A diindenophenanthrene biradicaloid, formally derived from Chichibabin's hydrocarbon, is obtained in a short, scalable synthesis. The present system is electron-rich and devoid of conjugated substituents, and still exhibits very good stability under ambient conditions. The introduction of the diindeno[1,2-a:2′,1′-i] phenanthrene ring framework results in a singlet biradicaloid system with an easily accessible triplet state (ΔES-T = −1.30 kcal mol−1) and a small electronic bandgap (1.39 V). The stability limits of the title hydrocarbon were explored systematically in the solid state, to reveal an unusual thermally initiated hydrogen-scrambling oligomerization process.
Bibliographical noteFunding Information:
Financial support from the National Science Center of Poland (DEC-2012/07/E/ST5/00781 to M. S. and DEC-2015/19/N/ST5/ 00760 to M. A. M.) and the Foundation for Polish Science (START fellowship to M. A. M.) is gratefully acknowledged. Quantum chemical calculations were performed in the Wrocław Center for Networking and Supercomputing. P. M. Z. thanks the Alfred P. Sloan Foundation for support of this project. The work at Yonsei University was supported by Strategic Research (NRF-2016R1E1A1A01943379) through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT (Information and Communication Technologies) and Future Planning. We thank Prof. Frank Würthner (Würzburg), Dr Yi-Lin Wu (Northwestern University), and anonymous referees for helpful comments.
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