heptacene

{{Chembox

|ImageFile = Heptaceen.png

|ImageSize = 250px

|ImageName = Skeletal formula of heptacene

|ImageFile1 = Heptacene molecule spacefill.png

|ImageSize1 = 250px

|ImageAlt1 = Space-filling model of the heptacene molecule

|PIN = Heptacene

|Section1={{Chembox Identifiers

|CASNo = 258-38-8

|UNII_Ref = {{fdacite|correct|FDA}}

|UNII = BC329D8R2F

|PubChem = 5460712

|ChemSpiderID = 4574185

|SMILES = c1cc2cc3cc4cc5cc6cc7ccccc7cc6cc5cc4cc3cc2ccc1

|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

}}

|Section2={{Chembox Properties

| C=30 | H=18

}}

}}

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.{{cite journal|doi=10.1002/anie.200906002|pmid=20468014|title=Heptacene and Beyond: the Longest Characterized Acenes|year=2010|last1=Zade|first1=Sanjio S.|last2=Bendikov|first2=Michael|journal=Angewandte Chemie International Edition|volume=49|issue=24|pages=4012–5}} This compound has long been pursued by chemists{{cite journal | doi = 10.1002/cber.19420751114| title = Heptacen ein einfacher, "ultragrüner"︁ Kohlenwasserstoff (Aromatische Kohlenwasserstoffe, XXXV. Mitteil.)| journal = Berichte der Deutschen Chemischen Gesellschaft (A and B Series)| volume = 75| issue = 11| pages = 1330–1338| year = 1942| last1 = Clar| first1 = E.}}{{cite journal | doi = 10.1021/ja01609a055| title = Cyclic Dienes. XI. New Syntheses of Hexacene and Heptacene1,2| journal = Journal of the American Chemical Society| volume = 77| issue = 4| pages = 992–993| year = 1955| last1 = Bailey| first1 = William J.| last2 = Liao| first2 = Chien-Wei}}{{cite journal | doi = 10.1039/JR9570002681| title = 519. Four higher annellated pyrenes with acene character| journal = Journal of the Chemical Society (Resumed)| pages = 2681| year = 1957| last1 = Boggiano| first1 = B.| last2 = Clar| first2 = E.}} because of its potential interest in electronic applications and was first synthesized but not cleanly isolated in 2006.{{cite journal | doi = 10.1021/ja063823i| pmid = 16866498| title = Photogeneration of Heptacene in a Polymer Matrix| journal = Journal of the American Chemical Society| volume = 128| issue = 30| pages = 9612–9613| year = 2006| last1 = Mondal| first1 = Rajib| last2 = Shah| first2 = Bipin K.| last3 = Neckers| first3 = Douglas C.}}a| Diels-Alder reaction of dibromonaphthalene forming a naphthyne and bicyclo[2,2,2]oct-2,3,5,6,7-pentaene with n-butyllithium in toluene 3 hours at -50 to -60 °C 53% chemical yield b| organic oxidation with P-chloranil in toluene 2 hours reflux and 81% yield c] Bishydroxylation with N-Methylmorpholine N-oxide and osmium tetroxide in acetone and t-butanol at room temperature for 48 hours, 83% yield d] Swern oxidation with trifluoroacetic acid in dimethyl sulfoxide and dichloromethane at -78 °C, 51% yield e] photochemical decarbonylization in a PMMA matrix at 395 nm Heptacene was finally fully characterized in bulk by researchers in Germany and the United States in 2017.{{cite journal | doi = 10.1021/jacs.6b13212| pmid = 28319405| title = Heptacene: Characterization in Solution, in the Solid State, and in Films| journal = Journal of the American Chemical Society| volume = 139| issue = 12| pages = 4435–4442| year = 2017| last1 = Einholz| first1 = Ralf| last2 = Fang| first2 = Treliant| last3 = Berger| first3 = Robert| last4 = Grüninger| first4 = Peter| last5 = Früh| first5 = Andreas| last6 = Chassé| first6 = Thomas| last7 = Fink| first7 = Reinhold F.| last8 = Bettinger| first8 = Holger F.}}

:Image:Heptacene synthesis.png{{clear left}}

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.{{cite journal | doi = 10.1021/ja901841c| pmid = 19757812| title = Synthesis, Stability, and Photochemistry of Pentacene, Hexacene, and Heptacene: A Matrix Isolation Study| journal = Journal of the American Chemical Society| volume = 131| issue = 40| pages = 14281–14289| year = 2009| last1 = Mondal| first1 = Rajib| last2 = TöNshoff| first2 = Christina| last3 = Khon| first3 = Dmitriy| last4 = Neckers| first4 = Douglas C.| last5 = Bettinger| first5 = Holger F.}} 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.{{cite journal | last1 = Einholz | first1 = R. | last2 = Bettinger | first2 = H. F. | year = 2013 | title = Heptacene: Increased Persistence of a 4n+2 π-Electron Polycyclic Aromatic Hydrocarbon by Oxidation to the 4n π-Electron Dication | journal = Angew. Chem. Int. Ed. | volume = 52 | pages = 9818–9820 | doi = 10.1002/anie.201209722 | pmid = 23873781 }}

"[Isolated] solid heptacene has a half-life time of several weeks at room temperature."{{cite journal | doi = 10.1021/jacs.6b13212| pmid = 28319405| title = Heptacene: Characterization in Solution, in the Solid State, and in Films| journal = Journal of the American Chemical Society| volume = 139| issue = 12| pages = 4435–4442| year = 2017| last1 = Einholz| first1 = Ralf| last2 = Fang| first2 = Treliant| last3 = Berger| first3 = Robert| last4 = Grüninger| first4 = Peter| last5 = Früh| first5 = Andreas| last6 = Chassé| first6 = Thomas| last7 = Fink| first7 = Reinhold F.| last8 = Bettinger| first8 = Holger F.}}