Nanohoops as New Building Blocks for Supramolecular Chemistry
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Date
2020-02-27
Authors
Van Raden, Jeff
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
The delocalization of pi-electrons through extended carbon networks is a key design strategy to modulate the chemical and physical properties of organic molecules and materials. In addition to the extent of delocalization, the overall topology or three-dimensional geometry of the resulting molecule can have a profound impact on the resulting properties. Cycloparaphenylenes, also known as nanohoops, are a particularly illustrative example, where the fully conjugated cyclic structure results in properties that are often times in stark contrast to their linear counter parts. These electronic differences as well as their macrocyclic shape renders them as fascinating candidates for various applications in supramolecular and materials chemistry.
Chapter I provides a brief overview of the importance of template-directed synthesis in preparing complex architectures. Examples of common synthetic macrocycles will first be discussed which will then be followed with a more in-depth presentation of how the radial, yet fully conjugated cylindrical geometry of nanohoops make them distinguished building blocks for supramolecular applications. Chapter II provides a more detailed understanding of the synthetic and electronic considerations of nanohoop macrocycles. A scalable and mild synthetic approach is disclosed that allows for the preparation of a highly strained nitrogen-doped nanohoop. Using the nitrogen atom, the electronic structure is then fined tuned via alkylation. Chapter III describes the synthesis of cycloparaphenylenes that contain a metal-coordination site, a 2,2’-bipyridine, which acts as versatile handle for a variety of metal centers. Chapter IV expands on the coordination chemistry of these macrocycles; however, the ligand geometry is engineered to direct a metal to the inside of the macrocyclic cavity, which is then used to construct a new type of mechanically interlocked nanohoop structure. Chapter V discusses how other non-covalent interactions can be leveraged to construct supramolecular cylindrical assemblies, where weak arene-perfluoroarene interactions guide nanohoops into perfect cylinders. In summary, the findings discussed in this dissertation provide synthetic strategies for the selective functionalization of nanohoops and highlight this class of molecules as a novel scaffold for the design of new types of carbon nanomaterials.
This dissertation includes previously published and unpublished co-authored material.