Spectroscopic Observation of the Dimerization Reactions of the 9-Phenylcarbazole Cation Radical in Acetonitrile

摘要

The dimerization reaction processes of the 9-phenylcarbazole cation radical(PCZ~(center dot+))in acetonitrile(AN)were observed using an electron-transfer stopped-flow method.Although the lifetime of PCZ~(center dot+)in AN is less than a few hundred milliseconds,the dynamic transformation of the absorption spectra of PCZ~(center dot+)was successfully observed in AN for the first time with the proposed method.By observing the changes in the absorption spectra in the visible region,the decrease in PCZ~(center dot+)and the concurrent increase in the dimer cation radical were observed with isosbestic points.In addition,in the presence of neutral PCZ,the acceleration of the dimerization of PCZ~(center dot+)was clearly confirmed.Consequently,in the presence of PCZ,the rate law was determined to be-d[PCZ~(center dot+)]/dt = 3Kk'[PCZ~(center dot+)]~2[PCZ],where 3Kk' is 1.4X10~9 M~(-2)s~(-1).This means that the reaction mechanism involves a two-step interaction with the catalytic effect of neutral PCZ.Although the difference in the reactivity had already been known between PCZ~(center dot+)and the triphenylamine cation radical,the reaction mechanism has been clarified to be different in both cases.