Heptacene is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

and a

polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...

and the seventh member of the

acene 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 represent ...

or polyacene family of linear fused benzene rings. This compound has long been pursued by chemists because of its potential interest in electronic applications and was first synthesized but not cleanly isolated in 2006. Heptacene was finally fully characterized in bulk by researchers in Germany and the United States in 2017. : The final step is a

photochemical Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400–7 ...

decarbonylization with a 1,2-dione bridge extruded as

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

. In solution heptacene is not formed because it is very unstable being a reactive DA diene and quickly reacts with oxygen or forms

dimer Dimer may refer to: * Dimer (chemistry), a chemical structure formed from two similar sub-units ** Protein dimer, a protein quaternary structure ** d-dimer * Dimer model, an item in statistical mechanics, based on ''domino tiling'' * Julius Dimer ...

s. When on the other hand the dione precursor is dissolved in a

PMMA PMMA may refer to: * para-Methoxymethamphetamine, a stimulant drug * Philippine Merchant Marine Academy The Philippine Merchant Marine Academy ( fil, Akademiya sa Bapor Pangkalakalan ng Pilipinas) also referred to by its acronym PMMA) is a ma ...

matrix first, heptacene can be studied by spectroscopy. Heptacene has been studied spectroscopically at cryogenic temperatures in a

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** ''The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchis ...

. When dissolved in sulfuric acid the heptacene dication is reported to be stable at room-temperature for more than a year in absence of oxygen. " solatedsolid heptacene has a half-life time of several weeks at room temperature."

Derivatives

: : 7,16-Bis(tris(trimethylsilyl)silylethynyl)heptacene was synthesized in 2005. This compound is stable in the solid state for a week but decomposes in contact with air. Its synthesis started from

anthraquinone Anthraquinone, also called anthracenedione or dioxoanthracene, is an aromatic organic compound with formula . Isomers include various quinone derivatives. The term anthraquinone however refers to the isomer, 9,10-anthraquinone (IUPAC: 9,10-dioxoan ...

and naphthalene-2,3-dicarboxaldehyde. More stable substituted heptacenes have been reported: with stabilizing ''p''-(''t''-butyl)thiophenyl substituents (Figure 1) and with phenyl and triisopropylsilylethynyl groups (Figure 2).

References

{{PAHs Acenes Polycyclic aromatic hydrocarbons Substances discovered in the 2000s