Aromatization of rings of fulvene and heptafulvene due to the through space interactions in [34]3,4,6,6-fulvene-4,5,8,8-heptafulvene-cyclophane

Two non-aromatic molecules, fulvene and heptafulvene gain aromaticity when positioned parallelly to each other in a cyclophane-like molecule. Four aliphatic linkers are employed to hold the two rings together and the distance between them in the structure optimized at the MP2/6-31G(d) level of theory equals to 3.337 Å. Calculations show that through-space charge transfer occurs from heptafulvene to fulvene ring leading to an increase of aromaticity which is documented by geometry based index HOMA and magnetic based index NICS. When fulvene and heptafulvene are forced to approach each other directly, without linkers, the most effective changes in aromaticity are observed at much shorter distance 2.1–2.2 Å and they are much larger than those observed for the cyclophane system.