Fullerene local ring currents

The aromatic character of fullerene anions can be better understood by monitoring the local ring currents of the 5-membered rings (5MRs) and 6-membered rings (6MRs) in... 

The enhancement of the diamagnetic susceptibility caused by a ring current is not an isotropic effect but occurs only when the plane of the ring is oriented perpendicular to the external magnetic field. Consequently, the presence or absence of a pronounced anisotropy A% can, in principle, be taken as evidence for or against a ring current and can thus be employed as an aromaticity probe. The need to correct for local anisotropy effects of single and multiple bonds, however, and limitations in the experimental determination of have impeded widespread applications of this property. Moreover, for spherical molecules such as fullerenes, this criterion cannot be sensibly applied at all. 

Are fullerenes aromatic In this review we have attempted to summarize the current state of research related to this question. The classical criteria for aromaticity of planar, unsaturated compounds, namely, those based on structure, energetics, reactivity, and magnetic properties, are applied to fullerenes and their derivatives. Magnetic and NMR properties are probably the most general indicators for aromaticity, and the wealth of accumulated data clearly demonstrates that extensive cyclic delocalization of ji electrons takes place in fullerenes. The observed properties are often the result of the simultaneous presence of locally diatropic and paratropic ring currents. 

---