Triphenylamine derivatives react with Cu2+ in acetonitrile to give radical cations. which Subsequently Undergo dimerization to provide tetraphenylbenzidine derivatives. Kinetic aspects of radical cation formation were examined by stopped-flow spectrophotometry. A broad range of triphenylamine derivatives Were studied, and the driving force for the electron-transfer reaction ranged from +3.67 to -8.56 kcal M-1 with rate constants varying from 1.09 x 10(2) to 2.15 x 10(5) M-1 s(-1) for these systems. Reorganization energy for the electron-transfer reaction was estimated using experimentally determined activation parameters. Filling of the rate data to the Marcus equation using different values of the electronic coupling matrix element H-el provided a good fit with H-el = 100 cm(-1) suggesting that electron transfer in the TPA/Cu2+ system conforms to the Marcus-type electron transfer. Furthermore, the high reorganization obtained from these Studies is consistent with significant bond cleavage in the transition state, and a mechanism consistent with the experimental data is proposed.