| Literature DB >> 22948533 |
Zhongfang Chen1, Judy I Wu, Clémence Corminboeuf, Jonathan Bohmann, Xin Lu, Andreas Hirsch, Paul von Ragué Schleyer.
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-).Year: 2012 PMID: 22948533 DOI: 10.1039/c2cp42146a
Source DB: PubMed Journal: Phys Chem Chem Phys ISSN: 1463-9076 Impact factor: 3.676