Baird’s rule

The ground-state minimal energy strucmre of COT is a non-aromatic and non-planar species that is not so interesting from Baird s rule perspective. For this reason, we have chosen the planar COT, which is not an energy minimum but is a stationary point of the potential energy surface with bond-length alternation and well-known antiaromatic character. 

Zhu J, Fogarty HA, Mollerstedt H, Brink M, Ottosson H (2013) Aromaticity effects on the profiles of the lowest triplet-state potential-energy surfaces for rotation about the C=C bonds of olefins with five-membered ring substituents an example of the Impact of Baird s rule. Chem Eur J 19 10698-10707... 

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