Synthesis of [6.8]₃Cyclacene: Conjugated Belt and Model for an Unusual Type of Carbon Nanotube

Abstract

[6.8]3Cyclacene as the first hydrocarbon being a fully conjugated molecular belt has been synthesized in an eight-step reaction sequence starting from 4,6-dimethylisophthalaldehyde. It is the smallest and most strained member of the [6.8]cyclacene family, and the synthetic path offers a general route to its higher members. The structural pattern of [6.8]3cyclacene represents a model for a novel type of carbon nanotubes.

Cyclacenes and short zigzag nanotubes with alternanting Ge―C bonds: theoretical impacts of Ge on the ground state, strain, and band gap

“…They are of interest with respect to their conjugation, spectroscopic properties and cavities. They serve as possible structural motifs for carbon nanotubes (CNTs) . Cyclacene, a class of laterally fused benzoid hydrocarbons, has offered a simple conceptual framework for understanding the structure and properties of nanotube or fullerene systems because of their remarkable similarity to these structures.…”

On the Way to Carbon Nanotubes: The First Synthesis of an Aromatic Nanobelt

“…[6] [ (Figure 2; 15). [14] In this case,t he phenyl rings are also conjugated via ethenyl bridges.H owever,the whole system with its 24 p-electrons is not aromatic. In the same year,t he first synthesis of ac ycloparaphenylene (CPP) was published (Figure 2; 16) [15] but these 6 n p-electron (for [n]CPP) systems also do not show full aromaticity.…”

On the cation–π capabilities of small all sp2‐carbon host structures. Evaluation of [6.8]3cyclacene from relativistic DFT calculations

“…In this venue, a convenient approach is to provide segments that can adopt a boat‐like conformation into the belt‐like structure, as proposed by Gleiter through the evaluation and synthesis of smaller prototypical example, namely, [6.8] 3 cyclacene ( 1 ) based on an alternate fusion of 6‐ and 8‐membered rings . Such system represent one of the first examples of a pure‐fused hydrocarbon cyclacene with a resulting closed‐shell electronic structure, which envisages the characterization of higher members of the [6.8] n cyclacene family, as pointed by the authors …”