The Radical Ions of Dipleiadiene (Dicyclohepta[ de , ij ]naphthalene) and Its 12b,12c‐Homo Derivative. An ESR and ENDOR study

The radical anions and the radical cations of dipleiadiene (dicyclohepta[ de , ij ]naphthalene; 1 ) and its 12b, 12c‐homo derivative 2 were characterized by ESR and ENDOR spectroscopy. Their singly occupied orbitals are related to the degenerate nonbonding MOs of a 16‐membered π‐perimeter. The π‐spin distribution over the perimeter is similar in the radical cations 1 .+ and 2 .+ , and an analogous statement holds for the radical anions 1 .− and 2 .− . However, deviations of the π‐system from planarity lead to a decrease in the absolute values of the negative coupling constants of the perimeter protons in 2 .+ and 2 .− relative to those in 1 .+ and 1 .− . The hyperfine data for the perimeter protons in the radical ions correlate with the changes in 13 C chemical shifts on passing from the neutral compounds to the corresponding diions. It is concluded from the coupling constants of the CH 2 protons in the radical ions of 2 that the cation 2 .+ exists in the methano‐bridged form ( A ) of the neutral 2 (and, presumably, also of the dication 2 2+ ), whereas the anion 2 .− adopts the bisnorcaradiene form ( B ) of the dianion 2 2− .