In organic chemistry, the acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons made up of benzene () rings which have been linearly fused. They follow the general molecular formula . The larger representatives have potential interest in optoelectronic applications and are actively researched in chemistry and

electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

. Pentacene has been incorporated into organic field-effect transistors, reaching

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mobilities as high as 5 cm²/Vs. The first 5 unsubstituted members are listed in the following table: Hexacene is not stable in air, and dimerises upon isolation. Heptacene (and larger acenes) is very reactive and has only been isolated in a matrix. However, bis(trialkylsilylethynylated) versions of heptacene have been isolated as crystalline solids.

Larger acenes

Due to their increased conjugation length the larger acenes are also studied. Theoretically, a number of reports are available on longer chains using density functional methods. They are also building blocks for nanotubes and graphene. Unsubstituted octacene (n=8) and nonacene (n=9) have been detected in matrix isolation. The first reports of stable nonacene derivatives claimed that due to the electronic effects of the thioaryl substituents the compound is not a diradical but a closed-shell compound with the lowest HOMO-LUMO gap reported for any acene, an observation in violation of Kasha's rule. Subsequent work by others on different derivatives included crystal structures, with no such violations. The on-surface synthesis and characterization of unsubstituted, parent nonacene (n=9) and decacene (n=10) have been reported. In 2020, scientists reported about the creation of dodecacene (n=12) for the first time.

Related compounds

The acene series have the consecutive rings linked in a linear chain, but other chain linkages are possible. The

phenacene Phenacenes are a class of organic compounds consisting of fused aromatic rings. They are polycyclic aromatic hydrocarbons, related to acenes and helicenes from which they differ by the arrangement of the fused rings. Relevance to organic elect ...

s have a zig-zag structure and the helicenes have a helical structure. File:Heptacene 200.svg, Heptacene File:7-phenacene.svg, henacene File:M-heptahelicene.svg, ''M''-heptahelicene Benz nthracene, an isomer of tetracene, has three rings connected in a line and one ring connected at an angle.

References

{{PAHs Conductive polymers Organic semiconductors