Valence Isomerization of the Radical Cations of Bicyclopentanes in 7-Irradiated Low-Temperature Freon Matrices

The radical cation of spiro[2.2] pentane was produced in a γ-irradiated CC1₃F matrix at 4 K. Analysis of the observed ESR spectrum has led, by a process of elimination, to the conclusion that the radical cation is probably Jahn-Teller (J-T) distorted from D₂d to C_2v. At 77 K the distorted radical cation isomerizes to the radical cation of methylene cyclobutane. Above 77 K the latter shows a reversible ESR spectral change which may be interpreted in terms of the isomerization to a nonclassical radical cation. The radical cation of bicyclo[2.1.0]pentane isomerizes even at 4 K to the radical cation of cyclopentane. The results are discussed in comparison with ab initio MO calculations.