Dianion and Dication of Tetracyclopentatetraphenylene as Decoupled Annulene‐within‐an‐Annulene Models

Abstract

The dianion and dication of tetramesityl‐substituted tetracyclopentatetraphenylene, a circulene consisting of alternating five‐ and six‐membered rings, have been generated by reduction with alkali metals and oxidation with antimony(V) halides, respectively. They are theoretically predicted to adopt double annulenoid structures called annulene‐within‐an‐annulene models in which the outer and inner conjugation circuits are significantly decoupled. The theoretical structures were experimentally proven by X‐ray crystallographic analyses and the electronic configurations were supported by MCD spectra. Based on the 13C NMR chemical shifts, negative and positive charges are shown to be located mainly at the outer periphery, indicating that the dianion and dication have delocalized 22‐π and 18‐π electron outer perimeters, respectively, and 8‐π electron structure at the inner ring. Notably, the dianion has an open‐shell character, whereas the dication has a closed‐shell ground state.

Redox‐Active Hydrocarbons: Isolation and Structural Determination of Cationic States toward Advanced Response Systems

“…Therefore, the findings on the precise control of the intrinsic properties of organic molecules based on the manipulation of multiple redox states may lead to breakthroughs in the field of organic bulk electronic materials. Very recently, other attractive systems have also been reported in which both neutral and cationic states were successfully isolated by applying the strategies described here [128–131] . The redox chemistry of pure hydrocarbons is expanding rapidly, and these examples will be covered in another review.…”

“…Very recently, other attractive systems have also been reported in which both neutral and cationic states were successfully isolated by applying the strategies described here. [128][129][130][131] The redox chemistry of pure hydrocarbons is expanding rapidly, and these examples will be covered in another review. Furthermore, although excluded from this review, the development of pure hydrocarbon-based response systems based on different approaches from electrochemical stimulation is also being actively pursued.…”

Localized Antiaromaticity Hotspot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes

“…Rings of different size are introduced less frequentlyusually with the goal of adding structural variations. − For example, the five- and seven-membered rings introduce a positive or a negative curvature, respectively. The five-membered rings (pentagons) are particularly common at highly curved locations in polyaromatics, such as in fullerenes or caps of closed carbon nanotubes. − …”

Theoretical study on the structures, electronic properties, and aromaticity of thia[4]circulenes

“…Fortunately, DFT calculation is expected to be useful for qualitative and semiquantitative analyses of aromatic character, even for fused-ring conjugated systems showing multi-reference character and small DE ST . 104,105 3.2 Molecular orbital energy and distribution Fig. 2 shows the energy levels and distributions of the HOMOs and LUMOs of [4]circulene and the thia [4]circulenes.…”