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 13 C 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,

Synthesis and crystal structure of 2,9-diamino-5,6,11,12-tetrahydrodibenzo[a,e]cyclooctene

“…An overview of 6,8,6 ring systems can be found in Domiano et al (1992). The 6,8,6 motif also appears in circulene systems, see Miyoshi et al (2022).…”