{{Chembox |ImageFile = Heptacene 200.svg |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.<ref>{{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}}</ref> This compound has long been pursued by chemists<ref>{{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.}}</ref><ref>{{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}}</ref><ref>{{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.}}</ref> because of its potential interest in electronic applications and was first synthesized but not cleanly isolated in 2006.<ref>{{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.}}</ref><ref>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</ref> Heptacene was finally fully characterized in bulk by researchers in Germany and the United States in 2017.<ref>{{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.}}</ref>
:300px|left|heptacene synthesis{{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.<ref>{{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.}}</ref> 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.<ref>{{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 }}</ref> "[Isolated] solid heptacene has a half-life time of several weeks at room temperature."<ref>{{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.}}</ref>
== Derivatives == :thumb|Figure 1. :thumb|Figure 2. 7,16-Bis(tris(trimethylsilyl)silylethynyl)heptacene was synthesized in 2005.<ref>{{cite journal|doi=10.1021/ja051798v|title=Functionalized Higher Acenes: Hexacene and Heptacene|year=2005|last1=Payne|first1=Marcia M.|last2=Parkin|first2=Sean R.|last3=Anthony|first3=John E.|journal=Journal of the American Chemical Society|volume=127|pages=8028–9|pmid=15926823|issue=22}}</ref> 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)<ref>{{cite journal|doi=10.1021/ja808881x|pmid=19243093|title=Exploiting Substituent Effects for the Synthesis of a Photooxidatively Resistant Heptacene Derivative|year=2009|last1=Kaur|first1=Irvinder|last2=Stein|first2=Nathan N.|last3=Kopreski|first3=Ryan P.|last4=Miller|first4=Glen P.|journal=Journal of the American Chemical Society|volume=131|issue=10|pages=3424–5}}</ref> and with phenyl and triisopropylsilylethynyl groups (Figure 2).<ref>{{cite journal|doi=10.1002/anie.200803345|pmid=18825763|title=The Most Stable and Fully Characterized Functionalized Heptacene|year=2008|last1=Chun|first1=Doris|last2=Cheng|first2=Yang|last3=Wudl|first3=Fred|journal=Angewandte Chemie International Edition|volume=47|issue=44|pages=8380–5}}</ref>
==References== {{Reflist|2}} {{PAHs}} {{Hydrocarbons}}
Category:Acenes Category:Polycyclic aromatic hydrocarbons Category:Substances discovered in the 2000s