Helicenes, which consist of <i>ortho</i>-fused aromatic rings, represent a unique class of polyaromatic compounds combining the nonplanarity with structural flexibility and inherent chirality. Multiple helicenes with two or more helicene moieties fused together in one polyaromatic hydrocarbon framework have been recently reported and gained significant attention due to their contorted three-dimensional structures, multiple chiral states, as well as their applications in organic electronic devices. By introducing heteroatoms or smaller rings to the helicene core, the helicity, local aromaticity, as well as stability and reactivity of the <i>π</i>-systems can be effectively modulated. Helicenes can also serve as multi-electron reservoirs but their potential for storing multiple electrons has not yet been revealed. Since no electron acquisition and chemical reactivity studies of the helicenes have been reported, we initiated a broad investigation of their stepwise chemical reduction processes, using alkali metals as reducing agents. A number of single and double helicenes, including the heteroatom-doped systems, have been selected for this study for comparison. Several new products of stepwise reduction reactions have been isolated and fully characterized, using X-ray crystallographic and spectroscopic tools. The direct X-ray structural comparison with the parent helicenes allowed us to fully reveal the consequences of electron addition on geometry perturbation and transformation of the helicenic core. These results as well as metal binding trends will be discussed and compared for several selected helicenes.

Structural consequences of adding multiple electrons to helicenes

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.