Unusual electron density topology and intramolecular steric π-π interaction in 1,3,5,7-cyclooctatetraene

We explain the presence of the Cage Critical Point within the individual cyclooctatetraene ring as a result of the overlapping of p-type orbitals belonging to oppositely placed formally double CC bonds. This unusual ring topology is enabled by spatial arrangement of the double CC bonds in rigid skeleton of the COT ring in its natural tub-shaped conformation. Since the overlapping of the p-type orbitals may suggest some additional 'through the space' p-electron delocalization, this interaction is investigated in detail. Our results show that this interaction should be considered as a steric one and no extra stabilization from 'through the space' delocalization can be considered. (C) 2009 Elsevier B.V. All rights reserved.