Known for over a century, [n]helicenes have attracted the attention of chemists because of their intriguing physical properties. Ortho-fusion of n aromatic rings builds up the rigid helix in this class of molecules. The chiral properties of [n]helicenes were not only studied extensively on the single-molecular level using STM techniques,[1] but even more attention was paid to the chiroptical properties of [n]helicenes with their strong Cotton effects.[2] Not surprisingly, the chiroptical properties vary with the number of fused rings n. But only recently, it was shown that the circular dichroism response can be reversibly switched in the same molecule by the attachment of a redox-active ruthenium center to a [6]helicene.[3] In this contribution, we present the synthesis and characterization of a new helicene quinone, which is analyzed in the context of electrochemically switching of chiroptical properties. Furthermore, we were able to characterize the semiquinone radical anion with a combination of EPR spectroscopy, ENDOR spectroscopy, and DFT calculations. [1] Shchyrba A.; Nguyen M.-T.; W�ckerlin C.; Martens S.; Nowakowska S.; Ivas T.; Roose J.; Nijs T.; Boz S.; Sch�r M.; St�hr M.; Pignedoli C. A.; Thilgen C.; Diederich F.; Passerone D.; Jung T. A. J. Am. Chem. Soc. 2013  , 135, 15270.[2] Roose J.; Achermann S.; Dumele O.; Diederich F. Eur. J. Org. Chem. 2013 , 3223.[3] Anger E.; Srebro M.; Vanthuyne N.; Toupet L.; Rigaut S.; Roussel C.; Autschbach J.; Crassous J.; R�au R. J. Am. Chem. Soc. 2012  , 134, 15628.

Helicenes: Redox switching of chiroptical properties

248th National Meeting (2014)

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