Novel Synthetic Design and Methods for Atomically Precise Nanographenes

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Atomically precise nanographenes and related structures have gained significant importance in several areas of chemistry and materials science due to their unmatched optoelectronic properties. Yet, their full potential has not yet been exploited as several types of very promising structures cannot yet be prepared efficiently due to the lack of synthetic methods. The central objective of our research program is to develop innovative and versatile synthetic tools for the preparation of unprecedented, well-defined nanographenes (NGs), graphene nanoribbons (GNRs) and carbon allotropes with unique physical properties. This proposal is separated into four related themes: 1. Metal-free photochemical reaction for intramolecular C-C coupling; 2. GNRs and other one-dimensional carbon allotropes; 3. Zigzag-edged NGs and GNRs; 4. Conjugated molecules with a high diradical character. As a short- to medium-term project, we will pursue our efforts in the development and study of a reaction called the cyclodehydrochlorination (CDHC) for the preparation of NGs, GNRs and new carbon allotropes of different topologies by following three strategies. Our medium- to long-term goal will be to use this method to prepare unprecedented topologies of sought-after armchair GNRs whose synthesis is not yet possible using known wet chemistry strategies. Also, low bandgap, one-dimensional carbon allotropes with 5- and 7-membered rings will be prepared. The best candidates will be integrated as active materials in organic electronics devices. Another medium-term objective is to prepare long, stable zigzag-edged nanographenes with low bandgap. We propose an innovative approach that consists of using short, stable zigzag-edged molecules, such as naphthalene and pyrene, as building blocks to prepare longer analogs. Short, definite-length model compounds will be prepared using different synthetic approaches to study their stability and the relationships between their structures and properties. Our long-term goal is to synthesize zigzag-edged GNRs and evaluate their singlet fission properties. NGs and GNRs will be used as scaffolds to prepare molecules with a high diradical character. We propose to generate diradicals "on demand" in various NGs and GNRs by using tunable steric hindrance through coordination chemistry with metals within the aromatic skeleton. The discoveries that will be made using our innovative approaches will have a significant impact on physical organic chemistry and materials science. This research program is based on our long-standing expertise in the area of aromatic compounds and fits perfectly with our long-term objective, which is to have a access to unorthodox carbon-rich molecules and materials that could surpass the best-known materials in electronics applications.