Electrooxidation of 5-substituted indoles
Electrooxidation of 5-substituted indoles
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DOI：
10.1039/a703128i
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发表时间：
1997-11-07
期刊：
影响因子：
--
通讯作者：
Thomson, AD
中科院分区：
文献类型：
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作者：
Jennings, P;Jones, AC;Thomson, AD
多种 5-取代吲哚单体在铂电极上的电化学氧化导致氧化还原活性 he 的形成。电化学和光谱证据与 he 中的氧化还原物质是环状三聚体一致。相反，5-氨基吲哚和5-羟基吲哚在铂电极上的电聚合不会导致氧化还原活性膜的形成。这是由于单体通过取代基吸附到金属电极上，从而抑制了该反应。然而，这些单体电聚合到预沉积的 5-氰基吲哚或 5-硝基吲哚上导致形成环状三聚体。使用旋转环盘电极（RRDE）进行的电化学研究已经证实了三聚反应的化学计量，并且氧化还原活性环状三聚体物质表现出可逆的单电子氧化还原活性。这些三聚体中每一个的还原半波电势显示出与哈米特取代基常数 sigma(+) 或 sigma(-) 的线性相关性，视情况而定，针对对位取代的芳族化合物确定，表明 5-取代基共轭到三聚体的π电子系统中。这表明明智地选择取代基可以控制三聚体氧化还原电位。
The electrochemical oxidation of a wide variety of 5-substituted indole monomers at a platinum electrode results in the formation of a redox active him. Electrochemical and spectroscopic evidence is consistent with the redox species in the him being a cyclic trimer. In contrast, the electropolymerisation of 5-aminoindole and 5-hydroxyindole on a platinum electrode does not result in redox active film formation. This is attributed to the adsorption of the monomer onto the metal electrode via the substituent, which inhibits this reaction. However, electropolymerisation of these monomers onto a predeposited him of 5-cyanoindole or 5-nitroindole results in the formation of the cyclic trimer. Electrochemical studies using a rotating-ring disc electrode (RRDE) have confirmed the stoichiometry of the trimerisation reaction and also that the redox active cyclic trimer species shows reversible one electron redox activity. The half-wave potential for the reduction of each of these trimers shows a linear dependence with the Hammett substituent constant, sigma(+) or sigma(-), as appropriate, determined for a para-substituted aromatic indicating that the 5-substituent is conjugated into the pi-electron system of the trimer. This indicates that judicious choice of substituents allows control of the trimer redox potential.