{{short description|Class of chemical compounds}} {{distinguish|text = the class of hydronitrogens known as "azenes"}} thumb|The general structural formula for acenes
In organic chemistry, the '''acenes''' or '''polyacenes''' are a class of organic compounds and polycyclic aromatic hydrocarbons made up of benzene ({{chem2|C6H6}}) rings which have been linearly fused.<ref name=GoldBook /><ref name=Bettinger /> They follow the general molecular formula {{chem2|C_{4''n''+2}H_{2''n''+4} }}.
The larger representatives have potential interest in optoelectronic applications and are actively researched in chemistry and electrical engineering. Pentacene has been incorporated into organic field-effect transistors, reaching charge carrier mobilities as high as 5 cm<sup>2</sup>/Vs.
The first unsubstituted members are listed in the following table: {| class="wikitable" ! Name ! Number of rings ! Molecular formula ! Structural formula |- | Naphthalene | 2 | {{chem2|C10H8}} | 100px |- | Anthracene | 3 | {{chem2|C14H10}} | 150px |- | Tetracene | 4 | {{chem2|C18H12}} | 200px |- | Pentacene | 5 | {{chem2|C22H14}} | 250px |- | Hexacene | 6 | {{chem2|C26H16}} | 300px |- | Heptacene | 7 | {{chem2|C30H18}} | 350px |}
Hexacene is not stable in air, and dimerises upon isolation. Heptacene (and larger acenes) is very reactive and has only been isolated in a matrix. However, bis(trialkylsilylethynylated) versions of heptacene have been isolated as crystalline solids.<ref name=anthony />
==Larger acenes== Due to their increased conjugation length the larger acenes are also studied.<ref name=bendikov /> Theoretically, a number of reports are available on longer chains using density functional methods.<ref name=wu /><ref name=Seenithurai /> They are also building blocks for nanotubes and graphene. Unsubstituted '''octacene''' (n=8) and '''nonacene''' (n=9)<ref name=Tönshoff /> have been detected in matrix isolation. The first reports of stable nonacene derivatives claimed that due to the electronic effects of the thioaryl substituents the compound is not a diradical but a closed-shell compound with the lowest HOMO–LUMO gap reported for any acene,<ref name=kaur /> an observation in violation of Kasha's rule. Subsequent work by others on different derivatives included crystal structures, with no such violations.<ref name=Purushothaman /> The on-surface synthesis and characterization of unsubstituted, parent '''nonacene''' (n=9)<ref name=zuzak /> and '''decacene''' (n=10)<ref name=Krüger /> have been reported. In 2020, scientists reported about the creation of '''dodecacene''' (n=12)<ref>{{Cite journal|last1=Eisenhut|first1=Frank|last2=Kühne|first2=Tim|last3=García|first3=Fátima|last4=Fernández|first4=Saleta|last5=Guitián|first5=Enrique|last6=Pérez|first6=Dolores|last7=Trinquier|first7=Georges|last8=Cuniberti|first8=Gianaurelio|last9=Joachim|first9=Christian|last10=Peña|first10=Diego|last11=Moresco|first11=Francesca|date=2020-01-28|title=Dodecacene Generated on Surface: Reopening of the Energy Gap|url=https://pubs.acs.org/doi/10.1021/acsnano.9b08456|journal=ACS Nano|language=en|volume=14|issue=1|pages=1011–1017|doi=10.1021/acsnano.9b08456|pmid=31829618 |issn=1936-0851|arxiv=2004.02517|bibcode=2020ACSNa..14.1011E |s2cid=209341741 }}</ref> for the first time. Four years later, in the beginning of 2024, Ruan ''et al.'' succeeded in synthesizing unsubstituted '''tridecacene''' (n=13) on a (111)-gold surface. The acene was characterized by STM- and STS-measurements.<ref>{{Cite journal |last1=Ruan |first1=Zilin |last2=Schramm |first2=Jakob |last3=Bauer |first3=John B. |last4=Naumann |first4=Tim |last5=Bettinger |first5=Holger F. |last6=Tonner-Zech |first6=Ralf |last7=Gottfried |first7=J. Michael |date=2024-01-12 |title=Synthesis of Tridecacene by Multistep Single-Molecule Manipulation |journal=Journal of the American Chemical Society |volume=146 |issue=6 |pages=3700–3709 |language=en |doi=10.1021/jacs.3c09392 |pmid=38216144 |issn=0002-7863|doi-access=free |pmc=10870776 |bibcode=2024JAChS.146.3700R }}</ref>
==Related compounds== The acene series have the consecutive rings linked in a linear chain, but other chain linkages are possible. The phenacenes have a zig-zag structure and the helicenes have a helical structure. <gallery caption="Macromolecular forms consisting of seven fused benzene rings" class="center"> File:Heptacene 200.svg|Heptacene File:7-phenacene.svg|[7]Phenacene File:M-heptahelicene.svg|''M''-heptahelicene </gallery>
[[Benz(a)anthracene|Benz[a]anthracene]], an isomer of tetracene, has three rings connected in a line and one ring connected at an angle.
==References== {{Reflist|colwidth=30em |refs= <ref name=GoldBook>{{GoldBookRef|file=A00061|title=acenes}}</ref> <ref name=anthony>{{cite journal|doi=10.1002/anie.200604045|pmid=18046697|title=The Larger Acenes: Versatile Organic Semiconductors|year=2008|last1=Anthony|first1=John E.|journal=Angewandte Chemie International Edition|volume=47|issue=3|pages=452–83 |bibcode=2008ACIE...47..452A }}</ref> <ref name=bendikov>{{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 |bibcode=2010ACIE...49.4012Z }}</ref> <ref name=wu>{{Cite journal|last1=Wu|first1=Chun-Shian|last2=Chai|first2=Jeng-Da|date=2015-05-12|title=Electronic Properties of Zigzag Graphene Nanoribbons Studied by TAO-DFT|journal=Journal of Chemical Theory and Computation|volume=11|issue=5|pages=2003–2011|doi=10.1021/ct500999m|pmid=26894252 |bibcode=2015JCTC...11.2003W |issn=1549-9618|url=http://ntur.lib.ntu.edu.tw/bitstream/246246/270528/1/index.html |url-access=subscription}}</ref> <ref name=Seenithurai>{{Cite journal|last1=Seenithurai|first1=Sonai|last2=Chai|first2=Jeng-Da|date=2016-09-09|title=Effect of Li Adsorption on the Electronic and Hydrogen Storage Properties of Acenes: A Dispersion-Corrected TAO-DFT Study|journal=Scientific Reports|language=en|volume=6|issue=1|article-number=33081|doi=10.1038/srep33081|issn=2045-2322|pmc=5016802|pmid=27609626|arxiv=1606.03489|bibcode=2016NatSR...633081S}}</ref> <ref name=Tönshoff>{{cite journal|doi=10.1002/anie.200906355|pmid=20432492|title=Photogeneration of Octacene and Nonacene|year=2010|last1=Tönshoff|first1=Christina|last2=Bettinger|first2=Holger F.|journal=Angewandte Chemie International Edition|volume=49|issue=24|pages=4125–8 |bibcode=2010ACIE...49.4125T }}</ref> <ref name=kaur>{{cite journal|doi=10.1021/ja9095472|title=Design, Synthesis, and Characterization of a Persistent Nonacene Derivative|pmid=20055388|year=2010|last1=Kaur|first1=Irvinder|last2=Jazdzyk|first2=Mikael|last3=Stein|first3=Nathan N.|last4=Prusevich|first4=Polina|last5=Miller|first5=Glen P.|journal=Journal of the American Chemical Society|volume=132|issue=4|pages=1261–3 |bibcode=2010JAChS.132.1261K }}</ref> <ref name=Purushothaman >{{cite journal|doi=10.1002/anie.201102671|title=Synthesis and Structural Characterization of Crystalline Nonacenes|pmid=21717552|year=2011|last1=Purushothaman|first1=Balaji|last2=Bruzek|first2=Matthew|last3=Parkin|first3=Sean|last4=Miller|first4=Anne-Frances|last5=Anthony|first5=John|journal = Angew. Chem. Int. Ed. Engl.|volume=50|pages=7013–7017|issue=31 |bibcode=2011ACIE...50.7013P }}</ref> <ref name=Bettinger>''Electronic structure of higher acenes and polyacene: The perspective developed by theoretical analyses'' Holger F. Bettinger Pure Appl. Chem., Vol. 82, No. 4, pp. 905–915, 2010. {{doi|10.1351/PAC-CON-09-10-29}}</ref> <ref name=zuzak>''Nonacene Generated by On-Surface Dehydrogenation'' Rafal Zuzak, Ruth Dorel, Mariusz Krawiec, Bartosz Such, Marek Kolmer, Marek Szymonski, Antonio M. Echavarren, Szymon Godlewski, ACS Nano, 2017, 11 (9), pp 9321–9329 {{doi|10.1021/acsnano.7b04728}}</ref> <ref name=Krüger>''Decacene: On-Surface Generation'' J. Krüger, F. García, F. Eisenhut, D. Skidin, J. M. Alonso, E. Guitián, D. Pérez, G. Cuniberti, F. Moresco, D. Peña, Angew. Chem. Int. Ed. 2017, 56, 11945. {{doi|10.1002/anie.201706156}}</ref> }}
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Category:Acenes Category:Conductive polymers Category:Organic semiconductors Category:Polycyclic aromatic hydrocarbons