Indacene stability

It seems that the substituents play an essential role in the kinetic stabilization of the molecule 201 ab initio calculations for the formally anti-aromatic unsubstituted indacene shows that the minimum energy corresponds to a Dzh symmetry and a completely delocalized 12-jr-electron system.202... 

The analysis of pi-bonds distribution of eight identified isomers has shown (Fig. 3) that in isomers 4, 5, 11, 19, and 22 only corannulene (Fig. 2, a) and indacene (Fig. 2, b) substructures are present, only indacene (Fig. 2, b) substructure is possible to mark in isomer 23, and the one coronene (Fig. 2, d) in isomer 16 and the two coronene (Fig. 2, d) substructure in isomer 24 appear. This confirms our previous thesis about stabilization of coronene substructures with increase of the fullerene sizes. 

X-ray analysis of l,3,5,7-tetrakis(diethylamino)-2,6-diaza-5-indacene (17) shows it has a delocalized structure, although it belongs to the Huckel antiarenes. The theoretical predictions on the increasing delocalization and stabilization of j-indacene by donor and acceptor groups are also fullfilled in the 2,6-diaza series <88AG(E)1437>. 

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