Rapid-scan time-resolved FT-IR spectroelectrochemistry studies on the electrochemical redox process.
The electron transfer to or from molecules containing multiple redox centers has been extensively investigated. Rapid scan time-resolved FT-IR-RAS spectroelectrochemistry was used to investigate the electron-transfer mechanism in this report. The electron transfer of two typical compounds, 1,4-benzoquinone and 1,4-bis(2-ferrocenylvinyl)benzene, was examined with this method. Although the two compounds show two-electron transfer in the redox process, 1,4-benzoquinone exhibits two single electron waves while 1,4-bis(2-ferrocenylvinyl)benzene exhibits a single wave in cyclic voltammetric experiments. The IR absorption of the intermediate, BQ*- and p-(Fc-CH=CH)+2-benzene, at 1506 and 1589 cm(-1), respectively, appeared and disappeared on the experimental time scale in the oxidation and reduction process was observed. In the oxidation process of the p-(Fc-CH=CH)2-benzene molecule, one Fc was oxidated to Fc+ first and the electron-withdrawing ability of Fc+ was stronger than that of Fc, which resulted in the D-pi-A structure and the band at 1589 cm(-1) becoming visible. Then as the oxidation continues, the other Fc was oxidated to Fc+ too, which resulted in the reforming of the symmetry of the benzene ring A-pi-A, so the band at 1589 cm(-1) disappeared. Similar phenomenon can be elucidated in the reduction process but the configuration type changed from A-pi-A to D-pi-A and finally to D-pi-D. Hence, not only 1,4-benzoquinone but also 1,4-bis(2-ferrocenylvinyl)benzene show two consecutive one-electron processes. In addition, it is observed that the existing time of the electrochemical reaction intermediate (BQ*- and p-(Fc-CH=CH)+2-benzene) is prolonged at low temperatures due to slow reaction kinetics.
Jin
Baokang
B
Department of Chemistry, Anhui University, 230039, Hefei, Anhui province, P.R. China. bkjinhf@yahoo.com.cn
Liu
Peng
P
Wang
Ye
Y
Zhang
Zipin
Z
Tian
Yupeng
Y
Yang
Jiaxiang
J
Zhang
Shengyi
S
Cheng
Faliang
F
D016227:Benzoquinones / Q000737:chemistry*; D004563:Electrochemistry; D004579:Electron Transport; D005296:Ferrous Compounds / Q000737:chemistry*; D000075163:Metallocenes; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D017550:Spectroscopy, Fourier Transform Infrared; D020058:Styrene / Q000737:chemistry*; D013997:Time Factors
D016227:Benzoquinones; D005296:Ferrous Compounds; D000075163:Metallocenes; D009942:Organometallic Compounds; C004532:quinone; D020058:Styrene; C004998:ferrocene