title: Is C60 buckminsterfullerene aromatic?
abstract: C(60) does not have "superaromatic" or even aromatic character, but is a spherically π antiaromatic and enormously strained species. This explains its very large and positive heat of formation (610 ± 30 kcal mol(-1)). The π electron character of C(60) was analyzed by dissected nucleus independent chemical shifts (NICS). The results were employed to examine the scope and limitations of Hirsch's 2(N + 1)(2) spherical aromaticity rule for several globular cages. C(20)(2+) (18 π electrons) and C(60)(10+) (50 π electrons) are spherically π aromatic, but C(20) (20 π electrons) and C(60) (60 π electrons) are spherically π antiaromatic, due to the high paratropicity of their half-filled π subshells. Limitations for Hirsch's rule, for clusters with more than 50 π electrons, are illustrated by e.g. the π aromaticity of the 66 π electron C(60)(6-) and the lack of π aromaticity of the 72 π electron C(48)N(12) and C(60)(12-).
authors.affiliation: Department of Chemistry, University of Puerto Rico, San Juan, PR 00931. zhongfangchen@gmail.com
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Chen
authors.forename: Judy I
authors.initials: JI
authors.lastname: Wu
authors.forename: Clémence
authors.initials: C
authors.lastname: Corminboeuf
authors.forename: Jonathan
authors.initials: J
authors.lastname: Bohmann
authors.forename: Xin
authors.initials: X
authors.lastname: Lu
authors.forename: Andreas
authors.initials: A
authors.lastname: Hirsch
authors.forename: Paul von Ragué
authors.initials: Pv
authors.lastname: Schleyer