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Conformation and Aromaticity Switching in a Curved Non‐Alternant sp 2 Carbon Scaffold
Author(s) -
Zhu Chongwei,
Shoyama Kazutaka,
Würthner Frank
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202010077
Subject(s) - aromaticity , chemistry , dication , crystallography , delocalized electron , dimer , crystal structure , valence (chemistry) , ion , molecule , organic chemistry
A curved sp 2 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 1 2+ . 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. 1 2+ 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 (SbF 6 ) 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.