Functional Metal-Ligand Assemblies: Molecular Recognition and Biomimetic Catalysis

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Professor Richard J. Hooley of the University of California-Riverside is supported by the Macromolecular, Supramolecular, and Nanochemistry (MSN) and the Chemical Catalysis (CAT) Programs of the Division of Chemistry to develop self-assembly approaches to creating new chemical structures that act in a manner similar to enzymes and to explore the potential applications of these structures in catalysis. Large biomolecules such as enzymes (a type of protein) control many cellular processes, and chemists strive to mimic their behavior with artificial analogs, but these mimics cannot approach the complexity of natural enzymes. One approach to create large, complex molecules in a rapid manner is self-assembly, whereby individual pieces are reversibly arranged to make superstructures. This project aims to develop self-assembly approaches to create new chemical structures that act in a manner similar to enzymes and to explore the potential applications of these structures in catalysis. This project provides interdisciplinary research training to a diverse group of graduate and undergraduates students in areas that bridge chemistry, biology and materials science. In the course of conducting this project, research results are incorporated in the chemistry curriculum and new courses are developed with a focus on promoting diversity and increasing retention of students in STEM fields.Self-assembled cage complexes have a wide array of applications, but their use as biomimetic catalysts is constrained by the lack of activating groups in their “active site” cavities. This project seeks to remedy this by creating synthetic receptors via metal-ligand based self-assembly that display reactive functional groups to their cavity interiors. This project focuses on three specific areas: 1) creation and host:guest properties of new self-assembled cage complexes with internally oriented acidic, basic and/or ambiphilic groups; 2) application of these cages as enzyme-mimicking catalysts, focusing on novel reactivity patterns that are not accessible with small molecule catalysts such as unusual stereochemistry in oxocarbenium ion cyclizations, and sequential tandem catalysis; 3) creation of robust covalent cage catalysts via post-assembly reaction of the reversible cages and the study of their function in protease-mimicking reactivity. An important objective in this area is to ensure that the cage catalysts are stable to a variety of reaction conditions, and can be applied in multiple different environments, including aqueous solution.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.