Acenes or polyacenes is a class of organic compounds and polycyclic aromatic hydrocarbons made up of linearly fused benzene rings. 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 cm2/Vs.
The first 6 unsubstituted members are listed in table 1.
| Name | Molecular formula | Number of rings | Molar mass | CAS number | Structural formula |
|---|---|---|---|---|---|
| Naphthalene | C10H8 | 2 | 128.17 g/mol | 91-20-3 | |
| Anthracene | C14H10 | 3 | 178.23 g/mol | 120-12-7 | |
| Tetracene | C18H12 | 4 | 228.29 g/mol | 92-24-0 | |
| Pentacene | C22H14 | 5 | 278.35 g/mol | 135-48-8 | |
| Hexacene | C26H16 | 6 | 328.41 g/mol | 258-31-1 | |
| Heptacene | C30H18 | 7 | 378.46 g/mol |
The last members, hexacene and heptacene, are very reactive and have only been isolated in a matrix. However, bis(trialkylsilylethynylated) versions of hexacene and heptacene have been isolated as crystalline solids.[1]
Due to their increased conjugation length the larger acenes are also studied [2]. They are also building blocks for nanotubes and graphene. Unsubstituted octacene (n=8) and nonacene (n=9) [3] have been detected in matrix isolation. A stable nonacene derivative has also been reported [4]. 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.
A related group of compounds with 1,2-fused rings and with helical not linear structures are the helicenes. Polyquinanes and quinenes are fused cyclopentane rings.