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Post-synthetic Modification of Nanographenes using C-H Activation and Alkyne Benzannulation
AdvisorChalifoux, Wesley A.
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“Bottom-up” (BU) synthetic strategies have now given chemists the tools to further modify large polycyclic aromatic hydrocarbon (PAH) molecules in a relatively straightforward man-ner. A powerful BU technique is alkyne benzannulation as it allows for the reliable prepara-tion of pyrenacene (pyrene, peropyrene, teropyrene, etc.) molecules in high yield. Coupling this strategy with the postsynthetic modification of nanographene’s (NG) is a relatively new area of interest in the world of materials chemistry. Edge functionalization is the most pre-dominant method regarding postsynthetic modification as it allows the change of shape, electronics, and chirality of the NG to occur. In this work, we have developed new methods to successfully elongate the size of pyrenacene NGs with the use of iridium catalyzed C-H bond activation to make dissymmetric chiral peropyrenes, and the longest atomically precise oligomeric graphene nanoribbon (GNR) fragment. Additionally, the C-H activation of a complex pyrene molecule allowed us to prepare two dissymmetrical chiral peropyrenes that were separated by high-performance liquid chromatography (HPLC) and were both studied for their photophysical and electrochemical properties. Lastly, we were able to successfully brominate the starkly unresearched teropyrene in excellent yields using extant electrophilic aromatic substation (EAS) techniques that required no further purification upon completion. This tetra-brominated species was then further functionalized via Stille C-C coupling reac-tions resulting in the preparation of backbone functionalized teropyrene derivatives that led to near red-light absorbing NGs. Additionally, a single crystal was grown to unambiguously prove structure of one of the teropyrene derivatives.