Enthalpy–Entropy Compensation Effect in Oxidation Reactions by Manganese(IV)-Oxo Porphyrins and Nonheme Iron(IV)-Oxo Models,Journal of the American Chemical Society

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Enthalpy–Entropy Compensation Effect in Oxidation Reactions by Manganese(IV)-Oxo Porphyrins and Nonheme Iron(IV)-Oxo Models
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2021-11-01 , DOI: 10.1021/jacs.1c08198
Mian Guo _{1,

2} , Jisheng Zhang ₁ , Lina Zhang ₁ , Yong-Min Lee ₁ , Shunichi Fukuzumi _{1,

3} , Wonwoo Nam _{1,

4}

Affiliation

“Enthalpy–Entropy Compensation Effect” (EECE) is ubiquitous in chemical reactions; however, such an EECE has been rarely explored in biomimetic oxidation reactions. In this study, six manganese(IV)-oxo complexes bearing electron-rich and -deficient porphyrins are synthesized and investigated in various oxidation reactions, such as hydrogen atom transfer (HAT), oxygen atom transfer (OAT), and electron-transfer (ET) reactions. First, all of the six Mn(IV)-oxo porphyrins are highly reactive in the HAT, OAT, and ET reactions. Interestingly, we have observed a reversed reactivity in the HAT and OAT reactions by the electron-rich and -deficient Mn(IV)-oxo porphyrins, depending on reaction temperatures, but not in the ET reactions; the electron-rich Mn(IV)-oxo porphyrins are more reactive than the electron-deficient Mn(IV)-oxo porphyrins at high temperature (e.g., 0 °C), whereas at low temperature (e.g., −60 °C), the electron-deficient Mn(IV)-oxo porphyrins are more reactive than the electron-rich Mn(IV)-oxo porphyrins. Such a reversed reactivity between the electron-rich and -deficient Mn(IV)-oxo porphyrins depending on reaction temperatures is rationalized with EECE; that is, the lower is the activation enthalpy, the more negative is the activation entropy, and vice versa. Interestingly, a unified linear correlation between the activation enthalpies and the activation entropies is observed in the HAT and OAT reactions of the Mn(IV)-oxo porphyrins. Moreover, from the previously reported HAT reactions of nonheme Fe(IV)-oxo complexes, a linear correlation between the activation enthalpies and the activation entropies is also observed. To the best of our knowledge, we report the first detailed mechanistic study of EECE in the oxidation reactions by synthetic high-valent metal-oxo complexes.

中文翻译：

锰（IV）-氧代卟啉和非血红素铁（IV）-氧代模型在氧化反应中的焓-熵补偿效应

“焓-熵补偿效应”（EECE）在化学反应中无处不在；然而，在仿生氧化反应中很少探索这种EECE。本研究合成了六种带有富电子和缺电子卟啉的锰 (IV)-氧代配合物，并在氢原子转移 (HAT)、氧原子转移 (OAT) 和电子转移等各种氧化反应中进行了研究。 ET) 反应。首先，所有六种 Mn(IV)-氧代卟啉在 HAT、OAT 和 ET 反应中都具有高反应性。有趣的是，我们观察到富含电子和缺乏 Mn(IV)-氧代卟啉在 HAT 和 OAT 反应中的反向反应性，这取决于反应温度，但在 ET 反应中没有；富电子的 Mn(IV)-氧代卟啉在高温（例如，0 °C）下比缺电子的 Mn(IV)-氧代卟啉更具反应性，而在低温（例如，-60 °C）下，缺电子的 Mn(IV)-氧卟啉比富电子的 Mn(IV)-氧卟啉更具反应性。EECE 使富电子和缺电子 Mn(IV)-氧代卟啉之间这种依赖于反应温度的反向反应性合理化；即激活焓越低，激活熵越负，反之亦然。有趣的是，在 Mn(IV)-氧卟啉的 HAT 和 OAT 反应中观察到活化焓和活化熵之间的统一线性相关性。此外，从先前报道的非血红素 Fe(IV)-oxo 配合物的 HAT 反应中，还观察到激活焓和激活熵之间的线性相关性。据我们所知，我们报告了 EECE 在合成高价金属-氧代络合物氧化反应中的首次详细机理研究。

更新日期：2021-11-10

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