The Benzenium Ion − Aromatic as the π-Complex or Antiaromatic as the σ-Complex Being Something Similar to the Cyclopentadienyl Cation?

The spatial magnetic properties, through-space NMR shieldings (TSNMRSs), of the benzenium cation (C6H7+) 1 and of ±I/M-substituted analogues C6H6X+ 3–8 [X = −Me, −CF3, −NH2, −NO2, −NO, −SiH3] have been calculated using the gauge-independent atomic orbital perturbation method employing the nucleus-independent chemical shift concept, and iso-chemical-shielding surfaces of various sizes and directions have been observed. The TSNMRS values were employed to compare the spatial magnetic properties (TSNMRS) of benzene and the benzenium ion 1 and then further compared with analogues 3–8, to answer the question whether the electronic structures of 1 and 3–8 are still similar to those of aromatic species or somewhat similar to the antiaromatic cyclopentadienyl cation 2, supported by structural data and δ(13C)/ppm values.