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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Reaction mechanism for the highly efficient catalytic decomposition of peroxynitrite by the amphipolar iron(III) corrole 1-Fe
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Reaction mechanism for the highly efficient catalytic decomposition of peroxynitrite by the amphipolar iron(III) corrole 1-Fe

机译：两极铁（III）腐蚀剂1-Fe高效催化分解过氧亚硝酸盐的反应机理

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摘要

The amphipolar iron(III) corrole 1-Fe is one of the most efficient catalysts for the decomposition of peroxynitrite, the toxin involved in numerous diseases. This research focused on the mechanism of that reaction at physiological pH, where peroxynitrite is in equilibrium with its much more reactive conjugated acid, by focusing on the elementary steps involved in the catalytic cycle. Kinetic investigations uncovered the formation of a reaction intermediate in a process that is complete within a few milliseconds (k(1) similar to 3 x 10(7) M-1 s(-1) at 5 degrees C, about 7 orders of magnitude larger than the first order rate constant for the non-catalyzed process). Multiple evidence points towards iron-catalyzed homolytic O-O bond cleavage to form nitrogen dioxide and hydroxo-or oxo-iron(IV) corrole. The iron(IV) intermediate was found to decay via multiple pathways that proceed at similar rates (k(2) about 10(6) M-1 s(-1)): reaction with nitrogen dioxide to form nitrate, nitration of the corrole macrocyclic, and dimerization to binuclear iron(IV) corrole. Catalysis in the presence of substrates affects the decay of the iron intermediate by either oxidative nitration (phenolic substrates) or reduction (ascorbate). A large enough excess of ascorbate accelerates the catalytic decomposition of PN by 1-Fe by orders of magnitude, prevents other decay routes of the iron intermediate, and eliminates nitration products as well. This suggests that the beneficial effect of the iron corrole under the reducing conditions present in most biological media might be even larger than in the purely chemical system. The acquired mechanistic insight is of prime importance for the design of optimally acting catalysts for the fast and safe decomposition of reactive oxygen and nitrogen species.
机译：两极铁（III）腐蚀剂1-Fe是最有效的分解过氧亚硝酸盐的催化剂之一，过氧亚硝酸盐是涉及多种疾病的毒素。这项研究的重点是在生理pH值下的反应机理，其中过氧亚硝酸盐与其反应性更高的共轭酸处于平衡状态，着眼于催化循环中涉及的基本步骤。动力学研究揭示了在几毫秒内完成的过程中反应中间体的形成（k（1）类似于在5摄氏度，约7个数量级的3 x 10（7）M-1 s（-1）大于非催化过程的一级速率常数）。多种证据表明，铁催化的均相O-O键裂解形成二氧化氮和羟基铁或氧铁（IV）腐蚀物。发现铁（IV）中间体通过以相似速率（k（2）约10（6）M-1 s（-1））进行的多条途径降解：与二氧化氮反应形成硝酸盐，硝化了甲氧大环，并二聚为双核铁（IV）腐蚀物。在底物存在下的催化作用通过氧化硝化（酚类底物）或还原（抗坏血酸盐）影响铁中间体的降解。足够大量的抗坏血酸可以使1-Fe催化PN催化PN分解数量级，防止铁中间体的其他衰变途径，并消除硝化产物。这表明在大多数生物介质中存在的还原条件下，铁腐蚀物的有益作用可能甚至大于纯化学体系中的作用。获得的机理见解对于设计用于快速安全地分解活性氧和氮物种的最佳作用催化剂至关重要。

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