Reductive bond cleavage of chloro-substituted 10-methyl- tribenzotriquinacenes: Transition between concerted and stepwise mechanisms

The electrochemical reduction of 1-chloro-, 1,4-dichloro- and 1,4,7-trichloro-10-methyl-tribenzotriquinacenes in ACN and DMF was found to occur by concerted electron transfer and bond breaking process, showing irreversible cyclic voltammetric peaks. However, the transition of the process to the stepwise mechanism upon increasing the driving force by raising the scan rate was established. Both CCl bonds are reduced successively in the dichloro compound, but only two bonds overall were reduced in the trichloro compound. The reduction mechanism is discussed. The homolytic dissociation energy of CCl bond in monochloro compound was estimated to be equal to 2.9 eV.