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

Abstract

Abstract Radical anions of benzo[2.2]paracyclophane (V) and its 1,2,12,12,14,15,17,18‐octadeuterio derivative (V‐d 8 ) 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 · ⊖.