Heptacene

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. 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. "[Isolated] solid 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 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).