Hexacene is not stable in air, anddimerises upon isolation.Heptacene (and larger acenes) is veryreactive and has only been isolated in a matrix. However, bis(trialkylsilylethynylated) versions of heptacene have been isolated as crystalline solids.[3]
Due to their increasedconjugation length the larger acenes are also studied.[4] Theoretically, a number of reports are available on longer chains using density functional methods.[5][6] They are also building blocks fornanotubes andgraphene. Unsubstitutedoctacene (n=8) andnonacene (n=9)[7] 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 adiradical but a closed-shell compound with the lowestHOMO-LUMO gap reported for any acene,[8] an observation in violation ofKasha's rule. Subsequent work by others on different derivatives included crystal structures, with no such violations.[9] The on-surface synthesis and characterization of unsubstituted, parentnonacene (n=9)[10] anddecacene (n=10)[11] have been reported. In 2020, scientists reported about the creation ofdodecacene (n=12)[12] for the first time. Four years later, in the beginning of 2024, Ruanet al. succeeded in synthesizing unsubstitutedtridecacene (n=13) on a (111)-gold surface. The acene was characterized by STM- and STS-measurements.[13]
The acene series have the consecutive rings linked in a linear chain, but other chain linkages are possible. Thephenacenes have a zig-zag structure and thehelicenes have a helical structure.
Macromolecular forms consisting of seven fused benzene rings
Heptacene
[7]Phenacene
M-heptahelicene
Benz[a]anthracene, an isomer of tetracene, has three rings connected in a line and one ring connected at an angle.
^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
^Kaur, Irvinder; Jazdzyk, Mikael; Stein, Nathan N.; Prusevich, Polina; Miller, Glen P. (2010). "Design, Synthesis, and Characterization of a Persistent Nonacene Derivative".Journal of the American Chemical Society.132 (4):1261–3.Bibcode:2010JAChS.132.1261K.doi:10.1021/ja9095472.PMID20055388.
^Purushothaman, Balaji; Bruzek, Matthew; Parkin, Sean; Miller, Anne-Frances; Anthony, John (2011). "Synthesis and Structural Characterization of Crystalline Nonacenes".Angew. Chem. Int. Ed. Engl.50 (31):7013–7017.Bibcode:2011ACIE...50.7013P.doi:10.1002/anie.201102671.PMID21717552.
^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 9321–9329doi:10.1021/acsnano.7b04728
^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
![[7]Phenacene](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3a7-phenacene.svg)
