Study The Electron Transfer Mechanism Of Small Molecule Quinone Compounds By IR Spectroelectrochemistry Cyclic Voltabsorptometry And Derivative Cyclic Voltabsorptometry Technique

In this paper, the achievements of electrochemical studies of quinone compounds were reviewed. The carbonyl group(C=O) in the structure of the quinone compound is the active center of the oxidation-reduction reaction, Most of quinone compounds with good electrochemical activity, is an excellent carrier for the electron transfer, and play an important role in redox electron transport chains of living systems. Study the electrochemical reaction mechanism of quinone compounds, which can make a better understanding of the metabolic processes in the living systems. The electron transfer mechanism of a representative quinones was investigated by Cyclic voltammetry (CV), In-situ IR spectrum, IR spectroelectrochemistry cyclic voltabsorptometry (CVA) and derivative cyclic voltabsorptometry (DCVA) technique. This paper mainly covered the following research works:1. Electrochemical and In-situ FTIR Spectroelectrochemistry techniques were used to study the electrochemical reaction of anthraquinone (AQ) and1,8-dimethoxy-9,10-anthraquinone (DMeAQ), In-situ FTIR Spectroelectrochemistry techniques was used to track the whole electrochemical redox process of the AQ and DMeAQ. The appearance and disappearance of intermediate semiquinone anion radical were clearly observed in the3D spectra and CVA. The information form the different peaks was studied by CVA and DCVA, The result proved the electrochemical eduction reaction mechanism of AQ and DMeAQ, the mechanism is that:(1) The reduction of AQ: AQ＋e＝AQ·-AQ·-e=AQ2-2AQ·-=AQ＋AQ2- (2) The reduction of DMeAQ: DMeAQ+e=DMeAQ·-DMeAQ·-+e=DMeAQ2-2DMeAQ·-=DMeAQ+DMeAQ2-2. The electrochemical characters of1,8-dihydroxy-9,10-anthraquinone (Q) was studied by cyclic voltammetry in the thin layer cell. In-situ FT2IR was employed as a powerful tool in exploring the changes in the molecular structure of the electrochemical reaction process from the molecular level, and the reaction mechanism of forming dimer during the reaction was proposed. Compared with AQ and DMeAQ, The electrochemical process of Q is not a simple two-step single-electron oxidation-reduction reaction, suggesting that the electrochemical oxidation process may be a complex reaction including some other complicated chemical processes, such as:the formation of semiquinone radical and dianion, the emiquinone radical protonation and dimerization reaction occurs via hydrogen bonds, and so on. So the Q electrochemical reaction mechanism was proposed by CVA and DCVA. 3. The Q was electrolyzed in the homemade electrolytic cell by controlling the current and the potentiometer, the dimer crystal appeared on the surface of electrode, the Mass Spectrometry (MS), infrared spectroscopy (IR), and nuclear magnetic resonance spectroscopy (’H-NMR and13C-NMR) were used to characterize the dimer, the results confirmed that the proposed reaction mechanism of the Q is correct. The mechanism is that:4. Electrochemical and In-situ FTIR Spectroelectrochemistry techniques were used to study the electrochemical reaction of chrysophanol (EQ) in the thin-layer cell, and study the reaction affected by CH3OH. These processes were tracked by In-situ FTIR Spectroelectrochemistry techniques. The result shows that the electrochemical reacton of EQ is similar to that of AQ and DmeAQ, and different from that Q. The reason may be caused by the steric hindrance effect of methyl.