Detection of phenyl-substituted radical cations derived from cyclopentyl- and urazole-type azoalkanes by pulse radiolysis, influence of heteroatom substitution on the radical cation reactivities

The radical cations of cyclopentane- and urazole-annelated azoalkanes and housanes were generated by pulse radiolysis and the transients characterized spectrally and kinetically by time-resolved optical monitoring. For the bridgehead-substituted diphenyl derivatives of the cyclopentane-annelated azoalkane 1 and housane 2 only the corresponding proximate 1,2 radical cation species were observed, generated from the initially formed and too short-lived (<1 mu s) distonic 1,3 radical cation by 1,2-methyl migration, In contrast, for the corresponding urazole-annelated azoalkanes 4, the-initial distonic 1,3 radical cations 5(.+) were detected, and of these the methyl-substituted 5b(.+) deprotonates to the radical 5b(.).