Characterization of Benzo[a]naphtho[2,3-f]pentalene: Interrelation between Open-shell and Antiaromatic Characters Governed by Mode of the Quinoidal Subunit and Molecular Symmetry |
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Authors: | Dr Akihito Konishi Koki Horii Haruna Iwasa Yui Okada Dr Ryohei Kishi Prof Dr Masayoshi Nakano Prof Dr Makoto Yasuda |
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Institution: | 1. Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, 565-0871 Japan;2. Department of Materials Engineering Science, Graduate School of Engineering Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka, 560-0043 Japan;3. Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI), Osaka University, Suita, Osaka, 565-0871 Japan |
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Abstract: | The singlet open-shell character and antiaromaticity are intriguing features in π-conjugated carbocycles. These two exhibit similar chemical and physical properties. However, they rarely coexist in the same molecule. Understanding the interrelation between the open-shell and antiaromatic characteristics in the same molecule is crucial to control the electronic properties. Herein we describe the synthesis and characterization of a new member of diarenoa,f]pentalene, benzoa]naphtho2,3-f]pentalene 6 . Unlike its isomer 5 with a closed-shell ground state, 6 exhibits an appreciable open-shell character and a moderate antiaromatic feature. The behaviors of the open-shell index (y0) against the difference of the proton chemical signal (Δδ(H1)) between pentalenide dianions/neutral pentalenes for our reported pentalenes 1 , 4 , 5 , and 6 give a thought-provoking conclusion about the interrelation between open-shell and antiaromatic characteristics in this series. The mode of the incorporated quinoidal moiety and the formal molecular symmetry are critical to balance these two characteristics. |
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Keywords: | antiaromaticity open-shell character pentalene polycyclic hydrocarbon non-alternant hydrocarbon |
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