Direct Characterization of Hexamethyl(Dewar Benzene) Radical Cation by Electronic Absorption Spectroscopy

The electronic absorption spectrum of the hexamethyl(Dewar benzene) radical cation ( 1 • + ) is presented for the first time. Partial stabilization of 1 • + in organic glasses at cryogenic temperatures is explained in terms of matrix rigidity, which can inhibit the isomerization process. Annealing of the matrix leads to fast isomerization of 1 • + to hexamethylbenzene radical cation ( 2 • + ) and, at high concentrations of 1, formation of the hexamethylbenzene dimer radical cation can be observed.