Acenes, consisting of linearly fused benzene rings, are an important fundamental class of organic compounds with various applications. Hexacene is the largest acene that was synthesized and isolated in the 20th century. The next largest member of the acene family, heptacene, was observed in 2007 and since then significant progress in preparing acenes has been reported. Significantly larger acenes, up to undecacene, could be studied by means of low‐temperature matrix isolation spectroscopy with in situ photolytic generation, and up to dodecacene by means of on‐surface synthesis employing innovative precursors and highly defined crystalline metal surfaces under ultrahigh vacuum conditions. The review summarizes recent experimental and theoretical advances in the area of acenes that give a significantly deeper insight into the fundamental properties and nature of the electronic structure of this fascinating class of organic compounds.

Fluorinated armchair (10,10) and zigzag (18,0) single-wall carbon nanotubes (F-SWNT) of ${\mathrm{C}}_2\mathrm{F}$ stoichiometry with five different fluorine atom decorations are studied using density-functional theory and periodic boundary conditions. The most stable armchair F-SWNT isomers $(1a$ and $5a)$ are metallic and have $\pi$ bond chains parallel to the tube axis. Isomer $5a$ carries every second fluorine atom inside the tube and is $5\hspace{0.5em}{\mathrm{kcal}\mathrm{}\mathrm{mol}}^{-1}$ more stable than $1a.$ Fluorinated zigzag tubes are not metallic. The isomer with helical zigzag conjugated $\pi$ bonds is the most stable zigzag F-SWNT, but is less stable than $1a.$ Depending on the fluorination pattern and the tube chirality, the band gaps of the F-SWNT’s vary from 2.7 to 0 eV.