Spectroelectrochemical Examination of Charge Transfer between Chlorpromazine Cation Radical and Catecholamines

Article abstract of DOI:10.1021/ac00253a029

With chlorpromazine (CPZ) and dopamine (DA) in their reduced forms in solution, the potential of a platinum electrode was stepped to a value where both species were oxidized at diffusion controlled rates.The CPZ⁺. cation radical so generated then diffused away from the electrode and encountered reduced DA, which it oxidized.The rate of oxidation was determined by monitoring the absorbance due to CPZ⁺. or dopamine quinone (DPQ) using the glancing incidence reflection spectroelectrochemical technique.The kinetics of the process indicate that the rate law is first order in both CPZ⁺. and DA, implying that the first encouter of the two molecules is the rate limiting step, rather than some subsequent process.The rate constant for dopamine was compared with those for three other catechols, and the rate constant increased monotonically with driving force, as measured by the difference in redox potentials between catechol and CPZ.The advantages of the technique for studying homogeneous charge transfer reactions are noted, as is the implication of the results on the CPZ⁺./DA reaction on the biological effects of CPZ.