F. Gerson et al., DIBENZO[A,E]CYCLOOCTENE - A NONPLANAR RADICAL-CATION, Journal of the Chemical Society, Chemical Communications, (14), 1994, pp. 1659-1660
Upon oxidation to the radical cation, the eight-membered ring in diben
zo[a,e]cyclooctene (2) seems to retain its tub-shaped geometry; in thi
s regard, 2 resembles the parent cyclooctatetraene 1.