Are Antiaromatic Rings Stacked Face-to-Face Aromatic?

The stacking of 4n pi electron hydrocarbon rings into superphane structures can eliminate their antiaromaticity and result in through-space three-dimensional arom. character. This is demonstrated by the bond length equalized geometries and diatropic NICS values of the methano-bridged superphane series with interacting three- to nine-membered 4n pi electron rings. Along with triplet and Moebius strategies, stacking is the third way to achieve arom. ring systems with 4n pi electrons. [on SciFinder (R)]