The ESR. Spectrum of the Radical Anion of 1,1,2,2,9,9,10,10‐Octafluoro [2.2]paracyclophane

The radical anion of 1,1,2.2,9,9,10, 10‐octafluoro[2.2]paracyclophane ( 1 ) has been generated by electrolytic reduction of 1 in 1,2‐dimethoxyethane (tetrabutylammonium perchlorate as the supporting salt). The hyperfine coupling constants of the eight 19 F‐nuclei and the eight protons, a f = 3.35 and a H ≈ 0.10 mT, are qualitatively reproduced by INDO. calculations. According to these calculations, the singly occupied orbital of 1 ⊖ can be represented by an A g ‐combination of two ‘symmetric’ benzene LUMO's, with a substantial transfer of spin population into the 2s‐AO's of the F‐atoms. Line‐width alternation in the ESR. spectrum of 1 ⊖ indicates an ion pairing of the radical anion with its counter‐ion Bu 4 N ⊖ . The energy barrier to the migration of the cation between two equivalent sites at the radical anion is determined as 14±2 kJ/mol.