Antiaromaticity can be characterized by the magnetic criteria (NMR chemical shifts, magnetic susceptibilities and their anisotropies): the behavior is opposite that found in aromatic systems. IGLO computations of these magnetic properties on representative 4n π electron annulenes, benzannulenes, and the bishomoantiaromatic bicyclo[3.2.1]octadienyl cation reveal paramagnetic (positive) susceptibility exaltations Λ. In contrast, aromatic compounds exhibit diamagnetic exaltations and have negative Λ’s. The paramagnetic ring currents in antiaromatic compounds also result in magnetic anisotropy enhancement, opposite in sign to their aromatic counterparts. The downfield NMR chemical shifts of Li+, complexed to the π faces of antiaromatic rings, serve as an additional probe of antiaromaticity. This behavior contrasts with the Li+ upfield shifts of their antiaromatic counterparts.
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Jiao et al. (1995) studied this question.