Cavitands and Self-Assembled Capsules as Supramolecular Reagents and Organo-Catalysts

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For several decades now, chemists have been learning from Nature how to harness the intrinsic properties of molecules to "self-assemble" into complex arrays that possess novel properties quite independent of the original components. This research program of Prof. Bruce Gibb at Tulane University utilizes bowl-shaped molecules in assembly processes that form novel chemical reactors. Although akin to the familiar test-tube, these chemical reactors are exceedingly small. Much like Nature's catalysts - enzymes - these reactors are capable of trapping one molecule at a time to bring about novel and selective chemical transformations. Additionally, the program of research is designed to improve our understanding of chemical transformations using exceedingly mild conditions (e.g., room temperature water). This research is important to society because it addresses national needs in sustainability. The use of room temperature water helps to reduce energy cost for production of chemicals and avoid environmental issues associated with the use of organic solvents. Broader impacts of the research include education and training of graduate and undergraduate students as the next generation of productive members and leaders in the chemical sciences, as well as outreach activities designed to promote chemistry within the local community and to broaden participation in science and engineering fields.The state-of-the-art of supramolecular chemistry has now reached a point that the construction of (supra)molecular containers is relatively facile. Building on this, a significant aim of this program of research is to consider how electrostatic potential fields within nano-spaces can be engineered, and in doing so, how it is possible to control guest reactivity and catalysis within the nano-space. This program of research focuses on three classes of chemical conversions (cyclization reactions, stereoselective halogenation of carbon-carbon double bonds, and halogenation of aromatic compounds) using cavitands and deep-cavity cavitands as scaffolds and hosts. All of the chemical conversions being studied utilize water as the solvent and take advantage of the hydrophobic effect to drive guest complexation and/or promote turnover.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.