一个热力学模型,用于在位点差异化的高旋转铁集群中对一氧化碳的氧依赖结合
Charles H Arnett1, Matthew J Chalkley1, Theodor Agapie1
1Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , United States.
Journal of the American Chemical Society
|March 29, 2018
概括
反氧化化学对高旋转铁集团对二氧化碳的亲和力影响极小,而低旋转复合物则不同. 电子转移促进了Fe(III) 位点的CO结合,这表明了酶辅因子结合的机制.
科学领域:
- 生物有机化学
- 有机金属化学
- 生物化学
背景情况:
- 酶的FeMo辅因子会因其氧化还原状态而结合N2和CO.
- 了解氧化还原变化如何影响高旋铁对π酸的亲和力至关重要,但尚未得到充分阐明.
研究的目的:
- 研究氧化还原化学对一氧化碳 (CO) 的结合亲和力和激活作用.
- 将高旋转铁集群中的氧化还原效应与低旋转和单金属铁复合体中的氧化还原效应进行比较.
主要方法:
- 能够进行可逆CO结合的位点分化的铁集群的合成.
- 电化学研究探测从Fe (II) 4到Fe (II) Fe (III) 3的氧化还原状态.
- 用光谱分析 (例如 νCO 频率) 来评估 CO 的结合和激活.
主要成果:
- 一个电子氧化还原事件导致高旋铁集群的CO亲和力和激活的轻微变化 (高达400倍).
- 相比之下,低旋转和单金属铁复合物由于结合点的氧化还原化学反应而显示出很大的亲和力增强 (10^5-10^22倍).
- 远程金属中心的电子负载对CO结合能量影响最小 (约1kcal·mol-1),但通过内部电子转移使CO结合成为可能.
结论:
- 反氧化化学对高旋转铁集群的碳化合物结合亲和力有有限的直接影响.
- 集群内部的远程电子转移促进了在Fe (III) 中心的CO结合,并带来了很小的能量损失.
- 这些发现表明FeMo辅因子的N2和CO协调机制,可能涉及辅因子的氧化边缘.
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