在水溶液中，铁（III）四（5,10,15,20-（N-甲基-4-吡啶基））卟啉与过氧化氢反应过程中，氧代铁（IV）卟啉自由基阳离子的瞬态形成。

Transient formation of the oxo-iron(IV) porphyrin radical cation during the reaction of iron(III) tetrakis-5,10,15,20-(N-methyl-4-pyridyl)porphyrin with hydrogen peroxide in aqueous solution.

作者信息

Saha Tapan Kumar, Karmaker Subarna, Tamagake Keietsu

机构信息

Faculty of Pharmaceutical Science, Okayama University, 1-1-1 Tsushima-naka, Okayama 700-8530, Japan.

出版信息

Luminescence. 2003 May-Jun;18(3):162-72. doi: 10.1002/bio.718.

DOI:10.1002/bio.718

PMID:12701092

Abstract

The reaction of iron(III) tetrakis-5,10,15,20-(N-methyl-4-pyridyl)porphyrin (Fe(III)TMPyP) with hydrogen peroxide (H(2)O(2)) and the catalytic activity of the reaction intermediates on the luminescent peroxidation of luminol in aqueous solution were studied by using a double-mixing stopped-flow system. The observed luminescence intensities showed biphasic decay depending on the conditions. The initial flashlight decayed within <1 s followed by a sustained emission for more than 30 s. Computer deconvolution of the time-resolved absorption spectra under the same conditions revealed that the initial flashlight appeared during the formation of the oxo-iron(IV) porphyrin, TMPyPFe(IV) = O, which is responsible for the sustained emission. The absorption spectra 0.0-0.5 s did not reproduce well by a simple combination of the two spectra of Fe(III)TMPyP and TMPyPFe(IV) = O, indicating that transient species was formed at the initial stage. Addition of uric acid (UA) caused a significant delay in the initiation of the luminol emission as well as in the formation of the TMPyPFe(IV) = O. Both of them were completely diminished in the presence of UA equimolar with H(2)O(2), while mannitol had no effect at all. The delay of the light emission as well as the appearance of TMPyPFe(IV) = O was directly proportional to the UA but other kinetic profiles were not changed significantly. Based on these observations and the kinetic analysis, we confirmed the involvement of the oxo-iron(IV) porphyrin radical cation, (TMPyP)(.+)Fe(IV) = O, as an obligatory intermediate in the rate-determining step of the overall reaction, Fe(III)TMPyP + H(2)O(2) --> TMPyPFe(IV) = O, with a rate constant of k = 4.3 x 10(4)/mol/L/s. The rate constants for the reaction between the (TMPyP)(.+)Fe(IV) = O and luminol, and between the TMPyPFe(IV) = O and luminol were estimated to be 3.6 x 10(6)/mol/L/s and 1.31 x 10(4)/mol/L/s, respectively.

摘要

采用双混合停流系统研究了四（5,10,15,20-（N-甲基-4-吡啶基））卟啉铁（III）（Fe(III)TMPyP）与过氧化氢（H₂O₂）的反应以及反应中间体对鲁米诺在水溶液中发光过氧化反应的催化活性。观察到的发光强度根据条件呈现双相衰减。初始闪光在<1秒内衰减，随后持续发射超过30秒。在相同条件下对时间分辨吸收光谱进行计算机去卷积分析表明，初始闪光出现在氧合铁（IV）卟啉TMPyPFe(IV)=O形成过程中，该氧合铁（IV）卟啉负责持续发射。0.0 - 0.5秒的吸收光谱不能通过简单组合Fe(III)TMPyP和TMPyPFe(IV)=O的两个光谱很好地重现，这表明在初始阶段形成了瞬态物种。添加尿酸（UA）导致鲁米诺发射的起始以及TMPyPFe(IV)=O的形成出现显著延迟。在与H₂O₂等摩尔的UA存在下，这两者都完全消失，而甘露醇则完全没有影响。发光延迟以及TMPyPFe(IV)=O的出现与UA成正比，但其他动力学曲线没有明显变化。基于这些观察结果和动力学分析，我们证实氧合铁（IV）卟啉自由基阳离子（TMPyP）⁺Fe(IV)=O作为总反应Fe(III)TMPyP + H₂O₂→TMPyPFe(IV)=O速率决定步骤中的必需中间体，其速率常数k = 4.3×10⁴/mol/L/s。（TMPyP）⁺Fe(IV)=O与鲁米诺反应以及TMPyPFe(IV)=O与鲁米诺反应的速率常数分别估计为3.6×10⁶/mol/L/s和1.31×10⁴/mol/L/s。