Stacked-ring aromaticity: an orbital model.

Visualization of induced current density using the ipsocentric CHF/CTOCD-DZ/6-31G** approach gives a direct demonstration of the literature proposal of reversal of [4n]annulene antiaromaticity on stacking cyclooctatetraene (COT) rings into a superphane. Through-space interactions lead to a closed-shell in which paratropicity of planar COT units is quenched, and layered diatropic currents arise from magnetic response of two pairs of frontier orbitals. A general orbital model rationalizes the differences in current between stacked aromatic and antiaromatic rings.