Heptacene

Heptacene is an organic compound and a polycyclic aromatic hydrocarbon and the seventh member of the acene or polyacene family of linear fused benzene rings.^[1] This compound has long been pursued by chemists^[2][3][4] because of its potential interest in electronic applications and was first synthesized but not cleanly isolated in 2006.^[5][6] Heptacene was finally fully characterized in bulk by researchers in Germany and the United States in 2017.^[7]

heptacene synthesis

Heptacene

Skeletal formula of heptacene
Names
Preferred IUPAC name Heptacene
Identifiers
CAS Number	258-38-8
3D model (JSmol)	Interactive image
ChemSpider	4574185
PubChem CID	5460712
UNII	BC329D8R2F Y
CompTox Dashboard (EPA)	DTXSID50420113
InChI InChI=1S/C30H18/c1-2-6-20-10-24-14-28-18-30-16-26-12-22-8-4-3-7-21(22)11-25(26)15-29(30)17-27(28)13-23(24)9-19(20)5-1/h1-18H
SMILES c1cc2cc3cc4cc5cc6cc7ccccc7cc6cc5cc4cc3cc2ccc1
Properties
Chemical formula	C30H18
Molar mass	378.474 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The final step is a photochemical decarbonylization with a 1,2-dione bridge extruded as carbon monoxide. In solution heptacene is not formed because it is very unstable being a reactive DA diene and quickly reacts with oxygen or forms dimers. When on the other hand the dione precursor is dissolved in a PMMA matrix first, heptacene can be studied by spectroscopy. Heptacene has been studied spectroscopically at cryogenic temperatures in a matrix.^[8] 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.^[9] "[Isolated] solid heptacene has a half-life time of several weeks at room temperature."^[10]

Derivatives

Figure 1.

Figure 2.

7,16-Bis(tris(trimethylsilyl)silylethynyl)heptacene was synthesized in 2005.^[11] This compound is stable in the solid state for a week but decomposes in contact with air. Its synthesis started from anthraquinone and naphthalene-2,3-dicarboxaldehyde. More stable substituted heptacenes have been reported: with stabilizing p-(t-butyl)thiophenyl substituents (Figure 1)^[12] and with phenyl and triisopropylsilylethynyl groups (Figure 2).^[13]