Aromatic character studies on calicene and calicene-like containing heavier atoms via nuclear independent chemical shifts (NICS)

Calicene, triapentafulvalene, cyclopropenylidenecyclopenta-diene, is a completely conjugated unsaturated molecule. Two rings of the calicene, connected by a double bond, can be shown to have an aromatic character with a dipolar electronic structure. This molecule has never been synthesized but the substituted species show quite high dipole moments [1,2]. Theoretical calculations have been carried out for calicene [3-7]. Semi-empirical SCF MO calculations have been done for calicene and its various possible benzo derivatives [3]. As continuation on our works [8], in this manuscript, the aromatic character was calculated for calicene and calicene-like containing heavy atoms through nuclear independent chemical shifts (NICS) calculations.