The dynamic, size-dependent properties of [5]-[12]cycloparaphenylenes.

[n]Cycloparaphenylenes (or "carbon nanohoops") are cyclic fragments of carbon nanotubes that consist of n para linked benzene rings. These strained, all sp(2) hybridized macrocycles, have size-dependent optical and electronic properties that are the most dynamic at the smallest size regime where n = 5-12. This review highlights the unique physical phenomena surrounding this class of polycyclic aromatic hydrocarbons, specifically emphasizing the novel structural, optical, and electronic properties of [5]-[12]CPPs.