

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Professor Orion Berryman of the University of Montana is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) and the Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) Programs of the Division of Chemistry to devise means to control how chain molecules are shaped into tubular helical structures (foldamers). The project exploits a recent observation that a hydrogen bond that is judicially placed in a chain molecule can cause the molecule to fold, mimicking the folding ability of proteins and nucleic acids. Special functional units are strategically placed inside the molecular tube to allow for the transport of anions. The project helps define the requirements to efficiently incorporate the hydrogen bonding into molecular design, producing a new tool for molecular recognition and self-assembly. The project is expected to impact many fields, such as drug development, separation science, environmental remediation, bioengineering, materials development, and sensing. During the course of this research, students at the graduate, undergraduate and high school levels are trained in advanced chemistry research methods. In addition, Dr. Berryman and his team will establish a permanent module at a local science museum as well as a travelling exhibit to familiarize K-8 students and members of the public with chemistry concepts. The project builds on a recent observation by Professor Berryman and his collaborators that strategically placed hydrogen bonds and halogen bonds on chain molecules synergistically induce folding into helical structures. Preliminary solution, computational and single crystal diffraction studies show that hydrogen bond enhanced halogen bonds reorganize molecular structure, strengthen binding, and are robust enough to be measured in solution. The project explores the effect of the hydrogen bond type, distance and angle on the strength, structure and directionality of the halogen bond. The specific aims of this proposal are threefold. The team seeks to quantify the influence of a proximal hydrogen bond on halogen bond strength and directionality. They will determine how halogen bonding selectivity is influenced by an intramolecular hydrogen bond. Finally, they will promote folding and anion transport with the hydrogen bond enhanced halogen bond. A suite of instrumental measurement techniques and DFT calculations will be employed to support the research effort. The mechanism causing the synergistic interaction can, in principle, be applied to pairs of noncovalent interactions other than hydrogen bonding and halogen bonding, which paves the way for the development of a set of tools for molecular engineering.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.