title: Double aromaticity and ring currents in all-carbon rings.
abstract: Double aromaticity of neutral, planar rings of carbon atoms is demonstrated through visualisation of the induced ring currents, mapped at the ipsocentric B3LYP/6-31G(d)//B3LYP/6-31G(d) level for species C(6) to C(30), with onset of delocalised current in the in-plane pi system at C(10)/C(11). Both in-plane and conventional out-of-plane pi systems have diatropic/paratropic current in accordance with the Hückel rule, with 4 m+2 occupation of the out-of-plane pi system taking precedence, as predicted by simple nesting of Frost-Musulin diagrams. The current-density maps show characteristic double-doughnut and double-track topographies for out-of-plane and in-plane ring currents, respectively, both governed by a common framework of angular momentum rules.
authors.affiliation: Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK. p.w.fowler@sheffield.ac.uk
authors.forename: Patrick W
authors.initials: PW
authors.lastname: Fowler
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Mizoguchi
authors.forename: David E
authors.initials: DE
authors.lastname: Bean
authors.forename: Remco W A
authors.initials: RW
authors.lastname: Havenith
mesh_terms: D002244:Carbon / Q000737:chemistry*; D004583:Electrons; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D008280:Magnetics; D055585:Physical Phenomena
chemical_list: D006841:Hydrocarbons, Aromatic; D002244:Carbon