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7679738 
Journal Article 
Conformation and Aromaticity Switching in a Curved Non-Alternant sp2 Carbon Scaffold 
Zhu, C; Shoyama, K; Würthner, F 
2020 
Yes 
Angewandte Chemie (International Edition)
ISSN: 1433-7851
EISSN: 1521-3773 
WILEY-V C H VERLAG GMBH 
WEINHEIM 
59 
48 
21505-21509 
English 
32815658 
WOS:000572121000001 
A curved sp2 carbon scaffold containing fused pentagon and heptagon units (1) was synthesized by Pd-catalyzed [5+2] annulation from a 3,9-diboraperylene precursor and shows two reversible oxidation processes at low redox potential, accompanied by a butterfly-like motion. Stepwise oxidation produced radical cation 1.+ and dication 12+ . In the crystal structure, 1 exhibits a chiral cisoid conformation and partial π-overlap between the enantiomers. For the radical cation 1.+ , a less curved cisoid conformation is observed with a π-dimer-type arrangement. 12+ adopts a more planar structure with transoid conformation and slip-stacked π-overlap with closest neighbors. We also observed an intermolecular mixed-valence complex of 1⋅(1.+ )3 that has a huge trigonal unit cell [(1)72 (SbF6 )54 ⋅(hexane)101 ] and hexagonal columnar stacks. In addition to the conformational change, the aromaticity of 1 changes from localized to delocalized, as demonstrated by AICD and NICS(1)zz calculations. 
annulation; aromaticity; azulene; intermolecular mixed-valence; polycyclic aromatic hydrocarbons