A Stable Saddle‐Shaped Polycyclic Hydrocarbon with an Open‐Shell Singlet Ground State

Diindeno‐fused bischrysene, a new diindeno‐based polycyclic hydrocarbon (PH), was synthesized and characterized. It was elucidated in detailed experimental and theoretical studies that this cyclopenta‐fused PH possesses an open‐shell singlet biradical structure in the ground state and exhibits high...

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Published in:Angewandte Chemie International Edition 2017-03, Vol.56 (12), p.3280-3284
Main Authors: Ma, Ji, Liu, Junzhi, Baumgarten, Martin, Fu, Yubin, Tan, Yuan‐Zhi, Schellhammer, Karl Sebastian, Ortmann, Frank, Cuniberti, Gianaurelio, Komber, Hartmut, Berger, Reinhard, Müllen, Klaus, Feng, Xinliang
Format: Article
Language:English
Subjects:
aromaticity
biradicals
Crystal structure
electronic structure
Hydrocarbons
polycyclic hydrocarbons
saddle conformation
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Summary:Diindeno‐fused bischrysene, a new diindeno‐based polycyclic hydrocarbon (PH), was synthesized and characterized. It was elucidated in detailed experimental and theoretical studies that this cyclopenta‐fused PH possesses an open‐shell singlet biradical structure in the ground state and exhibits high stability under ambient conditions (t1/2=39 days). The crystal structure unambiguously shows a novel saddle‐shaped π‐conjugated carbon skeleton due to the steric hindrance of the central cove‐edged bischrysene unit. UV/Vis spectral measurements revealed that the title molecule has a very narrow optical energy gap of 0.92 eV, which is consistent with the electrochemical analysis and further supported by density functional theory (DFT) calculations. Stay in the saddle: A curved polycyclic hydrocarbon synthesized by extending the twisted bischrysene core by two indene units displayed a stable singlet biradical structure in the ground state. X‐ray crystallographic analysis clearly revealed its saddle‐shaped conformation.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201611689