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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Six-coordinate ferric porphyrins containing bidentate N-t-butyl-N-nitrosohydroxylaminato ligands: structure, magnetism, IR spectroelectrochemisty, and reactivity
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Six-coordinate ferric porphyrins containing bidentate N-t-butyl-N-nitrosohydroxylaminato ligands: structure, magnetism, IR spectroelectrochemisty, and reactivity

机译：含有双齿N-叔丁基-N-亚硝基羟基laminato配体的六配位铁卟啉：结构，磁性，IR光谱电化学和反应性

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NONOates (diazeniumdiolates) containing the [X{N2O2}](-) functional group are frequently employed as nitric oxide (NO) donors in biology, and some NONOates have been shown to bind to metalloenzymes. We report the preparation, crystal structures, detailed magnetic behavior, redox properties, and reactivities of the first isolable alkyl C-NONOate complexes of heme models, namely (OEP)Fe(eta(2)-ON(t-Bu)NO) (1) and (TPP)Fe(eta(2)-ON(t-Bu)NO) (2) (OEP = octaethylporphyrinato dianion, TPP = tetraphenylporphyrinato dianion). The compounds display the unusual NONOate O,O-bidentate binding mode for porphyrins, resulting in significant apical Fe displacements (+0.60 angstrom for 1 and +0.69 angstrom for 2) towards the axial ligands. Magnetic susceptibility and magnetization measurements made from 1.8-300 K at magnetic fields from 0.02 to 5 T, yielded magnetic moments of 5.976 and 5.974 Bohr magnetons for 1 and 2, respectively, clearly identifying them as high-spin (S = 5/2) ferric compounds. Variable-frequency (9.4 GHz and 34.5 GHz) EPR measurements, coupled with computer simulations, confirmed the magnetization results and yielded more precise values for the spin Hamiltonian parameters: g(avg) = 2.00 +/- 0.03, vertical bar D vertical bar = 3.89 +/- 0.09 cm(-1), and E/D = 0.07 +/- 0.01 for both compounds, where D and E are the axial and rhombic zero-field splittings. IR spectroelectrochemistry studies reveal that the first oxidations of these compounds occur at the porphyrin macrocycles and not at the Fe-NONOate moieties. Reactions of 1 and 2 with a histidine mimic (1-methylimidazole) generate RNO and NO, both of which may bind to the metal center if sterics allow, as shown by a comparative study with the Cupferron complex (T(p-OMe) PP)Fe(eta(2)-ON(Ph)NO). Protonation of 1 and 2 yields N2O as a gaseous product, presumably from the initial generation of HNO that dimerizes to the observed N2O product.
机译：含有[X {N2O2}]（-）官能团的NONOates（二氮杂二烯二醇盐）在生物学中经常被用作一氧化氮（NO）供体，并且一些NONOates已显示与金属酶结合。我们报告了血红素模型的第一个可分离的烷基C-NONOate配合物（即（OEP）Fe（eta（2）-ON（t-Bu）NO））的制备，晶体结构，详细的磁性行为，氧化还原特性和反应性。 1）和（TPP）Fe（eta（2）-ON（t-Bu）NO）（2）（OEP =八乙基卟啉对二阴离子，TPP =四苯基卟啉对二阴离子）。这些化合物对卟啉显示出不同寻常的NONOate O，O-双齿结合模式，导致朝向轴向配体的明显的铁尖顶位移（1 +0.60埃和2 +0.69埃）。在0.02至5 T的磁场下，从1.8-300 K进行磁化率和磁化强度测量，分别得出1和2的磁矩分别为5.976和5.974 Bohr磁子，清楚地将它们标识为高自旋（S = 5/2）铁化合物。可变频率（9.4 GHz和34.5 GHz）EPR测量与计算机模拟相结合，确认了磁化结果，并为自旋哈密顿量参数得出了更精确的值：g（avg）= 2.00 +/- 0.03，垂直条D垂直条=两种化合物的3.89 +/- 0.09 cm（-1）和E / D = 0.07 +/- 0.01，其中D和E是轴向和菱形零场分裂。红外光谱电化学研究表明，这些化合物的首次氧化发生在卟啉大环上，而不发生在Fe-NONOate部分上。 1和2与组氨酸模拟物（1-甲基咪唑）的反应生成RNO和NO，如果空间允许，两者都可能结合到金属中心，如Cupferron配合物（T（p-OMe）PP的比较研究）所示Fe（eta（2）-ON（Ph）NO）。 1和2的质子化可产生N2O，为气态产物，大概是从最初生成的HNO生成二聚为观察到的N2O产物。

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