Synthesis of cyclopenta-fused aromatic hydrocarbon radicals

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Conjugated systems, which alternately contain benzene and cyclopentadiene moieties (cyclopenta-fused polyaromatic hydrocarbons, CP-PAHs), are known for their special properties, making them, e.g., suitable for utilization in optoelectronic applications. CP-PAHs containing an odd number of five-membered rings are in their neutral state radicals. In this project radicalic CP-PAHs shall be synthesized by ortho-coupling in ortho-carboxyl- or ortho-formyl-substituted oligophenyls. The resulting intermediates shall be transferred into the conjugated CP-PAHs by oxidative or reductive methods. Side reactions at the radical centers can be prevented by bulky aryl substituents at the cyclopentadienes. Higher CP-PAHs should favorably be constructed starting with oligoaryls containing fluorene moieties. Methods are described for the synthesis of CP-PAHs containing up to eleven rings. The target compounds shall be investigated (partly in cooperation with other groups) with respect to their aromatic, electronic, and magnetic properties and their redox activities. The experimental analytical methods will be supported by quantum chemical calculations.