IR Spectroelectrochemical Cyclic Voltabsorptometry and Derivative Cyclic Voltabsorptometry

Abstract

In this paper, we report the IR (infrared) CVA (cyclic voltabsorptometry) and DCVA (derivative cyclic voltabsorptometry) spectroelectrochemical techniques to elucidate an electrochemical mechanism. First we set potassium ferrocyanide as an example to explain the validity of this method. Then the electrochemical redox of two compounds, 1,4-benzoquinone and 1,4-bis(2-ferrocenylvinyl)benzene, was selected to be examined with this method. 1,4-Benzoquinone exhibits two single-electron waves in the cyclic voltammetric (CV) experiment, whereas two electroactive groups (Fc) are contained in p-(Fc-CH=CH)(2)BZ, but only one redox wave is observed. IR CVA results show that three IR absorption peaks in 1,4-benzoquinone, 1232 cm(-1) (the absorption of final production), 1656 cm(-1) (the absorption of original reactant), and 1510 cm(-1) (the absorption of intermediate), and two IR absorption peaks in 1,4-bis(2-ferrocenylvinyl)benzene, 1620 cm(-1) (the absorption of final oxide production) and 1589 cm(-1) (the absorption of intermediate), can be used to track the electron transfer. On the basis of the IR absorbance at the appropriate monitored wavelength (mentioned above), we can analyze simultaneously the concentration change of the corresponding redox transition during CV scans. Also the combination of the DCVA spectroelectrochemical technique with theory analysis allows reconstructing the current-potential (i-E) curve for each step of electron transfer. The reconstructed i-E curve can help us to understand the electron-transfer process. We believe IR CVA and DCVA spectroelectrochemical techniques can be applicable to the study of a wide range of complex electrochemistry processes.