Organic radical cations in fluid solution: Unusual structures and rearrangements.

Many intrinsically unstable radical cations derived from strained hydrocarbons can be generated as shortlived intermediates by electron transfer to photoexcited electron acceptors in polar solvents. Nuclear spin polarization effects observed during these reactions provide insight into radical cation structures and the mechanisms of their reactions. In particular, unprecedented "non-vertical" and homoaromatic structures have been established and the mechanisms of radical cation rearrangements, cycloadditions and fragmentations have been elucidated.