Open-Shell and Antiaromatic Character Induced by the Highly Symmetric Geometry of the Planar Heptalene Structure: Synthesis and Characterization of a Nonalternant Isomer of Bisanthene

Konishi, Akihito; Horii, Koki; Shiomi, Daisuke; Sato, Kazunobu; Takui, Takeji; Yasuda, Makoto

doi:10.1021/jacs.9b04080

Cited by 112 publications

(93 citation statements)

References 91 publications

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“…One is the example recently published by Konishi and co‐workers, in which the PAH contains besides one azulene core, six more fused six‐membered rings. Very recently, the same group presented a small PAH that contains two fused azulene units and two additional peri ‐fused six‐membered rings, giving overall four rings . This compound shows significant biradical character.…”

Section: Methodsmentioning

confidence: 99%

Contorted Polycyclic Aromatic Hydrocarbons with Two Embedded Azulene Units

2019

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Polycyclic aromatic hydrocarbons (PAHs) that contain both five‐ and seven‐membered rings are rare, and those where these rings are annulated to each other and build azulene units have, to date, mainly been generated in minute amounts on surfaces. Herein, a rational approach to synthesize soluble contorted PAHs containing two embedded azulene units in the bulk is presented. By stepwise detachment of tert‐butyl groups, a series of three azulene embedded PAHs with different degrees of contortion has been made to study the impact of curvature on aromaticity and conjugation. Furthermore, the azulene PAHs showed high fluorescence quantum yields in the NIR regime.

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Section: Methodsmentioning

confidence: 99%

Contorted Polycyclic Aromatic Hydrocarbons with Two Embedded Azulene Units

2019

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“…The singlet open‐shell character, which often inhabits o ‐ or p ‐quinoidal subunits in polycyclic hydrocarbons, [6,21–24] is frequently associated with the aromatic or antiaromatic nature due to an inherently small HOMO‐LUMO gap [25–27] . Understanding the interrelation between open‐shell and antiaromatic characteristics is crucial to describe the nature of unique π‐conjugations [28–31] . However, in many neutral 4nπ‐systems, open‐shell and antiaromatic characteristics are incompatible in the same molecule [29,32,33] .…”

Section: Introductionmentioning

confidence: 99%

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

Konishi

Horii

Iwasa

et al. 2021

Chemistry An Asian Journal

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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 diareno[a,f]pentalene, benzo[a]naphtho[2,3‐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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“…The average bond length of the seven-membered ring was 1.418Å, slightly shorter than that found with a dibenzotropylium cation derivative (1.425Å) reported in the literature. 46 Thus, the calculated harmonic oscillator model of aromaticity (HOMA) index 47 of the seven-membered ring in BCHF1+H + (0.52) was also slightly higher than that of the dibenzotropylium cation (0.48), 46 suggesting a comparable aromatic character.…”

Section: Synthesis and Structural Characterizationmentioning

confidence: 99%