Electrocatalytic redox of hydroquinone by two forms of l-Proline

The redox behavior, the molecular mechanism and electronic transfer of hydroquinone interacted with two forms of l-Proline, covalent-linked to glass carbon electrode surface through CN bond by electrooxidation and free dissolved in solution, were investigated by means of UV–vis and electrochemistry. The UV–vis spectrum showed that the reaction between free l-Proline and hydroquinone did not involve strong chemical bond. However, the electrochemical behavior of covalent-linked l-Proline is different from that of free one. Owing to electrostatic effect, the form of covalent-linked l-Proline favors electron transfer and enhances the reversibility of redox for hydroquinone. This phenomenon is conformed by cyclic voltammogram with a significant increase in peak current of hydroquinone redox and rate constant of electron transfer. It was found that it is a three-electron-transfer reaction. On the contrary, the form of free l-Proline unfavors electron transfer, resulting in a decrease in peak current of hydroquinone and rate constant, and the hydrogen bond was formed in the interaction.

The molecular mechanism and electronic transfer of hydroquinone redox by two forms of l-Proline, covalent-linked to glass carbon electrode surface and free dissolved in solution, were investigated. Owing to electrostatic effect, l-Proline covalent-linked favors electron transfer and enhances the reversibility of hydroquinone redox. This phenomenon is reflected by a significant increase in peak current of hydroquinone redox and rate constant of electron transfer in voltammetry. Furthermore, it is a three-electron-transfer mechanism. On the contrary, free dissolved l-Proline impedes electron transfer, resulting in a decrease in peak current of hydroquinone and rate constant. Besides, due to hydrogen bond formed, with increasing l-Proline concentration, the association formed between l-Proline and hydroquinone will turn from l-Proline·C6H6O2 to (l-Proline)2·C6H6O2. The investigation will be useful to explore new biocatalytic strategies.Figure optionsDownload as PowerPoint slide