ELECTROCHEMICAL OXIDATION AND STRUCTURAL-CHANGES OF 5,6-DIHYDROBENZO[C]CINNOLINES

The anodic oxidation of tetraphenylhydrazine (1) and various 5,6-dihyd robenzo[c]cinnoline derivatives (2-10) in liquid SO2 and CH2Cl2 was st udied by cyclic voltammetry at different temperatures. All compounds c ould be oxidized to their respective dications and in some cases to th eir trications. The unusual results indicate a high internal reorganiz ation energy during the first oxidation step. X-ray structure determin ations and other findings reveal that the electron transfer reactions are accompanied by structural changes of the molecular framework. The mechanism of oxidation will be dicussed in terms of different variants . Digital simulations and experimental data give strong evidence for a n E(i)E-DISP mechanism.