π-Spin distribution in the radical anion of benzo[2.2]paracyclophane and its relation to those in the radical anions of [2.2](1,4)naphthalenophanes

Radical anions of benzo[2.2]paracyclophane (V) and its 1,2,12,12,14,15,17,18-octadeuterio derivative (V-d₈) in three ethereal solvents (DME, THF and MTHF) and in the temperature range of ?90 to ?50° have been studied by ESR. and ENDOR. spectroscopy. The resulting hyperfine data provide a detailed picture of the π-spin distribution in V · ? which is in full accord with expectation. In particular, it is noteworthy that the naphthalene moiety accommodates almost the entire π-spin population, as may be anticipated by the higher electron affinity of this π-system relative to benzene. The proton coupling constants for V · ? have been compared with those values for the radical anions of anti- and syn-[2.2](1,4)-naphthalenophanes (II and III, respectively) which were obtained under conditions of low frequency electron transfer between the two equivalent naphthalene moieties. Such a comparison corroborates the interpretation of the results reported previously for II · ? and III · ?.