The observation of ion-pairing effect based on substituent effect of ferrocene derivatives

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• 作者：Yujie Shi ; Liu Fang ; Xuan Li ; Liangti Qu ; Huibo Shao ; ^{hbs@bit.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Ferrocene derivatives ; Substituent effect ; Ion-pairing effect ; Positive/negative cooperativity ; Reversal phenomenon
• 刊名：Journal of Electroanalytical Chemistry
• 出版年：2015
• 出版时间：15 November 2015
• 年：2015
• 卷：757
• 期：Complete
• 页码：258-262
• 全文大小：1595 K

文摘

The ion-pairing effect was investigated based on the substituent effect of ferrocene (Fc) derivatives using cyclic voltammetry. It was shown that the presence of ion-pairing strongly affected the electrochemical redox behavior in the organic solvent. The formal redox potential (E^0′, the average of anodic and cathodic peak potential) shifted negatively with the increasing ion-pairing effect. That was because the formation of ion pair (Fc⁺·ClO₄⁻) was beneficial to equilibrium shift from Fc to Fc⁺ in thermodynamics. In this work, electron-donating and electron-withdrawing substituents of ferrocene derivatives were employed for a deep study of ion-pairing effect, respectively. It is confirmed that both ion-pairing effect and electron-donating substituent effect facilitated the negative shift of E^0′ for ferrocene derivatives, showing the positive cooperativity. While the electron-withdrawing substituent effect resulted in the positive shift of E^0′ for ferrocene derivatives and was unfavorable for the oxidation of Fc derivatives, reflecting the negative cooperativity with ion-pairing effect. In addition, the reversal phenomenon of weak electron-withdrawing substituent was revealed when the ion-pairing effect was stronger than the electron-withdrawing substituent effect, indicating that the ion-pairing function has a significant effect on electrochemical behavior of ferrocene derivatives.