McQuilken Alison C, Matsumura Hirotoshi, Dürr Maximilian, Confer Alex M, Sheckelton John P, Siegler Maxime A, McQueen Tyrel M, Ivanović-Burmazović Ivana, Moënne-Loccoz Pierre, Goldberg David P
Department of Chemistry, The Johns Hopkins University , Baltimore, Maryland 21218, United States.
Oregon Health & Science University, Institute of Environmental Health, Portland, Oregon 97239, United States.
J Am Chem Soc. 2016 Mar 9;138(9):3107-17. doi: 10.1021/jacs.5b12741. Epub 2016 Feb 26.
The nonheme iron complex, [Fe(NO)(N3PyS)]BF4, is a rare example of an {FeNO}(7) species that exhibits spin-crossover behavior. The comparison of X-ray crystallographic studies at low and high temperatures and variable-temperature magnetic susceptibility measurements show that a low-spin S = 1/2 ground state is populated at 0-150 K, while both low-spin S = 1/2 and high-spin S = 3/2 states are populated at T > 150 K. These results explain the observation of two N-O vibrational modes at 1737 and 1649 cm(-1) in CD3CN for [Fe(NO)(N3PyS)]BF4 at room temperature. This {FeNO}(7) complex reacts with dioxygen upon photoirradiation with visible light in acetonitrile to generate a thiolate-ligated, nonheme iron(III)-nitro complex, Fe(III)(NO2)(N3PyS), which was characterized by EPR, FTIR, UV-vis, and CSI-MS. Isotope labeling studies, coupled with FTIR and CSI-MS, show that one O atom from O2 is incorporated in the Fe(III)-NO2 product. The O2 reactivity of [Fe(NO)(N3PyS)]BF4 in methanol is dramatically different from CH3CN, leading exclusively to sulfur-based oxidation, as opposed to NO· oxidation. A mechanism is proposed for the NO· oxidation reaction that involves formation of both Fe(III)-superoxo and Fe(III)-peroxynitrite intermediates and takes into account the experimental observations. The stability of the Fe(III)-nitrite complex is limited, and decay of Fe(III)(NO2)(N3PyS) leads to {FeNO}(7) species and sulfur oxygenated products. This work demonstrates that a single mononuclear, thiolate-ligated nonheme {FeNO}(7) complex can exhibit reactivity related to both nitric oxide dioxygenase (NOD) and nitrite reductase (NiR) activity. The presence of the thiolate donor is critical to both pathways, and mechanistic insights into these biologically relevant processes are presented.
非血红素铁配合物[Fe(NO)(N3PyS)]BF4是表现出自旋交叉行为的{FeNO}(7)物种的一个罕见例子。低温和高温下的X射线晶体学研究以及变温磁化率测量结果表明，在0至150 K时占据低自旋S = 1/2基态，而在T > 150 K时低自旋S = 1/2和高自旋S = 3/2态均被占据。这些结果解释了室温下在CD3CN中[Fe(NO)(N3PyS)]BF4在1737和1649 cm(-1)处观察到的两种N - O振动模式。这种{FeNO}(7)配合物在乙腈中用可见光光照射时与双氧反应生成硫醇盐配位的非血红素铁(III)-硝基配合物Fe(III)(NO2)(N3PyS)，通过电子顺磁共振（EPR）、傅里叶变换红外光谱（FTIR）、紫外可见光谱（UV-vis）和串联质谱（CSI-MS）对其进行了表征。同位素标记研究与FTIR和CSI-MS相结合表明，来自O2的一个O原子掺入到Fe(III)-NO2产物中。[Fe(NO)(N3PyS)]BF4在甲醇中的O2反应性与乙腈显著不同，仅导致基于硫的氧化，而不是NO·氧化。提出了一个涉及Fe(III)-超氧和Fe(III)-过氧亚硝酸根中间体形成的NO·氧化反应机制，并考虑了实验观察结果。Fe(III)-亚硝酸盐配合物的稳定性有限，Fe(III)(NO2)(N3PyS)的分解导致{FeNO}(7)物种和硫氧化产物。这项工作表明，单个单核、硫醇盐配位的非血红素{FeNO}(7)配合物可以表现出与一氧化氮双加氧酶（NOD）和亚硝酸还原酶（NiR）活性相关的反应性。硫醇盐供体的存在对这两条途径都至关重要，并给出了对这些生物学相关过程的机理见解。
