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首页> 外文期刊>Environmental toxicology and chemistry >ROLE OF METALLOPORPHYRIN CORE METALS IN THE MEDIATED REDUCTIVE DECHLORINATION OF TETRACHLOROETHYLENE
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ROLE OF METALLOPORPHYRIN CORE METALS IN THE MEDIATED REDUCTIVE DECHLORINATION OF TETRACHLOROETHYLENE

机译：金属卟啉核金属在四乙叉基介导的还原脱氯中的作用

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A promising approach to abiotically dechlorinate a variety of chlorinated organic contaminants under reducing conditions is to utilize porphyrins or other tetrapyrrole macrocycles as electron transfer mediators/shuttles for catalyzing their reduction. In this study, various experimental approaches were used to elucidate the role of porphyrin core metals in the reductive dechlorination of tetrachloroethylene (PCE). The importance of specific core metals for the reactivity of a porphyrin and its mediated reaction mechanisms was demonstrated by inserting different metals into metallo tetrakis (N-methyl-4-4 pyridiniumyl) porphyrin (TMPyP). No PCE dechlorination was observed when the free-base (i.e., no core metal) and iron core metal forms of TMPyP were utilized. When using nickel or cobalt TMPyP, reductive dechlorination of PCE occurred but appeared to follow different pathways for the two metals based on product analyses. Physical (e.g., steric) considerations suggest that direct contact between a porphyrin core metal and PCE may be limited and therefore that the entire metalloporphyrin molecule should be viewed as a functional system in which the organic macrocycle has an active part in reductive dechlorination reactions. This view is supported by the fact that slight changes in the functional groups on a porphyrin macrocycle, particularly those far removed from the core metal itself, greatly affected the reactivity and mechanism of the porphyrin. Solution conditions also had a major effect on porphyrin reactivities, to the extent that a nonreactive metalloporphyrin could be activated merely by adjusting the pH of the solution or by adding a small amount of cosolvent. The collective results of this study suggest that fine tuning of naturally occurring metalloporphyrin complexes and/or their environments can enhance the catalyzed detoxification of chlorinated contaminants in many natural and engineered environmental systems.
机译：在还原条件下对多种氯化有机污染物进行非生物脱氯的一种有前途的方法是利用卟啉或其他四吡咯大环化合物作为电子转移介质/航天飞机，以催化其还原。在这项研究中，使用各种实验方法来阐明卟啉核心金属在四氯乙烯（PCE）还原脱氯中的作用。通过将不同的金属插入金属四（N-甲基-4-4吡啶鎓）卟啉（TMPyP）中，可以证明特定核心金属对于卟啉反应性及其介导的反应机理的重要性。当使用TMPyP的游离碱（即无芯金属）和铁芯金属形式时，未观察到PCE脱氯。当使用镍或钴TMPyP时，PCE发生了还原性脱氯，但根据产物分析，两种金属似乎遵循不同的途径。物理（例如空间）方面的考虑表明，卟啉核心金属与PCE之间的直接接触可能受到限制，因此整个金属卟啉分子应被视为功能体系，其中有机大环化合物在还原性脱氯反应中具有活性。卟啉大环上官能团的微小变化，特别是那些远离核心金属本身的官能团的轻微变化，极大地影响了卟啉的反应性和机理，这一观点得到了支持。溶液条件对卟啉反应性也有重大影响，以致仅通过调节溶液的pH值或加入少量助溶剂就可以活化非反应性金属卟啉。这项研究的总体结果表明，在许多自然环境和工程环境系统中，对天然存在的金属卟啉配合物和/或其环境进行微调可以增强对氯化污染物的催化解毒作用。

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