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Novel di-tert-butylated polycyclic aromatic hydrocarbons (PAHs) with [4] helicene components were prepared through an oxidative photocyclisation reaction. The structural properties of the PAHs were evaluated with 1H NMR and X-ray crystallography. It was detected that the PAHs have highly twisted π-conjugated systems and a deep fjord region. Although they are not planar, these PAHs can readily form dimers in solutions and undergo staggered one-dimensional array columnar crystal packing by intermolecular π–π interactions.

Various substituents have been introduced into the inner position of the dithia[3.3]metabenzenopyridinophanes (MPPs) and their conformational are evaluated by variable temperature 1H NMR spectral measurements, IR measurements, computer calculation and X-ray structural analyses.

Bis([2.2]metacyclophane) bipyridinium was synthesized for the first time and it was found that this cyclophane compound was reduced at more negative potentials than the corresponding bipyridinium, having no cyclophane skeleton, due to a transannular CH–p interaction between the aromatic ring of the cyclophane and CH portion next to nitrogen atom.

The transannular interaction between two aromatic rings of the dithia[3.3]metacyclophanediazonium salt is evaluated by several spectral measurements and the dediazoniation of the salt preferentially affords the biphenyl compound.